a Potassium-containing Fluoridated Hydroxyapatite varnish and its effect on dentin

Objectives: to produce a Potassium-containing Fluoridated Hydroxyapatite varnish and to evaluate its effect on dentin in vitro and in vivo.

Methods: Hydrofluoric acid and potassium nitrate was selected as fluorine-containing and Potassium-containing reagents to add into mixed Ca (NO₃)₂-P₂O₅ ethanol solutions to form dipping sols. The nature resin was added as varnish reagents. The properties of the novel material were investigated by XRD and EDX. The cervical dentin of premolars was cut and polished to obtain a flat surface with opened tubules. The surface morphology of the dentin applied with the material was observed by SEM. After biological assessments, the novel varnish was proved to be biocompatible for dental clinical application. 81 patients of dental hypersensitivity, totaling 281 teeth were enrolled in a Random Control Test in 8 weeks. Following stimulation of teeth by tactile probe and air blast stimuli, sensitivity was recorded using Yeaple probe score, Schiff Air Sensitivity Scale and visual-analogue scale (VAS).

Results: All of the resulting samples showed apatite structure in their XRD patterns. Fluorine and potassium were incorporated into hydroxyapatite. EDX recorded the mapping of Ca, P, K and F element in the surface of the dentin applied with material. SEM indicated that the tubules were covered by a 10 µm layer of varnish and in the 10µm inside tubule diameter, material particles were observed. Compared to the baseline, both the test and the control treatments resulted in a significant (p<0.05) reduction of discomfort at each follow-up examination. There were significant differences in tactile threshold, Schiff scores and VAS scores (p<0.05; respectively) between test and control groups at 8 weeks.

Conclusions: The novel potassium-containing fluoridated hydroxyapatite varnish was produced successfully through sol-gel method. The varnish was proved to be an effective way to reduce dentine sensitivity.