Proximal Post-Curing Improves Microhardness of Class-II Resin Composite Restorations

Aim: This in vitro study investigated the effect of additional proximal post-curing on the microhardness of Class-II resin composite restorations. Methods: Thirty-two extracted human third molars received narrow (N) or wide (W) MO Class-II cavities with cervical margins extending below the cemento-enamel junction. Cavities were restored with Venus Diamond using an adhesive protocol and incremental layering. Specimens were assigned to four groups: N.O, N.OT, W.O, W.OT, representing cavity width (N/W) and curing protocol (O: occlusal light curing only, OT: occlusal plus proximal post-curing after matrix band removal). After 7 days of storage in artificial saliva, restorations were sectioned into three vertical planes, and Vickers microhardness (HV2/30 s) was measured. Results: The highest overall microhardness was observed in Group W.OT (81.35 HV2), whereas Group N.O showed the lowest values (73.14 HV2) (p < 0.05). Proximal post-curing significantly increased microhardness, with Group N.OT (78.34 HV2) exceeding both occlusal-only groups (W.O: 74.68 HV2; p < 0.05). In all groups, microhardness decreased with increasing restoration depth (p < 0.05), although this reduction was less pronounced after post-curing. Conclusions: Within the limitations of this in vitro study, proximal post-curing significantly increased polymerization depth and microhardness of Class-II resin composite restorations.