| [Objective]To explore the influence of different acid etching conditions on enamel surface and to select the treatment conditions for early acid etching enamel samples.On this basis,the preventive effect of adhesive and Infiltrant resin on early erosive enamel wear was studied,to provide certain reference for clinical application.[Material and methods]180 freshly extracted premolars were collected,embedded and fixed on the slow cutting machine after treatment,and enamel slices with a certain thickness on the buccal surface were cut.And screening according to the following conditions:(1)under the stereoscopic microscope(10 times)observation,exclude caries,hidden crack,demineralization of the samples;(2)for microhardness measurement,selected 110 pieces of enamel with the closest hardness value as samples.The sample enamel surface was polished using silicon carbide sandpaper under flowing water and then polished using a polishing film.Ultrasonic washing to remove the sample surface contamination,air gun to blow dry,retained and set aside.Hydrochloric acid solutions with pH values of 1.6,2.4,3.2 and 4.0 were prepared respectively.80 samples were selected and half of the glazed surface was sealed with adhesive tape as the untreated surface and the other half as the treated surface.Samples were randomly divided into the following 8 groups for treatment:4 groups with etching time t=30s,pH=1.6,2.4,3.2 or 4.0(labeled as A1,A2,A3 and A4 group in sequence);and 4 groups with etching time t=60s,pH=1.6,2.4,3.2 or 4.0(labeled as B1,B2,B3 and B4 group in sequence).After treatment,the samples were rinsed with deionized water for 30s,and then the surface tape was removed.The microhardness of untreated and treated surfaces were measured by vickers microhardness tester.Laser scanning confocal microscopy was used to measure the height difference(enamel loss)between the two surfaces before and after treatment.The treatment conditions of early erosive enamel samples were screened out by statistical method.On this basis,30 samples were selected and half of the glazed surface was sealed with adhesive tape as the untreated surface and the other half as the treated surface.The treatment surface of the sample was treated with the above early erosive treatment conditions.After treatment,the samples were rinsed with deionized water for 30s.The samples were randomly divided into 3 groups according to the application of material or not and the type of material:blank group(no treatment on treatment surface),adhesive group(Singlebond adhesive on treatment surface)and Infiltrant resin group(Icon infiltrant resin on treatment surface).A 30-day cycle of erosion-abrasion(acid etching+brushing)was performed on the samples.In addition to this time,put the samples in artificial saliva.Laser scanning confocal microscopy was used to measure the thickness of enamel or material and 3d surface roughness before and after the erosion-abrasion cycle.SPSS 24.0 software was used to test the normality and homogeneity of variance of the data,followed by t test and variance analysis.The test level was α=0.05.[Results]1.Effects of different acid etching conditions on the hardness of enamel surface After acid etching treatment,the hardness values(MPa)of treatment surfaces of group A1 to A4 decreased(43.0±5.95),(26.3±5.35),(12.1 ±6.46)and(0.6±3.04),respectively;and the hardness values(MPa)of treatment surfaces of group B1 to B4 decreased(60.5±6.49),(36.3±7.47),(18.5±6.06)and(9.3±4.5 0),respectively.Among them,the hardness values between the untreated and treated surfaces in the A4 group showed no significant statistical significance(P>0.05).2.Effects of different acid etching conditions on the tissue loss of enamel surface After acid etching treatment,laser scanning confocal microscopy observation showed that the enamel loss of treatment surface in group A1 to A4(nm)was(801.9±48.0),(325.3±36.1),(15.5±3.4)and(-0.2±2.5),respectively;and the enamel loss of treatment surface in group B1 to B4 was(1199.1±222.5),(435.6±45.0),(75.9±8.7)and(1.7±3.5),respectively.There was no significant tissuel loss on the enamel treatment surface in A4 or B4 group(P>0.05)3.Changes of surface roughness before and after erosion-abrasion cycle in different groupsThere was no significant difference in surface roughness(P>0.05)between each group,which was about 0.67 μm.The surface roughness of the infiltrant resin group increased to(3.490±0.040)μm after the application of the material.The surface roughness of the adhesive group did not increase significantly after the application of the material,approximately(0.665±0.108)μm.After 30 days of erosion-abrasion cycle,the surface roughness of the treated surface in the control group increased to(5.100±0.469)μm.The surface roughness of the infiltrant resin group increased to(3.947±0.109)μm.The surface roughness of the treated surface in the adhesive group showed no significant change,which was(0.70410.053)μm(P>0.05).The surface roughness of the treated surface in the three groups was as follows:control group>infiltrant resin group>adhesive group.The difference was statistically significant(P<0.05).4.The preventive effect of different materials on early erosive enamel wearAfter the material was applied to the treatment surface,the thickness of material on enamel surface in infiltrant resin group and adhesive group was about 14.02 μm and 10.62 μm,respectively.After 30 days of erosion-abrasion cycle,the amount of acid erosive wear on the treated surface of the control group reached 29.71μm in the control group,5.61 μm in the infiltrant resin group,and 2.87 μm on the treated surface of the resin adhesive group-The lower enamel of the two groups of applied materials were not further affected by the erosion-abrasion cycle.The material loss ratio(material loss thickness/total material thickness)of the infiltrant resin group and the adhesive group was 41%and 29%,respectively,with statistically significant differences(P>0.05).The infiltrant resin group resulted in about 13 μm loss of enamel in the process of material application.[Conclusion]1.Acid etching treatment could cause the reduction of microhardness of the treated surface of samples.Within a certain range,the decreasing value of surface microhardness increases with the decrease of pH value or the prolongation of acid etching time.2.Acid etching treatment could cause tooth tissue loss on the treated surface of samples.Within a certain range,the amount of enamel loss increases with the decrease of pH value or the prolongation of acid corrosion time.3.When pH=4.0 and t=60s,the microhardness of the sample treatment surface decreased,but there was no obvious height difference.In other words,the surface of the sample softened without loss of dental tissue.4.The surface roughness of the control group increased after erosion-abrasion cycle.After application and erosion-abrasion cycle,the surface roughness of infiltrant resin group increases gradually.The surface roughness of the adhesive group does not change obviously after application and after erosion-abrasion cycle..5.Compared with the infiltrant resin,the Singlebond resin adhesive has better short-term protection against early erosive enamel wear.6.Singlebond resin adhesive has less damage to enamel in the process of application,and the effect is better. |
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