Experimental Investigations Of Infiltrant Used To Seal The Pit And Fissures Of Permanent Molar

ObjectiveTo research the microleakage,microgap and shear bond strength of infiltrant used to seal pits and fissures of permanent molars,and to compare it with other common sealants,to explore whether infiltrant can be used to seal fissures,as to provide certain reference information for the selection of sealing materials in clinical practice.Methods125 no-caries third molars with deep fissures were randomly divided into 5 groups.Group A:pit and fissure sealant（Helioseal F）;Group B:glass ionomer（GC FUJI Ⅶ）;Group C:flowable composite（3M Z350XT）;Group D:infiltrant（15%hydrochloric acid atching for 2min+infiltrant）;Group E:soft-atching infiltrant（35%phosphoric acid etching for 30s+infiltrant）.1.Microleakage of different groups50 teeth were randomly divided into 5 groups and 10 teeth in each group were sealed with different materials and etchants.and then 500 cold-heat cycles were carried out to imulate aging.Teeth were stored in 2%methylene blue solution for 24hours and specimens were sectioned and measured the pencentages of dye penetration under stereomicroscope.2.Microgap of different groupsDifferent materials and etchants were applied to seal the pits and fissures in each group.The crowns were bucco-lingually sectioned into two fragments with a high-speed precision saw.30 sections in total were gold-sputtered and inspected by SEM.2mm area in the middle of the fissure was selected and the width of microgap between the sealing material and the enamel surface was measured under high power electron microscopy（5000X）.3.SBS of different groupsA cyclinder of 2.38mm diameter and 5.00mm height was formed on the smooth surface for the preparation of SBS test.Then,the SBS test was carried out in the universal testing machine and the failure mode was analyzed under the stereomicroscope.4.Statistical analysisThe experimental data were analyzed by SPSS20.0 statistical software and theStatistical data were expressed as mean+standard deviation.Normal test and homogeneity test of variance were conducted first.If normal distribution and homogeneity of variance were followed,analysis of variance was used for comparison between groups.If it is subject to normal distribution but does not comply with homogeneity of variance,Welch test is used for comparison of population mean,and then Dunnett T3 test is used for pair comparison.If normal distribution and homogeneity of variance were not followed,Kruskal-Wallis H test was used for comparison among groups,and Mann-Whitney U test was used for pairwise comparison between groups,p<0.05 for the difference was considered statistically significant.Result1.Group B exhibited the worst microleakage than other groups and the difference was signficant（P<0.0001）.The microleakage of groups A and C was significantly higher than that in groups D and E（P<0.05）,but there was no statistical significance between groups A and C,D and E（P>0.05）.2.The widths of microgap in group A,group B,group C,group D,group E were 2.11±0.69 μm,23.94±3.29 μ m,1.48±0.39 μ m,0.67±0.27 μ m and 0.61±0.23 μ m,respectively.Among them,group B exhibited the largest microgap while group E exhibited the smallest.The microgap of Group B was significantly larger than that of other groups（P<0.0001）,group A and C were significantly larger than group D and E（P<0.05）,but there was no statistical significance in the width of microgap between group A and C,group D and group E（P>0.05）.3.The average values of shear bond strength in group A,group B,group C,group D and group E were 12.75±5.73Mpa;4.18±1.09Mpa,19.56±5.18Mpa,14.68±3.85Mpa and 11.40±2.79Mpa respectively.Among them,group C exhibited the highest SBS while group B exhibited the lowest.The SBS of group B was significantly lower than that of other groups,and the difference was statistically significant（P<0.01）.The SBS of group C was significantly higher than that of groups B and E（P<0.05）but was a little higher than that of groups A and D（P>0.05）.The mean values of group A,D and E were similar,and there was no statistically significant difference.In the analysis of the fracture mode,adhesive failure was the most predominant failure type in all groups,ranging between 70%and 90%,follwed by mixed failures,which ranged between 10%and 30%.Conclusion1.Microleakage was inevitable in each group,glass ionomer performed the most serious,followed by resin-based sealant and flowable composite.Infiltrant applied with 15%hydrochloric acid etching for 2min or 35%phosphoric acid etching for 30s performed best in microleakage.2.Glass ionomer exhibited the widest microgap,followed by resin-based sealant and flowable composite.Infiltrant applied with 15%hydrochloric acid etching for 2min or 35%phosphoric acid etching for 15s performed best in microgap.3.The SBS of flowable composite was the highest,and the resin-based sealant and can achieve better SBS as well as infiltrant no matter what etchant was used.The SBS of glass ionomer is the lowest.