Caries Management - Science and Clinical Practice. Группа авторов

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      Activity of White and Brown Spot Lesions

      When located interproximally, natural white spot lesions typically appear as oblong shapes below or around the contact point, where they cannot be viewed directly under normal conditions (Fig. 3.6). When located at the vestibular or oral aspect of the tooth just above the gingival margin, they are spread out in a line. In some instances, a whitish, sometimes discolored band can be found parallel to, but at some distance from, the gingival margin in teeth of the permanent dentition (Fig. 3.7). In this case, most likely, the lesion has developed when the tooth was not fully erupted, which also is a period during which tooth cleaning is often neglected. Following complete eruption, the local ecosystem may have changed due to better cleaning, which is why the demineralized band stabilizes, remaining an inactive white spot lesion, sometimes turning into a brown spot.

      Fig. 3.8 Section through an interproximal (approximal) caries lesion exposed by operative treatment procedures. The enamel caries (arrow) is typically cone-shaped in appearance.

      Fig. 3.9 Histological section through the crown of a premolar tooth with fissure caries without cavitation viewed by reflected light microscopy. Lesion development follows the prism orientation, leading to the shape of an inverted cone (“butterfly”). The deepest demineralization of this long fissure occurred at the fissure entrance, most likely due to a better nutritional situation for the plaque bacteria at this site.

      When located occlusally, white spot caries lesions develop locally in particular in the fossa areas and grooves (Chapter 1).^5–7 Quite often white spot lesions incorporate exogenous pigments from food, which adds a brownish tint (brown spot lesion). It is believed that exogenous pigments are incorporated with time, indicating that brown spot lesions have existed for longer already than white spot lesions. This would mean that brown discoloration is a sign of slow progression or low activity. Certainly, the pigmentation of white spot lesions relies on several factors like nutritional habits, surface porosity, and so on. In some instances, white spot lesions remain white for many years and therefore it cannot be assumed that the absence of brown discoloration in enamel lesions is a sign of high caries activity and fast progression.

      A more reliable marker for lesion activity is the appearance of the surface of a white spot lesion following removal of the biofilm. While active lesions are in a state of nett loss of minerals, they have more porosities at the surface than lesions that are not active. Therefore, an active white spot lesion shows a matt, dull surface, while an inactive lesion presents a shiny surface.^1,8 White spot lesions that are not covered by plaque are clinically almost certainly shiny and inactive, mainly due to incorporation of minerals (remineralization), and abrasion and polishing related to plaque removal.¹

      Lesion progression of white spot lesions within enamel roughly follows the rod/prism direction. The three-dimensional morphology of small white spot lesions on the approximal surface resembles a cone with its base at the enamel surface and its tip toward the enamel–dentin junction (EDJ) (Fig. 3.8). The three-dimensional morphology of the occlusal fissure lesion is with the tip at the surface and the base toward the EDJ due to the directions of the prisms in the fissure area (Fig. 3.9).

       NOTE

      The first clinically visible sign of caries-affected enamel is the white spot lesion, which can be as deep as several hundred micrometers. This lesion is composed of a porous body covered by a well-mineralized surface zone. The appearance and porosity of this surface layer is influenced by the lesion activity. Lesion development follows the direction of the enamel prisms.