Effects of different debonding techniques on the debonding forces and failure modes of ceramic brackets in simulated clinical set-ups.
BACKGROUND
The objectives of this study were to evaluate the effects of different debonding techniques on the in-vitro mean debonding forces and failure modes of ceramic brackets bonded to enamel with clinically simulated setups.


METHODS
Three kinds of ceramic brackets (Clarity; 3M Unitek, Monrovia, Calif; Inspire and Inspire Ice; Ormco, Orange, Calif) were bonded to extracted premolars with the same bonding system. Thirty ceramic brackets, 10 of each type, were removed by hand; 60 ceramic brackets, 20 of each type, were tested on a universal testing machine with the pliers according to the manufacturers' recommendations. To simulate clinical debonding conditions, specially designed setups were used to debond the ceramic brackets. Debonding forces and failure modes were investigated. Fractographic evaluations were performed by using scanning electron microscopy.


RESULTS
Most brackets failed at the bracket-adhesive interface. Cohesive bracket fractures were noted in all 3 types of ceramic brackets (debonded by hand: 70% of Inspire, 20% of Inspire Ice, and 10% of Clarity; debonded by machine: 75% of Inspire, 30% of Inspire Ice, and 25% of Clarity). The cohesive ceramic fractures of the Clarity brackets were located at the junction between the wings and the body, and at the slot. However, for the Inspire and the Inspire Ice brackets, the cohesive ceramic fractures were located at the occlusal aspect of the base. The mean debonding forces of Inspire, Inspire Ice, and Clarity brackets were 25.72 +/- 11.98, 17.92 +/- 5.03, and 76.89 +/- 23.47 N, respectively. No enamel damage was found after the brackets were removed.


CONCLUSIONS
The results of the failure modes showed that the new designs with a ball reduction band in the Inspire Ice bracket and the vertical debonding slot in the Clarity bracket significantly reduced the risk of ceramic bracket fracture during debonding. The force required to debond the Inspire Ice bracket was significantly lower than that of the Inspire bracket.
Chen
Hsing-Yu
HY
Department of Orthodontics, School of Dentistry and Graduate Institute of Clinical Dentistry, National Taiwan University and National Taiwan University Hospital, Taipei, Taiwan.
Su
Ming-Zen
MZ
Chang
Hsin-Fu Frank
HF
Chen
Yi-Jane
YJ
Lan
Won-Hong
WH
Lin
Chun-Pin
CP
D000537:Aluminum Oxide; D001641:Bicuspid; D002516:Ceramics; D017005:Dental Debonding / Q000295:instrumentation / Q000379:methods; D003799:Dental Stress Analysis; D004868:Equipment Failure; D006801:Humans; D008855:Microscopy, Electron, Scanning; D016382:Orthodontic Appliance Design; D016910:Orthodontic Brackets; D033081:Shear Strength; D013718:Tensile Strength
D000537:Aluminum Oxide