The effects of aging upon the connective tissues of the periodontal ligament.

The ultrastructural features of the cells and of the oxytalan fibers within the periodontal ligaments of aged rats (2 year old) were quantified and compared with data for tissues obtained from younger animals (8 week old). Sections of the mid-root regions of the mandibular first molars were prepared for examination by TEM. The fibroblasts of the aged rats were found to differ in 3 respects: the areas occupied by endoplasmic reticulum were significantly less, the areas occupied by intracellular collagen profiles were also less, and both the numbers and sizes of intercellular contacts were significantly different (p < 0.05). For the oxytalan fibers, no differences were observed between the periodontal ligaments of the aged and control animals both in terms of numbers of fibers per 50 microns and in terms of area of tissue occupied. Thus, in contrast to the apparent lack of age changes so far determined for the extracellular matrix of the periodontal ligament (collagen fibrils and oxytalan), the periodontal fibroblasts exhibit some age changes as perceived at the ultrastructural level.