Background Bond strength of orthodontic composite is strongly influenced by molecular and structural mechanisms. Aim of this in vitro study was to compare the bond strength of light-cure orthodontic composites by measuring debonding forces and evaluating locations of bond failure. Investigations on chemical compositions clarified adhesive behaviors and abilities, exploring effects of ageing processes in this junction materials.
Methods Sixteen human premolars were selected to realize specimen of enamel sections, randomly divided into three groups, which was assigned a different orthodontic adhesive system and then underwent to Shear Bond Strength test.
Twenty-seven human premolars were selected to produce samples, each of which was coupled at a metallic bracket, bonded to the enamel tooth surface with one of the three orthodontic adhesive systems, to quantify, at FE-SEM magnifications, after debonding, the residual material on enamel and bracket base surfaces.
Eight test discs of each orthodontic composite, were divided into three randomly groups to study accelerated aging effects in human saliva and sugary drink. Chemical compositions of composite materials were investigated, before and after ageing procedures, by Raman Spectroscopy analysis.
Conclusion The orthodontic adhesive systems showed rather similar strength of adhesion to enamel. The breakage of adhesive-adherent bond occurs in TXT at enamel-adhesive interface while in Bisco and Leone composites at the adhesive-bracket interface. Accelerated in vitro aging demonstrated a good physical-chemical stability for all orthodontic composites, Bisco only, was weakly contaminated with respect to the other two materials.