To Compare Shear Bond Strength of Brackets Using Different Conventional Composites with Self Etching Primer and Its Effect on Early Orthodontic Loading: An In-Vitro Study.

Introduction: This study was conducted to evaluate the effect of applying early orthodontic force on the shear bond strength (SBS) of orthodontic brackets bonded with 4 adhesive systems. Methods: One hundred and twenty stainless steel brackets were bonded to enamel surface of extracted premolars with self etching primer and 4 conventional composites. For each adhesive 15 brackets were bonded without application of force (groups IA, IIA, IIIA, IVA) and another 15 were subjected to a 120gm force with a coil spring (groups IB, IIB, IIIB, IVB). This force was applied 30 minutes after bonding and maintained for 24 hours. Groups IA and IB had Transbond self etching primer (TBP) & Transbond XT adhesive (3M Unitek), groups IIA and IIB had Transbond self etching primer & Orthofix adhesive (Anabond), groups IIIA and IIIB had Transbond self etching primer & Enlight adhesive (Ormco) and groups IVA and IVB had Transbond self etching primer & Light Bond (Reliance Orthodontics). SBS testing was performed by using a universal testing machine (Instron Corporation, Canton, Mass). The results of SBS testing for all adhesives were analyzed by analysis of variance and unpaired Student’s t test to compare the effect of force on the SBS of each adhesive. Results: TBP and Transbond XT had the highest values (without force; 9.855± 2.4 MPa, with force 9.548 ± 1.596 MPa) and TBP and Enlight had the lowest (without 8.215 ± 1.851 MPa; with force, 6.818 ± 1.742 MPa). Conclusions: for all studied composites, orthodontic force up to 120gm can be applied within the first hour after bonding with no deleterious effect on bond strength.