Adhesion of metal brackets to glassy matrix and hybrid CAD/CAM materials after different physico-chemical surface conditioning

Abstract

This study compared the adhesion of metal brackets bonded to different CAD/CAM materials after various surface conditioning methods. CAD/CAM blocks (N=204, n=17 per group) of a) VITA Mark II (VM), b) IPS e.max CAD (IP), c) Lava Ultimate (LU), and d) VITA ENAMIC (VE) were conditioned with one of the following methods: C-Control: (fine diamond bur); CJ: (fine diamond bur+air-abrasion with 30 µm SiO 2 +silane), and HF: (fine diamond bur+9.5% hydrofluoric acid+silane). Metal brackets were bonded to the conditioned surfaces of the specimens, stored in artificial saliva for 24 h at 37°C and thermocycled (x1000). Subsequently, the brackets were debonded under shear in a Universal Testing Machine (1 mm/min). Failure types were analyzed under scanning electron microscope. Data were analyzed using two-way ANOVA and Tukey`s tests (α=0.05). Two-parameter Weibull distribution values, including the Weibull modulus, scale, and shape, were calculated. Mean bond strength (MPa) values were significantly affected by the surface conditioning method (p<0.001) but not the CAD/CAM material type (p=0.052).Bond strengths for all CJ and HF-conditioned specimens were two-fold higher (11.83±1.95 -9.44±1.63) than those for control specimens with all materials (4.73±0.93 -6.02±0.69). Lower mean values were obtained in LU-CJ (9.78±1.61) and LU-HF (9.44±1.63) than those for other groups (11.83±1.95 -10.93±1.33) groups (p<0.05). Weibull distribution showed higher shape values for VM-CJ (11.26) and VM-HF (8.87) than those for other groups (0.82-1.83). In control groups, exclusively adhesive and after conditioning mainly mixed failures were observed. Chairside silica coating or HF conditioning significantly improved metal bracket adhesion to both glassy matrix and hybrid CAD/CAM materials tested, with the most reliable adhesion being observed for feldspathic ceramic.

In vitro testing of shear bond strength of orthodontic brackets bonded to different novel CAD/CAM ceramics

“…These results were similar to a previous study by Dilber et al, 19 who found that the average SBS values were significantly influenced by the substrate treatment protocol but not the CAD/CAM substrate category.…”

Influence of different surface treatment on bonding of metal and ceramic Orthodontic Brackets to CAD-CAM all ceramic materials

“…Study results confirmed that surface roughening with a medium-grit bur was inadequate for enhancing bond strength across all the ceramic groups. Dilber et al [ 50 ] corroborated this observation; they recommended additional surface conditioning with HFA etching or silica coating after surface grinding with a diamond bur. Schmage et al [ 51 ] observed that roughening with a diamond bur without silane application resulted in reduced bond strength compared to HFA etching and sandblasting.…”