A NOVEL METHOD FOR DIRECT NONDESTRUCTIVE DIAGNOSIS OF CARIES AFFECTED TOOTH SURFACES BY LASER MULTIPHOTON IONIZATION Natalia Vinerot, 1 Yuheng Chen, 1 Vladimir V. Gridin, 1 Valery Bulatov, 1 Liviu Feller, 2 and Israel Schechter 1 1 Schulich Department of Chemistry, Technion-Israel Institute of Technology, Haifa, Israel 2 Department of Periodontology and Oral Medicine School of Dentistry, Medunsa Oral Health Centre, University of Limpopo, South Africa & A new nondestructive analytical method for diagnosis of tooth caries is presented. The method is based on the Multiphoton Ionization (MPI) fast conductivity signals measured from tooth surfaces. The signals are acquired for a series of laser wavelengths, thus obtaining full MPI spectra. The results indicate a good correlation between the MPI results and the degree of severity of the caries, as diagnosed using traditional inspection. Moreover, the spectral information can be reduced (using least squares fitting) to a single parameter that provides an objective quantitative estimation of the caries severity. The MPI data can be obtained for tiny points on the dental surface and it is suggested that mapping is possible by scanning method. Keywords diagnosis of caries, laser multiphoton ionization, nondestructive, tooth surfaces INTRODUCTION Multiphoton Ionization (MPI) is a process that takes place under high irradiation intensities, and in which the irradiated material simultaneously absorbs several photons. The ionization process depends on the ionization potential of the examined materials at the irradiation spot. The ejected photoelectrons are separated using a high electric field and the resulted current is monitored. It has been shown that the time integrated current is directly related to the irradiated chemical compounds. [1] The so called fast-conductivity data acquisition method allows for using MPI for direct chemical analysis under ambient conditions. The main advantage of this Address correspondence to Israel Schechter, Schulich Department of Chemistry, Technion-Israel Institute of Technology, Haifa 32000, Israel. E-mail: Israel@techunix.technion.ac.il Instrumentation Science and Technology , 38:143–150, 2010 Copyright # Taylor & Francis Group, LLC ISSN: 1073-9149 print/1525-6030 online DOI: 10.1080/10739141003591475 Downloaded By: [Schechter, Israel] At: 20:27 1 March 2010