title: Laser debonding of ceramic orthodontic brackets.
abstract: Laser light energy has been shown in other studies to degrade resins by thermal softening, thermal ablation, or photoablation. If this technology could be successfully applied to bracket debonding, fracturing of both bracket and enamel during debonding might be eliminated. Both polycrystalline alumina and single crystal alumina (sapphire) ceramic orthodontic brackets were bonded to the labial surfaces of lower deciduous bovine incisor teeth with the acid-etch technique as currently practiced in dentistry. Under an externally applied stress of either zero or 0.8 MPa, the brackets were debonded by irradiating the labial surfaces of the brackets with laser light at wavelengths of 248 nm, 308 nm, and 1060 nm, and at light power densities of between about 3 and 33 W/cm2. Debonding times were measured, and the surfaces created by debonding were examined with both light and scanning electron microscopy to determine the extent of bracket and enamel damage. The results showed that under the conditions of this study, no enamel or bracket damage was present in any sample. The polycrystalline brackets debonding times were about 3 seconds, 5 seconds, and 24 seconds for 248 nm, 308 nm, and 1060 nm of radiation, respectively. The debonding of polycrystalline brackets is caused by thermal softening of the bonding resin resulting from heating of the bracket. The hot bracket then slides off the tooth. All sapphire brackets debonded in less than 1 second. At sufficiently high power levels, debonding of sapphire brackets is caused by either thermal ablation or photoablation resulting from direct interaction of the light beam with the resin.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Faculty of Dentistry, University of Manitoba, Canada.
authors.forename: R M
authors.initials: RM
authors.lastname: Tocchio
authors.forename: P T
authors.initials: PT
authors.lastname: Williams
authors.forename: F J
authors.initials: FJ
authors.lastname: Mayer
authors.forename: K G
authors.initials: KG
authors.lastname: Standing
mesh_terms: D000042:Absorption; D000537:Aluminum Oxide / Q000737:chemistry; D000704:Analysis of Variance; D000818:Animals; D002417:Cattle; D002516:Ceramics; D017005:Dental Debonding / Q000295:instrumentation* / Q000379:methods; D003743:Dental Enamel / Q000528:radiation effects; D003799:Dental Stress Analysis; D004868:Equipment Failure; D007834:Lasers; D009354:Neodymium; D016910:Orthodontic Brackets; D013997:Time Factors
chemical_list: D009354:Neodymium; D000537:Aluminum Oxide