Enamel Deproteinization with Sodium Hypochlorite: Effects on Ceramic Bracket Bond Strength

To assess the efficiency of different concentrations of sodium hypochlorite (NaOCl) on the bonding of ceramic brackets to dental enamel using different bonding protocols. Ceramic, a polycrystalline bracket, was bonded to 90 extracted bovine incisors using primer + Transbond XT (P+TXT); Optibond S adhesive + Transbond XT (OS+TXT), and OS + Orthocem (OS+OC). Three concentrations of NaOCl (0%, 2.5%, and 5.25%) were used for each material, resulting in nine experimental groups (n=10). The shear bond strength (SBS) assay was performed on a universal testing machine. The surface morphology of the enamel and tooth/bonding material interface was examined under a scanning electron microscope. Kruskal-Wallis and Dunn's tests were performed to compare the non-parametric data (ARI scores). SBS data were analyzed using a generalized linear model. All analyses were performed using the R program and with a significance level of 5%. No significant differences in SBS between the groups with different concentrations of NaOCl (p>0.05). OS+OC group yielded the lowest bond strength values (3.35 MPa_0%, 4.90 MPa_2.5%, 4.68 MPa_5.25%) compared to the other groups, regardless of NaOCl (p<0.05). No significant difference between the materials regarding the ARI score (p>0.05). OS+TXT-5.25% showed significantly higher scores (14.4 MPa) than OS+TXT-2.5% (9.17 MPa) (p<0.05). The surface morphology analysis revealed a change in the etching pattern for types 1 and 2 when NaOCl was used. The different concentrations of NaOCl previously applied onto the enamel surface did not enhance bond strength. OS+OC should not be recommended for bonding with fixed ceramic orthodontic devices.