Laser fluorescence device is a non-invasive and quantitative method based on the laser-induced fluorescence. The first laser fluorescence device, DIAGNOdent 2095 (KaVo, Biberach, Germany), was developed in 1998 (Figure 5). It is based on the quantification of emitted fluorescence from organic components of dental tissues when excited by a 655nm laser diode (aluminum, gallium, indium and phosphorus - AlGaInP) located on the red range from the visible spectrum.
The emitted light reaches the dental tissues through a flexible tip. As the mature enamel is more transparent, this light passes through this tissue without being deflected. In contact with affected enamel, this light will be diffracted and dispersed. The later is able to excite either the hard dental tissue, resulting in the tissue autofluorescence, or fluorophores present in the caries lesions. These fluorophores derived from the products of the bacterial metabolism and has been identified as porphyrins (Hibst et al., 2001). The emitted fluorescence by the porphyrins is collected by nine concentric fibers and translated into numeric values, which can vary from 0 to 99. Two optical tips are available: tip A for occlusal surfaces, and tip B for smooth surfaces. This device has shown good results in the detection of occlusal caries, however, it might not be used as the only method for treatment decision-making process (Bader & Shugars, 2006; Rodrigues et al., 2008).
Recently, a new and compact device - DIAGNOdent 2190 or DIAGNOdent pen - (KaVo, Biberach, Germany) (Figure 6) has been introduced in the market. This device functions on the same principle as the earliest. For this reason, the device was condensed and the tips were modified. The tips used in this device are made from sapphire fiber and the same solid single sapphire fiber tip is used for propagation of the excitation and for collection of the fluorescence light, but in opposite directions and different wavelengths (Lussi & Hellwig, 2006). There are two tips which can be coupled on this device: an occlusal and an approximal tip. However, its performance in approximal surfaces is still limited. The device weights 140g and only one battery (1,5V) is needed.
As mentioned before, when a caries lesion or a dental surface is assessed by DIAGNOdent, a value between 0 and 99 is observed. This value is, theoretically, related to the lesion depth. For the values interpretation, several cut-off points have been proposed in the literature, as for DIAGNOdent as for DIAGNOdent pen. These cut-off points differ from each other in some units in the enamel and dentin. For this reason, is recommended that the clinician considers the values as an interval for the interpretation and also associates clinical and radiographic characteristics for the correct assessment of the lesions.
Other factor that might be addressed is the presence of stains due to inactive lesions or calculus on the occlusal surfaces due to biological sealing. Both can result in high values of fluorescence and, in consequence, false-positive results. Therefore, as also recommended before visual examination, cleansing of dental surfaces should be performed before laser fluorescence measurements. Besides, after professional prophylaxis using bicarbonate powder or prophylactic paste, it is important that the dental surface is rinsed off, so powder or paste does not remain in the fissure or inside microcavities. This could influence the laser fluorescence measurements (Diniz et al., 2011; Lussi & Reich, 2005).
In conclusion, the clinician who intends to use this method as a auxiliary in the caries detection process should be aware of the correct device functioning and remember that several factors might interfere the results, such as staining, calculus or powder/paste remnants; calibration procedures; and cut-off points variation for enamel and dentin caries.
For this reason, DIAGNOdent or DIAGNOdent pen should not be used as major method for caries detection, but as a supplementary tool for both visual and radiographic examination. Some situations, in which the professional is in doubt concerning the presence of a caries lesion on a surface free of staining, those devices can be suggested as substitutes for the radiographic examination. Besides, in the pediatric dentistry field, their use can also be suggested when X-ray examination is not possible due to the child behavior or during examination of patients with special needs or disabilities.
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