Effect of Direct Retainer Types for a Dento-maxillary Prosthesis on Abutment Teeth of Maxillectomy Patients: In Vitro Study

Abstract

The purpose of this study is to evaluate the effects of different types of direct retainers on the strain around the abutment teeth in a maxillectomy model using strain gauge measurements.
A simulated unilateral left-side maxillectomy model and prosthesis were fabricated. A triaxial strain gauge on #11 and uniaxial strain gauges on #14, #15, #16 and #17 were fixed on the model to determine the deformation under two conditions: a dislodgement force and a vertical occlusal load. A 0.9 mm wire clasp （WC）, an O-ring attachment （OP） and a magnetic attachment （MA） were applied as a direct retainer on #11. The magnitudes of each strain, the maximum principle strains （MPSs） and their directions were statistically analyzed by one-way ANOVA with a post hoc Bonferroni test.
In the dislodgement test, the MPSs of the OP were significantly smaller than those of the WC and MA in almost all tested conditions. Both the MPS and direction of the WC model were found to be the smallest in the occlusal load test. The results suggest that the design of an anterior direct retainer would directly affect prosthesis movement and the associated stress distribution to the area around the abutment teeth in the model.