A systematic review of shear bond strength of sixth- and fourth-generation adhesives in primary teeth

Background: The use of tooth-colored restorations, particularly composite resins, in the treatment of primary teeth has become increasingly common. The durability and clinical success of these restorations largely depend on the adhesive system and its application protocol. Therefore, this study aimed to systematically review the literature comparing the shear bond strength of sixth-generation self-etch adhesives with that of fourth-generation etch-and-rinse adhesives in primary teeth. Materials and Methods: A comprehensive search was conducted in PubMed, Scopus, and Cochrane databases using relevant keywords. Out of 162 initially identified studies, 72 in-vitro studies comparing the shear bond strength of sixth- and fourth-generation adhesives on human primary teeth were screened. After assessing eligibility based on study objectives, population, sample selection, participation rate, available variables, data collection methods, statistical analyses, and results, five studies underwent full-text analysis. Ultimately, four studies met the inclusion criteria for this systematic review. Results: No statistically significant differences were observed in the shear bond strength between the two adhesive systems. However, minor variations were noted. Moreover, none of the included studies evaluated the long-term performance of these adhesives. Conclusion: Despite the high heterogeneity and risk of bias among the included studies, the evidence suggests that fourth-generation adhesives may exhibit slightly better shear bond strength compared to sixth-generation self-etch systems in laboratory settings. Nonetheless, due to reduced application time and technique sensitivity, self-etch systems may be preferable for pediatric patients.