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Date: 29/05/2011 20:21
Radiographic Interpretation
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Radiographic Interpretation - DAG ORSTAVIK, TORE ARNE LARHEIM

Image

Introduction


Radiographs are indispensable in most aspects of endodontic practice. They are important for diagnosis, treatment planning, monitoring details during treatment, control of details at conclusion of treatment, and for follow-up control of treatment outcome. The main focus in this chapter will be on interpretation of periapical radiographic images as intraoral films or digital counterparts, sensors, and image plates are the most frequently used means of radiographic examinations for endodontic diagnosis.


More sophisticated methods for radiographic diagnosis have become available, providing better details of normal and pathological structures with multiplanar imaging. Examples of such advanced imaging interpretation are also given, mainly in the section dealing with differential diagnosis.


Biological Processes Related to Radiographic Diagnosis


INTRODUCTION


It is basic knowledge that radiographic details portray variations in mineral density in tissues and that conventional film- or sensor-detected exposures are two-dimensional reflections of a three-dimensional reality. Normal anatomical structures are recognized by density variations in tooth and bone tissues. The interpretation is done by relating the radiographic signs to our mental image of what the three-dimensional image normally should look like, and how we perceive this to be projected to the film. With time and experience, we rely increasingly on how a given radiograph relates to other radiographs we have seen and learned to accept as normal or pathological structures.


Obviously, interpretation of even simple radiographic exposures is subject to a great deal of bias: the knowledge base of basic, three-dimensional anatomy will vary among observers, there is bias and variation in the learning process from peers et al., and we develop individual preferences in attaching importance to specific elements of the radiograph. As clinical and radiographic signs of endodontic disease often are small and rather unspecific, there is always pressure on the diagnostician to read as much as possible into small variations in radiographic appearance of tooth and periapical structures. This bias and individual variation in diagnosis of periapical disease by radiography was elegantly demonstrated by Goldman et al.1 and more scientifically by Reit and Grondahl.2


CARIES

In caries diagnosis, the endodontic dilemma is to determine the spatial relationship of the carious lesion to the pulp. On the one hand, we are conditioned to think that proximal caries goes deeper than what can be seen in the radiograph; on the other, caries located on the buccal or lingual aspect may project over the pulp and give the false impression of pulpal involvement. Interpretation of radiographic findings in crowned teeth represents special challenges.3


PULPAL CHANGES: CALCIFICATION, OBLITERATION, AND RESORPTION

Abnormal pulp calcification may be reactionary (tertiary) dentin to caries or trauma (operative procedures); degenerative localized or diffuse calcifications in the coronal and, characteristically, the radicular pulp; and pulp obliteration following traumas such as tooth concussion or luxation or intentional or necessary replantation.4-7


Internal resorptions are usually associated with the replacement of dentin by a soft tissue with resorbing cells causing a balloon-shaped lesion starting from the radicular pulp.8-12 The radiographic end result is a round or ovoid radiolucent area observed on the


[Figure 1. A, B, Internal resorption of left upper canine before and after endodontic treatment (Courtesy, Dr. Harald Prestegaard); C, Rare case of multiple resorptions (Courtesy, Dr. Elisabeth Samuelsen).]


radiograph (Figure 1). It is a characteristic radiographic sign that the internal pulpal wall is destroyed, whereas cementum and periodontium are not affected, at least not initially.


Figure 1. A, B, Internal resorption of left upper canine before and after endodontic treatment (Courtesy, Dr. Harald Prestegaard); C, Rare case of multiple resorptions (Courtesy, Dr. Elisabeth Samuelsen).0



PATHOLOGICAL REACTIONS OF TOOTH STRUCTURE: FRACTURE, RESORPTIVE PROCESSES

Fracture of a root can be difficult to diagnose but may result in reparative processes that become recognizable in later radiographs.13-16 Diagnosis of root fractures may be made easier by using multiple projections (Figure 2) or advanced radiographic techniques, particularly computed tomography (CT).14,16 There may be a hard tissue union of the two fragments if they are in close apposition to each other, the pulp is vital, and the fracture line is in its entirety within the periodontal ligament (PDL). Remodeling may then lead to a near normalization of the radiographic appearance of the root (Figure 3). In the case of fibrous repair, the fragments remain separated by a structure resembling periodontal membrane, and remodeling processes in the form of blunting of the fragment edges may become visible in the radiograph.


Resorptive processes of the tooth structure induce changes in radiographic structures that may be challenging both from a diagnostic and therapeutic point of view.17-20 Surface resorption and repair may be seen as the body's way of coping with damage to the cementum, and these processes are sometimes extensive enough to be detectable radiographically. In cases of trauma with pulp damage, it then becomes a diagnostic challenge to differentiate resorption and repair from progressive inflammatory resorption, which, when uncontrolled, will lead to rapid loss of tooth substance.


Cervical root resorption21 attacks dentin from pinpoint openings in cementum at the bottom of the gingival pocket and progresses either in irregular pathways in all directions into dentin or as semilunar, distinct caries- or erosion-like lesions (Figure 4), sometimes in multiple locations. As the process tends to halt when the inner dentin and predentin


[Figure 2. Root fracture examined two days after trauma. A, Uncertain diagnosis on the periapical radiograph. B, C, D, Fracture is evident when multiple projections are obtained.]


[Figure 3. A, Tooth remodeling of fragments after healing of horizontal root fracture. B, Blunting of edges shown in insert with artificially increased contrast.]


are reached, radiographically the lesions are often characterized by an outline of the pulp space appearing through the radiolucent area caused by the resorption (Figure 5).


Figure 2. Root fracture examined two days after trauma. A, Uncertain diagnosis on the periapical radiograph. B, C, D, Fracture is evident when multiple projections are obtained.0

Figure 3. A, Tooth remodeling of fragments after healing of horizontal root fracture. B, Blunting of edges shown in insert with artificially increased contrast.0

Figure 4. Cervical root resorption; erosive type.0

Figure 5. Cervical root resorption progressing apically with characteristic outline of pulp chamber clearly visible (Courtesy, Dr. Nabeel Mekhlif).0



PERIAPICAL CHANGES: WIDTH OF PERIODONTAL LIGAMENT, BONE TEXTURE CHANGES, DEMINERALIZATION, BONE FORMATION, APICAL SURGERY

Apical root resorption, bone resorption, cementum formation, and bone deposition are the biological processes primarily associated with radiographic changes in the periapical area. Furthermore, there are often structural changes in the periapical bone reflecting either increased density of bone (condensing apical osteitis)22,23 or altered organization of trabeculae (incipient apical osteitis) (Figure 6).


Resorption/remodeling of the apical lamina dura and a widening of the periodontal ligament may occur as an early or limited response to infection in the root canal system, but is also common as a consequence of increased tooth mobility, as in marginal periodontal inflammation or during orthodontic tooth movement. In the latter case, apical root resorption and remodeling of the root apex may be very extensive (Figure 7).


[Figure 4. Cervical root resorption; erosive type.]


Apical periodontitis leads to demineralization of periapical bone with subsequent lesion development. Preceded by structural changes in the bone, this lesion may be evident in radiographs before overt demineralization has begun in the area.


Apical periodontitis (granuloma, radicular cyst) develops with variable speed, and the effects on the surrounding bone will also vary. Bone deposition with the formation of a distinct bony rim may occur, which has been associated with stable lesions more likely to have cyst formation; however, there is little evidence to support this concept.24,25 On the other hand, cyst formation is more likely to be found in large lesions compared to small.26 Histological studies have indicated that in lesions with acute characteristics there are changes in bone structure peripherally to the outer margin of the lesion proper.27


Surgical endodontic or other periapical procedures leave a blood clot that organizes and eventually heals by formation of cortical and medullary bone. This healing process is faster than healing of apical lesions after conservative endodontic therapy,28 and leads to


[Figure 5. Cervical root resorption progressing apically with characteristic outline of pulp chamber clearly visible]


radiographic signs that may differ from normal periapical structures, particularly if scar tissue with reduced mineral content is formed.29,30


Figure 6. Condensing apical periodontitis at distal root, incipient apical periodontitis at mesial root of mandibular first right molar. Note foreign material in pulp chamber, a likely cause of chronic pulpitis or pulp necrosis.0

Figure 7. A, Periapical radiographs of maxillary premolar made before orthodontic treatment, B, at 5.2 months and C, 11.9 months after bracket placement, and D, at end of 22.1 months of orthodontic treatment. Projections A, C and D are reconstructed according to projection B. Note apical root resorption of 2.6mm at 5.2 months B, of 5.1mm at 11.9 months C, and of 7.0mm at end of treatment D. (Modified with permission from Artun J, Van't Hullenar R., Doppel D., Kuijpers-Jagtman A.M. Identification of orthodontic patients at risk of severe apical root resorption. Am J Orthod Dentofacial Orthop 2007; 132:in press.)0



OTHER ENDODONTIC APPLICATIONS OF PERIAPICAL RADIOLOGY

There are several situations and cases where other aspects of endodontic treatment are detected and monitored by radiographs. Examples are iatrogenic mishaps such as root perforations and overfillings, root fractures and special procedures such as root resection and hemisection.


Periapical Diagnosis


Apical periodontitis is typically a droplet-shaped radiolucent area associated with the root apex surrounded by bone in continuity with the lamina dura at some distance from the pulpal exit.31 Being dependent on the egress of infectious material through the apical pulp orifice, lesions of apical periodontitis may be situated in lateral or furcal locations in association with lateral or furcal accessory canals, respectively.


[Figure 6. Condensing apical periodontitis at distal root, incipient apical periodontitis at mesial root of mandibular first right molar. Note foreign material in pulp chamber, a likely cause of chronic pulpitis or pulp necrosis.]


Apical periodontitis is a defense mechanism against infection. When apical cementum and dentin are invaded by microbes, the structures are attacked by resorbing cells, and root resorption, albeit limited, is integral to lesion development.32,33 The development of a granuloma and/or a cyst may be seen as the mobilization of an area where host defense mechanisms are concentrated, and the resorption of bone is a process necessary to provide space for the defending tissues.34 The granuloma/cyst is also protecting from direct infection of the bone marrow (osteomyelitis). While the granuloma/cyst is defined to a degree by the relative resistance of the bone, it occupies a place that is effective for the mobilization of a host defense, and cortical bone may be eroded for this purpose even if the path of least resistance would have pointed in another direction.


As the cortex makes up a very large percentage of the bone mass in the radiograph of a normal periapical area,35 the proposition has been made that involvement of cortical bone loss is necessary for detection of a lesion in a radiograph. While it is a matter of course that any lesion involving the cortex is more easily detectable,36,37 research has documented that the changes induced by resorptions and changes in the medullary and subcortical, trabecular bone can also be seen.37,38


[Figure 7. A, Periapical radiographs of maxillary premolar made before orthodontic treatment, B, at 5.2 months and C, 11.9 months after bracket placement, and D, at end of 22.1 months of orthodontic treatment. Projections A, C and D are reconstructed according to projection B. Note apical root resorption of 2.6mm at 5.2 months B, of 5.1mm at 11.9 months C, and of 7.0mm at end of treatment D.]


Radiographic signs must be correlated with macroscopic or microscopic anatomical and pathological features. Several studies have compared the radiographic and histological appearance of apical periodontitis, of which Brynolf's27 is by far the most extensive and detailed. Table 1 lists some of her findings that relate radiographic signs to histological characteristics of periapical inflammation.


There are few things easier than the radiographic diagnosis of a well-established, chronic apical periodontitis. Two particular radiographic aspects of apical periodontitis, however, may be difficult and frustrating: the detection of incipient changes and the monitoring of healing or post-treatment development of disease.


Advanced Multiplanar Imaging


Advanced imaging of the periapical area usually means section imaging. With computer technology it is possible to obtain an image of virtually any plane through a structure, greatly improving the diagnostic information of its three-dimensional morphology. However, the interpretation of multiple sections versus one projectional radiographic image is challenging and may require collaboration between specialists in endodontics and oral and maxillofacial radiology as given in the following paragraphs.


Advanced imaging, in particular CT, may be used supplementary to conventional periapical radiography for demonstration of complex anatomy of the root and surrounding structures, including associated lesions (Figure 8). With the development of cone beam CT, the root and periapical bone can be examined in axial, coronal, and sagittal sections with less patient exposure than with conventional CT to evaluate, for instance, the integrity of the cortical bone (Figure 9).


[Table 1. Histological and Radiographic Correlates]


[Figure 8. Molar with one canal in the mesiobuccal root unfilled and with apical periodontitis. A, B, C, Unfilled root canal is not seen on periapical or panoramic radiographs. D, E, F, G, Unfilled root canal and apical periodontitis seen on CT scans. H, I, Clinical photos confirm two root canals in the mesiobuccal root (of which only the most buccal was found to be root filled). (H, I, Courtesy, Dr. Homan Zandi)]


[Figure 9. Cone beam CT. B, axial, C, coronal, D, sagital sections. Root filled distal root with normal periapical structure and apical periodontitis associated with unfilled mesial root with destroyed buccal cortex. The different image planes are illustrated in A.]


Figure 8. Molar with one canal in the mesiobuccal root unfilled and with apical periodontitis. A, B, C, Unfilled root canal is not seen on periapical or panoramic radiographs. D, E, F, G, Unfilled root canal and apical periodontitis seen on CT scans. H, I, Clinical photos confirm two root canals in the mesiobuccal root (of which only the most buccal was found to be root filled). (H, I, Courtesy, Dr. Homan Zandi)0

Figure 9. Cone beam CT. B, axial, C, coronal, D, sagital sections. Root filled distal root with normal periapical structure and apical periodontitis associated with unfilled mesial root with destroyed buccal cortex. The different image planes are illustrated in A. (Courtesy, Dr. K. Honda.)0



Problems and Potentials of Periapical Radiographic Diagnosis and Follow-up of Apical Periodontitis


INCIPIENT CHANGES

Based on a concept of apical periodontitis (granuloma, cyst) formation as an expanding balloon starting at the apical orifice of the pulp, it has been held that the first sign of disease can be recognized as a widened periodontal ligament. Brynolf's27 and later studies39,40 have documented that this is a poor indicator of disease development. Rather, it may reflect increased tooth mobility or a limited tissue reaction to root filling surplus, or traumatic occlusion. Initial or limited inflammatory processes in relation to root canal infection can be detected by changes in the bone structure periapically rather than by overt demineralization.27 While it may be possible through extensive training to obtain proficiency in observing these changes,41 it should probably be accepted that such initial changes cannot reliably be diagnosed by conventional radiographic methods. In keeping with standard procedures for diagnosing disease in clinical practice and epidemiological studies, a high threshold should be set to exclude weak radiographic signs.


HEALING OF APICAL PERIODONTITIS

The biological dynamics of healing apical periodontitis are rarely studied and therefore not well known. It is a slow process,28 probably because of the resistance to resorption/replacement of the tissue components of cysts and, particularly, granulomas. By quantitative analyses of radiographs, healing may be seen as early as 3 months after therapy,42,43 and by 1 year, almost all cases that will eventually heal completely, show unequivocal, radiographic signs of healing44 (Figure 10). But healing processes that were not in evidence for as long as 10 to 17 years after treatment can be activated later to re-establish normal radiographic structures.45


Figure 10. A, B, C, Complete healing of apical periodontitis within 17 months of treatment.0.015625



ANATOMICAL LIMITATIONS

Normal anatomical structures and their variable location, size, and characteristics in different individuals, interfere with the interpretation of the periapical tissue responses in endodontic diagnosis. It is not simple in individual cases to account for variations of this kind; for example, while the alveolar bone surrounding roots of mandibular second and third molars is often free of confounding anatomical structures and thus should lead to an unquestionable diagnosis of periapical changes, the variations in trabecular pattern in this area is a frequent source of misdiagnosis of apical lesions that do not actually exist.


[Figure 10. A, B, C, Complete healing of apical periodontitis within 17 months of treatment.]


[Figure 11. Idiopathic osteosclerosis. A, Closely located to the apex of a vital tooth. B, Separated from the apex of a tooth with vital pulp.]


Figure 11. Idiopathic osteosclerosis. A, Closely located to the apex of a vital tooth. B, Separated from the apex of a tooth with vital pulp.0



DIFFERENTIAL DIAGNOSIS

Although conventional periapical radiography will be sufficient for differential diagnostic radiographic evaluation in most cases, the usefulness of advanced imaging is evident in the examination of a number of conditions, particularly when more serious disease is suspected.46


Hypercementosis may occur in response to pulpal inflammation without infection in the apical part of the canal. While the pulpitis usually requires endodontic treatment, the cementum deposited is not remodeled and will persist after endodontic treatment. Condensing apical osteitis is also associated with chronic pulpitis and will resolve following adequate therapy. It is the bone structure that is altered, and remodeling is possible and likely, although areas of persistent condensed bone may be seen in apposition to apparently adequately treated teeth. Idiopathic osteosclerosis may be a differential diagnostic problem if located close to the apices (Figure 11). Marginal periodontitis may show radiographic features similar to apical periodontitis, and when presenting with a necrotic and infected pulp may need combined treatment (Figure 12). Root fractures may indeed be seen as a variant of apical periodontitis; if the pulp canal space and the fracture slit are infected, this will result in a periodontitis where the fracture communicates with the periodontal space (Figure 13). The radiographic signs are somewhat characteristic in the case of vertical fractures, in that the whole length of the root may be affected, producing a diffuse halo of radiolucent bone around the root (Figure 14). Similarly,


[Figure 12. A, Typical endodontic-periodontal lesion. B, Healing 10 months after endodontic treatment.]


[Figure 13. Oblique-vertical root fracture with laterally widened periodontal ligament due to infection.]


[Figure 14. Vertical root fracture with bone resorption along the entire length of the mesial root.]


[Figure 15. Osteomyelitis with fistula formation and sequestration. A, B, Destructive foci, apparently with normal bone structures in between. C, D, Apical periodontitis with sequester and gutta-percha point in sinus tract.]


osteomyelitis may follow an initial root canal infection that for some reason has escaped the protective functions of the cyst or granuloma and invaded the bone marrow spaces (Figures 15, 16). Osteomyelitis characteristically may show sequestration and apparently normal bone structures between areas of bone destruction (see Figure 15). Another characteristic feature is periosteal bone formation that in young patients may become extensive (Figures 16, 17). In patients with irradiated mandibles, osteoradionecrosis may develop


[Figure 16. Osteomyelitis in 12-year old patient with extensive periosteal reaction. A, Apical periodontitis associated with both molars with necrotic pulps in left mandible and onion-peel bone formation of the lower mandibular border. B, C, One year later extensive bone formation is evident (arrow). D, Two years after baseline new bone destruction because of increased disease activity is clearly seen (arrow).]


[Figure 17. Proliferative periostitis of Garre. A, Clinical photo of 8-year-old boy with swelling associated with the left mandible (arrow). B, Occlusal radiograph shows classic onion skin osseous expansion around the mesial root of the first molar. C, Periapical radiograph shows a large lesion associated with the mesial root of the molar. D, Occlusal view 5 months after endodontic treatment; note significant reduction in swelling. E, Periapical radiograph taken 1 year after treatment; note resolution of apical lesion. F, Occlusal view 1 year later; note resolution of osseous expansion.]


that is indistinguishable from osteomyelitis, although usually with less prominent periosteal reaction (Figure 18). This may occur even many years after the radiation therapy of the malignancy. Bisphosphonate-related osteonecrosis of the jaws with a similar radiographic picture has been reported to occur with increasing frequency.47


The inflammatory paradental cyst is a rare entity, occurring exclusively in the mandibular molar area, and should not cause major difficulties in differentiation from apical periodontitis.48 However, the cyst may be projected over the apex on a conventional radiograph, making advanced imaging a valuable supplement for diagnosis (Figure 19). The lateral periodontal cyst is a developmental cyst occurring primarily in the premolar area of the mandible and may be difficult to distinguish radiographically from apical periodontitis.49 It can also occur in the maxilla, and when


[Figure 18. Osteoradionecrosis two years after radiation therapy and surgery of malignancy in maxilla. A, B, Extensive bilateral bone destruction with sequestration (arrows).]


[Figure 19. Paradental cyst. A, Apical radiolucency of first mandibular molar (Arrow). B, C, Buccal radiolucency with marginal communication, typically of a buccally infected paradental cyst.]


[Figure 20. Lateral periodontal cyst. A, Occlusal view shows apical radiolucency (arrow). B, CT scan shows cyst not connected to the tooth (arrow).]


projected over the apex on a conventional radiograph, supplementary advanced imaging may add decisive diagnostic information (Figure 20). The non-odontogenic incisive canal developmental cyst is located centrally between the maxillary incisors and may be easily mistaken for apical periodontitis if projected over the apex. An axial view may be helpful to identify the cyst in a palatal position in the jaw (Figure 21). A normal apical periodontium and pulp sensitivity will rule out apical periodontitis in such cases. The simple bone cyst (traumatic bone cyst) is not a true cyst but an empty hole in the jaw bone without epithelial coverage and of unknown origin, usually found in young individuals (Figure 22). Osseous (cemental) dysplasia may completely mimic almost any phase, productive or resorptive, of chronic apical periodontitis. The condition may be


[Figure 21. Incisive canal cyst. A, B, C, Occlusal view and conventional periapical radiographs show the cyst palatally located to the incisors.]


[Figure 22. Simple bone cyst. Periapical radiograph showing radiolucency between first and second molars. There was no expansion of the mandible.]


[Figure 23. Osseous (cemental) dysplasia. Apical radiolucencies (early stage dysplasia) around apices of three incisors.]


multiple and is predominantly found in the incisal region of the lower jaw (Figure 23). It is characteristic of most of the conditions mentioned in this paragraph that the pulps are vital and there are no clinical symptoms The giant cell granuloma is another lesion that usually presents as a large, sometimes multilocular, radiolucent area. It may also be more unilocular (Figures 24, 25), like eosino-philic granuloma, and sometimes give radiographic signs not unlike apical periodontitis. The value of advanced imaging is clearly demonstrated with the case of giant cell granuloma; it could be determined


[Figure 24. Giant cell granuloma mimicking apical periodontitis.]


[Figure 25. Giant cell granuloma. A, B, C, Unilocular radiolucency with displacement of two incisors; D, CT scan shows severe expansion buccally without corticated outline (arrow); E, F, MR imaging scans before E and after F intravenous contrast injection show contrast enhancement of entire lesion, consistent with solid tumor (arrow).]


[Figure 26. Primary hyperparathyreoidism. Defects in dentin structure and wide pulp chambers and root canals make the pulp tissue highly susceptible to damage and infection.]


before surgery and histology that the lesion was solid and not cystic when supplementary magnetic resonance imaging was performed (see Figure 25).


Hyperparathyroidism (Figure 26) is a systemic condition predisposing for pulpal and periapical infections.


Tumors of the jaw present radiolucencies that sometimes may mimic apical periodontitis. Pulp sensitivity will normally rule out apical periodontitis. The odontogenic keratocyst (keratocystic odontogenic tumor) and the ameloblastoma may appear close to root apices in singlelobular or multilobular forms, the latter tumor frequently demonstrates evident root resorption (Figure 27). A case of ameloblastoma, seen as a unilocular radiolucency on a conventional radiograph, proved to be multicystic with advanced imaging (Figure 28). Ossifying fibroma may also simulate apical periodontitis


[Figure 27. Ameloblastoma, multicystic/solid type. A, B, Multilocular radiolucencies with evident root resorptions (arrow). C, CT scan shows severe bone destruction and evident buccal expansion with destroyed lingual cortical bone (arrow).]


[Figure 28. Ameloblastoma, desmoplastic type. A, B, C, D, Apical unilocular radiolucency in the premolar region (arrow). Note also idiopatic osteosclerosis (arrow head). E, CT scan shows multilocular radiolucences (arrow) and sclerosis (arrow head). C, CT scan shows evident destruction including buccal cortex (arrow).]


(Figure 29), but unlike the other conditions mentioned (except cemental dysplasia), it also produces bone giving a mixed radiographic appearance.50


Malignant tumors in the jaws are rare but may cause severe bone destruction, and displace, but rarely resorb, adjoining teeth; floating teeth are more typical.46 A case of metastatic breast carcinoma in the mandible is shown in Figure 30, detected when the patient had a postoperative follow-up after apicoectomy.


Figure 12. A, Typical endodontic-periodontal lesion. B, Healing 10 months after endodontic treatment. (Courtesy, Dr. Birte N. Myrvang)0

Figure 13. Oblique-vertical root fracture with laterally widened periodontal ligament due to infection.0

Figure 14. Vertical root fracture with bone resorption along the entire length of the mesial root.0

Figure 15. Osteomyelitis with fistula formation and sequestration. A, B, Destructive foci, apparently with normal bone structures in between. C, D, Apical periodontitis with sequester and gutta-percha point in sinus tract.0

Figure 16. Osteomyelitis in 12-year old patient with extensive periosteal reaction. A, Apical periodontitis associated with both molars with necrotic pulps in left mandible and onion-peel bone formation of the lower mandibular border. B, C, One year later extensive bone formation is evident (arrow). D, Two years after baseline new bone destruction because of increased disease activity is clearly seen (arrow). (Reproduced with permission from Larheim, T.A., Westesson, P.-L. Maxillofacial Imaging, Springer 2006.)0

Figure 17. Proliferative periostitis of Garre. A, Clinical photo of 8-year-old boy with swelling associated with the left mandible (arrow). B, Occlusal radiograph shows classic onion skin osseous expansion around the mesial root of the first molar. C, Periapical radiograph shows a large lesion associated with the mesial root of the molar. D, Occlusal view 5 months after endodontic treatment; note significant reduction in swelling. E, Periapical radiograph taken 1 year after treatment; note resolution of apical lesion. F, Occlusal view 1 year later; note resolution of osseous expansion. (Reproduced with permission from Jacobson H.L.J., Baumgartner J.C., Marshall J.G., Beeler W.J. Proliferative periostitis of Garre: Report of a case. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2002;94:111-14.)0

Figure 18. Osteoradionecrosis two years after radiation therapy and surgery of malignancy in maxilla. A, B, Extensive bilateral bone destruction with sequestration (arrows). (Reproduced with permission from Larheim, T.A., Westesson, P.-L. Maxillofacial Imaging, Springer 2006.)0

Figure 19. Paradental cyst. A, Apical radiolucency of first mandibular molar (Arrow). B, C, Buccal radiolucency with marginal communication, typically of a buccally infected paradental cyst.0

Figure 20. Lateral periodontal cyst. A, Occlusal view shows apical radiolucency (arrow). B, CT scan shows cyst not connected to the tooth (arrow). (Reproduced with permission from Larheim, T.A., Westesson, P.-L. Maxillofacial Imaging, Springer 2006.)0

Figure 21. Incisive canal cyst. A, B, C, Occlusal view and conventional periapical radiographs show the cyst palatally located to the incisors.0

Figure 22. Simple bone cyst. Periapical radiograph showing radiolucency between first and second molars. There was no expansion of the mandible.0

Figure 23. Osseous (cemental) dysplasia. Apical radiolucencies (early stage dysplasia) around apices of three incisors.0

Figure 24. Giant cell granuloma mimicking apical periodontitis.0

Figure 25. Giant cell granuloma. A, B, C, Unilocular radiolucency with displacement of two incisors; D, CT scan shows severe expansion buccally without corticated outline (arrow); E, F, MR imaging scans before E and after F intravenous contrast injection show contrast enhancement of entire lesion, consistent with solid tumor (arrow). (Reproduced with permission from Larheim, T.A., Westesson, P.-L. Maxillofacial Imaging, Springer 2006.)0

Figure 26. Primary hyperparathyreoidism. Defects in dentin structure and wide pulp chambers and root canals make the pulp tissue highly susceptible to damage and infection.0

Figure 27. Ameloblastoma, multicystic/solid type. A, B, Multilocular radiolucencies with evident root resorptions (arrow). C, CT scan shows severe bone destruction and evident buccal expansion with destroyed lingual cortical bone (arrow). (Reproduced with permission from Larheim, T.A., Westesson, P.-L. Maxillofacial Imaging, Springer 2006.)0

Figure 28. Ameloblastoma, desmoplastic type. A, B, C, D, Apical unilocular radiolucency in the premolar region (arrow). Note also idiopatic osteosclerosis (arrow head). E, CT scan shows multilocular radiolucences (arrow) and sclerosis (arrow head). C, CT scan shows evident destruction including buccal cortex (arrow). (Reproduced with permission from Larheim, T.A., Westesson, P.-L. Maxillofacial Imaging, Springer 2006.)0

Figure 29. Ossifying fibroma. A, Apical radiolucency (and pulp sensitivity). B, 2.5 years later a mixed lesion was found including second molar. (Reproduced with permission from Mork Knutsen B., Larheim T.A., Johannessen S., Hillestad J., Solheim T., Stromme Koppang H. Recurrent conventional cemento-ossifying fibroma of the mandible. Dentomaxillofac Radiol 2002; 31:65-8.)0

Figure 30. Metastasis to the mandible from breast cancer. A, Periapical radiolucency after apicectomy of premolar in left mandible. B, C, D, CT scans show the postoperative defect and otherwise normal bone. E, Healed surgical defect, but new radiolucency had developed one year and 4 months later. F, G, H, CT scans confirm healed area and bone destruction including buccal cortex.0



Periapical Radiographs in Clinical and Epidemiological Endodontic Research


INTRODUCTION


Clinical radiographic research in endodontics is primarily concerned with apical periodontitis: its emergence following pulp extirpation or its healing after root canal treatment of infected teeth.


SPECIFICITY AND SENSITIVITY, REPRODUCIBILITY

Any system for registering disease must address the issue of specificity and sensitivity: how specific is a given criterion for the disease in question (i.e., how often will the diagnosis be wrong) and how quickly/early the criterion can be detected (i.e., how sensitive is the sign). From the discussions above, it is apparent that initial signs of apical periodontitis in radiographs may be of low specificity (widened periodontal ligament (PDL) reflecting increased mobility rather than disease), and increasing the sensitivity may come at the expense of specificity in registering initial disease. Also with reference to the discussion above, the personal bias in interpreting radiographs makes it imperative that for research purposes, harmonization and calibration of observers, while difficult, is carried out.


SUCCESS AND FAILURE

Endodontic treatment is performed under conditions with a theoretical potential for complete asepsis or effective antisepsis. This leads to a concept of a potential also for absolute "success" (complete elimination of infection) or "failure" (residual, recurrent or de novo infection). Complete radiographic maintenance or reestablishment of normal periapical structures have thus been defined as "success," whereas persistence or emergence of radiographic signs of disease is termed "failure."51 The concept is simple


[Figure 29. Ossifying fibroma. A, Apical radiolucency (and pulp sensitivity). B, 2.5 years later a mixed lesion was found including second molar.]


and easily understandable to patient, clinician, and researcher and has been widely used for assessments of treatment outcome (for review see refs 52, 53). However, the bias and variation in observers' perceptions of what constitutes success or failure has made comparisons among studies with different observers problematic.


PROBABILITY ASSESSMENTS

Acknowledging the bias and difficulties in calibration, Reit and Grondahl54 and Zakariasen et al.55 applied a probability scoring system for monitoring apical disease: the observers were assigned to assess the probability that disease be present on a 5- or 6-point scale. The system provides numerical data amenable to more sophisticated analyses than the dichotomous scoring, but it does in no way address the problem of harmonization of observers.


THE PERIAPICAL INDEX SCORING SYSTEM

This was developed56 for two reasons: to integrate radiographic score with histological characteristics of the disease and to make possible harmonization of observers across studies and geographical distance. The histological reference was to the studies by Brynolf,27 by adoption of her findings with a degree of simplification deemed necessary for calibration of scorers (Figure 31). Bias was reduced by making scoring a visual exercise rather than relying on verbal descriptors in characterization of radiographic findings and controlled by providing a


[Figure 30. Metastasis to the mandible from breast cancer. A, Periapical radiolucency after apicectomy of premolar in left mandible. B, C, D, CT scans show the postoperative defect and otherwise normal bone. E, Healed surgical defect, but new radiolucency had developed one year and 4 months later. F, G, H, CT scans confirm healed area and bone destruction including buccal cortex.]


[Figure 31. The periapical index scoring system.]


[Figure 32. Periapical index scores used to monitor and compare healing of teeth with apical periodontitis with and without cultivable bacteria at the filling session. Average change in PAI score from baseline at 4, 12, 26 and 52 weeks used as indicator of healing]


calibration kit with precise measurement of a given observer's performance in relation to a set of "true" scores. The system has been applied to more than 30 peer-reviewed publications since 2001, from Canada to China, with applications typically in endodontic epidemiology57 and clinical, follow-up studies58 (Figures 32, 33).


Figure 31. The periapical index scoring system. (Reproduced with permission from Orstavik D., Kerekes K., Eriksen H.M. The periapical index: a scoring system for radiographic assessment of apical periodontitis. Endod Dent Traumatol 1986;2:20-34.)0

Figure 32. Periapical index scores used to monitor and compare healing of teeth with apical periodontitis with and without cultivable bacteria at the filling session. Average change in PAI score from baseline at 4, 12, 26 and 52 weeks used as indicator of healing (Data from Waltimo T., Trope M., Haapasalo M., Orstavik D. Clinical efficacy of treatment procedures in endodontic infection control and one year follow-up of periapical healing. J Endod 2005;31:863-6.)0

Figure 33. Periapical index scores used to monitor healing in a group of teeth treated for apical periodontitis (Data from Sathorn C., Parashos P., Messer H.H. Effectiveness of single- versus multiple-visit endodontic treatment of teeth with apical periodontitis: a systematic review and meta-analysis. Int Endod J 2005;38:347-55.)0



DIGITAL QUANTIFICATION OF RADIOGRAPHIC DATA

Using direct digital or digitized, conventional radiographs, the numerical information in the acquired image may be used for quantitative assessment of grey level/mineral content changes. Digital subtraction is one attractive option for this purpose, but despite several attempts to apply this procedure to endodontic, periapical radiographs,42,59 this has not been successful. A method whereby lesion grey levels are related to a peripheral area in the same jaw, unaffected by pathological or healing processes in the bone, has proven more robust and found application in quantitative studies42,60-63 (Table 2) (Figure 34).


[Figure 33. Periapical index scores used to monitor healing in a group of teeth treated for apical periodontitis]


[Table 2. Application of the Ratio Method in Evaluation of Healing After Treatment of Apical Periodontitis with Three Modalities]


[Figure 34. Delineation of areas to be monitored during healing. AP, lesion as outlined at start, N, peripheral, stable normal bone]


Figure 34. Delineation of areas to be monitored during healing. AP, lesion as outlined at start, N, peripheral, stable normal bone (Modified from Orstavik D., Farrants G., Wahl T., Kerekes K. Image analysis of endodontic radiographs: digital subtraction and quantitative densitometry. Endod Dent Traumatol 1990;6:6-11.)0.015625



APPLICATIONS TO CLINICAL RESEARCH

New procedures, materials, and medicaments keep emerging for use in endodontics with claims of superior performance. While many such products and methods may be evaluated for their feasibility by in vitro technological and biological tests, true progress in treatment outcome can only be measured in controlled, follow-up studies with randomized design and in comparison with conventional methods of reference. Very few such studies have been performed and that is reflected in the scarcity of solid data at the higher levels of evidence found when endodontic treatment is studied in systematic reviews and meta-analyses.52,64-67 Extensive, at times costly, randomized clinical trials are necessary for documentation of performance, and it is unfortunate that many new techniques and products do not have such data available.


The Periapical Index (PAI) scoring system has been used in several studies with randomization of techniques and has proven useful for strict comparisons of, particularly, root filling materials68,69 (see Figure 34), but also for comparison of treatment methods.70 Similarly, digital analyses have been used successfully in both situations.42,61 With intra-study calibration of observers, simple success-failure analyses may of course also be applied for such comparisons. However, comparisons across studies cannot be done reliably.


EPIDEMIOLOGY

Eriksen et al.71-77 have conducted a series of epidemiological surveys using the PAI scoring system. This has made possible direct comparison of the distribution of apical periodontitis and endodontic treatment results in several different regions and countries. Other investigators78,79 have also produced epidemiological data with the index, adding to our knowledge base with the same methodology. Based on these surveys, with a standardized interpretation of radiographic information, the realization is growing that chronic apical periodontitis is quite prevalent in most societies all over the world and that periapical disease is an important dental health issue and a major cause of tooth extraction in many populations80 (Figure 35).


[Figure 35. Periapical index scores used to record the prevalence of apical periodontitis in 35-45 year-olds in selected countries]


Figure 35. Periapical index scores used to record the prevalence of apical periodontitis in 35-45 year-olds in selected countries (Data from Skudutyte-Rysstad R., Eriksen H.M. Endodontic status amongst 35-year-old Oslo citizens and changes over a 30-year period. Int Endod J 2006;39:637-42.)0



Radiography in the Future of Endodontics


The periapical radiograph has successfully maintained a position of ubiquity and remains indispensable in endodontic practice. The ease and precision with which relatively detailed knowledge can be obtained with this diagnostic tool makes it superior for routine applications today and in the foreseeable future. Critical and evidence-based knowledge of how endodontically relevant changes in teeth and bone are reflected in radiographs remains crucial, and it is an ever challenging task to reduce personal and institutional bias in radiographic interpretation. The dose and cost of scans and the difficulty to use other, sophisticated methods in real time at chairside make it unlikely that these techniques will affect the basic procedures in endodontic diagnosis and treatment. The continued reinforcement of clinicians' proficiency in reading and interpreting the information in periapical radiographs is therefore a key for maintaining and improving the quality in endodontic practice.


On the other hand, tremendous advances are being made with the development of, particularly, the computer-assisted scanning techniques. The technology producing localized scans of areas in the jaw with much reduced dosage holds a promise for future improvements in diagnostic and treatment procedures. New insights and concepts may have to be developed of how the three-dimensional appearance and localizations of apical periodontitis lesions appear in areas of the jaw, where conventional radiography offers limited if any help.


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Edited: 29/05/2011 20:27
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