Impact of Surface Micromorphology and Demineralization on Enamel Loss Measurements by CP-OCT

Objectives: Optical Coherence tomography (OCT) is a promising clinical imaging technology for quantitative and objective assessment of dental erosion. We aimed to determine the influence of enamel surface roughness and demineralization severity (by erosive challenge) on dental surface loss measurements by cross-polarization OCT (CP-OCT).

Methods: Human enamel specimens were obtained from extracted molars and prepared with three surface roughness levels (very rough, rough and polished; n=10). They were evaluated using CP-OCT (swept laser light source, wavelength of 1310 nm, Santec Inner Vision IVS-300-S-L-C, Santec Corp) and optical profilometry (gold standard, S5/03 sensor, Proscan 2000, Scantron) at baseline, and after 1, 2, 4, 6, 8, 16 and 24 h of demineralization in 0.3% citric acid (pH 2.4), under static and room temperature conditions. The effects of roughness and demineralization on enamel loss measurements were analyzed using ANOVA (alpha=0.05). Intraclass correlation coefficients (ICCs) and Bland-Altman plots were used to evaluate inter-method agreement and intra-examiner repeatability.

Results: CP-OCT surface loss measurements did not significantly differ with the changes in enamel surface roughness (p=0.27). Among demineralization severities, CP-OCT surface loss measurements at 1, 2, 4 and 8 h did not differ among each other, but they showed significantly lower enamel loss than 16 and 24 h; 6 and 16 h were significantly lower than 24 h (p<0.05). Overall, there was no significant difference (p=0.73) between the mean measurements (mean±SE, in micrometers) of CP-OCT (-39±0.5) and optical profilometry (-40±4); however, ICC was relatively low (ICC=0.34). Enamel loss estimation by CP-OCT presented an error of approximately ±150 µm compared to profilometry. Intra-examiner repeatability with CP-OCT was excellent (ICC=0.98).

Conclusions: Enamel roughness did not affect CP-OCT measurements. The estimated error of CP-OCT measurements limited the appropriate assessment of enamel erosion surface loss, in the magnitude simulated in this study.