Fabrication and evaluation of Bis-GMA/TEGDMA resin with various amounts of silane-coated silica for orthodontic use.

The objective of this research was to fabricate a composite with an optimum filler level in a bisphenol-A-glycidyldimethacrylate (Bis-GMA) triethylene glycidal dimethacrylate (TEGDMA) resin for bonding of metallic orthodontic brackets to achieve the best handling characteristics with optimum bond strength and without compromising the mechanical properties of the adhesive. One-hundred and sixty extracted human premolars free of any detectable pathology or buccal surface alterations were collected and divided into four groups. In group 1 (control), the teeth were bonded with stainless steel brackets using Transbond XT. In groups 2, 3, and 4, the teeth were bonded with metal brackets using a Bis-GMA/TEGDMA resin with 80, 60, and 20 per cent by weight silane-coated silica of a spherical shape with a mean size of 0.01 μm. Shear bond strength (SBS) of the composites was determined and the adhesive remnant index (ARI) and enamel fracture post-debonding were assessed. According to one-way analysis of variance and Tukey's honestly significant difference (HSD) multiple comparison tests, the SBS of group 4 (10.54 MPa) was considerably less than that of groups 1 (26.1 MPa), 2 (25.5 MPa), and 3 (24.6 MPa). Chi-square analysis revealed that there was an insignificant difference in the incidence of enamel fracture between groups 1 and 2, while a significant difference was present between groups 1 and 2 and 3 and 4. An insignificant difference was also observed in the location of the adhesive failure between the four groups. While all the bonding adhesives tested can be safely used for bonding of brackets, 60 per cent filled Bis-GMA/TEGDMA was superior clinically due to its ease of handling and superior bond strength.