In vitro SEM analysis of desensitizing agents and experimental hydroxyapatite-based composition effectiveness in occluding dentin tubules

Abstract

Background. Novel materials used for dentin hypersensitivity (DH) treatment, including hydroxyapatite-based desensitizers, are not only effective in occluding dentinal tubules, but are also biocompatible and non-toxic. A newly formulated desensitizer containing hydroxyapatite was evaluated in comparison to commercially available desensitizers. Objectives. To compare the occluding efficacy and durability of 3 commercially available desensitizing agents with a pharmaceutical composition developed by the authors based on hydroxyapatite (HAp). Material and methods. For the experiment, 40 disc-shaped dentin specimens (5 mm thick) were obtained from extracted human teeth. Each disc was divided into 4 sections, so that each desensitizing agent could be applied to each specimen and prepared for further evaluation in most homogenous conditions. The chemical composition of the dentin surfaces was analyzed using scanning electron microscopy (SEM) equipped with an energy-dispersive X-ray spectroscope (EDS), Fourier-transform infrared (FTIR) and Raman spectra techniques. The specimens were immersed in an artificial saliva solution for 24 h, 48 h and 7 days to assess the durability of the layers and the tubule-obliteration effectiveness. Data analysis was performed using Student's t-test with an average value of normal distribution at an unknown variance with a standard deviation (SD) of σ-0.4. Results. All the test groups showed some degree of dentinal tubule occlusion or a covering layer, but the HAp-based composition proved to be the longest-lasting. It was concluded that the developed pharmaceutical composition creates a coating on the dentin surface built of hydroxyapatite crystals sized 10-20 μm, which are likely to constitute a reservoir of calcium and phosphate ions, as well as smaller crystals (0.2-0.3 μm) that occlude dentinal tubules. Conclusions. The composition containing biocompatible hydroxyapatite effectively occluded dentinal tubules and therefore exhibits a potential for reducing the pain and discomfort caused by dentin hypersensitivity.