Evaluation of shear bond strength of orthodontic ceramic and metal brackets with zirconia: effects of adhesive systems and storage conditions

The current study assessed the shear bond strength of two orthodontic bracket materials to zirconia using two bonding approaches and two storage settings. Two bonding strategies were selected to bond metal and ceramic brackets to zirconia samples. Before being tested for Shear Bond Strength SBS, samples were either subjected to 5,000 thermocycles or kept in water for 24 h. Samples were divided into 8 Groups n = 10 represented as Group 1: Ceramic Brackets + HEMA-Free Bonding System + Water Storage, Group 2: Ceramic Brackets + HEMA-Containing Bonding System + Water Storage, Group 3: Metal Brackets + HEMA-Free Bonding System + Water Storage, Group 4: Metal Brackets + HEMA-Containing Bonding System + Water Storage, Group 5: Ceramic Brackets + HEMA-Free Bonding System + Thermocycling, Group 6: Ceramic Brackets + HEMA-Containing Bonding System + Thermocycling, Group 7: Metal Brackets + HEMA-Free Bonding System + Thermocycling, Group 8: Metal Brackets + HEMA-Containing Bonding System + Thermocycling. Several independent groups were compared using the Kruskal-Wallis test, and two independent groups were assessed using the Mann-Whitney U test. A P-value < 0.05 was deemed significant. Shear bond strength was significantly greater in ceramic than in metal 5.9 ± 2.6 vs. 4.9 ± 2.3, p = .026 and in 2-Hydroxyethyl methacrylate HEMA-containing systems compared to HEMA-free systems 6.1 ± 2.3 vs. 4.8 ± 2.4, p = .034. Water storage settings also yielded higher bond strength than thermocycling conditions 6.9 ± 1.8 vs. 3.9 ± 2.2, p < .001. The findings indicate that shear bond strength was significantly influenced by bracket material and adhesive system to zirconia. Additionally, storage settings play a crucial part in shear bond strength. Developing effective bonding techniques for orthodontic brackets and zirconia ceramic materials remains a major clinical obstacle.