Experimental Research Of A New Nano-hydroxyapatite As Root Canal Filling Sealer

Objective Nano-hydroxyapatite root canal sealer is a new biomaterial, it's made up of nano-hydroxyapatite,iodoform and silicon oil,et al. In this study we had done a series of basic experiments before it is for clinical use as a root canal filling sealer .Method The systematic researches were divided into four parts: Part one "The antibacterial activites of n-HA in vitro ". The flat drill method were used ,and AH-plus as control, to study the antibacterial ability to P.gingivalis, F.nucleatum and P.intermedius, which were the high rate detected bacteria in infacted root canals. Part two "Evaluation on Cytotoxicity of nano- hydroxyapatite in vitro " In this study , the cytotoxicity was evaluated by the MTT method and the activity of ALP with mouse osteoblast. Part three "Evaluation on the apical sealing ability of n-HA in vitro." 34 single-rooted human teeth were instrumented. They were randomlydivided into 2 groups of 15 teeth each and filled using lateral condensation with one of the two test sealers (AH-plus, n-HA) and gutta-pertha. Another 2 groups as positive and negative controls (2 teeth each). The apical leakage was measured by dye penetration method. Part four "biocompatibility of n-HA on experimential animial in vivo".Three dogs were used and AH-plus was as control ,each dog was used for three experiments of root canal filling, mandibula implanting and subcutaneous implanting , the animals were killed after 2,4 and 12 weeks separately. The tissue reaction was assessed by X-ray and histological examination.Result ?From the diameter of the antibacterial annulus,n-HA showed more stronger antibacterial ability to three test baterials than AH-Plus..(2)With the culture time increasing the toxicity graduation of the nHA tends to 0. The cell survival rate of n-HA showed high relatively .The OD value of cell was similar to the negative control (P > 0.05 ) .(3)A11 root canal sealers tests showed some apical microleakage.AH-plus was better than n-HA,no significant difference was found between two test materials(p>0. 05).?Animal experiment showed no or merely a mild inflammatory reaction detected in specimens of n-HA,while AH-plus initiated a middling inflammatory reaction to tissue.Conclusion n-HA showed good biocompatibility than AH-plus in vivo, no cytotoxicity with the testcells, good antibacterial effect to P.gingivalis, F.nucleatum and P. intermedius,. a certain extent apical root canal sealing ability.Based on these findigs, n-HA had showed some ability,which Satisfied the need of root canal filling sealer.Futher researches are n eeded to bring more explicit insights into the properties of this material,and make better use of it.