Objectives: The aim of this study was to evaluate the performance of laser fluorescence (LF) in proximal caries detection of permanent molars.
Materials and Methods: 115 permanent molars of 25 patients were examined with ICDAS-II then LF measurements were performed. The study groups were compared according to healthy status and caries experience (ICDAS-II 1, 2, 3). Relative Operating Characteristic (ROC) analysis was performed to find cut off values and McNemar analysis was used in comparison of methods. Sensitivity, specificity, accuracy and area under the ROC curve were calculated for LF. Statistical significance was calculated by using p<0.05.
Results: According to visual examination evaluation, LF cut off value found 5 for sound enamel and caries. As a result of the McNemar analysis, statistically significant difference was found between visual examination and LF (p=0.008). LF method showed high sensitivity for proximal caries detection in permanent molars (Sensitivity=0.85, Specificity=1).
Conclusions: Laser fluorescence method can be used as an auxillary method in visual examination for proximal caries detection in children.
Keywords: laser fluorescence, proximal caries, permanent molars
The minimally invasive approach, which is becoming increasingly important in today’s dentistry, is based on caries diagnosis and caries risk control and prevention of caries progression by examining the initial caries in detail. Because dental caries is a preventable disease, it should be treated before clinical signs and symptoms occur. Therefore, early diagnosis of enamel caries and noncavitated dentine caries is important 
Visual and radiographic methods are traditionally used in the diagnosis of caries. Since these methods have high specificity and low sensitivity, subjective results are obtained depending on the experience of physicians . More sensitive, specific and reproducible diagnostic tools have been developed due to the low rate of observers’ disagreement, particularly in examining changes in the structure of initial caries lesions . Digital radiography, laser fluorescence, electrical conductivity, fiber optic transillumination, digital fiber optic transillumination, quantitative laser fluorescence, near infrared laser transillumination, optical coherence tomography, ultrasonic imaging system are newly developed diagnostic methods .
One of the actual and noninvasive caries diagnosis methods developed to eliminate the lacks of traditional methods is laser fluorescence method. It is a highly mineralized tissue with a low proportion of water and organic matrix in the structure of the sound enamel and has a very poor fluorescence. Laser fluorescence works with the principle that the caries tissue absorbs and scatter the laser beam differently than healthy tissue .
The mechanism of DIAGNOdent (Kavo, Biberach, Germany), which works with the principle of laser fluorescence, is based on monitorization the fluorescence light emitted by protoporphyrin, a light-sensitive pigment, as a result of bacterial metabolic activities by sending the beam with 655 nm wavelength to the surface of the tooth and quantifying the optical values by fiber optics. The degree of demineralization is monitored with values ranging from 0-99 .
The aim of this study was to evaluate the performance of laser fluorescence in proximal caries detection of permanent molars.
MATERIAL AND METHODS
This study was approved by Marmara University Faculty of Dentistry Clinical Research Ethics Committee (Protocol no. 2017-150). 25 pediatric patients aged between 5 and 13 years who referred to the Department of Pedodontics, Faculty of Dentistry of Marmara University and with healthy permanent first molars or with noncavitated caries lesions at the mesial proximal surface were included in the study. Patients which had permanent molars with dental anomalies or restorations and any systemic disease, physical disability or mental retardation and cooperative disorders were not included in the study. Parents were asked to sign the consent form before the study.
Before the examination, the teeth were cleaned with a rotating brush and then flossed. After the cleaning, the proximal areas were examined under the reflector light with the aid of a loop of x3 magnification (Keeler, UK). The selected teeth were dried for 5 seconds by using air spray and evaluated according to International Caries Detection and Assessment System II (ICDAS II) criteria (Ekstrand et al., 2007).
The scores were:
0 – Sound tooth: nochanges in enamel translucency after prolonged air drying .
1 – First visual change in enamel: no evidence of change when seen wet, but after prolonged air drying a carious change (white or brown lesion) is visible.
2 – Distinct visual change in enamel: carious opacity or brown carious discolouration seen in wet tooth.
3 – Localized enamel breakdown: distinct loss of enamel integrity.
4 – Underlying dark shadow from dentine: a shadow of discoloured dentine visible through an apparently sound marginal ridge, buccal or lingual walls of enamel.
5 – Distinct cavity with visible dentine: cavitation in opaque or discoloured enamel with exposed dentine.
6 – Extensive distinct cavity with visible dentine: obvious loss of structure, with clearly visible extensive cavity in dentine.
The laser fluorescence (LF) method was used with the DIAGNOdent Pen (KaVo, Bieberach, Germany). Fiberoptic conical sapphire tip, which was developed for the diagnosis of proximal caries, was used in the examination. Before starting the measurements, the device was calibrated using a ceramic reference disc according to the manufacturer’s instructions, and the zero point was recorded by applying it to a healthy area on the buccal surface of the tooth to be measured. Calibration was repeated before each measurement. After calibration, it has been ensured that the instrument tip is not directed to light sources and reflective surfaces.
The reflector light was kept off during use of the DIAGNOdent Pen. The clean tooth surface was air dried for 5 seconds and insulated with cotton rolls. After the tip of the tool was positioned parallel to the tooth surface and below the point of contact, the tip was rotated about its axis to obtain a numerical value ranging from 0-99 on the digital display of the device. Three different measured values were recorded: two separate points at buccal point and one point at lingual / palatinal point. The mean values of the obtained values were recorded as DIAGNOdent Pen score.
The study groups were compared according to healthy and caries (ICDAS-II 1, 2, 3) proximal regions. Relative Operating Characteristic (ROC) analysis of the DIAGNOdent device was performed to find cut off values for permanent teeth. Cross-tabulation and Mc Nemar analysis were performed in comparison of caries diagnosis methods. Sensitivity, specificity, accuracy and area under the ROC curve (Area Under Curve, AUC) were calculated for each method using MedCalc (Free Trial). Statistical analysis of the data was performed using the Statistical Package for the Social Sciences software (SPSS 15 for Windows, SPSS Inc., Chicago, Illinois, USA) and MedCalc (Free Trial). Statistical significance was calculated using p <0.05.
115 permanent first molars of 25 pediatric patients were included in the study, 53 of which were caries and 62 healthy.
After classification according to the degree of caries, ROC analysis was performed for laser fluorescence and cut values were found. The success of the diagnostic method increases with the growth of the area under the ROC curve. Specificity and sensitivity values were recorded as cut-off points. Cutoff values were found by reference to the visual examination.
According to visual examination evaluation, laser fluorescence cutoff value found 5 for sound enamel and caries (ICDAS-II 1, 2, 3) (Sensitivity: 0.89, Specificity: 0.92, AUC: 0.97) (Figure1).
Sensitivity, specificity, accuracy and areas under the curve were calculated for proximal caries diagnostic methods according to 5 cut-off values for permanent molars with sound enamel and caries lesion interfaces, and comparisons were made between McNemar analysis. The laser fluorescence method according to the reference of visual examination showed a high sensitivity value in the diagnosis of proximal caries in permanent molars (Sensitivity: 0.85, Specificity: 1, Accuracy: 0.93, AUC: 0.92).
Table 1. Area under the curve, sensitivity, specificity and accuracy results for the proximal caries diagnosis using cut-off value (= 5)
When cross-tabulation was evaluated, in comparison with laser fluorescence and visual examination in the differentiation of sound enamel and ICDAS-II 1, 2, 3, 8 proximal surfaces (15%) with caries detected by visual examination were recorded as healthy according to LF method. The detection rate of the LF diagnostic method in healthy proximal enamel was 100%, while the rate of caries detection was 85% (Table 2). As a result of the McNemar analysis, when visual examination was taken as a reference standard, a statistically significant difference was found between the ICDAS-II 1,2,3 group and sound enamel threshold (p=0.008).
Table 2. Cross-table between laser flourescence and visual examination in ICDAS-II 1, 2, 3 and healthy threshold
The ideal method of caries diagnosis should accurately measure the depth of caries development in order to monitor the progression of active lesions and make accurate clinical decisions . Among the various methods used today, tactile and visual examination and radiography are the most commonly used in routine clinical applications ..These conventional methods have limited use, particularly in detecting noncavitated lesions at the proximal surfaces. Therefore, various early detection methods have been developed by using new technologies .
The laser fluorescence method is a simple tool that is well accepted by children and can be read in a matter of seconds without the need for cooperation. It can be used especially when the caries lesion cannot be detected visually at the proximal surfaces .
In a study where laser fluorescence method and radiographic examination were compared regarding proximal caries evaluation in permanent molars, the cut-off value found was 7 for differentiation between sound and enamel caries lesions. The difference between enamel and dentin caries was found to be 16 . In another in vivo study for the detection of proximal caries lesions in permanent molars, the diagnostic accuracy of laser fluorescence method in cavitated and noncavitated caries thresholds was detected and the cut-off values were found 16 for cavitation caries and 8 for non-cavitation caries lesions .
In our study, the sensitivity value for laser fluorescence method was 0.85 and the accuracy value was 0.93 in the diagnosis of proximal caries in permanent molars. In the clinical study of Ozkan and Guzel (2017),which was compared traditional caries diagnosis methods, laser fluorescence device and near infrared transillumination in permanent molars with proximal dentin caries lesions, radiography and near infrared transillumination methods have the highest sensitivity (0.83-0.82) and accuracy (0.82-0.80); laser fluorescence method and visual examination showed low sensitivity (0.60-0.54) .Menem et al. (2017) compared the diagnostic accuracy of laser fluorescence device and radiography in detecting cavitated and noncavitated proximal caries lesions of permanent molars. Diagnostic accuracy of laser fluorescence was found to be significantly higher than digital radiography .
More clinical studies are available in the literature regarding the efficacy of laser fluorescence on occlusal caries of permanent teeth than the proximal caries [9-13]. Sinanoglu et al. (2014) compared the laser fluorescence, visual and radiological examinations for the detection of occlusal caries in permanent molars. Visual inspection showed the highest sensitivity, accuracy and kappa values among the researchers in terms of agreement between the researchers. It has been reported than laser method can be used in permanent posterior teeth, is useful for the detection of dental caries in occlusal surfaces and can be improved using traditional diagnostic methods .
In conclusion, laser fluorescence method can be used safely in the diagnosis of proximal caries in pediatric patients. It is suitable for visual inspection as an auxillary tool and it provides quantitative results in caries diagnosis with no radiation exposure which can be caused by radiography.
This research was supported by Marmara University Scientific Research Project Coordination Unit (SAG-C-DRP-200318-0101).
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