| Objective: The adhesive strength of zirconium oxide ceramic brackets was measured by an in vitro tooth mechanics experiment,and the difference between the bond strengths of metal brackets and alumina ceramic brackets was compared,which provided a reference for the clinical application of zirconium oxide ceramic brackets.Materials and methods: 80 Extracted premolars for orthodontic treatment were collected and randomly divided into A,B and C groups(20 in group A,30 in group B,30 in group C).Group A adhesive straight wire metal bracket(Shinye,China),Group B bonded single crystal alumina ceramic brackets(Protect,China),Group C bonded zirconia ceramic brackets(Blanc,China).Respectively,Group A brackets were divided into A1(10),A2(10)due to the difference of light curing angle.Group A1 was cured 20 seconds at each mesial and bistal surface and the group A2 was vertically cured 40 seconds.Group B was randomly divided into B1(10),B2(10),B3(10)with the difference of cure angle and time.Group B1 was cured 20 seconds at each mesial and bistal surface,group B2 was vertically cured 40 seconds and group B3 was vertically cured 20 seconds.The experimental groups in group C were the same as those in group B.Group A,B and C were bonded with Transbond XT.The isolated teeth bonded with brackets placed in water environment at 37 ℃ for 24 h,shear force was applied on the bracket in a direction of parallel brackets bottom,and the shear force was recorded when the bracket fell off.The shear force divided by the floor area of the bracket was the shear bond strength of the bracket.the ARI index of each group(Adhesive remnant index,residual adhesive index of tooth surface)was also recorded.The data of each group were analyzed statistically to compare the brackets bonding strength and ARI index between different brackets and different curing methods.Results: Compare between groups(1)cure 20 s in each mesial and bistal surface of bracket,The Shear bond force of A1,B1 and C1 groups were not exactly same(P<0.05).The pairwise comparison shows that the Shear bond force of zirconia bracket is slightly lower than that of metal bracket and alumina bracket.The difference is statistically significant(P<0.05).There was no significant difference in Shear bond force between metal brackets and alumina brackets(P>0.05).However,there was no significant difference in shear bond strength and ARI between the three brackets(P>0.05).(2)The group with vertical curing for 40 s,the Shear bond force of A2,B2 and C2 groups were not exactly same(P<0.05).The pairwise comparison shows that the Shear bond force of zirconia bracket is slightly lower than that of metal bracket,and the difference is statistically significant(P<0.05).There was no significant difference in Shear bond force between zirconia bracket and aluminum oxide bracket(P>0.05).There was no significant difference in shear bond strength and ARI between the three brackets(P>0.05).(3)The group with curing for 20 s,There was no significant difference in Shear bond strength,Shear bond force and ARI between B3 and C3 groups(P>0.05).In-group comparison(1)For groups A、Band C,when the curing time is the same and the curing angle is different,there was no significant difference in Shear bond strength and Shear bond force of brackes(P>0.05).For metal brackets and alumina brackets,there was no significant difference in ARI after treatment at different light angles(P>0.05).However,for zirconia brackets,the ARI of the group with vertical curing for 40 s was slightly lower than that of the group with 20 s in the mesial and bistal surface of bracket,and the difference was statistically significant(P<0.05).(2)For group B and C(Aluminum bracket group,Zirconia bracket group),there was no significant difference in Shear bond force,Shear bond strength and ARI after different light curing time.(P>0.05).Conclusion:(1)The Shear bond strength of zirconia bracket,metal bracket and alumina bracket have no different from based on the different light curing time and different light curing angle,and all satisfy the clinical application.(2)For the three brackets,when the light curing time is 40 s,vertical light curing and curing at the mesial and bistal surface of bracket will not affect the bonding strength of brackets.(3)For the two kinds of ceramic brackets,there is no difference in bonding strength between light curing for 20 s and light curing for 40 s,and both satisfy the requirements of clinical application. |
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