Study Of Rebonding Strength With Processing Enamel And Bracket

Objective: To investigate the clinical loss rate of brackets and the shear bond strength ofbrackets, using three different processing methods on debonded enamel, and with newbracket or recycled brackets which were burned. Clinic and experimental results werecombined to explore the processing methods.Methods:Experiment in vitro:70extracted premolars were collected,70edgewise bracketswere bonded, shear bond strength of10premolars as control group (group A) were tested.60premolars’ brackets were debonded using pliers and randomly divided into six groupswere processed: group B1,the enamel was cleaned using tungsten carbide bur with newbracket; group B2, the enamel was cleaned using tungsten carbide bur with recycledbrackets which were burned; group C1,the enamel was cleaned using tungsten carbide burand polishing with new bracket; group C2,the enamel was cleaned using tungsten carbidebur and polishing with recycled brackets which were burned; group D1, the enamel wascleaned using silicon particles with new bracket; group D2,the enamel was cleaned usingsilicon particles with recycled brackets which were burned. The shear bond strength ofevery group was tested.Clinical trial: The research objects were selected from department of stomatology, theFifth Affiliated Hospital of Zunyi Medical College from2012to2013.8patients’52premolars as control group(group E) were first bonded,101patients’145premolars thatdebond were bonded and randomly divided into six groups were processed, group F1, theenamel was cleaned using tungsten carbide bur with new bracket; group F2,the enamel wascleaned using tungsten carbide bur with recycled brackets which were burned; groupG1,the enamel was cleaned using tungsten carbide bur and polishing with new bracket;group G2,the enamel was cleaned using tungsten carbide bur and polishing with recycledbrackets which were burned; group H1,the enamel was cleaned using silicon particles withnew bracket groupH2, the enamel was cleaned using silicon particles with recycled brackets which were burned. Three months later, debonding brackets were recorded, thento calculate the loss rate of brackets.Results:Experiment in vitro: the mean shear bond strength of every group, group Awas15.73±2.74MPa; group B1was12.67±3.99MPa; group B2was10.92±3.49MPa; groupC1was11.90±4.75MPa; groupC2was9.0±1.45MPa; group D1was9.0±3.75MPa; group D2was7.92±2.93MPa.There were significant difference in group A and group C1,groupD1,groupB2, group C2, group D2, respectively（P<0.05）. There were significant differencein group B1and group D1, group B2and group D2（P<0.05）. There were no significantdifference ingroupB1and group C1, group C1and group D1, group B2and group C2,group C2and group D2(P﹥0.05). There were no significant difference in group B1andgroup B2, group C1and group C2, group D1and group D2(P﹥0.05).Clinical trial: The loss of brackets, group E was10/52(19.23﹪);group F1was7/29(24.14﹪); group F2was7/28(25.00﹪); group G1was5/22(22.73﹪); group G2was6/25(24.00﹪); group H1was6/23(26.09﹪); Group H2was5/18(27.78﹪).There was nosignificant difference between groups(P﹥0.05).Conclusion:1. Inital bonding strength more than rebonding strength, The mean shear bondstrength of six methods processing enamel and bracket was more than that recommended.2. New brackets can be replaced with recycled brackets which were burned.