Long Term Retentive Efficiency of Two Designs of Magnetically Retained Kennedy Class I Removable Partial Over Dentures

Abstract

This in vitro study evaluated the loss of retentive efficiency of Kennedy class I removable partial dentures (RPDs) retained by magnetic attachment with keeper versus those retained by magnets and copings covering the abutment teeth. Six readymade models, representing Kennedy class I with the first premolar bilaterally as last standing abutments, were modified to simulate resiliency of oral mucosa and abutments periodontal ligament. Six RPDs constructed from the same material and having the same design were constructed. They only varied in the design of magnet used for retaining the dentures. The first group, constituted RPDs retained by magnetic attachments with keepers on the abutments. While, the second group constituted RPDs retained by magnetic attachments with copings cemented on dome shaped abutments. Bar joining both sides of RPDs with a ring in the middle was constructed and attached to the geometric center of the RPDs. The ring was attached to the hook of the universal testing machine. Insertion/separation cycles of RPDs were applied to assess the changes in the force required to remove the RPDs at 0, 500, 750 and 1000 insertion/separation cycles. The results revealed more change in the retentive efficiency of RPDs retained by magnetic attachments and copings compared to RPDs retained by magnetic attachments and keepers. It was thus concluded that magnetic attachments with keeper retain their retentive efficiency more than magnets and copings.