title: Effect of CO2 laser on pulpal temperature and surface morphology: an in vitro study.
abstract: OBJECTIVE
  The objective of this study was to evaluate the potential effects on underlying dental hard tissues of a high pulse rate carbon dioxide (CO2) laser that was designed for soft tissue surgery.
  
  
  METHODS
  Eighteen extracted human teeth were sectioned longitudinally, cleaned, and varnished, leaving nine exposed windows on each: six on the coronal surface (enamel) and three on the root surface (cementum, dentin). The CO2 irradiation conditions used were: wave length 10.6 microm; 1.2-2.6J/cm(2) fluence per pulse; repetition rate 120-1000Hz; 100-200ms pulse duration; and cumulative fluences ranging from 14 to 2200J/cm(2). Each window was irradiated with a 0.3mm beam diameter at one of nine power settings for 0.1, 0.5, or 1.0s. The pulp chamber temperature was measured with a microthermocouple. The irradiated teeth were evaluated by Polarized Light Microscopy (PLM) and Scanning Electron Microscopy (SEM).
  
  
  RESULTS
  The pulp chamber temperature rise ranged from 0.5 to 19 degrees C depending on the location of the window and distance to pulp chamber. SEM revealed crystal fusion in both enamel and dentin at all cumulative fluences. At cumulative fluences of 40J/cm(2), 200 pulses/second and higher, measurable tissue loss was observed with PLM both in dentin and enamel.
  
  
  CONCLUSIONS
  These results indicate there are threshold conditions above which pulsed CO2 laser light used for soft tissue surgery may cause detrimental changes to underlying oral hard tissue and to the pulp.
authors.affiliation: Eastman Dental Center, University of Rochester, Rochester, NY 14620-2989, USA. hans_mamlstrom@urmc.rochester.edu
authors.forename: H S
authors.initials: HS
authors.lastname: Malmström
authors.forename: S M
authors.initials: SM
authors.lastname: McCormack
authors.forename: D
authors.initials: D
authors.lastname: Fried
authors.forename: J D
authors.initials: JD
authors.lastname: Featherstone
mesh_terms: D001831:Body Temperature / Q000502:physiology*; D002245:Carbon Dioxide; D003460:Crystallization; D003739:Dental Cementum / Q000648:ultrastructure; D003743:Dental Enamel / Q000648:ultrastructure; D003782:Dental Pulp / Q000502:physiology*; D003786:Dental Pulp Cavity / Q000502:physiology; D003804:Dentin / Q000648:ultrastructure; D006801:Humans; D007091:Image Processing, Computer-Assisted; D053685:Laser Therapy / Q000295:instrumentation; D007834:Lasers / Q000145:classification; D008855:Microscopy, Electron, Scanning; D008859:Microscopy, Polarization; D008904:Miniaturization; D013821:Thermometers; D014070:Tooth / Q000648:ultrastructure*; D019228:Tooth Crown / Q000648:ultrastructure; D014092:Tooth Root / Q000648:ultrastructure
chemical_list: D002245:Carbon Dioxide