title: The effect on the ultrastructure of dental enamel of excimer-dye, argon-ion and CO2 lasers.
abstract: This study aimed to investigate the ultrastructural changes that occur in dental enamel irradiated with pulsed excimer-dye, continuous-wave (CW) argon-ion and CW CO2 lasers. The pulsed excimer-dye laser produced deep craters, rough damaged surfaces with underlying porosity and amorphous vitrified material. The vitrification of the enamel indicated that the temperature in these areas must have been at least in the range 1280 to 1600 degrees C. The CW argon-ion laser irradiation produced a changed non-cratered surface with inter-crystalline porosity and a mixture of small and some large irregularly packed recrystallized enamel crystals. The CW CO2 laser produced shallow craters, surface crazing and lifting off the removal of the surface layer to expose the underlying roughened enamel. The ultrastructure revealed inter- and intra-crystalline porosity, a mixture of small but variable size irregularly packed recrystallized enamel crystals and also well packed large crystals which indicated further grain growth. The porosity in lased enamel was overall very similar to that seen in enamel heated in an electric furnace to a temperature of 600 degrees C. The presence of recrystallized enamel crystals indicated a temperature rise of approximately 1000 degrees C and the grain growth indicated that a temperature > or = 1000 degrees C existed for some time after the laser irradiation. In general the excimer-dye laser produced most surface destruction because of its higher power density and shorter interaction time and the argon-ion laser produced least damage. These results indicated that the lasers used in this study require much more refinement before they can find therapeutic application to dental enamel, and this may well be the case for other lasers being investigated for clinical dental practise.
authors.affiliation: Department of Physics, Monash University, Clayton, Victoria, Australia.
authors.forename: J
authors.initials: J
authors.lastname: Palamara
authors.forename: P P
authors.initials: PP
authors.lastname: Phakey
authors.forename: H J
authors.initials: HJ
authors.lastname: Orams
authors.forename: W A
authors.initials: WA
authors.lastname: Rachinger
mesh_terms: D001128:Argon; D002245:Carbon Dioxide; D003743:Dental Enamel / Q000528:radiation effects / Q000648:ultrastructure*; D006801:Humans; D007834:Lasers / Q000009:adverse effects*; D008854:Microscopy, Electron; D008855:Microscopy, Electron, Scanning
chemical_list: D002245:Carbon Dioxide; D001128:Argon