Bond strength of various fluoride-releasing orthodontic bonding systems. Experimental study

The aim of the study was to compare the shear bond strength of a fluoride-releasing composite resin adhesive (Light Bond, Reliance) and a light-cured resin-reinforced glass ionomer cement (Fuji Ortho LC, GC America) bonded to extracted teeth under different enamel surface conditions. Forty human premolars were divided at random into 4 groups of 10 specimens. Stainless steel brackets were attached to the enamel surface by 1 of the 4 protocols: 1. Fuji Ortho LC, moist non-etched enamel; 2. Fuji Ortho LC, moist etched (37% H3PO4); 3. Light Bond, dry etched (37% H3PO4); 4. Light Bond, dry etched (Etch & Prime 3.0, Degussa). The teeth were stored in deionized water at 37 degrees C for 48 hours. Shear bond strengths was determined at a crosshead speed of 1 mm/min. The residual adhesive on the enamel surface was evaluated with the modified Adhesive Remnant Index (ARI). Analysis of variance (ANOVA) and Duncan's test were used to compare the 4 groups. Significance was predetermined at p = 0.05. Significant inter-group differences were found (p < 0.0001). The mean SBS (and SD), in MPa were: Group 1: 15.9 (4.7); Group 2: 20.3 (2.5); Group 3: 16.7 (2.6); Group 4: 11.7 (2.5). Glass ionomer cement without etching and composite with Etch & Prime showed adhesive failures at the enamel and good enamel integrity after debonding. The other specimens showed mixed or adhesive fractures at the bracket failure sites. Glass ionomer used on wet tooth surfaces without etching shows a clinically acceptable bond strength with clean separation from the enamel after debonding.