New-Generation Flowable Bulk-Fill Composites as Stand-Alone Posterior Restorations: A Narrative Review

Restoration of endodontically treated posterior teeth with extensive mesio-occluso-distal (MOD) cavities remains a clinical challenge because of substantial loss of tooth structure and increased susceptibility to cuspal deflection and fracture. Bulk-fill resin composites were introduced to simplify restorative procedures while reducing polymerization shrinkage stress and improving biomechanical behavior. Flowable bulk-fill composites were initially indicated as stress-relieving base materials because of their lower filler content and elastic modulus. However, newer-generation formulations exhibit modified filler loading, optimized elastic modulus, and increased curing depth, allowing their use as stand-alone restorative materials in posterior teeth. This narrative review examined recent evidence describing the mechanical behavior of bulk-fill composites in posterior restorations. Particular attention was directed toward cuspal deflection, polymerization effects, fracture resistance, and clinical applicability in large MOD cavities.Electronic database screening was performed using PubMed, Scopus, and Google Scholar. Eligible studies included laboratory investigations evaluating posterior Class II or MOD cavities restored with bulk-fill composites. Studies based on non-posterior cavity designs, conventional non–bulk-fill materials, or incomplete methodological descriptions were not considered.Reported outcomes included cuspal deflection behavior, polymerization shrinkage effects, fracture resistance, marginal adaptation, and restorative variables.In conclusion, this narrative reviewindicatedthat flowable bulk-fill composites generally exhibit reduced polymerization shrinkage stress and lower cuspal deflection compared with conventional composite techniques. New-generation flowable bulk-fill materials demonstrate improved biomechanical performance relative to earlier formulations and, in selected MOD cavity designs, approach the behavior of packable bulk-fill composites. Although favorable results have been reported, variability in study design and testing protocols remains evident. New-generation flowable bulk-fill composites may therefore be considered a viable stand-alone option for selected posterior MOD cavities, provided that cavity configuration, material selection, and clinical technique are carefully controlled.