Fiberoptic transillumination FOTI

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Fiber-optic transillumination (FOTI) (Fig. 8) is a qualitative technique introduced in the 1970s. It is based on light transmission through an optic fiber; as the light falls upon the tooth surface, it spreads through the healthy dental tissue. In this context, caried tissue is characterized by an increased organic component, with alteration of the homogeneity of the inorganic component - thereby resulting in a loss of light transmission capacity.

Fig. 8. Fiber-optic transillumination device (DioPower Lamp)

FOTI has been used fundamentally for identifying proximal surface caries (Cortes et al., 2000;), with high specificity and a broader range of sensitivity values (Tran^us et al., 2005). The technique is of great help in diagnosing cracked tooth syndrome (Fig. 9). However, it is little used for diagnosing hidden dentin caries, where moreover few studies have assessed its diagnostic performance, precision and reproducibility.

Transillumination Test Dental
Fig. 9. Cracked tooth syndrome diagnosed by fiber-optic transillumination (FOTI).

FOTI is more specific than sensitive. Table 6 reports the validity of the test in different in vitro studies referred to occlusal caries. In an in vivo study with full sample validation, our group (Guerrero, 2011) has recorded a sensitivity of 0.47 and a specificity of 1.0. These data are in line with those reported by other in vitro studies (Ashley et al., 1998; Cortes et al., 2000).

AUTHOR

LEVEL

STUDY

SENSITIVITY

SPECIFICITY

Cortes 2000

enamel

in vitro

0.74 - 1

0.23 - 0.85

Ashley 1998

enamel

in vitro

0.21

0.95

Cortes 2000

dentin

in vitro

0.74

0.85

Ashley 1998

dentin

in vitro

0.14

0.95

Table 6. Sensitivity and specificity of FOTI in the diagnosis of occlusal non-cavitated caries.

Table 6. Sensitivity and specificity of FOTI in the diagnosis of occlusal non-cavitated caries.

As a coadjutant to visual inspection, FOTI can offer an alternative to X-rays in situations where patient irradiation is not possible. It is therefore interesting to compare both methods. In reference to occlusal caries, some authors (Wenzel et al., 1992) consider transillumination to offer better performance than conventional X-rays in detecting early-stage dentin caries. Cort├ęs (Cortes et al., 2000), in an in vitro study, reported greater sensitivity than specificity for FOTI, and superior performance with respect to X-rays, though in application to the diagnosis of enamel caries. Once caries has progressed to the dentin, FOTI proved to be significantly inferior to conventional X-rays (Guerrero, 2011). Regarding the predictive usefulness of the technique, we recorded a NPV of 54% and a PPV of 100%, without false-positive readings (Guerrero, 2011).

However, the fact that FOTI is not routinely used by dental professionals, is not recommended as a technique of choice, and is moreover supported by limited research indicates that the inconveniences which we have observed (Guerrero, 2011) - involving a large proportion of false-negative results - are probably coincident with those of other authors who have studied this technique. The main advantage of FOTI is its optimum PPV performance, which means that any positive reading is almost certainly indicative of an existing lesion.

Digitalization may represent a step forward in transillumination diagnosis. Digital FOTI (DIFOTI) makes use of the digitalized image of a tooth during transillumination, which is analyzed using specific software (Tran^us et al., 2005). The images can be filed, reproduced and studied by different examiners, and may serve to monitor the lesion. Interpretation of the image is where problems are found, however, since the results are not directly quantified by the technique. According to some authors (Pretty & Maupome, 2004; Pretty, 2006), the caried areas can be detected in their early stages with DIFOTI, appearing as dark areas. The results may be superior to those afforded by radiography (Pretty & Maupome, 2004; Pretty, 2006), though further studies are needed in order to confirm this possibility.

To summarize, FOTI in combination with visual inspection may be useful for determining occlusal caries depth, though further in vivo studies are needed. While in wait of such studies, we consider that transillumination should not be used for diagnosing hidden dentin caries, due to the low sensitivity of the technique and its poorer results compared with X-rays. However, FOTI in combination with VI should be taken into consideration in those cases where X-rays cannot be obtained.

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