Investigating the Fracture Strength of Cad/Cam Pmma and Bis-Acrylic Resin in Temporary Crown Materials

Abstract

Aim: This study investigated the fracture strength of CAD/CAM polymethyl methacrylate (CAD/CAM PMMA) and Bis-acrylic resin temporary crowns to determine which material was more appropriate.

Materials and Methods: Chamfer and rounded shoulder preparations were made using a total of 80 stainless steel dies, with 20 in each group (cervical finish line width: 1.0 mm; taper degree: 6). CAD/CAM PMMA and Bis-acrylic resin were poured into the obtained left mandibular first molar silicone mold to cast temporary crowns. Their fracture resistances were then evaluated using an Instron device (speed: 1.0 mm/min), and the data were recorded.

Results: The lowest and highest fracture strength averages were found in the rounded shoulder preparation groups that used Bis-acrylic resin (1137.1 N) and CAD/CAM PMMA (1498.75 N). No significant differences were found between the chamfer preparation groups with CAD/CAM PMMA and Bis-acrylic resin (p > 0.05). However, the fracture resistances of Bis-acrylic resin and CAD/CAM
PMMA in rounded shoulder preparations were significantly different (p < 0.05).

Conclusion: CAD/CAM PMMA temporary crowns are recommended for rounded shoulder preparations as they had the highest average fracture resistance when compared to other materials.