Effect of flexible acrylic to substitute metal in implant supported removable partial denture on abutments clinical and radiographic outcome

Abstract
Purpose: To evaluate clinically and radiographically the effect of flexible acrylic clasp and framework versus metal in on abutment teeth in implant modified distal extension cases.
Methods: eighteen participants with mandibular class I partially edentulous arches modified by posterior implants opposing edentulous maxilla were allocated by simple randomization into three groups according to the removable partial denture material as follows; metal framework with RPA clasp (G1), all flexible partial denture (G2) and metal framework with flexible clasp (G3). Clinical parameters of teeth abutments with radiographic outcome of teeth/implant abutments were investigated and compared for the three groups.
Results: gingival crevice fluid volume, pocket depth and periotest values were significantly increased in all groups but comparison revealed more increase in G2 and G3. While radiographic abutment crestal bone changes were statistically significant in G1 compared to the other groups.
Distal implant did not show significant differences in marginal bone level between groups.
Conclusions: Flexible acrylic clasp challenge abutment tooth hygiene and may be a risk for future periodontitis. The traditional metal framework removable partial dentures, with RPA clasp, exceed the rest-less flexible clasp and transmit more masticatory loads to abutment teeth and in turn less preservative to surrounding alveolar bone. The hybrid design that combined a metal framework and acrylic flexible clasp and denture base may be a viable alternative when aesthetics are of primary concern and should include metal rest component.