BACKGROUND: Laser Induced Breakdown Spectroscopy (LIBS) can be used to measure trace element concentrations in solids, liquids and gases, with spatial resolution and absolute quantifaction being feasible, down to parts-per-million concentration levels. Some applications of LIBS do not necessarily require exact, quantitative measurements. These include applications in dentistry, which are of a more "identify-and-sort" nature - e.g. identification of teeth affected by caries. METHODS: A one-fibre light delivery / collection assembly for LIBS analysis was used, which in principle lends itself for routine in vitro / in vivo applications in a dental practice. A number of evaluation algorithms for LIBS data can be used to assess the similarity of a spectrum, measured at specific sample locations, with a training set of reference spectra. Here, the description has been restricted to one pattern recognition algorithm, namely the so-called Mahalanobis Distance method. RESULTS: The plasma created when the laser pulse ablates the sample (in vitro / in vivo), was spectrally analysed. We demonstrated that, using the Mahalanobis Distance pattern recognition algorithm, we could unambiguously determine the identity of an "unknown" tooth sample in real time. Based on single spectra obtained from the sample, the transition from caries-affected to healthy tooth material could be distinguished, with high spatial resolution. CONCLUSIONS: The combination of LIBS and pattern recognition algorithms provides a potentially useful tool for dentists for fast material identification problems, such as for example the precise control of the laser drilling / cleaning process.

Institute of Physical Engineering Technical University Brno Technická 2 616 69 Brno Czech Republic

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Murray JJ. The prevention of Dental Disease. Oxford University Press, Oxford. 1990.

Niemz MH. Laser-tissue interactions. Springer Verlag, Berlin. 1996.

Takamori K, Hokari N, Okumura Y, Watanabe S. Detection of oclusal caries under sealant by use of a laser fluorescence system. J Clin Laser Med Surgery. 2001;19:267–271. doi: 10.1089/10445470152612008. PubMed DOI

Stookey GK, Gonzales-Cabezas C. Emerging methods of caries diagnosis. J Dent Educ. 2001;65:1001–1006. PubMed

Schneiderman A, Elbaum M, Schultz T, Keem S, Greenebaum M, Driller J. Assessment of dental caries with Digital Imaging Fibre-Optics Transillumination (DIFOTI): in vitro study. Caries Res. 1997;31:103–110. PubMed

Nair MK, Tyndall DA, Ludlow JB, May K. Tuned aperture computed tomography and detection of recurrent caries. Caries Res. 1998;32:23–30. doi: 10.1159/000016426. PubMed DOI

Abreu M, Tyndall DA, Ludlow JB, Nortje CJ. The effect of the number of iterative restorations on tuned aperture computed tomography for approximal caries detection. Dentomaxillofac Radiol. 2001;30:325–329. doi: 10.1038/sj.dmfr.4600636. PubMed DOI

Wenzel A. Digital radiography and caries diagnosis. Dentomaxillofac Radiol. 1998;27:3–11. doi: 10.1038/sj/dmfr/4600321. PubMed DOI

Zero DT. Applications of clinical models in remineralization research. J Clin Dent. 1999;10:74–85.

McIntyre JM, Featherstone JDB, Fu J. Studies of dental root surface caries. 2: The role of cementum in root surface caries. Australian Dent J. 2000;45:97–102. PubMed

Kruger J, Kautek W, Newesely H. Femtosecond-pulse laser ablation of dental hydroxyapatite and single-crystalline fluoroapatite. Appl Phys A. 1999;69:S403–407. doi: 10.1007/s003390051426. DOI

Kohns P, Zhou P, Stormann R. Effective laser ablation of enamel and dentine without thermal side effects. J Laser Appl. 1997;9:171–174. PubMed

Hibst R. Applications of lasers in dentistry – a survey. LaserOpto. 2000;32:46–52.

Fried D, Zuerlein M, Featherstone JDB, Seka W, Duhn C, McCormack SM. IR laser ablation of dental enamel: mechanistic dependence on the primary absorber. Applied Surface Science. 1998;127-129:852–856. doi: 10.1016/S0169-4332(97)00755-1. DOI

Altshuler GB, Belikov AV, Sinelnik YA. A laser-abrasive method for the cutting of enamel and dentine. Laser Surg Med. 2001;28:435–444. doi: 10.1002/lsm.1071.abs. PubMed DOI

Fried D, Ragadio J, Champion A. Residual heat deposition in dental enamel during IR laser ablation at 2.79, 2.94, 9.6 and 10.6 μm. Laser Surg Med. 2001;29:221–229. doi: 10.1002/lsm.1111. PubMed DOI

Eguro T, Maeda T, Tanabe M, Otsuki M, Tanaka H. Adhesion of composite resins to enamel irradiated by the Er:YAG laser: application of the ultrasonic scaler on irradiated surface. Laser Surg Med. 2001;28:365–370. doi: 10.1002/lsm.1063. PubMed DOI

Jeffries T. Quintupled YAG probes 200-year-old teeth to uncover ancient diet details. Opto Laser Europe. 2001. p. 15.

Majidi V, Joseph MR. Spectroscopic Applications of Laser-Induced Plasmas. Critical Reviews in Analytical Chemistry. 1992;23:143–162.

Radziemski LJ. Review of Selected Analytical Applications of Laser Plasmas and Laser Ablation 1987–1994. Microchemical Journal. 1994;50:218–234. doi: 10.1006/mchj.1994.1090. DOI

Samek O, Liška M, Kaiser J, Beddows DCS, Telle HH, Kukhlevsky S. Clinical application of laser-induced breakdown spectroscopy to the analysis of teeth and dental materials. J Clinical Laser Medicine & Surgery. 2000;18:281–289. PubMed

Beddows DCS, Kondo H, Morris GW, Telle HH. Remote laser-induced breakdown spectroscopy using a novel single-fibre arrangement. CLEO/Europe – EQEC '98, Glasgow 1998: Technical Digest. p. 237.

Samek O, Beddows DCS, Kaiser J, Kukhlevsky S, Liška M, Telle HH, Young J. The application of laser induced breakdown spectroscopy to in situ analysis of liquid samples. Optical Engineering. 2000;39:2248–2262. doi: 10.1117/1.1304855. DOI

Amador-Hernandez J, Fernandez-Romero JM, Luque de Castro MD. In-depth characterization of screen-printed electrodes by laser-induced breakdown spectroscopy and pattern recognition. Surf Interface Anal. 2001;31:313–320. doi: 10.1002/sia.979. DOI

Samek O, Krzyzanek V, Beddows DCS, Telle HH, Kaiser J, Liška M. Material identification using laser spectroscopy and pattern recognition algorithms. Lecture Notes in Computer Science. 2001;2124:443–450.

Diffuse Reflectance Spectroscopy as a Novel Method of Caries Detection-An In Vitro Comparative Study in Permanent Teeth