Biocompatibility And Sealing Ability Study Of A Solidifiable Calcium Hydroxide Canal Sealer

Root canal therapy is now the most effective method to cure acute/chronicpulpitis and periapical diseases. The last step of the method is to obturate theroot canal thoroughly which purpose is to eliminate dead space within the rootcanal and block the routes of infection. Furthermore, it can induce apical holeclosing effectively. Many studies have shown that root canal sealers areindispensable materials for appreciate obturation. Currently, zinc oxide kind,calcium hydroxide kind, silicone kind, resin kind, glass ionomer kind andnano-materials kind root canal sealers are most commonly used, however, thereis still few material to meet the ideal sealer kinds of requirements.Recently, Materials Dept. of Fourth Military Medical University hasindependently researched and developed a solidifiable calcium hydroxide rootcanal sealer which is a two-component paste. A component is Ca（OH）₂and Bcomponent is salicylic acid1,3-D diolesters. When the two components are mixed, they turn to solidification. The material has characteristics of solidificity,easily placement, the x-ray radiopacity and no teeth staining. However, whetherthe material can be used as a clinical root canal filling material needs a series ofexperimental studies to confirm.In this paper, cytotoxicity, tissue compatibility and apical sealing abilitywere tested and self-made Ca（OH）₂blocking agent was compared with severalcommonly used clinical sealers, such as MTA, AH Plus, Roeko Seal, Cortisomoland RC Sealer. Energy dispersive X-ray spectrometer analysis was adopted toinvestigate the material content of internal elements. Ultrastructure of the abovematerials were analyzed by field emission scanning electron microscope. Ourstudy can give an objective and comprehensive evaluation for the probability ofthe material for clinical use and provide relative theoretical basis.Experiment1In vitro cytotoxicity study of several root canal sealers byCCK-8Objective: To detect in vitro cytotoxic effects of MTA, AH Plus, Roeko Seal,Cortisomol, Ca（OH）₂in L-929cell line and evaluate cell biocompatibility.Methods: In this study, elemental analysis of MTA, AH Plus, Roeko Seal,Cortisomol, Ca（OH）₂were conducted by energy dispersive X-ray spectrometer.CCK-8was used to detect in vitro cytotoxic effects of L-929cells at twodifferent extract concentration （100%and50%） after immediate solidification or1week after solidification.Results: It showed that samples in AH Plus group of100%and50%in1weekgroup at day1,2and4had the significant difference （P <0.05）. The cell proliferation rate in50%concentration of extract group was highest whichrepresented the lowest cytotoxcity. The same parameter tested in other foursealers showed no significant difference （P>0.05）, namely cytotoxicity withouta significant change. The cell proliferation rate of Cortisomol group wascomparable with Ca（OH）₂group （P>0.05）. There was also no significantdifferences between the MTA group and Roeko Seal group （P>0.05）. However,AH Plus group showed statistically difference with other four groups （P <0.05）.Conclusion: MTA and Roeko Seal have the lowest, AH Plus is has moderatelycytotoxic, and Cortisomol and Ca（OH）₂, have similar cytotoxicity, but the gradeis less than three.Experiment2Biocompatibility of a solidifiable calcium hydroxide rootcanal sealer on subcutaneous and skull of ratsObjective: using rat subcutaneous implants and bone implants experiment tocompare biocompatibility of MTA, AH Plus and Ca（OH）₂.Methods:28adult male SD rats were randomly divided into4groups （n=7ineach group）. MTA, AH Plus and Ca（OH）₂were implanted in rats subcutaneouslyor within the skull.1,2,4,8weeks after subcutaneous implant or after2,4,8,12weeks after skull implant, material histocompatibility was examined.Results: Norplant experimental observation for the MTA showed inflammatoryreaction in MTA as Class I, except one week group and no statistical differencewas found compared with the negative control group （P>0.05）.1,2,4weeksafter operation, AH Plus and Ca（OH）₂group showed Class II inflammationreaction which is of statistically significance with negative control group （P < 0.05）. At week8, inflammatory response turned to Class I. Experimentalobservation of bone implants after2and4weeks with MTA showedfibrous connective tissue migration and osteoblasts were increased from week8.At week12, surface of the material tested was completely covered by new bone.At week2,4and8, fibrous connective tissue gradually enveloped the material inAH Plus and Ca（OH）₂group. At week12, some of the new bone surroundedthe split material and grew irregularly through the internal of the material.Conclusion: MTA has better biocompatibility in the rat subcutaneousconnective tissue and bone tissue. AH Plus and Ca（OH）₂is similar on thebiocompatibility of the rat subcutaneous connective tissue and bone tissueapproximation.Experiment3A quantitative glucose method by constant air pressure forevaluation of the sealing ability of several root canal sealersObjective: The aim of this study was to introduce a modified model forquantitative testing of glucose micro-leakage by constant air pressure andevaluate the sealing ability of four root canal sealers including AH Plus, RoekoSeal, Cortisomol, RC Sealer and Ca（OH）₂Sealer.Methods:68straight maxillary anterior teeth were randomly divided into fourexperimental groups of12samples each, in detail, group A: AH Plus, group B:Roeko Seal, group C: Cortisomol, group D: RC Sealer and group E: Ca（OH）₂Sealer and positive&negative control group of4samples each. After regularroot preparation, samples in experimental groups were obturated by using coldgutta-percha lateral compaction technique with sealers according to group description. Control groups were obturated with cold gutta-percha only. Throughthe above model, the value of glucose micro-leakage from crown to rootdirection was measured at day1,3,5,7,10,15,20,25and30with the glucoseoxidase （GOD） method.Result: At day1,3,5, no significant difference of micro-leakage value was foundbetween group A and B, so did group C, D&E （p>0.05）. From day7,micro-leakage value in each experimental group gradually increase, andstatistical difference was found between groups, except C and E （p<0.05）.Conclusion: this new model using constant air pressure is easy to establish,sensitive and practical. Among all the sealers evaluated, polydimethylsioxanebased root canal sealer, Roeko Seal has the greatest sealing ability, whileepoxy-amine resin based AH Plus is second, Ca（OH）₂Sealer has the samesealing ability with Cortisomol and RC Sealer.