title: A comparative evaluation of CO2 and erbium-doped yttrium aluminium garnet laser therapy in the management of dentin hypersensitivity and assessment of mineral content.
abstract: OBJECTIVE
  Dentin hypersensitivity is a potential threat to oral health. Laser irradiation may provide reliable and reproducible treatment but remains controversial. The present study aimed to evaluate the effects of CO2 or erbium-doped yttrium aluminium garnet (Er:YAG) laser therapy, and to assess mineral content.
  
  
  METHODS
  Eighteen human single-rooted teeth affected with advanced periodontitis were obtained. Buccal and lingual surfaces were planed to form 36 specimens. Ethylenediaminetetraacetic acid gel (24%) was applied to remove the smear layer and simulate hypersensitive teeth. The experimental groups were: group 1, control (no irradiation); group 2, CO2 laser (repetitive pulsed mode, 2 W, 2.7 J/cm(2)); and group 3, Er:YAG laser (slight contact mode, 40 mJ/pulse and 10 Hz). To evaluate dentinal tubule occlusion, six specimens per group (2-mm thickness) were prepared and observed using scanning electron microscopy (SEM) for calculation of the occlusion percentage. To evaluate the mineral content, six specimens per group (0.6-mm thickness) were used, and then the levels of Ca, K, Mg, Na, and P were measured by inductively coupled plasma-atomic emission spectrometry. In addition, the surface temperature of the specimens during laser irradiation was analyzed by a thermograph.
  
  
  RESULTS
  The SEM photomicrographs indicated melted areas around exposed dentinal tubules and a significantly greater percentage of tubular occlusion in the CO2 and Er:YAG laser groups than the control, and in the Er:YAG group than the CO2 laser group. In addition, no significant differences were noted among the experimental groups for the mineral elements analyzed. The CO2 laser group showed an evident thermal effect compared to the Er:YAG group.
  
  
  CONCLUSIONS
  CO2 and Er:YAG laser are effective in treating dentin hypersensitivity and reducing its symptoms. However, the Er:YAG laser has a more significant effect; thus, it may constitute a useful conditioning item. Furthermore, neither CO2 nor Er:YAG lasers affected the compositional structure of the mineral content.
authors.affiliation: Department of Oral Medicine, Periodontology & Oral Diagnosis, Faculty of Oral & Dental Medicine, Fayoum University, Al-Fayoum, Egypt.
authors.forename: Mahmoud Helmy
authors.identifier: 0000-0002-4711-3219
authors.initials: MH
authors.lastname: Belal
authors.affiliation: Department of Public Health & Community Medicine, Faculty of Medicine, Tanta University, Tanta, Egypt.
authors.forename: Abdulaziz
authors.identifier: 0000-0001-8152-1227
authors.initials: A
authors.lastname: Yassin
keywords: Dentin; Hypersensitivity; Laser; Minerals