Evaluation of calculus imaging on root surfaces by spectral-domain optical coherence tomography

Objective: The aim of this in vitro study was to evaluate the ability of optical coherence tomography (OCT) to display calculus on root surfaces. Material and methods: Ten teeth with calculus on the root surface were embedded in resin, omitting the root surface. A region of interest (ROI) was marked by small drill holes coronally and apically of the calculus and imaged by spectral-domain optical coherence tomography ([SD OCT], Telesto SP5, centre wavelength 1310 nm) and light microscopy (LM). To evaluate the impact of different fluids on calculus visualisation, using OCT, root surfaces were covered by a layer of NaCl and blood and displayed by OCT. Subsequently, teeth were completely covered with resin and sectioned for histological evaluation. Within the ROI, lengths of root surface and calculus were measured by LM and OCT, and the ratio [%] was calculated. In addition, at three sites of each ROI, agreement of presence and length of calculus was evaluated. Both methods were compared using Pearson's correlation. Results: Regarding the presence of calculus, agreement between LM and OCT was strong (kappa(i) = 0.783, p = 0.033), and measurements regarding the length of the calculus were strongly correlated (r(i) > 0.906; p(i)< 0.001). However, the values differed for dry (p = 0.023) and NaCl-covered root surfaces (p = 0.035). Conclusion: Calculus on the root surface can be displayed by SD-OCT, which therefore may be suited as imaging technology for subgingival calculus in periodontal pockets.