Abstract
The purpose of this study was to evaluate the shear bond strength and adhesive remnant index ARI) of orthodontic brackets following enamel conditioning with acid etching, hydroabrasion, and with both procedures. Thirty extracted human premolars were divided into three groups and received either acid etching, hydroabrasion or both procedures. Orthodontic brackets were bonded with composite resin. Shear bond strength was tested with a tensile machine, then the teeth were observed under a stereomicroscope to evaluate ARI scores. The enamel morphology after each conditioning method was evaluated with scanning electron microscope imaging. A one-way ANOVA and a Kruskal−Wallis H test were used to compare the bond strength and the ARI scores among the three groups. Hydroabrasion alone produced shear bond strength values below clinical acceptability, while the combination of acid etching and hydroabrasion produced the highest values. The ARI scores in the hydroabrasion group were significantly different from the other groups. Hydroabrasion followed by acid etching was effective in increasing the shear bond strength of orthodontic brackets. Further in vivo studies are needed to confirm the cost and benefits of this technique.
Highlights
When Buonocore in 1955 first described the use of phosphoric acid etching, it became possible to achieve a strong bond between resin composite and enamel [1]
Thirty-three upper premolars extracted for therapeutic reasons, such as periodontal problems or orthodontic treatment, were selected after being screened under 2.5X magnifying loupes for presenting an intact enamel surface and no signs of erosion or abrasion, no surface demineralization, no decay and no traumatic damage provoked by forceps during the extraction procedure
A low-viscosity resin is applied to the surface, infiltrating the micropores left in the prismatic and interprismatic enamel by the action of the etchant: the micromechanical interlocking between the roughened enamel and the low-viscosity resin is the mechanism that underlies enamel bonding [21]
Summary
When Buonocore in 1955 first described the use of phosphoric acid etching, it became possible to achieve a strong bond between resin composite and enamel [1]. Enamel etching has been the gold standard for orthodontic bracket bonding: the phosphoric acid modifies the enamel surface into a typical etching pattern, allowing the mechanical interlocking of the adhesive into the created roughness [3]. An orthodontic bonding should be strong enough to prevent accidental failure, while minimizing the damage to the enamel and being reversible, allowing the removal of the bracket without significant damage to the tooth [4]. Phosphoric acid etching provides a good bond strength, but on the other hand is considered by many authors as having an iatrogenic.
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