Hoop Strain in Dental Implants and the Influence of Different Cantilever Lengths, an In Vitro Pilot Stud

Purpose: The purpose of this study is to determine the hoop stress around dental implant in a circumferential and vertical pattern and to compare stress values to different cantilever length on a cross arch implant supported framework.;Material and Methods: A milled cross-arch metal framework supported by 4 implants imbedded in acrylic in addition to one separated implant in the middle. Five T-strain gauge rosette distributed on five dental implants recorded data as they were loaded by 50 and 100 N forces using MTS 810 loading machine. The loading sites were anterior implant, posterior implant, 0.5 Anterior Posterior ,(AP spread) ratio cantilever, 1.0, 1.5 and 2.0 ratio cantilever. Each one of those 7 sites were loaded 10 times for each of the 50 and 100 N generating 360 different reading for each of those groups. Three-way ANOVA was conducted (twice, one for vertical and one for hoop strain) for analysis of strain with factors of: Magnitude of force, extension of cantilever and position of the implants followed by Post hoc Tukey comparison between the groups.;Results: The anterior implant is under tension in vertical direction when forces are applied to the cantilever on the contralateral side. The most posterior implant is under less tension in the vertical direction but shows as much strains in the circumferential direction. Post hoc analysis shows cantilever over 1.0 ratio causes same high amount of stress to the system.;Conclusion: A ratio up of 0.5 AP spread for the cantilever is statistically acceptable. However, A ratio up to 1.0 AP spread for the cantilever exerts no more tension to the system than the load on the implants.