Objective: This study examined the impact of early biofilm on the tooth surface, during the assessment of initial enamel erosion using swept-source optical coherence tomography (SS-OCT). Method and materials: Forty-five enamel windows of 2 × 4 mm2 were prepared on 23 extracted human teeth. The specimens were exposed to citric acid (pH 3.2) for 30 minutes and randomly divided into three groups (n = 15): Group 1, no biofilm; Group 2, 1-day-old biofilm; and Group 3, 3-day-old biofilm. Specimens in Groups 2 and 3 were inoculated with oral bacteria (Streptococcus sanguinis, Streptococcus mitis, and Actinomyces naeslundii) to produce early laboratory-cultivated biofilms for 1 and 3 days respectively. Surface microhardness (SMH) measurements were taken at pre- (t1) and post-erosion (t2); and SS-OCT scans were done at t1, t2, and post-biofilm cultivation (t3). Integrated reflectivity (IR) of the tooth-air interface (IRsurface) and enamel (IRenamel) were computed from the mean A-scans. Statistical analysis was performed using paired t tests and one-way ANOVA (α = .05). Results: A significant increase in IRenamel was observed at t2 (P < .05). At t3, IRsurface between Group
1 (control) and Group 2 (P = .012) as well as Group 3 (P = .001)
were significantly different. Significant variances in IRenamel were
perceived between t2 and t3 for Groups 2 and 3 but not for
Group 1. Conclusion: As early biofilm affected SS-OCT assessment
of initial enamel erosion, they should be removed from
the tooth surface prior to OCT procedures.