title: Adhesive performance of precoated brackets after expiration.
abstract: OBJECTIVE
  To evaluate adhesive performance in terms of debonding forces of precoated metal and ceramic brackets 4 years after expiration.
  
  
  METHODS
  Buccal and lingual surfaces of embedded extracted maxillary premolars were etched with 34% Tooth Conditioner Gel (Dentsply Caulk, Milford, Del), rinsed, and dried. Transbond MIP (3M Unitek, Monrovia, Calif) was applied prior to placing adhesive precoated brackets (APC II Victory stainless steel and APC Plus Clarity ceramic brackets, 3M Unitek). The preexpiration brackets had 29-35 months before, and the postexpiration brackets were 45-52 months past, their expiration dates. Sample size was 17-21 per group. Debonding forces were determined by subjecting the bonded brackets to a shear force in a universal testing machine. Debonding forces were compared using two-way ANOVA. Debonded surfaces were examined under a stereomicroscope to determine failure modes, which were compared using the chi-square test.
  
  
  RESULTS
  No statistically significant difference was found in debonding forces (P  =  .8581) or failure modes (P  =  .4538) between expired and unexpired brackets. Metal brackets required statistically significantly higher debonding forces than did ceramic brackets (P  =  .0001). For both expired and unexpired brackets, failure modes were mostly cohesive in the adhesive layer for ceramic brackets, and mixed between adhesive and cohesive failure in the adhesive layer for metal brackets.
  
  
  CONCLUSIONS
  Adhesive precoated brackets did not have any reduction in enamel-adhesion properties up to 4 years after their expiration date. Extended shelf life testing for precoated dental brackets may be worth considering.
authors.affiliation: a  Resident, Department of Orthodontics, College of Dentistry, University of Tennessee Health Science Center, Memphis, TN.
authors.forename: Cayce C
authors.initials: CC
authors.lastname: Cloud
authors.affiliation: b  Associate Professor and Department Chair, Department of Orthodontics, College of Dentistry, University of Tennessee Health Science Center, Memphis, TN.
authors.forename: Terry M
authors.initials: TM
authors.lastname: Trojan
authors.affiliation: c  Private practice, Stockton, CA.
authors.forename: Sam N
authors.initials: SN
authors.lastname: Suliman
authors.affiliation: d  Associate Professor, Department of Restorative Dentistry, College of Dentistry, University of Tennessee Health Science Center, Memphis, TN.
authors.forename: Daranee
authors.initials: D
authors.lastname: Tantbirojn
authors.affiliation: e  Professor and Director of Biomaterials Research, Department of Bioscience Research, College of Dentistry, University of Tennessee Health Science Center, Memphis, TN.
authors.forename: Antheunis
authors.initials: A
authors.lastname: Versluis
mesh_terms: D000269:Adhesives; D001641:Bicuspid; D002516:Ceramics; D017005:Dental Debonding; D003743:Dental Enamel; D045662:Dental Etching; D006801:Humans; D008422:Materials Testing; D016910:Orthodontic Brackets
chemical_list: D000269:Adhesives
keywords: Adhesive; Bonding, Failure mode; Expiration date; Precoated bracket; Shelf life