Comparisons of different debonding techniques for ceramic brackets: an in vitro study. Part I. Background and methods.

Techniques for removing metal orthodontic attachments are, for the most part, not as effective with ceramic brackets because the properties of ceramic brackets differ greatly from those of the conventional metal orthodontic brackets. Currently available ceramic brackets are composed of aluminum oxide crystals in either a polycrystalline or monocrystalline form that has a low fracture toughness compared with that of stainless steel. Metal brackets will deform 20% under stress before fracturing, whereas ceramic brackets will deform less than 1% before failing. The purpose of this study was (1) to evaluate the debonding characteristics of three different types of ceramic brackets when removed by techniques recommended by the manufacturers; (2) to evaluate and compare the conventional, ultrasonic, and electrothermal bracket-removal techniques, and (3) to evaluate and compare the mean enamel loss from removal by high-speed bur, by slow-speed bur, and by the ultrasonic method. In the first phase of the investigation, 140 teeth (70 maxillary central incisors and 70 third molars) were bonded with one of three types of ceramic brackets. Three different debonding methods were tested--(1) the conventional method recommended by the manufacturer (either pliers or wrench), (2) an ultrasonic method that employed specially designed tips, and (3) an electrothermal method involving an apparatus that transmits heat to the bracket. In each of the test groups, five variables were evaluated during and after bracket removal: (1) the incidence of bracket failure, (2) the amount of adhesive remaining after bracket removal, (3) the site of bond failure, (4) the debonding time for each technique, and (5) enamel damage resulting from bracket removal.(ABSTRACT TRUNCATED AT 250 WORDS)