SiO2-nanocomposite film coating of CAD/CAM composite resin blocks improves surface hardness and reduces susceptibility to bacterial adhesion.

Composite resin blocks for computer-aided design/computer-aided manufacturing (CAD/CAM) applications have recently become available. However, CAD/CAM composite resins have lower wear resistance and accumulate more plaque than CAD/CAM ceramic materials. We assessed the effects of SiO2-nanocomposite film coating of four types of CAD/CAM composite resin blocks: Cerasmart, Katana Avencia block, Lava Ultimate, and Block HC on surface hardness and bacterial attachment. All composite blocks with coating demonstrated significantly greater Vickers hardness, reduced surface roughness, and greater hydrophobicity than those without coating. Adhesion of Streptococcus mutans to the coated specimens was significantly less than those for the uncoated specimens. These reduced levels of bacterial adherence on the coated surface were still evident after treatment with saliva. Surface modification by SiO2-nanocomposite film coating has potential to improve wear resistance and susceptibility to plaque accumulation of CAD/CAM composite resin restorations.

Wear resistance of a modified polymethyl methacrylate artificial tooth compared to five commercially available artificial tooth materials.

STATEMENT OF PROBLEM: Wear resistance is a limitation of artificial denture teeth. Improving the wear resistance of conventional artificial denture teeth is of value to prosthodontic patients. PURPOSE: The purpose of this in vitro study was to evaluate the wear resistance and hardness of modified polymethyl methacrylate artificial denture teeth compared to 5 commercially available artificial tooth materials. MATERIAL AND METHODS: This study evaluated 180 artificial denture teeth (6 groups) that included 3 groups of conventional artificial teeth (MajorDent, Cosmo HXL, and Gnathostar), 2 groups of composite resin artificial teeth (Endura and SR Orthosit PE), and 1 group of modified surface artificial teeth. The flattened buccal surface of each tooth (n=15) was prepared for investigation with the Vickers hardness test and the elucidate wear test (n=15) by using a brushing machine. Each group was loaded for 18,000 cycles, at 2 N, and 150 rpm. The wear value was identified with a profilometer. The data were statistically analyzed by using 1-way ANOVA and post hoc Turkey honestly significant difference tests (α=.001). The tribologies were observed under a scanning electron microscope, and the cytotoxicities were evaluated by MTT assay. RESULTS: The Vickers hardnesses ranged from 28.48 to 39.36. The wear depths and worn surface area values ranged from 1.12 to 10.79 µm and from 6.74 to 161.95 µm(2). The data revealed that the modified artificial denture teeth were significantly harder and exhibited significantly higher wear resistance than did the conventional artificial teeth (P<.001). The scanning electron microscopic images revealed cross sections of the conventional artificial denture teeth with intensively worn surface areas after brushing. The cytotoxicity test revealed 97.85% cell viability, which indicates the nontoxicity of the modified surface of this material. CONCLUSIONS: Within the limitations of this study, the polymethyl methacrylate modified surface artificial denture teeth was not significantly different from that of the composite resin artificial denture teeth, with the exceptions that the surface was harder and more wear resistant.