The Effect of Different Types of Adhesive Systems on Marginal Integrity of Class II Resin Composite Restoration.

PURPOSE: To evaluate the marginal integrity of cervical margin relocation (CMR) or deep margin elevation (DME) restorations using a universal adhesive in etch-and-rinse and self-etch modes, compared to gold-standard systems after 6-month water aging. METHODS AND MATERIALS: Standardized mesial and distal Class II cavities were prepared in 32 human maxillary premolars. Specimens were assigned to four groups according to adhesive systems and modes: OFL (OptiBond FL), CSE (Clearfil SE Bond), UER (Single Bond Universal; etch-and-rinse), and USE (Single Bond Universal; self-etch) (n = 16 per group). After DME/CMR and final restoration, specimens were stored in 37°C distilled water for 6 months. Marginal integrity was assessed qualitatively via micro-CT by two calibrated observers and quantitatively via 0.5% methylene blue dye. Data were analyzed using weighted kappa coefficient, Wilcoxon signed-rank test, two-way repeated measures analysis of variance (ANOVA), and one-way ANOVA with Games-Howell post-hoc tests (α = 0.05). RESULTS: Micro-CT showed high inter-examiner reliability (κ = 0.84) and stable interfacial adaptation across groups post-aging. However, dye penetration revealed that adhesive mode significantly affected microleakage (p 0.05), while proximal box concavity geometry had no significant effect (p > 0.05). The USE group exhibited the lowest mean microleakage (0.94 ± 0.62 mm), showing no significant differences from OFL and CSE. The UER group showed the highest mean microleakage (1.48 ± 0.09 mm), which was significantly higher than the USE group (p 0.05). CONCLUSION: Within the limitations of this study, the self-etch application of universal adhesives provided superior durability of marginal seals for DME compared to the etch-and-rinse mode. Optimizing matrix application also minimized the influence of concavity geometry.