Age-induced changes in the teeth and their attachment apparatus.

Both the hard substances and the soft tissues of the teeth and their attachment apparatus are subject to constant change. This begins immediately after eruption and continues throughout life. An exact dividing line between changes which are physiological and pathological cannot always be drawn. Enamel undergoes attrition, and in addition its mechanical characteristics alter, owing probably to changes in diffusion conditions. The age-induced changes occurring in dentine are much more obvious, the biological properties of this hard substance being fundamentally altered. The dentine of older people is characterized by the continuous narrowing of the lumen of the dentinal tubule, increasing calcification, reduction in the amount of peritubular fluid and reduced sensitivity. In this process, dentine becomes able to assume the function of enamel as it wears. With age cementum undergoes continuous deposition, mainly functionally induced. It is evident, even macroscopically, that the volume of the pulp declines owing to the deposition of secondary dentine or of amorphous dentine with age. Histologically, young pulp differs fundamentally from that of the pulp of an older person. Regressive processes commence immediately after tooth eruption. The number, nature, properties and capabilities of the cells change, but the pulp does not suffer any appreciable loss of vitality. Circulation in the pulp is affected by deposition of hard substance in the apical part of the root canal. These processes are important in endodontics, and because of them different treatment methods have to be used for patients of different ages. The tooth supporting tissues are also subject to constant rearrangements, the physiological occlusal and mesial movements of the teeth being relevant here. All these structural and biological differences must be allowed for when therapy is being considered. They have not hitherto been taken sufficiently into account.