[Effect of different support angles on the fitness of removable partial denture framework fabricated using selective laser melting technique].

Objective: To evaluate the fitness of bilateral free-end dentition defect removable partial denture framework fabricated by selective laser melting (SLM) technique with different support angles. Methods: After the control group has been set to eliminate the system error, and according to the standard model of bilateral mandibular posterior teeth loss, eighteen titanium alloy removable partial denture frameworks fabricated by SLM technology were divided into 3 groups with support angles of 0° (horizontal group), 45°(45° group) and 90° (vertical group). Plaster cast with duplicated structure of tissue surface of the removable partial denture (RPD) framework was obtained. A three-dimensional scanner was used to scan original and duplicated plaster casts. The gaps between framework and the model in different parts were analyzed using Geomagic Qualify software to evaluate the fitness of the framework with visual method. Results: The framework fits on the plaster model completely, and its tissue surface fitted on the plaster model well. The deviation between frameworks and plaster casts was calculated as follow: the total deviations of the horizontal, 45°, and vertical group were (0.146±0.017), (0.182±0.015) and (0.185±0.022) mm respectively. The mean deviation of the horizontal group was significantly less than those of the 45° group and the vertical group (P<0.05). Moreover, there was no significant difference in the total deviation between the 45° group and the vertical group. The total deviation of occlusal rest of the horizontal group was significantly less than that of the 45° group (P<0.05). However, no significant difference was detected in the deviation of occlusal rest among the vertical group, the horizontal group, and the 45° group (P>0.05). There was no significant difference in the deviation of occlusal rest among the vertical group, the horizontal group, and the 45° group. The deviation of clasp of the horizontal group was significantly smaller than those of the 45° group and the vertical group (P<0.05). Whereas, there was no significant difference in the deviation of clasp between the 45° group and the 90° group (P>0.05). No significant difference was found in the deviation of lingual bar among the three groups (P>0.05). Conclusions: Among the three kinds of bilateral free-end dentition defect RPD framework fabricated by SLM in different support angles, horizontal printing was proved to reach the minimal deviation, even though the fitness of all three kinds of frameworks can fullfil clinical requirements according to previous studies.