This study investigates the flexural properties, Knoop hardness number (KHN), and wear behavior of computer-aided design and computer-aided manufacturing (CAD/CAM) resin blocks and compares these values with those of conventional resin composites for direct restoration (RCDs). Four CAD/CAM resin blocks and two RCDs are compared. Ten specimens per material are used to obtain the flexural properties according to ISO 6872 specifications, and five specimens per material are used for KHN measurement. For sliding impact wear testing, twelve specimens are prepared. Confocal laser scanning microscopy (LSM) is used to determine maximum facet depth and volume loss. Polished material surfaces and worn surfaces after wear testing are observed using scanning electron microscopy and LSM. While measured flexural properties and KHN are found to be material-dependent, CAD/CAM resin blocks exhibit higher wear resistance than RCDs. CAD/CAM resin blocks polymerized at high-pressure and high-temperature are found to exhibit wear behaviors far superior to those of RCDs.

The influence of an oxygen-inhibited layer (OIL) on the shear bond strength (SBS) to enamel and surface free-energy (SFE) of adhesive systems was investigated. The adhesive systems tested were Scotchbond Multipurpose (SM), Clearfil SE Bond (CS), and Scotchbond Universal (SU). Resin composite was bonded to bovine enamel surfaces to determine the SBS, with and without an OIL, of adhesives. The SFE of cured adhesives with and without an OIL were determined by measuring the contact angles of three test liquids. There were no significant differences in the mean SBS of SM and CS specimens with or without an OIL; however, the mean SBS of SU specimens with an OIL was significantly higher than that of SU specimens without an OIL. For all three systems, the mean total SFE (γS), polarity force (γSp), and hydrogen bonding force (γSh) values of cured adhesives with an OIL were significantly higher than those of cured adhesives without an OIL. The results of this study indicate that the presence of an OIL promotes higher SBS of a single-step self-etch adhesive system, but not of a three-step or a two-step self-etch primer system. The SFE values of cured adhesives with an OIL were significantly higher than those without an OIL. The SFE characteristics of the OIL of adhesives differed depending on the type of adhesive.