ORIGINAL PAPER A crystallinity study of dental tissues and tartar by infrared spectroscopy J. A. Abraham & H. J. Sánchez & C. A. Marcelli & M. Grenón & M. C. Guidi & M. Piccinini Received: 28 April 2010 / Revised: 9 August 2010 / Accepted: 9 November 2010 / Published online: 1 December 2010 # Springer-Verlag 2010 Abstract In this paper we report a study of an important property of biomineralized phases, crystallinity, on the basis of previous results for synthetic apatite. Crystallinity is not only important for understanding biomineralization, it is also related to the maturation and mechanisms of growth of calcium phosphates in biological surroundings. We studied two kinds of sample, teeth as an example of biomineralized tissues and dental calculi (adhering) as an example of mineralization without participation of biological agents, except possibly bacteria. The investigation focused on study of ν 1 –ν 3 infrared absorption bands of PO 4 3– phos- phates. We used ATR (attenuated total reflection) analysis to examine human dental tissues and tartar on several samples. The results confirm for the first time previous assumptions about the growth and maturation of dental calculi, i.e., crystallinity progresses from regions of high crystallinity to regions of lower crystallinity, and, in addition, its quantification with spatial resolution in the sample. A gradual pattern was observed in dental calculus. Another result from this study was that cementum and dentine had similar crystallinity, despite their different biological and mechanical functions. Keywords Crystallinity . Dental calculi . Tooth . Infrared spectroscopy . Biomineralization . Attenuated total reflection Introduction Study of the crystallinity of biological calcium phosphates is important for several reasons. Biologically, knowledge of the crystallinity or degree of crystallization of hard tissues could be relevant to diagnosis of diseases related to dissolution of osseous mass, for example osteoporosis. In prosthesis manufacture, knowing the factors that affect crystallinity could improve the manufacturing process, because these elements are usually covered by calcium phosphates on the metallic surfaces that will be in contact with bone. It is expected that the calcium phosphates covering the prosthetic element resemble the characteristics of bone and have similar crystallinity, in favor of rapid acceptance by the body system and low chance of rejection. In the same way, in dentistry, this characterization is also important in dental implants for the same reason, moreover it could be important for understanding the growth, maturation, and adhesion of dental calculus on the surface of teeth. The crystallinity of tartar is related to the process of growth, because maturation of calcium phosphate phases in this kind of deposit is not homogeneous but varies gradually. Some authors consider that crystallization follows the same behavior. Insights into characterization of the crystallinity of the zone of adhesion between tartar and the dental surface, could be useful for chemical or other detachment mechanisms less traumatic than abrasive removal. Crystallinity is relevant for biomineralization also. Biomineralization is a very complex process in which hard tissues of some animals, i.e. bones, teeth, ivory, shells, etc., are formed by microorganisms and proteins. In addition to proteins, polysaccharides and proteoglycans are emerging as important components of the organic matrices associated with biominerals. Also, physical and chemical mechanisms J. A. Abraham (*) : H. J. Sánchez : M. Grenón Universidad Nacional de Córdoba, 5000 Córdoba, Argentina e-mail: jabraham.famaf@gmail.com C. A. Marcelli : M. C. Guidi : M. Piccinini INFN, Laboratori Nazionale di Frascati, 00044 Frascati, Italy Anal Bioanal Chem (2011) 399:1699–1704 DOI 10.1007/s00216-010-4430-0