Hydroxyapatite coating effect on the bond strength between CAD/CAM materials and a resin cement

The purpose of this study was to evaluate the bond strength between CAD/CAM materials and a resin cement using hydroxyapatite coating as a surface treatment method. Different surface treatments (Control, no treatment-C; Sandblasting-SB; Hydrofluoric acid etching-HF; applying tooth desensitizer-TeM; applying topical crème-ToM, HAp coating with Pulse Laser Deposition technique-PLD) were applied to three different CAD/CAM materials (LAVA Ultimate, VITA Enamic, and Cerec Blocs). After surface treatments, a universal adhesive (Single Bond Universal, 3M ESPE) was applied and adhesive resin (Rely X Ultimate, 3M ESPE) were cemented on each material surface using plastic tubes (4 mm in diameter). The shear bond strength values were measured using a universal testing machine. Scanning electron microscope analysis were performed to evaluate failure modes and effects of surface treatments. Obtained data were statistically analyzed using two-way ANOVA and Tukey's post hoc test (p = 0.05). The bond strength of PLD groups were significantly higher than other groups in resin-ceramics (p < 0.05). In Cerec Blocs, HF resulted significantly higher bond strength than other groups (p < 0.05). SEM analysis of surface treatment methods (except TeM and ToM) revealed an increase in surface alterations compared to control groups. Failure modes were dominantly adhesive in groups C, TeM, and ToM, whereas mostly mix or cohesive failures were observed in PLD, HF, and SB. Hydroxyapatite coating with PLD technique exhibited promising bond strength results for CAD/CAM resin-ceramics. HAp coating can be used as a replacement for hydrofluoric acid etching and sandblasting in CAD/CAM resin-ceramic materials to obtain better bond strength values.