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Effect of Etching Time and Technique on Bonding to Machinable Glass Ceramic

Objectives: the purpose of this in-vitro study was to investigate the effect of different surface treatment and various etching times on the shear bond strength of machinable glass ceramic using 2 resin cements. Materials and Methods: A total of 64 ceramic samples (10x12x3.5 mm) were fabricated from (IPS e.max CAD) using CAD/CAM technology. Ceramic samples were divided into two main groups (n=32) according to surface treatment: Hydrofluoric acid followed by Monobond N application or Monobond Etch and prime. According to the etching time, either 60 or 120 sec each main group was divided into two subgroups (n=16). Composite resin discs were fabricated (4mm diameter x 3mm thickness) dimensions. Each subgroup was further subdivided into two divisions (n=8) according to type of luting agent used, either adhesive resin cement (Multilink N) or self-adhesive resin cement (G-CEM LinkAce). Bonded specimens were stored in water bath at 37°C for 5 months then exposed to 10,000 thermal cycles. Universal testing machine was used to record the shear bond strength values for each specimen. Failure analysis was performed using a stereomicroscope (10x) and a scanning electron microscope (SEM). Results: SBS values ranged between 11.9 and 15.1 MPa in groups treated with HF pluse Monobond N and between 13.9 and 15.8 MPa in groups treated with MEP. ANOVAs test showed statistically significant difference between the two etching agents used for surface treatment as well as luting agent used for the bonding. However, etching time factor had no statistically significant difference. Moreover, the interaction between the factors had no statistically significant difference P (≤0.05). Most of specimens exhibited cohesive and mixed failure mode. Conclusions: MEP showed comparable SBS results to the combination of HF and Monobond N after artificial aging. Etching time had no effect on the SBS results. The adhesive resin cement showed higher SBS values compared to self-adhesive resin cement regardless of the other factors.