Effects of food-simulating solutions on the surface properties of two CAD/CAM resin composites

BACKGROUND: During clinical service, dental materials could experience chemical degradation due to exposure to different diet components which could affect their functions and longevity. So, the objective of this study was to investigate the effect of food simulating solutions on surface properties of two CAD/CAM dental resin composites. MATERIAL AND METHODS: Two CAD/CAM composites; a nano-hybrid and a resin nano-ceramic were machined into 2 mm plates then assessed at baseline for their surface roughness and microhardness. Each group was immersed into distilled water, ethanol and methyl ethyl ketone (MEK) for 15 days at 37oC. The surface properties were evaluated after one day, 10 and 15 days of immersion by a surface profilometer and Vickers microhardness tester, and finally the surface morphology was studied using scanning electron microscopy. RESULTS: At baseline, there was no significant difference in roughness between Teric CAD and Lava Ultimate, however, Lava Ultimate was significantly harder than Tetric CAD. Aging in ethanol had no significant effect on roughness and hardness of both the materials. Yet, Lava Ultimate showed significantly higher roughness and hardness compared to Tetric CAD. Immersion in MEK resulted in a significant increase in roughness of Lava Ultimate at 10 and 15 days. Neverthless, it caused a significant decrease in hardness of Tetric CAD at 10 and 15 days and Lava Ultimate at 10 days. Finally, water immersion caused a significant increase of roughness Tetric CAD. CONCLUSIONS: Exposure to different storage media variably affected the surface properties of CAD/CAM machinable composites. Both materials showed greater stability in surface properties when being immersed in ethanol than MEK. Hence, the surface deterioration suggests the advisability of more research involving increased immersion periods and involvement of thermocycling changes. Key words:Food simulating solutions, chemical degradation, nano-hybrid CAD/CAM composite, resin nano-ceramic CAD/CAM material, surface roughness, micro-hardness, surface morphology.