Evaluation of shear strength of brackets with different dental composites and enamel roughness

The objective of this study was to evaluate the enamel roughness and shear bond strength (SBS) of dental composite after removal of metal brackets bonded with different materials (Transbond XT, Filtek Z100, Venus Diamond and Filtek P90). Cleaning and etching were performed in vitro on 60 premolars, which were then divided into four groups (n = 15). A metal bracket was bonded to each tooth using one of the four materials. The SBS test was performed in an Instron universal testing machine, using a chisel positioned at the junction interface with a speed of 1.0 mm/min. After testing the SBS, the teeth were analyzed using the Adhesive Remnant Index (ARI) with a stereomicroscope under 40× magnification. The remainder of the bonding material was removed with multilaminated carbide bur (FF 9642) and the surface roughness measured. The SBS and roughness data were statistically analyzed. The average SBS for the different groups in this study ranged from 6.13 to 12.72 MPa; Transbond XT (12.57 MPa) and Filtek Z100 (12.72 MPa) showed the highest values. There were differences between the bonding materials in IRA scores, but no statistically significant difference for roughness. All SBS values were adequate, since none were below the minimum acceptable level (6–8 MPa), however the enamel did not return to the conditions present prior to the bonding of the brackets.