**4.3 Light-emitting devices**

Other method used for caries detection is based on optical properties from sound and carious dental tissues.

Fluorescence is a phenomenon where the light is absorbed in a specific wavelength and then emitted in a higher wavelength. This characteristic has been observed in the dental tissues, since the pattern of light absorption and reemission (spectrum of fluorescence) of the dental tissues varies according to the excitation light wavelength (Benedict, 1928). Thus, light absorption and reemission is different in the enamel, dentin and cementum, as well as in sound and carious tissues. For this reason, fluorescence can be used for the detection and subsequent diagnosis of dental caries.

The natural fluorescence of hard dental tissues has been studied since long time ago. It is well known that as the enamel as the dentin shows an auto-fluorescence. In this way, caries lesions, dental plaque and microorganisms also show fluorescent components. It has been observed that the difference between natural fluorescence of sound and carious dental tissues can be quantified using light-emitting devices, such as laser, xenon or LED.

#### **4.3.1 Laser fluorescence devices (DIAGNOdent and DIAGNOdent pen)**

Laser fluorescence device is a non-invasive and quantitative method based on the laserinduced 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

Recently, a digital subtraction radiographic system was evaluated on occlusal surfaces (Ricketts et al., 2007). In this in vitro study, accuracy and reproducibility of DSR was compared to visual assessment of paired digital images in detecting changes in mineral content within occlusal cavities. Intra-examiner and inter-examiner reproducibility for detection of demineralization from the subtraction images was significantly better than viewing the paired images side by side. The subtraction radiography system used was found to be more accurate and reproducible than visual assessment of paired digital images, showing promising results for monitoring occlusal lesion progression in clinical studies.

It is important to clarify that DSR will not necessarily improve the detection of a caries lesion, but will only provide important information on any changes occurring over time, and is therefore, suitable for monitoring lesion behavior. As a new method, other studies

Other method used for caries detection is based on optical properties from sound and

Fluorescence is a phenomenon where the light is absorbed in a specific wavelength and then emitted in a higher wavelength. This characteristic has been observed in the dental tissues, since the pattern of light absorption and reemission (spectrum of fluorescence) of the dental tissues varies according to the excitation light wavelength (Benedict, 1928). Thus, light absorption and reemission is different in the enamel, dentin and cementum, as well as in sound and carious tissues. For this reason, fluorescence can be used for the detection and

The natural fluorescence of hard dental tissues has been studied since long time ago. It is well known that as the enamel as the dentin shows an auto-fluorescence. In this way, caries lesions, dental plaque and microorganisms also show fluorescent components. It has been observed that the difference between natural fluorescence of sound and carious dental

Laser fluorescence device is a non-invasive and quantitative method based on the laserinduced 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

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

tissues can be quantified using light-emitting devices, such as laser, xenon or LED.

**4.3.1 Laser fluorescence devices (DIAGNOdent and DIAGNOdent pen)** 

should be carried out in order to validate its use in monitoring caries lesions.

**4.3 Light-emitting devices** 

subsequent diagnosis of dental caries.

range from the visible spectrum.

carious dental tissues.

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).

Fig. 5. DIAGNOdent 2095 – a laser fluorescence device for caries detection.

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.

Fig. 6. (A) DIAGNOdent 2190 or DIAGNOdent pen calibration against the standard ceramic. (B) Occlusal tip. (C) Approximal tip.

Traditional and Novel Caries Detection Methods 119

Fig. 7. (A) QLF system. (B) Fluorescence image of an enamel caries lesion on the buccal surface. (C) Fluorescence image of an occlusal caries lesion. (D) Fluorescence image of a

To enable calculation of fluorescence loss in the caries lesion, the fluorescence of healthy tissue that was originally present at the lesion site is rebuilt by extrapolation of the fluorescence of healthy tissue that is found around the caries lesion. The difference between the lesion values and the reconstructed values allows the calculation of fluorescence loss. The fluorescence emitted is directly related to the mineral content of the enamel. Thus, the image can be used later to quantify the size, depth and volume of carious lesion produced by the parameters produced by the software: lesion area (in square millimeters), lesion depth - ΔF (percentage of fluorescence loss) and volume of carious lesion - ΔQ (the product of the lesion area in mm2 and the lesion depth in percentage of fluorescence loss) (Zandoná

Through these parameters, it is possible to detect and differentiate caries lesions at an early stage of development, making this system a sensitive method for quantification of enamel caries. Another advantage is that the image can be stored and used to motivate patients to seek healthcare and to prevent dental disease through education during routine preventive care. However, this method is more complicated, since the use of QLF consists of three main steps. The first is lesion detection by the examiner and subsequent capturing of an image of the lesion. Second, quantitative analysis is done of the image. Finally, the third step involves the long-term monitoring of the caries lesions, which enjoys the benefit of an innovative video repositioning part of the software, setting the initial image and the live image based on the geometry of similar fluorescence intensities. For that, it is necessary that the images of the tooth surfaces should be captured in the same position and angulation. Thus, same magnification images obtained at different observation times could be compared (Buchalla

This fluorescence method has demonstrated that it can be reliably used by different examiners (Eggertsson et al., 1999). The literature demonstrates the diverse QLF

secondary caries lesion around a composite restoration

& Zero, 2006).

et al., 2001).

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.

#### **4.3.2 Quantitative light-induced fluorescence (QLF)**

Quantitative light-induced fluorescence (QLF) (QLF-clin, Inspektor Research Systems BV, Amsterdam, Netherlands) (Figure 7) was developed for use in caries detection and it is available commercially for clinical use. This device consists of a handheld intraoral color microvideo CCD camera, interfaced with a personal computer and custom software (QLFpatient, Inspektor Research Systems BV, Amsterdam, Netherlands). The software enables to capture and to analyze in vivo images of the tooth during clinical examination.

QLF uses a 50-watt xenon arc-lamp and an optical filter in order to produce a blue light with a 290- to 450-nm wavelength, which is carried to the tooth through a light guide fitted with a dental mirror. The fluorescence images are filtered by a yellow high-pass filter (λ ≥ 540 nm) and then captured by a color CCD camera (Al-Khateeb et al., 1997). When the tooth surface is illuminated by this high-intensity blue light, autofluorescence of the enamel is obtained by the intraoral camera, since all excitation light reflected or diffused is filtered. When a lesion is present on the surface, an increase in light scattering is observed relative to the surrounding enamel. The result of this is that the contrast between sound enamel and a carious lesion is improved with the lesion seen as being dark on a light green background (Neuhaus et al., 2009).

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

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

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

Quantitative light-induced fluorescence (QLF) (QLF-clin, Inspektor Research Systems BV, Amsterdam, Netherlands) (Figure 7) was developed for use in caries detection and it is available commercially for clinical use. This device consists of a handheld intraoral color microvideo CCD camera, interfaced with a personal computer and custom software (QLFpatient, Inspektor Research Systems BV, Amsterdam, Netherlands). The software enables to capture and to analyze in vivo images of the tooth during clinical examination. QLF uses a 50-watt xenon arc-lamp and an optical filter in order to produce a blue light with a 290- to 450-nm wavelength, which is carried to the tooth through a light guide fitted with a dental mirror. The fluorescence images are filtered by a yellow high-pass filter (λ ≥ 540 nm) and then captured by a color CCD camera (Al-Khateeb et al., 1997). When the tooth surface is illuminated by this high-intensity blue light, autofluorescence of the enamel is obtained by the intraoral camera, since all excitation light reflected or diffused is filtered. When a lesion is present on the surface, an increase in light scattering is observed relative to the surrounding enamel. The result of this is that the contrast between sound enamel and a carious lesion is improved with the lesion seen as being dark on a light green background

radiographic characteristics for the correct assessment of the lesions.

fluorescence measurements (Diniz et al., 2011; Lussi & Reich, 2005).

examination of patients with special needs or disabilities.

**4.3.2 Quantitative light-induced fluorescence (QLF)** 

(Neuhaus et al., 2009).

Fig. 7. (A) QLF system. (B) Fluorescence image of an enamel caries lesion on the buccal surface. (C) Fluorescence image of an occlusal caries lesion. (D) Fluorescence image of a secondary caries lesion around a composite restoration

To enable calculation of fluorescence loss in the caries lesion, the fluorescence of healthy tissue that was originally present at the lesion site is rebuilt by extrapolation of the fluorescence of healthy tissue that is found around the caries lesion. The difference between the lesion values and the reconstructed values allows the calculation of fluorescence loss. The fluorescence emitted is directly related to the mineral content of the enamel. Thus, the image can be used later to quantify the size, depth and volume of carious lesion produced by the parameters produced by the software: lesion area (in square millimeters), lesion depth - ΔF (percentage of fluorescence loss) and volume of carious lesion - ΔQ (the product of the lesion area in mm2 and the lesion depth in percentage of fluorescence loss) (Zandoná & Zero, 2006).

Through these parameters, it is possible to detect and differentiate caries lesions at an early stage of development, making this system a sensitive method for quantification of enamel caries. Another advantage is that the image can be stored and used to motivate patients to seek healthcare and to prevent dental disease through education during routine preventive care. However, this method is more complicated, since the use of QLF consists of three main steps. The first is lesion detection by the examiner and subsequent capturing of an image of the lesion. Second, quantitative analysis is done of the image. Finally, the third step involves the long-term monitoring of the caries lesions, which enjoys the benefit of an innovative video repositioning part of the software, setting the initial image and the live image based on the geometry of similar fluorescence intensities. For that, it is necessary that the images of the tooth surfaces should be captured in the same position and angulation. Thus, same magnification images obtained at different observation times could be compared (Buchalla et al., 2001).

This fluorescence method has demonstrated that it can be reliably used by different examiners (Eggertsson et al., 1999). The literature demonstrates the diverse QLF

Traditional and Novel Caries Detection Methods 121

An advantage of this method is that the patient can see in the computer screen the whole process of caries detection and visualize tooth areas where the disease shows more severe signals. This method makes easier the explanation to the patient concerning his/her clinical situation and possible available treatments. Besides, it is possible to monitor the caries lesion progression or arrestment overtime, as the images of the dental surfaces can be stored in the

Recently, another device for caries detection was developed on LED technology - Midwest Caries I.D. – (DENTSPLY Professional, York, PA, USA) (Figure 9). The handheld device emits a soft light emitting diode (LED) between 635 nm and 880 nm and analyzes the reflectance and refraction of the emitted light from the tooth surface, which is captured by fiber optics and is converted to electrical signals for analysis. The microprocessor of the device contains a computer-based algorithm that identifies the different optical signature (changes in optical translucency and opacity) between healthy and demineralized tooth

Fig. 9. Midwest Caries I.D. device and the standard for calibration procedure.

**4.3.5 Fiber-optic transillumination (FOTI) and digital imaging fiber-optic** 

been accepted by clinicians as a supplementary tool during clinical examinations.

differentiate enamel lesions from sound surfaces.

**transillumination (DIFOTI)** 

The demineralization leads to a change in the LED from green to red with a simultaneous audible signal, which is directly related to the severity of caries lesions. According to the manufacturer, when there is a change in the optical translucency and opacity of the dental tissues, the emitted green light changes to red and an audible signal could be heard. The faster the signal, the deeper the lesion. In the literature, there is only one published study which evaluated the Midwest Caries I.D. in vitro performance for occlusal caries detection (Rodrigues et al., 2011). In this study, the device presented the same cut-off limits for cariesfree sites and enamel caries. This means that the Midwest Caries I.D. was not able to

Fiber-optic transillumination (FOTI) and digital imaging fiber-optic transillumination (DIFOTI) have been introduced to improve early detection of carious surfaces and have

computer.

(Strassler and Sensi, 2008).

**4.3.4 LED technology (Midwest Caries I.D.)** 

applicability, such as detecting incipient primary lesions, secondary and root caries on smooth and occlusal surfaces in both primary and permanent teeth; detecting demineralization around orthodontic components; monitoring demineralization and remineralization caries lesion processes; quantifying dental plaque, erosion and fluorosis; monitoring caries removal; and detecting removal of extrinsic stains after tooth whitening (Al-Khateeb et al., 1997 ; Eggertsson et al., 1999; Neuhaus et al., 2009 ; Zandoná & Zero, 2006). However, it is important to emphasize that QLF can be influenced by some factors, such as stains, dental plaque, dental fluorosis or hypomineralization. Thus, as the presence of these confounding factors can produce images with similar appearance to that of dental demineralization, it is important that dental professionals should recognize those factors and differentiate them to perform a correct diagnosis.

QLF device has demonstrated potential to detect and longitudinally monitor caries lesions. In addition, it can provide dental professionals with significant information related to caries lesions severity. However, it should be emphasized that the information provided by QLF, as in all supplemental methods, can never be used by itself for clinical decision support. This information should be carefully evaluated and integrated to other individual patient factors and professional experience before making a definitive diagnosis and treatment plan.

#### **4.3.3 Fluorescence camera (VistaProof)**

Another device based on the light-induced fluorescence phenomenon is the intraoral camera VistaProof (Dürr Dental, Bietigheim-Bissingen, Germany) (Figure 8) that is based on six blue GaN-LEDs emitting a 405-nm light. With this camera it is possible to digitize the video signal from the dental surface during fluorescence emission using a CCD sensor (chargecoupled device). On these images, it is possible to see different areas of the dental surface that fluoresce in green (sound dental tissue) and in red (carious dental tissue) (Thoms, 2006). DBSWIN software is used to analyze the images and translate into values the intensity ratio of the red and green fluorescence. According to the manufacturer, those values are related to the lesion extension. The higher is the bacterial colonization, the higher is the red fluorescent signal. The software highlights the lesions and classifies them in a scale from 0 to 5, giving a treatment orientation in the first evaluation: monitoring, remineralization or invasive treatment. However, these values still need to be adjusted (Rodrigues et al., 2008, 2011). Recently, this device showed a good performance in detecting and quantifying dental plaque formed over smooth surfaces under high exposition to sucrose (Raggio et al., 2010).

Fig. 8. (A) VistaProof fluorescence camera and DBSWIN software analysis. (B) Six blue LEDs emitting a 405-nm light.

applicability, such as detecting incipient primary lesions, secondary and root caries on smooth and occlusal surfaces in both primary and permanent teeth; detecting demineralization around orthodontic components; monitoring demineralization and remineralization caries lesion processes; quantifying dental plaque, erosion and fluorosis; monitoring caries removal; and detecting removal of extrinsic stains after tooth whitening (Al-Khateeb et al., 1997 ; Eggertsson et al., 1999; Neuhaus et al., 2009 ; Zandoná & Zero, 2006). However, it is important to emphasize that QLF can be influenced by some factors, such as stains, dental plaque, dental fluorosis or hypomineralization. Thus, as the presence of these confounding factors can produce images with similar appearance to that of dental demineralization, it is important that dental professionals should recognize those factors

QLF device has demonstrated potential to detect and longitudinally monitor caries lesions. In addition, it can provide dental professionals with significant information related to caries lesions severity. However, it should be emphasized that the information provided by QLF, as in all supplemental methods, can never be used by itself for clinical decision support. This information should be carefully evaluated and integrated to other individual patient factors and professional experience before making a definitive diagnosis and treatment plan.

Another device based on the light-induced fluorescence phenomenon is the intraoral camera VistaProof (Dürr Dental, Bietigheim-Bissingen, Germany) (Figure 8) that is based on six blue GaN-LEDs emitting a 405-nm light. With this camera it is possible to digitize the video signal from the dental surface during fluorescence emission using a CCD sensor (chargecoupled device). On these images, it is possible to see different areas of the dental surface that fluoresce in green (sound dental tissue) and in red (carious dental tissue) (Thoms, 2006). DBSWIN software is used to analyze the images and translate into values the intensity ratio of the red and green fluorescence. According to the manufacturer, those values are related to the lesion extension. The higher is the bacterial colonization, the higher is the red fluorescent signal. The software highlights the lesions and classifies them in a scale from 0 to 5, giving a treatment orientation in the first evaluation: monitoring, remineralization or invasive treatment. However, these values still need to be adjusted (Rodrigues et al., 2008, 2011). Recently, this device showed a good performance in detecting and quantifying dental plaque formed over smooth surfaces under high exposition to sucrose (Raggio et al., 2010).

Fig. 8. (A) VistaProof fluorescence camera and DBSWIN software analysis. (B) Six blue LEDs

and differentiate them to perform a correct diagnosis.

**4.3.3 Fluorescence camera (VistaProof)** 

emitting a 405-nm light.

An advantage of this method is that the patient can see in the computer screen the whole process of caries detection and visualize tooth areas where the disease shows more severe signals. This method makes easier the explanation to the patient concerning his/her clinical situation and possible available treatments. Besides, it is possible to monitor the caries lesion progression or arrestment overtime, as the images of the dental surfaces can be stored in the computer.
