title: Acid resistance of erbium-doped yttrium aluminum garnet laser-treated and phosphoric acid-etched enamels.
abstract: OBJECTIVE
  To compare the effects of erbium-doped yttrium aluminum garnet (Er:YAG) laser ablation and of phosphoric acid etching on the in vitro acid resistance of bovine enamel.
  
  
  METHODS
  Teeth were polished to make the surface flat. The polished enamel was either etched with 37% phosphoric acid for 30 seconds or ablated with a single 33 J/cm2 pulse from an Er:YAG laser. The control specimens were free from acid etching and laser ablation. Changes in crystal structure, dissolved mineral (calcium [Ca] and phosphorus [P]) contents, and calcium distribution in the enamel subsurface after a pH-cycling process were evaluated.
  
  
  RESULTS
  After laser treatment, poor crystal structures improved without forming any new phases, such as tricalcium phosphates. Among the tested enamels, dissolved mineral contents were significantly different (P < .05). Er:YAG laser-treated enamels had the lowest mineral dissolution (Ca, 13.78 ppm; P, 6.33 ppm), whereas phosphoric acid-etched enamels had the highest (Ca, 15.90 ppm; P, 7.33 ppm). The reduction rate and reduced depth of calcium content along the subsurface were lowest in Er:YAG laser-treated enamels.
  
  
  CONCLUSIONS
  The Er:YAG laser-treated enamels are more acid resistant to acid attack than phosphoric acid-etched enamels.
authors.affiliation: Department of Orthodontics, College of Dentistry, Kyungpook National University, Daegu, Korea.
authors.forename: Jung-Ho
authors.initials: JH
authors.lastname: Kim
authors.forename: Oh-Won
authors.initials: OW
authors.lastname: Kwon
authors.forename: Hyung-Il
authors.initials: HI
authors.lastname: Kim
authors.forename: Yong Hoon
authors.initials: YH
authors.lastname: Kwon
mesh_terms: D000818:Animals; D002118:Calcium / Q000032:analysis; D002417:Cattle; D018360:Crystallography, X-Ray; D003743:Dental Enamel / Q000737:chemistry / Q000187:drug effects*; D045662:Dental Etching / Q000379:methods*; D004164:Diphosphonates / Q000494:pharmacology; D004577:Electron Probe Microanalysis; D004871:Erbium; D006863:Hydrogen-Ion Concentration; D019344:Lactic Acid / Q000494:pharmacology; D007834:Lasers; D010756:Phosphoric Acids; D010758:Phosphorus / Q000032:analysis
chemical_list: D004164:Diphosphonates; D010756:Phosphoric Acids; D010758:Phosphorus; D019344:Lactic Acid; C027474:methylene diphosphonate; D004871:Erbium; C030242:phosphoric acid; D002118:Calcium