|Year : 2013 | Volume
| Issue : 2 | Page : 48-54
The evaluation of idiopathic osteosclerosis on panoramic radiographs with an investigation of lesion's relationship with mandibular canal by using cross-sectional cone-beam computed tomography images
Melda Misirlioglu1, Rana Nalcaci2, Mehmet Zahit Adisen1, Selmi Yilmaz1
1 Department of Oral and Maxillofacial Radiology, Faculty of Dentistry, Kirikkale University, Kirikkale, Turkey
2 Department of Oral and Maxillofacial Radiology, Faculty of Dentistry, Ankara University, Ankara, Turkey
|Date of Web Publication||21-Oct-2013|
Mehmet Zahit Adisen
Department of Oral and Maxillofacial Radiology, Faculty of Dentistry, Kirikkale University, Kirikkale
Source of Support: None, Conflict of Interest: None
Objective: The aim of this study was to determine the prevalence of idiopathic osteosclerosis (IO) in a Turkish population on orthopantomographs with respect to age, sex, and lesion characteristics and investigate the lesion's relationship with mandibular canal with the aid of cross-sectional cone-beam computed tomography (CBCT) images. Materials and Methods: 8000 panoramic radiographs taken with two digital orthopantomograph devices over a 10-month period were evaluated. Each patient was assigned an identification number, and demographic information (age, sex), absence/presence of a lesion, and if present, lesion characteristics (localization, dental relationship, size, and shape) were recorded. Additionally, cross-sectional CBCT images of 30 patients with IO were examined in terms of relationship with mandibular canal. Results: 273 IO lesions were detected in 225 patients (130 females, 95 males; mean age: 33.1 years). The majority of lesions were observed in the mandibular premolar and molar areas. IO lesions occurred more frequently among middle-aged individuals and at higher rates among females (3.1%, n = 130) than males (2.8%, n = 95); however, differences by age and sex were not statistically significant (P > 0.05). Cross-sectional images revealed that 80% of the lesions were in contact with mandibular canal. None of the lesions showed any cortical expansion. Conclusions: This large-scale study found IO to have a low prevalence rate among a Turkish population. IO was observed to occur more frequently in females than in males and to be most common among individuals aged 20-29. CBCT results suggested a possible association between IO lesions and mandibular canal.
Keywords: Cone-beam computed tomography, idiopathic osteosclerosis, panoramic radiography, Turkish
|How to cite this article:|
Misirlioglu M, Nalcaci R, Adisen MZ, Yilmaz S. The evaluation of idiopathic osteosclerosis on panoramic radiographs with an investigation of lesion's relationship with mandibular canal by using cross-sectional cone-beam computed tomography images. J Oral Maxillofac Radiol 2013;1:48-54
|How to cite this URL:|
Misirlioglu M, Nalcaci R, Adisen MZ, Yilmaz S. The evaluation of idiopathic osteosclerosis on panoramic radiographs with an investigation of lesion's relationship with mandibular canal by using cross-sectional cone-beam computed tomography images. J Oral Maxillofac Radiol [serial online] 2013 [cited 2020 May 29];1:48-54. Available from: http://www.joomr.org/text.asp?2013/1/2/48/120108
| Introduction|| |
Idiopathic osteosclerosis (IO) is the term used to describe radiopacities of unknown cause that are incidentally detected on periapical or panoramic radiographs.  Other terms such as 'dense bone island', 'bone scar', 'bone whorl', 'focal periapical osteopetrosis', 'enostosis' and 'eburnated bone' have also been used to describe these sclerotic areas of the jaw. , IO lesions are always asymptomatic and cannot be attributed to any inflammatory, dysplastic, neoplastic, or systemic disorder, and they are not associated with any detectable cortical expansion. 
IO lesions are most often encountered in the mandibular premolar and molar areas, and they vary in size from 2 mm to 1-2 cm. Radiographically, they may appear round, elliptical, or irregular in shape, and they are well delineated from the surrounding normal bone. Histopathological evaluation has shown IOs to be composed of dense, calcified tissue without marrow spaces. ,
IOs need to be differentiated from periapical cemental dysplasia, submandibular calculus, torus, exostosis, osteoma, odontoma, and condensing osteitis (CO) of dental origin associated with low-grade, chronic inflammation of the bone around the tooth apex as well as from soft-tissue lesions such as tonsilloliths, phleboliths, and sialoliths that may project as radiopacities in panoramic radiographs. ,
The etiology of IO is unclear, but it may involve internal stress and sufficient blood supply to form bone masses in the mandible. Regardless of cause, given that IO lesions are both asymptomatic and harmless, it is generally agreed that their treatment is unnecessary. ,
The aim of this study was to identify the age and sex distribution, localization, shape, size, and dental relationship of IO in a group of Turkish patients and to investigate the lesions relationship with mandibular canal with the aid of cross-sectional cone-beam computed tomography (CBCT) images.
| Materials and Methods|| |
The study comprised of 8000 panoramic radiographs taken from patients who underwent clinical and radiographic examination at Department of Oral and Maxillofacial Radiology between January 2011 and October 2011. The retrospective study plan was approved by the dental faculty administration. Radiographs were captured using two digital orthopantomography devices (Pax primo and Pax uni 3D; Vatech, Seoul, Korea) at the following settings: 60-80 kVp, 8-10 mA, 9.7 sec. exposure.
All examinations were carried out by one of the authors. In order to minimize the risk of false assessments caused by fatigue, no more than 50 radiographs were evaluated at a time. Patient age and sex were recorded for each film. Radiographs in which the full jaws were not displayed and radiographs with technical problems were excluded from further examination. Among the remaining 7502 radiographs, those on which radiopaque lesions were initially detected were reevaluated by two of the authors, and those with any of the following radiopacities were excluded:
Among the remaining 225 radiographs, those with IO lesions were separately assessed by two of the authors, and lesion size, shape, localization, and dental relationships were recorded. In cases where there was any disagreement, a third observer was consulted, and if no consensus could be reached, the radiograph was excluded from further consideration.
- Characteristic mixed radiopaque-radiolucent areas of periapical cemental dysplasia and other benign fibro-osseous lesions of periodontal ligamental origin (i.e., diffuse sclerosing osteomyelitis and florid osseous dysplasia). ,,
- Radiopacities with a surrounding radiolucent rim. 
- Thickening of the lamina dura around teeth showing marked malposition or serving as abutments for fixed bridges or partial dentures. ,,
- Clearly identifiable remnants of deciduous or permanent teeth. ,,
- Radiopacities around teeth with deep caries or large restorations. 
- Possible evidence of CO (i.e., solitary radiopacities in edentulous regions). ,
- Radiographs from patients with torus or exostosis, salivary calculus, tonsilloliths, calcified lymph nodes, and stylohyoid ligaments. 
- Evidence suggesting an expansile lesion (i.e., displacement of the inferior dental canal, floor of the antrum, or teeth adjacent to the lesion). 
- Radiopacities associated with resorption of adjacent teeth. 
- Radiographs from patients with Gardner's syndrome, familial polyposis of the colon and other diseases that involve a metabolic bone disturbance. ,
Dental relationships were defined according to Geist et al.  as follows:
- Interradicular: Sclerotic tissue limited to the area between the roots [Figure 1]a.
- Apical/interradicular: Radiopacities were located at the apices and exhibited significant extension between the roots [Figure 1]b,
- Apical: Masses predominately located around the root apices [Figure 1]c,
- Separate: Radiopacities apical to and clearly separated from the teeth and lamina dura [Figure 1]d.
Lesion size was recorded as the maximum width as measured digitally using the Easydent V4.0 image processing program for panoramic radiographs. (Magnification factor: 1.56:1) Lesion shape was recorded as either round [Figure 2]a, elliptical [Figure 2]b, or irregular [Figure 2]c.
|Figure 1: Dental relationships of idiopathic osteosclerotic lesions according to classifi cation of Geist et al. Interradicular (a), apical/interradicular (b), apical (c), separate (d)|
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|Figure 2: Lesion shape as seen in cropped panoramic radiographs. Round (a), eliptic (b), and irregular (c)|
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Following radiographic analysis, 30 patients CBCT images, which were captured for other clinical diagnosis and treatments with Vatech Pax uni 3D digital orthopantomography device (Vatech, Seoul, Korea) at the following settings: 50-90 kVp, 4-10 mA, 10 sec. exposure, were examined in terms of relationship with mandibular canal. Cross-sectional coronal plane images with 0.2-mm slice thickness were evaluated using the Ez3D2009 software program, and lesions relationship with mandibular canal and cortical bone was divided into two types and four subtypes as follows [Figure 3]: ,
|Figure 3: Schematic drawings of idiopathic osteosclerosis on coronal slices|
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Type I: Separate from mandibular canal
Type II: In contact with mandibular canal
- In contact with buccal cortical bone
- In contact with lingual cortical bone
- In contact with buccal and lingual cortical bone
- Separate from buccal and lingual cortical bones
Data was analyzed using the Statistical Package for Social Sciences Program (SPSS 11.5). Values were recorded as mean ± standard deviation or median (max-min) and compared using the chi-square test. Radiographic evaluations were compared using Student's t-test for parametric data and the Mann-Whitney U test for nonparametric data, with the significance level set at 0.05.
- In contact with buccal cortical bone
- In contact with lingual cortical bone
- In contact with buccal and lingual cortical bone
- In contact with buccal and lingual cortical bone and surrounding the mandibular canal (Because there was no IO which separates from buccal and lingual cortical bone in contact with mandibular canal.)
| Results|| |
Of the 7502 panoramic radiographs examined, 4137 belonged to female subjects and 3365 to male subjects [Table 1]. The age range of subjects was 12-91 years (mean age: 39.1 years). A total of 273 IO lesions were detected in 225 subjects (age range: 12-72; mean age: 33.1). Whereas 181 subjects had single lesions, 44 had multiple lesions, and of these, 40 had 2 IO lesions and 4 had 3 IO lesions [Table 2]. Lesion prevalence was 2.9%. Although lesions were found more frequently in females (3.1%, n = 130) than in males (2.8%, n = 95), the difference was not statistically significant (P = 0.42). Lesions were most frequently seen in middle-aged individuals, especially those aged 20-29 years, but the differences among age groups were not statistically significant (P = 0.42) [Table 1].
|Table 1: Distribution of cases and differences in lesion prevalence by sex and age group|
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Lesion relation to tooth
According to Geist et al.'s criteria for dental relationships, most lesions were classified as apical (36.2%), followed by separate (30.8%), interradicular (19.0%), and apical/interradicular (14.0%) [Table 2]. The distribution of lesions by dental relationship did not vary significantly by number of lesions (single vs multiple) (P > 0.05) [Table 3].
|Table 3: Differences in lesion characteristics by number of lesions (single vs multiple)|
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Site and size
The vast majority of lesions (97.9%, n = 267) were in the mandible, with only 6 lesions (2.1%) in the maxilla, and most were located in the region of the posterior teeth (molar region: 41.0%; premolar region: 33.0%). More than half of all lesions (54.0%) were between 0.5 and 1 cm [Table 2]. Lesions of <0.5 mm accounted for a significantly larger proportion of lesions among individuals with multiple lesions (P = 0.001), whereas lesions of 05-1 cm occurred at statistically higher rates among individuals with single lesions (P = 0.01). In terms of localization, lesions at premolar sites accounted for a significantly higher number of lesions in comparison to all other sites among individuals with multiple lesions (P = 0.003), whereas among individuals with single lesions, premolar-molar (P = 0.04) and molar sites (P = 0.003) were equally common and statistically higher in comparison to other localizations [Table 3].
Lesion's shape was classified as round, elliptic, or irregular, with round (36.6%) and irregular (37.8%) lesions found at nearly the same frequency, followed by elliptical lesions (25.6%) [Table 2]. Lesion shape did not vary significantly by number of lesions (single vs multiple) (P > 0.05) [Table 3].
CBCT analysis results
The age range of subjects was 17-74 years (14 females, 16 males; mean age: 30.2 years). Cross-sectional images indicated that 24 cases (80%) were type II and 6 cases (20%) were type I. Of the 24 type II cases, 16 (53.3%) were present as c type. Distribution of the lesions is shown in [Table 4]. None of the lesions showed any cortical expansion [Figure 4].
| Discussion|| |
IO has been reported to show prevalence rates ranging from 3.1% to 31%. ,, This study found the prevalence of IO to be 2.9%. Differences in reported rates may be due to differences in ethnicity of the study populations, differences in types of radiographs, and differences in criteria used to identify IO.  For example, in contrast to Kawai et al.,  the present study excluded radiopacities in edentulous regions because they could represent surgical scars or residual CO. Moreover, the present study used panoramic radiographs, which have a lower sensitivity than periapical radiographs in detecting lesions, with only 60-83% of lesions present in periapical radiographs detectable in panoramics. 
The present study found IO lesions to be more prevalent among females than males, but the difference was not statistically significant (P = 0.42). This finding is in line with Kawai et al.  Yonetsu et al.  and Sisman et al.  who found no difference in incidence between females and males, but it conflicts with Geist et al.  and McDonnell et al.,  who reported female-to-male ratios of 1.5:1 and 2:1, respectively.
In the present study, the number of IO lesions was found to be higher especially in the third decade; however, differences among age groups were not statistically significant (P > 0.05). This finding is in line with Kawai et al.,  Yonetsu et al.,  and Sisman et al.,  but it conflicts with Miloglu et al.  and Lee et al.  who found significant differences in IO prevalence by age group. The peak prevalence in the third decade found in most reports coincides with, or immediately precedes, the attainment of peak bone mass in the fourth decade.  The decreasing frequency of IO in older age groups found in the present study might be related to the small number of samples.
Many previous studies have reported the prevalence of IO to be higher in the mandible than the maxilla. , Similarly, this study found 97.9% of lesions (n = 267) were in the mandible. In addition, the prevalence of IO was greatest in the posterior region (molar: 41.0%; premolar: 33.0%). These findings could be explained by the fact that the common superposition of anatomic structures make maxillary lesions harder to detect from panoramic radiographs when compared to mandibular lesions.  Furthermore, premolar areas in the mandible may experience concentrated inner distortion, and areas of the mandible near the mental foramen receive sufficient blood supply to easily form bone masses.  The fact that 80% of lesions were detected in contact with mandibular canal in cross-sectional images in the present study supports this idea [Figure 4]. It has been suggested that the location of IOs primarily in the premolar and molar areas ,, is an indication that these lesions could represent residual roots from deciduous molars that have been resorbed and replaced by sclerotic bone.  Histological examination of a lesion diagnosed as IO has clearly shown sclerotic bone containing a retained root, suggesting that microscopic root fragments may act as a nidus for bone proliferation in some cases.  Moreover, given the higher prevalence of caries among molars when compared to other teeth, it is possible that some lesions, such as CO, could be misdiagnosed as IO. 
It has been suggested that any radiopacity associated with an intact tooth or a tooth with shallow caries/fillings could be diagnosed as IO because there is no obvious cause for any inflammation, whereas any radiopacity located at a heavily decayed, filled, or endodontically treated tooth could be diagnosed as CO.  Other possibilities in differential diagnosis include lesions such as torus mandibularis and exostosis, which describes single or multiple radiopaque lesions of the periosteal surface of the jaw that show cortical expansion in tomographic images.  In contrast, IOs show no cortical expansion in tomographic images.  CBCT imaging can be most helpful in diagnosing these conditions. In the present study, cross-sectional images showed no cortical expansion in any of the IO patients.
Yonetsu et al.  were the first to use tomography to investigate IO lesions, but the authors recommend against the routine use of computed tomography (CT) for this purpose. Araki et al.  maintained that CBCT should be used instead of conventional CT because tomography could provide more detailed images of the interior of the jaw bone than periapical and panoramic radiography, which are not always appropriate for IO diagnosis. They stressed that the large osteosclerotic lesions overlapping the roots of teeth tent to represent CO or cemental mass lesions, hence the application of CBCT in these cases may be efficacious. Also, they investigated the type of bone thickening arising from the cortical bone and found that many lesions (70.5%) were in contact with both buccal and lingual cortical bone, which easily observed in detail using CBCT. In the present study, we also found similar results that the most of the lesions were continuous with bicortical bone. These results suggest that bone thickening from inner surface of cortical bone may lead to a tendency for rapid growth in a relatively short period. 
In terms of etiology, Eselman  suggested that IO could be developmental rather than reactive and considered it to be an anatomical variation of normal bone. Eversole et al.  reported excessive occlusal forces as a possible cause of IO. MacDonald et al.  suggested that since IO occurs almost exclusively in the alveolar process, the tooth or its primordium may play a role in the genesis of IO; alternatively, the authors proposed excessive fluoride as an etiological factor.
In study of Sisman et al., most of the lesions of IO were found to be associated with the root apices. Hence, they suggested that slight imbalances in occlusion provide enough vibratory stimulus to provoke bone formation in these patients. On the other hand, they found that the second most common localization of IO lesions were separate from dentition and stressed that stimulatory effects of excessive occlusion would not be a factor in this localization and may support the possibility that IO may be a developmental anatomic variation.  Verzak et al. also supported the theory that IO lesions should be considered developmental variants of normal bone architecture unrelated to local stimuli. 
On the other hand, CBCT results in this study suggested a possible association between IO lesions and mandibular canal and this situation can be explained as follows; areas of the mandible near the mandibular canal receive sufficient blood supply to easily form bone masses. 
Regardless of its origins, because IO is an asymptomatic lesion that is not associated with any other pathological condition and has no negative health consequences, it does not require treatment. ,
In conclusion, this large-scale study found IO to have a low prevalence rate among a Turkish population. IO was observed to occur more frequently in females than in males and to be most common among individuals aged 20-29. CBCT was found to be an effective method for investigating lesions relationship with anatomical structures and an increase in the use of CBCT in the future can be expected to improve our understanding of the nature of these lesions.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]
[Table 1], [Table 2], [Table 3], [Table 4]