Progression of erosive lesions after Nd:YAG laser and fluoride using optical coherence tomography

This study aimed to use optical coherence tomography (OCT) to assess the progression of erosive lesions after irradiation with Nd:YAG laser and application of topical fluoride. One-hundred and twenty dentin samples (4 × 4 × 2 mm) obtained from bovine incisors were used. Samples were protected with acid-resistant nail varnish, with exception of a central circular area 2 mm in diameter. All samples were submitted to erosive cycles with citric acid solution 0.05 M (citric acid monohydrate—C6H8O7·H2O); M = 210.14 g/mol) pH 2.3, at room temperature, for 20 min, 2×/day, throughout 20 days. After 10 days of acid challenges, lesions became visible, and each group received a different treatment (n = 15): control (without treatment), topical application of sodium fluoride 2 % for 4 min; Nd:YAG laser with different irradiation parameters (1, 0.7, and 0.5 W); and the association of fluoride with the laser parameters. OCT readouts were performed on day 01 (before the first acid challenge—OCT1), on day 05 (OCT2), day 10 (OCT3—after treatment), day 15 (OCT4), day 17 (OCT5), and day 20 (OCT6). The OCT images generated made it possible to measure the amount of tooth tissue loss over the 20 days of erosive cycle, before and after treatments, and to monitor early dentin demineralization progression. After statistical analysis, the fluoride group was observed to be the one that showed smaller loss of tissue over time. The OCT technique is promising for diagnosing and monitoring erosive lesion damage; however, further in vitro and in vivo research is needed to improve its use.