Shear bond strength and residual adhesive after orthodontic bracket debonding.
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.
Al Shamsi
A
A
Restorative Department, School of Dentistry, Queen's University, Belfast, Northern Ireland, UK. alshamsiamna@hotmail.com
Cunningham
J L
JL
Lamey
P J
PJ
Lynch
E
E
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
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