Evaluation of the effects of different deproteinization protocols on the bond strength of resin-based restorative materials in molar incisor hypomineralization-affected teeth

Molar-incisor hypomineralization (MIH) presents a significant clinical challenge, particularly due to the bonding difficulties between resin-based restorative materials and tooth hard tissues, stemming from the increased organic content of the enamel. This study aimed to evaluate the effects of sodium hypochlorite (NaOCl), a well-established deproteinizing agent, and hypochlorous acid (HOCl), a potential alternative, applied at various concentrations and durations, on the bond strength of resin-based restorative materials. Under in-vitro conditions and ethical approval, 128 extracted molars exhibiting moderate MIH were randomized into eight deproteinization protocol groups: (a) 1% NaOCl for 15 seconds, (b) 1% NaOCl for 30 seconds, (c) 6% NaOCl for 15 seconds, (d) 6% NaOCl for 30 seconds, (e) 50 ppm HOCl for 15 seconds, (f) 50 ppm HOCl for 30 seconds, (g) 100 ppm HOCl for 15 seconds, and (h) 100 ppm HOCl for 30 seconds. After the occlusal one-third of each tooth surface was standardized using a precision cutting device, the respective deproteinization protocols were applied. Subsequently, 37% phosphoric acid etching was performed for 20 seconds, followed by universal bonding application for 20 seconds. Composite restorations were then prepared within cylindrical molds, and shear bond strength testing was conducted using a crosshead speed of 0.5 mm/min until failure, with values recorded in Newtons and Megapascals (MPa). Statistical analyses included independent t-tests for two-group comparisons and one-way ANOVA with Bonferroni post hoc tests for multi-group comparisons, with significance set at p ≤ 0.05. The results revealed statistically significant differences within the 50 ppm HOCl group between the 15- and 30-second subgroups (p = 0.033), as well as among all 30-second groups (p = 0.002). Post hoc analyses indicated that the bond strength for 50 ppm HOCl applied for 30 seconds was significantly lower compared to other deproteinization agents (1% NaOCl, 6% NaOCl, and 100 ppm HOCl). Despite these findings, HOCl demonstrated promising outcomes comparable to NaOCl, which is considered the gold standard due to its proven deproteinizing efficacy. HOCl offers potential advantages, particularly for pediatric patients, as its less alkaline nature, reduced cytotoxicity, and more tolerable taste and odor make it a suitable alternative. However, further randomized clinical trials are warranted to validate the long-term clinical efficacy of HOCl for deproteinization in MIH-affected teeth.