Effect of a new combined therapy with nano-carbonate apatite and CO ₂ laser on dentin hypersensitivity in an in situ model

Objective: The aim of this study was to determine the occluding effects of a combination of dentifrice containing nano-carbonate apatite (n-CAP) and CO₂ laser on dentinal tubules, and to evaluate the acid resistance of this combination after 4 days of treatment, by using an in situ model. Background data: The synergic effect of this combination was demonstrated in an in vitro study. Methods: This was a two period crossover, single-blind, randomized, four-treatment, split-mouth study. Ten healthy participants wore lower intraoral appliances during the treatment period. Specimens were divided into the following four groups: no treatment (control group), tooth-brushing using 20% n-CAP dentifrice (n-CAP group), CO₂ laser irradiation (laser group), and laser irradiation after n-CAP application (combined group). Occluding effects were evaluated on 2 days (days 1 and 2), and then acid challenge was performed using grape juice on 2 days (days 3 and 4). All of the specimen surfaces were evaluated by a scanning electron microscope. Results: The combined group showed a better occluding effect than control group compared with other treatment groups, and this effect was 20% higher than that in the n-CAP group. Also, the combined group had the smallest open dentinal tubular area among all of the treatment groups. Conclusions: The combined therapy is a promising method for ensuring a long-lasting effect of dentin hypersensitivity treatment in clinical practice.