Comparison between Acetal Resin and Cobalt-chromium Removable Partial Denture Clasps: Effect on Abutment Teeth

Fabricating an esthetically pleasing removable partial denture while avoiding the unsightly display associated with conventional clasp assemblies presented a challenge to dentists. Among other techniques, this could be done using acetal resin clasps as simple and effective means of improving removable partial denture esthetics.1 Patients often cite lack of retention and poor esthetics as reasons for not wearing their partial dentures. Traditional metal alloy clasps have been shown to exert forces on abutment teeth that exceed those capable of producing tooth movement. In addition, metal display on anterior teeth is often unacceptable. The technopolymer materials were purported to have superior flexibility and exerted less force than the metals on the abutment teeth. These forces fell within the physiological range of those abutments and considered safe for use. This coupled with their pleasing esthetics made them suitable for use on periodontally Statement of problem: Acetal resin has been introduced as an esthetic partial denture clasp material. However, the effects of these clasps on the abutment teeth supporting structures were not clear. Purpose: To evaluate the effects of acetal resin clasps on the abutment teeth supporting structures as compared to cobalt-chromium clasps. Materials and methods: Twenty patients, 12 males and 8 females, with Kennedy class III modification I partially edentulous maxilla and dentulous mandibles were selected for this study. Patients were divided into two equal groups; group 1 received maxillary cobalt-chromium partial denture frameworks with acetal resin Akers clasps. Group 2 received maxillary partial denture with cobalt-chromium frameworks and Akers cobalt-chromium clasps. Crevicular fluid, epithelial attachment loss, and bone height and density of the abutment teeth were evaluated at partial denture insertion and after 6 and 12 months. Paired t-test was used at p ≤ 0.05 to assess the changes in the above parameters in each group. Student t-test was used to compare between the two groups. Results: Crevicular fluid measurements were significantly higher in the first group than that in the second group. There were no differences in epithelial attachment loss between the two groups. There were significantly higher reductions in the bone height and in the bone density in the second group than that in the first group. Conclusion: Acetal resin clasps were superior to cobalt-chromium clasps as produced fewer reductions in bone height and in bone density around the abutment teeth inspite of produced increase in the crevicular fluid. Clinical implications: Since there were lesser reductions in bone height and in bone density around acetal resin clasp abutments, it could be used successfully to retain partial dentures. However, meticulous oral hygiene and proper insertion and removal of partial denture with acetal resin clasps were required to decrease gingival inflammation and crevicular fluid amount.