Qualitative lightinduced fluorescence QLF

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Toothache Causes and Treatments

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Qualitative light-induced fluorescence (QLF) is used for the detection and quantification of early-stage caries (Pretty, 2006; McComb & Tam, 2001) and for monitoring demineralization or remineralization of smooth surface lesions (Verdonschot & van der Veen, 2002; Heinrich-Weltzien et al., 2005). The tooth is illuminated by the diffuse blue-green light beam of an argon laser at a wavelength of 488 nm (Tran^us et al., 2005; McComb & Tam, 2001). It can also be illuminated by a xenon microdischarge arc lamp and optic fiber system generating blue light at a wavelength of 370 nm (Pretty, 2006), with conduction by a liquid guide. The images are obtained in a dimmed environment using a portable intraoral video camera, with software processing. These images can be used to calculate lesion size, depth and volume (Tran^us et al., 2005; Zandona & Zero, 2006). The demineralized areas appear as dark zones, since radiation of the carious lesion is lower than that of the healthy enamel (Tran^us et al., 2005). The intensity of the emitted light is correlated to mineral loss and can be quantified (Verdonschot & van der Veen, 2002).

QLF is sensitive and reproducible in quantifying smooth surface caries, though it does not discriminate between lesions confined to the enamel layer and dentin caries (McComb & Tam, 2001). The applicability of this technique appears to be limited by lesion depth (McComb & Tam, 2001) - QLF being effective up to 400 ^m in depth, but not beyond. The possibility of adapting the technique to the diagnosis of occlusal caries is under investigation, though few clinical studies have been made to date (Weerheijm et al., 1992; McComb & Tam, 2001). Table 5 shows the sensitivity and specificity data of in vitro studies on QLF in application to occlusal dentin caries. This diagnostic technique can be affected by the degree of humidity or dryness of the fissures, their stains and morphology and does not appear to distinguish between caries and hypoplasia.

AUTHOR

LEVEL

STUDY

SENSITIVITY

SPECIFICITY

Stookey 2001

Dentin

in vitro

0.49

0.67

Zandona 2006

Dentin

in vitro

0.61

0.59

Pretty 2004

Dentin

in vitro

0.77

0.67

McComb 2001

Dentin

in vitro

0.72-0.76

0.79-0.81

Table 5. Sensitivity and specificity of QLF in the diagnosis of hidden dentin caries.

Table 5. Sensitivity and specificity of QLF in the diagnosis of hidden dentin caries.

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