Fiber-optic transillumination (FOTI) and digital imaging fiber-optic transillumination (DIFOTI) have been introduced to improve early detection of carious surfaces and have been accepted by clinicians as a supplementary tool during clinical examinations.
FOTI (Figure 10) device is a practical, easy, fast and inexpensive method of imaging teeth in the presence of multiple scattering. It is based on the changes in the scattering and absorption phenomenon of light photons that increases the contrast between sound and enamel caries. In other words, results from a local decrease of transillumination owing to the characteristics of the carious lesion. The illumination is delivered via fiber-optics from a light source to a tooth surface. The light propagates from the fiber illuminator across tooth tissue to non-illuminated surfaces. The resulting images of light distribution are then used for diagnosis. Its transmission can be observed either in the opposite side or in the occlusal surfaces, when molars and premolars are analyzed. As light scattering is higher in the demineralized enamel, it is possible to see the lesion as a dark area or a shadow. Besides, carious dentin appears orange, brown or grey underneath the enamel. This can help on the differentiation between enamel and dentin lesions. However, it has been show that FOTI diagnosis by naked eye can be subject to great inter- and intra-examiner variation (Neuhaus et al., 2009).
To overcome the variability dilemma in FOTI, a new method has been tested. DIFOTI (Figure 11) is a method which employs digital image processing for quantitative diagnosis and prognosis in dentistry. It is based on light propagation just below the tooth surface and can be used to determine lesion depth. It uses fiber-optic transillumination of safe visible light to image the tooth. In this system, light delivered by a fiber-optic is collected on the other side of the tooth by a mirror system and recorded with a CCD imaging camera, instantaneously. Thus, DIFOTI images can be acquired in repeatable fashion by maintaining adjustment of a number of imaging control parameters. Then the acquired information is sent to a computer for analysis with dedicated algorithms, which produce digital images that can be viewed by the dentist and patient in real time or stored for later assessment. In addition, this system can use digital image processing methods to enhance contrast between sound and carious tissues and to quantify features of incipient, frank and secondary caries lesions on occlusal, approximal and smooth surfaces. It can also be used to detect other changes in coronal tooth anatomy, such as tooth fractures and fluorosis. DIFOTI presents higher sensitivity in detection early lesions when compared to the radiographic examination and has potential for quantitative monitoring of selected lesions over a period of time (Bin-Shuwaish et al., 2008; Young & Featherstone, 2005).
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