Effect of water, saliva and blood contamination on bonding of metal brackets with a 4-META/MMA/TBB resin to etched enamel

Purpose: To investigate the influence of contamination by water, human sali va, and blood on the bonding of metal brackets with a 4-META/MMA/TBB resin to etched enamel. Materials & Methods: For compressive shear bond strength measurements, the surfaces of bovine enamel were prepared either by etching with 37% phosphoric acid solution for 10, 30, or 60 s and then dried with oil-free compressed air for 10 s, or by contaminating with water, human sal iva, and blood. Brackets were applied with Super Bond under loads of 200, 4 00, or 600 g. The bonded samples were immersed in water for 1 d or thermocy cled for 500 cycles, and the mean shear bond strengths were compared using two-way ANOVA and Scheffe's multiple comparisons test at P=0.05. Results: T he bond strengths to enamel etched for 60 s were independent of the variabl e load, regardless of the type of contamination. A short etching duration p rovided higher bond strengths than extended etching of samples contaminated with saliva and blood. The bond strengths to enamel etched for 10 s after thermal stress and immersion in water were from 11.4 to 30.4 MPa. The sampl es contaminated by saliva showed the lowest bond strength, and thermal stre ss did not reduce the bond strengths.