Caries Management - Science and Clinical Practice. Группа авторов

How does the caries lesion manifest using different investigative methods—for example, light microscopy, scanning electron microscopy, microradiography (mineral content), hardness testing and fluorescence?

      • Caries is a dynamic process—how can caries activity be recognized?

      • Where are the bacteria within a caries lesion?

      • Can the caries process be stopped and dental hard tissue even be remineralized?

      • Dental erosion—not caries, but also destructive to the dentition.

      Enamel Caries

      Location in the Teeth

      Since it is caused by acids produced from a biofilm covering the tooth surface, carious dissolution of dental hard tissue (i.e., enamel, dentin, and cementum) always starts on a tooth's surface, which is accessible to the oral environment. Clinically, this may be at the enamel surface, root cementum, or exposed dentin. For simplicity we look first at caries affecting the enamel layer only, and then follow the histological and clinical appearance of the caries process as it penetrates deeper into the tooth. As observed clinically, caries most often develops at typical anatomical sites of the teeth, the plaque stagnation areas (Fig. 3.1; see also Chapter 1). Caries in pits and fissures is typical for younger people. Caries at interproximal surfaces and at the gingival margin, particularly when root cementum and dentin are exposed, is typical for older patients. These caries predilection sites all facilitate plaque accumulation, because there is some local protection from mechanical cleaning, notably from tongue and cheek movements, and from toothbrushing. Although caries lesions develop predominantly at specific sites, the specific properties of the overlying biofilm (Figs. 3.1a and 3.2) are largely responsible for determining whether or not caries will develop, rather than specific properties of the enamel itself (Fig. 3.1f; see also Chapter 2). In principle, the fundamental processes of caries development act the same way, irrespective of the location. Every caries process in enamel starts with slight “etching” of the surface (Fig. 3.3a) under a layer of dental plaque.¹ It can be assumed that this process occurs frequently under almost any plaque-covered area and starts as soon as the plaque fluid becomes undersaturated with respect to any enamel mineral present (Chapter 2). At a very early stage, the “etching” is reversible. Only under cariogenic circumstances does the dissolution process progress, leaving micro-porosities at the enamel surface (Fig. 3.3) that start to extend deeper into the enamel (Fig. 3.4). These micro-porosities are typically located at the prism boundaries and, with further progression, within the prism cores (Chapters 1 and 2).

      Fig. 3.1a–g Caries lesions start developing at plaque stagnation areas.

      a,b Plaque accumulation in the fossae of an upper molar tooth (a). After cleaning, this tooth shows a deep (distal) and less developed (central) caries lesion (b).

      c,d Interproximal (approximal) plaque accumulation has led to caries development below the contact point of a lower molar tooth, which cannot easily be seen by visual examination (c) but extends well into dentin as can be seen during operative treatment (d).

      e–g It is not the properties of enamel or dentin tissue of the site itself that facilitates caries development, but plaque accumulation, as can be seen at a rotated lower molar tooth (e) with deep interproximal caries at an unusual site (f). Caries at the cervical region of an upper canine tooth (g).

      Fig. 3.2a,b Plaque accumulation at interproximal (approximal) and cervical regions, which already has caused cervical caries.

      a Small amounts of plaque with cervical caries beginning underneath (young patient).

      b Interproximal and cervical plaque deposition with cervical caries at several teeth (older patient suffering from hyposalivation). Note: gingivitis following plaque accumulation at the gingival margin.

      Fig. 3.3a–c SEM images of an interproximal (approximal) site of a molar tooth following extraction and vigorous ultrasonication in NaOCl solution to remove the dental plaque without damaging the surface.

      a The border of an early caries lesion (indicated by black arrows) separates sound enamel (left side) from etched, slightly demineralized enamel.

      b Surface porosities scattered along the perikymata.

      c Quite often a honeycomblike structure is revealed, indicating a preferred dissolution pattern.

      Fig. 3.4 SEM image from a micropore surrounded by enamel of low porosity (intact surface layer). The micropore extends several micrometers into the enamel. Such micropores are often the entrance into channels that extend several hundred micrometers into the enamel.

      Fig. 3.5 Cervical white spot lesion of a lower canine following removal of the overlying plaque and brief air-drying. Note the dull, matt appearance indicating an active lesion. The cervical caries lesion of the premolar has already developed further including breakdown of the cervical enamel layer. The blood pooling at the gingival margin of the canine is due to tooth cleaning before taking the photograph, indicating gingivitis in this area.

      Fig. 3.6 Interproximal (approximal) white spot lesion with central brownish discoloration that became visible during preparation of the neighboring tooth. The oblong shape is typical for interproximal white spot lesions.

      Fig. 3.7 Band-shaped white spot lesions of lower premolars parallel to, but distinctly above the gingival crest. These lesions must have developed at an earlier age when the patient's teeth were not fully erupted.

       NOTE

      Caries lesions begin to form at