Journal of Dental Medicine

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Statement of Problem: Odontogenic keratocyst is a developmental odontogenic cyst which arises from dental lamina. One of the important features of odontogenic keratocyst is strong tendency to recurrence.

Purpose: The purpose of this study was the statistical evaluation of age and gender of patient as well as area of involvement in odontogenic keratocysts in the oral and maxillofacial pathology department of dental faculty of Tehran University of Medical Sciences from 1971-2002. Materials and Methods: This study was a cross sectional, descriptive one. Medical records were reviewed and variables such as age, gender and site of involvement were recorded. The data were analyzed with SPSS software.

Results: The relative frequency of odontogenic keratocyst was 36%. 66% of cysts were in men and 34% in women. 68% of lesions affected the lower jaw and 32% the upper jaw. Regarding the site of involvement, 48% of lesions involved the molar region of mandible and 42%, the anterior part of maxilla. The occurrence of keratocysts was higher in this sites. Most of the cases were diagnosed in the third decade.

Conclusion: Based on the findings of this study, odontogenic keratocyst was more prevalent in men, mandible and the third decade. The posterior part of mandible and anterior region of maxilla were involved most frequently.

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Background and Aim: Proper designing of partial denture frameworks is the duty of dentists, but this task is often abdicated to technicians because of lack of time and experience. Computer assisted learning and designing can be used for both training dental students and helping dentists design proper frameworks. As the first step to prepare software for framework designing, this study evaluated the agreement on different framework designing principles, among prosthodontists of dental schools in Iran.
Materials and Methods: A questionnaire consisting of 121 design rules was sent to 41 prosthodontists at seven dental schools in Iran .The percentage rate of agreement on results was used for data analysis.
Results: The percentage of rules accepted by more than 60% of the prosthodontists was 76.2%. It consisted 80% saddle rules, 76.2% rest rules, 78.4% clasp rules, 63.6% maxillary major connector's rules and 80.9% mandibular major connector rules.
Conclusion: The percentage of accepted rules by Iranian prosthodontists was 76.2%. Maxillary major connectors had the least acceptance.

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Background and Aim: Designing removable partial dentures is one of the most important phases of prosthetic treatments. Computer can be used to facilitate and increase accuracy of removable partial denture design. The aim of this study was to develop a software for removable partial denture design.

Materials and Methods: A questionnaire (discussed in part I) and major textbooks, were used to determine the design rules.  The software (RPD Graph) was developed using Visual C++ and Maryam program. The RPD Graph can determine the classification of partial edentulous arch. With defining the missing teeth and providing data about prognosis and conditions of abutment teeth, the removable partial design will be developed by RPD Graph. This software is a knowledge-based system which has specific characteristics. It can be used as an educational tool for teaching RPD design and as a clinical tool for supporting clinician's decision. In addition it can be developed to more complete softwares.

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Background and Aim: Digital subtraction Radiography (DSR) is a method of accurate assessing condylar head changes. several studies have been carried out in applying DSR in dentistry, however there is a few number of studies in efficacy of DSR method in assesment of condylar head changes, The aim of this study was to compare panoramic radiography and DSR detecting simulated lesions of the mandibular condyl.

Materials and Methods: this was a process reaserch study, in which two dry human skulls with no obvious temporomandibular joint pathology were used. Osteophytic lesions were simulated using three sizes of bone chips that were placed on the medial portion of anterior and superolateral aspects of the condyle. Osteolytic lesions were simulated making 1 and 2 mm holes using round burr in the central portion of anterior aspect and Lateral pole of the condyle. Panoramic radiographs were prepared with and without the lesions in place. These paired radiographs were digitized and digital- subtraction images of the original panoramic images were obtained. Eight observers evaluated 155 images of each modality for the presence or absence and the type of simulated lesions of the mandibular condyle. Sensitivity, specificity, reliability and measure of agreement were analyzed using kappa test and crossed tables and qualitative variables were assess by chi-square and fisher's Exact test.

Results: Specificity of panoramic and DSR methods were 15.4% and 66.7% respectively. Sensitivity of panoramic and DSR methods were 61.1% and 80.6% for osteophytic lesions and 37.5% and 83.3% for Osteolytic lesions. The percentage of correct decisions made in DSR method was significantly more than conventional panoramic method (82.6% vs 41.9%) (p<0.0001).

Conclusion: Based on the results of this study digital subtraction technique was significantly more accurate than the panoramic radiographs in detection of simulated lesions of the mandibular condyle.

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