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Bonding Metal Brackets On Tooth Surfaces

KH Breuning*,Dekkers L,Beeftink M,Schols J,Wolke J

Objectives: To test the effect of different surface preparation methods on accurate bonding of orthodontic brackets on enamel, composite, and ceramic surfaces. In addition, we evaluated differences in bonding force and the adhesive remaining between precoated and non-precoated brackets after bonding on these surfaces.
Methods: Samples of enamel, composite, and ceramic surfaces were prepared for bonding orthodontic brackets using roughening with a bur, a sandblaster, phosphoric acid solution, etching with hydrofluoric acid solution, and a porcelain activator depending on the surface tested. After surface preparation, the roughness of the surface was evaluated. Then, a primer was applied and precoated and non-precoated brackets were bonded to the surface. The bond strength was tested and the amount of remaining adhesive was evaluated.
Results: Thermo cycling of teeth did not result in differences in bond strength. There was a significant increase in bonding strength between brackets without adhesive and precoated brackets after bonding on sandblasted composite surfaces. An increased roughness of dental surfaces did not result in increased bonding strength. There was adequate bonding of metal brackets on enamel after etching with 35% phosphoric acid for 10 seconds. Enamel surfaces that were roughened with a drill or sandblaster before etching had shear bonding strengths over the recommended 8 MPa. Just roughening of the enamel surface did not lead to efficient bonding. On a composite surface, roughening with a bur led to adequate bonding; while, sandblasting did not. For ceramics, after etching with hydrofluoric acid a porcelain activator was required. A reduction in surface roughness led to an increase in bond strength. After debonding, the quantity of adhesive remaining depended on the surface properties and the surface preparation before bonding.
Clinical Significance: Bracket failure during orthodontic treatment leads to increased treatment time and costs. Bonding forces should not be too low to prevent bracket failure or too high to prevent damage to the surface from debonding. Both precoated and non-precoated bracket types can be used for adequate bonding on the tested dental surfaces.