Non-destructive Evaluation of Marginal Gaps in Stressed Class V Restorations

Objectives: To evaluate the marginal adaptation of composite resins (CRs) with different elastic moduli (EM), before and after thermo-mechanical loading (TML), using polarization-sensitive, spectral-domain optical coherence tomography (PS-OCT).
Methods: Standardized Class V preparations (2mm width × 2mm height × 1.5mm depth) with occlusal margins in enamel and gingival margins in dentin were made on the facial and lingual surfaces of 12 human premolars. Specimens were randomized to one of three groups (n=8): Tetric EvoCeram Bulk Fill (intermediate EM); Filtek Supreme Ultra (high EM); Durafill VS (low EM). All specimens were restored with the same 2-step self-etch adhesive (Clearfil SE Bond) and CRs were applied and light-cured following manufacture’s recommendations. After finishing (Sof-Lex) and storage (30 days, 100% humidity), 121 cross-sectional PS-OCT baseline images were obtained along each restoration’s margins in increments of 25μm with 3mm (x) × 3mm (y) × 1.34mm (z) as total dimensions sampled in volume. B-scan images were analyzed using Image J, and the deepest enamel and dentin marginal gaps in each specimen were measured linearly. The samples were then loaded for 250,000 cycles (5 Kg at 1.2 Hz) with simultaneous thermocycling (5/55°C) for 90s (CS-4.8, Mechatronik, Germany). The same imaging protocol was then performed post-TML, for the same specimens. Data were statistically analyzed using a general linear model (GLM) analysis of variance (ANOVA) and Tukey post-hoc test for pairwise comparisons (P<0.05).
Results: GLM ANOVA showed statistically significant differences in the factors “TML” and “material” (P<0.001) as well as in their interaction (P<0.001). Durafill VS presented significantly higher marginal gaps (P<0.001) than the other composites after TML. Results are summarized in the table.
Conclusions: From the composites tested, the material with the lowest elastic modulus resulted in higher marginal gaps for class V composite resin restorations, particularly after TML.