Journal of Endodontics Research - http://endodonticsjournal.com
Idiopathic osteosclerosis of the jaws followed through a period of 20-27 years
http://endodonticsjournal.com/articles/93/1/Idiopathic-osteosclerosis-of-the-jaws-followed-through-a-period-of-20-27-years/Page1.html
By JofER editor
Published on 09/9/2008
 
A. Halse & O. Molven
Section of Oral Radiology and Section of Endodontics, School of Dentistry, University of Bergen, Bergen, Norway.

Aim.
The aim of the present study was to examine the prevalence of idiopathic osteosclerosis (IO) in a baseline sample and to follow the patients through an extended period of time.

Conclusion.
The present investigation showed that IO lesions observed over a period of more than two decades were stable. The observations support the theory that IO should be considered a normal anatomical variant of bone. In some cases, a local aetiological agent may cause development of structures with an identical appearance.

Introduction - Materials and methods.
A. Halse & O. Molven
Section of Oral Radiology and Section of Endodontics, School of Dentistry, University of Bergen, Bergen, Norway.

Introduction.
Well-defined radiopaque bony lesions are occasionally observed in the alveolar process of the jaws, primarily in the molar and premolar regions. They are most common in the mandible, where they may also be observed more closely to the inferior border. These lesions appear round, elliptical or irregular in shape and are generally asymptomatic and without any obvious aetiological agent.
Several names of this condition are found in the literature. Based on the unknown origin, the term idiopathic osteosclerosis (IO) is often used (Geist & Katz 1990, Yonetsu et al. 1997, MacDonald-Jankowski 1999). Another common name is dense bone islands (McDonnell1993, Kawai et al.1996, Petrikowski & Peters 1997).
A number of studies have estimated the prevalence of such alterations. The reported percentages vary either because of a true difference amongst the samples or by different diagnostic criteria being applied. The lowest prevalence, 2.3%, was recorded in a Canadian sample (Petrikowski & Peters 1997) and the highest one, 9.7%, in a Japanese population (Kawai et al.1992).
The biological behavior of IO has not been well clarified. Bone deposition in response to increased occlusal forces has been proposed as an aetiological factor (Geist & Katz1990), or the lesions might represent intraosseous anatomic variations (Fireman 1976, Yonetsu et al.1997). A search of the literature has revealed only two longitudinal studies of IO (Petrikowski & Peters 1997,Williams & Brooks 1998). Petrikowski & Peters (1997) followed a group of young patients for a period of 1-10 years, whilst Williams& Brooks (1998) had a mean observation period of10.4 years in an adult population.
A sample of endodontically treated teeth in patients has been followed over a period of up to 27 years (Molven et al. 2002), which has permitted investigation of a variety of nonendodontic variables. Even though the long term sample was limited in size, it was judged to be of special interest owing to the long observation time. The aim of the present study was, therefore, to examine the prevalence of idiopathic sclerosis in a baseline sample and to follow the patients through an extended period of time.

Materials and methods.

Patients.
A group of patients who had root fillings at the School of Dentistry, University of Bergen were contacted and invited to attend for re-examination 10-17 years after the treatment. Of this sample of 431 persons, 238 were examined. Details concerning patient data are given elsewhere (Halse et al. 1985). These 238 patients were the basis for the material included in the present study.
Ten years after the first re-examination, 167 of the 238 patients were contacted. Patients aged 76 years or more were excluded, and patients who had died or had moved to other parts of the country were identified. Overall, 156 patients responded and 131 appeared for examination.
Radiographs and files of 210 patients from the first reexamination and130 patients from the second re-examination were found satisfactory for the present study. A survey of the patient samples is presented in Table 1. Further details concerning patient data are given by Molven et al. (2002).

Radiographic methods and diagnostic criteria.
Complete series of intraoral radiographs exposed with a standardized technique were available for all patients. Based on the criteria used in other studies, the present criteria for diagnosing IO were: well-defined radiopacity of more than 3 mm in size; round, elliptical or more irregular in form; no surrounding radiolucent rim (Yonetsu et al.1997). Exclusion criteria were all other specific diagnoses, with special awareness of periapical lesions, tori and dental hard-tissue remnants.
All the films were evaluated by one of the authors (A.H.). Data concerning location and characteristics were recorded for the cases with an obvious IO diagnosis, as well as for a number of uncertain or borderline cases. The latter cases were jointly evaluated by both the authors. The final viewing and comparison of all the cases with a positive diagnosis was also performed as a joint evaluation.

Statistical analysis.
Differences between patient groups were examined by chi-square and Mann-Whitney tests using a computer program (Minitab1996).

Table 1. Patients distributed according to sex and age at the second and third examination.

Patients distributed according to sex and age at the second and third examination


Results.
Baseline examination.
Twenty-seven patients were selected by one examiner (A.H.) for further evaluation, including uncertain and borderline cases. At the joint evaluation11 patients, each with one possible lesion, were excluded. Eight were recorded as having residual roots and three normal morphology.
Sixteen of the 210 patients examined were found to have IO. Fourteen had one lesion, one had two lesions and another one had three lesions. Eight patients (50%) were females as compared to 63% females in the whole patient group, indicating no sex predilection (P = 0.18, chi square). The mean age of the patients with IO was 47 years as compared to 44 years for the rest of the patient group, indicating no significant difference (P = 0.25, Mann-Whitney). The majority of the 19 lesions were found in the mandible, 11 in the molar area and three in the premolar area. Three lesions were found in the maxillary molar area and two in the premolar area. The maximum diameter was 15 mm as measured directly on the film.

Follow-up after 10-17 years.
Seventeen lesions remained unchanged, one showed reduced size, whilst one had disappeared. The latter was in a female aged 40 years at the baseline examination and 57 years at the follow-up (Fig.1). At the follow-up, remnants of the sclerotic structure were hardly visible in the region of the maxillary second premolar. This was the only lesion with a location corresponding to an earlier alveolus. The same patient had two other lesions, in the mandibular right and left molar areas, respectively.
One new lesion appeared. Whilst the region of a first mandibular molar now showed the typical IO appearance, the retrospective viewing of the same region 13 years earlier clearly showed a residual root.

Follow-up after 20-27 years.
The number of individuals that could be examined at the second follow-up was reduced from 210 to 130. Eight patients with nine IO were thus lost, and eight patients with one lesion each could be followed. Two lesions - which at the first follow-up were unchanged - now showed reduced size (Fig. 2). Six lesions remained unchanged (Fig. 3). Two new lesions occurred, one in the first maxillary molar region and the other in the second mandibular molar area. In both the cases, residual roots were observed in the radiographs taken 10 years earlier.

Figure 1. Osteosclerotic lesion in a 40-year-old female, located in the alveolar area of the first maxillary premolar (left). Seventeen years later, the lesion was recorded as disappeared, with hardly any sclerotic structures being visible (right).

Osteosclerotic lesion in a 40-year-old female, located in the alveolar area of the first maxillary premolar

Figure 2. Osteosclerotic lesion in a 42-year-old female, located in the alveolar process in the area of the distal root of the first mandibular molar (right). After 25 years, the size is somewhat reduced; especially the contour of the distal root can now be seen (left).

Osteosclerotic lesion in a 42-year-old female, located in the alveolar process in the area of the distal root of the first mandibular molar

Figure 3. Osteosclerotic lesion in a 44-year-old male, located in the central portion of the alveolar process of a missing mandibular first molar (left). No change is seen after15 years (middle). Also after 25 years it remains unchanged (right); subtle deviations in appearance were ascribed to exposure variables.

Osteosclerotic lesion in a 44-year-old male, located in the central portion of the alveolar process of a missing mandibular first molar


Discussion - References.
Discussion.
The present sample of adults had a 7.6%prevalence of IO within the jaws with no sex predilection and a mean age of the patients with IO that did not differ from the rest of the sample. Owing to the small size of our patient sample, we should be cautious while interpreting the results and drawing conclusions. The prevalence of IO has, however, been reported in a number of studies (Farman et al. 1978, Geist & Katz 1990, Kawai et al.1992, Petrikowski & Peters 1997,Yonetsu et al. 1997,Williams & Brooks 1998, MacDonald-Jankowski 1999) and our findings are in agreement with their main observations. Investigations on adult patients have generally shown a prevalence in the range of 3-8%, no sex differences have been found, and the majority of the lesions have been observed in the mandibular premolar and molar areas.
Knowledge of the prevalence and characteristics of IO is mainly based on the cross-sectional studies. Obviously, longitudinal studies may provide valuable information concerning origin and development of lesions, and all our patients were followed for at least10 years. In addition, a subsample of 130 individuals were followed for 20 years or more; only two earlier longitudinal studies have been published (Petrikowski & Peters 1997, Williams & Brooks1998).
Petrikowski & Peters (1997) examined a population of 2991 orthodontic patients, both children and young adults (5-35 years). Few patients were 25 years or older, and the mean age of the group was 14.0 years. All had a pretreatment panoramic radiograph and a follow-up panoramic radiograph taken1-9 years later. The earliest age at which an IO was detected was 9.4 years. The proportions of patients with IO in the age groups above 10 years were similar. In total, re-examination of the patients over varying time periods showed that 40% of the IO lesions increased in size, whilst 45%remained static. In addition to the lesions diminishing in size, three cases demonstrated complete regression. The authors commented that this phenomenon had not been described earlier. Their conclusion was that IO develops during early adolescence and that the lesions are somewhat labile, especially during adolescence.
Williams & Brooks (1998) examined complete series of intraoral radiographs of 1585 adults; their mean age was 44 years and the mean follow-up period was 10.4 years. They found only small changes during the observation period and proposed that in cases where the diagnosis was certain, no action or further follow-up was indicated.
Moreover, the cross-sectional study of Yonetsu et al. (1997) on the prevalence of IO includes some CT examinations, providing detailed information about the location of the lesions. Eleven patients, all with lesions in the mandible, out of the 64 patients with IO had a CT examination performed for some other reason. Five lesions appeared as thickening of cortical bone and were classified as enostoses. Six lesions were located within medullary bone and were classified as central sclerosis. Four of these six presented as homogeneous, rather dense radiopacities within medullary bone, whilst two had a heterogeneous appearance with varying density. Because of the characteristics and the locations, the authors concluded that IO represented normal variants of bone, being developmental rather than reactive.
With in the jaws or close to them, there are other skeletal structures also with varying frequency of occurrence and varying features. Torus mandibularis and torus palatinus are relatively common structures and two studies on Scandinavian populations (Eggen & Natvig 1991, Haugen 1992) indicated that they present themselves in late adolescence or early adult hood. There after, they are relatively stable, even though cross-sectional studies have found somewhat varying prevalence in different age groups. Exostoses, i.e. protuberances of bone located in various areas of the jaws, represent a similar entity. Jainkittivong & Langlais (2000) performed a cross-sectional study on their prevalence and found that the occurrence was moderately related to increasing age and that the13-19-year group displayed a low prevalence. More or less extensive ossifications within the stylohyoid ligament are often observed in panoramic radiographs just posterior to the mandibular ramus. According to a longitudinal study by Omnell et al. (1998) on orthodontic patients, the majority of these ossification sites are established during adolescence. A few were recorded between the ages of 20 and 30 years.
Thus, it appears that several skeletal structures with varying frequency of occurrence are established during late adolescence and early adult hood. As for their period of development, it is similar to that of IO.T his might indicate a common causative factor, most probably genetic, and that the alterations might be considered anatomical variants.
It has been maintained (Gibilisco 1985) that with IO most frequently found located in the premolar and molar areas, they might represent residual roots from deciduous molars, resorbed and replaced by sclerotic bone. The longitudinal study on young patients by Petrikowski & Peters (1997) gave, however, no indication of root remnants being anaetiological factor. Histological examination might provide information about possible dentine remnants. But because there is no clinical indication for removal of these lesions, and because biopsy on merely scientific indications would be problematic for ethical reasons, such data are sparse. One investigation, however, correlated radiological and histological findings of different radiopaque conditions within the jaws and included seven cases of sclerotic bone, defined as a circumscribed bulk of compact bone situated where the bone is normally cancellous (Henrikson et al.1963). In one case, the histological examination clearly demonstrated sclerotic bone containing a retained root.
In our study, residual roots, whose periodontal structures disappeared and later presented themselves as IO, were observed in three patients. This indicates that though the majority of the cases diagnosed as IO cannot be explained by this factor, the phenomenon may be occasionally observed.

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