Comparison Of Shear Bond Strength And Microleakage Of Rebonded Metal Brackets Using Differernt Adhesives: An In Vitro Study

Objectives:The aim of this study was to evaluate the shear bond strength and microleakage of rebonded stainless steel orhodontic bracktes using three different adhesives.Methods:300 human premolar teeth extracted for orthodontic purposes were divided to 3 groups:A for Jingjin enamel adhesive (Jingjin), B for 3M Unitek TransbondTM XT (3M), C for GC Fuji orthoTM LC (GC). In part One, chose 120 sample teeth randomly divided into six groups, group A0, B0, C0 (n=20) served as the control groups, witch were exposed to artificial saliva for 24h. Group A1, B1, C1 (n=20) as experimental groups, witch were standard thermocycling and fatigue cycle to simulation using intro-oral a year later. Both the experimental and control groups were then subjected to shear bond strength (SBS) test using an Instron Universal Testing Machine. and to recored ARI (Adhesive Remnant Index, ARI). In part Two, the rest of 180 sample teeth with bonding bracket were used to rebounded bond new premolar metal brackets. Each group was then further divided into three sub-groups named after adhesives (A for Jingjin, B for 3M, C for GC):AA、AB、AC、BA、 BB、BC、CA、CB、CC. All the samples were then subjected to standard thermocycling and fatigue cycle to to simulation using intra-oral a year laterc, shear bond strength (SBS) test were measured using an Instron Universal Testing Machine.and so as the ARI (Adhesive Remnant Index, ARI). In part Three, chose 5 samples from each group A1、B1、C1 as control groups and 5 sample teeth from rebonded groups as experimental groups. All the samples placed in 0.1% Rhodamine B isothiocyanate for 40min, sectioned, evaluate and photographed by Macro confocal microscope (MCM). Microleakage was scored at the enamel-adhesive interface and the bracket-adhesive interface from both occlusal and gingival margins. And the microleakage arer from both occlusal and gingival and the average arer were used to quantitative analysis microleakage. Statistical analysis was accomplished with SPSS 20.0.Results:1、The shear bond strength of the control group A0、B0、C0:there were significant difference among the three groups,and for the pairwise comparisons, there were significant difference between A0 and B0,B0 and C0. There were significant difference in the adhesive remnant index A0<B0、C0 (P<0.05)2、For the control group A1、B1、C1:There were significant differences among the three groups in shear bond strength. And for the pairwise comparisons, there were significant difference between A1 and B1, A1and C1 (P<0.05). There were no significant difference in the adhesive remnant index (P>0.05).3、For the shear bond strength,there were significant difference between A0 and A1, BO and B1 (P<0.05), There were no significant difference between CO and C1 (P >0.05)4、For the rebounded groups, there were significant difference in shear bdnd strength, and for the pairwise comparisons, there were significant difference between AA and AB、B1 and BA,, BA and BB, BA and BC, BB and BC, C1 and CA, CA and CB, CA and CC, CB and CC (P<0.05). There were no significant difference between A1 and AA, A1 and AB,A1 and AC, AB and AC, AA and AC, B1 and BB,B1 and BC, C1 and CB, C1 an dCC (P>0.05)5、For the microleakage arer, the results indicate statistically significant differences between the gingival and occlusial, and the gingivl arers are lager than occlusial (P <0.05)6、For the average microleakage ares, there were significant difference among the three groups. And for the pairwise comparisons:AA>BA、CA、AB>AC、CB、 BB>BC、CC>A1>B1、C1(P<0.05)7、At the enamel-adhesive interface, the occlusial side is lager than gingivl side hassignificant differences (P<0.05). There were significant differences among thegroups, and for the pairwise comparisons:AA、BA、AB>BB、CA、BC>AC、 CB、CC>A1、B1>C1 (P<0.05).8、At the bracket-adhesive interface, There were significant differences among the groups, and for the pairwise comparisons:AA、A1、BA、CA>AB、B1、BB、 CB>BC、AC、C1、CC (P<0.05).Conclusion (s):1、The shear bond strength mesured 24h is larger than using a yaer later. And for the first bond, bond with 3M resin or GC can offer better shear bond strength than Jingjin at 24h. and GC is better than 3M afer a year later.2、The first bonding shear bond strength is lager than rebonded’s and they can both attach the clinical need. The teeth bonded with Jingjin before, use GC or 3M to rebond can offera better shear bond strength. Bond with 3M before, use GC rebounded can offer the largest shear bond strength. Bond with GC before, use 3M or GC both can offer a prefect shear bond strength.3、All of the brackets exhibited some amount of microleakage. Rebound groups results in more microleakage than first bond groups both tooth-adhesive and A significant difference was observed that gingival microleakage arer is larger than occlusial. Use Jingjin first bond has larger microleakage than 3M or GC.4、At enamel-adhesive interface, microleakage at gingival is larger than occlusial side. Use 3M rebond has lareger microleakage at enamel-adhesive interface than other adhesive.5、At bracket-adhesive interfaces, microleakage at occlusial side is larger than gingival side. Use GC rebond espressed less microleakage than other adhesives. The amount of the microleakage at bracket-adhesive interface. This result means that microleakage at bracket-adhesive interface does not depend on first bond or rebond, but on the type of adhesive used.