The fatigue bond strength of fixed-fixed versus cantilever resin-bonded partial fixed dental prostheses

Restorations using posterior resin-bonded partial fixed dental prostheses to replace missing premolar teeth were previously considered to have only variable success. Although 2-unit cantilevered resin-bonded partial fixed dental prostheses have been shown to have similar or improved clinical retention to their 3-unit counterparts, no in vitro evidence supports their use in preference to fixed-fixed designs.

The purpose of this in vitro study was to fatigue load 2 different resin-bonded partial fixed dental prosthesis designs (3-unit fixed-fixed and 2-unit cantilevered) and then compare their bond strengths after loading to failure.

Nickel chromium castings with cantilevered (n=10) and fixed-fixed framework designs (n=10) were bonded with a resin cement to stainless-steel tooth dies supported by a simulated periodontal ligament and subjected to cyclic loading (12 000 cycles). The abutment tooth analog was then secured in a universal testing machine, and the framework was loaded axially away from the tooth die until failure. Differences between the bond strengths of the 2 prosthesis designs were analyzed by a Mann-Whitney U test (P<.05).

The bond strengths of the fixed-fixed group (332 N) were lowered by fatigue loading but not the cantilevered group (421 N) (P<.05).

Three-unit fixed-fixed resin-bonded partial fixed dental prostheses were found to have a lower bond strength than 2-unit cantilevered resin-bonded partial fixed dental prostheses when fatigue loaded.