J11-198.indd 439 Journal of Oral Science, Vol. 53, No. 4, 439-444, 2011 Original Asymptomatic radiopaque lesions of the jaws: a radiographic study using cone-beam computed tomography Masao Araki1,3), Naoyuki Matsumoto2,4), Kunihito Matsumoto1,3), Masaaki Ohnishi1), Kazuya Honda1,3) and Kazuo Komiyama2,4) 1)Department of Oral and Maxillofacial Radiology, Nihon University School of Dentistry, Tokyo, Japan 2)Department of Pathology, Nihon University School of Dentistry, Tokyo, Japan 3)Division of Advanced Dental Treatment, Dental Research Center, Nihon University School of Dentistry, Tokyo, Japan 4)Division of Immunology and Pathobiology, Dental Research Center, Nihon University School of Dentistry, Tokyo, Japan (Received 13 April and accepted 6 September 2011) Abstract: Panoramic radiography and cone-beam before bone sclerosis. (J Oral Sci 53, 439-444, 2011) computed tomography (CT) were used to analyze asymptomatic radiopaque lesions in the jaw bones Keywords: osteosclerosis; panoramic radiography; cone- and determine the diagnostic relevance of the lesions beam CT; diagnosis. based on their relationships to teeth and site of origin. One hundred radiopaque lesions detected between 1998 and 2002 were examined by both panoramic Introduction radiography and cone-beam CT. On the basis of Most cases of idiopathic osteosclerosis of the jaws panoramic radiographs, the region was classified are detected incidentally on panoramic radiography. as periapical, body, or edentulous, and the site was Due to the findings from studies of the characteristics classified as molar or premolar. Follow-up data from of this condition, its morphologic aspects can now be medical records were available for only 36 of these ascertained from radiologic images and histopathologic cases. The study protocol for simultaneous use of cone- findings (1-8). However, the relationship between internal beam CT was approved by the ethics review board of osteosclerotic changes and their features on diagnostic our institution. A large majority of radiopaque lesions images remains unclear. were observed in premolar and molar sites of the Patients with radiopaque lesions in the jaws are some- mandible; 60% of lesions were periapical, 24% were times referred to our outpatient clinic for diagnosis. As in the body, and 16% were in the edentulous region. cone-beam computed tomography (CT) was not clinically An interesting type of radiopaque lesion, which we developed before 1997, diagnosis of such lesions was named a pearl shell structure (PSS), was observed on much more difficult than it is now. When necessary, we cone-beam CT in 34 of the 100 lesions. The PSS is a now use cone-beam CT for the diagnosis of radiopaque distinctive structure, and this finding on cone-beam lesions and have observed an interesting structure in CT likely represents the start of bone formation some of these lesions, which we have named a pearl-shell structure (PSS) because of its radiographic resemblance Correspondence to Dr. Masao Araki, Department of Oral and to a pearl from the Japanese Akoya pearl oyster. PSSs Maxillofacial Radiology, Nihon University School of Dentistry, can be observed on cone-beam CT and, in some cases, on 1-8-13 Kanda-Surugadai, Chiyoda-ku, Tokyo 101-8310, Japan panoramic radiography and dental radiography (Fig. 1). Tel: +81-3-3219-8084 Fax: +81-3-3219-8354 Moreover, differential diagnosis of radiopaque lesions E-mail: email@example.com might be improved by knowledge of their site of origin,
440 a b c d Fig. 1 a. Panoramic radiograph shows a radiopaque lesion in the body of the right lower premolar site of the mandible. b, c, d. Cone-beam CT images (b: parallel section, c: cross-section, d: horizontal section). The radiopacity of the lesion varies, and a central region with increased opacity is visible (pearl shell structure, PSS). These CT images clearly show the heterogeneous form of the PSS. a b c Fig. 3 Cone-beam CT images of PSSs in the periapical Fig. 2 Sites of radiopaque lesions detected on panoramic region of the right lower canine site of the mandible. radiographs. These CT images clearly show a small homogeneous radiopaque spot in the central region. a: parallel section, b: cross-section, c: horizontal section particularly with regard to whether their origin is odon- The panoramic radiographs were used to classify the togenic or nonodontogenic. However, these factors are region of the lesions as periapical (in contact with the outside the scope of the present research. tooth root), body (within the mandible), or edentulous This retrospective study used panoramic radiography (in the edentulous alveolar bone) (Fig. 2). Cone-beam and cone-beam CT to analyze asymptomatic radiopaque CT was then used in all cases to analyze radiopaque lesions in jaw bones and determine the diagnostic rele- lesions and their contents. On cone-beam CT images, vance of PSSs, based on the site of origin of the lesions a PSS was defined as a small, more intense, radiopaque and their relationship with the teeth. spot within a radiopaque lesion. Radiopaque regions that resembled an osteosclerotic mass were also included in Materials and Methods the present study (Fig. 1). A PSS represents a wide range We examined 100 radiopaque lesions that had been of possible lesions, but must be observable in at least two revealed by panoramic radiography (imaging conditions: directions on cone-beam CT images, i.e., parallel (Fig. 70-75 kVp, 7-10 mA) between 1998 and 2002. First, we 3a), cross- (Fig. 3b), and horizontal (Fig. 3c) sections. determined the characteristics of lesions by identifying Two experienced radiologists evaluated the cone-beam their location on panoramic radiographs. Then, we CT images and identified PSSs on randomly selected obtained images of the lesions using a cone-beam CT panoramic radiographs and cone-beam CT images. device (3DX; Morita Corp, Kyoto, Japan; 85 kVp, 10 We reviewed the medical records of patients for whom mA, and 17 s, with a total filtration of 1.2 mm Cu). All follow-up data from medical records were available (36 patients were given a detailed explanation of cone-beam of the 100 cases). Among these patients, we investigated CT. The study protocol for the use of cone-beam CT was the condition of adjacent teeth, including the need for approved in advance by our institution’s ethics review dental treatment, pulp vitality, abrasion of the occlusal board. surface, and the presence of pain.
441 Table 1 Age and sex distribution of the patients Table 3 Comparison of panoramic radiographs and images Age Male Female from cone-beam computed tomography (CT) 10-19 2 5 Entitiy Method 20-29 4 20 PSS Non-PSS 30-39 6 12 Panoramic radiography 4 96 40-49 2 15 Cone beam CT 34 66 50-59 6 13 n = 100, PSS: Pearl shell structure Cone beam CT: Cone-beam Computed Tomography 60-69 0 9 70-79 0 5 80-89 0 1 Total 20 cases 80 cases Table 4 Follow-up data from the clinical records of 23 patients with radiopaque lesions accompanied by a pearl shell structure Area A B C D Table 2 Distribution of radiopaque lesions in the jaw bones, P-region (n = 14) 7 12 7 0 and number of patients with pearl shell structures B-region (n = 7) 4 5 6 0 (PSSs) E-region (n = 2) – - – 1 Site Incisor Premolar Molar Angle A: No dental treatment, B: Vital tooth, C: Abrasion, D: pain Mandible P-region: Periapical region shows radiopaque lesions in contact with P-region 1 18(6) 31(9) 1 the tooth root B-region 3(1) 14(11) 4 2(1) B-region: Body region shows radiopaque lesions within the mandible E-region 0 4(1) 6(3) 5 E-region: Edentulous region shows radiopaque lesions in edentulous Maxilla alveolar bone P-region 3 3 3(1) 0 B-region 0 0 1 0 E-region 0 0 1(1) 0 n = 100, ( ): Numbers of PSS and the mean age of these patients was 36.9 years. A P-region: Periapical region shows radiopaque lesions in contact with PSS was most commonly found in the premolar and the tooth root B-region: Body region shows radiopaque lesions within the mandible molar sites, particularly within body lesions at premolar E-region: Edentulous shows radiopaque lesions in edentulous sites and within periapical lesions at molar sites. Thus, alveolar bone PSSs tended to be located at a distance from the roots of teeth. In a comparison of panoramic radiographs and cone-beam CT images, the presence of a PSS could be Statistical analysis confirmed by panoramic radiography alone in only 4 of We used the chi-square test for independence to analyze the 34 cases (Table 3). the location of radiopaque lesions and the specific site Thirty-six patients with radiopaque lesions (including within that region. We used the same test to evaluate 23 with PSSs) were followed using information from the relationship between PSS site and the location of clinical records. The condition of adjacent teeth was radiopaque lesion formation. Fisher’s exact probability as follows: 11 patients did not need dental treatment, test was used to evaluate the relationship between the 17 showed pulp vitality, 13 had abrasions of occlusal presence of a PSS and dental attrition. A P value < 0.05 surfaces, and 22 were free of pain (Table 4). was considered to indicate statistical significance. We confirmed two PSS lesions histopathologi- cally and found that these were caused by condensing Results osteomyelitis. One of these patients was a 14-year-old The 100 lesions were found in 20 men and 80 boy with the typical findings of a PSS on panoramic women. The mean age of the patients was 41.9 years radiography (Fig. 4a). Histopathologically, the center (range, 10–82 years; Table 1). Regarding the evaluation of the PSS consisted of a mass of remodeling bone and of panoramic radiographs, the most frequent sites of was surrounded by wide, bony trabeculae and irregularly radiopaque lesions were the premolar and molar sites of shaped, fibrous bone marrow (Fig. 4b). the mandible. The region was classified as periapical in The chi-square test for independence showed a statisti- 60 cases, body in 24 cases, and edentulous in 16 cases cally significant association between the region of lesion (Table 2). A PSS was found in 34 of the 100 cases (34%), formation and lesion site. However, PSS site was not
442 the lesion. PSSs can be observed on cone-beam CT and are sometimes visible on intraoral and panoramic radio- graphs. In the present study, 4 of 34 cases with PSSs were confirmed by both panoramic and dental radiographs. The fact that these structures can be observed on plain radiography suggests that they are areas of the central bone that are undergoing bone sclerosis and therefore have higher radiographic density as compared with the a b surrounding bone lesion. Histopathologic examination of Fig. 4 a. Panoramic radiograph shows a radiopaque lesion a completely resected lesion containing a PSS showed that with a PSS between the left lower canine and first the center of the remodeling bone mass was surrounded premolar. b. Histopathologic image of a lesion resected by wide bone trabeculae and irregularly shaped fibrous at surgery shows that the center of the remodeling bone mass is surrounded by wide bone trabeculae and bone marrow (Fig. 4b). This particular case was caused irregularly shaped fibrous bone marrow. by condensing osteomyelitis. Radiopaque lesions occurring in the periapical region can be neoplastic lesion or dysplastic lesion or inflam- matory lesion (3). Therefore, it can be challenging to significantly associated with the region of radiopaque differentiate between a cement-like lesion derived from lesion formation. Similarly, Fisher’s exact probability the odontogenic epithelium and an osteogenic lesion test showed no significant association between the pres- in the area around the dental root. We have previously ence of a PSS and dental attrition. described our experience regarding the site of occurrence and a variety of forms of jaw enostosis and have observed Discussion extensive overlap of the dental root by enostosis (18). Although the cause of most radiopaque lesions in Such areas of bone sclerosis around a tooth are usually the jaws is unclear, the etiologic factors for some of diagnosed as odontogenic lesions. However, based on these lesions are gradually being discovered. Most observation of tooth attrition, the present study found that radiopaque lesions are asymptomatic and are discovered many radiopaque lesions in the periapical region were incidentally on panoramic tomographs or on cone-beam caused by stimulus of occlusal disharmony without pain. CT images obtained during preoperative assessment of Interestingly, radiopaque lesions with a PSS are often dental implants. These lesions can be benign tumors or located in the body region, far from the apex of the dental reflect dysplastic or inflammatory changes, and can have root. These findings are perplexing. One possibility is complex imaging findings (9). Various terms have been that these lesions are a response to traumatic injury. used to describe such lesions, including idiopathic osteo- Thus, as mentioned above, we believe that PSSs should sclerosis (10-15), dense bone island (9,16,17), enostosis be followed up to determine whether they are a starting (18,19), focal periapical osteopetrosis (7), and condensing point for bone sclerosis resulting from inflammation or a osteitis (20). In addition to their varying appearance, the persistent focus of increasing bone sclerosis. size of these lesions can change in a number of ways The present findings offer new evidence regarding (17). Not all asymptomatic radiopaque lesions are surgi- the regions of the jaw where radiopaque lesions occur. cally removed soon after detection. Some are observed The most frequently involved regions were premolar and over a long period, which allows their behavior to be molar sites of the mandible; body lesions at premolar sites predicted. For these reasons, a comprehensive analysis and periapical lesions at molar sites were particularly of radiopaque lesions is not currently possible. common. These findings require careful consideration. At In this study, we detected a small radiopaque mass a molar site, occlusal disharmony can cause hard-tissue within some of these radiopaque lesions. We noted this formation along the periodontal space. At a premolar site, X-ray finding in the present study and refer to it as a pearl the body area of the mandible is not close to the dental root shell structure, or PSS. We initially thought that the PSS but is near the highly vascular mental foramen. Persistent, might be related to the formation of a radiopaque lesion strong stimulus from occlusal disharmony could lead to within the bone. However, in the present study, we used bone sclerosis in the alveolar bone, which is suggested cone-beam CT to examine 100 cases, and a PSS was by the many cases of radiopaque lesions near the mental found in only 34% of the cases. This suggests that a PSS foramen. Another possible etiologic factor is that the is an indicator of the site where bone formation begins in premolar site of the mandible has a bowed configuration
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