Conventional Xrays Rx

Clinical inspection is completed by radiological evaluation. Bitewing X-rays represent the technique of choice for diagnosing proximal surface caries, though they may also be useful for diagnosing occlusal dentin caries (Tran^us et al., 2005; Wenzel et al., 1992). At occlusal level, the X-rays register a tooth thickness beyond the proximal zone, and the lesions are masked by the healthy tissues for a longer period of time (Wenzel et al., 1992). For this reason, from the histological perspective, the lesion is more advanced than suggested by its radiological appearance - a fact that justifies the low sensitivity of the technique. In our studies, the observed sensitivity was 0.57 (Guerrero, 2011), i.e., many existing lesions are not detected. Nevertheless, once again, the specificity is very high. These results imply that negative X-ray findings cannot be taken to rule out dentin caries, though a positive X-ray diagnosis should be taken as an indication for opening the fissure and providing caries treatment. The reviewed in vivo and in vitro studies (Wenzel et al., 1992, Lussi, 1993; Angnes et al., 2005; Lussi et al., 2001; Ashley et al., 1998; Costa et al., 2008) point to low sensitivity and high specificity, in coincidence with our own results (Table 2). Only studies involving third molars report lesser specificity, possibly due to the difficulty of correctly obtaining X-ray projections in this zone.

AUTHOR

LEVEL

STUDY

SENSITIVITY

SPECIFICITY

Ashley 1998

enamel

in vitro

0.19

0.80

Wenzel 1990

enamel

in vitro

0.44

0.70

Ricketts 1997

dentin

in vitro

0.14

0.95

Ashley 1998

dentin

in vitro

0.24

0.89

Wenzel 1992

dentin

in vitro

0.48

0.81

Lussi 2001

dentin

in vivo

0.63

0.99

Heinrich 2002

dentin

in vivo

0.70

0.96

Angnes 2005

dentin

in vivo

0.0 - 0.06

0.98 - 0.96

Costa 2008

dentin

in vivo

0.26

0.94

Table 2. Sensitivity and specificity values for the X-ray diagnostic evaluation of occlusal caries.

Table 2. Sensitivity and specificity values for the X-ray diagnostic evaluation of occlusal caries.

The main difficulty of conventional X-ray exploration is the distinction between deep enamel and superficial dentin, due to superpositioning of the healthy vestibular and lingual enamel, which masks the radiotransparency, particularly in early-stage lesions. Carious lesions normally cannot be detected on X-rays until they have extended about 0.5 mm beyond the amelodentinal junction (Kidd et al., 1993). Even with this difficulty, however, in vitro studies point to acceptable correlation with the existing histological condition. In this context, Wenzel (Wenzel, 1998) suggested that the in vitro diagnostic performance may be better than in the actual clinical setting, i.e., the results obtained in the laboratory may be overestimated. However, other in vitro studies indicate that by the time occlusal caries have been identified on the X-rays, demineralization has already extended to the middle third of the dentinal layer, i.e., the deep dentin (Ricketts et al., 1997). Weerheijm (Weerheijm et al., 1992) reported that X-rays are not very effective for diagnosing incipient enamel caries, though the technique is very useful for diagnosing deeper lesions. In this context, conventional X-rays improve the diagnostic capacity of VI by 11%, and moreover help assess the extent of the lesion (Ekstrand et al., 1995).

Regarding the predictive value of the technique, our group (Guerrero, 2011) has recorded a PPV of 100%, suggesting that a positive diagnosis implies the existence of caries, since false-positive interpretations are very unlikely. In turn, we recorded a NPV of 59%, i.e., normal X-ray findings do not discard the possibility that an occlusal lesion may have invaded dentin. In relation to the inter-examiner reproducibility of the technique, the results are varied and range from kappa index (k) values of 0.39 (weak concordance) to 0.95 (near-perfect concordance) (Angnes et al., 2005; Costa et al., 2008; Cortes et al., 2000) - though most studies report substantial concordance values (0.61-0.80).

In sum, bitewing X-rays are an obligate diagnostic tool for proximal surface caries and represent a good adjunct in the diagnosis of occlusal caries. Considering that VI results in an important percentage of undetected clinical lesions (Wolwacz et al., 2004), particularly in adolescents (Wenzel et al., 1992), the bitewing X-rays must be carefully evaluated for possible lesions beneath the occlusal enamel. Figure 4 shows caries in dentin with a non-cavitated occlusal surface. However, a normal X-ray study does not rule out the presence of hidden dentin caries, in view of the low sensitivity and NPV of the technique.

tr* SSi

Fig. 4. Hidden dentin caries diagnosed from bitewing X-rays (A: dentin caries, B: early dentin caries)

0 0

Post a comment