Biocompatibility testing of hydroxyapatite using human gingival epithelial cells

Dentin hypersensitivity is a common condition of transient tooth pain associated with a variety of exogenous stimuli, and the therapy for it is very important for conservative treatment. Objectives: The purpose of this in vitro study was to examine the biocompatibility of nanograde hydroxyapatite (HA) as a dentin desensitizing agent with human gingival epithelial cells. Methods: Human gingival tissue was used for primary culture. The tissues were incubated in aMEM, supplemented with 10% fetal bovine serum, 2 mM L-gluthamine, and 100 U/ml of antibiotics, in culture dish and maintained in a humidified atmosphere of 5% CO₂ in air at 37°C. Upon confluence, human gingival fibroblasts(HGFs) were detached by incubation with 0.2% trypsin in 0.02% EDTA solution for 5 min at 37°C. Then, cells were plated on tissue culture dishes at a density of 2x10⁴ cells/ml. The fourth passage cell line was used for compatibility test. Cells were cultured in dishes adding nanograde HA powder or light-cured Cleafil Megabond Bond (MB) or Megabond Primer(MP) . The cell proliferation was evaluated by the observation using phase-contrast microscopy and by the trypsinized cell counting using a hemocytometer at each 0,2,4 and 7 days after plating. Statistical analysis was performed using unpaired Student's t-test. Results: On the observation using phase-contrast microscopy, nanograde HA showed an excellent biocompatibility with HGFs and was much more compatible with HGFs than MB and MP. On the cell counting, nanograde HA is much more compatible with the HGFs than MB and MP (p < 0.01).Conclusion: These results suggested that an inorganic compound was more adaptable to the dentin desensitizing agent than an organic one.