ABSTRACT As the prevalence of dental caries decreases, the diagnosis and treatment of initial mineral loss resulting in white spot lesions have been getting more and more important. Since dental CT provides computed tomography images of a tooth with radiation exposure similar to panoramic radiography, it will become possible in the near future to evaluate the enamel mineral density using CT in the same way as measurement of the bone mineral density. Such computed tomography images enable dentists to perform longitudinal, three-dimensional, and precise evaluation of the enamel mineral density before a demineralized lesion becomes detectable by any other traditional means. Despite their advantage, there are not enough reports on evalu- ation of the enamel mineral density using CT. This study evaluated the serial changes in mineral density in the earliest stage of enamel demineralization. Eight bovine enamel specimens were coated with nail varnish. On each specimen, 4 square windows measuring 1 mm2 were created. The specimens were incubated in lactic acid solution at 38?C. During incubation, the windows were covered by nail varnish one by one at 30, 60, and 90 minutes, respectively. At 120 minutes, the specimens were removed from the solution. After the nail varnish was removed, X-ray microradiography was performed using SKYSCAN1172 at settings of 100 kV and 100 μA. The mean Hounsfield unit values (HUV) of enamel in a non-window area and those in the window areas were calculated every 180 μm over a depth of 0 - 900 μm and analyzed by two-way ANOVA. Data were affected by the incubation time and depth from the enamel surface, and there was not interaction between the
two factors. Considering the incubation time, HUV of the whole measured enamel (0 - 900 μm) in the non-window group was significantly higher than that of the other incubated groups. Considering the depth, HUV was decreased at 721 - 900 μm compared with that at 0 - 180 μm in the 30-minute-incubated group, and the decrease spread to 361 - 900 μm in the 60- and 90- minutes-incubated groups. HUV was additionally calculated at increments of 18 μm and compared within the 60-minute-incubated group, and changes in the mineral density at the boundary of the earliest demineralized lesion could be observed. This study demonstrated detailed mineral density changes in the earliest period of demineralization.
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Watanabe, K. , Nakamura, T. , Ogihara, T. , Ochiai, Y. and Watanabe, S. (2012) Longitudinal evaluation of mineral loss at the earliest stage of enamel demineralization using micro-computed tomography. Health, 4, 334-340. doi: 10.4236/health.2012.46055.
 Ten Cate, J.M., Larsen, M.J., Pearce, E.I.F. and Fejerskov, O. (2008) Dental caries the disease and its clinical Management. 2nd Edition, John Wiley & Sons Ltd., Chichester.
 Featherstone, J.D. (2004) The caries balance: The basis for caries management by risk assessment. Oral Health & Preventive Dentistry, 2, 259-264.
 Featherstone, J.D. (2006) Caries prevention and reversal based on the caries balance. Pediatric Dentistry, 28, 128132.
 Magalh?es, A.C., Moron, B.M., Comar, L.P., Wiegand, A., Buchalla, W. and Buzalaf, M.A. (2009) Comparison of cross-sectional hardness and transverse microradiography of artificial carious enamel lesions induced by different demineralising solutions and gels. Caries Research, 43, 474-483. doi:10.1159/000264685
 Buchalla, W., Imfeld, T., Attin, T., Swain, M.V. and Schmidlin, P.R. (2008) Relationship between nanohardness and mineral content of artificial carious enamel lesions. Caries Research, 42, 157-163.
 Rousseau, C., Vaidya, S., Creanor, S.L., Hall, A.F., Girkin, J.M., Whitters, C.J., Strang, R. and McHugh, S. (2002) The effect of dentine on fluorescence measurements of enamel lesions in vitro. Caries Research, 2002, 36, 381385. doi:10.1159/000066533
 Pretty, I.A., Edgar, W.M. and Higham, S.M. (2003) The erosive potential of commercially available mouthrinses on enamel as measured by Quantitative Light-induced Fluorescence (QLF). Journal of Dentistry, 31, 313-319.
 Clementino-Luedemann, T.N. and Kunzelmann, K.H. (2006) Mineral concentration of natural human teeth by a commercial micro-CT. Dental Materials Journal, 25, 113-119. doi:10.4012/dmj.25.113
 Huang, T.T., Jones, A.S., He, L.H., Darendeliler, M.A. and Swain, M.V. (2007) Characterisation of enamel white spot lesions using X-ray micro-tomography. Journal of Dentistry, 35, 737-743. doi:10.1016/j.jdent.2007.06.001
 Fearne, J., Anderson, P. and Davis, G.R. (2004) 3D X-ray microscopic study of the extent of variations in enamel density in first permanent molars with idiopathic enamel hypomineralisation. British Dental Journal, 196, 634-638.
 Farah, R.A., Swain, M.V., Drummond, B.K., Cook, R. and Atieh, M. (2010) Mineral density of hypomineralised enamel. Journal of Dentistry, 38, 50-58.
 Dowker, S.E., Elliott, J.C., Davis, G.R. and Wassif, H.S. (2003) Longitudinal study of the three-dimensional development of subsurface enamel lesions during in vitro demineralisation. Caries Research, 37, 237-245.
 Shapurian, T., Damoulis, P.D., Reiser, G.M., Griffin, T.J. and Rand, W.M. (2006) Quantitative evaluation of bone density using the Hounsfield index. International Journal of Oral and Maxillofacial Implants, 21, 290-297.
 De Oliveira, R.C., Leles, C.R., Normanha, L.M., Lindh, C. and Ribeiro-Rotta, R.F. (2008) Assessments of trabecular bone density at implant sites on CT images. Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology & Endodontics, 105, 231-238.
 Park, H.S., Lee, Y.J., Jeong, S.H. and Kwon, T.G. (2008) Density of the alveolar and basal bones of the maxilla and the mandible. American Journal of Orthodontics and Dentofacial Orthopedics, 133, 30-37.
 Turkyilmaz, I., Ozan, O., Yilmaz, B. and Ersoy, A.E. (2008) Determination of bone quality of 372 implant recipient sites using Hounsfield unit from mputerized tomography: A clinical study. Clinical Implant Dentistry and Related Research, 10, 238-244.
 Wong, F.S., Anderson, P., Fan, H. and Davis, G.R. (2004) X-ray microtomographic study of mineral concentration distribution in deciduous enamel. Archives of Oral Biology, 49, 937-944. doi:10.1016/j.archoralbio.2004.05.011
 Weatherell, J.A., Robinson, C., Schaper, R. and Künzel, W. (1983) Distribution of fluoride in clinically sound enamel surfaces of permanent upper incisors. Caries Research, 17, 118-124. doi:10.1159/000260659
 Eisenburger, M. (2009) Degree of mineral loss in softened human enamel after acid erosion measured by chemical analysis. Journal of Dentistry, 37, 491-494.
 Arnold, W.H., Gaengler, P., Sabov, K., Schmitz, I., Gedalia, I. and Steinberg, D. (2001) Induction and 3D reconstruction of caries-like lesions in an experimental dental plaque biofilm model. Journal of Oral Rehabilitation, 28, 748-754. doi:10.1046/j.1365-2842.2001.00755.x
 Tanaka, J.L., Medici Filho, E., Salgado, J.A., Salgado, M.A., Moraes, L.C., Moraes, M.E. and Castilho, J.C. (2008) Comparative analysis of human and bovine teeth: radiographic density. Brazilian Oral Research, 22, 346351. doi:10.1590/S1806-83242008000400011
 Tanaka, R., Shibata, Y., Manabe, A. and Miyazaki, T. (2009) Mineralization potential of polarized dental enamel. PLoS One, 4, e5986. doi:10.1371/journal.pone.0005986