Shear bond strength of ceramic brackets bonded to surface-treated feldspathic porcelain after thermocycling.

Purpose: The aim of this study was to evaluate the effect of six different surface conditioning methods on the shear bond strength of ceramic brackets bonded to feldspathic porcelain. Materials and methods: A total of 60 feldspathic porcelain disks were fabricated and divided into six subgroups including 10 specimens in each. Specimens were first treated one of the following surface conditioning methods, namely, 37% phosphoric acid (G-H3PO4), 9.4% hydrofluoric acid (G-HF), grinding with diamond burs (G-Grinding), Nd:YAG laser (G-Nd:YAG), Airborne-particle abrasion (G-Abrasion). Specimens were also coated with silane without surface treatment for comparison (G-Untreated). A total of 60 ceramic brackets were bonded to porcelain surfaces with a composite resin and then subjected to thermocycling 2500x between 5 degrees C and 55 degrees C. The shear bond strength test was carried out using a universal testing device at a crosshead speed of 0.5 mm/min. Failure types were classified according to the adhesive remnant index. Analysis of variance and Tukey tests were used for statistical analysis (alpha=0.05). Microstructure of untreated and surface-treated specimens was investigated by scanning electron microscopy. Results: Using G-Abrasion specimens resulted in the highest shear bond strength value of 8.58MPa for feldspathic porcelain. However, the other specimens showed lower values: G-Grinding (6.51MPa), G-Nd:YAG laser (3.37MPa), G-HF (2.71MPa), G-H3PO4 (1.17MPa), and G-Untreated (0.93MPa). Conclusion: Airborne-particle abrasion and grinding can be used as surface treatment techniques on the porcelain surface for a durable bond strength. Hydrofluoric acid and phosphoric acid etching methods were not convenient as surface treatment methods for the feldspathic porcelain.