Conventional bitewing radiographic method
Several factors have contributed to the general adoption of radiographic examination as an aid to the detection and subsequent treatment of caries:
1. It discloses sites inaccessible to other diagnostic methods. Radiography facilitates detection of carious lesions at an earlier, potentially reversible stage. Usually, more approximal and occlusal lesions are recorded when clinical examinations are supplemented by radiography.
2. The depth of the lesion can be evaluated and scored, eg, by the radiographic index by Grondahl et al (1977), modified from Moller and Poulsen (1973): 0 = no radiographic changes in enamel; 1 = radiographic changes in enamel; 2 = radiolucency extending to the dentinoenamel junction; 3 = radiolucency penetrating approximately halfway through dentin; and 4 = radiolucency close to the pulp.
3. Because the radiograph provides a permanent record, recall examinations allow assessment of progression or regression of lesions, evaluation of disease activity, and the efficacy of preventive and therapeutic measures.
4. Radiography is noninvasive, whereas gentle probing may cause iatrogenic damage to the surface of noncavitated enamel and dentin lesions.
Radiographs have, however, some limitations:
1. For accurate reproducibility, standardized geometric angulation, exposure time, processing procedures, and analyzing facilities are necessary. A bitewing film holder fixed to a radiographic long cone facilitates standardized geometric angulation.
2. Radiography does not disclose the earliest stages of lesion development.
3. Radiography does not unequivocally distinguish among approximal surfaces that are sound, have subsurface lesions, or are cavitated.
4. To some degree, radiographs underestimate the extent of demineralization, but overestimations may also occur, as a result of projection errors.
5. Radiographic diagnosis is subjective, and the interpretation of radiographic findings is subject to interobserver and intraobserver variation.
6. Approximal secondary caries on the more apical part of a restoration may not be detected.
7. Noncavitated carious lesions on the root are difficult to diagnose.
There is a wealth of data relating to conventional radiographic techniques that are used in general practice, research, and clinical trials, but studies predating the recent changes in the pattern of the disease process should be extrapolated with caution to present conditions.
Radiographic results are best considered by site. For approximal surfaces, recent studies show moderate levels of sensitivity at the D1 threshold, disclosing many more relatively small approximal lesions that may be amenable to preventive care than are disclosed by most other techniques. Specificity is generally high, although not quite as high as for the clinical methods. At the D3 threshold, sensitivity is also moderate and specificity is high. For occlusal surfaces, newer findings have changed perceptions of performance and the applicability of radiographic methods (for review, see Pitts, 1997).
While the intrinsic image geometry of the bitewing projection, with superimposition of large volumes of sound enamel, precludes sensitive radiographic diagnosis of enamel lesions, the method is now highly applicable, with moderate sensitivity, for detecting extensive dentinal lesions which may be undetected at clinical examination.
