Physical and chemical mechanisms involved in adhesion of orthodontic bonding composites: in vitro evaluations

Abstract

Background Bond strength of orthodontic composite is strongly influenced by molecular and structural mechanisms. Aim of this in vitro study was to compare 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 Twelve enamel discs, from human premolars, were randomly coupled to one orthodontic adhesive system (Transbond XT™ 3 M UNITEK, USA, Light-Cure Orthodontic Paste, LEONE, Italy and Bisco Ortho Bracket Paste LC, BISCO, Illinois) and underwent to Shear Bond Strength test. Metallic brackets were bonded to twenty-seven human premolar, with one of the adhesive systems, to quantify, at FE-SEM magnifications, after debonding, the residual material on enamel and bracket base surfaces. Raman Spectroscopy analysis was performed on eight discs of each composites to investigate on chemical compositions, before and after accelerated aging procedures in human saliva and sugary drink. Results Orthodontic adhesive systems showed similar strength of adhesion to enamel. The breakage of adhesive-adherent bond occurs in TXT at enamel-adhesive interface while in Bisco and Leone at adhesive-bracket interface. Accelerated in vitro aging demonstrated good physical–chemical stability for all composites, Bisco only, was weakly contaminated with respect to the other materials. Conclusion A similar, clinically adequate and acceptable bond strength to enamel for debonding maneuvers was recorded in all orthodontic adhesive systems under examination. No significant chemical alterations are recorded, even in highly critical situations, not altering the initial mechanical properties of materials.

Comparative Study of the Shear Bond Strengths and Bracket Failure Rates of Two Orthodontic Adhesive Systems

“…Contrary to previous studies [18,20,34] (most of which did not compare shear bond strength and failure rate) in which teeth used to determine shear bond strength in the laboratory were extracted from any available participant, in the present study, the teeth used for the in vitro shear bond strength determination were from the same participants enrolled into the clinic study. This was to ensure that teeth with similar morphology and chemistry per participant were used in the comparison of bond strength and failure rate since the success of adhesion has also been linked to the characteristics of the interfacing surfaces [35]. Teeth surfaces with sub-clinical erosion from cola-based drinks have been reported as having significantly reduced bond strength [36].…”

Aspects and Principles of Material Connections in Restorative Dentistry—A Comprehensive Review

“…Optimum values are therefore around 6–8 MPa. At the other end of the scale, there is the adhesive cementation of bridge crowns or implantological work, where forces of 20–30 MPa are required [ 8 ].…”

“…Their propagation is strongly influenced by the molecular weight of the reactants and growing polymer network, and reactive and structural characteristics of the material being cured. These can be determined by the shape and volume fraction of the filler, viscosity of the resins, quantity of double bonds and mismatch of refractive index between resin and fillers [ 8 ].…”

Combined Effects of Different Bracket Bonding Adhesives and Different Resin Removal Methods on Enamel Discoloration: A Preliminary Study

“…Therefore, the availability of an orthodontic bonding agent with minimal discoloration and the ability to remove its residue by following a simple protocol would be highly desirable. The literature on the effect of orthodontic bracket bonding/removal on enamel discoloration is scarce and controversial [ 18 , 19 ]. Moreover, no study has simultaneously examined both factors affecting the colorability of teeth after bracket debonding (bonding factors and resin removal factors): all of the few previous studies had either investigated bonding factors or resin removal factors but not both.…”