Microgap Formation between a Dental Resin-Matrix Computer-Aided Design/Computer-Aided Manufacturing Ceramic Restorative and Dentin after Various Surface Treatments and Artificial Aging

The potential formation and the size of microgaps at the material/dentin interface after various surface modifications of a resin-matrix computer-aided design/computer-aided manufacturing (CAD/CAM) ceramic following artificial aging was investigated. Fifty human third molars were used, and a resin-matrix CAD/CAM ceramic, Lava Ultimate, and a resin cement material, Rely X Ultimate, were tested. CAD/CAM blocks were sectioned, and each slab was luted on the tooth surface using the same resin cement. The surface material was modified using the following treatments: Group 1-no treatment (control); Group 2-hydrofluoric acid (HF) + silane; Group 3-air abrasion with Al2O3 particles (29 mu m); Group 4-air abrasion with Al2O3 particles (53 mu m); and Group 5-erbium, chromium:yttrium-scandium-gallium-garnet (Er,Cr:YSGG) (2780 nm) laser treatment. The specimens were submitted to thermocycling (5000 cycles: 5 & DEG;C-55 & DEG;C) and then transversely cut in the middle and examined using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). Larger microgaps were observed in the control and laser-treated groups, with no significant differences (p = 0.452). By contrast, the other three groups presented lower microgap formation, and in some cases, no microgaps were detected. Air-abrasion groups exhibited the lowest microgap formation (p < 0.05). Different surface modifications of the material presented significant differences in the formation of microgaps at the adhesive interface after artificial aging, implying differences in bond strengths among the groups. Air-abrasion pretreatments with Al2O3 particles presented more beneficial results regarding microgap formation.