Background. A caries lesion causes changes in the optical properties of the affected tissue. Currently a caries lesion can be detected only at a relatively late stage of development. Caries diagnosis also suffers from high interobserver variance. Methods. This is a pilot study to test the suitability of an optical diffuse reflectance spectroscopy for caries diagnosis. Reflectance visible/near-infrared spectroscopy (VIS/NIRS) was used to measure caries lesions and healthy enamel on extracted human teeth. The results were analysed with a computational algorithm in order to find a rule-based classification method to detect caries lesions. Results. The classification indicated that the measured points of enamel could be assigned to one of three classes: healthy enamel, a caries lesion, and stained healthy enamel. The features that enabled this were consistent with theory. Conclusions. It seems that spectroscopic measurements can help to reduce false positives at in vitro setting. However, further research is required to evaluate the strength of the evidence for the method’s performance. 1. Introduction Minimally invasive dentistry is an approach that seeks to maintain the patient’s oral health with preventive measures and to treat possible disturbances of health as early as possible and with as little intervention as possible [1]. This requires that caries is detected at an early stage of development and that its status can be monitored frequently [2]. However, the current methods for diagnosing caries are able to detect caries only at a relatively advanced stage. Accordingly, methods for early detection of caries have been researched for the past twenty years. Many of these methods still require extensive research before they can be used in clinical practice. Optical caries diagnosis methods are based on the fact that caries cause changes in the tooth’s optical properties at an early stage of development [3]. This was a pilot study to investigate whether diffuse reflectance visible/near-infrared spectroscopy (VIS/NIR-S) can be used to detect dental caries lesions. Reflectance spectroscopy measures the intensity of light at several different wavelengths, that is, its spectra, after the light has reflected from the studied object. Diffuse reflectance refers to light that has been reflected from the inside of the object, rather than from its surface. In this study the intensity was measured at wavelengths in the visible range and at wavelengths in the near-infrared range, covering wavelengths in the range 420–1000？nanometers. Within this range, the intensity
References
[1]
N. Wilson and A. Plasschaert, “Dental caries, minimally invasive dentistry and evidencebased clinical practice,” in Minimally Invasive Dentistry-the Management of Caries, N. H. F. Wilson, Ed., pp. 1–6, Quintessence, 2007.
[2]
R. S. Jones, G. D. Huynh, G. C. Jones, and D. Fried, “Near-infrared transillumination at 1310-nm for the imaging of early dental decay,” Optics Express, vol. 11, no. 18, pp. 2259–2265, 2003.
[3]
L. Karlsson, “Caries detection methods based on changes in optical properties between healthy and carious tissue,” International Journal of Dentistry, vol. 2010, Article ID 270729, 9 pages, 2010.
[4]
C. M. Bühler, P. Ngaotheppitak, and D. Fried, “Imaging of occlusal dental caries (decay) with near-IR light at 1310-nm,” Optics Express, vol. 13, no. 2, pp. 573–582, 2005.
[5]
R. S. Jones, Near-Infrared Optical Imaging of Early Dental Caries, University of California, San Francisco, Calif, USA, 2006.
[6]
J. Wu and D. Fried, “High contrast near-infrared polarized reflectance images of demineralization on tooth buccal and occlusal surfaces at λ？=？1310-nm,” Lasers in Surgery and Medicine, vol. 41, no. 3, pp. 208–213, 2009.
[7]
M. Staninec, C. Lee, C. L. Darling, and D. Fried, “In vivo near-IR imaging of approximal dental decay at 1,310？nm,” Lasers in Surgery and Medicine, vol. 42, no. 4, pp. 292–298, 2010.
[8]
D. Fried, J. D. B. Featherstone, C. L. Darling, R. S. Jones, P. Ngaotheppitak, and C. M. Bühler, “Early caries imaging and monitoring with near-infrared light,” Dental Clinics of North America, vol. 49, no. 4, pp. 771–793, 2005.
[9]
I. A. Pretty, “Caries detection and diagnosis: novel technologies,” Journal of Dentistry, vol. 34, no. 10, pp. 727–739, 2006.
[10]
C. Zakian, I. Pretty, and R. Ellwood, “Near-infrared hyperspectral imaging of teeth for dental caries detection,” Journal of Biomedical Optics, vol. 14, no. 6, Article ID 064047, 2009.
[11]
A. M. A. Maia, D. D. D. Fonseca, B. B. C. Kyotoku, and A. S. L. Gomes, “Evaluation of sensibility and specificity of NIR transillumination for early enamel caries detection—An in vitro study,” in Proceedings of the European Conference on Lasers and Electro-Optics and the European Quantum Electronics Conference (EQEC '09), p. 1, IEEE, June 2009.
[12]
L. Karlsson, Optical Based Technologies for Detection of Dental Caries, Karolinska Institutet, 2009.
[13]
W. A. Pena, Optical Imaging of Early Dental Caries in Deciduous Teeth With Near-IR Light at 1310？nm, University of California, San Francisco, Calif, USA, 2009.
[14]
C. Lee, D. Lee, C. L. Darling, and D. Fried, “Nondestructive assessment of the severity of occlusal caries lesions with near-infrared imaging at 1310？nm,” Journal of Biomedical Optics, vol. 15, no. 4, Article ID 047011, 2010.
[15]
S. Chung, D. Fried, M. Staninec, and C. L. Darling, “Near infrared imaging of teeth at wavelengths between 1200 and 1600？nm,” in Lasers in Dentistry XVII, vol. 7884 of Proceedings of SPIE, San Francisco, Calif, USA, January 2011.
[16]
J. A. Weatherell, C. Robinson, and A. S. Hallsworth, “Variations in the chemical composition of human enamel,” Journal of Dental Research, vol. 53, no. 2, pp. 180–192, 1974.
[17]
M. Marquezan, F. N. P. Corrêa, M. E. Sanabe et al., “Artificial methods of dentine caries induction: a hardness and morphological comparative study,” Archives of Oral Biology, vol. 54, no. 12, pp. 1111–1117, 2009.
[18]
T. Aoba, “Solubility properties of human tooth mineral and pathogenesis of dental caries,” Oral Diseases, vol. 10, no. 5, pp. 249–257, 2004.
