Behavior of mandibular canines as abutment teeth and indirect retainers in Kennedy class II Removable Partial Denture Prosthesis

PURPOSE: The purpose of this study was to evaluate the behavior of mandibular canines acting as abutment teeth and indirect retainers of a Kennedy class II according to different designs: lingual rest and lingual rest associated with a reciprocal arm. MATERIALS & METHODS: A resin cast with two simulated canine teeth was made in Ni-Cr alloy, representing a Kennedy class II mandibular arch. With the objective of simulating the resilience of the periodontal ligament, a polyurethane layer was added at the canine tooth's root. A metallic framework of Co-Cr alloy was fabricated with a T bar clasp and a lingual rest associated with a reciprocal arm. To obtain the second framework, the reciprocal arm was removed using a tungsten bur. Each framework was submitted to tensile force using a VersaTest machine. The magnitude and direction of canine movement during removal of the framework was measured using two dial gauges (mm). The axial tensile force required to remove the experimental framework (N) was also evaluated. The data were compared using the paired t-test with 95% confidence intervals. Differences were considered significant at P < .05. RESULTS: The mean retentive force of the modified design framework with the reciprocal arm was significantly higher (P < .0001) than that of the framework with the lingual rest. The abutment teeth showed movement in the lingual and mesial directions, and this movement was less when associated with the reciprocal arm design. CONCLUSION: The reciprocal arm in association with a lingual rest in the framework decreased the movement of the abutment teeth when analyzed in the bucco-lingual and mesio-distal directions and contributed to increased retention by friction.