Bond strength of indirect bonded brackets in orthodontic adhesives with different viscosities.

The aim of this study was to assess the effects of three adhesives with different viscosities and an adhesion promoter on the shear bond strength (SBS) of orthodontic brackets bonded to human premolars with an indirect bonding system (IDBS). High, medium and low viscosity IDBSs with and without application of the adhesion promoter were used. The mean SBSs of the high and low viscosity IDBSs were significantly higher than that of the medium viscosity IDBS. Application of the adhesion promoter significantly increased the SBSs. The adhesion promoter significantly increased the surface roughness and free-energy of enamel. Irrespective of application or nonapplication of the adhesion promoter, the high and low viscosity IDBSs are effective for bracket bonding. Use of the medium viscosity IDBS in combination with the adhesion promoter is recommended for obtaining a clinically acceptable SBS.