| Experiment 1Penetration of Passive Ultrasound-Activated Na OCl Combined with EDTA Irrigation Solution in Infected Dentinal Tubules of Human TeethObjective To evaluate ex vivo the irrigant penetration of passive ultrasound-activated Na OCl combined with EDTA irrigation solution into dentin tubules of human teeth with infected root canals.Methods 48 root canals(24 infected root canals,24 clean root canals)were examined.All the root canals were prepared to 40~#06 and underwent a uniform passive ultrasonic irrigation flow.2%methylene blue solution was used for staining to visualize the penetration of irrigant.The EXAKT cutting and grinding equipment was used to take transverse sections of 100-150μm at the coronal,middle and apical thirds of the root canals.The data(median penetration depth,maximum penetration depth and penetration percentage)were observed under a light microscope to evaluate the effect of dye penetration.The difference of permeability between the infected and clean root canal groups were analyzed by Independent-Samples T test or non-parametric tests.The difference of permeability of different root canal sites(coronal,middle and apical)were analyzed by one-way ANOVA or non-parametric test.Data are expressed as“mean±standard deviation”or“median(first quartile,third quartile)”.P<0.05 was statistically significant.Results The median penetration depth,maximum penetration depth and penetration percentage of coronal sections of infected root canals were 0.0-343.9μm,0.0-660.7μm and 0.0-100.0%,respectively,which were significantly lower than 21.2-1057.8μm,150.9-1607.9μm and 69.6-100.0%of clean root canals(P<0.05).In middle sections,the median penetration depth,maximum penetration depth and penetration percentage of infected root canals were 0.0-68.1μm,0.0-635.6μm and 0.0-98.1%,respectively,significantly less than 32.3-584.3μm,142.9-840.7μm and 54.5-100%of clean root canals(P<0.05).For apical sections,the median penetration depth,maximum penetration depth and penetration percentage of infected root canals were 0.0-143.9μm,0.0-347.8μm and 0.0-98.4%,respectively,also significantly lower than 0.0-449.1μm,47.4-975.6μm and 42.5-100.0%of clean root canals(P<0.05).In infected root canals,the median penetration depth(9.0μm),maximum penetration depth(71.8μm)and penetration percentage(60.8%)of apical sections were all significantly lower than those in the coronal sections(22.1μm,248.3μm and 84.9%)(P<0.05),and the maximum penetration depth(71.8μm)and penetration percentage(60.8%)of apical sections were significantly lower than those in the middle sections(202.8μm and88.6%)(P<0.05),however,the difference between the penetration depth and penetration percentage of the middle sections and coronal sections was not significant(P>0.05).Conclusion The dentin permeability of infected root canals was weaker than that of clean root canals,and the dentin permeability of the apical sections was the worst in infected root canals.Experiment 2Dentin Structural Changes Affecting Dentin Permeability in Infected Root Canals of Human TeethObjective Dentine structural changes in infected root canals were observed histologically to investigate the relationship between root dentine permeability and its histopathological changes.Methods Transverse sections obtained in experiment 1 were processed to 20–30 μm and then stained with hematoxylin and eosin to observe the structural changes in the root dentin.Stained sections were evaluated under light microscopy and the incidence of structural changes was calculated.Differences in the incidence of structural changes in infected and clean root canals were analyzed by Pearson X2 test or Yates correction X2 test.P <0.05 was statistically significant.Results The formation of reparative dentin and sclerotic dentin was observed in both groups.In coronal,middle and apical sections of infected root canals,the incidence of the reparative dentin are respectively 85.00%,70.83% and 79.17%,more higher than that of clean root canals(8.33%,41.67% and 50.00%).In coronal and apical sections of infected root canals,the incidence of the sclerotic dentin are respectively 40.00% and75.00%,significantly higher than 8.33% and 29.17% of clean root canals(P <0.05).The incidence of sclerotic dentin in middle sections of infected and clean root canals was 50.00% and 29.17%,respectively,and the difference was not significant(P> 0.05).Conclusion Reparative dentin and sclerotic dentin have a higher incidence in infected root canals,which may will prevent the penetration of irrigant into infected dentin tubules. |
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