Internal adaptation and micromorphological analysis of a new self-cure resin composite

Enhancing the adaptation and durability of composite restorations remains a major challenge in modern adhesive dentistry. Recently, a new self-cured resin composite has gained attention with the potential to improve interfacial adaptation and reduce polymerization shrinkage stress, offering an alternative to conventional light-cured systems.

Sixteen freshly extracted human molars were prepared with standardized Class II cavities and randomly assigned to two groups (n=8). The first group was restored using a self-cure bulk-fill resin composite (Stela Automix, SDI Ltd., Australia) with its respective primer, while the second group received an injecTable resin composite (G-aenial Universal InjecTable, GC Corporation, Japan) with a universal adhesive. Restorative procedures followed manufacturers' instructions. The restorations were finished and polished, before being stored in distilled water at 37°C for six months to simulate aging conditions. After storage, specimens were sectioned longitudinally and analyzed using environmental scanning electron microscopy to evaluate internal adaptation, and interfacial gap measurements were recorded.

An independent Sample T-test showed a statistically significant difference in interfacial gap (IG%) between the two restorative systems, with the self-cure composite showing more favourable outcomes. For stela, the IG% was13.5±6.1 while for InjecTable composite IG%=28.4±13.3.

The Stela primer and composite used in this study demonstrated superior internal adaptation compared to the light-cured control, suggesting they could be a viable alternative, particularly for deep gingival margins or situations where light curing is inaccessible. Key words:Self-cure composite, internal adaptation, SEM, curing mode, Universal adhesive.