ABSTRACT
Magnets were first used for over denture retention in 1977. The use of implant retained over denture with magnets offers a simple treatment approach to the problem of instability of the conventional complete denture. Advantage with magnets include technical simplicity and reduced lateral stresses on the abutments. The purpose of this study was to evaluate the effect of function, thermal changes and time duration on Dyna magnetic force in artificial mouth model. In this longitudinal in vitro study, we used eight Dyna system magnets [2.5 [asterisk] 500]. One magnet was used control and the others were placed in artificial mouth affected by different forces functional and thermal changes ranging from 5 to 55[degree sign]c throughout ten years. The force of repulsion had been measured after 3, 5, 10 years and decreased respectively 11.9%, 19.1%, 22.5%, as compared to baseline, however clinically this reduction was not significant in terms of denture retention. During the study period the magnets lost some of their repulsion force, In addition, their steel coatings were not damaged over time. However, viewing the results of this study, it could be concluded that repetitive function and variable mouth temperature are effective factors in reducing magnet retention in an over denture attachment in the long term