Bond strength of orthodontic brackets to polymethylmethacrylate: effect of the surface treatment and adhesive system

Objectives: To evaluate the influence of surface treatment and adhesive system on shear bond strength failure mode orthodontic brackets bonded to polymethylmethacrylate surfaces. Methods: Ninety metal (n=15) were aged discs SR Ivocron subjected three conditions (no treatment; sandblasting with 50-?m aluminum oxide; roughening a tungsten bur), using two combinations adhesives (methylmethacrylate monomer + Transbond XT Primer; Scotchbond Universal Adhesive) followed by composite XT. In control group, 15 human mandibular incisors. The specimens thermocycled, stored in distilled water (37ºC, 7 days), tested shear, an Instron universal machine. Failure was classified according remnant index stereomicroscope. data analyzed analysis variance posthoc tests (p<0.05). Results: Significant differences found between bracket different treatments (p<0.001). Sandblasting oxide superior bur roughening. did not significantly nor (p=0.8415). All experimental groups showed lower strengths than group (p=0.1566). Conclusions: Mechanical influenced bracket’s polymethylmethacrylate. most effective mechanical treatment. weakest link at acrylic-adhesive interface. Orthodontic bonding weaker enamel, regardless used.