Does artificial aging affect mechanical properties of CAD/CAM composite materials.

PURPOSE: The purpose of this study was to determine the flexural strength and Weibull characteristics of different CAD/CAM materials after different in vitro aging conditions. METHODS: The specimens were randomly assigned to one of the six in vitro aging conditions: (1) water storage (37 degrees C, 3 weeks), (2) boiling water (24h), (3) hydrochloric acid exposure (pH: 1.2, 24h), (4) autoclave treatment (134 degrees C, 200kPa, 12h), (5) thermal cycling (5000 times, 5-55 degrees C), (6) cyclic loading (100N, 50,000 cycles). No treatment was applied to the specimens in control group. Three-point bending test was used for the calculation of flexural strength. The reliability of the strength was assessed by Weibull distribution. Surface roughness and topography was examined by coherence scanning interferometry. Evaluated parameters were compared using the Kruskall-Wallis or Mann-Whitney U test. RESULTS: Water storage, autoclave treatment and thermal cycling significantly decreased the flexural strength of all materials (p<0.05), whereas HCl exposure or cyclic loading did not affect the properties (p>0.05). Weibull moduli of Cerasmart and Lava Ultimate were similar with control. Vita Enamic((R)) exhibited similar Weibull moduli in all aging groups except the HCl treated group (p>0.05). R(a) values of Cerasmart and Lava Ultimate were in the range of 0.053-0.088mum in the aged groups. However R(a) results of Vita Enamic((R)) were larger than 0.2mum. CONCLUSIONS: Flexural strength of newly developed restorative CAD/CAM materials was significantly decreased by artificial aging. Cyclic loading or HCl exposure does not affect to the flexural strength and structural reliability of Cerasmart and Lava Ultimate.