title: Effects of CO(2) laser debonding of a ceramic bracket on the mechanical properties of enamel.
abstract: OBJECTIVE
  To investigate the effects of CO(2) laser debonding of a ceramic bracket on the mechanical properties of tooth enamel.
  
  
  METHODS
  Fifty-three human premolars were used in this study. The temperature changes of cross-sectioned specimens during laser irradiation were monitored with an infrared thermographic microscope system. Different laser output settings (3, 4, 5, and 6 W) were compared. The shear bond strength of brackets after laser irradiation was measured for specimens bonded with a conventional etch and rinse adhesive or with a self-etching adhesive, and the adhesive remnant index score was calculated. The hardness and elastic modulus of cross-sectioned enamel after laser irradiation were investigated by the nanoindentation test. Data were compared by one-way and two-way analysis of variance, followed by the Scheffé test.
  
  
  RESULTS
  The temperature of enamel increased by about 200 degrees C under CO(2) laser irradiation with a relatively high output (5 and 6 W), and a temperature increase of about 100 degrees C to 150 degrees C was seen under laser irradiation with a low output (3 and 4 W). The bracket shear bond strength decreased under all laser irradiation conditions. The hardness and elastic modulus of enamel were not affected by CO(2) laser debonding.
  
  
  CONCLUSIONS
  CO(2) laser debonding may not cause iatrogenic damage to enamel.
authors.affiliation: Department of Oral Growth and Development, Health Sciences University of Hokkaido, Hokkaido, Japan. r.veberiene@gmail.com
authors.forename: Masahiro
authors.initials: M
authors.lastname: Iijima
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Yasuda
authors.forename: Takeshi
authors.initials: T
authors.lastname: Muguruma
authors.forename: Itaru
authors.initials: I
authors.lastname: Mizoguchi
mesh_terms: D000704:Analysis of Variance; D017005:Dental Debonding / Q000009:adverse effects / Q000295:instrumentation* / Q000379:methods; D003743:Dental Enamel / Q000293:injuries / Q000502:physiology*; D003799:Dental Stress Analysis; D055119:Elastic Modulus; D006244:Hardness; D006358:Hot Temperature / Q000009:adverse effects; D006801:Humans; D054020:Lasers, Gas / Q000009:adverse effects*; D016910:Orthodontic Brackets; D033081:Shear Strength; D018709:Statistics, Nonparametric; D013817:Thermography / Q000379:methods