title: Rehardening of acid-softened enamel and prevention of enamel softening through CO2 laser irradiation.
abstract: OBJECTIVE
  The aims of the present study were to investigate whether irradiation with a CO(2) laser could prevent surface softening (i) in sound and (ii) in already softened enamel in vitro.
  
  
  METHODS
  130 human enamel samples were obtained and polished with silicon carbide papers. They were divided into 10 groups (n = 13) receiving 5 different surface treatments: laser irradiation (L), fluoride (AmF/NaF gel) application (F), laser prior to fluoride (LF), fluoride prior to laser (FL), non-treated control (C); and submitted to 2 different procedures: half of the groups was acid-softened before surface treatment and the other half after. Immersion in 1% citric acid was the acid challenge. Surface microhardness (SMH) was measured at baseline, after softening and after treatment. Additionally, fluoride uptake in the enamel was quantified. The data were statistically analysed by two-way repeated measurements ANOVA and post hoc comparisons at 5% significance level.
  
  
  RESULTS
  When softening was performed either before or after laser treatment, the L group presented at the end of the experiments SMH means that were not significantly different from baseline (p = 0.8432, p = 0.4620). Treatment after softening resulted for all laser groups in statistically significant increase in SMH means as compared to values after softening (p < 0.0001). Enamel fluoride uptake was significantly higher for combined laser-fluoride treatment than in control (p<0.0001).
  
  
  CONCLUSIONS
  Irradiation of dental enamel with a CO(2) laser at 0.3J/cm(2) (5 μs, 226 Hz) not only significantly decreased erosive mineral loss (97%) but also rehardened previously softened enamel in vitro.
authors: Department of Operative Dentistry, Periodontology and Preventive Dentistry (ZPP), RWTH Aachen University, Pauwelsstr. 30, 52074 Aachen, Germany. mestevesoliveira@ukaachen.de
authors: M
authors: M
authors: Esteves-Oliveira
authors: C
authors: C
authors: Pasaporti
authors: N
authors: N
authors: Heussen
authors: C P
authors: CP
authors: Eduardo
authors: F
authors: F
authors: Lampert
authors: C
authors: C
authors: Apel
mesh_terms: D002327:Cariostatic Agents / Q000493:pharmacokinetics / Q000627:therapeutic use; D019343:Citric Acid / Q000009:adverse effects; D003743:Dental Enamel / Q000187:drug effects / Q000528:radiation effects*; D003959:Diamines / Q000493:pharmacokinetics / Q000627:therapeutic use; D005459:Fluorides / Q000493:pharmacokinetics / Q000627:therapeutic use; D006244:Hardness; D006801:Humans; D006863:Hydrogen-Ion Concentration; D054020:Lasers, Gas / Q000627:therapeutic use*; D028022:Low-Level Light Therapy / Q000379:methods; D012464:Saliva, Artificial / Q000737:chemistry; D017001:Tooth Demineralization / Q000517:prevention & control / Q000532:radiotherapy*; D014077:Tooth Erosion / Q000517:prevention & control / Q000532:radiotherapy; D014089:Tooth Remineralization / Q000379:methods*
chemical_list: D002327:Cariostatic Agents; D003959:Diamines; D012464:Saliva, Artificial; D019343:Citric Acid; C495399:Olaflur; D005459:Fluorides