Support Ratio Between Abutment and Soft Tissue Under Overdentures: A Comparison Between Use of Two and Four Abutments.

PURPOSE The purpose of this preliminary in vivo study was to compare force distribution on abutments (tooth or implant) and tissues supporting overdentures with two or four abutments. MATERIALS AND METHODS A convenience sample of five subjects with tooth and/or implant-supported overdentures was enrolled. Recordings were completed on each subject using a force-measuring system mounted on a metal framework with four anteroposterior spread abutments (A), four abutments with denture bases (B), and on two anterior abutments with denture bases (C). The tissue-support ratio (TSR) was calculated as (A-B)/A or (A-C)/A. RESULTS TSR values changed 1.5 to 2 times when the number of abutments was reduced from four to two. CONCLUSION The amount of tissue strain on the posterior residual ridge increased when the number of abutments was reduced.