In-vitro characterization and evaluation of mesoporous titanium dioxide composite hydroxyapatite and its effectiveness in occluding dentine tubules.

Background: To synthesize mesoporous titanium dioxide composite hydroxyapatite (TiO-HAP) and to evaluate its effectiveness in sealing of occluding dentine tubules.

Methods: TiO-HAP was synthesized by chemical precipitation method and characterized using infrared absorption spectrometer, X-ray diffraction, scanning electron microscope, and specific surface area detector. Forty completely extracted molars were prepared and randomly assigned into Control group, Gluma group, HAP group and TiO-HAP group according to different treatments. The characteristics of HAP and TiO-HAP and the sealing effectiveness of dentine tubules in these four groups, including infrared spectrum, surface contact angle, pore size distribution, and re-mineralized enamel surface profiles, were analyzed by suitable characterized techniques. The cytotoxicity of the synthesized TiO-HAP was tested and compared using 3-(4,5)-dimethylthiahiazo(-z-y1)-3,5-di-phenytetrazoliumromide (MTT) colorimetry.

Results: Our results showed TiO-HAP group had significantly lower contact angle, higher specific surface area, and wider range of pore size distribution than other groups. The majority of dentinal tubules in the TiO-HAP group were blocked by white matter in a uniformed manner, and the crystals arranged in order grew along the axial direction. In addition, no significant difference in optical density (OD) value was found between control group and TiO-HAP group (P > 0.05), and cell growth was good in TiO-HAP group, indicating no cytotoxicity of TiO-HAP.

Conclusions: The MTT assay identified that TiO-HAP had little effect on the L929 cell line. We showed TiO-HAP might be used as a remineralization agent in enamel caries-like lesions.