Development of in vivo measuring system of the pressure distribution under the denture base of removable partial denture

Purpose: To develop a system to measure the pressure distribution under the base of a removable partial denture (RPD) and to apply it in vivo. Methods: A tactile sensor sheet with 100 sensing points and a measuring system (I-SCAN™, Nitta, Osaka, Japan) were used. The sensor was calibrated before being applied in vivo. A subject with a mandibular RPD (Kennedy class II, division 1) participated in this study, and the RPD was duplicated as the experimental denture. The basal surface at distal extension was accommodated to the sensor in a manner similar to direct relining. Measurements were performed with three patterns of occlusal rest design (mesial and distal rests, mesial rest only, and without a rest) during maximal voluntary clenching (MVC) and gum chewing. Results: The calibration measurements showed that the output value from each sensing point and total output of sensing points were positively correlated with the applied load. The pressures recorded in vivo varied depending on the locations of sensing points on the basal surface of the denture. During MVC the pressure distribution changed with the clenching level, and the highest pressure was registered near the residual ridge crest. The pressure distribution also changed according to the number of occlusal rests. The load center shifted about 2 mm during MVC and about 4 mm during gum chewing. Conclusion: The measuring system developed here enabled us to measure the pressure distribution under the denture base of RPD. The pressure distribution varied along with the design of the occlusal rest.