Caries Management - Science and Clinical Practice. Группа авторов

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      Caries of the Exposed Root

      Caries of the exposed root has shown increased prevalence over the past few years, particularly among the elderly.⁶⁴ Development of root caries relies on the exposure of root areas, mostly due to gingival recession, and the accumulation of plaque (Fig. 3.22). With regard to plaque accumulation, the development of root caries is not so much different from caries development at other sites, e.g., interproximal, occlusal, and smooth surfaces. The cementum layer may cover the outer surface of the exposed root. This layer can be removed with time by toothbrushing or dental therapeutic removal of tartar, polishing, or periodontal treatment (scaling and root planing). It is known that dentin is more vulnerable to demineralization than enamel, and the same applies to the cementum layer (see Chapter 2). In most cases root caries spreads across the cementum or dentin surface to a certain extent, while initially its depth is limited. The dentin of the root has fewer dentinal tubules than coronal dentin and it is already in a “mature” state when root caries develops, due to a history of external stimuli following root exposure, or simply age, with a high degree of sclerosis.⁶⁵ It has been observed that bacteria are already able to penetrate the cementum layer in an early state of root caries development, while bacteria penetrate into the underlying dentin at a later state of lesion development. A well-mineralized surface zone forms at the surface of the cementum or dentin (when cementum is absent). The body of the lesion underneath this mineral-rich surface zone is heavily demineralized with about 50% or less of the natural mineral content of sound dentin⁶⁶ (see Fig. 3.23). The histological layering within root dentin is similar to coronal dentin. However, a cross-section through a root caries lesion shows that root caries lesions are rather shallow, and saucer-shaped in most cases.

      Fig. 3.22a, b Cervical caries lesions of different activity from two different patients.

      a Active root caries in a lower molar of an elderly patient. The cavitated caries lesion is partly filled with plaque. The gingiva is inflamed in the area of the lesion and reaches into the cavity.

      b Arrested root caries lesion in a lower molar of a middle-aged patient. The lesion was arrested following a change in toothbrushing habits. The surface is shiny and hard and acquired a pattern of toothbrushing abrasion. The discoloration of arrested root caries lesions tends to get darker with time.

      Fig. 3.23a, b Microradiography of a carious cervical lesion of a lower molar cut just above the cemento-enamel junction.

      a Due to the severe carious circumstances the enamel layer in the area of the caries lesion has been lost. The exposed dentin shows a remineralized layer at the surface.

      b Microradiogram showing the mineral content of the cervical caries lesion along the dashed arrow in (a). The high mineral content of the mineralized zone at the surface, the low mineral content at the center of the caries lesion, and a continuous increase in mineral content toward the end of the lesion can be seen. Also, in the sound part of the microradiogram, a decrease in mineral content toward the pulp is visible.

       NOTE

      For development of root caries the same principles apply as for coronal caries, but there are a few points that facilitate the development of caries within cementum and dentin at the cemento-enamel margin. Two major factors contribute to root caries: the exposure of the cervical region in conjunction with the fact that cementum and dentin are more vulnerable to demineralization than enamel; and patient age, which is associated not only with root exposure, but also with lower salivary flow and reduced tooth-cleaning capabilities.