Objectives
To determine the effect of curing mode and restoration-surface pre-treatment on the micro-tensile bond strength (渭TBS) to dentin.
Methods
Sandblasted CAD/CAM composite blocks (LAVA Ultimate, 3M ESPE) were cemented to bur-cut dentin using either the etch & rinse composite cement Nexus 3 (鈥楴X3鈥? Kerr) with Optibond XTR (鈥榅TR鈥? Kerr), or the self-etch composite cement RelyX Ultimate (鈥楻XU鈥? 3M ESPE) with Scotchbond Universal (鈥楽BU鈥? 3M ESPE). All experimental groups included different 鈥榗uring modes鈥?(light-curing of adhesive and cement (鈥楲L鈥?, light-curing of adhesive and auto-cure of cement (鈥楲A鈥?, co-cure of adhesive through light-curing of cement (鈥楢L鈥?, or complete auto-cure (鈥楢A鈥?) and different 鈥榬estoration-surface pre-treatments鈥?of the composite block (NX3: either a silane primer (Kerr), or the XTR adhesive; RXU: either silane primer (RelyX Ceramic Primer, 3M ESPE) and SBU, or solely SBU). After water-storage (7 days, 37 掳C), the 渭TBS was measured. Additionally, the degree of conversion (DC) of both cements was measured after 10 min and after 1 week, either auto-cured (21 掳C/37 掳C) or light-cured (directly/through 3-mm CAD/CAM composite).
Results
The linear mixed-effects model (伪 = 0.05) revealed a significant influence of the factors 鈥榗uring mode鈥?and 鈥榗omposite cement鈥? and a less significant effect of the factor 鈥榬estoration-surface pre-treatment鈥? Light-curing 鈥楲L鈥?revealed the highest 渭TBS, which decreased significantly for all other curing modes. For curing modes 鈥楢A鈥?and 鈥楢L鈥? the lowest 渭TBS and a high percentage of pre-testing failures were reported. Overall, DC increased with light-curing and incubation time.
Significance
The curing mode is decisive for the bonding effectiveness of adhesively luted composite CAD/CAM restorations to dentin.
