Partial edentulism and removable partial denture design in a dental school population: a survey in Greece.

OBJECTIVES: To investigate the pattern of partial edentulism and the most frequent designs of cobalt-chromium removable partial dentures (RPDs), constructed at the Dental School of Athens, Greece. METHODS AND MATERIALS: Five hundred and fifty-three patients, between 42 and 81 years old, mostly males, treated by undergraduate dental students, were included. The survey was based on visual evaluation of master casts and work authorisation to dental technicians. Aspects examined were: Kennedy Classification, modification areas, major connectors, clasping, placement of rest seats and indirect retention. RESULTS: Kennedy Class I was the most common encountered in the maxilla (50.5%) and in the mandible (70%). The most frequent major connectors were the lingual bar (92.6%) and the U-shaped palatal strap (54%). The most common clasp was the Roach (69.2%) in Class I and Class II. In Class III and IV, the most common was the occlusally approaching clasp (55% and 70%). The most frequent location of the rest was mesial of abutment teeth. On the average, 39.5% of Class I RPDs and 58.6% of Class II RPDs had indirect retainers. CONCLUSION: A combination of the two major philosophies of RPD design (biomechanical and hygienic) was evident in the RPDs examined in our study.

The influence of interimplant distance and attachment type on the retention characteristics of mandibular overdentures on 2 implants: 6-month fatigue retention values.

This in vitro study evaluated the 6-month fatigue retention provided by 5 paired overdenture attachments placed at 3 different interimplant distances (19, 23, and 29 mm). Mean fatigue retention was calculated for each attachment type and compared with the retention produced by the other attachments tested and the initial retention values published earlier. Interimplant distance was found to play a significant role only in the retention of the Hader bar with red and yellow clips. A significant reduction in retention values was observed for 4 of 5 attachment types.

Static implant loading caused by as-cast metal and ceramic-veneered superstructures.

STATEMENT OF PROBLEM: The passive fit of superstructures for implant-supported restorations is affected by each step of the fabrication process. In this context the question arises whether ceramic veneering would increase static implant loading. PURPOSE: The purpose of this study was to quantify the strain development of various fixed partial dentures (FPDs) both in the as-cast condition and after ceramic veneering. MATERIAL AND METHODS: Four different types (n = 10) of 5-unit FPDs (cementable, screw retained/plastic cylinder, screw retained/gold cylinder, screw retained/cemented) representing commonly used types of FPDs were investigated before and after ceramic veneering. Three implants were placed in a model simulating a patient situation, and strain gauges were mounted mesially and distally adjacent to the implants. The strain development was recorded during cement setting (provisional cement) and screw fixation. The data were analyzed statistically using multivariate 2-sample tests (alpha=.1). RESULTS: All FPDs revealed measurable amounts of strain. Neither the type of retention nor the mode of fabrication for conventional screw-retained FPDs had a significant influence on strain development. Ceramic veneering caused an increase in strain development for the conventional fixed partial dentures tested. The lowest strains were found in FPDs cemented to gold cylinders on the model for the metal frames and the ceramic-veneered FPDs. CONCLUSION: Conventional procedures were unable to produce superstructures with absolute passive fit. Ceramic veneering appeared to increase strain development and, thus, inaccuracy of the fit. The technique of cementing superstructures to prefabricated components directly on the implants may compensate for dimensional errors caused by impression making and superstructure fabrication.