Adaptation of removable partial denture rest seats in prostheses made with selective laser sintering or casting techniques: A randomized clinical trial.

STATEMENT OF PROBLEM: New fabrication techniques have been developed for removable partial denture (RPD) frameworks although studies validating the clinical application of these techniques are scarce. PURPOSE: The purpose of this clinical study was to compare the adaptation of RPD framework rests made with conventional casting or computer-aided design and computer-aided manufacturing (CAD-CAM) with selective laser sintering (SLS) at the clinical evaluation and 1 year after the delivery of the prostheses. MATERIAL AND METHODS: This triple-blinded pilot study included 18 participants presenting with maxillary and/or mandibular partial edentulism, of which only 7 returned for the second measurement 1 year after prosthesis delivery. Participants were randomly assigned to 1 of 2 groups depending on whether the RPD framework was made with SLS or conventional lost-wax casting. The adaptation of the RPD at the rest seat area was evaluated by injecting a silicone material on the abutment tooth before seating. The silicone specimens were then sectioned transversely and measured with a scanning electron microscope. The statistical analysis was performed with a linear mixed-effect model with the intention to treat and with a 3-factor repeated measures ANOVA (alpha=.05). RESULTS: At the metal framework evaluation (T(0)), the prostheses made with SLS showed a mean +/-standard deviation adaptation of 398 +/-45 mum, while those made with conventional casting presented a mean +/-standard deviation adaptation of 176 +/-41 mum (P=.009). One year after the delivery of the prostheses (T(1)), the adaptation of the frameworks made with conventional casting was still significantly better (88 +/-6 mum versus 197 +/-94 mum, P=.03). CONCLUSIONS: Frameworks made with SLS showed worse clinical accuracy at the rest than frameworks produced with conventional casting.