Age-related changes of the cementogenesis in the senescence-accelerated mouse (SAM)

Cementogenesis of the molars with aging was studied using senescence accelerated mouse (SAM) which included SAMP2/Iw and SAMP8@Iw as prone strains, and SAMR1/Iw as a resistant strain. Morphometric analysis was done for the cementum thickness at 2, 6, 12 and 16 months of age on 4 parts of the mice, i.e. at the mesial (M), the distal (D), the apical (A) and the furcational (F) cementum of the maxillary first molar. SAMR1/Iw was also studied at 20 months of age. Mean cementum thickness was statistically analyzed for age and strain differences. Mean thicknesses of the M and the D cementum in SAMP2/Iw and in SAMP8@Iw were usually higher than those in SAMR1/Iw. Furthermore, there were significant differences between SAMP2/Iw and SAMR1/Iw, and between SAMP8/Iw and SAMR1/Iw, both at 12 and 16 months of age. There was no difference in mean thickness in the F cementum in either strain and at any age. In the A cementum, SAMP2/Iw displayed significantly thicker cementum than SAMR1/Iw at 6, 12 and 16 months of age. The degree of molar eruption was thought to be more accelerated in SAMP2/Iw than in SAMR1/Iw. However, the thickness of the A cementum was not different for SAMP8@Iw and SAMR1/Iw in any age group. In this study, 2 conclusions were drawn as follows: first, that SAMP2/Iw and SAMP8@Iw exhibited more accelerated cementogenesis than SAMR1/Iw in the M and the D cementum. Secondly, several factors such as intrinsic factors, occlusal forces and degree of attrition affected the cementogenesis of the M and the D, the F and the A cementum, respectively.