Effect Of Modification In Bonding Protocols On Bond Strength In Metallic Brackets

Objective: The fixed orthodontic appliance treatment is widely used in the dental clinic.Orthodontic forces cause the tooth to move thanks to bond an orthodontic appliance on the tooth surface.Many studies have shown that a problem during the bonding procedure between the orthodontic appliance and the tooth enamel will lead to the undesired bracket debonding that leads to longer orthodontic treatment times and affecting the orthodontic treatment efficiency.The purpose of this study is to compare the performance of two orthodontic bonding systems with different modification in the bonding process(extended enamel conditioning of 60 seconds and a delayed bonding of 5 minutes),analyzing the shear bond strength(SBS)and the adhesive remnant index(ARI)using in vitro techniques,in order to determine if these modifications to the bonding protocol that could be frequent happen in the daily work of the professional can generate a modification in the bonding strength values of the orthodontic adhesive to dental enamel,providing reference for orthodontic clinical treatment.Methods: 60 premolar teeth with metallic brackets(3M Victory Series)were bonded using two kinds of orthodontic bonding systems: 3M Unite? Bonding System and 3M Transbond XT? Light Cure Adhesive System.The enamel conditioning was done using Gluma Etch 35 acid gel.The 60 samples which match with the inclusion criteria were randomly divided initially into two groups based on each one of the orthodontic bonding systems in a study.The samples were embedded in an acrylic resin tube and subsequently cleaned after the bonding process of the bracket.Afterward,each group was further randomly subdivided into three groups of ten samples each(n = 10).More specifically groups I,II and III used the 3M Unite? Bonding System,while groups IV,V and VI used the 3M Transbond XT? Light Cure Adhesive System.Group I and group IV were the control groups and the adhesive was bonded according to the operating procedures recommended by the orthodontic bonding system manufacturer;groups II and V were made up of samples that treated with an extended enamel conditioning protocol of 60 seconds;and the groups III and VI consisted of samples that had a delayed bonding of 5 minutes with the saliva solution application to simulate the mouth environment.The shear bond strength test was performed in a laboratory with a Langrun WDW-1 tensile test machine equipped with a knife edge tool that is orientated parallel to the labial surface of the tooth to apply an occlusal-apical force,pressing the bracket-adhesive-tooth interface until the moment of the fracture of the adhesive.The maximum load(N)generated before the fracture is converted into pressure(MPa),to obtain the shear bond strength.Also,the remnant of adhesive on the teeth after debonding was also analyzed through standardized photographs using Photoshop CC 2019(Version 20.0.3)photo editing software to determine the adhesive remnant index.The data was characterized using Student’s t-distribution test analysis,one-way analysis of variance test(ANOVA)and chi-squared test using SPSS(Version 22).Results: The mean values of the SBS in MPa are as follows: Group I: 10.60 ± 4.55,Group II: 10.58 ± 4.34,Group III:13.77 ± 3.08,Group IV: 11.89 ± 5.44,Group V: 9.18 ± 3.27,and Group VI: 10.18 ± 5.14.The mean values of the SBS in MPa between the control groups(Groups I and VI)and the experimental groups(Groups II,III,V,and VI)present slight variations.The ARI values(Group I: 1.50,Group II: 1.50,Group III: 1.20,Group VI: 2.00,Group V: 1.90,Group VI: 1.30),did not yield differences are not statistically significant.Conclusion: There was no statistical difference in SBS and ARI between the adhesives and between the modified protocols studied.However,was observed that the samples bonded with 3M Unite? bonding system immersed in the saliva for 5 minutes after tooth surface etching have a shear bond strength after bonding slightly increased.While,the samples bonded with 3M Transbond XT? Light Cure Adhesive system with 60 seconds of etching time and 5 minutes delay after enamel conditioning have a shear bond strength slightly decreased.It is suggested that although there is enough time to adjust the position of the bracket using Transbond XT? light curing bonding system,an extended time of enamel conditioning and a delayed bracket bonding after enamel conditioning may affect the bonding strength of the bracket and enamel.