Effects of aging on the mechanical behavior of human dentin

An experimental study on the mechanical behavior of human dentin and the influence of age was conducted. Beams with rectangular cross-section were sectioned from the coronal dentin of virgin extracted molars (N=76) that were obtained from (N=70) patients between 17 and 80 years of age. The beams were loaded in either quasi-static 4-point flexure or 4-point flexural fatigue to failure and the stiffness, strength and fatigue properties were evaluated. In characterizing the fatigue response the beams were divided into two age groups that were regarded as young (17less than or equal toageless than or equal to30, mean+/-std. dev. = 25+/-5 years) and old (50less than or equal toageless than or equal to80, mean +/- std. dev. = 64+/-9 years) dentin. Results from monotonic loading showed that both the flexural strength and strain to fracture of dentin decreased significantly with age. The fatigue life of dentin increased with a reduction in cyclic stress amplitude and the fatigue strength of young dentin was greater than that of old dentin at all cyclic stress amplitudes. The endurance strength of young dentin (at 107 cycles) was approximately 44MPa, whereas the old dentin exhibited an endurance strength of approximately 23 MPa. Based on differences in the mechanical behavior and microscopic features of the fracture surfaces from the young and old specimens, aging appears to result in an increase in both the rate of damage initiation and propagation in dentin. (C) 2004 Elsevier Ltd. All rights reserved.