14. Chemical composition of human enamel and dentin. Preliminary results to determination of the effective atomic number
Madelon A. F. Zenóbioa, Maria S. Nogueira*a, and Elton G. Zenóbiob aDevelopment Centre for Nuclear Technology (CDTN / CNEN – MG), Rua Mário Werneck, s/n, Cidade Universitária- Pampulha, Belo Horizonte, Brazil. b Pontiff University Catholic – PUC/Minas,Av. Dom José Gaspar, 500, Coração Eucarístico- Belo Horizonte, Brazil.
Abstract.
The theoretical or practical dosimetry involving radiation interactions in humans needs the reliable elemental composition data of body tissues. The object of this research was to obtain the characterization dental hard tissues and to determine its effective atomic number. An analytical research of inorganic composition, from 30 intact human molars, extracted for periodontal reasons, was performed by Neutron Activation Analysis (NAA), ICP/AES, Thermogravimetric (TG) and Differential Thermal Analysis (DTA). The coronal dentin and enamel were separated by two techniques: (1) – mechanically by chipping and breaking by chirurgic hammer, allowed to dry in an electric oven for 5 hours at 1600C. (2) – through by high-running round steel burs. The samples were thoroughly cleaned with distilled deionizer water and sent for analysis in CDTN/CNEN laboratories, Belo Horizonte, Minas Gerais, Brazil. The results showed concentrations of 11 elements measured in dentin and enamel. The five elements of the higher concentration by neutron activation analysis and ICP/AES were Ca, P, Na, Mg and Al. Thermogravimetric analysis of enamel showed a loss of water of hydroxyapatite to 5000C. Thermogravimetric analyses of dentin showed tree temperatures at which mass loss occur. These processes are related to superficial water loss (100oC); organic decomposition and water liberation from hydroxyapaptite (100oC to 600oC); and the beginning of hydroxyapatite decomposition (600oC to 850oC). Differences, in mineral concentration, were found between enamel and dentin, with higher concentrations in enamel. The two techniques proposed to separated dentin and enamel, no presented differences in elements concentration, statement that the high-running round steel burs technique didn’t affected the samples.
KEYWORDS: Dental materials, Dentin, enamel, Thermal analysis, nuclear analysis, dosimetry
CONCLUSION
The analyses through INAA, ICP/AES and TGA/D allowed for the identification of the element composition present in dentin and enamel. These analyses are a tool for the quantitative and qualitative determination of components of human dental which are necessary for the evaluation of the effective atomic number. The results of this study show the advantages in analyzing the enamel and dentin separately. It was possible to identifying the composition of these portions in human teeth and the difference in the mineral and organic composition.