Supplementary Material for: Enamel caries lesion depth obtained by optical coherence tomography and transverse microradiography: a comparative study

Introduction: Visual imaging of sub-surface caries lesions is of vital interest in dentistry, which can be obtained by invasive radiography-technique as well as by available non-destructive imaging approaches. Thus, as a first step towards the development of a new innovative approach, the Spectral-domain optical coherence tomography (SD-OCT) was applied to detect the lesion depth in comparison to the established reference technique (transverse microradiography, TMR). Methods: Bovine enamel specimens were demineralized for 5 days, following previous studies by Braga et al., [2021] and [2022]. For OCT, the resulting artificial lesions were scanned three-dimensionally (SD-OCT), and semiautomated measured (CarLQuant). For TMR, specimens were sectioned and the lesion depth was manually determined (Inspektor Research System). Results: The range of lesion depth detected with OCT was 24.0 to 174.0 µm (mouthrinses study, Braga et al., [2021]), 18.0 to 178.0 µm (toothpastes study) and with TMR 59.2 to 198.0 µm (mouthrinses study), 33.2 to 133.4 µm (toothpastes study, Braga et al., [2022]). We found a strong correlation between both methods in terms of lesion depth (Spearman rankwith outlier p<0.001, Rho=0.75, Spearman rankwithout outlier p=0.001, Rho=0.79). The two methods produce similar results (Passing Bablok regression, 1.16). As deeper is the lesion, the smallest is the difference between both methods as indicated by Bland-Altman-plots. Conclusion: Especially in the case of deep lesions, the values obtained by both methods are in agreement, and OCT can potentially substitute TMR to detect and assess lesion depth with the benefit of being non-destructive.