Nano-computed tomography evaluation of volumetric polymerization shrinkage and internal adaptation of self-adhesive bulk-fill composites: An in vitro study

Aim: The aim of the study was to measure the volumetric polymerization shrinkage (VPS) of conventional and self-adhesive bulk-fill composites, using nano-computed tomography (CT) and quantitatively correlate these findings with interfacial gap formation. Methods: Twelve extracted human maxillary first premolars were taken. Root canal treatment was performed, and teeth were randomly assigned to two groups for postendodontic restoration: Group I ( n = 6) – restored with bulk-fill composite resin (Tetric N-Ceram) after etching and bonding, Group II ( n = 6) – restored with self-adhesive bulk-fill composite resin (Surefil One) without etching and bonding. Each tooth was scanned using Nano-CT before and after light curing to assess VPS% and interfacial gaps (Pre-cure scan and Post-cure scan). The two scans were superimposed in the three-dimensional rendering software to obtain VPS% and interfacial gaps. Results: Conventional bulk-fill composites exhibited higher VPS than self-adhesive bulk-fill composites, although the difference was not statistically significant. The self-adhesive bulk-fill composites showed a higher volume of external voids compared to conventional composites, but again, this was not statistically significant. Conclusion: Self-adhesive bulk-fill composites demonstrated reduced volumetric shrinkage compared to conventional composites, suggesting potential clinical benefits. However, they also showed a higher incidence of interfacial gaps, which may impact their long-term effectiveness.