Evaluation of Demineralization around Composite Restorations using Optical Coherence Tomography

Objectives: To use swept-source optical coherence tomography (SS-OCT) in evaluating marginal integrity of composite restorations before and after demineralization. Methods: Round cavities (4x2 mm) were prepared on the cervical area of bovine teeth, and restored with Estelite Flow Quick (EF, Tokuyama Dental) and one of three adhesives; Bond Force (BF, Tokuyama Dental), Scotchbond Universal (SB, 3M ESPE) or G-Bond Plus (GB, GC). Control group was restored with EF only (n=10). After 3-day incubation in artificial saliva and 10,000 thermocycling cycles, gaps at enamel and dentin margins were scored on four B-scan images obtained across each restoration using SS-OCT (Santec, Japan) at 1310 nm center wavelength. After three weeks of immersion in a demineralizing gel (pH= 4.5), the specimens were evaluated again, and the lesions formed at enamel and dentin margins were scored on SS-OCT cross-sectional images. Mean ranks of marginal gaps and marginal lesions were compared by non-parametric statistical analysis at significance level of 0.05. Results: Before demineralization, there was a statistically significant difference in sealing of both enamel and dentin margins between Control and the adhesive groups (p<0.05). SB and BF showed significantly lower enamel marginal gaps than GB (p<0.05). SB showed significantly lower dentin gap scores than other groups (p<0.05). After demineralization, enamel and dentin marginal lesions were significantly deeper in control group, while there was no statistically significant difference among the three adhesive groups. Spearman's test suggested a moderate significant correlation between gap score and lesion extent at enamel margin (rho= 0.45, p<0.005), but not for dentin (p>0.05). Conclusion: Clinically, OCT would be a promising tool for monitoring and evaluation of composite restoration margins. While the ability of adhesives to seal tooth-composite margin is a substantial factor for prevention of lesion formation at the interface, demineralization of dentin margins may depend on other factors as well.