| Calcium hydroxide which is combined with low toxicity, good biocompatibility,wide antibacterial spectrum and the role of promotting periapical hard tissueformation has been widely used in clinical practice. Research shows that calciumhydroxide is dissolved into Ca2+ and OH- which are diffused in periapical tissuesto play a role. Robert established a periapical drug diffusion model in 2005. Thismodel is maded to be periapical simulation which analysis the concentration ofactive ingredient in root canal sterilization drug to evaluate the effect of drugdiffusion. The aim of this paper is to investigate different forms of calciumhydroxide diffuse throught different apical aperture in simulation model, differentconcentrations of calcium hydroxide diffuse throught the 40# apical aperture, andantibacterial effect to provide experimental basis to the clinical application ofcalcium hydroxide. This study is divided into two parts:Experimental diffusionstudy parts,with two expriments in part one. Expriment one focused on the diffusedeffects of three different forms of calcium hydroxide through various simulatedaperture. Experiment two invastigated the time-concentration curve of differentconcentrations of calcium hydroxide in periapical model simulated. In part ofexperimental study of the simulation model,which colonized pulp periapicalpathogens (such as F.nucleatum. P.endodontails, E.faecalis), inclose differentconcentrations of calcium hydroxide to observe inhibitory effects of drugs andantibacterial effects as compared with 0.02% chlorhexidine.The results showed: (1) Three different forms of calcium hydroxide root canalthrough various simulated aperture periapical spread to the effect of pH analysis, the proliferation of liquid calcium hydroxide group average pH values (8.26, S=0.86) ishigher than calcium hydroxide paste group(7.96. S=0.702) and calcium hydroxidespike group (7.83, S=0.59),also has a statistically significant difference (p＜0.05).The average pH value between calcium hydroxide paste group and calciumhydroxide spike group was no statistically significant difference (p＞0.05); Ca2+results showed that mean Ca2+ concentration of calcium hydroxide liquidgroup(29.87ppm. S=10.76), calcium hydroxide paste group (24.62ppm. S=10.40),calcium hydroxide spike group (16.42ppm. S=5.70), there were significantdifferences among the three groups (p＜0.05). The results also showed that theaverage pH values and the average calcium concentrations of different apicalaperture were statistically significant difference (p＜0.05), followed80#＞40#＞25#＞15#. (2) In different concentrations of calcium hydroxide periapicalmodel,the difussion of the time-concentration curve suggest that root canal inclosedifferent Ca(OH)2 paste group agar intracellular Ca2+ concentrations and pH valuesare significantly higher than control(P＜0.05), and Ca2+ concentration increasedgradtially over time, and it is to show a steady trend after 15 days, but agar pHshowed a continuing upward trend. There are significant difference among fourdifferent concentrations of Ca(OH)2 in pH and Ca2+ concentrations. At 15 days ofexperiment, the highest of drugs calcium and pH value is 30% of calcium hydroxidegroup, the minimum is 90% calcium hydroxide group, 10% and 60% calciumhydroxide groups have no significant difference (p＞0.05). (3) In the simulationperiapical model colonized pulp pathogens and then affixed to differentconcentrations of calcium hydroxide suggested that the inhibitory effects observed:(1) F. nucleatum. 10% calcium hydroxide and calcium hydroxide group was betterthan 30% and60% calcium hydroxide groups (P＜0.05). Inhibitory effect of 10%calcium hydroxide and 30% calcium hydroxide have no significant difference (p＞0.05). Inhibitory effect of 90% calcium hydroxide is not obvious. (2) P.endodontails,there are no significant difference among 10% calcium hydroxide group, 30% calcium hydroxide group and 60% calcium hydroxide group (p＞0.05). none of themis worse than 90% calcium hydroxide group. (3) E.faecalis, four differentconcentrations of hydrogen peroxide have no significant inhibitory effect. (4) 0.02%chlorhexidine solution to the inhibitory effects of these three bacteria significantly.Based on these findigs, we can reached the following conclusions: (A)suspension of calcium hydroxide in periapical model simulated has better effect onthe diffusion than calcium hydroxide paste and calcium hydroxide spike;the biggerof apical aperture, the better the effect of the diffusion of drugs. (B) Root canalinclose Ca(OH)2 have significant impacts on periapical Ca2+eoncentration and pH,different concentrations of calcium hydroxide have different impacts on periapicalCa2+ concentration and pH. The effects of the diffusion of 30% and 60%calciumhydroxide are better, and 90% calcium hydroxideis the worst. (C) calcium hydroxidehas good inhibitory effect on F. nucleatum and P.endodontails, but inhibitory effectis due to different concentrations.Calcium hydroxide has no significant inhibitoryeffect to E.faecalis; (D)0.02% chlorhexidine solution has good inhibitory effects ofthese three bacteria significantly.
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