The impact of surface preparation on shear bond strength of metallic orthodontic brackets bonded with a resin-modified glass ionomer cement

Abstract

Aim: The aim of this study was to assess the effects of four enamel preparation techniques on shear bond strength (SBS) of brackets bonded with a resin-modified glass ionomer cement (RMGIC). Adhesive Remnant Index (ARI) and enamel surface roughness (Ra) were also investigated after cement removal. Materials and methods: One hundred and forty-four human premolars were divided into four groups (n=36 in each group) as follows: Group 1, 37% phosphoric acid (i.e. conventional); Group 2, sandblasting; Group 3, sodium hypochlorite and 37% phosphoric acid; and Group 4, sodium hypochlorite and sandblasting. Twenty-four hours after bonding, the brackets were debonded with an Instron machine using a crosshead speed of 1.0 mm/min; the ARI was evaluated by an image analyser system; the Ra was measured by profilometry; and the morphology of the tooth enamel surface was observed by scanning electron microscope evaluation. Data were submitted to ANOVA and the Kruskal-Wallis test (α=0.05). Results: Mean SBS values for Groups 1-4 were 13.86, 9.08, 17 and 9.63 MPa, respectively. Mean ARI for Groups 1-4 were 11.16, 2.06, 20.66 and 3.73%. The SBS and ARI showed statistically significant differences between the four groups (P<0.001). The Ra (μm) showed no significant differences between groups. Conclusions: Bracket bonding using RMGIC showed adequate adhesion for clinical use, and the type of enamel preparation had a significant influence.