Caries Management - Science and Clinical Practice. Группа авторов

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      Changes in Teeth and Saliva with Aging

      Most tissues in the human body have a physiological turnover of their components. The rate of turnover varies from tissue to tissue; in the pulp tissue the turnover is considered to be high, while it is limited for the dentin and cementum. Tooth enamel is a tissue with no biological turnover after it is formed. Alteration of enamel during a lifetime is thus physico-chemically related. Wear will cause loss of incisal protuberances, perikymata, and imbrication lines resulting in a flattening of the teeth with age (cf. Fig. 1.14a,b). At the crystal level, old enamel has a higher content of fluoride,³⁰ the reason for which will be covered in Chapters 2 and 12.

      Fig. 1.14a,b Dentition of a young (a) and old (b) person. Wear is a natural aging process that only turns pathologic if it is excessive for the respective age and results in clinical symptoms.

      At least two age-dependent changes take place in the dentin; namely physiological dentin formation and gradual obturation of the dental tubules. The former is referred to as secondary dentin formation, to differentiate it from primary dentin formation which occurs until the tooth is fully formed, while the latter is referred to as dentin, or tubular sclerosis. The changes in the dentin during a lifetime have some clinical and cosmetic implications³¹; thus the diminishing size of the pulp chamber due to the secondary dentin formation may prevent pulp reaction and pulp exposure, but may also complicate pulp treatment. Tubular sclerosis results in a reduction in the sensitivity and permeability of dentin, although the latter may prevent ingress of toxic agents deeper into the dentin. The sum effect of changes in the dentin (condensation) influences the color of the teeth, thus owing to the translucence of the enamel, the color of older teeth is more yellow than younger teeth (Fig. 1.14b).

      The most striking age-related change in the cementum is that its width nearly triples with age. To the best knowledge of the authors this has no clinical implication.

      The pulp changes with age—in general from a cell-rich and fiber-poor tissue to a cell-poor and fiber-rich tissue.³¹ These changes are important from a clinical point of view, as the reactivity of an old pulp is different from the young one. This must be taken into consideration when choosing between different treatment options.

      As described above, more than 99% of saliva is water, thus less than 1% is electrolytes and organic components. What happens to these components with age? Most data^32,33 indicate that there are changes in the structure of the salivary glands due to age, but it seems that these changes are not sufficient to significantly influence the three components (water, electrolytes, and organics) in such a way that the tendency for developing caries increases. Instead of relating the increasing prevalence and incidence of caries seen in elderly people to age-related disorders of the salivary glands, we should rather consider age as a possible contributory factor to increasing patient vulnerability.³³

      Dental professionals should be able to differentiate between signs of natural aging/wear and signs of pathological processes. However, it should be kept in mind that the transition between “natural aging” and “disease” is mostly fluid, and the definition of what is “disease” is often controversial.