title: Impact of combined CO2laser irradiation and fluoride on enamel and dentin biofilm-induced mineral loss.
abstract: OBJECTIVE
  The caries-protective effects of CO2laser irradiation on dental enamel have been demonstrated using chemical demineralization models. We compared the effect of CO2laser irradiation, sodium fluoride, or both on biofilm-induced mineral loss (∆Z) and Streptococcus mutans adhesion to enamel and dentin in vitro.
  
  
  METHODS
  Ground, polished bovine enamel, and dentin samples were allocated to four groups (n = 12/group): no treatment (C); single 22,600-ppm fluoride (F) varnish (5 % NaF) application; single CO2laser treatment (L) with short pulses (5 μs/λ = 10.6 μm); and laser and subsequent fluoride treatment (LF). Samples were sterilized and submitted to an automated mono-species S. mutans biofilm model. Brain heart infusion plus 5 % sucrose medium was provided eight times daily, followed by rinses with artificial saliva. After 10 days, bacterial numbers in biofilms were enumerated as colony-forming units/ml (CFU/ml) (n = 7/group). ∆Z was assessed using transversal microradiography (n = 12/group). Univariate ANOVA with post hoc Tukey honestly-significant-difference test was used for statistical analysis.
  
  
  RESULTS
  Bacterial numbers were significantly higher on dentin than enamel (p < 0.01/ANOVA). On dentin, LF yielded significantly lower CFUs than other groups (p = 0.03/Tukey), while no differences between groups were found for enamel. The lowest ∆Z in enamel was observed for L (mean/SD 2036/1353 vol%×μm), which was not only significantly lower than C (9642/2452 vol%×μm) and F (7713/1489 vol%×μm) (p < 0.05) but also not significantly different from LF (3135/2628 vol%×μm) (p > 0.05). In dentin, only LF (163/227) significantly reduced ∆Z (p < 0.05).
  
  
  CONCLUSIONS
  CO2laser irradiation did not increase adhesion of S. mutans in vitro. Laser treatment alone protected enamel against biofilm-induced demineralization, while a combined laser-fluoride application was required to protect dentin.
authors.affiliation: Department of Operative Dentistry, Periodontology and Preventive Dentistry (ZPP), RWTH Aachen University, Pauwelsstr. 30, 52074, Aachen, Germany. mestevesoliveira@ukaachen.de.
authors.forename: Marcella
authors.initials: M
authors.lastname: Esteves-Oliveira
authors.affiliation: Clinic for Conservative Dentistry and Periodontology, School of Dental Medicine, Christian-Albrechts-Universität zu Kiel, Arnold-Heller-Straße 3, 24105, Kiel, Germany.
authors.forename: Karim Fawzy
authors.initials: KF
authors.lastname: El-Sayed
authors.affiliation: Clinic for Conservative Dentistry and Periodontology, School of Dental Medicine, Christian-Albrechts-Universität zu Kiel, Arnold-Heller-Straße 3, 24105, Kiel, Germany.
authors.forename: Christof
authors.initials: C
authors.lastname: Dörfer
authors.affiliation: Department of Operative and Preventive Dentistry, Charité - Universitätsmedizin Berlin, Aßmannshauser Str. 4-6, 14197, Berlin,, Germany.
authors.forename: Falk
authors.initials: F
authors.lastname: Schwendicke
mesh_terms: D000818:Animals; D001422:Bacterial Adhesion / Q000187:drug effects / Q000528:radiation effects; D018441:Biofilms / Q000187:drug effects* / Q000528:radiation effects*; D002417:Cattle; D003743:Dental Enamel / Q000187:drug effects* / Q000528:radiation effects*; D003804:Dentin / Q000187:drug effects* / Q000528:radiation effects*; D005460:Fluorides, Topical / Q000494:pharmacology*; D066298:In Vitro Techniques; D054020:Lasers, Gas; D008852:Microradiography; D008855:Microscopy, Electron, Scanning; D011897:Random Allocation; D012969:Sodium Fluoride; D013295:Streptococcus mutans / Q000187:drug effects / Q000528:radiation effects; D013499:Surface Properties; D017001:Tooth Demineralization / Q000517:prevention & control*
chemical_list: D005460:Fluorides, Topical; C023807:sodium fluoride topical preparation; D012969:Sodium Fluoride
keywords: Biofilm(s); CO2 laser; Caries model; Dental plaque/plaque biofilms; Microbial ecology; Streptococcus mutans