Mohamed Salem A. Edibrzi¹ Mohammed M. Abdel Khalik, ² ,Ahmed Samir Khairallah³ , Mohamed Samy EL-Gayyar⁴.
¹Professor of Removable Prosthodontics,Faculty of Dentistry,Mansoura University
² Assist.professor of Removable Prosthodontics,Faculty of Dentistry,Mansoura University
³ Assist.Professor.in machine design,Faculty of Engineering,Mansoura University

Abstract:
Objectives:The aim of the work is to study in vitro the effect of different resilient material design concept used in distal extension RPD on stress transmitted to the abutment teeth:-
The design concept include: 1. occlusal reactive, 2 .flexible base.
Methods:Acrylic resin Model, occlusal reactive mandibular distal extension RPD and flexible base mandibular distal extension RPD were subjected to Strain gauges Fixation and Load application
Results:In this study; no significant difference was found between two groups on non loading side. High strain was recorded in buccal &lingual surface in group B ( flexible base) than group A (occlusal reactive). For both groups higher strain recorded on loading side than non loading side.
Conclusions:occlusal reactive distal extension RPD is superior to flexible base one regards stress transmitted to abutment teeth.
From tissue preservation point of view , occlusal reactive distal extension removable partialdenture is a prostheticapproach tominimize stress applied to the abutment teeth.