Clinical performance of different types of posterior bulk-fill resin composite restorations in permanent teeth: a systematic review

Abstract Background Bulk-fill resin composites were developed to overcome limitations of incremental placement techniques: time consumption and air bubble entrapment. They are available in different viscosities, including high-viscosity (sculptable) and low-viscosity (flowable). Furthermore, practitioners deploy various techniques, such as sonic activation and preheating, to reduce the viscosity of bulk-fill resin composites. However, few studies have evaluated the clinical performance of different bulk-fill resin composite types. Consequently, this systematic review aimed to evaluate and compare the clinical performance of sonic-activated, preheated, and flowable bulk-fill resin composites versus conventional high-viscosity bulk-fill materials in permanent posterior teeth, regarding the following parameters: functional (retention, marginal adaptation, and anatomic form), esthetic (marginal discoloration, color match, and surface texture), and biological parameters (secondary caries and postoperative sensitivity). Methods This systematic review was conducted in accordance with PRISMA guidelines. An electronic search of PubMed and ScienceDirect identified clinical trials published between 2015 and 2025 that compared different types of bulk-fill resin composites. Clinical studies evaluated any cavity class in permanent posterior teeth with at least a one-year of follow-up. Study selection and data extraction were performed independently by two reviewers using predefined inclusion and exclusion criteria and a standardized, pilot-tested data extraction form. Included variables were study characteristics, sample size, type of restorative material, evaluation criteria, follow-up duration, and clinical outcomes. The modified Cochrane Risk of Bias Tool was used to assess the quality of the selected studies. Results Out of 1041 records, 33 full-text articles were assessed for eligibility, with six randomized controlled trials (RCTs) finally included. Overall, no significant differences were observed among bulk-fill resin composite types regarding retention, surface texture, anatomic form, secondary caries, or postoperative sensitivity. Some trends suggested slightly better marginal adaptation for flowable or preheated composites. Additionally, one included study reported no significant differences between Class I and Class II restorations. Conclusions Different types of bulk-fill resin composites perform similarly for most functional and biological parameters, with marginal adaptation and discoloration being the parameters requiring further long-term investigation.