Abstract
The purpose of this in vitro study was to analyze and identify a methodology for the improvement of the shear bond strength of orthodontic brackets bonded with two orthodontic adhesive systems considered to be widely used, Transbond Plus Color Change with Transbond Plus Self-Etching Primer and Fuji Ortho LC with orthophosphoric acid under various enamel conditions: dry, moistened with water and moistened with saliva. The sample size included a group of 120 freshly extracted premolars distributed into six study groups, each one of 20 teeth. A universal testing machine was used to detach the brackets. We determined and compared the strength of the two studied adhesive systems used in different enamel surface conditions. The mean shear bond strength values in groups 1 (TPCC, TSEP, dry), 2 (TPCC, TSEP, water), 3 (TPCC, TSEP, saliva), 4 (Fuji Ortho LC, etched, dry enamel), 5 (Fuji Ortho LC, etched enamel, water) and 6 (Fuji Ortho LC, etched enamel, saliva) were 15.86, 12.31, 13.04, 15.27, 14.14 and 13.11 MPa, respectively. ANOVA test and Student’s t-test showed significant differences between groups. While clinically acceptable shear bond strengths were obtained for all six studied groups, a particular outcome that to the authors’ knowledge has not been documented elsewhere has been obtained: in case of water contamination, it is preferable to use Fuji Ortho LC instead of Transbond Plus.
Highlights
The highest bond strength was found for the group in which we used TPCC and TSEP on dry enamel, and the lowest bond strength was found for the same adhesive system on the enamel moistened with saliva
Their study demonstrated that saliva prevents micromechanical bonding between Fuji Ortho LC and tooth enamel to a great extent in the etched groups because of deposition of salivary constituents [18]; this must be the reason why we found the lowest adhesion in the group where the contamination after etching was done with saliva
We found no significant differences between the two bonding systems on dry enamel and enamel moistened with saliva
Summary
The possibility of bonding brackets was an important step in fixed orthodontics, resulting in the shortening of working time for the orthodontist, better hygiene and fewer dental and periodontal pathological conditions after wearing the appliances, better aesthetics and the elimination of the working phase in which the interdental spaces were closed after detaching the bands [1].The bond strength between the brackets and the tooth enamel is an extremely important issue in performing the mechanics of orthodontic treatment; the brackets’ detachments cause a series of inconveniences, the reattachment being a difficult, unpleasant maneuver, besides the fact that the detachment of the brackets can cause delays of the treatment results and mechanical injuries of the neighboring soft tissues of the oral cavity [1,2].From a chemical point of view, adhesion is the gluing of two materials that can be different by means of a chemical compound called adhesive or bonding. The bond strength between the brackets and the tooth enamel is an extremely important issue in performing the mechanics of orthodontic treatment; the brackets’ detachments cause a series of inconveniences, the reattachment being a difficult, unpleasant maneuver, besides the fact that the detachment of the brackets can cause delays of the treatment results and mechanical injuries of the neighboring soft tissues of the oral cavity [1,2]. The difference from physical adhesion is that chemical groups which appear on both surfaces can form an intramolecular or intermolecular chemical bond. Chemical adhesion involves a chemoabsorption process in which the adhesive molecules attached by adsorption to the surface of the material can react with its active groups by forming chemical bonds [3]. The purpose of adhesion is to join the enamel surface with another substrate, represented by the materials used for bonding the brackets. Its hardness varies depending on the dental area in which the tooth is positioned; in areas with intense functional stress, it can reach
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