Introduction - Materials and methods.
A. Halse & O. MolvenSection 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.