Tensile Strength, Hardness and Fluoride Release of a Newly Developed Orthodontic Bracket Adhesive

Abstract

Previous studies have investigated materials specifically developed for use as orthodontic cements. Composite resins have shown greater bond strength and faster setting time compared to glass ionomer cements. However, glass ionomer adhesives have significantly greater fluoride release. The purpose of this study was to evaluate the tensile bond strength, hardness and fluoride release of Photac-Bond™ (PB), a newly developed capsulated, light-cured glass ionomer resin. A composite resin, TransBond™ (TB), and a glass ionomer cement, Ketac-Cem™ (KC), were used as controls. Each was used to bond 30 orthodontic brackets to bovine tooth samples. Tensile debonding using an lnstronTM test machine was performed after all samples were thermocycled (using 5°C and 45°C water baths) and stored for 14 days (37°C, 100 percent humidity). Discs made of the adhesives were also tested for fluoride release and Knoop hardness. TB was shown to have significantly greater tensile bond strength (p<0.05) compared to PB and KC. Adhesive: Photac-Bond™ (PB); Mean-Tensile Bond Strength (MPa): 2.22; Standard Deviation: 0.51; Adhesive: Ketac-Cem™ (KC); Mean-Tensile Bond Strength (MPa): 2.08; Standard Deviation: 0.45; Adhesive: Adhesive: TransBond™ (TB): 5.56; Mean-Tensile Bond Strength (MPa): 5.56; Standard Deviation: 0.79; No significant difference in tensile bond strength was found between PB and KC. PB fluoride release was much greater than that of TB and KC. The high fluoride release rate indicates that PB is suitable for use in patients at risk of enamel decalcification. Analysis suggests that PB developed a significantly lower hardness value than the controls. These results suggest that PB should be used to bond teeth where bracket loading is expected to be low and danger of enamel decalcification is high.