July 1st, 2009 by admin

It is difficult to see the white spot lesion on an approximal surface because
the lesion forms just cervical to the contact area and vision is obscured by the
adjacent tooth. The lesion is usually only discovered at a relatively late stage
when it has already progressed into dentine and is seen as a pinkish-grey
area shining up through the marginal ridge (Figure 1.3, page 5). It must be
emphasized again that the teeth should be isolated, clean, and dry to see
this.
In contrast, an approximal lesion on the root surface may be diagnosed
visually but gingival health is mandatory for such a diagnosis to be reliable.
Thus, if the gingivae are red, swollen, and tending to bleed, caries diagnosis
in these areas should be deferred until improved oral hygiene has been insti-
tuted and the in ammation is resolved.
Tactile 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
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 re ected through
the teeth using the dental mir ror and carious lesions are readily seen in the
mir ror (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
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 orthodontists 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