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 implantsupported overdentures was enrolled. Recordings were completed on each subject using a forcemeasuring 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.