Comparative Evaluation of the Mechanical and Biological Properties of Contemporary Dental Composites

Abstract

Background: Resin composites are the most widely used direct restorative materials. New formulations, including nanohybrid, bulk-fill and flowable composites, differ in filler technology and resin chemistry, which may influence their mechanical durability and biocompatibility.
 Aim: To compare the mechanical and biological properties of four contemporary resin composites: a microhybrid, a nanohybrid, a sculptable bulk-fill and a flowable bulk-fill composite.
 Materials and methods: Specimens of [Material A, microhybrid], [Material B, nanohybrid], [Material C, sculptable bulkfill] and [Material D, flowable bulk-fill] were prepared and light-cured according to the manufacturers' instructions.
 Flexural strength and flexural modulus were measured by three-point bending according to ISO 4049 (n = [10] per group).
 Vickers microhardness was measured at the top and bottom surfaces of 4 mm thick specimens, and the bottom-to-top hardness ratio was calculated (n = [10]). Water sorption and solubility were determined according to ISO 4049 (n = [5]).
 Volumetric polymerisation shrinkage was measured with [a video-imaging device / the buoyancy method] (n = [5]).
 Cytotoxicity was assessed with the MTT assay on [L929 / human gingival] fibroblasts exposed to material extracts at 24 and 72 hours (n = [6]). Data were analysed with one-way ANOVA and Tukey post-hoc tests (α = 0.05).
 Results: Flexural strength ranged from [XX ± SD] MPa ([Material D]) to [XXX ± SD] MPa ([Material B]) (p [< 0.001]); all materials exceeded the ISO 4049 minimum of 80 MPa. [All / Only Materials C and D] achieved a bottom-to-top hardness ratio of at least 0.80 at 4 mm. Water sorption and solubility were within ISO limits for all materials.
 Polymerisation shrinkage was [highest] for [Material D] ([X.XX ± SD]%). Cell viability exceeded [70]% for [all materials at 72 hours], indicating no cytotoxic effect according to ISO 10993-5.
 Conclusion: [The nanohybrid composite showed the most favourable mechanical properties, while bulk-fill composites achieved adequate depth of cure at 4 mm.] All materials were biocompatible in vitro. Material selection should consider the clinical situation, including load-bearing, cavity depth and the need for a capping layer with flowable bulk-fill composites.