Effect of Immediate-dentin-sealing on Bonding-behavior of CAD/CAM Restoration Under Cyclic-load-stress
Objectives: The purpose of this study was to examine the effect of immediate-dentin-sealing(IDS) on the bonding-behavior of CAD/CAM onlay restoration under cyclic-load-stress simulating intra-oral environment. Methods: Standardized MODP cavities were prepared in 32 extracted-human-upper-molars. The cavity specimens were divided into four IDS-applications, eight each; thin-layered IDS(T), slope-shaped IDS(S), base-shaped IDS(B) and non-IDS(N, as control). All cavities were scanned by CEREC AC Omnicam(SIRONA Dental Systems), regardless of IDS status. The IDS application was done using an all-in-one adhesive system(Scothbond Universal Adhesive, 3M ESPE) and a low-viscosity resin restorative(Filtek Supreme Ultra Flowable Restorative, 3M ESPE). Each CAD/CAM onlay was designed and then fabricated from a popular feldspathic ceramic block(VITABLOCS Mark II, VITA), by CEREC MCXL. Fabricated onlays were cemented with an adhesive resin cement system(PANAVIA V5, Kuraray Noritake Dental). The restored specimens were subjected to cyclic-load-stress(157N x 3 x 105 times at 37°C water). 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 were examined using one-way ANOVA, Tukey’s HSD test and Weibull analysis with a level of significance set at 0.05. Results: Pre-testing failure(ptf) was occurred in three specimens for T-restoration and two specimens for N-restoration. The mean values of μ-TBS in MPa, [Weibull modulus(Wm)] and the stress value in MPa for 10% probability of failure level{PF10:PF90} of T/S/B/N-restorations were 5.8[6.0]{4.8:8.0}/11.5[6.3]{8.7:14.1}/12.1[5.2]{8.5:15.5}/4.4[5.6]{3.4:5.9}. The μ-TBS was influenced by the IDS status. Wm of S-restoration was significantly greater than the value of B-restoration. The values of μ-TBS, PF10 and PF90 of T, S and B-restorations were significantly greater than those of N-restoration. Conclusions: The IDS-application significantly influenced the bonding-behavior of MODP CAD/CAM ceramic onlay restoration. The S-restoration demonstrated the highest performance in terms of bonding reliability and durability evaluated by both the Weibull parameters and ptf-occurrence under cyclic-load-stress simulating intra-oral environment.