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ObjectiveThis study assessed the relation among several aspects of the masticatory function and the nutritional status in adults with natural dentition. DesignOne hundred adults with natural dentition participated in this cross-sectional study. They performed one free-style masticatory test consisting of five trials of 20 silicon-chewing cycles. The preferred chewing side was determined by calculating the asymmetry index. Masticatory performance was determined by sieving the silicon particles, and the cycle duration was also recorded. Weight, body water percentage, body fat mass, muscle mass and osseous mass were measured using a portable digital weighing machine. Body mass index (BMI), waist-hip ratio, skinfold thickness and the upper-arm composition were determined. The relation between masticatory function and a nutritional variable were tested using Pearson or Spearman rank correlation coefficients or using analysis of variance or the Kruskal-Wallis H-test and the Mann-Whitney U test, as appropriate. ResultsWhereas body fat percentages for women were significantly higher than for men, the body mass index was higher in men than in women. Participants who were underweight chewed more asymmetrically and more slowly than normal weight or obese participants. A negative correlation was observed between body fat percentage and masticatory laterality. No relation between masticatory performance and any nutritional status indicator was detected. ConclusionBeing underweight and having a low body fat percentage seem to be related to a masticatory lateral asymmetry and to a large cycle duration in young adults with natural dentition. Masticatory performance does not seem to be related to nutritional status.

The structural and thermal properties of human tooth enamel, dentine and three synthetic hydroxyapatite samples with Ca/P ratios of 1.57 (Ca deficiency), 1.67 and 1.77 (Ca excess), respectively, were analysed in the temperature range from 20 to 600 °C to have information on the parameters involved in the ionic/electrical conductivities reported for human tooth enamel between 200 and 350 °C approximately. Studies were carried out through x-ray diffraction, thermo-gravimetric analysis, differential scanning calorimetry, Fourier transform infrared spectroscopy and temperature programmed desorption. Chemical analysis was performed by x-ray characteristic energy dispersive spectroscopy. Results indicate a strong correlation between the removal of the OH− groups from the hydroxyapatite unit cell and the expulsion of absorbed water and lattice water registered during heating.

Powder from carious human tooth enamel and dentine were structurally, chemically and thermally analysed and compared against those from sound (healthy) teeth. Structural and chemical analyses were performed using x-ray diffraction, energy-dispersive x-ray spectroscopy and transmission electron microscopy. Thermal analysis was carried out by thermogravimetric analysis, Fourier transform infrared spectroscopy and x-ray diffraction. Results demonstrate partially dissolved crystals of hydroxyapatite (HAP) with substitutions of Na, Mg, Cl and C, and a greater weight loss in carious dentine as compared with carious enamel. A greater amount of thermal decomposition is observed in carious dentine as compared with sound dentine, with major variations in the a-axis of the HAP unit cell than in the c-axis. Variations in shape and intensity of the OH−, and FTIR bands were also found.