title: Optimal Er:YAG laser energy for preventing enamel demineralization.
abstract: OBJECTIVE
  The purpose of this study was to identify the optimal laser energy range of Er:YAG laser irradiation for laser-induced caries prevention (LICP).
  
  
  METHODS
  Twenty-one human non-carious molars were selected. The teeth were covered with nail varnish, except two 4 mm x 1 mm windows on both the buccal and lingual surfaces. The windows were randomly assigned to groups A, B, C and D, receiving no irradiation, 100, 200 and 300 mJ irradiation, respectively. The pulse width 10 pps (pulse per second) with a 1.0 mm spot size was used. After the laser treatment, each tooth was cut into two halves longitudinally. Then a two-day pH-cycling was performed, with an 18-hour demineralization followed by a 6-hour remineralization. Sections of 120 +/- 20 microm in thickness were obtained from each window. Lesion depth was measured using polarized light microscope coupled with an image analysis software. One-way ANOVA and post-hoc Tukey tests were used for evaluation of treatment effects.
  
  
  RESULTS
  The laser treatments of 100 and 200 mJ have demonstrated significant protection of enamel demineralization (p = 0.01 and 0.001, respectively), but not the treatment with 300 mJ (p = 0.106). A smaller lesion depth was observed for the 200 mJ group (97.1 microm) than that of the 100 mJ group (105.6 microm). Compared with the control, a lesion reduction of 32.78 and 26.93% for the 200 mJ group and the 100 mJ group were obtained, respectively.
  
  
  CONCLUSIONS
  Caries prevention may be achieved by using Er:YAG laser treatment if the optimal range of laser parameters for LICP can be employed.
authors.affiliation: National Yang Ming Medical University, Taipei, Taiwan.
authors.forename: Jeng-Fen
authors.initials: JF
authors.lastname: Liu
authors.forename: Yuanyuan
authors.initials: Y
authors.lastname: Liu
authors.forename: Hsu Chin-Ying
authors.initials: HC
authors.lastname: Stephen
mesh_terms: D000535:Aluminum; D000704:Analysis of Variance; D003743:Dental Enamel / Q000528:radiation effects*; D006801:Humans; D053685:Laser Therapy; D017001:Tooth Demineralization / Q000517:prevention & control* / Q000532:radiotherapy; D015019:Yttrium
chemical_list: C503779:yttrium-aluminum-garnet; D015019:Yttrium; D000535:Aluminum