title: Morphological and ultrastructural comparative analysis of bone tissue after Er:YAG laser and surgical drill osteotomy.
abstract: OBJECTIVE
  The purpose of this study was to analyze morphological, chemical, and crystallographic changes of bone tissue after osteotomy performed with an erbium:yttrium-aluminium-garnet (Er:YAG) laser and a low speed pilot drill.
  
  
  METHODS
  Bone blocks were prepared from porcine ribs, and on each block, two tunnel preparations were performed using the Er:YAG laser (pulse energy: 1000 mJ, pulse duration: 300 μs, pulse repetition rate: 20 Hz) or the low-speed surgical pilot drill. The morphological changes of the cortical and the spongious surface of the tunnel preparations were analyzed under the field emission scanning electron microscopy (FE-SEM) at low and high resolution. The distribution and the level of chemical elements in the treated surfaces were evaluated by qualitative and semiquantitative energy dispersive x-ray analysis (SEM-EDX). Diffraction x-ray analysis was used to detect any differences and thermally induced modifications of hydroxyapatite crystals.
  
  
  RESULTS
  FE-SEM revealed sharp edges of the Er:YAG preparations, with empty intertrabecular spaces and no signs of carbonization. In the drill group, the surface of the preparations was smooth, completely covered with smear layer and microcracks, and with hairy-like irregularities on the edges. SEM-EDX analysis did not reveal any differences in the number of specific chemical elements between the laser and the drill group. There were no thermally induced modifications of hydroxyapatite crystal structure in the bone tissue in either group.
  
  
  CONCLUSIONS
  The Er:YAG laser ablation did not cause any chemical or crystallographic changes of the bone tissue. Compared with the drill, Er:YAG laser created well-defined edges of the preparations, and cortical bone had no smear layer.
authors.affiliation: 1 Department of Oral Surgery, School of Dental Medicine, University of Zagreb , Zagreb, Croatia .
authors.forename: Dragana Gabric
authors.initials: DG
authors.lastname: Panduric
authors.forename: Ivona Bago
authors.initials: IB
authors.lastname: Juric
authors.forename: Svetozar
authors.initials: S
authors.lastname: Music
authors.forename: Krešimir
authors.initials: K
authors.lastname: Molčanov
authors.forename: Mato
authors.initials: M
authors.lastname: Sušic
authors.forename: Ivica
authors.initials: I
authors.lastname: Anic
mesh_terms: D000818:Animals; D001842:Bone and Bones / Q000737:chemistry / Q000000981:diagnostic imaging* / Q000528:radiation effects / Q000648:ultrastructure*; D003461:Crystallography; D053844:Lasers, Solid-State; D008855:Microscopy, Electron, Scanning; D010027:Osteotomy / Q000379:methods*; D013552:Swine; D014463:Ultrasonography