A COMPREHENSIVE REVIEW OF VARIOUS LASER-BASED SYSTEMS USED
IN EARLY DETECTION OF DENTAL CARIES
Authors: Fawad Javed1a, Georgios E. Romanos2b*
1 Division of General Dentistry, Eastman Institute for Oral Health, University of Rochester, NY 14620, USA.
2 School of Dental Medicine, Stony Brook University, Stony Brook, NY, USA.
aBDS, PhD, Research Associate
bDDS, DMD, PhD, Professor
Professor Georgios E. Romanos
School of Dental Medicine, Stony Brook University, Stony Brook, NY, USA.
Phone: +1 (631) 632-8755; Fax: +1 (631) 632-8670; E-mail: Georgios.Romanos@stonybrookmedicine.edu
Introduction: The aim was to comprehensively review the various laser-based systems used in early detection of dental caries.
Methodology: PubMed/Medline and Google-scholar databases were searched from 1995 up to June 2015 using various combinations of the following keywords: “dental early caries”, “diagnosis”, “laser” and “light fluorescence” (LF). Literature reviews, letters to the Editor, and commentaries were excluded. Articles published only in English were included. The pattern of the present study was customized to primarily summarize the pertinent information.
Results: Laser fluorescence at 655 nm (DIAGNOdent) is a promising tool for early detection of occlusal caries. Other systems based on the LF concept include VistaProof (VP) and DIAGNOdent Pen; however, no statistically significant difference in the caries detection efficacy has been reported between VP, DIAGNOdent Pen and DIAGNOdent devices. Although light emitting diode system have also been tested for detecting caries, their diagnosing efficacy remains unclear due to a lack of studies.
Conclusion: Lasers-based caries systems are useful tools in the early detection of caries in contrast to traditional visual and radiographic examination techniques; however, further studies are needed to assess the caries diagnostic efficacy of the various commercially available laser-based caries diagnostic systems.
Keywords: dental early caries, diagnosis, laser and light fluorescence, light emitting diode
Dental caries (or caries) represent a chronic disease of the mineralized tissues of teeth, namely (enamel, dentin and cementum) caused by the action of cariogenic bacteria on fermentable carbohydrates leading to the demineralization of these mineral portions and (if left untreated) disintegration of their organic matrix . Traditionally, caries are diagnosed by visual clinical examination (for example, visualizing the size and depth of the lesion using mechanical probes) and radiographs (such as bite-wing images) ; however, these techniques are able to detect carious lesions only at an advanced stage . Yet, specificity of visual examination for the diagnosis of caries has been reported to be high; the methodology exhibits low sensitivity and reproducibility . Likewise, although digital radiography (such as digital intra-oral and extra-oral radiographs and three-dimensional computed tomography) is a modernization in imaging technology [5-7]; the potential risk of radiation hazards associated with these techniques, remains inevitable.
Novel techniques have been assessed as diagnostic tools to identify and quantify initial demineralization. Laser fluorescence (LF) (in the visible region, blue or red) has been reported to be a valuable tool for early diagnosis of caries [8,9]. Caries detecting devices based on the LF mechanism include DIAGNOdent 2095 and DIAGNOdent 2190 (LF and LFpen, KaVo, Biberach, Germany). Results by Takamori et al.  showed that LF is useful in the early diagnosis of occlusal caries. LF has also shown promising results in the detection of caries in deciduous teeth [11,12]. Likewise, other LF-based devices comprising of a light-emitting-diode (LED) and have also been developed to diagnose early caries lesions . In an in-vitro study, Rodrigues et al.  investigated the efficacy of LED and two LF-based devices in detecting occlusal caries. The results demonstrated that LED and LF based devices allow good reproducibility and are more useful tools for detecting early signs of caries than conventional caries diagnosing methods . However, the role of the examiners’ experience in detecting early caries using lasers cannot be overruled.
Early diagnosis of caries may help reduce pain, inflammation and economic burden and contribute to enhancing oral health related quality of life [15-17]. Moreover, it allows application of preventive measures to arrest the lesion by avoiding invasive restorative procedures. Therefore, the aim of the present study was to comprehensively review the various laser-based systems used in early detection of dental caries.
Materials and methods
The addressed focused question was “Which lasers-based caries detecting systems are currently available for early diagnosis of caries?”
Study eligibility criteria
The following eligibility criteria were imposed: Clinical studies, case-reports, intervention: efficacy of LF in diagnosing early carious lesions compared to traditional caries detecting techniques and studies published only in English.
Literature search strategy
To address the focused question, PubMed/MEDLINE and Google-Scholar databases were searched from 1995 up to and including June 2015 using different combinations of the following key words: “dental caries”, “diagnosis”, “laser”; “fluorescence”, “phototherapy” and “light”. Literature reviews, letters to the Editor and commentaries were excluded. The pattern of the present review was customized to summarize the relevant information.
The DIAGNOdent system (Figure 1a) uses digital imaging fiber-optic transillumination, which identifies zones of demineralization by recording the transmitted visible light that is directed at the tooth. The concept behind using a laser beam in the diagnosis of caries is that altered mineralized surfaces irradiated by a longitudinal light wave emit fluorescent radiation. The device comprises a probe that emits red light (wavelength 655 nm) directed on the mineralized teeth surface/s under examination. Demineralized teeth surfaces emit a fluorescent light (mainly due to bacterial porphyrins), which is captured back by the probe and the devices displays values ranging from 0 to 99 . DIAGNOdent has been tested extensively, including for the detection of occlusal and smooth surface caries, comparing its results with visual inspection, histology, radiography and quantitative light-induced fluorescence. However, this device was later updated by a cable free pen-type LF device (LFpen), which additionally allowed approximal surfaces to be examined (DIAGNOdent pen, KaVo, Biberach, Germany) (Figure 1b).
Light-emitting-diode based caries detection
Light-emitting-diode (LED) (MIDWEST Caries ID, MID, Dentsply Professional, York, Pennsylvania) (Figure 2) is a handheld device that aims at detecting caries. The device is based on the concept that demineralized teeth surfaces influence reflection and reflectance of the emitted light . The presence of demineralization changes the LED from green to red with a concurrent audible signal thereby confirming the presence of caries . In this caries detection system, the speed of the signal is associated with the depth of the carious lesion. To our knowledge of indexed literature, there is a scarcity of studies that have assessed the efficacy of LEDs in detecting early caries. A study by Bozdemir et al.  compared the performance of LED-based and LF-based devices with that of visual examination in the diagnosis of occlusal caries. In this study, 156 occlusal surfaces were visually examined for evidence of caries following which they were assessed with the LED- and LF-based caries detection devices . The study concluded that LED-based and LF-based devices detect caries more accurately as compared to traditional visual-examination based methodologies . However, the result showed no significant difference in the caries detecting efficacy of LED- and LF-based systems . Results by Rodriguez et al.  demonstrated that LED-based caries diagnosis systems are unable to differentiate sound surfaces from enamel caries. In this study , the laser parameters used in the LED-based caries detection system remained unclear. In this regard, further studies with a large sample size are needed o assess the significance of LED-based systems in the diagnosis of caries.
Achilleos et al. , introduced a fluorescence device (FC; Vista Proof, Duerr Dental, Germany), to detect caries on occlusal surfaces of teeth. The tool emits light with a wavelength of 400 nm and filters the fluorescence emitted by the tissue. Specific software quantifies the fluorescence on a numerical scale ranging from 0 to 5. This device also works on the same principle as that for DIAGNOdent that is, capturing the fluorescence from bacterial porphyrins. The authors reported the sensitivity of Vista Proof to be significantly greater that for DIAGNOdent (pen) . In another study, Seremidi et al.  compared the efficacy of fluorescence device VistaProof (VP) and DIAGNOdent Pen. In this study, 107 sites on 41 occlusal surfaces of recently extracted premolars were selected and classified into lesion categories according to Ekstrand’s clinical criteria . The fluorescence of the sites was measured by the Vista Proof and DIAGNOdent Pen devices. The results demonstrated no statistically significant difference between the accuracy of DP and VPs for both enamel and dentin lesions .
Multispectral near-infrared reflectance imaging
Near infrared (NIR) multispectral imaging is a novel non-invasive imaging technology that maps and quantifies caries without using ionizing radiation [22-25]. This technology works on the concept that for longer wavelengths (such as 1450 nm), water absorption increases significantly and reduces the penetration of the NIR light . NIR digital imaging transillumination technology has been shown to be useful as a diagnostic tool in the detection of proximal caries and, less importantly, for occlusal caries, fissures, and secondary decay around amalgam and composite restorations . It has also been reported that early demineralization appears with high contrast at NIR wavelengths due to a 10- to 20-fold difference in the magnitude of light scattering between sound and demineralized enamel [22,26]. In an in-vitro study, Simon et al.  assessed how the lesion contrast changes with the lesion severity and depth for different spectral regions in the NIR and compared that range of contrast with visible reflectance and LF. Forty-four human molars were painted with an acid-resistant varnish leaving a window (4 mm×4 mm) on the occlusal surface of each tooth exposed for demineralization. In the unprotected windows, artificial lesions were induced using a demineralizing solution at pH 4.5. Near-IR reflectance images were obtained over several near-IR spectral distributions, visible light reflectance and LF with 405 nm excitation and detection at wavelengths greater than 500 nm. In each sample, the severity of the demineralization window was non-invasively assessed using cross polarization optical coherence tomography (CP-OCT). The CP-OCT results showed that the severity of the carious lesions varied significantly across the sample windows and that visible light does not precisely reflect the large variation in the lesion severity as compared to near-IR reflectance. Reflectance measurements at certain near-IR wavelengths have been reported to more accurately reflect variation in the depth and severity of the lesions . Chung et al.  reported that near-IR measurements at higher wavelengths (1,200nm to 1,600nm) reflect the variation in the depth and severity of the lesions more accurately as compared to shorter wavelengths. In another study, Wu and Fried  compared the image contrast of artificial carious lesions produced on the buccal and occlusal surfaces of teeth using fluorescence, visible reflectance and near-IR reflectance. The results demonstrated that near-IR reflectance at wavelength 1,310-nm yielded the greatest contrast than visible reflectance though it remained statistically comparable with fluorescence imaging . In a recent study Söchtig et al. suggested that NIR transillumination is a method that may help avoid bitewing radiographs for diagnosis of caries in routine dental practice. However, further studies over a greater range of lesion severity are needed to determine the optimum performance ranges for this imaging technique.
Lasers-based caries systems are useful tools in the early detection of caries as compared to traditional visual and radiographic examination techniques; however, further studies are needed to assess the caries diagnostic efficacy of the various commercially available laser-based caries diagnostic systems.
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