Influence of Cement Thickness on Dentin-adhesion of CAD/CAM Nano-ceramic Block

Objectives: CAD/CAM crowns tend to be a loose fit, and it has often been reported dropping off the CAD/CAM crowns in clinical use. Recently, new self-adhesive resin cement, CSRZAF12 which improves the bond strength by pre-treatment with GCP-01 primer which has acceleration function of curing from the interface, was developed by GC-Corporation. The purpose of this study was to evaluate the influence of the cement thickness on the dentin adhesion of CAD/CAM nano-ceramic block using self-adhesive resin cements which are CSRZAF12 and SA-Luting-Plus(Kuraray-Noritake).
Methods: Bovine dentine surface was prepared with 600-grit SiC paper as a bonding substitute. Bonding area and cement space were regulated(3mm-diameter and 100μm- or 300μm-thickness, respectively) with a plastic sticker. All Cements were treated according to manufacturers’ instructions, and a specimen of CAD/CAM nano-ceramic block(1.5mm-thickness, CERASMART, A3LT, GC) was cemented(self-curing or light-curing-mode) to the substitute(n=5). The specimens were soaked in 37degC distilled water for 24hours, and then tensile bond strength(TBS) was measured(crosshead-speed:1mm/min.).
Results: In the table, asterisk(*) indicated significant difference between thickness on each product and curing-mode(T-test,*:p<0.05). CSRZAF12-without-GCP-01 and SA-Luting-Plus showed significantly lower bond strength in the case of light-curing-mode and 300μm cement thickness. TBS of CSRZAF12-with-GCP-01 has no significantly differences between different cement thicknesses on both curing mode.
Conclusions: These results suggest that it may make lower bond strength by higher polymerization shrinkage stress on light-curing-mode if cement layer is thicker. When combined with GCP-01, it is suggested that CSRZAF12 is cured from cement/dentin interface with its curing-acceleration function and curing reaction from the interface resists the polymerization shrinkage stress on light-curing-mode. It indicated that CSRZAF12-with-GCP-01 has a stable and excellent dentin adhesion to CAD/CAM nano-ceramic block regardless of the cement thickness and curing-mode.