Effect of immediate-dentin-sealing application on bonding of metal-free CAD/CAM onlay-restoration

Objectives: The purpose of this study was to examine the effect of immediate-dentin-sealing application on the bonding of metal-free CAD/CAM onlay-restoration under in-vitro cyclic-load-stress condition.
Methods: Standardized MODB cavities were prepared in 16 extracted human lower molars. The intra-cavity dentin walls of a half cavity-specimens were pretreated with an all-in-one adhesive system (Scotchbond Universal Adhesive, 3M ESPE) and sealed immediately (S+) with a flowable resin composite (Filtek Supreme Ultra Flowable Restorative, 3M ESPE). The other cavity-specimens were not sealed (S-). Optical-impressions for all cavities were taken by CEREC AC Omnicam (ver.4.3), and then CAD/CAM onlay was milled from a hybrid-resin-composite-block (L: Lava Ultimate, 3M ESPE) or a popular ceramic-block (V: VITABLOCS Mark II, VITA) by CEREC MC XL (SIRONA Dental Systems), eight each. Each onlay was cemented to individual cavity with an adhesive resin-cement (RelyX Ultimate, 3M ESPE). All restored specimens were subjected to cyclic-load-stress (157N x 300,000times at 37°C water) simulating intra-oral environment. Four standardized beam specimens were trimmed from each restored specimen, and micro-tensile bond strength (μ-TBS) to pulpal dentin wall were measured. The data of μ-TBS were examined using Student’s t-test and Weibull analysis.
Results: The μ-TBS(SD) of S+/S- restorations in MPa were L; 26.6(6.5)/21.2(6.1), V; 5.1(1.2)/3.5(1.6). The μ-TBS of S+ CAD/CAM restoration was statistically greater than the value of S- restoration, regardless of milling-block material. Weibull modulus (Wm) of S+/S- restorations were L; 3.24/3.22, V; 4.62/2.27. For V-restoration, the Wm-value of S+ specimens was significantly bigger than that of S- specimens. No difference was recognized in Wm for L-restoration between S+ and S- conditions.
Conclusions: Immediate-dentin-sealing application was effective to obtain excellent intra-cavity bond strength and good bonding reliability of metal-free CAD/CAM onlay-restoration compared with no-sealing.