Conclusions
Development
A carious lesion should be regarded as damage resulting from the infectious disease dental caries. The coronal lesion starts as clinically undetectable demineralization of enamel, visible only at the microscopic level, and proceeds gradually to visible, noncavitated demineralization of first the enamel surface and then the dentin, and finally to cavitation of the dentin. Primary carious lesions are most frequently located supragingivally on the crowns and particularly on the occlusal surfaces of the molars and the approximal surfaces of the posterior teeth. Root caries may occur in elderly people and other adult caries-risk patients with root surfaces exposed by periodontal disease.
Carious lesions may be classified according to type (primary or secondary caries), location (crown, root, and surfaces), size and depth (enamel, dentin, or root cementum), and shape (noncavitated, smooth, rough or soft surface, cavitation, etc).
From a treatment needs aspect, it is important to evaluate whether the lesions are active or inactive and noncavitated or cavitated.
Enamel lesions develop mainly where cariogenic plaque accumulates and remains undisturbed for lengthy periods. This plaque, together with accessible fermentable carbohydrates, results in prolonged periods of low pH. In toothbrushing populations, these conditions occur most frequently on the approximal surfaces of the posterior teeth (particularly from the mesial surfaces of the second molars to the distal surfaces of the second premolars) and the occlusal surfaces of erupting molars (particularly the distal fossae).
Moderate pH levels result in a noncavitated enamel lesion with a surface zone that is like a micropore filter, and a so-called lesion body where there is greater loss of minerals from every single enamel prism. Such a noncavitated lesion can be arrested without any loss of surface minerals. At very low pH (4.5 to 5.0), an erosive-like enamel lesion will develop with intraprismatic dissolution of the enamel with microcavities. Such a lesion can also be arrested, but with some loss of the enamel surface compared with the surrounding intact enamel. In other words, all noncavitated
as well as more active erosive-like enamel lesions should be diagnosed as early as possible and arrested to prevent extension of the lesion into the dentin, with eventual cavitation, which would generally require operative intervention.
In populations with low or moderate caries prevalence and access to well-organized preventive programs, most enamel lesions will be arrested and therefore never progress into the dentin. On the other hand, in highly caries-active individuals with poor oral hygiene and no daily use of fluoride, enamel lesions can progress to cavitation of the dentin very rapidly (within 6 to 12 months). The demineralization of the dentin at the dentinoenamel junction corresponds to the width of the outer surface of the enamel lesion and progresses in the same direction as the dentinal tubules. Very advanced demineralization of the dentin may occur without enamel cavitation; under such conditions there is no microbial invasion of the dentinal tubules. All noncavitated lesions of dentin can and should, therefore, be arrested and not be treated invasively.
Root caries develops only on root surfaces that are accessible to cariogenic microflora and exposed to the cariogenic plaque (biofilms). The primary lesions develop predominantly at plaque-retentive areas, particularly in the large interproximal areas and along the gingival margin and the cementoenamel junction. These represent stagnant areas where plaque accumulates. The primary root lesion has greater horizontal than vertical dimensions because of the greater thickness of supragingival plaque along the gingivocervical margin. If the exposed root surface is still covered
by a layer of cementum, the early stages in caries development involve a haphazard demineralization of this layer, because of acid formation by the acidogenic bacteria colonizing the root surface. Such initial lesions result in a soft, yellow, but noncavitated root surface that can be arrested.
However, where root cementum has been removed in patches as an iatrogenic effect of aggressive scaling and root planing, the exposed root dentin may be destroyed very rapidly; cavity formation is a combined effect of acidogenic microorganisms and collagenase-producing microorganisms.
Even cavitated active root lesions can be converted to nonactive brown-black lesions by improved plaque control and use of fluoride. Restoration of such arrested lesions may still be indicated, however, not only to prevent plaque retention, but also to improve esthetics.
Diagnosis
For several decades, the accepted method for detecting carious lesions in patients, as well as in clinical trials, has been a combination of clinical visual-tactile (light, mirror, and probing) examination and bitewing radiographs. For most patients, these techniques are still appropriate. However, over the last decade there has been a considerable increase in materials and methods available for this purpose:
1. The visual method, still used by many general practictioners
2. The visual-tactile method with light, mirror, and gentle probing
3. The conventional visual method in use in European epidemiologic surveys
4. The meticulous clinical visual method based on mechanical cleaning and drying of
the tooth surfaces before examination
5. The visual method with temporary elective tooth separation
6. The visual method with temporary elective tooth separation and the use of
elastomeric impression material for evaluation of the size and depth of cavitated
lesions
7. The conventional (bitewing) radiographic technique
8. The digital radiographic method, which minimizes radiation exposure compared to
conventional radiographs
9. The computer-aided radiographic method, which utilizes the measurement potential
of computers in assessing and recording lesion size
10. The fiber-optic transillumination method (FOTI)
11. The electric conductance (fixed frequency) method
12. The endoscopic filtered fluorescence method (EFF)
13. The alternating current impedance spectroscopic technique (ACIST)
14. The quantitative laser (light) fluorescence method (QLF)
The accuracy (sensitivity and specificity) and applicability of these methods vary
considerably. Some, eg, the visual-tactile and European methods, are very rapid and
inexpensive, but subjective, and are therefore useful for large-scale epidemiologic
surveys. Others are objective and offer quantitative diagnosis but are very time
consuming and require costly equipment (ACIST, EFF, and QLF), and to date are
being applied only in limited research projects.
The diagnostic method of choice depends on the purpose of the examination. Apart
from the occult fissure lesion penetrating deeply into the dentin, difficulties in clinical
detection and registration arise not with the advanced lesion but primarily with the
early lesion (confined to the outer enamel), the noncavitated lesion of dentin,
recurrent caries (around the margins of restorations), and subgingival root caries.
The general trend in clinical examination is away from reliance on gentle probing
with a sharp explorer, toward meticulous visual inspection (sharp eyes and a blunt
probe) for early detection of noncavitated lesions: Treatment is directed toward
arresting the lesion and preserving the surface zone, to prevent the initiation of
cavitation.
In general practice, the aforementioned method, in combination with radiographs
(conventional bitewings or digital) and FOTI should be adequate for diagnosis of
carious lesions in patients. Temporary elective tooth separation should be used to
determine whether posterior approximal lesions of dentin are noncavitated or
cavitated.
For diagnosis of occlusal caries, probing offers no advantage in accuracy over visual
inspection after mechanical cleaning and drying. Noncavitated active enamel lesions
should be detectable as white spots on either side of the entrance of the fissures or
pits. However, even noncavitated lesions of dentin occur frequently.
Conventional bitewing radiographs improve the potential for detecting both
noncavitated and cavitated occlusal lesions of dentin. However, there is some risk of
false-positive diagnoses.
A new aid, Diagnodent, based on QLF technique, appears to be advantageous for
detection of occlusal enamel as well as dentin caries lesions.
All noncavitated occlusal lesions, in enamel as well as in dentin, can be arrested by
plaque control and fluoride or treated with noninvasive methods such as fissure
sealants. In a radiographically detected lesion of dentin, or by QLF aid, explorative
opening of the entrance to the fissures may be indicated, to allow direct visual
inspection of possible cavitation through the base of the fissure into the dentin. In the
absence of cavitation, the fissure should be sealed with a fluoride-releasing material
(resin-based glass-ionomer materials or compomers).
Of the recent innovations, the QLF technique followed by the electrical conductance
(fixed frequency) method seems to be the most promising for diagnosis of occlusal
lesions of enamel as well as dentin.
In the anterior teeth, approximal lesions of enamel and dentin, noncavitated as well as
cavitated, are readily detectable by a combination of meticulous clinical visual
examination and FOTI. In the posterior teeth, radiographs (bitewings, digital, or
computer aided) are excellent for detection of approximal lesions in enamel and
dentin, as well as for monitoring progression, arrest, or regression. In this area,
meticulous clinical examination is of limited value in the detection of early lesions.
However, neither radiography nor meticulous clinical examination is useful for
differentiating between cavitated and noncavitated approximal lesions of dentin.
Temporary elective tooth separation is therefore recommended; for visual inspection
with or without a pouring of an impression for future reference. Studies have found no
dentin cavitation in the majority of radiographically detected lesions in the outer half
of the dentin. Such lesions should be arrested rather than restored.
For differential diagnosis and for assessment of treatment needs, root caries should be
classified as active or nonactive and noncavitated or cavitated. This can usually be
done by meticulous clinical examination. A rough, soft plaque-covered surface and
yellow color indicate an active lesion, while a smooth, dark brown or black surface
that is hard to moderate probing pressure indicates an inactive (arrested) lesion.
Cavity formation may be associated with both active and nonactive lesions, but in the
latter the margins appear smooth. On the buccal and lingual surfaces, meticulous
clinical examination should be adequate for diagnosis according to the
aforementioned criteria. Probing with a sharp explorer is contraindicated.
The most difficult type of root lesion to diagnose is located subgingivally on
approximal surfaces. Meticulous clinical examination should be supplemented by
vertical (standing) bitewing radiographs.
As with active enamel lesions, the initial treatment of active root lesions should be
preventive and noninvasive (improved plaque control and use of fluoride), aimed at
arresting the lesion and converting it from active to inactive.
The major emphasis is on the early detection of the noncavitated active lesion.
Treatment is preventive and needs related, aimed at arresting the lesion as soon as
possible. Because the arrested lesion does not progress to cavity formation, there is no
indication for operative intervention (for reviews on the development of carious
lesions, see Thylstrup et al, 1994; Thylstrup and Fejerskov, 1994; for reviews on
diagnosis of carious lesions, see Grondahl, 1994; Ismail, 1997; Pitts, 1997).
