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

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.

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).

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).

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.