Diagnosis of root caries
Definition and classification
Root caries usually appears as a shallow area, less than 2 mm deep, a mostly noncavitated, ill-defined, softened, and often discolored lesion, characterized by destruction of cementum and penetration of dentin. Several definitions and classifications have been proposed; Hix and O'Leary (1976) defined root caries as "a cavitation or softened area in the root surface which might or might not involve adjacent enamel or existing restorations (primary and recurrent lesions)."
Billings (1986) proposed the classification presented in Box 20, based on four grades of severity: incipient; shallow surface defect (less than 0.5 mm deep), some pigmentation; deep lesions (more than 0.5 mm deep) with cavitation; and pulpal involvement.
Nyvad and Fejerskov (1982, 1987) proposed differentiation between active and inactive lesions, using the following criteria:
1. Active root surface lesion. Any area that is well-defined and shows a yellowish or light brown discoloration. The lesion is most likely covered by visible plaque and/or presents a softening or a leathery consistency on probing with moderate pressure (Fig 225).
2. Inactive (arrested) root surface lesion. Any root surface area that shows a welldefined, dark brown or black discoloration. The surface of the lesion is smooth and shiny and appears hard on probing with moderate pressure (Fig 226).
Figure 226 illustrates how the active lesion in Fig 225 has been arrested and inactived by improved plaque control and use of fluoride toothpaste (Nyvad and Fejerskov, 1986). Both active and inactive lesions may exhibit cavitation, but in the latter the margins are smooth (see Fig 226).
Root caries may be classified as primary or secondary, cementum or dentin, active or inactive, with or without cavitation. The lesions can also be classified according to the texture: soft, leathery, or hard, and the color: yellow, light brown, dark brown, or black (see Table 15). When root surfaces are exposed to the oral environment as a result of gingival recession, the areas of potential plaque retention increase, particularly in the large interproximal areas and along the cementoenamel junctions.
The primary carious lesion of the root has a greater horizontal than vertical dimension because of the greater thickness of supragingival plaque along the gingivocervical margin. Initial active root lesions are soft on probing, have a leathery consistency, and are normally covered with plaque. The color is yellow or light brown but, with longer exposure to the oral environment, changes to dark brown and black. This change results from extrinsic factors, such as staining from dietary components and smoking, and possibly from chromogenic bacteria present in the lesion.
Figure 227 illustrates various root lesions.
Diagnostic methods
The problems associated with diagnosis of root caries are somewhat different from those associated with coronal caries. On the buccal and lingual surfaces, meticulous clinical visual examination will be sufficient for differential diagnosis of a lesion as cavitated or noncavitated or active or inactive, according to the aforementioned criteria. In borderline cases between inactive and active lesions, the texture of the surface (soft, leathery, or hard) is more important than the color (yellow, tan, brown, dark brown, or black). Lynch and Beighton (1994) reported that, irrespective of color, soft lesions are closest to the gingival margin, and hard lesions are the most distant;
leathery lesions occupy an intermediate position.
For clinical examination, sharp eyes and a blunt probe are recommended, and even
gentle probing with a sharp explorer is contraindicated
The most difficult type of lesion to diagnose is on approximal surfaces where there
has been loss of attachment but no recession¾in other words, lesions within deep
periodontal pockets that are hidden from view. Vertical (standing) bitewing
radiographs are essential for diagnosis. These lesions appear to progress more rapidly
than enamel lesions, and failure to detect them at an early stage may result not only in
pulpal involvement but also in a tooth that cannot be treated endodontically.
Clinicians are cautioned to differentiate such true carious lesions from cervical
radiolucency, which appears as a dark shadow on approximal root surfaces as a result
of the contrast between adjacent parts of the image.
Treatment
As with active enamel lesions, treatment of active root caries initially should be
preventive and noninvasive and directed toward arresting and converting the lesion
from active to inactive. As shown in the study by Nyvad and Fejerskov (1986),
discussed earlier, it is possible to arrest even cavitated carious lesions of the root
simply by improving mechanical plaque control by self-care and instituting the use of
fluoride toothpaste (see Figs 187, 188, 189 and 227 (c and f)). Repeated PMTC in
combination with, for example, slow-release chlorhexidine and fluoride varnish
further improves the potential for arresting active root lesions.
However, restoration of black, cavitated, but inactive root lesions may be indicated,
not only because of plaque retention but also for esthetics. The restorative materials of
choice are tooth-colored, fluoride-releasing materials such as glass-ionomer materials,
resin-based glass-ionomer materials, or compomers.
