title: Shear bond strength and residual adhesive after orthodontic bracket debonding.
abstract: OBJECTIVE
  To compare the shear bond strength and determine the area of residual adhesive on teeth after the debonding of brackets bonded with two types of orthodontic adhesives. These were a resin-modified glass ionomer cement (RMGIC; Fuji ORTHO LC, GC Corporation, Tokyo, Japan) and a resin applied as a precoated bracket (APC bracket, 3M Unitek GmbH, Seefeld, Germany).
  
  
  METHODS
  A total of 60 premolar teeth were randomly divided into two groups, and brackets were bonded according to the manufacturers' instructions. In group 1, the teeth were conditioned using 10% polyacrylic acid, and the brackets were bonded using Fuji Ortho LC in wet condition. In group 2, the teeth were etched using 37% phosphoric acid, and the APC brackets were bonded. Bond strength was measured using a testing instrument (2000S, Lloyds Instruments, Fareham, England) at a crosshead speed of 1 mm/min, and the residual adhesive was quantified using a three-dimensional laser scanning instrument.
  
  
  RESULTS
  The Mann-Whitney test showed that the median bond strength of group 1 was significantly lower than that of group 2 (P < .001). A Pearson chi-square test of the Adhesive Remnant Index (ARI) revealed a significant difference among the groups tested. All the adhesives in group 1 failed at the enamel/adhesive interface (100%), whereas group 2 exhibited cohesive failure of the adhesive (90%).
  
  
  CONCLUSIONS
  The bond strength values obtained with the RMGIC were above the minimum values suggested in the literature to achieve a clinically effective adhesion in orthodontics.
authors.affiliation: Restorative Department, School of Dentistry, Queen's University, Belfast, Northern Ireland, UK. alshamsiamna@hotmail.com
authors.forename: A
authors.initials: A
authors.lastname: Al Shamsi
authors.forename: J L
authors.initials: JL
authors.lastname: Cunningham
authors.forename: P J
authors.initials: PJ
authors.lastname: Lamey
authors.forename: E
authors.initials: E
authors.lastname: Lynch
mesh_terms: D000134:Acid Etching, Dental; D000180:Acrylic Resins / Q000737:chemistry; D000268:Adhesiveness; D000538:Aluminum Silicates / Q000737:chemistry; D003722:Dental Alloys / Q000737:chemistry; D001840:Dental Bonding; D017005:Dental Debonding; D005899:Glass Ionomer Cements / Q000737:chemistry; D006801:Humans; D021621:Imaging, Three-Dimensional; D007834:Lasers; D008422:Materials Testing; D016910:Orthodontic Brackets; D010756:Phosphoric Acids / Q000737:chemistry; D019279:Resin Cements / Q000737:chemistry*; D033081:Shear Strength; D013499:Surface Properties
chemical_list: D000180:Acrylic Resins; C474376:Adhesive Precoated Cement; D000538:Aluminum Silicates; D003722:Dental Alloys; C095451:Fuji Ortho LC; D005899:Glass Ionomer Cements; D010756:Phosphoric Acids; D019279:Resin Cements; C006903:carbopol 940; C030242:phosphoric acid