Mechanics behind 4D interferometric measurement of biofilm mediated tooth decay. Michael S. Waters1, Bin Yang2, Nancy J. Lin1 and Sheng Lin-Gibson1* 1 National Institute of Standards and Technology, Materials Science Engineering Laboratory, Polymers Division, Biomaterials Group, 100 Bureau Dr., Mail Stop 8543, Gaithersburg, MD 20899-8543 2 American Dental Association Foundation, 100 Bureau Dr., Mail Stop XXXX, Gaithersburg, MD 20899-XXXX * To whom correspondence should be addressed. ABSTRACT Evaluating the efficacy of dental materials to protect human teeth requires the capacity to measure tooth decay. Currently, practices for determining tooth decay are destructive, qualitative to lowly quantitative, and/or measure bulk changes that have low to no spatial resolution. The combination of the highly variable nature of tooth enamel and the inability to perform serial analyses on the same spatial location limits the capacity to access reproducible information from any experimental set. To help complement the void left by other techniques, this study explores the potential of interferometric optical profilometry to make rapid precision measurements in 3dimensions over time of human tooth enamel decay. Using unique techniques in raw interferometric data evaluation in combination with specially designed biocompatible 3-D alignment translation stages, human tooth decay was measured with respect to pathogenic dental bacterial biofilms. These investigations revealed the capacity to quantitatively determine the rate of tooth decay in previously unseen spatial and temporal scales (4D). These new, rapid, low-cost techniques minimize effort for sample preparation and use very few consumables, opening the feasibility for high-throughput investigations of clinical dental materials to a wider international community. INTRODUCTION Tooth decay is one of the most rampant, chronic, communicable diseases (1, 6). 94% of adults in the United States have manifested coronal caries (a form of cavity) sometime within their life. Tooth decay is primarily caused by a mixed consortium of oral bacteria, which aggregate to colonize the cracks and crevices of the teeth and the region from the gingival line to the periodontal interface, forming a biofilm that is highly resistant to harsh environments, including abrasion and antibiotics. Streptococcus mutans, the bacteria considered to be the primary causative agent of dental caries, secretes lactic acid in a surface-attached bacterial biofilm, inhibiting growth of other bacteria giving itself an opportunity to dominate and dissolve the calcium hydroxyapatite material of the tooth surface (3-5). One of the major challenges to overcome in the battle against tooth decay is the capacity to measure the effectiveness of any therapeutic agent on dental health. This is due in large part to the hypervariable nature of teeth, both between different people and even within a single tooth (7). Teeth are made of calcium hydroxyapatite formed into 2 different major structures: enamel and dentin. Dentin is a tubular material that makes up the majority of the tooth, which connects to the mandibular bones. A thick, hard, impact- and wear-resistant enamel cap covers the top of T. Proulx (ed.), Optical Measurements, Modeling, and Metrology, Volume 5, Conference Proceedings of the Society for Experimental Mechanics Series 9999999, DOI 10.1007/978-1-4614-0228-2_41, © The Society for Experimental Mechanics, Inc. 2011 337
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