CARIES DETECTION WITH LASER FLUORESCENCE DEVICES . LIMITATIONS OF THEIR USE
Practice
2.2 . Fluorescence of sound and carious tooth substance Fluorescence is the property of a medium to absorb low wavelength radiation such as ultraviolet ( 1-400nm ) emitting longer wavelengths of visible light ( 430-450nm ). Teeth have the ability to emit fluoresce . This phenomenon can be observed when the incident radiation is shown in the ultraviolet spectrum , as in the cases of exposure to black light illumination or when the person is found at high altitude . The primary fluorescence of teeth , otherwise known as autofluorescence , arises from the internal biological structures of the cells , with responsible elements being several enzymes , vitamins , uranium glass and endogenous fluorophores , present in dentin and enamel . 20 Dentin emits more autofluorescence than enamel , with the emission peak being at 450nm . Although the exact chemical mechanism of tooth auto-fluorescence has not yet been ascertained , the greater amount of organic components of dentine seems to be the reason for its higher fluoresce values . 21 It has been found that decayed tissues emits more fluoresce than healthy ones upon stimulation by red laser or infrared irradiation . This seems to be the result of both demineralization processes and the presence of bacteria byproducts in the decayed tissue . 22 2.3 . Caries detection methods based on visible spectrum fluorescence Quantitative fluorescence ( Quantitative Light – induced Fluorescence , QLF ) is a method used to detect the demineralization of enamel in the early stages . The technique relies on the ability of enamel to emit strong auto-fluorescence under certain circumstances . Hypomineralised enamel shows a decrease demission of fluorescence spectrum as compared to that of healthy enamel . With the use of the QLF method , demineralized areas can be detected before they become clinically visible , since the sensitivity of the specific technique is particularly high . Limitations of this technique were found in the detection of dentine caries also in the deep enamel lesions ( 400μm ), where the results were not so accurate . 23 2.4 . Caries detection devices based on laser fluorescence The difference in fluorescence between sound and carious tooth structures was the fundamental concept behind the development of devices capable of quantifying the decayed tissue fluorescence . Methods based on fluorescence are divided into those that use visible spectrum stimulating rays such as the QLF and those based on laser ray fluorescence such as the DIAGNOdent and the DIAGNOdent Pen ( KaVo Dental GmbH , Birebach / Riβ , Germany ). 23 Sundström et al . 24 in a pioneering study , stimulated carious and sound tooth structures by laser beams of different wavelengths ( 337nm , 488nm , 515nm , 633nm ), and calculated the emitted fluorescence . The 488nm wavelength was selected as the most appropriate wavelength for the detection of incipient caries with this technique .
3 . DIAGNOdent Device and DIAGNOdent Pen Device 3.1 . DIAGNOdent Device The light source of DD is a diode laser with a wavelength of 655nm and a maximum power of 1mW . The red laser beam is transferred through a descending optical fiber to its edge , made of sapphire . Two different tip designs are available . The wedge-shaped which is used for occlusal surfaces and the straight one designed for smooth dental surfaces . The excitation optical fiber , i . e . one that carries the light beam on the tissues , is surrounded by nine concentric optical fibers of smaller diameter that collect the fluorescent radiation together with the surrounding light from the dental surfaces . All optical fibers have a diameter of 40 microns and they are carved at their end to receive or transmit the light radiation in similar manner . 25 A specially designed filter prevents the diffusion of ambient light ( λ < 655nm ) and thus only the fluorescent light is collected and converted into an electrical signal . Then , the signal is displayed on two LED screens and expressed as a integer number between 0 and 99 . One screen displays the current measured value while the other records the maximum value of detection . 22 3.1.1 . Correlation detection values of DD Most clinical studies currently use the suggested measurements [ Cut-Off Values ( COV )] of the DD as they appeared in the clinical study of Lussi et al . 12 In this study , seven examiners evaluated 332 occlusal surfaces of 240 patients . After histological examination , they found that the values between 0-13 correspond to healthy dental tissues ; values between 14-20 correspond to enamel caries and values between 21-29 to dentin caries . 12 In the same study , the restorative intervention is suggested for values between 20-29 . However , Tranaeus et al . 26 suggested lower intervention values . 20-25 Anttonen et al . 27 suggested intervention values greater than 30 , emphasizing that for values greater than 40 , the probability of overtreatment is greatly reduced . Heinrich-Weltzien et al . 28 , compared the validity of various proposed COV , concluding that the superficial lesions in dentin ( D3 ) with rates between 17-21 showed the lowest discrepancy ( 0,48 to 0,51 ). For deeper dentin lesions ( D4 ), the manufacturer ’ s suggested values (> 34 ) had the best performance ( 0.51 ). Therefore , the proposed correlations of COV for DD vary considerably between studies and have changed several times even by the manufacturer . As a general observation , it is worth mentioning , that laboratory studies use lower COV for dentin caries in relation to clinical studies . 3.1.2 . Effect of exogenous factors on DD measurements Exogenous factors that could possibly influenceDD values are various toothpastes and polishing pastes . In an in vitro study , the potential effect of ten different polishing pastes and four toothpastes
48 Stoma Edu J . 2017 ; 4 ( 1 ): 46-53 . http :// www . stomaeduj . com