Quantitative Assessment of Dental Calculus With Optical Coherence Tomography (OCT)

Objectives: The aim of this study is to develop and validate a method to identify the tooth-calculus interface using Optical Coherence Tomography (OCT) and to use it to assess the effectiveness of a treatment for enhancing calculus removal.
Methods: 3D scans of calculus deposits with varying thickness on human extracted teeth were performed with MicroCT and OCT and the corresponding frames were identified and superimposed. OCT image processing was performed using MATLAB. The location of the tooth-calculus interface (TCI), which was clearly demarcated on the MicroCT scans were outlined on the OCT scan and the mean OCT reflectance at the interface determined. An algorithm was developed to automate the selection of regions of interest and outline the TCI. The algorithm was validated against scans of another cohort of calculus (n=10). One-sample T-test and Bland-Altman plot was used to assess the difference between OCT and MicroCT (Δt) in calculus thickness measurements. The validated algorithm was used to measure the mean calculus thickness before (T₀) and after(T₁) application of a two-part treatment where part A is applied, followed by part B. 15 calculus deposits (>0.3mm thickness) on human extracted teeth were subjected to the treatment whilst 2D time-lapse OCT scans were performed.
Results: The mean of Δt, was 0.0038 mm and not significantly different from zero (p>0.05). The Bland-Altman plot showed a random spread of Δt around the mean with all values falling within 2 SD. Linear regression analysis showed no proportional bias between the MicroCT and OCT measurements. Baseline thickness, T₀ was 0.432±0.1 mm and paired T-test showed significant (p<0.05) mean thickness reduction of 0.08±0.06mm (17.3±11%) after intervention.
Conclusions: An algorithm was developed and validated to identify the tooth-calculus interface on OCT scans and it was used to measure the efficacy of a calculus reduction treatment.