Further reading
3.5.3 Approximal surfaces 2 Clinical-visual examination
good but it can be confused by staining and calculus, giving high readings when active caries is not present. Whether this machine will become a helpful tool in the diagnosis of occlusal caries when used by general practi- tioners has yet to be established. In the meantime, its readings should be interpreted with caution and combined with a conventional clinical-visual and radiographic examination.
3.5.3 Approximal surfaces
2Tactile examination (careful!)
A sharp, curved probe (Briault) can be used gently to try to determine whe- ther an approximal lesion is cavitated, but if this instrument or a scaler is used in a heavy-handed manner, it can actually cause cavitation.
Bitewing radiography
The bitewing radiograph is of paramount importance in the diagnosis of the approximal carious lesion (Figure 3.9), although it should be remembered that the technique is relatively insensitive as it is not able to detect early sub- surface demineralization. As shown diagrammatically in Figure 3.10, the approximal enamel lesion appears as a dark triangular area in the enamel of the bitewing radiograph. The lesion may be in the outer enamel or be seen throughout the depth of the enamel. Larger lesions can be seen as a radio- lucency in the enamel and outer half of the dentine or a radiolucency in the enamel reaching to the inner half of the dentine. The pulp is often exposed by the carious process in this latter instance.
While the bitewing radiograph can detect demineralization, it cannot diagnose lesion activity. A series of radiographs taken over time are required to confirm the arrest or progression of lesions. It is essential that these views are geometrically comparable and the only reliable way to achieve this is to use film holders and beam-aiming devices (Figure 3.3).
Cavitated lesions are likely to be active because of the difficulty of remov- ing plaque from the hole when an adjacent tooth is present. The presence or absence of a cavity cannot be judged from a radiograph but, referring
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Figure 3.9. A bitewing radiograph showing caries in enamel and dentine on the mesial aspect of the upper first molar. A lesion is also visible on the mesial aspect of the lower first premolar.
to Figure 3.10, appearances graded 0–2 are unlikely to be cavitated, while grade 4 will almost certainly be cavitated. The problem comes with grade 3 which may or may not be cavitated. The dentist may wish to separate the teeth to determine whether a cavity is present and this technique is described on page 55.
Caries on the approximal root surface is also visible on a bitewing radio- graph (Figure 3.11) although this appearance is sometimes confused with the cervical radiolucency. The latter is a perfectly normal appearance caused by the absence of the dense enamel cap at the enamel–cement junction and the absence of the interdental alveolar bone. Fortunately, root caries is
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Figure 3.10. Diagrammatic representations of caries on bitewing radiographs.
visible clinically and a careful clinical re-examination will usually sort out any confusion.
It will be obvious that if it is to be of value, bitewing radiography must be carried out carefully. Overlapping contact points obscure what the clini- cian is trying to see and unfortunately, slight difference in angulation of the film or X-ray beam will affect what is seen on the resultant radiograph. Thus radiographs should be as reproducible as possible, using film holders with beam-aiming devices (Figure 3.3) and standardizing exposure time and dose.
This is particularly important when the dentist is going to monitor lesions on radiographs over time to look for progression or arrest of lesions. In addi- tion, films should be read dry, mounted, and under standardized lighting conditions.
Transmitted light
Transmitted light can also be of considerable assistance in the diagnosis of approximal caries. This technique consists of shining light through the contact point. A carious lesion has a lowered index of light transmission and therefore appears as a dark shadow that follows the outline of the decay through the dentine. The technique has been used for many years in the diagnosis of approximal lesions in anterior teeth. Light is reflected through the teeth using the dental mirror and carious lesions are readily seen in the mirror (Figure 3.12).
In posterior teeth a stronger light source is required and fibreoptic lights, with the beam reduced to 0.5 mm in diameter, have been used (Figure 3.13).
It is important that the diameter of the light source is small so that glare
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Figure 3.11. A bitewing radiograph showing root caries on the distal aspect of the first upper molar. This tooth has over-erupted following loss of the lower first molar.
and loss of surface detail are eliminated. The technique is called fibreoptic transillumination(FOTI). It has particular advantages in patients with posterior crowding where bitewing radiographs will produce overlapping images and in pregnant women where unnecessary radiation should be avoided.
Tooth separation
One further technique to assist with the diagnosis of approximal caries is the use of tooth separation. This technique has been borrowed from the ortho-
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Figure 3.12. A mirror view of the palatal aspect of the upper anterior teeth.
Lesions are visible mesially and distally on the upper right central incisor.
Figure 3.13. Use of a fibreoptic light in the diagnosis of approximal caries.
(By courtesy of Professor C. Pine.)
dontists who have used it for years to separate teeth before placing bands around them. A small round elastic is forced between the contact points using a special pair of applicating forceps (Figure 3.14a). After a few days the teeth are separated (Figure 3.14b). The dentist can now feel, very gently, with a probe to detect whether a cavity is present. Alternatively, a little elastomer impression material can be injected between the teeth(Figure 3.14c). After a few minutes the set material can be removed with a probe and the impression examined to see whether there is a cavity (Figure 3.14d).