EXPERIMENTAL SILANE PRIMER AND GRIT-BLASTING DISTANCE IN ORTHODONTIC BONDING OF ZIRCONIA SURFACES

The objective of this study is to evaluate the effect of an experimental adhesive silane blend system in achieving optimal orthodontic bonding to zirconia surfaces. Also, the effect of the sandblasting distance on the adhesion strength and surface roughness of the zirconia bonding surface was determined. A total of 180 zirconia specimens were used for 3 test groups (n=60), and then grit-blasted with various distance (5mm, 10mm and 15mm). The grit-blasted specimens were allocated to three silanizations (n=30): with 1.0 vol% 3 methacryloyloxypropyltrimethoxy-silane (EP1) or their blends with 0.5% (EP2), and 1.0 vol% (EP3) 1, 2-bis-(triethoxysilyl) ethane (all in ethanol/water). Premolar brackets were bonded to zirconia specimen surfaces using TransbondTM XT adhesive resin. Next, ten specimens from each subgroup were subjected to thermo-cycling of 5000 cycles. Adhesion strength tests were performed at baseline (dry), and after thermo-cycling. The grit-blasted specimens were studied by scanning electron microscopy (SEM) and their surface roughness was evaluated. Contact angles and wettability of the primers on the zirconia surface was determined. The highest surface roughness was 0.69 ± 0.0097 μm for specimens grit-blasted at a distance of 5 mm (group 1), and the lowest surface roughness was 0.29 ± 0.0078 μm for the control specimens. Significant differences in the mean surface roughness were observed between the study groups (P ˂ 0.05). ANOVA showed a significant influence of the grit-blasting distance, silane blend and artificial aging on the shear bond strength values (P ˂ 0.05). The highest adhesion strengths were obtained for baseline specimens irrespective of the grit-blasting distance or the silane primer blend system used. The water contact angle of the control zirconia specimen was 53.5° and the contact angle ranged between 3-7° after primer coating. Grit-blasting at 10mm and silane primer blend system of 1.0 vol% 3-methacryloyloxy-propyltrimethoxysilane + 0.5 vol% 1,2-bis- (triethoxysilyl) ethane demonstrated optimal orthodontic bonding with least surface damage to the zirconia surface.