title: FTIR and SEM analysis of CO2 laser irradiated human enamel.
abstract: OBJECTIVE
  Considering the enamel chemical structure, especially carbonate band, which has a major role in the caries prevention, the objective of the present study was to assess the chemical alterations on the enamel irradiated with CO(2) laser by means of FTIR spectroscopy and SEM analysis.
  
  
  METHODS
  The enamel surfaces were analysed on a spectrometer for acquisition of the absorption spectrum relative to the chemical composition of the control sample. The irradiation was conducted with a 10.6-μm CO(2) laser (0.55W, 660W/cm(2)). The carbonate absorption band at 1600-1291cm(-1) as well as the water absorption band at 3793-2652cm(-1) was measured in each sample after the irradiation. The water band was measured again 24-h after the irradiation. The band area of each chemical compound was delimited, the background was subtracted, and the area under each band was integrated. Each area was normalized by the phosphate band (1190-702cm(-1)).
  
  
  RESULTS
  There was a statistically significant decrease (p<0.05) in the water content after irradiation (control: 0.184±0.04; irradiated: 0.078±0.026), which increased again after rehydration (0.145±0.038). The carbonate/phosphate ratio was measured initially (0.112±0.029) and its reduction after irradiation indicated the carbonate loss (0.088±0.014) (p<0.05).
  
  
  CONCLUSIONS
  The 10.6-μm CO(2) laser irradiation diminishes the carbonate and water contents in the enamel after irradiation.
authors.affiliation: Departamento de Clínica Infantil, Odontologia Preventiva e Social, Faculdade de Odontologia de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brazil. alessandra@forp.usp.br
authors.forename: Alessandra Marques
authors.initials: AM
authors.lastname: Corrêa-Afonso
authors.forename: Luciano
authors.initials: L
authors.lastname: Bachmann
authors.forename: Cíntia Guimarães de
authors.initials: CG
authors.lastname: Almeida
authors.forename: Silmara Aparecida Milori
authors.initials: SA
authors.lastname: Corona
authors.forename: Maria Cristina
authors.initials: MC
authors.lastname: Borsatto
mesh_terms: D001834:Body Water / Q000737:chemistry; D002254:Carbonates / Q000032:analysis; D003743:Dental Enamel / Q000737:chemistry / Q000528:radiation effects* / Q000648:ultrastructure; D006801:Humans; D054020:Lasers, Gas; D008855:Microscopy, Electron, Scanning; D008964:Molar, Third; D010710:Phosphates / Q000032:analysis; D011829:Radiation Dosage; D017550:Spectroscopy, Fourier Transform Infrared; D013997:Time Factors; D019228:Tooth Crown / Q000737:chemistry / Q000528:radiation effects / Q000648:ultrastructure
chemical_list: D002254:Carbonates; D010710:Phosphates