title: Structural modifications induced in dentin by femtosecond laser.
abstract: The structural and chemical modifications induced in dentin by ultrafast laser ablation were studied. The laser experiments were performed with a Yb:KYW chirped-pulse-regenerative amplification laser system (560-fs pulse duration, 1030-nm radiation wavelength), fluences in the range 2 to 14 ?? J / cm 2 , 1-kHz pulse repetition rate, and 5 - mm / s scanning speed. The ablation surfaces were characterized by scanning electron microscopy and Fourier transform infrared spectroscopy. The ablation surfaces produced with 2 ?? J / cm 2 presented an irregular morphology with exposed dentinal tubules and no evidence of thermal effects. For 7 and 14 ?? J / cm 2 , the ablation surfaces were covered by a layer of redeposited ablation debris, consisting mainly of amorphous calcium phosphate. This layer is weakly adherent to the underlying tissue and can be easily removed by ultrasonication, revealing a surface with a morphology similar to the one obtained with 2 ?? J / cm 2 . The constitution of the dentin ablation surfaces is similar to the constitution of pristine dentin, showing that, within this fluence range, the laser treatment does not significantly modify the structure and constitution of dentin. The results achieved suggest an ablation mechanism where collagen is preferentially decomposed by the laser radiation, reducing the tissue cohesive strength and leading, ultimately, to its ablation.
authors.affiliation: Lisbon University, Instituto Superior Técnico and CeFEMA, Center of Physics and Engineering of Advanced Materials, Avenida Rovisco Pais, 1049-001 Lisboa, PortugalbLaboratoire ICMCB, CNRS-UPR9048, 87 Avenue du Dr. Albert Schweitzer, 33608 Pessac Cedex, France.
authors.forename: Quang-Tri
authors.initials: QT
authors.lastname: Le
authors.affiliation: Laboratoire ICMCB, CNRS-UPR9048, 87 Avenue du Dr. Albert Schweitzer, 33608 Pessac Cedex, France.
authors.forename: Caroline
authors.initials: C
authors.lastname: Bertrand
authors.affiliation: Lisbon University, Instituto Superior Técnico and CeFEMA, Center of Physics and Engineering of Advanced Materials, Avenida Rovisco Pais, 1049-001 Lisboa, Portugal.
authors.forename: Rui
authors.initials: R
authors.lastname: Vilar
mesh_terms: D002130:Calcium Phosphates; D003804:Dentin / Q000000981:diagnostic imaging* / Q000528:radiation effects*; D006801:Humans; D053685:Laser Therapy; D007834:Lasers; D008855:Microscopy, Electron, Scanning; D008963:Molar / Q000000981:diagnostic imaging / Q000528:radiation effects; D017550:Spectroscopy, Fourier Transform Infrared; D013499:Surface Properties
chemical_list: D002130:Calcium Phosphates; C020243:calcium phosphate