Effect of gingival fluid on marginal adaptation of Class II resin-based composite restorations

Purpose: To evaluate in vitro the marginal quality of Class II composite re storations at the gingival enamel margins as affected by contamination of t he cavities with gingival fluid (GF) during different steps of resin bondin g procedures. Materials and Methods: 70 Class II cavities were prepared in extracted human molars and restored with composite using a multi-component bonding system (OptiBond FL/Herculite XRV; OPTI) or a single-bottle adhesiv e (Syntac Sprint/Tetric Ceram; SYN). The cavities were contaminated with hu man GF: C1 after acid etching, C2 after application of the primer (OPTI) or light-curing of the primer-adhesive (SYN), and C3 after light-curing of th e resin adhesive (OPTI). Uncontaminated cavities were used as the control ( C0). The restored teeth were subjected to thermocycling (TC) and replicated for SEM analysis of marginal gap formation. Microleakage at the gingival m argins was determined by dye penetration with basic fuchsin. Statistics: no n-parametric tests (Kruskal-Wallis test, Mann-Whitney test with Bonferroni correction). Results: In both bonding systems, contamination with GF after acid etching (C1) did not impair the marginal quality; the mean percentages of continuous margin/mean depths of dye penetration were: OPTI: C0: 88.5%/ 0.10 mm, C1: 95.6%/0.04 mm; SYN: C0: 90.9%/0.08 mm, C1: 97.0%/0.05 mm. Marg inal adaptation was adversely affected when GF contamination was performed after OPTI primer application (C2: 75.4%/1.51 mm) and after light-curing of SYN (C2: 79.6%/0.94 mm), respectively.