To clarify the effect of aging on the microstructure and mechanical properties of dentine.

The third molars were collected in youth group (n= 10) and in aging group (n= 10) respectively. In each group, five samples parallel to or perpendicular to the dentinal tubules were prepared. The mechanical properties were measured using the displacement method. The microstructures were observed using scanning electron microscope (SEM) . The effects of aging on the microstructure and the mechanical properties of dentine were analyzed. Statistical analysis was performed using double factor variance analysis at a significance level of 0.05.

The majority of tubules in the aging dentine were completely filled with mineral. The diameters of the aging dentine tubules were reduced and some were closed compared with those of youth dentine. Meanwhile, the mechanical properties changed with the dentine aging. For elasticity modulus, the young group[ (15.1 ± 2.1) , (17.0 ± 1.6) GPa] was higher than aging group [ (11.6 ± 2.2) , (13.7 ± 2.0) GPa] with statistically significant difference (F= 14.20, P= 0.002) . The parallel loading group[ (15.1 ± 2.1) , (11.6 ± 2.2) GPa] was lower than perpendicular loading group[ (17.0 ± 1.6) , (13.7 ± 2.0) GPa] with statistically significant difference (F= 4.85, P= 0.04) . For elastic limit, the young group [ (157 ± 14) , (165 ± 12) MPa] was higher than aging group [ (140 ± 4) , (140 ± 13) MPa], and the difference was statistically significant (F= 16.76, P= 0.001) .

The age-related changes of dentine affected the microstructure and compression mechanical properties. The compressive mechanical properties of dentine decreased with age.