Comparative Evaluation of Shear Bond Strength of Seventh and Eighth Generation Bonding Agents with and without Additional Acid Etching: An In Vitro Study

Introduction: Adhesive dentistry has advanced with the development of newer generations of bonding agents that simplify clinical procedures and enhance bond strength. Self-etch adhesives – specifically seventh- and eighth-generation bonding agents – eliminate the need for separate etching. However, evidence suggests that supplemental phosphoric acid etching may improve their performance. This in vitro study aimed to evaluate and compare the shear bond strength (SBS) of seventh- and eighth-generation bonding agents with and without additional acid etching. Materials and Methods: Eighty freshly extracted human maxillary premolars were selected, flattened to expose dentin surfaces and embedded in acrylic resin blocks. The teeth were randomly divided into four groups ( n = 20 each): Group IA – seventh-generation adhesive with acid etching; Group IB – seventh-generation adhesive without acid etching; Group IIA – eighth-generation adhesive with acid etching and Group IIB – eighth-generation adhesive without acid etching. Bonding agents were applied as per the manufacturer’s instructions, followed by composite resin build-up using a Teflon mould. After 24 h of storage in distilled water at 37°C, SBS was measured using a universal testing machine. Data were statistically analysed using the SPSS software version 22.0, with P < 0.05 considered statistically significant. Results: Group IIA exhibited the highest mean SBS (26.71 megapascals [MPa]), followed by Group IA (21.31 MPa), Group IIB (20.06 MPa) and Group IB (16.94 MPa). The differences among all groups were statistically significant. Conclusion: Eighth-generation bonding agents showed superior SBS compared to seventh-generation agents. Additional phosphoric acid etching significantly improved the bond strength of both adhesive systems.