|Root Canal Filling Materials|
|Date: 13/06/2011 22:53|
Root Canal Filling Materials
Root Canal Filling Materials - JAMES DAVID JOHNSON
Historically, many materials have been used to fill root canals. In the 1800s and before, materials ranging from tin foil, lead foil, gold foil, cotton pellets with various medicaments, wood, spunk, plaster of Paris, oxychloride of zinc, oxyphosphate of zinc, zinc oxide, paraffin, copper points, and various other concoctions were used to fill root canals. Sometimes canals were not filled at all, and only a mixture of Hill's stopping was placed over canals.1 With Asa Hill's development of Hill's stopping in 1847, which consisted of bleached gutta-percha and carbonate of lime and quartz, the advent of gutta-percha as a root canal filling material in endodontics began.2 In 1867, G. A. Bowman of St. Louis was credited with using gutta-percha points to obturate root canals.1 The S. S. White Company began to market gutta-percha points to the profession in 1887.3 Gutta-percha, as an obturating material, has survived, and today exists in many forms, and is still the most widely used material to obturate root canals.
Requirements for an Ideal Root Canal Filling Material
Grossman4 modified Brownlee's5 criteria for the ideal root canal filling material and listed the following criteria for an ideal root canal filling material:
1. It should be easily introduced into the root canal.
2. It should seal the canal laterally as well as apically.
3. It should not shrink after being inserted.
4. It should be impervious to moisture.
5. It should be bacteriostatic or at least not encourage bacterial growth.
6. It should be radiopaque.
7. It should not stain tooth structure.
8. It should not irritate periradicular tissues.
9. It should be sterile, or easily and quickly sterilized, immediately before insertion.
10. It should be removed easily from the root canal, if necessary.
Root canal filling materials have been classified as solid-core filling materials, semisolid-core filling materials, and paste filling materials. Silver points are an example of solid-core filling materials. Guttapercha is the most widely used semisolid-core material. Various paste systems have been used over the years, such as zinc oxide-containing pastes.
Solid-Core Filling Materials
HISTORICAL ROOT CANAL FILLING MATERIALS (SILVER POINTS)
Silver points, having the same diameter and taper as files and reamers, were introduced by Jasper in 1933.2 Silver points were widely used in the 1930s to the 1960s, particularly in smaller canals. They were fabricated to the same size as instruments used in the preparation of the canal. Silver points had the advantages of being easy to insert, and length control was easier. Although silver points fulfilled many of Grossman's requirements, the main drawback of silver points is that they do not seal well laterally or apically because of their lack of plasticity. Silver points cannot adequately fill all the canal space and cannot be compacted into spaces or voids within the root canal system. They maintain their round shape and no canal is perfectly round in shape, even after instrumentation. This leaves too much space to be filled by sealer or cement, thus leading to leakage. The leakage allows corrosion of the silver points and the formation of silver salts. These products were found to be cytotoxic. Seltzer et al.6 found such products as silver amine sulfate amide hydrate, silver sulfides, and silver sulfates from silver points removed from canals that were obturated with silver points. Brady and Del Rio7 found corrosion products of sulfur and chlorides by microanalysis of failed silver points. Goldberg8 found that corrosion was present microscopically in cases obturated with silver points that were deemed successful clinically and radiographically. Gutierrez et al.9 reported that canal irrigants could corrode silver points. Kehoe10 reported a case of localized argyria leading to "tattooing" of the alveolar mucosa associated with corroding of a silver point in a maxillary premolar.
Silver points used in smaller canals were very successful in their era. The inappropriate use of silver points in larger canals helped to give rise to their reputation as an inferior obturation method. With the advent of different instrumentation techniques that allowed for successful obturation of smaller canals with gutta-percha, the use of silver points has declined because of their inherent disadvantages. The use of silver points in modern endodontic therapy is extremely limited, and there seems to be no indications or justification for their use today.
Semisolid-Core Filling Materials
Gutta-percha is by far the most popular and commonly used root canal filling material. Although it does not meet all the criteria for an ideal filling material, it satisfies most of them. The major disadvantage of gutta-percha as a root canal filling material is its lack of rigidity. Gutta-percha, particularly the smaller sizes, will bend easily under lateral pressure.
Gutta-percha, known as "mazer wood," was introduced to England from Asia in the 1600s and existed as little more than a curiosity of the East for nearly 200 years.11 It was not until 1848 that Ernst Werner von Siemans used gutta-percha as insulation for underwater cable. With its many desirable properties, gutta-percha soon was being used in many different ways and in many different products. Patents were applied for new products using gutta-percha, which included "corks, cements, thread, surgical instruments, garments, pipes, musical instruments, candelabras, gaiters, garters, suspenders, window shades, carpets, gloves, mattresses, pillows, tents, umbrellas, and sheathing for ships."11 Perhaps the best known use of gutta-percha was in golf balls, introduced in the later part of the nineteenth century and used until 1920. These golf balls were called "gutties."11
Natural gutta-percha has been described as the product of various species of rubber trees from Malaysia, Borneo, Indonesia, and South America, mainly Brazil. Some of the species mentioned as sources of natural gutta-percha are Palaquium gutta, Mimusops globsa, and Manilkara bidentata, and are of the same botanical family as the natural rubber tree Hevea brasiliensis. Raw gutta-percha is the flexible hardened juice of these tropical trees.
Gutta-balata is identical in chemical structure and physical properties to gutta-percha and has long been used as gutta-percha, or added to gutta-percha in commercial brands. Additionally, synthetic trans-polyisoprene may be added to commercial gutta-percha. Raw gutta-percha from the tree undergoes a rigorous process to convert it into commercial grade gutta-percha. This process involves purification, dissolving of resins, and denaturing of proteins.12
Friedman et al.13 investigated the ingredients of five commercial brands of gutta-percha points. They found the composition of these commercially available gutta-percha points, as seen in Table 1, to consist of 18 to 22% gutta-percha, 59 to 76% zinc oxide, 1 to 4% waxes and resins, and 1 to 18% metal sulfates. Although gutta-percha is not the major ingredient, it serves as the matrix. Zinc oxide acts as the filler, whereas the waxes and resins serve as plasticizers. Metal sulfates, such as barium sulfate, provide the radiopacity to identify the material radiographically.
Evidence of slight antibacterial activity from gutta-percha points exists, presumably from the zinc oxide in commercially available gutta-percha14; however, it is too weak to be an effective microbiocide. As the destruction of bacteria is key to endodontic success, a new formulation of gutta-percha that contains iodoform, medicated gutta-percha (MGP) (Medidenta International, Inc., Woodside, NY), has been developed by Martin and Martin.15 Within the filled root canal, the iodine/iodoform depot in the MGP point is a biologically active source for inhibiting microbial growth. The iodoform is centrally located within the gutta-percha and takes about 24 hours to leach to the surface. "The iodoform remains inert until it comes in
[Table 1. Composition of Gutta-Percha Endodontic Filling Materials (Mean Percentage ± SD)]
contact with tissue fluids that activate the free iodine."15 A canal filled with MGP gutta-percha could serve as a protection against bacterial contamination from coronal microleakage reaching the apical tissue. The use of heat during obturation does not affect either the release of iodoform or its chemical composition.16 Presumably, the use of iodine containing gutta-percha points would be contraindicated in a patient with a history of allergy to iodine.
An in vitro assessment of iodoform containing gutta-percha tested the ability of the iodoform containing gutta-percha to delay the infiltration of Enterococcus faecalis using a bacterial microleakage model.17 The results showed no difference between regular gutta-percha points and iodoform-containing gutta-percha points, both with Roth's 801 sealer, in their ability to delay microleakage of E. faecalis.
Gutta-percha points have also been introduced that contain a high percentage of calcium hydroxide (40-60%) (Roeko/Coltene/Whaledent, Langenau, Germany). This permits a simple placement of the medicament within the canal space between appointments. Calcium hydroxide points combine the efficacy of calcium hydroxide in a matrix of 42% bio-inert gutta-percha. Once the calcium hydroxide has leached out, the point is no longer useful as a filling material and must be removed. Holland et al.18 have reported on the use of an experimental calcium hydroxide containing gutta-percha point that can be used for root canal filling. Their results indicate that these points produced an improvement in the apical sealing quality of the root canal filling.
There are also gutta-percha points available that contain chlorhexidine (Activ Point) (Roeko/Coltene/Whaledent) that have a slow release of the chlorhexidine, and are used in a similar manner as the calcium hydroxide-containing gutta-percha. Some studies have shown that the points containing chlorhexidine had a better antibacterial effect than the calcium hydroxide containing gutta-percha points.19
Podbielski et al.20 tested gutta-percha points containing calcium hydroxide and zinc oxide, points containing zinc oxide and chlorhexidine, points containing iodine-polyvinylpyrrolidone, and gutta-percha points containing a mixture of chlorhexidine and iodine-polyvinylpyrrolidone for their ability to inhibit growth of pure cultures of bacterial species commonly involved in endodontic infections. The calcium hydroxide-containing gutta-percha points proved to possess the strongest antibacterial activity, compared with the other three of the four types, for all bacteria tested, with the exception Peptostreptococcus micros.
One study investigated the antimicrobial efficacy of medicated filling materials, including standard gutta-percha, iodoform gutta-percha (MGP), and gutta-percha with tetracycline.21 These medicated filling materials were tested against several strains of bacteria including Actinomyces israelii, Actinomyces naeslundii, E. faecalis, and Fusobacterium nucleatum. Standard gutta-percha and the iodoform-containing gutta-percha weakly inhibited F. nucleatum and A. naeslundii. In addition, the iodoform gutta-percha also inhibited A. israelii. Only the tetracycline-containing gutta-percha inhibited all bacterial strains, including E. faecalis.
In 1942, Bunn22 discovered that natural gutta-percha existed in a 1,4-trans-polyisoprene stereochemical structure. Natural rubber has a 1,4-cis-polyisoprene stereochemical structure. Both gutta-percha and natural rubber are high-molecular-weight stereo-isomers of polyisoprene. In the cis form of natural rubber, the CH2 group is on the same side of the double bond, whereas in the trans form of polyisoprene (gutta-percha) the CH2 groups are on the opposite side of the double bond as shown in Figure 1. The cis configuration of natural rubber allows for mobility of one chain past another and gives rise to the elastic nature of rubber, whereas the trans configuration of gutta-percha is more linear and crystallizes more readily making gutta-percha harder, more brittle, and less elastic than natural rubber.11,23 The scientific methods available to Bunn in 1942 did not allow for 100% identification of the 1,4-polyisoprene configuration, as he could not rule out the presence of a minority cis form.24 In 1993, Marciano et al.,24 using nuclear
[Figure 1. Stereochemical structure of gutta-percha, 1,4-trans-polyisoprene isomer (natural gutta-percha). CH2 groups are on opposite sides of the double bond for each successive monomer.]
magnetic resonance, were able to confirm that both natural and commercial gutta-percha mainly have a 1,4 trans stereochemical structure and that the coloring agent in commercial gutta-percha is erythrosine. Less than 1% of the sample had the 1,4 cis stereochemical structure.
Gutta-percha exists in two distinct crystalline forms, alpha and beta.22 Raw gutta-percha, as it comes directly from the tree, is in the alpha form. Once purified, gutta-percha, as it appears commercially in manufactured gutta-percha products, is in the beta crystalline form. There are few differences in physical properties between the two forms, merely a difference in the crystalline lattice depending on the annealing and/or drawing process used when manufacturing the final product.25 Although there is apparently no difference in the mechanical properties of the two crystalline forms, there are thermal and volumetric differences.11 Unlike many materials, there are volumetric changes associated with temperature changes in gutta-percha, which has clinical implications.
If the natural alpha form which comes from the tree is heated above 65°C, it will melt and become amorphous. If it is very slowly cooled at a rate of 0.5° per hour, the original alpha form will recrystallize. However, if the heated amorphous form cools normally, the beta form will crystallize.11 Schilder et al.26 investigated the temperatures at which the crystalline phase transitions occurred. They found that, when dental gutta-percha in the beta crystalline form was heated, a crystalline phase transition to the alpha form took place between 42° and 49°C, depending on the specific compound being tested. The alpha-to-amorphous phase transition occurred at a higher temperature of between 53° and 59°C, again depending on the make up of the specific compound being tested. This information is useful clinically, when the clinician needs the amorphous form of gutta-percha in order to flow gutta-percha into all parts of the canal and to utilize thermoplastic techniques.
In a study on the thermomechanical properties of gutta-percha, Schilder et al.27 found that compaction, as opposed to compression, is what occurs in clinical situations with gutta-percha. Additionally, the reduction in volume that takes place with mechanical manipulation of gutta-percha is due to the consolidation and collapse of internal voids in gutta-percha, and this occurs within compaction forces. Finally, there is no molecular spring back after compaction of gutta-percha that would aid in the seal of gutta-percha within the root canal system. To overcome the shrinkage of gutta-percha as it cools, it is necessary to put pressure on the gutta-percha with a plugger.
Traditionally, the beta form of gutta-percha was used to manufacture endodontic gutta-percha points to achieve an improved stability and hardness and to reduce stickiness. However, through special processing and/or modifications to the formulation of the gutta-percha compound, more alpha-like forms of gutta-percha have been introduced, resulting in changes in the melting point, viscosity, and tackiness of the gutta-percha. Gutta-percha with low viscosity will flow with less pressure or stress,25 whereas an increase in tackiness will help create a more homogeneous filling. Various manufacturers have introduced products to take advantage of these properties (e.g., Themafil, Densfil, MicroSeal).16
Gutta-percha points come in the standardized ISO (International Standards Organization) sizes to correspond to endodontic instruments. Initially, the ISO-sized gutta-percha points came in the standard 0.02 taper to match the instruments available in that era. Now gutta-percha points are available in the increased taper sizes of 0.04, 0.06, etc to match the endodontic instruments that have these greater tapers. Color coding to match the ISO size is available on most gutta-percha points marketed today (Figure 2).
The traditional configuration of gutta-percha points is manufactured in a form that does not correspond to
[Figure 2. Assorted gutta-percha points and absorbent paper points with 0.06 taper are shown here, with color coded ends for easy identification of the size of the point.]
ISO sizes but has tapers that closely match the final instrumented size of canals. These traditional sizes (extra-fine, fine-fine, medium-fine, fine, fine-medium, medium, medium-large, large, and extra-large) have long been used in warm vertical obturation techniques and also match spreader sizes used in lateral compaction techniques.
With the thermoplasticized injectable techniques of gutta-percha placement and obturation of canals, the gutta-percha is produced in pellet form that may be loaded into the heating devise (Obtura III) or as prepackaged cannulas or cartridges (UltraFil, Calamus, Elements). Carrier-based gutta-percha products have gutta-percha surrounding a carrier made of metal or plastic.
Gutta-percha that has been stored for extended periods of time can become brittle with aging. Sorin et al.28 presented a method to rejuvenate aged and brittle gutta-percha by immersing it in hot tap water (above 55°C) until the grasping forceps indents the now softened gutta-percha. The gutta-percha is then removed from the hot water and immediately quenched in cold tap water (less than 20°C) for several seconds. The gutta-percha point can now be sterilized and used to obturate the canal.
Gutta-percha should be stored in a cool location with low humidity. Kolokruis et al.29 investigated the effects of moisture and aging on gutta-percha. They found that high humidity causes the absorption of water by the gutta-percha points, which lowers the values for tensile strength and torsional strain resistance, increases the value for elongation, and has a plasticizing effect on the gutta-percha cones. The plasticizing effect is due to the insertion of water molecules in the polymer chains.
Senia et al.30 suggested sterilizing gutta-percha prior to insertion into the canal by immersion into 5.25% sodium hypochlorite for at least 1 minute to kill bacteria and spores on gutta-percha. Examination with a dissecting microscope showed no adverse effects on the gutta-percha points that were immersed for 5 minutes in 5.25% sodium hypochlorite.
In a scanning electron microscope (SEM) study, Short et al.31 examined the affect of the sodium hypochlorite on gutta-percha points and determined that gutta-percha fresh from the box had no crystals on its surface. All the gutta-percha points placed in sodium hypochlorite had sodium chloride crystals present after the rapid-sterilization technique using 5.25 and 2.5% sodium hypochlorite. However, the sodium chloride crystals could be removed from the gutta-percha surface by 96% ethyl alcohol, 70% isopropyl alcohol, or distilled water.
The structural effects of sodium hypochlorite solutions on gutta-percha points were examined in an atomic force microscopy study by Valois et al.32 They found aggressive deteriorating effects on the gutta-percha points that had been placed in 5.25% sodium hypochlorite for 1 minute. After 5 minutes in either 2.5% or 5.25% sodium hypochlorite, there were topographic changes. However, a 0.5% solution of sodium hypochlorite did not cause any alteration in the topography or elasticity of gutta-percha points. They concluded that a 0.5% solution of sodium hypochlorite would be a safe alternative for rapid decontamination of gutta-percha points.
As another alternative for the disinfection of gutta-percha points, Gomes et al.33 looked at the effectiveness of chlorhexidine and sodium hypochlorite as solutions for the disinfection of gutta-percha points. In their boxes, gutta-percha points had a contamination rate of 5.5%. Microbes found most frequently, after intentional contamination with gloves, were Staphylococcus organisms. Chlorhexidine was not effective in eliminating Bacillus subtilis spores on gutta-percha, whereas 5.25% sodium hypochlorite eliminated spores on gutta-percha after 1 minute of disinfection.
Figure 1. Stereochemical structure of gutta-percha, 1,4-trans-polyisoprene isomer (natural gutta-percha). CH2 groups are on opposite sides of the double bond for each successive monomer. Adapted and reproduced with permission from Marciano J et al (1993).240
Figure 2. Assorted gutta-percha points and absorbent paper points with 0.06 taper are shown here, with color coded ends for easy identification of the size of the point. Reproduced with permission of Brasseler USA.
Edited: 13/06/2011 23:08
|Date: 13/06/2011 22:54|
Re: Root Canal Filling Materials
Yee et al.34 introduced the concept of obturating root canals using injection-molded thermoplasticized dental gutta-percha. They developed a prototype devise (PAC-160) where gutta-percha points were loaded into a pressure syringe and heated to 160°C. They injected the heated and softened gutta-percha into prepared canals, with and without sealer. They found injected thermoplasticized gutta-percha could produce an effective apical seal, especially when used with sealer. They introduced what would become the Obtura unit.
Injectable thermoplasticized gutta-percha may be used as a primary obturation technique, or, as it is used most often today, as a back-filling technique to fill the coronal aspects of the canal after the initial placement and compaction of gutta-percha by other techniques in the apical portion of the canal. The thermoplasticized gutta-percha injection techniques are classified as high-temperature and low-temperature thermoplasticized gutta-percha injection systems. These systems have made obturation quicker with the back-filling technique.
The first commercially available thermoplasticized gutta-percha system was the Obtura system. The Obtura
[Figure 3. Obtura III Thermoplasticized gutta-percha delivery system by Obtura Spartan.]
III Unit (Obtura/Spartan Corp., Fenton, MO) (Figure 3) is a high-temperature thermoplasticized gutta-percha system that requires gutta-percha pellets to be inserted into a delivery system gun, and then the gutta-percha pellet is heated to 150° to 200°C prior to delivery into the canal system. The warmed and softened gutta-percha is then delivered through 20-, 23-, or 25-gauge needles. Obtura gutta-percha also comes in the Flow-150 pellets, which is lower temperature thermoplasticized gutta-percha, and requires heating only to 150°C. The Obtura III also can be used with Resilon pellets, and lower temperatures are required to thermally soften the Resilon.
In a clinical study using the Obtura II system, Tani-Ishii and Teranaka35 reported an overall success rate of 96% with a 1-year follow-up with cases obturated only with the Obtura II thermoplasticized injection technique.
Several studies have evaluated the safety of the temperatures used with injectable thermoplasticized systems and, for the most part, found them to be well below the critical 10°C rise in temperature that will cause damage to the periodontal ligament and bone.36-39 According to a study by Lipski,40 high-temperature thermoplasticized injectable gutta-percha in mandibular incisors may show an increase in temperature above the 10°C rise that is crucial if damage to the attachment apparatus is to be prevented. Maxillary incisors, however, did not show an external temperature rise above 10°C.
[Figure 4. Elements thermoplasticized gutta-percha delivery system with System B heat source by Sybron Endo.]
The Elements system (Sybron Endo, Orange, CA) is a high-temperature thermoplasticized gutta-percha system that uses preloaded gutta-percha cartridges that are heated prior to delivery through the unit by an activation button. The gutta-percha is heated to 200°C. The gutta-percha is delivered through a 45° pre-bent needle that comes in sizes 20, 23, or 25 gauges (Figure 4).
The Calamus system is manufactured by (Tulsa Dental Products, Tulsa, OK). The high-temperature system heats the gutta-percha cannulas from 60° to 200°C. The delivery system may be activated by finger pressure on a blue ring with multiple positions. Besides the temperature control, the flow rate may be controlled by the operator as well. The flow rate of the softened and heated gutta-percha may be
[Figure 5. Calamus thermoplasticized gutta-percha delivery system by Tulsa Dentsply.]
regulated from 20, 40, 60, 80, and 100%. The Calamus unit only comes with needle sizes of 20 and 23 gauges (Figure 5).
UltraFil (Hygienic Corp., Akron, OH) is a low-temperature thermoplasticized gutta-percha delivery system that has prepackaged cannulas with attached 22-gauge needles. The gutta-percha is prepared in the alpha phase form so that it softens at a temperature of 70° to 90°C in the heating unit. Once heated, the cannulas are then placed in the injection syringe and the softened thermoplasticized gutta-percha is ready for injection into canal.
Michanowicz and Czonstkowsky41 in a dye study using a low-temperature injection system (70°C) found that when sealer was used, there was very little leakage. They used no compaction with this technique. Lipski42 found temperatures transmitted to the periodontal ligament with the UltraFil system were below levels causing damage or injury.
Figure 3. Obtura III Thermoplasticized gutta-percha delivery system by Obtura Spartan. Reproduced with permission from Obtura Spartan.0
Figure 4. Elements thermoplasticized gutta-percha delivery system with System B heat source by Sybron Endo. Reproduced with permission from Sybron Endo.0
Figure 5. Calamus thermoplasticized gutta-percha delivery system by Tulsa Dentsply. Reproduced with permission of Tulsa Dentsply.0
Thermomechanical Compaction of Gutta-Percha
Several thermomechanical compaction methods and products have been marketed. McSpadden first introduced the McSpadden Compactor, which resembled a reverse Hedstrom file, which was rotated at up to 20,000 rpm. Heat generated by friction softened gutta-percha, and the blade design pushed material apically.
The MicroSeal System (Sybron Endo) was also developed by John McSpadden. He redesigned the Compactor into the NT Condenser that is used with the Microseal System. The NT Condenser rotates at slower speeds (1,000 to 4,000 rpm) than the original McSpadden Compactor and utilizes nickel-titanium instruments.
The system uses MicroSeal gutta-percha master cones, and specially formulated gutta-percha, termed low-fusing or ultra-low-fusing gutta-percha, in a cartridge that is heated in the MicroSeal heater. This specially formulated low-fusing gutta-percha is advertised to be alpha phase gutta-percha, as are the points. A rotating mechanical condenser in a handpiece is coated with the heated gutta-percha and inserted into the canal. This rotating condenser creates heat from friction that thermally softens the single gutta-percha master point previously seated in the canal. It also flows laterally, by centrifugal force, the low-fusing or ultra-low-fusing gutta-percha coated on the condenser into all aspects of the canal.43
Cathro and Love44 compared MicroSeal with a technique using the System B with Obtura II backfill obturation. The MicroSeal technique produced a dense homogenous gutta-percha fill at the apical 1 and 2 mm similar to the System B/Obtura II technique. Further coronally, the sealer became mixed into the MicroFlow gutta-percha, producing a heterogeneous mass with less solid gutta-percha compared with the System B/Obtura II technique.
The concept of a carrier-based thermoplasticized gutta-percha obturation method was introduced by Johnson in 1978.45 These products are marketed today as ThermaFil Plus Obturators (Tulsa Dental Products) (Figure 6), GT Obturators (Tulsa Dental Products), ProTaper Obturators (Tulsa Dental Products), Densfil
[Figure 6. ThermaFil Plus Obturator by Tulsa Dentsply.]
(Dentsply Tulsa, Tulsa, OK), and Soft-Core (Soft-Core System, Inc., CMS Dental, Copenhagen, Denmark).
The original ThermaFil obturators had a metal carrier, now replaced with a grooved plastic carrier. Gutta-percha, which coats the carrier, is said to be alpha phase gutta-percha, and certainly after heating in the ThermaFil oven, the gutta-percha is in the alpha or amorphous phase.
Gutmann et al.46 compared lateral compaction with ThermaFil obturation and found that curved canals, treated with ThermaFil, resulted in a denser, better-adapted obturation on radiographic examination than those obturated with lateral compaction. However, both showed acceptable root canal fills in the apical one third, and ThermaFil extruded more material beyond the apex. In the second part of the study, no significant difference was seen in dye leakage after obturation with lateral compaction or ThermaFil. Both demonstrated dye leakage over a 5-month period.47
Becker and Donnelly48 in a literature review of ThermaFil obturation made these observations. ThermaFil appears to seal the apical foramen as well as other thermoplasticized techniques, lateral compaction techniques, or vertical compaction techniques.47,49-60 ThermaFil appears to adapt well to canal walls, but the long-term seal may be affected by exposed (bare) carrier.61 Corrosion of metal carriers should not cause concern. There is significantly more extrusion of gutta-percha compared with lateral compaction.46,56,60 Coronal leakage varies by study, but ThermaFil appears to allow significantly more leakage.62-64 The effect of post-space preparation on the apical leakage of ThermaFil obturators varied depending on the particular study.65-72 Re-treatment may be more difficult, especially with metal carriers and if the canal has been prepared for a post.72-76 Metal carriers may limit the ability to perform root-end resection.77,78
Felstead et al.52 examined apical leakage and found no statistically significant difference among teeth obturated with ThermaFil when heated to 100°, 120°, or 144°C, but there was a trend toward less leakage with lower temperatures. There was no significant leakage difference between teeth obturated with ThermaFil or lateral condensation.
Clark and El Deeb56 investigated the sealing ability of plastic versus metal carriers in ThermaFil obturators. Both carrier types were rarely completely entombed by gutta-percha in the apical third; however, no leakage was detected in any of the obturated canals. Both ThermaFil groups yielded significantly more cases of apically extruded gutta-percha compared with the lateral condensation group. Extrusions were found to occur significantly more in straight than curved canals.
Weller et al.79 compared three types of ThermaFil obturators, the Obtura II technique, and lateral compaction for the ability of the gutta-percha to adapt to the canal walls. The Obtura II injectable technique demonstrated the best adaptation of gutta-percha to the prepared root canal followed by the plastic and titanium ThermaFil obturators that were similar, followed by the stainless steel ThermaFil obturators, and finally by the lateral compaction technique, which showed the poorest adaptation of gutta-percha to the canal walls.
GT Obturators are designed to be used after preparation with GT files (Tulsa Dental Products), and ProTaper obturators after preparing a canal with Pro-Taper files (Tulsa Dental Products).
Robinson et al.80 compared extrusion of gutta-percha in teeth instrumented with ProFile 0.06 or ProFile GT and obturated with ThermaFil Plus obturators or ThermaFil GT obturators, respectively, or with warm vertical condensation. Extrusion of gutta-percha was seen more often in the teeth obturated with ThermaFil GT obturators, followed by teeth obturated with ThermaFil Plus obturators, with the least amount of extrusion occurring with the warm vertical condensation technique with either instrumentation method.
In one study, the percentage of gutta-percha-filled area in the apical third of root canals obturated with either lateral condensation technique, System B technique, or ThermaFil technique was examined. There was no significant difference between the percentages of gutta-percha-filled area for lateral condensation or System B technique, but the coated carrier gutta-percha system (ThermaFil) produced a significantly higher percentage of gutta-percha-filled area than the other two techniques.81
Temperatures produced by heated carrier-based gutta-percha have been found to be at levels safe for bone and periodontal ligament.40,82
Densfil (Maillefer/Dentsply International, York, PA) is a carrier-based gutta-percha system with both plastic and titanium carriers, a spin-off of ThermaFil.
[Figure 7. SimpliFil has a metal carrier that comes in ISO sizes 35 to 130 with a 5 mm plug of gutta-percha or Resilon on the end.]
SimpliFil (LightSpeedUSA, San Antonio, TX) (Figure 7) is a 5 mm apical plug of gutta-percha or Resilon on the end of a file and is used similar to a carrier-based system. It has the advantage of not leaving the carrier in the canal, as it is twisted off of the apical plug.
Jarrett et al.83 compared the apical density of gutta-percha in palatal roots of maxillary molars when filled with SimpliFil, as recommended by the manufacturer; ThermaFil; warm vertical condensation Schilder technique; warm vertical continuous wave technique; mechanical lateral technique; cold lateral condensation technique; and a modified SimpliFil technique. SimpliFil, as recommended, and ThermaFil had the greatest mean obturated area, but neither was statistically better than mechanical lateral or warm vertical condensation (Schilder) technique. SimpliFil, as recommended, and ThermaFil were statistically better than cold lateral condensation technique, warm vertical condensation (continuous wave) technique, and the modified SimpliFil group. Mechanical lateral and warm vertical condensation (Schilder) techniques had statistically more obturated area than warm vertical condensation (continuous wave) and modified SimpliFil techniques. Cold lateral and warm vertical condensation (continuous wave) had significantly more obturated area than modified SimpliFil.
Shipper and Trope84 compared microbial leakage in canals obturated with one of the following techniques: lateral compaction, vertical compaction, Obtura II thermoplasticized injection technique, SimpliFil with Obtura II, FibreFil (Pentron Clinical Technologies, Wallingford, CT), or a combination of FibreFil and SimpliFil. Microbial leakage occurred more quickly in the lateral and vertical compaction techniques compared with SimpliFil and FibreFil techniques. A combination of an apical plug of gutta-percha with SimpliFil and a FibreFil coronal seal provided the best obturation.
SuccessFil is a carrier-based gutta-percha system combined with the UltraFil thermoplasticizied injection system to create what is marketed as the Trifecta System (Hygenic/Coltene/Whaledent). Goldberg et al.85 compared the sealing ability of Trifecta, lateral condensation and SuccessFil with lateral condensation. No statistically significant differences in leakage were seen between the groups.
JS Quick-Fill (JS Dental Manufacturing, Inc., Ridgefield, CT) is an alpha phase gutta-percha-coated titanium core in ISO sizes 15 to 60. The carrier-based material is spun into the canal at low speed, and the core may be left in the canal or slowly removed.
Figure 6. ThermaFil Plus Obturator by Tulsa Dentsply. Reproduced with permission of Tulsa Dentsply.0
Figure 7. SimpliFil has a metal carrier that comes in ISO sizes 35 to 130 with a 5 mm plug of gutta-percha or Resilon on the end. Reproduced with permission of LightSpeed.0
Properties of Gutta-Percha
Gutta-percha is generally regarded as a very acceptable material with good biocompatibility with the periapical tissues. This has, for the most part, been verified in several studies, with the exception that some formulations of gutta-percha have produced localized severe inflammatory reactions in animals.86 Wolfson and Seltzer,87 in a 1975 study, found severe tissue reaction to eight brands of gutta-percha they injected into the skin of rats.
Tavares et al.88 looked at the reaction of rat subcutaneous tissue to implants of different commercially available gutta-percha compared with Teflon control cylinders. Studies were conducted on Kerr and Hygenic brands of gutta-percha, and cylinders used with the UltraFil thermoplastic injectable gutta-percha from Hygenic Corp. The Kerr points gave mild reactions throughout all experimental periods, and the UltraFil cylinders initially produced a foreign body reaction caused by the dispersion of filling material particles mediated by macrophages and giant cells, but this response decreased with time and thus was considered biologically acceptable. The Hygenic gutta-percha points caused a severe initial inflammatory tissue reaction suggestive of bioincompatibility.
The ingredients of gutta-percha, such as zinc oxide, may contribute to the cytotoxic effects of some commercial gutta-percha.89 However, other studies have suggested that the zinc oxide component may reduce the toxicity of other ingredients, especially rosin and resin acids.90
The tissue toxicity exerted by gutta-percha is more evident in the advent of an overfill or overextension of gutta-percha into the periapical area. Sjogren et al.91 demonstrated that the size of gutta-percha particle may make a difference in the intensity of the inflammatory response. Large gutta-percha particles had very little inflammation around them, and appeared to be well encapsulated, whereas the smaller particles of gutta-percha caused a more intense localized response. Additionally, they found that gutta-percha with a rosin and chloroform component invoked a response considered severe.
In a study by Holland et al.,92 one brand or formulation of gutta-percha caused a severe inflammatory response in rat connective tissue with a fibrous capsule formation, whereas another brand was well tolerated.
Serene et al.93 looked at the activation of complement to examine the inflammatory response of four different commercially available brands of gutta-percha, and the ingredients in one of the brands. This in vitro study showed that each of the four brands of commercially available gutta-percha and each of the ingredients could cause activation of the complement system.
Although some gutta-percha has been shown to be cytotoxic, invoking inflammatory reactions in connective tissue, the most toxic portion of the sealer-gutta-percha obturation is the sealer.86
Because gutta-percha and gutta-balata are derived from the Paliquium gutta and M. globsa trees, which are of the same botanical family of trees as the natural rubber latex tree, H. brasiliensis, there was concern about the possible cross-reactivity between gutta-percha and natural rubber latex in individuals who may have immediate-type hypersensitivity to natural rubber latex. There have been case reports suggesting that gutta-percha may release proteins that induce reactions in latex-allergic individuals.94,95 In these cases, the symptoms were uncharacteristic of those routinely experienced by patients with latex allergies. Other causes, more directly related to the quality of the endodontic treatment itself, may have been the reason for the patients' symptoms. These case reports did not prove the cross-reactivity between Hevea latex and gutta-percha. On the other hand, Knowles et al.96 and Kleier and Shibilski97 presented case reports where gutta-percha was successfully used to obturate canals in patients with documented IgE antibody-mediated allergy to natural rubber latex.12 Studies by Costa et al.12 and Hamann et al.98 using the radioallergosorbent test (RAST) inhibition and enzyme-linked immunosorbent assay (ELISA)98 showed that commercially available gutta-percha alone is not likely to induce symptoms in the patient with type I natural rubber latex allergy and that commercially available gutta-percha can safely be used in these patients. The refining process for gutta-percha is so severe that most proteins would be denatured by the process. Raw gutta-balata was the only substance that showed cross-reactivity with natural rubber latex.12 None of the processed gutta-percha products, or natural raw gutta-percha, showed any cross-reactivity with natural rubber latex.12 Nevertheless, it is always prudent to investigate natural rubber latex allergies in patients because it is very common, particularly among health care workers (17%) and spina bifida patients (67%).99-101
Newer Solid-Core Filling Materials
Resilon (Pentron Clinical Technologies), and RealSeal (Sybron Endo), is a polycaprolactone core material with difunctional methacrylate resin, bioactive glass, bismuth and barium salts as fillers, and pigments, which is used with a resin sealer (Epiphany or Real-Seal) that is packaged with the core filling material (Figures 8). The rational behind the product is to create a "monoblock" consisting of a resin sealer with
[Figure 8. Epiphany sealer is a resin type of sealer used with polycaprolactone core materials such as Resilon core material.]
resin tags that enter into and bond to dentinal tubules, and to the dentin on the canal wall, as well as adhesively bonding to the core material, and which can also be light cured and sealed coronally as well. The Resilon system consists of a primer, a sealer, and synthetic polymer points or pellets.
Whereas the sealer used with Resilon is discussed under the discussion on sealers later in this chapter, the Resilon system, core material and sealer, has to be used together, as it is one system, and each part relies on the other parts to be successful.
The polyester core material is marketed in ISO-sized points with accessory points for lateral compaction and warm vertical techniques, or pellets for use in thermoplasticized techniques.101 The temperatures used in the thermoplasticized techniques for the polyester resin core materials are lower than those used for gutta-percha techniques (150°C, compared to 200°C), but otherwise has handling characteristics that are similar to gutta-percha and allows for lateral compaction or warm vertical obturation techniques. In the case of using Resilon with the System B unit, the temperature is set at 150°C and the power is set at 10. If Resilon is used with the Obtura III thermoplasticizing unit with 25-gauge needles, the temperature is set at 160°C; with 23-gauge needles, the temperature is set at 140°C; and for use with 20-gauge needles, the temperature is set at 120° to 130°C.
One study compared Resilon with gutta-percha in terms of the melting point, specific heat capacity, enthalpy change with melting, and heat transfer. It was found that there was no difference in the melting point temperatures for the two materials, but Resilon had a significantly greater specific heat capacity and endothermic enthalpy change. There was a significant difference in the heat transfer test in the temperature increase between gutta-percha and Resilon within 3 mm of the heat source, with gutta-percha having a greater temperature change. They concluded that Resilon may not be thermoplasticized the same as gutta-percha because there is a higher specific heat, higher enthalpy change with melting, and less heat transfer.102
Nielsen and Baumgartner103 examined the depth of nickel-titanium spreader penetration in root canals having a 0.04 preparation size taper using 0.02 and 0.04 tapered master gutta-percha or Resilon points. A significant difference in penetration depth was found for both taper of the point and the material used. The depth of spreader penetration was greatest for 0.02 tapered Resilon, followed by 0.02 gutta-percha, followed by 0.04 tapered Resilon, and the least spreader penetration occurred with the 0.04 gutta-percha.
Shipper et al.104 investigated the resistance to bacterial penetration of gutta-percha with AH 26 sealer, gutta-percha with Epiphany sealer, and Resilon with Epiphany sealer. Each combination of core material and sealer was obturated with both lateral and vertical condensation techniques. The Resilon groups were found to have less leakage than the gutta-percha groups with respect to the number and rate of the specimens in each group that leaked. All Resilon and Epiphany sealer groups leaked significantly less than all groups in which AH 26 was used as a sealer.
By contrast, other investigators105 performed an ultrastructural evaluation of the apical seal in roots filled with a polycaprolactone-based root canal filling material. This study compared the ultrastructural quality of the apical seal achieved with Resilon and Epiphany sealer with that produced by gutta-percha and AH Plus sealer. The SEM revealed both gap-free regions and gap-containing regions in canals filled with both materials. The transmission electron microscope revealed the presence of silver deposits along the sealer-hybrid layer interface in the Resilon/Epiphany samples and between the sealer and gutta-percha samples. They concluded that a complete apical seal cannot be achieved with either combination of root canal filling material and sealer.
The susceptibility of a polycaprolactone-based root canal filling material (Resilon) to degradation has been investigated. Tay et al.106 examined what effect alkaline hydrolysis would have on disks of Resilon or gutta-percha using scanning electron microscopy and energy dispersive X-ray analysis. They found that for Resilon, the surface resinous component was hydrolyzed after 20 minutes of immersion in sodium ethoxide, which exposed the spherulitic polymer structure and subsurface glass and bismuth oxychloride fillers. Gutta-percha did not undergo alkaline hydrolysis when immersed in sodium ethoxide.
Tay et al.107 evaluated the susceptibility of Resilon, gutta-percha, and polycaprolactone disks to hydrolytic enzymes present in saliva or secreted by endodontically-relevant bacteria. All three materials had slight weight gains when incubated in phosphate-buffered saline. Gutta-percha showed similar weight gains with the enzymes, lipase polysaccharide, and cholesterol esterase, but Resilon and polycaprolactone exhibited extensive surface thinning and weight loss after incubation in lipase polysaccharide and cholesterol esterase. Glass filler particles in Resilon were exposed following surface dissolution of the polymer matrix, which created a rough surface topography. They concluded that biode-gradation of Resilon by bacterial and salivary enzymes warrants further investigation.
The interfacial strengths of Resilon with Epiphany sealer have been compared with those of gutta-percha with AH Plus sealer by Gesi et al.108 The gutta-percha/AH Plus testing group exhibited significantly higher interfacial strength than did the Resilon/Epiphany group, when premature failures that occurred in Resilon root slices were included. The gutta-percha root slices failed exclusively along the gutta-percha/sealer interface. The Resilon root slices failed predominantly along the sealer/dentin interface with recognizable, fractured resin tags. Detachment of Resilon from the Epiphany sealer was also observed in some specimens. The relatively low interfacial strengths of materials, gutta-percha/AH Plus, and Resilon/Epiphany seemed to challenge the concept that root strengthening is accomplished with either material.
Stratton et al.109 looked at the sealing ability of Resilon and Epiphany sealer versus that of gutta-percha and AH Plus sealer, by means of fluid filtration testing. They found significantly less leakage using Resilon and Epiphany as compared with the gutta-percha and AH Plus sealer.
Another study found Resilon with Epiphany sealer had less leakage after 30 days than gutta-percha and sealer. All canals obturated with gutta-percha and sealer, and those obturated with Resilon or gutta-percha without sealer leaked within 30 days.110
Wang et al.111 investigated the effects of calcium hydroxide medication on the sealing ability of Resilon and found that calcium hydroxide did not adversely affect the seal of the root canal system that was subsequently filled with Resilon.
In an investigation comparing the completeness of root canal obturation with gutta-percha techniques versus Resilon with Epiphany sealer, using lateral compaction and continuous wave obturation, results showed that lateral compaction of gutta-percha was the only group with significantly more voids than gutta-percha with the continuous wave obturation, or Resilon with Epiphany sealer using either obturation technique.112
Resilon has been reported to reinforce the root canal system because of its adhesion to the canal wall and integration of the core material.113 On the other hand, another study compared cohesive strength and the stiffness of Resilon and gutta-percha under dry conditions and after 1 month of water storage, to determine whether they are stiff enough to reinforce roots. They found that both Resilon and gutta-percha had relatively low cohesive strength and modulus of elasticity, and did not have enough stiffness to reinforce roots after endodontic therapy.114
Long-term results and clinical trials will be useful in the evaluation of Resilon as compared with gutta-percha, and the evolution of newer generations of Resilon may further improve the material.
Figure 8. Epiphany sealer is a resin type of sealer used with polycaprolactone core materials such as Resilon core material. Courtesy, James David Johnson.0
Paste Filling Materials
Zinc oxide is a major component of many paste materials used in endodontics. It is the other ingredients in many zinc oxide paste materials that are responsible for other properties and potential toxicity. These pastes will be discussed under the pastes containing other ingredients. Because of the solubility of zinc oxide, they do not make effective core filling materials.
A paste filling material that has been widely used in Eastern European countries and some Asian and Pacific Rim nations is a resin type of material known as "Russian Red."115 This is resorcin-formaldehyde paste, a type of phenol-formaldehyde or Bakelite resin.101 Orstavik101 reported it is strongly antimicrobial, but with the disadvantage of shrinkage in the canal once placed, and that it often stains tooth structure a dark red. Sometimes re-treatments can be difficult, if the resin sets completely and there is sufficient bulk to the material.115
Trailement SPAD is another resin-based type of paste material that has been used in Europe.
Mineral Trioxide Aggregate
Mineral trioxide aggregate (MTA) has many uses in endodontics (Figure 9). MTA is used as a pulp-capping material,116-118 as a perforation repair agent,119-122 as a root-end filling material,123-125 as an apical barrier,126-128 and as an intraorifice barrier,129 and
[Figure 9. White and gray ProRoot mineral trioxide aggregate (MTA) by Tulsa Dentsply.]
may be considered as a paste filling material for the obturation of root canals. Because of its sealing ability, biocompatibility, and other desirable properties, it would seem to be a paste filling material that is indicated when more conventional core filling materials cannot be used. The major drawbacks of MTA are its somewhat difficult handling characteristics, which may be overcome with experience, and its extended setting time of at least 3 hours or more. Its many favorable properties and characteristics make it a valuable material in many aspects of endodontics.
ProRoot MTA (Tulsa Dental Products, Tulsa, OK) was introduced by Torabinejad et al.123 in 1993 as a root-end filling material and as a root perforation repair material.119 They reported the ingredients as tricalcium silicate, tricalcium aluminate, tricalcium oxide, and silicate oxide, with some other mineral oxides that were responsible for the chemical and physical properties of the aggregate. The powder consists of fine hydrophilic particles that set in the presence of moisture. The hydration of the powder results in a colloidal gel with a pH of 12.5 that will set in approximately 4 hours.130
Several studies have stated that MTA is very similar in nature to commercial Portland cement.131-135 Wucherpfenning and Green132 analyzed MTA and Portland cement by X-ray diffraction and reported that they were similar macroscopically and microscopically. Estrela et al.133 showed that Portland cement contains the same chemical elements as MTA, with the exception of bismuth oxide, which is added to MTA to increase its radiopacity. Duarte et al.136 reported that MTA Angelus is 80% Portland cement and 20% bismuth oxide. Sarkar et al.137 stated that MTA is a mechanical mixture of three powder ingredients, which are Portland cement (75%), bismuth oxide (20%), and gypsum (5%), with trace amounts of SiO2, CaO, MgO, K2SO4, and Na2SO4. They also listed the ingredients of the major component, Portland cement, as dicalcium silicate, tricalcium silicate, tricalcium aluminate, and tetracalcium aluminoferrite.
One of the very favorable properties of MTA is its outstanding sealing ability. This has been verified in many studies using MTA as a root-end filling material and for sealing perforations in both dye leakage and bacterial leakage models. Torabinejad et al.123 using an aqueous solution of rhodamine B fluorescent dye found MTA leaked significantly less than amalgam or ethoxybenzoic acid (Super EBA) as a root-end filling material. In another dye study, Torabinejad et al.138 found MTA sealed better as a root-end filling material than amalgam, Intermediate Restorative Material (IRM), or Super EBA, even in the presence of blood contamination. Gondim et al.139 demonstrated, with a dye study, that MTA leaked significantly less than Super EBA or IRM, regardless of the finishing technique employed. In a bacterial leakage investigation of root-end filling materials, Torabinejad et al.140 showed that MTA leaked significantly less than the other root-end filling materials tested. MTA was also found to allow less leakage of endotoxin in a study by Tang et al.141 Tselnik et al.129 examined bacterial leakage with MTA or a resin-modified glass ionomer as a coronal barrier. They found both gray and white MTA, when used as a coronal barrier, prevented microbial leakage for over 90 days. Nakata and coworkers121 found that MTA provided a better seal than amalgam to prevent the leakage of F. nucleatum into furcation perforations.
In a SEM study, Torabinejad et al.142 showed that MTA had better marginal adaptation than amalgam, Super EBA or IRM. Other studies using the SEM have agreed with these findings with regard to MTA adaptation.143,144 Xavier et al.145 examined both dye leakage and marginal adaptation as viewed under the SEM and found that MTA Angelus leaked significantly less than a glass ionomer, but statistically more than Super EBA. They found that MTA Angelus had much better marginal adaptation than EBA, or the glass ionomer when viewed under the SEM. Mangin et al.146 found no difference in leakage of radioactive labeled bacteria between hydroxyapatite cement, MTA, and Super EBA when used as root-end filling materials.
In a fluid filtration model, Bates et al.147 found MTA was comparable with Super EBA in the prevention of leakage, but Wu et al.148 reported MTA leaked significantly less than Super EBA. DeBruyne et al.149 using a fluid transport and capillary flow porometry technique found that after 1 day, and after 1 month there was no statistical significant difference in leakage between a reinforced glass ionomer cement and white MTA in root-end fillings. At 6 months, however, the glass ionomer leaked significantly less than MTA. There were no significant differences observed with flow porometry between pore diameters of the materials tested.
The effects of the thickness and of resection of MTA have been investigated. Andelin et al.150 examined leakage after the resection of MTA placed in canals before the root end was resected and found that the resection of set MTA did not affect its sealing ability. Lamb et al.151 had similar findings, as long as at least 3 mm of MTA remained. Valois et al.152 examined the influence of thickness of MTA on the sealing ability of the material and showed that a 4 mm thickness of MTA was significantly more effective in preventing protein leakage than lesser thicknesses of MTA. Matt et al.153 found that for an apical barrier, 5 mm of MTA was significantly harder than a 2 mm barrier, and allowed significantly less leakage. These dimensions may be important, not only in the depth of root-end fillings with MTA but when it is used as an apical barrier, or as a perforation repair material, or for other purposes.
MTA has been studied extensively for its biocompatibility with its application as a root-end filling material in root-end endodontic surgery. Cell culture studies have demonstrated that the cytotoxicity of MTA was significantly less than that of IRM or Super EBA.154 Implantation of MTA into tibias and mandibles of guinea pigs resulted in a tissue reaction considered favorable and slightly milder than that of Super EBA.155 Koh et al.156 found favorable biologic responses to MTA from human osteoblasts, and favorable cellular response to MTA.157
Haglund et al.158 compared MTA, amalgam, IRM, and a composite resin for their effects on mouse fibroblasts and macrophages. They found all four materials inhibited cell growth. There were significantly fewer cells cultured with the fresh IRM and composite groups compared with the MTA and amalgam groups, and there was no difference between a fresh mix of MTA and a fresh mix of amalgam. For set materials, there was no significant differences in the fibroblast cell growth between MTA, amalgam, and the composite resin. In the fibroblast cell line, set IRM had significalntly fewer surviving cells than the other set materials. There was a significant difference in the survival of cells in the macrophage cell line in the presence of the set materials between the composite resin group and MTA, and between the composite resin group and amalgam, with fewer macrophages surviving in the presence of the composite resin set material. Set IRM had significantly fewer cells survive than the other set material in the macrophage cell line also. DeDeus et al.159 compared the cytotoxicity of ProRoot MTA, MTA Angelus, and Portland cement and found no significant difference between the three materials in terms of cytotoxicity and that all three initially showed similar elevated cytotoxic effects that decreased gradually with time, allowing the cell culture to become reestablished.
Hernandez et al.160 studied the effect of mixing chlorhexidine with MTA versus MTA mixed with water on the apoptosis and cell cycle of fibroblasts and microphages. They found that mixing MTA with chlorhexidine induced apoptosis of fibroblasts and macrophages and decreased the percentage of both cell types in the S phase (DNA synthesis) of cell cycles. Thus, mixing sterile water with MTA was determined to be less cytotoxic than mixing MTA with chlorhexidine. Melegari et al.161 studied the production of prostaglandin E2 (PGE2) and the viability of cells cultured in contact with freshly mixed Roth's 801 sealer, Sealapex sealer, and MTA. It was found that none of the materials stimulated the release of PGE2.
MTA is also reported to have qualities that may provide an environment for repair and regeneration of periapical tissues. MTA has shown an inductive effect on cementoblasts in dogs and monkeys.124,125 Zhu et al.162 showed osteoblasts attaching and spreading on MTA. Regan et al.163 demonstrated that both MTA and Diaket can support almost complete regeneration of the periradicular periodontium when used as a root-end filling material on teeth that are not infected. Baek et al.164 found that MTA showed the most favorable periapical tissue response and that there was neoformation of cemental coverage over MTA.
There is conflicting information as to whether gray and white MTA have the same physical properties and biocompatibility. Holland et al.135,165,166 have shown that both white and gray formulations are biocompatible when implanted into rat connective tissue. Perez et al.167 demonstrated that white MTA was less biocompatible than gray MTA. Camilleri et al.168 showed no difference between the gray and white formulations of MTA. Ribeiro et al.169 showed no difference in cytotoxic effects for gray MTA, white MTA, or Portland cement. The same group found no difference in genotoxicity or cytotoxicity between gray or white MTA.170 Asgary et al.171 by electron probe microanalysis observed that the concentrations of Al2O3, MgO, and particularly FeO in white MTA are considerably lower than those found in gray MTA. The FeO is thought to be the primary ingredient responsible for the color differences between white and gray MTA. Oviir et al.172 investigated the proliferation of oral keratinocytes and cementoblasts on gray and white MTA. They found both cell types grew significantly better on the surface of white MTA compared with gray MTA. In addition, both cell types showed significantly higher proliferation when grown on 12-day-cured gray MTA compared with 24-hour-cured gray MTA. Matt et al.153 found that white MTA leaked significantly more than did gray MTA and that a two-step technique, where a moist cotton pellet is placed over the MTA for 24 hours to allow it to set, showed less leakage than a one-step technique for placing an apical barrier.
There is some conflicting opinion as to whether a moist cotton pellet is needed to allow the MTA to set properly when used within the root canal system, other than as a root-end filling material where it is in contact with moisture. This step adds another appointment to the treatment when MTA is used as a perforation repair material, as an apical barrier, or as an intraorifice barrier. There have been case reports where a moist cotton pellet is used between appointments to allow for the MTA to set.126-128 On the other hand, Sluyk et al.173 showed that the retention characteristics of MTA used as a perforation repair material was not altered by the placement of either a dry or a moist cotton pellet over the MTA, and the moisture from the periradicular tissues may provide adequate moisture to allow the MTA to set properly. Matt et al.153 did show, however, that the application of a moist cotton pellet significantly reduced leakage of MTA used as an apical barrier.
The long-term solubility of MTA was investigated by Fridland et al.174 Their results showed that MTA is capable of partially releasing its soluble fraction into an aqueous environment over a long period of time and it still maintains its high pH level of 11 to 12 over at least 78 days, while also maintaining its insoluble matrix of silica which produces MTA's structural integrity even while in contact with water. This soluble fraction is mainly composed of calcium hydroxide, which may provide the alkalinity favorable for cell division and matrix formation for healing of periradicular tissues and for antimicrobial activity. Sarkar et al.137 speculated that after placement of MTA in root canals and its gradual dissolution, hydroxyapatite crystals nucleate and grow, filling the microscopic space between MTA and the dentinal wall. This seal is first mechanical, but then they envision a reaction between the apatite layer and the dentin in the form of a chemical bond, and a seal between MTA and dentin.
Some investigators are looking into modifications of Portland type cements to alter the setting properties and handling characteristics. One of the main disadvantages of using MTA is its extended setting time. In industrial uses of Portland cement, the setting time may be increased by adding gypsum or reduced to a flash set by removing gypsum. Camilleri et al.175 investigated a new accelerated Portland cement. The setting time of the Portland cement was reduced by excluding gypsum in the last stage of the manufacturing process. The biocompatibility testing of this accelerated Portland cement was not altered by adding bismuth oxide for radiopacity and had similar biocompatibility as gray MTA, white MTA, and white Portland cement. Future research will have to determine whether altering the undesirable aspects of MTA can be accomplished without affecting its very desirable properties of sealing, biocompatibility, and favorable conditions for repair and regeneration of periradicular tissues.
Figure 9. White and gray ProRoot mineral trioxide aggregate (MTA) by Tulsa Dentsply. Reproduced with permission of Tulsa Dentsply.0
Paraformaldehyde pastes may also be considered as sealers, and are used as sealers by some. The addition of paraformaldehyde is for its antimicrobial and mummifying effects, but unfortunately its severe toxicity to host tissues outweighs any antimicrobial effects it may possess as an ingredient in endodontic materials.
N2 paste (Indrag-Agsa, Losone, Switzerland) and its US counterpart, RC2B, is a liquid and powder paste. The liquid contains zinc oxide, bismuth nitrate, bismuth carbonate, paraformaldehyde, and titanium oxide. The liquid consists of eugenol, peanut oil, and rose oil.176 The contents of N2 have changed over the years in response to studies identifying toxic substances, such as lead oxide and organic mercury.177 It still contains large amounts of paraformaldehyde (4-8%).86 N2 has been found to be extremely toxic.178,179 Furthermore, because it is used as a paste, the extrusion of this toxic material is easier and has caused severe neurological damage in reported cases.180-183 The Food and Drug Administration (FDA) lists N2 or RC2B as an unapproved new drug not legally imported or shipped across interstate lines.184 The American Dental Association (ADA) Council of Dental Therapeutics does not approve the use of paraformaldehyde pastes or sealers. A case report of a dentist who was found liable for a patient's permanent disability as a result of root canal therapy with N2 (Sargenti's) paste was presented in the status report. The canal was obturated with N2, which reportedly extruded into the mandibular canal causing nerve damage, facial dysesthesia, and pain. The patient was awarded $250,000 (US) for injury.185
The American Association of Endodontists has issued a position paper on the use of paraformaldehyde-containing endodontic materials, recommending against their use.186 Some states, including Florida, have banned the use of paraformaldehyde pastes.187 Because of the toxicity, legal issues, risks to patients, and the fact there are numerous other obturating materials available that provide a better outcome, without risk to the patient, the use of these materials in modern-day endodontics cannot be supported.
Endomethasone (Septodont, Paris, France) is a liquid-powder sealer used in Europe. The powder contains dexamethasone, hydrocortisone acetate, thymol iodide, paraformaldehyde, and a radiopaque excipient, whereas the liquid contains eugenol, peppermint oil, and Anise oil.176 The difference between Endomethasone and other paraformaldehyde-containing sealers is the addition of the hydrocortisone. The toxicity of the paraformaldehyde still remains.
Riebler's paste (Amubarut; Wera Karl, Biesingen, Germany) is another paraformaldehyde-containing paste as is Trailement SPAD, another resin-based type of paste material that has been used in Europe.
|Date: 13/06/2011 22:55|
Re: Root Canal Filling Materials
REQUIREMENTS FOR AN IDEAL ROOT CANAL SEALING MATERIAL
In addition to the basic requirements for core filling materials, Grossman also listed the following 11 requirements for a root canal sealer:188,189
1. It should be tacky when mixed to provide good adhesion between it and the canal wall when set.
2. It should make a hermetic seal.
3. It should be radiopaque so it can be visualized in the radiograph.
4. The particles of powder should be very fine so they can mix easily with the liquid.
5. It should not shrink upon setting.
6. It should not stain tooth structure.
7. It should be bacteriostatic or at least not encourage bacterial growth.
8. It should set slowly.
9. It should be insoluble in tissue fluids.
10. It should be tissue tolerant, that is, nonirritating to periradicular tissues.
11. It should be soluble in a common solvent, if it is necessary to remove the root canal filling.
One might add the following to Grossman's original basic requirements:
12. It should not provoke an immune response in periradicular tissues.190-193
13. It should be neither mutagenic nor carcinogenic.194,195
Zinc Oxide-Containing Sealers
For many years, zinc oxide-containing sealers have been the most popular and widely used sealers. There are many formulations and brands of sealers that have zinc oxide as the primary ingredient, differing only by other components added to the sealers.
Zinc oxide sealers allow for addition of other chemicals, such as paraformaldehyde, rosin, Canada balsam, and others, all of which may increase their toxicity.86 Zinc oxide-containing sealers that have other ingredients will be discussed under those sections.
Grossman's original formula contained zinc oxide, staybelite resin, bismuth subcarbonate, barium sulfate, and sodium borate (anhydrous) with eugenol as the liquid component.188 It has been marketed as Procosol sealer, as well as other product names.
Roth's 801 sealer (Roth's Pharmacy, Chicago, IL) is essentially the same as Grossman's original formulation, with the substitution of bismuth subnitrate for bismuth subcarbonate. Eugenol is used as the liquid of the sealer (Figure 10).
Rickert's formula was an early zinc oxide-containing sealer. It has long been an acceptable standard, meeting most of Grossman's requirements for an ideal sealer. Its major drawback was the staining of tooth structure from the silver that was used for radiopacity.16 Rickert's formula was marketed as Kerr's Pulp Canal Sealer (Sybron Endo/Kerr, Orange, CA). Pulp Canal Sealer has been popularized by clinicians using the warm vertical obturation techniques. A major disadvantage of Pulp Canal Sealer was its rapid setting time, especially with heat and in regions with high temperatures and high humidity.16 To overcome this disadvantage, researchers formulated Pulp Canal Sealer EWT (Extended Working Time) (Sybron
[Figure 10. Roth Root Canal Cement is an example of a zinc oxide and eugenol sealer.]
Endo/Kerr) which reportedly has a working time of 6 hours.16
Tubli-Seal (Sybron Endo/Kerr) is a two-paste system contained in two separate tubes. Developed as a nonstaining alternative to the silver-containing Pulp Canal Sealer, Tubli-Seal is a zinc oxide-base paste with barium sulfate for radiopacity, and mineral oil, cornstarch, and lecithin. The catalyst tube has polypale resin, eugenol, and thymol iodide. Tubli-Seal is easy to mix but has the disadvantage of rapid setting time.16 Tubli-Seal EWT has the same properties as the regular setting Tubli-Seal but has an extended working time.
Wach's cement (Roth International Inc., Chicago, IL) consists of a powder of zinc oxide, bismuth subnitrate, bismuth subiodide, magnesium oxide, and calcium phosphate. The liquid contains oil of cloves, eucalyptol, Canada balsam, and beechwood creosote. The liquid gives Wach's cement a rather distinctive odor of an old-time dental office.16 It has the advantage of having a smooth consistency, and the Canada balsam makes the sealer tacky.
Nogenol (GC America, Inc., Alsip, IL) was developed to overcome the irritating effects of eugenol.196 This product is an extension of the noneugenol periodontal dressings. It is a two-tube, base and catalyst system with a base of zinc oxide, barium sulfate, bismuth oxychloride, and vegetable oil. Hydrogenated rosin, methyl abietate, lauric acid, chlorothymol, and salicylic acid in the catalyst accelerate the setting time.16
Medicated Canal Sealer (Medidenta International, Inc.) was developed by Martin.15 This sealer contains iodoform for antibacterial purposes and is to be used with MGP gutta-percha, which also contains 10% iodoform.16
Figure 10. Roth Root Canal Cement is an example of a zinc oxide and eugenol sealer. Courtesy, James David Johnson.0
Calcium Hydroxide-Containing Sealers
Sealapex (Sybron Endo/Kerr) is a calcium hydroxide-containing noneugenol polymeric sealer that is packaged as two tubes. Sealapex has zinc oxide in the base along with calcium hydroxide and also contains butyl benzene, sulfonamide, and zinc stearate. The catalyst tube has barium sulfate and titanium dioxide for radiopacity, and a proprietary resin, isobutyl salicylate, and aerocil R792.16 Sealapex had no greater dissolution than Tubli-Seal at both 2 and 32 weeks. It appears that Sealapex had a sealing ability comparable with Tubli-Seal and could withstand long-term leakage.197
Holland and De Souza198 studied Sealapex sealer to see if it could induce hard tissue formation. Sealapex with calcium hydroxide did encourage apical closure by cementum deposition. Closure was also observed in the control groups (5%) and in Kerr Pulp Canal Sealer groups (10%), but was associated with dentin chips that also stimulate cementum formation. Both Sealapex and Kerr Pulp Canal Sealer, when overextended, provoke a chronic inflammatory reaction in the periodontal ligament (PDL).
Apexit (Ivoclar Vivadent, Schaan, Liechtenstein) is a calcium hydroxide sealer with salicylates also incorporated into the formula.
CRCS (Calciobiotic Root Canal Sealer; Coltene/Whaledent/Hygenic, Mahwah, NJ) is a calcium hydroxide-containing sealer with a zinc oxide-eugenol-eucalyptol base. CRCS is a rather slow setting sealer, especially in dry or in humid climates. It may require up to 3 days to fully set.16 The set sealer is quite stable, which improves its sealing qualities, but may mean that calcium hydroxide is not as readily released, and the stimulation of cementum and bone formation may be severely limited.
Beltes et al.199 did an in vitro evaluation of cytotoxicity of calcium hydroxide-based root canal sealers. Sealapex was the most cytotoxic, followed by CRCS, with Apexit being the least cytotoxic with the least decrease in cell density.
Siqueira et al.200 investigated the sealing ability, pH, and flow rate of three calcium hydroxide-based sealers (Sealapex, Sealer 26, and Apexit). There was no significant difference found between apical sealing ability and dye penetration. All calcium hydroxide sealers alkalinized adjacent tissues. Sealer 26 had significantly superior flow characteristics. They concluded calcium hydroxide sealers compare favorably with zinc oxide and eugenol (ZOE) cements for use in obturation.
Vitapex (NEO Dental International, Inc, Federal Way, WA) is a sealer, which was developed in Japan, and contains, not only calcium hydroxide, but also 40% iodoform and silicone oil among other ingredients.
Epoxy resin sealers have an established record in endodontics, especially in the form of AH 26 and its successor AH Plus (Dentsply International, York, PA).
AH 26 (Dentsply International/Maillefer) is a bisphenol epoxy resin sealer that uses hexamethylenetetramine (methenamine) for polymerization and has been used for many years as a sealer.101,201 The methenamine will give off some formaldehyde as it sets, and this has been one of its major drawbacks. The highest amount of formaldehyde release is in the freshly mixed sealer, and the amount of formaldehyde
[Figure 11. AH Plus Root Canal Sealer by Tulsa Dentsply is a resin type sealer shown here in a mixing syringe.]
released goes down after 48 hours, and after 2 weeks the amount released is insignificant.202 The amount of formaldehyde produced during the setting process has been reported to be several thousand times lower than the long-term release from formaldehyde-containing sealers such as N2.86,201 Other disadvantages are staining and an extended working time. On the other hand, AH 26 does not seem to be affected by moisture, and will even set under water.16
AH Plus and ThermaSeal Plus (Dentsply International) (Figure 11) were formulated with a mixture of amines that would allow for polymerization without the unwanted formation of formaldehyde,201,203 but with all the advantages of AH 26, such as increased radiopacity, low solubility, slight shrinkage, and tissue compatibility. AH Plus is an epoxy-bis-phenol resin that also contains adamantine.101 AH Plus comes as a two-paste system, unlike the liquid-powder system of AH 26. AH Plus has a working time of 4 hours and a setting time of 8 hours. Other improvements over the older AH 26 formulation are the thinner film thickness and the decreased solubility of AH Plus, both about half that of AH 26. AH Plus has been shown to be less cytotoxic than AH 26, but both caused a dose-dependent increase in genotoxicity.176
Epiphany (Pentron Clinical Technologies) or Real-Seal (Sybron Endo) is a sealer that contains urethane dimethacrylate (UDMA), Poly(ethylene glycol) dimethacrylates (PEGDMA), ethoxylated bisphenol A-dimethacrylate (EBPADMA), Bisphenol-A-glycidyl-dimethacrylate (BisGMA) resins designed for use with the polycaprolactone core materials. Additionally, these sealers contain silane-treated barium borosilicate glass, barium sulfate, silica, calcium hydroxide, bismuth oxychloride with amines, peroxide, a photo inhibitor, and pigments. Epiphany sealer is a dual-cure dental resin composite sealer that self-cures in about 25 minutes. It comes with a self-etch primer with sulfonic acid-terminated functional monomer, Hydro-xyethylmethacrylate (HEMA), water, and polymerization initiator. Sodium hypochlorite may negatively affect bond strength of the primer, so after using sodium hypochlorite for irrigation, one should irrigate with ethylenediaminetetraacetic acid (EDTA) and sterile water. Peroxide-containing lubricants might also have a retarding effect on the resins, so a final rinse with EDTA and sterile water is recommended after using these lubricants. Chlorhexidine does not affect the bond strength. When obturation is completed, the coronal surface may be light-cured for 40 seconds to create a coronal seal.
In a study comparing Epiphany sealer with AH Plus and EndoREZ sealers for intraosseous biocompatibility for 4 and 12 weeks, as recommended by the Technical Report 9 of the Federation Dentaire Internationale (FDI), Sousa et al.204 found the inflammatory tissue reaction to EndoREZ was severe and the AH Plus inflammatory reaction went from severe to moderate with time, whereas Epiphany showed biological compataibility in regard to bone formation, and it also produced either no, or very slight inflammation.
In a direct comparison of physical and chemical properties of AH Plus and Epiphany sealers, Versiani et al.205 found there was no significant difference in flow or film thickness between AH Plus and Epiphany sealers. There was a statistical difference between the two with the solubility of Epiphany being 3.41% versus 0.21% for AH Plus, and for dimensional stability, there was also a statistical difference with AH Plus expanding 1.3% on setting and Epiphany expanding 8.1% following setting. The setting time, flow, and film thickness tests for both cements conformed to American National Standards Institute (ANSI)/ADA standards. Dimensional alteration tests for both sealers were greater than values considered acceptable by ANSI/ADA standards, and the values for Epiphany sealer with regard to solubility were also greater than values considered acceptable by ANSI/ADA.
Ungor et al.206 evaluated the push-out bond strength of the Epiphany-Resilon root canal filling system with the bond strengths of different pairings of AH Plus, gutta-percha, Epiphany, and Resilon. Their results showed that Epiphany with gutta-percha had significantly greater bond strength than all the other groups. There was no significant difference between the Epiphany with Resilon combination and the AH Plus with gutta-percha. Inspection of the surfaces revealed the bond failure to be mainly adhesive to dentin for all groups.
Diaket (3M/ESPE, Minneapolis, MN) has been a popular sealer in Europe for many years and is a polyketone compound containing vinyl polymers mixed with zinc oxide and bismuth phosphate.86 Diaket is a sealer that sets by chelation, but it contains polyvinyl chloride in polymer form as a main ingredient.101 It has a liquid component of B-diketone. It is a tacky material that contracts upon setting, but this is offset by its absorption of water.16 It has done well in in-vitro tests, including biocompatibility studies.101 Studies have shown that after initial mild tissue reactions, and after longer times of 2 weeks or more, there seems to be a decrease in tissue irritation.207-209 Orstavik and Mjor210 reported that Diaket demonstrated good biocompatibility compared with other sealers.
Eldeniz et al.211 evaluated the shear bond strength of three resin-based sealers (Diaket, AH Plus, and EndoREZ) to dentin with and without the smear layer. Bond strength of root canal sealers to dentin is an important property for the integrity of the sealing of root canals. A significant difference was found among the bond strength of the sealers, smear layer, and control groups. AH Plus sealer showed the highest bond strength in smear layer-free surfaces, and had the strongest bond to dentin with the smear layer intact.
Figure 11. AH Plus Root Canal Sealer by Tulsa Dentsply is a resin type sealer shown here in a mixing syringe. Reproduced with permission of Tulsa Dentsply.0
Glass Ionomer-Based Sealers
There are currently no glass ionomer sealers being marketed. Ketac-Endo (3M, Minneapolis, MN) is mentioned here because it appears in many studies as a comparative sealer.
Silicone-based sealers utilize the same qualities as caulking compounds used in household construction around kitchen and bathroom structures providing adhesion, a moisture-resistant seal, and stability.101
Lee Endo-Fill (Lee Pharmaceuticals, El Monte, CA) is an example of a silicone-based root canal sealer.
RoekoSeal (Roeko/Coltene/Whaledent, Langenau, Germany) is a polyvinylsiloxane that is a white paste-like sealer.212 RoekoSeal is reported to polymerize without shrinkage and utilizes platinum as a catalyzing agent.101
Wu et al.213 reported a 1-year follow-up study on leakage, using a fluid transport model, of single-cone fillings with RoekoRSA sealer. The apical filling in all roots did not show leakage either at 1 week or at 1 year.
GuttaFlow (Roeko/Coltene/Whaledent) is a polyvinylsiloxane with finely milled gutta-percha particles added to the RoekoSeal sealer. GuttaFlow also contains silicone oil, paraffin oil, platin catalyst, zirconium dioxide, nano-silver as a preservative, and a coloring agent. It is eugenol free. It is a cold flowable gutta-percha filling system for the obturation of root canals. GuttaFlow is triturated in its cannula and passively injected into the canal and then used with single or multiple gutta-percha points.
The use of chloroform or solvent-based sealers was popularized by Johnston and Callahan.214 The technique is still practiced today with various types of chloroform sealers, including chloropercha and Kloropercha N-O. Gutta-percha particles are added to the chloroform to produce a sealer, which has the same color as gutta-percha. The mixture can then be used as a sealer with gutta-percha points for obturation of the canal. There is more shrinkage with the chloroform solvent techniques, and this often translates into leakage, with the material pulling away from the canal walls as it shrinks creating voids through which leakage may occur.215
Chlororosin lateral condensation uses 5% to 8% rosin in chloroform, which leaves a very adhesive residue.
Chloropercha is white gutta-percha with chloroform and has no adhesive properties.
Kloropercha N-O contains additional resin, plus Canada balsam, that adds adhesive property to the material.
Urethane Methacrylate Sealers
EndoRez (Ultradent, South Jordon, UT) is a hydrophilic UDMA resin sealer that reportedly has good canal wetting and flow into dentinal tubules.212 The hydrophilic property improves its sealing abilities, if some moisture is still in the canal at obturation.101 EndoRez is introduced into the canal with a narrow 30-gauge Navitip needle (Ultradent). A single gutta-percha point technique or the lateral compaction obturation technique may be used.
EndoRez resin-coated gutta-percha is also marketed, which reportedly chemically bonds to the EndoRez sealer and works with all resin-based sealers. EndoRez points come in ISO standard sizes.
Tay et al.216 investigated the effectiveness of obturating root canals with the polybutadiene-diisocyanate-methacrylate resin-coated gutta-percha (EndoREZ). This enables the polyisoprene in the gutta-percha to chemically couple with the methacrylate-based resin sealer (EndoREZ). This study examined the effectiveness of using passively fitting resin-coated gutta-percha points with the dual-cured version of EndoREZ sealer. It was found that the hydrophilic nature of the sealer enabled the creation of an extensive network of 800 to 1200μm long sealer resin tags after removal of the endodontic smear layer. Still there were interfacial gaps and silver leakage could be observed along the sealer-dentin interfaces. This was primarily attributed to polymerization shrinkage of the sealer. Gaps and silver leakage was also seen between the resin-coated gutta-percha and the sealer.
The shear strength of EndoREZ to resin-coated gutta-percha was examined, and it was also examined whether shear strength is improved by creating an oxygen inhibition resin layer via the application of a dual-cured dentin adhesive to resin-coated gutta-percha.217 The authors concluded that in-situ dentin adhesive application may be valuable in enhancing the coupling of resin-coated gutta-percha to methacrylate sealers.
A study of bone response to the methacrylate-based sealer, EndoREZ, revealed, that at 10 days after placement, the amount of reactionary bone formation in direct contact with EndoREZ was significantly less than that observed with the controls, and the number of inflammatory cells next to the EndoREZ sealer was significantly higher than the controls. However, after 60 days, no differences were noted between the experimental and control groups. This indicated that the sealer produces a response similar to that of many sealers.218 Zmener et al.219 looked at the apical seal produced with the methacrylate-based sealer (EndoREZ) and Gross-man's sealer. Three groups were evaluated. The first combination of materials and techniques was a single gutta-percha point with the methacrylate sealer, the second was lateral compaction with the methacrylate sealer, and the third technique was gutta-percha with Gross-man's sealer. The results demonstrated that the dye penetration in the two methacrylate sealer groups occurred at the sealer-dentin or sealer-gutta-percha interface. In the Grossman's sealer group, the dye leakage occurred at both interfaces, and throughout the mass.
EZ Fill (Essential Dental Systems, South Hacken-sack, NJ) is a noneugenol epoxy resin sealer that is placed with a bidirectional spiral, rotating in a hand-piece, and used with a single gutta-percha point technique. The spiral is designed to spread the sealer laterally in the apical region of the canal. It is reportedly nonshrinking on setting and is hydrophobic in nature, making it resistant to fluid degradation. One study has shown EZ fill to seal as well as other techniques.220 Favorable clinical outcomes have also been reported.212,222
[Figure 12. Micrograph showing hybrid bond between MetaSEAL and gutta-percha by penetration of the gutta-percha.]
MetaSEAL (Parkell, Inc., Edgewood, NY) marketed in the United States and Canada is a thinner version of 4-Meta, used for years as a restorative sealer. Belli et al.223 compared MetaSEAL for leakage against Epiphany/Real Seal and AH Plus and found it to show significantly lower leakage after the first week. After 4 and 12 weeks, there was no significant difference among the groups. MetaSEAL's self-etching formula hybridizes the canal wall preventing leakage and bonds to gutta-percha (Figure 12) and Resilon.
Figure 12. Micrograph showing hybrid bond between MetaSEAL and gutta-percha by penetration of the gutta-percha. Courtesy, Parkell.0
Paraformaldehyde-Containing Sealers (Riebler's)
Reibler's paste is a paraformaldehyde-containing sealer and was discussed earlier under paraformaldehyde-containing paste materials.
Evaluation and Comparison of Sealers
Orstavik101,224 has listed the various evaluation parameters for testing endodontic sealers. They include technologic tests standardized by the ADA/ANSI in the United States, and the ISO internationally. These technologic tests include flow, working time, setting time, radiopacity, solubility and disintegration, and dimensional change following setting. Additionally, biologic tests, usage testing, and antibacterial testing are useful. Clinical testing should be included to establish outcomes of treatment.
The influence of root canal shape (curved or straight) on the sealing ability of sealers has been studied in a fluid transport model.225 Canals were laterally compacted with gutta-percha with either Pulp Canal Sealer or Sealapex sealer. It was found that Sealapex allowed more leakage than Pulp Canal Sealer at 1 year. The authors concluded that canal form affects sealing ability at 1 month, but the sealer affects the quality of seal at 1 year.
The sealing ability of four sealers was evaluated quantitatively by Cobankara et al.226 The sealers tested were Rocanal, a zinc oxide-eugenol powder-liquid system; AH Plus, an epoxy resin-based sealer; Sealapex, a calcium hydroxide-based sealer; and RC Sealer, an adhesive resin sealer. Apical leakage decreased gradually for all sealers from 7 to 21 days. Sealapex demonstrated better apical sealing than the other sealers, and AH Plus, RC Sealer, and Rocanal all showed similar apical leakage at every time period.
Another in vitro study evaluated the apical leakage, by a fluid filtration meter, of three root canal sealers, AH Plus, Diaket, and EndoREZ.227 Statistical analysis indicated that root canal fillings with Diaket in combination with the cold lateral compaction technique showed less apical leakage than the other two sealers.
Saleh et al.228 used the SEM and energy dispersive spectroscopy to evaluate the adhesion of sealers. The microscopic details of the debonded interfaces between endodontic sealers and dentin or gutta-percha were assessed in this study. Grossman's sealer, Apexit, Ketac-Endo, AH Plus, RoekoSeal Automix, and RoekoSeal Automix with an experimental primer were examined. After tensile bond strength testing, the morphologic aspects of the fractured surfaces were assessed. The energy-dispersive spectroscopy successfully traced sealer components to the debonded surfaces. Some of the sealers penetrated into the dentinal tubules when the dentin surface had been pretreated with acids. However, these sealer tags remained, occluding the tubules after bond failure in some instances only (Grossman's sealer, RoekoSeal Automix with an experimental primer, AH Plus/EDTA). Penetration of the endodontic sealers into the dentinal tubules, when the smear layer was removed, was not associated with higher bond strength.
Pommel et al.229 examined the efficacy of four types of sealers in obtaining an impervious apical seal, and to correlate those seals with their adhesive properties. Pulp Canal Sealer, Sealapex, AH 26, and Ketac-Endo were the sealers evaluated. The results showed that teeth filled with Sealapex displayed higher apical leakage than the other sealers. No statistically significant difference was found between AH 26, Pulp Canal Sealer, and Ketac-Endo. No correlation was found between the sealing efficiency of the four sealers and their adhesive properties.
Lee et al.230 investigated the adhesion of endodontic sealers to dentin and gutta-percha. The bond strength to the dentin of the four sealers gave the following order from lowest to highest: Kerr Sealer < Sealapex < Ketac-Endo < AH 26. The bond strengths to gutta-percha gave the following order from lowest to highest: Ketac-Endo < Sealapex < Kerr < AH 26. The bond between the Kerr Sealer and dentin all failed adhesively, whereas the Sealapex bonds failed cohesively (80%). AH 26 demonstrated no adhesive failures. The AH 26 gave the highest bond strength values to both dentin and gutta-percha. These finding suggest that the resin may not only react with the collagen to form bonds but react with gutta-percha as well.
In another study, Tagger et al.231 showed AH 26 had a significantly stronger bond to gutta-percha than the remaining five sealers, including Roth's 801 and Sealapex.
The cytotoxicity of RoekoSeal Automix and AH Plus was evaluated using human cervical carcinoma cells and mouse skin fibroblasts.232 AH Plus was significantly more cytotoxic for both cell lines after 1 hour, 24 hours, and 48 hours, compared with the 7-day and 1-month setting periods. RoekoSeal had no cytotoxic effects on either cell line at any setting time.
Spangberg and Pascon233 examined the cytotoxicity of seven endodontic sealers (Wach's, Grossman's, Tubli-Seal, AH 26, Nogenol, Diaket, and Endo-Fill). Evaluated as solid materials, Wach's Sealer, Grossman's Sealer, Tubli-Seal, and Diaket were the most toxic. Nogenol was less toxic and the least toxic materials were AH 26 and Lee Endo-Fill. When solubilized, however, Grossman's sealer, Tubli-Seal, and Endo-Fill had very low toxicity, Nogenol had low to medium toxicity, and AH 26, Diaket, and Wach's sealers were very toxic as liquids.
Economides et al.234 investigated the biocompatibility of four root canal sealers (AH 26, Roth's 811, CRCS, and Sealapex). Sealapex and Roth's 811 sealers caused moderate to severe inflammation reactions, whereas CRCS caused a mild to moderate reaction. AH 26 caused the greatest irritation initially, but this inflammatory reaction decreased with time.
Bernath and Szabo235 examined tissue reaction initiated by different sealers. The aim of this study was to analyze the tissue reactions of the calcium hydroxide sealer, Apexit, and to compare it with the reactions of sealers with different chemical compositions (Endomethasone, AH 26, and Grossman's sealer). When filled within the root, AH 26 and Endomethasone initiated a mild lymphocytic/plasmocytic reaction in some cases. In the group of overfilled canals, all four sealers initiated an inflammatory response: Endomethasone initiated a foreign body-type granulamatous reaction; AH 26 particles were engulfed by macrophages; Apexit and Gross-man's sealers initiated only a lymphocytic/plasmocytic reaction.
Huumonen and coworkers236 evaluated the healing of patients with apical periodontitis after endodontic treatment by comparing a silicone-based sealer (RoekoSeal Automix) and a zinc oxide-based sealer. After a 1-year follow-up, 199 teeth were assessed to evaluate their periapical status. The results of the study showed that there was no statistical difference between the success rates of the two study groups. The overall success rate at 12 months was 76%.
Orstavik224 rated the flow for Tubli-Seal to be greater than that of Kerr's PCS, which was better than Diaket and Kloroperka NO. He also stated that flow properties may be affected by changes in the powder-to-liquid ratio.
The rheologic properties of Apexit, Tubli-Seal EWT, Grossman's sealer, and Ketac-Endo were tested in a capillary system by Lacey and coworkers.237 Tubli-Seal EWT had a thinner film thickness than the other sealers. Tubli-Seal EWT had lower viscosity and better flow than the other sealers. Increased strain rate gave a significant increase in the flow rate of all sealers. The reduction in powder-to-liquid ratio for Grossman's sealer significantly increased flow in narrow tubes, and at a higher strain rate. Increasing the rate of insertion gave increased volumetric flow and therefore a reduced viscosity for all sealers. As the internal width of the canals was reduced, there was a reduction in volumetric flow and therefore an increased viscosity.
McMichen et al.238 did a comparative study of selected physical properties of five root canal sealers. This study sought to investigate the physical properties of five sealers: Roth's 801, Tubi-Seal EWT, AH Plus, Apexit, and Endion. Solubility in water, film thickness, flow, working time, and setting time were tested. AH Plus had the greatest stability in solution. But AH Plus also had the greatest film thickness. Flow rates were similar, and the working times for all were greater than 50 minutes. Setting time for Roth's 801 was 8 days.
Tagger et al.239 studied the interaction between sealers and gutta-percha cones. AH 26 silver-free had a notable softening effect on most gutta-percha brands, resulting in increased flow. Liquid (bisphenol epoxy resin) and chemical-bond formation could act as partial solvent effect of the resin. Eugenol has a solvent effect on gutta-percha. The combination of Apexit and UDM gutta-percha cones (United Dental Manufacturers, Zipperer, VDW, Munich, Germany) gave the greatest penetration in lateral canals. Understanding the interaction between gutta-percha and sealers may serve as a guide for using the most suitable combination for specific clinical cases. A tooth with a wide apical foramen should be filled with a combination that provides little flow; conversely, canals with very fine apical foramina and internal irregularities should be filled with a more fluid combination.
The setting time for 11 sealers was determined in both aerobic and anaerobic environments by Nielsen et al.240 Kerr Tubli-Seal and Ketac-Endo were the fastest sealers to set under aerobic environments, and Ketac-Endo and Resilon sealer (Epiphany) were the fastest sealers to set under anaerobic environments. Roth's 801 and Roth's 811 sealers were the slowest sealers to set under both aerobic and anaerobic environments, taking over 3 weeks to set. Resilon sealer (Epiphany) set in 30 minutes under anaerobic conditions, but in the presence of air, Resilon sealer (Epiphany) took a week to set, and an uncured layer remained on its surface.
Orstavik224 stated that the assessment of working time is preferably done with measurements of flow as a function of time. It is the time from the start of mixing to the point at which the flow has been reduced to 90% of the initial flow measurement. The working time for zinc oxide-eugenol sealers demonstrated an initial increase in flow, followed by a later reduction in flow.
The zinc oxide sealers and the calcium hydroxide sealers appear to have greater solubility than other sealers.197,241-243
Schafer and Zandbiglari244 studied the solubility of root canal sealers in water and artificial saliva. The sealers examined were (epoxy resin [AH 26, AH Plus], silicone [RSA RoekoSeal], calcium hydroxide [Apexit, Sealapex], zinc oxide-eugenol [Aptal-Harz], glass ionomer [Ketac-Endo], and a polyketone-based sealer [Diaket]). Most sealers were of low solubility, although Sealapex, Aptal-Harz, and Ketac-Endo showed a marked weight loss in all liquids. Even after 28 days of storage in water, AH 26, AH Plus, RSA RoekoSeal, and Diaket showed less than 3% weight loss. AH Plus showed the least weight loss of all sealers tested, independent of the solubility medium used. Sealapex, Aptal-Harz, and Ketac-Endo had a marked weight loss in all liquids.
DIMENSIONAL CHANGE FOLLOWING SETTING
Kazemi et al.245 examined the long-term comparison of the dimensional changes of four sealers, ZnOE, AH 26, Endo-Fill, and Endomethasone. The two zinc oxide and eugenol sealers started to shrink within hours after mixing. The first volumetric loss for AH 26 and Endo-Fill was recorded after 30 days. The least dimensional change at any time period was observed for Endo-Fill. Significant dimensional change and continued volume loss can occur in some endodontic sealers. The setting times for Endo-Fill, ZnOE, Endomethasone, and AH 26 were 2.5, 4, 9, and 12 hours, respectively. Endo-Fill and AH 26 had lower rates of solubility, water sorption, and dimensional change than ZnOE and Endomethasone over 180 days.
The in vitro antibacterial activity of Fill Canal (zinc oxide based sealer), Sealapex, Sealer 26, Apexit, and calcium hydroxide against various species of micro-organisms was studied.246 Fill Canal demonstrated large zones of inhibition against all bacteria tested. Sealer 26 was not effective against Porphyromonas endodontalis or Porhyromonas gingivalis. Sealapex and calcium hydroxide showed similar effects against the various bacteria, being effective against Actinomyces israelii, and Actinomyces naeslundii. Sealapex was not effective against Staphylococcus aureus, but calcium hydroxide was effective against Staphylococcus aureus. Apexit was not effective against any of the microorganisms tested.
An in vitro antibacterial activity study of four root canal sealers tested AH Plus, Endomethasone, Pulp Canal Sealer, and Vcanalare, a zinc oxide and orthophenylphenol containing sealer.247 All of the freshly mixed sealers showed complete inhibition of bacterial growth. Similar results were obtained after 24 hours, with the exception of AH Plus. Vcanalare was the only sealer still inhibiting bacterial growth 7 days after mixing.
The amount of bacterial endotoxin penetration through root canals obturated either with cold lateral compaction or with a continuous wave technique with backfill of thermoplasticized gutta-percha, with either Roth's 801 sealer or AH 26 sealer, was evaluated by Williamson et al.248 The groups differed significantly. Thermoplasticized gutta-percha with Roth's 801 sealer permitted the least amount of endotoxin penetration, suggesting that the Roth's 801 sealer may have a role in inhibiting endotoxin penetration into obturated root canals.
Siqueira and Goncalves249 found that zinc oxide-eugenol sealers inhibited all the bacteria tested in their study. Sealer 26, the epoxy resin containing calcium hydroxide, was inhibitory on most strains of bacteria tested, but not against Porphyromonas endodontalis and Porphyromonas gingivalis. Sealapex had low antibacterial activity.
Leonardo et al.250 examined the antimicrobial activity of four root canal sealers (AH plus, Sealapex, Ketac-Endo, and Fill Canal), two calcium hydroxide pastes (Calen and Calasept), and a zinc oxide paste against seven bacterial strains. All sealers and pastes presented in vitro antimicrobial activity for all bacterial strains after a 24-hour incubation period at 37°C.
Kayaoglu et al.251 tested short-term antibacterial activity of root canal sealers toward E. faecalis. E. faecalis suspensions were exposed to freshly mixed sealers (MCS [Medidenta International, Inc.], AH Plus, Grossman's, Sealapex, Apexit). MCS contains iodoform. MCS, AH Plus, and Grossman's sealer significantly reduced the number of viable bacteria in both tests. Sealapex and Apexit were not statistically different from the controls. MCS, AH Plus, and Grossman's sealer were effective in reducing the number of cultivable cells of E. faecalis. Calcium hydroxide-based sealers, Sealapex and Apexit, were ineffective in this short-term experiment.
The prevention of coronal bacterial leakage back into the root canal system is crucial for the ultimate success of endodontic therapy. Several studies have shown that leakage can occur through the obturated root canal system in a relatively short time period.252-255 The issue of coronal leakage and its effect on endodontic outcomes has been investigated. Whereas some authors feel that the quality of the endodontic obturation is a more important factor than the quality of the coronal restoration,256-258 others feel that preventing coronal microleakage can play a significant role in the success of endodontic therapy.259 In any event, the placement of another barrier to the penetration of microorganisms into the obturated root canal system would seem to prevent leakage due to delay in placement of a permanent restoration or leakage from failed or inadequate coronal restorations. Several studies have looked at materials that may be used as intraorifice barriers placed 1 to 2 mm into the orifice of canals, or on the pulpal floor, to add another layer to prevent micro-leakage.129,260-268
Yamauchi et al.,269 in a dog study, examined the effect of an orifice plug of 2 mm of IRM or a dentin bonding/composite resin on coronal leakage of teeth that had canals obturated with gutta-percha and the access cavities left open for 8 months. Periapical inflammation was observed in 89% of the group without plugs, but in those with composite plugs only 39% had periapical inflammation and only 38% in the IRM-plugged group.
An investigation, comparing Cavit, against a flowable light-cured composite resin (Tetric), and MTA (ProRoot) as intraorifice barriers at 1, 2, 3, or 4 mm in canals obturated with gutta-percha, demonstrated a better seal with the flowable composite than with either MTA or Cavit.270
Chailertvanitkul et al.261 investigated coronal bacterial leakage, through coronal access using Vitrebond (3M), a resin-modified glass ionomer liner, as a barrier on the pulpal floor. The teeth with the Vitrebond liner that had been placed on the pulpal floor showed no leakage of bacteria, whereas 60% of the specimens without a Vitrebond liner showed leakage after 60 days.
Wolcott et al.260 found that there was no significant difference between Vitrebond, a colored trial GC America glass ionomer, and Ketac-Bond. There was significantly less coronal leakage when the glass ionomers were used than when no barrier was placed.
Maloney et al.267 found that thermocycling Triage (GC America, Inc.), a colored resin-modified glass ionomer, had no effect on the seal produced by Triage, when it was used as an intraorifice barrier at depths of 1 or 2 mm. The 1 and 2 mm intracoronal barrier significantly reduced coronal microleakage compared with no barrier placement.
Mavec et al.271 investigated the use of a glass ionomer barrier against bacterial leakage a when post space is required. They found that a 1 mm barrier of glass ionomer over as little as 2 or 3 mm of gutta-percha could reduce the risk of recontamination of the apical gutta-percha. This could be beneficial in cases where there is a minimum amount of root length for a post.
Pisano et al.262 compared Cavit, IRM, and Super EBA as intraorifice barriers to prevent coronal microleakage and found that all three groups leaked less than those obturated canals that did not receive a barrier.
Wolanek et al.265 tested the effectiveness of a dentin-bonding agent used as an intraorifice barrier and found that it reduced coronal bacterial leakage.
Galvan et al.264 evaluated Amalgbond Plus, C&B Metabond, One-Step Adhesive with Eliteflo composite, One-Step Dentin Adhesive with Palfique composite, and IRM as intracoronal barriers. At 7 days, the IRM, AEliteflo, and Palfique composite leaked significantly more than Amalgabond or C&B Metabond. Amalgabond consistently produced the best seal through all time periods.
Temporary Filling Materials
The problem of coronal leakage is also important in the choice of an interim restoration material to seal off the access preparation, either between appointments or before the endodontically treated tooth receives a permanent restoration.
Cavit (ESPE, Seefeld, Germany), in a number of studies, has been found to prevent leakage, when used as a temporary filling material to close access preparations, either as an interim filling material or after final obturation before a permanent restoration is placed.272-280 Cavit is premixed and is easily introduced into the access cavity, as well as being easy to remove from the access cavity at the subsequent appointment. The ingredients in Cavit are zinc oxide, calcium sulfate, zinc sulfate, glycoacetate, polyvinyl-acetate resin, polyvinylchloride-acetate, triethanolamine, and red pigment.272 The calcium sulfate is hydrophilic and causes hydroscopic expansion of Cavit. This absorption of moisture and subsequent expansion cause Cavit to seal very well as it sets in a moist environment.
In a survey of Diplomates of the American Board of Endodontics, Vail and Steffel281 found that Cavit was the temporary restoration of choice for both anterior and posterior teeth.
Webber et al.282 found that to seal adequately, Cavit must have a depth of at least 3.5 mm.
The ability of Cavit to prevent bacterial penetration into root canals containing four medicaments was evaluated.283 The medicaments were calcium hydroxide, chlorhexidine, an antibiotic-corticoid compound (Ledermix), and chloromono-campherphenolic compound (ChKM). The authors found that Cavit prolonged the protection of all the medicaments from 13 to 18 days but that an adequate seal could not be provided for more than 1 month.
Balto274 assessed microbial leakage of three temporary filling materials (Cavit, IRM, and Dyract). IRM began to leak after 10 days, whereas Cavit and Dyract did not leak until after 2 weeks.
After 3 weeks, Beach et al.273 found that 4 of 14 TERM samples and 1 of 18 IRM samples leaked and showed positive bacterial growth. None of the Cavit samples in the study leaked. It was shown that Cavit provided a significantly better seal than the other temporary filling materials.
Kazemi and coworkers277 found that Tempit (Centrix, Milford, CT) and IRM (Dentsply International/L.D. Caulk Division, Milford, DE) seemed less appropriate as an interim endodontic restoration than Cavit based on an assessment of marginal stability and permeability to dye penetration.
IRM is a temporary filling material that comes in a liquid-powder form that requires mixing. It is a polymer-resin-reinforced zinc oxide-eugenol material. Although many studies show it has inferior sealing abilities compared with Cavit, in clinical situations, however, which require greater bulk and resistance to occlusal forces, IRM may be used as a temporary restorative material. Zinc oxide and eugenol materials, such as IRM, possess about double the compressive strength value of Cavit.284 Glass ionomer cements or composite resins may also be used in these situations and may have better sealing ability and greater compressive strength.
The antibacterial properties of several temporary filling materials were examined. Revoltek LC (GC Corporation, Tokyo, Japan), Tempit (Centrix), Systemp inlay (Vivadent, Schaan, Liechtenstein), and IRM were tested against Streptococcus mutans and E. faecalis. Systemp inlay exhibited antibacterial properties when in contact with S. mutans for at least 7 days, whereas Tempit and IRM sustained this ability for at least 14 days. When in contact with E. faecalis, Tempit and IRM were antibacterial immediately after setting, and IRM sustained this activity for at least 1 day.285
Zmener et al.286 found no statistically significant difference in the marginal leakage between Cavit, IRM, and Ultratemp Firm after thermocycling. All of the materials leaked at the interface of the material with the dentin, and some of the IRM specimens absorbed the dye into the bulk of the material.
Orahood et al.287 found there was no difference in marginal leakage between Cavit and ZOE when used to seal access preparations through either alloy or composite restorations. One study found IRM more watertight than Fermit-N or Cavit G intermediate restorative materials.288
TERM (Dentsply International/L.D. Caulk Division) is a composite resin interim restorative material for endodontics. It is a visible-light-cured resin containing UDMA polymers, inorganic radiopaque filler, pigments, and initiators.272
Seiler289 studied bacterial leakage of three glass ionomers, IRM, and Cavit as used as a temporary endodontic restorative material. Cavit provided a slightly better seal than IRM; however, the glass ionomer and resin-modified glass ionomer materials provided better seals against bacteria than either IRM or Cavit. If 3.5 mm of space does not exist for a temporary filling material, Hansen and Montgomery290 found that TERM may provide a superior temporary restoration. They found that TERM provides an adequate seal at 1, 2, 3, and 4 mm.
|Date: 13/06/2011 22:55|
Re: Root Canal Filling Materials
As new materials are introduced to fill the root canal system, it is important to remember Grossman's tenets and to remember the proven success of many of the materials currently in use. However, there still is a need to constantly improve what we can offer our patients, and to improve the outcome of endodontic treatment, in order to preserve the natural dentition. Long-term randomized clinical trials are needed on all the materials, new and time tested, which are used in modern-day endodontics.
With advances in materials and other aspects of endodontics, one cannot imagine materials that will be available to use in root canal systems in the future. They, no doubt, will be much more biocompatible and, one might hope, may promote regeneration of tissues within the tooth and bone.
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