title: Anelastic phenomena associated to water loss and collagen degradation in human dentin.
abstract: This work describes the anelastic and dynamic Young modulus behaviour of human dentin from room temperature up to 673 K. Human molars, extracted from individuals (males 55-70 years old) as part of their dental treatment, were cut to obtain bar-shaped samples subsequently used for mechanical spectroscopy experiments. In addition, thermo-gravimetric analysis (TGA) has been performed to assess a possible weight loss occurring in the same temperature range of mechanical spectroscopy tests. A broad and asymmetric internal friction (Q(-1)) maximum at 500 K has been observed during the heating of the as-prepared samples. This maximum is absent during the following cooling down to room temperature. It is therefore due to the occurrence of an irreversible transformation in the sample. TGA shows a remarkable weight loss in the same temperature range. This effect has been related to loss of fluids and degradation of collagen. Another set of samples, previously kept for 36 h under a vacuum of 10(-2)Pa, were submitted at room temperature to test at increasing strain from 6×10(-6) to 7×10(-4). The results show transient and fully recoverable Q(-1) increase and dynamic modulus (E) decrease. The phenomenon has been ascribed to the breaking of weak H-bonds between polypeptide chains forming the triple-helix with consequent increase of the mean length of vibrating chain segments.
authors.affiliation: Department of Physics and Astronomy, University of Bologna, Viale Berti Pichat 6/2, 40127 Bologna, Italy. stefano.amadori4@unibo.it
authors.forename: S
authors.initials: S
authors.lastname: Amadori
authors.forename: E
authors.initials: E
authors.lastname: Bonetti
authors.forename: E G
authors.initials: EG
authors.lastname: Campari
authors.forename: I
authors.initials: I
authors.lastname: Cappelloni
authors.forename: R
authors.initials: R
authors.lastname: Montanari
mesh_terms: D000368:Aged; D003094:Collagen / Q000378:metabolism*; D003804:Dentin / Q000378:metabolism*; D055119:Elastic Modulus; D004548:Elasticity; D017276:Friction; D006801:Humans; D008297:Male; D008855:Microscopy, Electron, Scanning; D008875:Middle Aged; D059748:Proteolysis; D013696:Temperature; D013818:Thermogravimetry; D014867:Water / Q000737:chemistry*
chemical_list: D014867:Water; D003094:Collagen
keywords: Collagen; Dentin; Dynamic modulus; Internal friction