Effect of loading mode on bond strength of orthodontic brackets bonded with 2 systems.
BACKGROUND
A new orthodontic bracket bonding method or material invariably spawns bond strength studies examining the efficacy of the innovation. The primary purpose of this project was to ascertain whether the mode of in-vitro bracket debonding used in a study affects the measured bond strength. The secondary aim was to compare the bond strengths of 2 different bonding systems.


METHODS
Flattened stainless steel orthodontic brackets were bonded to flattened bovine enamel with a resin composite bonding agent (Transbond XT, 3M Unitek, Monrovia, Calif). The enamel was prepared with traditional acid etching and priming (37% phosphoric acid gel and Transbond XT Primer, 3M Unitek) or a single-step method (Transbond Plus, 3M Unitek) that combined etching and priming. Cement thickness was kept constant, and bonding was done under controlled temperature and humidity. Brackets were debonded in shear-peel, tension, or torsion.


RESULTS
When tested in shear-peel mode, traditional etching and priming produced a stronger bond than the single-step self-etch system. When tested in tension, the traditional bond was weaker than the single-step bond, and when tested in torsion, the bond strengths were similar.


CONCLUSIONS
Bond strength can vary depending on the method of testing. Claims of clinical efficacy might not be valid.
Katona
Thomas R
TR
Indiana University School of Dentistry, and mechanical engineering, Purdue University School of Engineering and Technology, Indianapolis, Ind, USA. tkatona@iupui.edu
Long
Robert W
RW
D000134:Acid Etching, Dental / Q000379:methods; D000818:Animals; D002417:Cattle; D003188:Composite Resins / Q000737:chemistry; D003722:Dental Alloys / Q000737:chemistry; D001840:Dental Bonding / Q000379:methods*; D017005:Dental Debonding / Q000379:methods; D003743:Dental Enamel / Q000648:ultrastructure; D006813:Humidity; D008422:Materials Testing; D016910:Orthodontic Brackets; D010756:Phosphoric Acids / Q000737:chemistry; D019279:Resin Cements / Q000737:chemistry; D012399:Rotation; D033081:Shear Strength; D013193:Stainless Steel / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D013696:Temperature
D003188:Composite Resins; D003722:Dental Alloys; D010756:Phosphoric Acids; D019279:Resin Cements; C429625:Transbond Plus Self-Etching Primer; C477790:Transbond XT; D013193:Stainless Steel