In vitro evaluation of marginal and internal adaptation of class II CAD/CAM ceramic restorations with different resinous bases and interface treatments

This in vitro study evaluated the influence of different composite bases and surface treatments on marginal and internal adaptation of class II CEREC CAD/CAM ceramic inlays, before and after simulated occlusal loading. Thirty-two IPS Empress CAD class II inlays (MO or OD) (n = 8/group) were placed on third molars, with margins 1 mm below the cementum-enamel junction (CEJ), following different cavity treatments. These treatments were non-liner (control group), a flowable composite liner (Premise flow) sandblasted or treated with soft air abrasion and a restorative composite liner (Premise) sandblasted. The restorations were then luted with Premise. All specimens were submitted to 1,000,000 cycles with a 100-N eccentric load. The tooth restoration margins were analysed semi-quantitatively by SEM pre- and post-loading. The internal adaptation was also evaluated after test completion. The percentage of satisfactory marginal adaptation varied from 75 to 87 % pre-loading and 62 to 72 % post-loading in occlusal enamel, from 71 to 83 % pre-loading and 52 to 63 % post-loading in proximal enamel, and from 68 to 88 % pre-loading and 43 to 66 % post-loading in cervical dentin. There were no significant differences among groups. The percentages of satisfactory tooth-composite internal adaptation varied from 81 to 98 % in occlusal dentin, from 63 to 90 % in axial dentin, and from 71 to 84 % in cervical dentin without any statistical difference. The results of the present study support the use of flowable or restorative composites as a liner underneath ceramic CAD/CAM inlays, producing marginal and internal adaptation which is not different from restorations placed directly on dentin. Soft air abrasion proved not to be different from sandblasting for treating cavities before cementation. The results of this in vitro test validate the increasing use of a flowable base/liner underneath CAD/CAM ceramic inlays to optimise tissue conservation and clinical procedures; in this case, soft air abrasion is recommended as a pre-cementation step.