The Influence of Work of Fracture on Six Orthodontic Bonding Systems

Introduction: Bonding is the primary method of attaching brackets to teeth in modem orthodontics. Thus, many studies have focused on the maximum shear bond strength values of orthodontic adhesives. In contrast, very little research has been performed considering the work of fracture of orthodontic bonding systems. Work of Fracture is defined as the area under the curve of a stress-strain graph. Previous shear bond strength studies measured the force necessary to produce bond failure. The purpose of this study was to measure the maximum shear force and displacement of six bonding systems and to calculate the work of fracture. Materials and Methods: One hundred and eighty bovine teeth were collected. Half of the teeth were direct bonded with titanium brackets and the other half with stainless steel brackets. Each bracket was divided into three groups of thirty and each group bonded with one of the following adhesives, Gren Gloo, Transbond XT or Glass lonomer. After bonding, the specimens were stored in distilled water at room temperature for 72 hours. The brackets were then debonded with a high-resolution tensile testing device and then assigned an Adhesive Remnant Index score. Results: Titanium and stainless steel brackets bonded with Gren Gloo and stainless steel brackets bonded with Transbond XT had the highest and statistically equal shear bond strengths (p > 0.05). Titanium and stainless steel brackets bonded with Gren Gloo and stainless steel brackets bonded with Transbond XT had the greatest and statistically equal displacement (p > 0.05). The analyses of the six combinations of brackets and adhesives showed that titanium brackets bonded with Gren Gloo bad the highest Work of Fracture (p < 0.001). These tests showed that the brackets bonded with Fuji Ortho LC Glass lonomer, independent of bracket type, had a significantly lower Adhesive Remnant Index than those brackets bonded with Green[sic] Gloo and Transbond XT (p < 0.001). Conclusions: Evaluating a bonding