Background and Objective: The use of the resin composite to alter the contour of the tooth has been recognized as a reasonable and non-aggressive method for improving the amount of stoppage for improving the retention of the removable partial prostheses. The aim of this study was to determine the amount of the required force to overcome the retention of undercuts created with resin composite on the abutment teeth
Materials and Methods: In this experimental trial, 20 first premolars were assigned into 2 groups. The resin composite for recontouring the abutment teeth in the buccal surfaces was applied to create the 0.25-mm undercuts. The control teeth with the untouched enamel surfaces were mounted at an angle to form the 0.25 mm undercut on the buccal surfaces. Both groups were encountered by a Zwick/Roelts apparatus under a repetitive force of 4500 cycles. The off-take forces measured before implying the enforce and off-take movements (T0) and after the frequencies mounting500, 1000 and 1500 Hz. The mean amount of the force in every phase of the experiment was compared by Mann-Whitney U test between two groups
Results: Loss of composite bond was not observed. The maximum and minimum of the forces were detected in T0 phase by the resin composite (17.5 and 3.75 N). Also, significant differences were observed in the off-take force between two groups after applying 500 cycles and after implementing the test (p<0.008)
Conclusion: The force required to off-take the framework after implanting for 4 years usage of removal partial prostheses in the teeth with natural enamel coverage was three times more than the contoured group with the composite resin.
)