Finite element and Weibull analysis to estimate failure risk in resin-bonded retainers

Three-dimensional finite element analysis and Weibull analysis were used to evaluate the effect of the thickness and the rigidity of the retainers on the risk of failure of an anterior resin-bonded prosthesis. Retainer thickness ranged from 0.4 to 1.4 mm. The physical properties of metals similar to Ni-Cr and type IV gold alloys were used. A concentrated load (100 N) was applied to the incisal edge of the finite element analysis modeled pontic, and the data of other loads (150 to 500 N in 50-N increments) were calculated from the data of 100 N. Subsequent Weibull analysis revealed that failure probability diminished when there was an increase in metal thickness at loads of 300 to 350 N, particularly for the retainer made of a type IV gold alloy. The reduction in failure probability caused by increasing the thickness of the metal was greater when type IV gold alloy was used than when Ni-Cr alloy was used. This investigation suggests that the longevity of resin-bonded retainers can be prolonged by thickening the retainers, rather than using more rigid metals.