Bond Integrity and Surface Topography of Orthodontic Metal Brackets to Ceramic and Polymer-Based Restorations. An In-Vitro Study Design

Abstract

The present laboratory study aimed to assess shear bond strength (SBS) of orthodontic metal brackets bonded to different ceramic and polymer-based restorations after artificial aging. Eighty metal brackets were bonded using Transbond-X to eighty disks which were fabricated using five different ceramic and polymer-based materials (n = 16): group LD: lithium disilicate ceramic, group LS: zirconia-reinforced lithium silicate ceramic, group PI: polymer-infiltrated ceramic, group FC: feldspathic ceramic, and group PM: Polymethyl methacrylate PMMA. Bonded specimens were stored in distilled water (37 °C) for 24 h before they underwent 37,500 thermal cycles between 5 °C and 55 °C. After storage, the SBS was performed using a universal testing machine. Then, the data was analyzed using one-way analysis of variance (ANOVA) and Tukey’s test (α = 0.05). A 2-dimensional topographic analysis of the specimens was performed using atomic force microscopy. The Adhesive Remaining Index (ARI) was also evaluated at 50x magnification. A significant difference was observed between SBS means in the different groups’ materials (P < 0.05). The outcomes of the LD and LS groups were similar (17.55± 0.63 MPa and 18.26±0.33 MPa) but different from those of the PM, PI, and FC groups (15.23±0.29 MPa, 14.22 ±0.56 MPa, and 12.68 ±0.86 MPa). For FC group, however, it provided statistically significantly lower SBS than the other groups. There was predominance of score 3 for ARI in all groups. The type of dental substrate has a significant influence to the shear bond strength of the metal brackets.