Clinical Investigation of Mandibular Distal Extension Removable Partial Dental Prosthesis

Objective: Removable partial denture frameworks are complex castings that are difficult to achieve accurate fit. The purpose of this study was to evaluate abutment tooth contact by direct retainer assemblies in function utilizing existing RPD's deemed clinically acceptable by the clinical investigators and the patient. Nine subjects, 5 men and 4 women age 30-74 participated in the study. Subjects were evaluated according to HIPPA.

Methods: Existing Kennedy Class 1 mandibular RPD's with at least 1 distal occlusal rest were evaluated. Each RPD was unloaded (rest) and loaded (function). The direct retainer assemblies of bilateral mandibular distal extension RPD's (Kennedy Class 1) included distal half-T retentive clasps and wrought wire clasp assemblies. Classic Blu-Mousse was used as recording material. Records of the RPD's were made under unloaded conditions using finger pressure to stabilize the prostheses. A second record was made with the patient occluding on cotton rolls to create a loaded condition. Photographs were taken of both records prior to the removal from the RPD.

Results: Findings were noted for each RPD. 50% of the distal rests made contact during the unloaded condition while 53% of the guide planes made contact during rest. During function 43% of the distal rests made contact while 87% of the guide planes made contact during function. There was no significant difference with the contact of the distal rests during loading and unloading. However the contact of the guide planes was significant when comparing loaded and unloaded (p=.05)

Conclusion: The data suggests that direct retainer assemblies do not contact that abutment tooth in the same position during rest and function.

Supported by COSTAR training grant NIDCR T-32 DE14318