Reducing Losing Ratio Of The Bond Orthodontic Brackets To Heavy Fluorotic Teeth In Clinic And Vitro Study

Direct bonding technique is common in orthodontic clinic. Losing ratio of bracket is a disadvantage for direct bonding bracket technique,especially for fluorotic teeth.Because fluorotic teeth enamel with hight fluorin can be resist acid and abrade force , it is easy to make the bracket losing .The purpose of this study was to compare bonding destruction force of orthodontic brackets to fluorotic teeth in vitro to normal teeth. To investigate the effect of bracket bonding of heavy fluorotic teeth with the light-curing composite to reduce losing ratio of the brackets in orthodontic clinic, the experiment was designed with the light-curing composite sticking to bond bracket for increasing bonding strength of orthodontic brackets to fluorotic teeth. Methods1. Experiment in vitro: sixty extracted heavy fluorotic teeth were chosen as experiment group and twenty normal teeth as control group. According to the differente treatment of enamel surface, the fluorotic teeth were further divided into direct bonding of bracket to fluorotic teeth group ; bonding of bracket to polished fluorotic teeth ; bonding of bracket to veneers of fluorotic teeth.Each group includes twenty teeth. Edgewise brackets were bonded on each tooth. The shear and tensile bond destruction force of four groups were tested by material testing machine. The adhesiveremnant indices were recorded.2. Experiment in clinic: 324 heavy fluorotic teeth in seventeen patients who need using fixed appliance for orthodontic treatment were chosen. According to the different treating methods of fluorotic teeth enamel surface , the teeth were divided into three groups randomly: direct bonding of bracket to fluorotic teeth group(96) ;bonding of bracket to polished fluorotic teeth(112) ;bonding of bracket to veneers of fluorotic teeth(116). Losing ratio of brackets were observed after four ,eight and twelve weeks. Results1. Experiment in vitro indicate : there were statistically significant difference in both shear and tensile bond destruction force among four groups (P<0.01). There are the most shear force (329 30.2) and tensile force (163.1 15.2) in bonding of bracket to veneers of fluorotic teeth group.Failure site was primarily at the adhesive-bracket interface to normal teeth and bonding of bracket to polished fluorotic teeth group. Direct bonding of bracket to fluorotic teeth group was primarily at the enamel-adhesive interface.2. Experiment in clinic indicate : there were significant difference in losing rate of the bond edgewise brackets after four ,eight and twelve weeks respectively (P<0.01). Direct bonding of bracket to fluorotic teeth group bonded 96 brackets that the losing ratio of bracket was 73.9%. Bonding of bracket to polished fluorotic teeth group bonded 112 brackets that the losing ratio of bracket was 26.7%. Bonding of bracket to veneers of fluorotic teeth group bonded 116 brackets that the losing ratio of bracket was 1.7% . The effect of bonding of bracket to veneers of fluorotic teeth was the best in three groups. Bonding of bracket to veneers of fluorotic teeth group was better than bonding of bracket to polished fluorotic teeth group. Bonding of bracket to polished fluorotic teeth group was better than direct bonding of bracket to fluorotic teeth group.ConclusionThe shear bond destruction force and the tensile bond destruction force in bonding of bracket to veneers of fluorotic teeth was stronger than normal teeth.Six(116) heavy fluorotic teeth patients with the light-curing composite sticking to bond bracket for period of treatmet was working normal.The losing ratio of edgewise brackets was significantly reduced in veneers of fluorotic teeth with the light-curing composite,this method can be used in fixed multibrackets appliance.This method provides a new technique for orthodontic bracket bonding directly to fluorotic teeth.