Effect of Mouthrinses on Microtensile Bond-strength of CAD/CAM Ceramic Blocks

Objectives: To investigate the effect of two mouthwashes (Colgate^® PerioGard^®, LISTERINE®) on the microtensile bond strength (mTBS) of three different types of CAD/CAM dental ceramics (IPS e.max CAD, VitablocS® Mark ii, Lava™ Plus High Translucency) cemented to human dentin using two types of resin cement.

Methods: Porcelain blocks (4×7.5×7.5mm) prepared from three different types of CAD/CAM dental ceramic were luted to human dentin using two types of resin cements: (1)RelyX™ Ultimate (RXUL); (2)RelyX™ Unicem (RXUN). After 24 hours of storage in distilled water, the bonded specimens were sectioned into 1 mm thick slabs and further into 1mmX1mm beams. A total of 192 beams were obtained, divided into 6 groups according to ceramic block and cement type. Each group was divided into 4 sub-groups (n=8), according to storage medium as follow: (1)Immediate testing with no storage; (2)Two weeks storage in distilled water at 37°C; (3)Two weeks storage in distilled water at 37°C and rinsed twice/day for 30 seconds with LISTERINE^®; (4)Two weeks storage in distilled water at 37°C and rinsed twice/day for 30 seconds with Colgate^® PerioGard^®. The beams were stressed to failure under tension at crosshead speed of 0.5mm/min in microtensile tester. The modes of failure were evaluated using stereomicroscope at X30. Data were statistically-analyzed with three-way ANOVA and Tukey’s tests (P<0.05).
Results: Use of mouthwashes decreased the microtensile bond strength but not significantly (P>.05), whereas the type of ceramic block and resin cement used both had significant effects (P≤.001). In overall, failure mode was found to be adhesive in 62%, cohesive in 5% and mixed in 32% of the specimens.

Conclusions: Bond strength of CAD/CAM dental ceramics cemented to human dentin was significantly affected by type of ceramic block and resin cement but not by use of mouthwashes.