title: Effect of carbon dioxide laser irradiation on enamel surface microhardness around orthodontic brackets.
abstract: BACKGROUND
  In this study, we aimed to determine the effect of carbon dioxide laser irradiation on enamel surface microhardness.
  
  
  METHODS
  In this single-blind interventional clinical trial, 16 patients needing at least 2 premolars extracted for orthodontic purposes participated. In each subject, 1 premolar was treated with the carbon dioxide laser (beam diameter, 0.2 mm; power, 0.7 W); the other was exposed to a visible guiding light as the control. A t-loop was ligated to the bonded brackets to increase caries risk. After at least 2 months, the teeth were extracted, and the surface microhardness was measured. Scanning electron microscope evaluation was performed on 1 sample from each group. Normal distribution of the data was assessed by the Kolmogorov-Smirnov and Shapiro-Wilks tests. Mean microhardness values of the 2 groups were compared using paired t tests.
  
  
  RESULTS
  The data had normal distributions. Means and standard deviations of the microhardness in the laser-treated and control groups were 301.81 ± 94.29 and 183.9 ± 72.08 Vickers hardness numbers, respectively; this was different significantly (P <0.001). Scanning electron microscopy showed the enamel surface melting in the laser-treated specimens.
  
  
  CONCLUSIONS
  Carbon dioxide laser treatment results in higher enamel surface microhardness around orthodontic brackets. Patients at high risk of caries might benefit from this intervention. Exact control of the laser irradiation parameters is recommended.
authors.affiliation: Associate professor, Department of Orthodontics, Dental Research Center, Dental Faculty, Hamadan University of Medical Sciences, Hamadan, Iran.
authors.forename: Amirfarhang
authors.initials: A
authors.lastname: Miresmaeili
authors.affiliation: Associate professor, Department of Orthodontics, Dental Research Center, Dental Faculty, Hamadan University of Medical Sciences, Hamadan, Iran.
authors.forename: Nasrin
authors.initials: N
authors.lastname: Farhadian
authors.affiliation: Associate professor, Department of Operative Dentistry, Dental Research Center, Hamadan University of Medical Sciences, Hamadan, Iran. Electronic address: Loghmanrs@yahoo.com.
authors.forename: Loghman
authors.initials: L
authors.lastname: Rezaei-soufi
authors.affiliation: Clinical instructor, Department of Pediatric Dentistry, Dental Faculty, Hamadan University of Medical Sciences, Hamadan, Iran.
authors.forename: Mehdi
authors.initials: M
authors.lastname: Saharkhizan
authors.affiliation: Private practice, Hamadan, Iran.
authors.forename: Meysam
authors.initials: M
authors.lastname: Veisi
mesh_terms: D000134:Acid Etching, Dental / Q000379:methods; D000293:Adolescent; D001641:Bicuspid / Q000528:radiation effects / Q000648:ultrastructure; D002327:Cariostatic Agents / Q000627:therapeutic use; D002648:Child; D004245:DMF Index; D003722:Dental Alloys; D003733:Dental Caries Susceptibility / Q000528:radiation effects; D003743:Dental Enamel / Q000528:radiation effects* / Q000648:ultrastructure; D005260:Female; D005459:Fluorides / Q000627:therapeutic use; D006244:Hardness / Q000528:radiation effects*; D006801:Humans; D054020:Lasers, Gas; D008297:Male; D008855:Microscopy, Electron, Scanning; D016910:Orthodontic Brackets; D010756:Phosphoric Acids; D019279:Resin Cements; D016037:Single-Blind Method; D013193:Stainless Steel; D014099:Toothbrushing / Q000295:instrumentation / Q000379:methods; D055815:Young Adult
chemical_list: D002327:Cariostatic Agents; D003722:Dental Alloys; D010756:Phosphoric Acids; D019279:Resin Cements; C477790:Transbond XT; D013193:Stainless Steel; C030242:phosphoric acid; D005459:Fluorides