Is There a Correlation Between Physical Properties and Film Thickness of Dual- and Photo- polymerized Luting Resins and CAD/CAM-Dentin Micro-Tensile Bond Strength?

Abstract

Objective To correlate µTBS of photo- and dual-polymerized luting resins with film thickness (FT), Vicker's hardness (HV) and ultimate-tensile strength (UTS).Methods Human molars (N = 30) were divided (6-groups) according to: 1: Luting resin: Dual- [Bifix QM, (BF)], or photo-polymerized [GrandioSo Heavy Flow (GHF) and VisCalor Bulk (VB)] and 2: Adhesive mode (Optibond Universal): Etch-and-rinse (ER) or self-etching (SE). CAD/CAM blocks (7x7x4mm3) were air-abraded (50µm Al2O3/10s/0.2MPa) and silanated. For ER, dentin was etched (15s), rinsed (30s), and blot-dried. For both modes, adhesive was applied (20s), air-dried (5s) and photo-polymerized (10s). Sticks (1x1mm2) were aged either for 24-hours or for 6-months. Sticks were pulled in tension (1mm/min). Debonded sticks were evaluated for failure mode. For FT, nine-bonded slabs/each cement were evaluated. For UTS, eight-hourglass specimens/each cement were tested. For HV, 5-discs/each cement were evaluated using Vicker’s hardness tester. Data were analysed using ANOVA/Pearson's correlation tests (α = 0.05).Results No correlation between µTBS/HV was revealed (P > 0.05). Positive correlation between µTBS/FT and µTBS/UTS (p < 0.05) were observed. Three-Way ANOVA revealed all experimental factors had significant effect on µTBS (p < 0.05). The VB showed significant lower µTBS (20.8 ± 9.3MPa). The ER mode showed higher µTBS (26.0 ± 10.9MPa), and 24-hours revealed the higher µTBS (27.4 ± 10.0MPa). Mixed failure was the predominate type (42.51%). The VB showed the highest FT (122.2 ± 11.9µm). The GHF revealed higher UTS and HV (112.5 ± 19.7MPa and 91.6 ± 0.4Kgf respectively).Conclusions Photo-polymerized flowable resin can substitute dual-polymerized cement for CAD/CAM composite bonding.Clinical relevance: Photo-polymerized flowable composite can replace the dual-polymerized resin cement one to bond CAD/CAM composite to dentin.