Analysis of 14C concentration in teeth to estimate the year of birth in the Mexican population.

The 14C analysis of permanent teeth employing nuclear techniques has a direct application in Forensic Sciences since teeth are the hardest part of the human body and can survive natural decay or extreme conditions. After the first Accelerator Mass Spectrometry Laboratory AMS-LEMA at UNAM, our research group is interested in reproducing 14C analysis on teeth as other countries to estimate age in the Mexican population samples. One of the main goals of this exploratory study is to know the best methodology considering relevant biological factors based on differences in tissues (enamel and dentin) that allows us to know the year of birth through the 14C concentration comparing the yield between 14C analyses from carbonate in enamel and collagen in dentin. In this study, Accelerator Mass Spectrometry (AMS) has been performed in 22 contemporary teeth samples (each one donated from 1 different adult), participating 22 individuals by informed consent to enable a new tool and improve forensic practices in Mexico. Carbon is extracted, converted to graphite, and pressed into a cathode. The sample is taken to an AMS system, where carbon isotopes are separated, counted, and the 14C/12C and 13C/12C ratios determined. Our results for standards and teeth samples from Mexican people are in good agreement with the expected values; they are also useful to set up the best conditions for studies in dentin and enamel. However, this is a destructive technique for dental organs; it is not suitable for individuals born previous 1950. New challenges in sample preparation processes are to be solved to take advantage of the nuclear techniques developed in the last 50 years and make new contributions to society.

Characterization of recombinant human cementum protein 1 (hrCEMP1): primary role in biomineralization.

Cementum protein 1 (CEMP1) has been recently cloned, and in vitro experiments have shown functions as regulator of cementoblast behavior and inducer of differentiation of non-osteogenic cells toward a cementoblastic/osteoblastic phenotype. In this study, we have produced a full-length human recombinant CEMP1 protein in a human gingival fibroblast cell line. The purified protein (hrCEMP1) has a M(r) 50,000. Characterization of hrCEMP1 indicates that its secondary structure is mainly composed of beta-sheet (55%), where random coil and alpha helix conformations correspond to 35% and 10%, respectively. It was found that hrCEMP1 is N-glycosylated, phosphorylated and possesses strong affinity for hydroxyapatite. Even more important, our results show that hrCEMP1 plays a role during the biomineralization process by promoting octacalcium phosphate (OCP) crystal nucleation. These features make CEMP1 a very good candidate for biotechnological applications in order to achieve cementum and/or bone regeneration.

STEM-HAADF electron microscopy analysis of the central dark line defect of human tooth enamel crystallites.

When human tooth enamel is observed with the Transmission Electron Microscope (TEM), a structural defect is registered in the central region of their nanometric grains or crystallites. This defect has been named as Central Dark Line (CDL) and its structure and function in the enamel structure have been unknown yet. In this work we present the TEM analysis to these crystallites using the High Angle Annular Dark Field (HAADF) technique. Our results suggest that the CDL region is the calcium richest part of the human tooth enamel crystallites.