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Long-term performance of flowable bulk-fill restorative systems in Class II restorations: a 7-year randomized
Érika Mayumi Omoto1, André Luiz Fraga Briso1, Anderson Catelan1
1Department of Restorative Dentistry and Endodontics, Araçatuba School of Dentistry, São Paulo State University, José Bonifácio St., Araçatuba, SP, 1193, Brazil.
Objectives:
This randomized, prospective, split-mouth study aimed to evaluate the clinical performance of flowable bulk-fill restorative systems in Class II restorations after 7 years of follow-up.
Methods:
Class II restorations were performed in 159 teeth according to the restorative systems: conventional microhybrid resin composite (PA - Peak Universal + Amelogen Plus, Ultradent); flowable bulk-fill and nanofilled resin composites (ABF - Adper Single Bond 2 + Filtek Bulk Fill Flow + Filtek Z350XT, Solventum); and flowable bulk-fill and microhybrid resin composites (XST - XP Bond + SDR + TPH3, Dentsply). Clinical performance was assessed using the USPHS criteria. Statistical analyses included Kaplan-Meier survival test, Log-rank test, Frailty Cox proportional-hazard model, Generalized Linear Mixed Model, and Generalized Estimating Equations (α=0.05).
Results:
A total of 76 restorations were evaluated after 7 years. No significant differences in survival rates were found among the groups. At the 7-year evaluation, both bulk-fill systems showed higher marginal discoloration than PA. A significant difference was observed between PA and ABF for surface texture, whereas XST did not differ from either group. For longitudinal comparisons, most parameters showed no significant differences over time. The XST group showed a significant change in marginal integrity between the 3- and 4-year follow-ups, which was maintained at the 7-year follow-up, whereas the ABF group showed a significant difference in marginal discoloration between the 3- and 7-year follow-ups. Logistic regression analysis revealed that no baseline factors influenced retention outcomes.
Conclusions:
No statistically significant differences in survival were detected among the tested restorative systems after 7 years. Although flowable bulk-fill restorative systems showed increased marginal discoloration, this finding may be interpreted as an esthetic alteration rather than a functional failure or the need for restoration replacement. Additionally, flowable bulk-fill restorative systems showed changes in marginal outcomes over time.
Clinical Significance:
Flowable bulk-fill restorative systems can be used in Class II restorations, as no statistically significant differences in survival were detected among the tested restorative systems after 7 years. Clinicians should be aware of the increased risk of marginal discoloration in these restorative systems; however, it should be interpreted as an esthetic alteration rather than a functional failure.
