title: Interlayer formation and its effect on debonding polycrystalline alumina orthodontic brackets.
abstract: During the debonding of ceramic orthodontic brackets, there is a risk of causing fractures, cracks, or flaking of enamel or of the bracket itself. Preliminary work on the resin-enamel interface under bonded brackets with the indirect (modified Thomas) or the thermal-cured indirect bonding techniques revealed an interlayer of unfilled resin formed between the filled resin and the enamel surface. The direct bonding technique, on the other hand, showed no such layer. This study was designed to determine the effect of the interlayer on conventional debonding techniques for polycrystalline ceramic orthodontic brackets. Variables examined were bracket failure or fracture (BF), amount of remnant adhesive (ARI), and enamel damage. Brackets were bonded to 90 fresh bovine teeth. These were divided into three groups of 30 each, based on three methods of bonding, i.e., direct, indirect (modified Thomas), and an indirect technique that used a thermal-cured resin. Each bonding group was further divided into three groups of 10 each, based on the type of debonding technique used, i.e., lift off, delamination, and twisting. Brackets bonded by the indirect (modified Thomas, BF mean = 0.27, ARI mean = 0.93) and the indirect technique that used a thermal-cured resin (BF mean = 0.03, ARI mean = 0.43) resulted in an overall significantly lower failure (p < 0.01) and ARI score on debonding (p < 0.0001) compared with those bonded by the direct technique (BF mean = 1.03, ARI mean = 1.97). Specimens evaluated under the stereomicroscope revealed that the brackets bonded with the indirect techniques debonded at the filled-unfilled resin interface or within the interlayer of unfilled resin.(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D000537:Aluminum Oxide; D000704:Analysis of Variance; D000818:Animals; D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D002417:Cattle; D002516:Ceramics; D001840:Dental Bonding / Q000379:methods*; D003738:Dental Cements / Q000737:chemistry; D017005:Dental Debonding; D003743:Dental Enamel / Q000648:ultrastructure; D004868:Equipment Failure; D016910:Orthodontic Brackets; D018709:Statistics, Nonparametric; D013499:Surface Properties
chemical_list: D003738:Dental Cements; D017438:Bisphenol A-Glycidyl Methacrylate; D000537:Aluminum Oxide