Composite resins are cured by mixing multifunctional monomers and silane-treated glass powder. Physical properties have been markedly improved by advancing the polymerization method and justifying the filler particle size and distribution. Among the physical properties, compression, diametral compression, and direct tensile tests are used to evaluate mechanical properties, but the three-point bending test may be the most practical. Thermal cycling is used as an accelerated degradation test for composite resins；however, storage in high-temperature water using a Soxhlet extraction device is also considered to be effective. Composite resin blocks for CAD/CAM are commercially available, but their flexural strength is decreased by immersion in water for 7 days and thermal cycling. Wear tests of composite resins showed that the amount of wear varied between two-body wear and three-body wear with poppy seeds and PMMA, and composite resin blocks for CAD/CAM generally showed less wear than those for restorative composite resins.

Additive manufacturing technology as new applications for the dental fields has expanded rapidly in recent years. The purpose of this research was to investigate the effects of printing parameters, including layer thicknesses and printing orientations, on the mechanical properties of vat photopolymerization-based additively manufactured parts by hardness tests using a dynamic ultra-micro hardness tester, and three-point bending test using a universal testing machine. In addition, the effects of these parameters (layer thicknesses and printing orientations) on the accuracy of the parts were examined. The results showed that printing parameters affected the dynamic hardness, indentation elastic modulus, flexural strength, and flexural modulus. The layer thicknesses affected the shrinkage and expansion of the 3D printed cubic parts. Moreover, differences in layer thickness affected the morphology of the 3D printed abutment teeth, especially in the finish line.

This study investigated the the effects of fluoride from the fluoride-releasing composite resins on the biological activities of Streptococcus mutans. The fluoride concentrations released from two types of the fluoride-releasing composite resins were both approximately 5 ppm. The released fluoride did not influence the proliferative activity of S. mutans. On the other hand, fluoride from the fluoride-releasing composite resins significantly inhibited biofilm formation, metabolic activity, and lactic acid production of S. mutans. Moreover, the fluoride from the fluoride-releasing composite resins inhibited enolase activity, which is involved in lactic acid production of S. mutans, but not glucosyltransferase (GTF) activity, which is involved in adhesion and biofilm formation of S. mutans. These results suggest that low concentrations of fluoride from the fluoride-releasing composite resins may exert caries-preventive effects by inhibiting the biological activities of S. mutans.