Elsevier Science Acta Medica Okayama 0109-5641 33 3 2017 Sandblasting may damage the surface of composite CAD-CAM blocks e124 e135 EN Kumiko Yoshihara Centrer for Innovative Clinical Medicine, Okayama University Hospital Noriyuki Nagaoka Advanced Research Center for Oral and Craniofacial Sciences, Okayama University Dental School Yukinori Maruo Department of Occlusion and Removable Prosthodontics, Okayama University Hospital Goro Nishigawa Department of Occlusion and Removable Prosthodontics, Okayama University Hospital Masao Irie Department of Biomaterials, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences Yasuhiro Yoshida Department of Biomaterials and Bioengineering, Graduate School of Dental Medicine, Hokkaido University Bart Van Meerbeekf KU Leuven (University of Leuven), Department of Oral Health Sciences, BIOMAT & University Hospitals 　OBJECTIVE:　 CAD-CAM blocks to fabricate semi-direct and indirect restorations are available in different sorts of ceramics as well as composite. In order to bond restorations prepared out of composite blocks into tooth cavities, it is recommended to gently sandblast the surface prior to the application of a primer/adhesive. Today, the effect of sandblasting composite block surfaces has not thoroughly been investigated. In this study, the ultra-structure of composite CAD-CAM blocks was investigated with special attention to the effect of sandblasting on the surface topography and of silanization on the bonding performance. 　METHODS:　 Five different composite CAD-CAM blocks were involved. We correlatively investigated their structural and chemical composition using X-ray diffraction (XRD), energy dispersion spectroscopy (EDS), scanning electron microscopy (SEM) and (scanning) transmission electron microscopy ((S)TEM). The effect of sandblasting was also imaged in cross-section and at the interface with composite cement. Finally, we measured the shear bond strength to the sandblasted block surface with and without silanization. 　RESULTS:　 All composite blocks revealed a different ultra-structure. Sandblasting increased surface roughness and resulted in an irregular surface with some filler exposure. Sandblasting also damaged the surface. When the sandblasted composite blocks were silanized, superior bonding receptiveness in terms of higher bond strength was achieved except for Shofu Block HC. 　SIGNIFICANCE:　 Sandblasting followed by silanization improved the bond strength to composite CAD-CAM blocks. However, sandblasting may also damage the composite CAD-CAM block surface. For the composite CAD-CAM block Shofu Block HC, the damage was so severe that silanization did not improve bond strength. No potential conflict of interest relevant to this article was reported.