Mandibular Bone Mineral Density Changes in Removable Partial Denture Wearers Dependent on Differences in Denture Support

Objectives: Radiographic assessment of bone quality is of great value in planning prosthodontic treatment. Panoramic radiographs are routinely taken prior to prosthodotnic treatment planning. The aim of this study was to determine the changes in bone mineral density (BMD) of the mandible in free-end saddle removable partial denture (RPD) wearers wearing dentures of different support, during a six month period. Methods: Twenty RPD patients (5 men, 15 women) participated. The BMD measurements were performed on digitized dental panoramic radiographs with a 5 step copper stepwedge attached to each film cassette. Grey levels of each step of the stepwedge were transformed to optical density values, and using the 3rd degree polynomial regression formula was calculated for each digitized image, to express BMD values of the measured regions of interest on the mandible in the copper stepwedge thickness equivalents. The difference in BMD values between the first and the second measurement for each region of the interest within gender, age groups and different type of RPDs was calculated. Results: The results revealed that the BMD values in the regions under the denture saddles of partially edentulous mandibles, in the projection of the mental foramen and mandibular ramus, significantly decreased in mucosa supported dentures and in tooth and mucosa supported dentures BMD values significantly increased within 6 months. BMD values at gonion significantly increased over 6 months in both groups, but increase was higher in tooth supported RPDs. Conclusions: The results support the idea that under the base of mucosa supported dentures occlusal forces stimulate bone resorption, while under the base of tooth and mucosa supported dentures, occlusal forces may even cause apposition of the bone.