Management of permeability of eroded root dentin through laser irradiation

There is evidence that erosion is key to the etiology of dentin hypersensitivity (DH). Among several approaches that have been investigated for managing DH, Nd:YAG and Er:YAG lasers have been advocated to reduce permeability of root dentin. Objective: To evaluate, through a 2x2 crossover intraoral model, the ability of laser irradiation to control permeability of eroded root dentin that was subsequently subjected to erosive challenges. Methods: Root dentin slabs were prepared from third human molars (3x3x2mm), sterilized and coated with wax except for a circular area on their outer surface. Specimens were cycled through acidic challenges (0.3% citric acid-CA,2h) and remineralization periods in artificial saliva to induce erosion-like lesions. Specimens were laser-irradiated with Nd:YAG (1W/15Hz) or Er:YAG (100mJ/3Hz) or left nonirradiated (control) and then placed in 12 individuals wearing intraoral appliances. In the first phase (5d), half of volunteers immersed their appliances in CA (90s,4x/d), while the remainder did not. After a 2-d washout period, a new set of specimens were mounted in appliances and participants crossed over to the treatment they had not received in phase 1. Specimens were subjected to a histochemical coloring method using cooper sulfate and dithiooxamide solutions. Three sections taken from the exposed area were imaged in an optical microscope. Permeability was measured in digitized images as the % of cooper penetration over the dentin thickness. Results: ANOVA indicated interaction between erosion during intraoral phase and laser irradiation (p>0.001).