| BackgroundBiodentine is specifcally designed as a new type of biological ceramic dentin substitute materials.It is a calcium silicate based product and effectively formulated applying the Mineral Trioxide Aggregate(MTA)-based cement technology and the amelioration of some properties of these types of cements.Compared with MTA,Biodentine has the advantages of more convenient operation,short setting time,low microleakage rate and good marginal integrity.Owing to its favorable mechanical properties which is semble to natural dental tissue and higher mechanical strength,Biodentine has a wide range of applications such as repair of perforation of pulp floor and lateral wall of the root canal,pulpotomy,apexification,retrograde filling,resorptive lesions and root canal obturation and so on.some scholars’ study shows that Biodentine has the ability to form hydroxyapatite crystals at the surface and permeate into the dentinal tubules,closely contact with the dentin and engender mechanical retention,greatly reducing the marginal microleakage and prevent pulp tissue infection and necrosis.However,as a root canal filling material,Biodentine exists in the root canal for a long time,there are relatively few research on Biodentine’s and MTA’s penetrability and its influence on the dentin’s fracture resistance.monoblock represents a new trend in the development of root canal therapy.monoblock emphasizes the improvement of the sealing ability of root canal filling and the good fluidity of the filling material making it possible to penetrate into the dentinal tubules to form mocromechanical retention,and enhance the fracture resistance of the teeth.As a root canal filling material,it plays an important role in the monoblock.In summary,Biodentine may enhance or restore the fracture resistance of dentin.in this study,we chosed isolated teeth as experimental subjects to explore Biodentine and as root canal filling materials exist in the root canal,its penetration into dentinal tubules and its effects on the dentine’s fracture resistance,and compare with MTA.provided theoretical evidence of some biomechanical properties for the clinical application of Biodentine in the treatment of endodontics diseases.ObjectiveTo establish a model of Biodentine and MTA as root canal filling materials which are filled in isolated root canals and detect Biodentine and MTA in the maximum depth and percentage of penetration into dentinal tubules and dentin’s three-point flexural strength and flexural modulus.to provided theoretical evidence of some biomechanical properties for the clinical application of Biodentine in the treatment of endodontics diseases.Materials and methodsPart I Observation of Biodentine which were penetrating into dentinal tubules under scanning electron microscopicWe collected 45 single-rooted isolated human premolars and randomly divided them into three groups:Biodentine,MTA,Vitapex.each group of 15.They were decoronated at the cementoenamel junction(CEJ)and sectioned to a standardized length of 12 mm.all specimens were completed the root canal preparation and then respectively obturated with seals.the specimens were immersed in PBS solutions at room temperature for three months.Each tooth removed a 1-mm-thick section at 1 and 5 mm from the root apex.all sections were imaged using a scanning electron microscopic at 5 x magnification.recorded the depth of sealers penetration and the results were statistically analyzed.Part II Measurement of Biodentine in the penetrative maximum depth and percentage of penetration into dentinal tubulesWe collected 60 single-rooted isolated human premolars and randomly divided them into four groups:Control group,Biodentine,MTA,Vitapex.They were decoronated at the cementoenamel junction(CEJ).all specimens were completed the root canal preparation and then respectively obturated with seals.the specimens were immersed in PBS solutions at room temperature for three months.For fluorescence,sealers were admixed with a trace(barely detectable)amount of rhodamine B isothiocyanate,after two weeks,all specimens were fixed with 4%paraformaldehyde for 5 days.Each tooth removed a 1-mm-thick section at 1 and 5 mm from the root apex.all sections were imaged using a confocal laser microscope at 5 ×magnification.The maximum depth of sealer penetration and the percentage of sealer penetration were measured applying NIS-Elements 4.2 imaging software and Photoshop cc 2016.the results were statistically analyzed.Part Ⅲ Influence of Biodentine on the dentin’s three-point flexural strength and flexural modulusWe collected 48 canines as experimental subjects.decoronated them at the cementoenamel junction and removed all cementum,performed apicoectomy,ratained the middle of roots as specimens.and the defective dentin specimens were removed.a total of 40 samples were obtained from the inclusion criteria.40 experimental specimens were randomly divided into 5 groups,each group of 8 and were numbered A,B,C,D,E group.Group A was positive control group without any treatment,the other four groups of experimental specimens were gone through pulp extirpation and root canal irrigation.group B did no root canal obturation;group C,D,E of root canals were filled with Biodentine,MTA,Vitapex paste respectively and both ends were sealed with flowable resin.all the samples were soaked in 0.9%sodium chloride solution and kept in the carbon dioxide incubator for 37℃.three-point flexural strength and flexural modulus of the specimens were measured after three months using universal testing machine.Results1.Wilcoxon rank sum test showed that the endodontic sealers penetrated both deeper and more well-distributed of the canal at the 5-mm level compared with 1-mm level(P<0.05);Mann-Whitney U obtained the difference of penetrative maximum depth of all materials was not statistically significant at the 1-mm level(p>0.05);these two groups had a significant difference(p<0.05)in the penetrative maximum depth at the 5-mm level:Control group between Biodentine,MTA and Vitapex respectively;Vitapex between Biodentine and MTA separately;however,there were no statistically significant in the difference between Biodentine and MTA(p>0.05).2.The mean value of the percentage of penetration of each material at the 5-mm level was significantly greater than that of at the 1-mm level(p<0.05);the mean value of the percentage of penetration at the 5-mm level in the control group was 26.4%,which was much less than that of the other three groups and the differences had statistically significant(p<0.05);Mann-Whitney U showed that the difference of the percentage of penetration of all materials was not statistically significant at the 1-mm level(p>0.05);the percentage of penetration of Biodentine and MTA at the 5-mm level were 78.8%and 72.3%respectively and the difference had statistically significant(p<0.05).3.Obtained the maximun load value of each specimen.the three-point flexural strength of each group was analyzed by single factor analysis of variance using SPSS 20 statistical software,and F=6.74(p<0.05);Comparison between each two groups using LSD method showed that the three-point flexural strength of group A had statistically significant between group B,D,E respectively(p<0.05);the dirrerence of these two groups’ three-point flexural strength also had statistically significant(p<0.05):group B and group C,group C and group E,group D and group E;but,the dirrerence between group C and group D had no statistically significant(p>0.05).4.Obtained the maximum load value of each specimen.the flexural modulus of each group was analyzed by single factor analysis of variance using SPSS 20 statistical software,and F=6.74(p<0.05);Comparison between each two groups using LSD method showed that there were significant differences(p<0.05)between each two groups except for group C and group D.Conclusions1.In this study,Biodentine and MTA were successfully established as root canal filling materials in vitro.The successful establishment of the model could be used to test the permeability of endodontic materials and the fracture resistance of dentin.2.Biodentine,MTA and Vitapex particles were densely attached to the dentinal tubules and the surfaces of the tubules.No damage and corrosion had appeared in dentin and dentinal tubules.However,some particles of Biodentine and MTA had penetrated into the dentin’s collagen fibers,and penetration depth of Vitapex was less than Biodentine and MTA.3.Experimental datas showed that the mean value of the penetrative maximum depth and the percentage of penetration of each material at the 5-mm level was significantly greater than that of at the 1-mm level;in reference to the penetrative maximum depth,there was no significant difference between Biodentine and MTA in the permeability at the 5-mm level;however,when it comes to the percentage of penetration,There was significant difference between Biodentine and MTA in the permeability at the 5-mm level.4.There was no significant difference between Biodentine and MTA on the fracture resistance of dentin;compared with the positive control group,Biodentine and MTA did not increase or recover dentine’s fracture resistance;but compared with the blank control group and Vitapex paste,Biodentine and MTA can increase the fracture resistance of dentin. |
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