Bonding effectiveness of tooth-colored materials to resin cement provided by self-etching silane primer after short- and long-term storage

Statement of problem. Glass-ceramic materials are typically treated with hydrofluoric acid (HF) and silane to improve their bond to composite resin; however, HF may be harmful to human tissues and the integrity of the material, and its application is a technique-sensitive procedure. A novel self-etching ceramic primer has been introduced with the claim that it can solve those problems. However, independent scientific evidence regarding its performance is scarce. Purpose. The purpose of this in vitro study was to evaluate the effect of self-etching silane primer on glass-ceramic surface roughness and on long-term bonding between glass-ceramic and composite resin cement. Material and methods. Plates of 3 materials (n=10), lithium disilicate glass-ceramic (LDC) (IPS e.max CAD), leucite-based glass-ceramic (LEU) (IPS Empress CAD), and resin-modified ceramic (PIC) (VITA ENAMIC), were treated in the following ways: no treatment (C), HF (5%) applied during the recommended time for each material (HF), and self-etching ceramic primer (Monobond Etch & Prime [MBEP]). Surface roughness (Sa) was analyzed with a laser 3D profiler. Ceramic sticks were subjected to (n=20) no treatment (C); treatment with hydrofluoric acid plus silane (HF+S); and treatment with self-etching ceramic primer (MBEP) bonded to prepolymerized composite resin sticks with composite resin cement (Variolink II) and stored for 24 hours and 1 year (n=10). The assemblies were submitted to microtensile bond strength testing (mu TBS). Data were analyzed using ANOVA and the Tukey pairwise, post hoc test (alpha=.05). Failure pattern and surface and interface morphology were assessed using scanning electron microscopy. Results. Only individual factors resulted in statistically significant differences for both variables (material: P<.001; surface treatment: P=.020), interaction (P=.570). HF group (0.49 +/- 0.11 mu m) showed statistically higher roughness values (P <=.05) than control groups (0.44 +/- 0.97 mu m), while MBEP (0.48 +/- 0.11 mu m) was comparable with both. HF produced greater surface alterations than MBEP and C. PIC (0.60 +/- 0.051 mu m) exhibited significantly higher roughness values (P <=.05) than LDC (0.37 +/- 0.07 mu m) and LEU (0.45 +/- 0.04). Regarding mTBS, the general mean of PIC (24.6 +/- 10.1 MPa) was higher (P <=.05) than LEUs (14.7 +/- 6.7 MPa) and LDCs (13.1 +/- 4.8 MPa), while treatment groups HF+S (17.9 +/- 10.0 MPa) and MBEP (20.5 +/- 9.7 MPa) produced higher mu TBS values than control groups (14.2 +/- 5.5 MPa). Adhesive failure was associated with low mu TBS values and aged specimens, while cohesive failure within the composite resin-cement layer and mixed failures were associated with higher mu TBS values. Interface debonding was detected in C groups for LDC and LEU. PIC exhibited better interface stability. Conclusions. MBEP produced smoother surfaces than HF. HF+S and MBEP significantly improved ceramic and composite resin cement bonding.