title: Surface damages of zirconia by Nd:YAG dental laser irradiation.
abstract: The purpose of this study was to characterize the surface damages of zirconia by Nd:YAG dental laser irradiation through a systematic evaluation of the associated microstructural changes. Disk specimens of yttria-stabilized tetragonal zirconia polycrystals (Y-TZP) and ceria-stabilized zirconia/alumina nanocomposite (Ce-TZP/Al₂O₃ nanocomposite) were irradiated by Nd:YAG dental laser. The specimens were characterized using scanning electron microscopy, X-ray diffractometry, and wavelength dispersive X-ray spectroscopy. Every single irradiated spot was indicated by a circular black pit surrounded by a circular raised rim with a sunken depression at the center. On surface changes, many cracks were formed inside each irradiated pit. On changes in elemental composition, the concentration of oxygen decreased while that of zirconium increased. After heating in air, the assembly of circular black pits turned white, although the depression and raised rim remained. This study showed that Nd:YAG dental laser irradiation induced cracking and reduced oxygen content on the surface of zirconia. Consequently, these phenomena reduced the mechanical strength of zirconia. Therefore, Nd:YAG dental laser welding should not be performed on tetragonal zirconia.
authors.affiliation: Department of Biomaterials Science, Graduate School of Medical and Dental Sciences, Kagoshima University, 8-35-1 Sakuragaoka, Kagoshima 890-8544, Japan. k2769021@kadai.jp
authors.forename: Makoto
authors.initials: M
authors.lastname: Noda
authors.forename: Yuji
authors.initials: Y
authors.lastname: Okuda
authors.forename: Jiro
authors.initials: J
authors.lastname: Tsuruki
authors.forename: Yoshito
authors.initials: Y
authors.lastname: Minesaki
authors.forename: Yasumi
authors.initials: Y
authors.lastname: Takenouchi
authors.forename: Seiji
authors.initials: S
authors.lastname: Ban
mesh_terms: D000388:Air; D000537:Aluminum Oxide / Q000737:chemistry / Q000528:radiation effects; D002563:Cerium / Q000737:chemistry / Q000528:radiation effects; D003116:Color; D003776:Dental Porcelain / Q000737:chemistry / Q000528:radiation effects*; D006358:Hot Temperature; D006801:Humans; D053844:Lasers, Solid-State; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D053761:Nanocomposites / Q000737:chemistry / Q000528:radiation effects; D010100:Oxygen / Q000032:analysis; D013052:Spectrometry, X-Ray Emission; D013314:Stress, Mechanical; D013499:Surface Properties; D014961:X-Ray Diffraction; D015019:Yttrium / Q000737:chemistry / Q000528:radiation effects; D015040:Zirconium / Q000032:analysis / Q000737:chemistry / Q000528:radiation effects*
chemical_list: C475766:Ce-TZP-Al2O3; C499362:yttria stabilized tetragonal zirconia; D003776:Dental Porcelain; D002563:Cerium; D015019:Yttrium; D015040:Zirconium; D000537:Aluminum Oxide; C028541:zirconium oxide; D010100:Oxygen