Comparison of the flexural strength and marginal accuracy of traditional and CAD/CAM interim materials before and after thermal cycling

Statement of problem Limited information is available concerning the properties of computer-aided designed/computer-aided manufactured (CAD/CAM) interim materials. Purpose The purpose of this study was to investigate the flexural strength and marginal accuracy of 2 traditional bis-acryl composite resin interim materials (Protemp 4 and Structur 2 SC/QM) and 2 CAD/CAM interim materials (Teilo CAD and VITA CAD-Temp). Material and methods Standard specimens (25 × 2 × 2 mm) of the 4 materials were made (n=20). Each group contained 10 specimens fractured under 3-point loading in a universal testing machine with a cross-head speed of 1 mm/min. The other 10 specimens were subjected to 5000 thermal cycles (5°C and 55°C) before testing. Four groups of interim crowns were fabricated from the 4 materials on models of a prepared left maxillary first molar (n=10). Twenty-four hours after cementing the crowns, margin discrepancies were measured under a stereomicroscope. The crowns then were subjected to 5000 thermal cycles (5°C and 55°C), and the margin discrepancies were measured again. Results Teilo CAD showed the highest mean flexural strength of the 4 interim materials before and after thermal cycling, and VITA CAD-Temp showed the lowest ( P< .05). After thermal cycling, the flexural strength decreased significantly ( P< .05). The margin discrepancies were larger for the bis-acryl interim crowns than for the CAD/CAM crowns before and after thermal cycling ( P< .05). After thermal cycling, the margin discrepancies in the bis-acryl interim crowns were larger ( P< .05); however, no significant differences were found for the margin discrepancies in the CAD/CAM interim crowns ( P >.05). Conclusions CAD/CAM interim materials were stronger and had better marginal accuracy properties than bis-acryl materials, especially after thermal cycling.