| Objectives It was aimed to do a preliminary research on the effect of household bleaching on the bonding strength of Jing-Jin enamel adhesive,3M Transbond light-cured resin adhesive,GC orthodontic glass ion adhesive.Enamel ultrastructure was observed at different time points after household bleaching,providing an experimental basis for better clinical connection of household bleaching and orthodontic bracket bonding.Methods 128 pulled bicuspids that were needed for orthodontics clinically were collected and divided into 12 groups randomly,each group having 10 specimens.Besides,8 teeth were selected to observe tooth enamel ultrastructure at different time points after household bleaching.A1,B1 and C1 groups were blank control groups,i.e.,they have no special treatment.They were immersed in artificial saliva,which was changed every day and they were bonded by brackets when doing the experiment.A2,B2 and C2 groups implement orthodontic bracket bonding immediately after household bleaching.A3,B3 and C3 groups were stored in artificial saliva after household bleaching and bond orthodontic brackets in one week.A4,B4 and C4 groups were stored in artificial saliva after household bleaching,and carried out orthodontic bracket bonding in 4 weeks.Group A used jing-jin enamel adhesive,Group B 3 M Transbond light-cured resin adhesive,Group C GC orthodontic glass ion adhesive.All the specimens were tested for the shear strength with hard brittle instrument and adhesive residue index on the surface of the teeth was calculated after brackets fall off.The collected data were analyzed using SPSS17.0software package.Results 1 The scanning results by scanning electron microscope showed that tooth enamel surface without household bleaching was flat,smooth and continuous and that the structure was uniform and compact without decalcification and dissolution,and that parts of them had visible shallow scratches,taking on the normal enamel surface form;The tooth enamel surface structure was observed immediately after household bleaching and they were found obvious change because the original normal enamel layer structure disappears and their surface became rough and rugged,with shallow pits,taking on a honeycomb structure,which was similar to the acid corrosion shape change;The teeth were stored for a week after household bleaching,then their enamel surface was scanned and observed,showing it was normal,and some parts were rough without obvious pit change;After the teeth were stored for 4 weeks after household bleaching,their enamel surface was scanned and observed and the structure was close to normal and fairly smooth and continuous.2 The test for the shear strength of the samples: in the experiment in Group A(Jing-Jin enamel adhesive group),the difference in the shear strength was significant.The brackets were bonded immediately after household bleaching,the difference in the shear strength between the experimental group and the control group was significant statistically with P<0.05.When the brackets were bonded in one week and four weeks after household bleaching,the difference in the shear strength was not significant statistically with P values 0.060 and 0.202 respectively compared with the control group.The average shear strength of the samples in A2 group was 5.63 MPa,which could not meet the clinical needs of the strength.In the experiment in Group B(3MTransbond light-cured resin adhesive),the average shear strength of the samples in Group B1 was 9.62 MPa,which was apparently higher than 7.72 MPa of the samples in Group B2,and their difference was significant statistically.But compared with 9.17 inGroup B3 and 9.76 in Group B4,the difference was not significant statistically.In the experiment in Group A(GC orthodontic glass ion adhesive group),the difference in the average shear strength between the four experimental groups was not significant statistically.3 The adhesive residue index: in the experiments in Groups A and B,the difference in the ARI scoring between the immediate bonding group and the control group was statistically significant and in the experiment in Group C,the difference between Groups C2,C3,C4 and Group C1 in ARI scoring was not statistically significant with P values > 0.05.Conclusions 1 10% carbamide peroxide household bleaching could lead to the microstructure of the enamel surface change and the rough surface demineralization.2After the brackets were bonded immediately following household bleaching,the shear strength of them that were bonded by resin adhesive was reduced considerably compared with the teeth without household bleaching,and even they could not reach the clinically required bonding strength.But the bonding strength by the resin reinforced glass ion adhesive was not affected.3 The shear strength of orthodontic bracket recovers and reaches the clinically required strength when they were bonded delayed one week after household bleaching. |
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