Comparison of different methods of excavation control for minimally invasive caries treatment
Nadezhda Georgieva Mitova1a*, Maya Rashkova1b, Galina Zhegova1c, Todor Uzunov2c, Dimitar Kosturkov3d, Nikolay Ishkitiev4e
1Department of Pediatrics Dentistry, Faculty of Dental Medicine, Medical University-Sofia, Bulgaria
2Department of Prosthetic Dentistry, Faculty of Dental Medicine, Medical University-Sofia, Bulgaria
3Department of Conservative Dental Medicine, Faculty of Dental Medicine, Medical University-Sofia, Bulgaria
4Department of Medical Chemistry and Biochemistry, Faculty of Medicine, Medical University-Sofia, Bulgaria
aDDS, Assistant Professor
bDDS, PhD, Professor
cDDS, PhD, Associate
dDDS, PhD Student
eDDS, PhD, Assistant Professor
Assistant Professor Nadezhda Georgieva Mitova, DDS
Department of Pediatrics Dentistry, Faculty of Dental Medicine, University-Sofia1, Georgy Sofijski blvd., BG-1431 Sofia, Bulgaria
Tel/Fax: +359 886 216 886
*(all pictures and tables are shown in .pdf document)
Introduction: The change in the color of the dentine, registered by visual and tactile method for control, is an objective method for the assessment of demineralization of the carious process in depth. The aim of the research is through an in vitro experiment, to study the changes in the dentine’s color in depth, during mechanical caries excavation, comparing two methods for control – visual and tactile, and by fluorescence.
Methodology: Subjects of the study were 32 extracted teeth, with similar in size dentine occlusal or proximal carious lesions (D3), excavated down to healthy or affected dentine, controlled with two methods – visual and tactile (by Bjørndal) and fluorescent. Pictures were taken from the tooth samples and the resulting images were subjected to a software color analysis with the use of the Hue, Saturation and Brightness color system.
Results: Visual and tactile controlled mechanical excavation down to healthy dentine results in dentine at the bottom of excavation having the same characteristics as the healthy dentine, which indicates that the method is sufficiently objective but risk of over-excavation exists. After applying fluorescently controlled method and the fluorescence disappears after the excavation, the dentine at the bottom of the excavation has much darker coloration than the healthy dentine.
Conclusion: Fluorescent method of control gives us opportunity to leave non-infected, demineralized dentine at the bottom of the cavity and should be preferred method in the light of minimally invasive treatment of dentinal caries.
Keywords: dentin, excavation, fluorescence, minimally invasive caries treatment.
In recent years the treatment with minimal intervention has been the subject of studies in all fields of modern medicine. With regard to deep dentinal carious lesions, dental science focuses on researching and developing of new methods related to the choice of technique of excavation, control during excavation and stimuli for internal remineralisation 1, 2, 3, 4.The goal is to prevent or detect the disease in its early stage, modern diagnostic and treatment procedures with minimal intervention for the maximum preservation of dental structures to be used. The minimally invasive excavation in treatment of deep dentinal caries requires a controlled, selective and sparing approach. Various techniques for selective excavation only of irreversibly damaged dentine have been developed 3, 5, 6, 7. The concepts for step excavation have been created. Control during excavation is getting an important condition for a selective removal only of irreversibly damaged dentine and preservation of the one which is minimally infected and that has preserved remineralizing properties (relatively preserved three-dimensional collagen structure, preserved intrafibrillar mineral).
In practice the most often method applied for control of excavation is the classical – visual and tactile, assessing the color and texture of carious dentine. The method is highly subjective, that requires development of other methods for controlling of the excavation by staining with dyes, by stimulating of the dental structures’ fluorescence etc. 1, 8, 9. In recent years FACE (Fluorescence Aided Caries Excavation) technology was established as an innovative method for the detection of infected dentine. It uses the principle of fluorescence, wherein a substance is irradiated by light of a certain wavelength (most often in the blue or ultraviolet range, it can be also laser light) absorbs the photons and secondarily emits to longer wavelength. Control of excavation is based on different fluorescence of various dental tissues and on red fluorescence of bacterial products 10. Such a device is Facelight light probe (W&H Dentalwerk Bürmoos GmbH, Bürmoos, Austria), where the tooth is illuminated with violet light (405 nm). Infected dentine can be seen in red and healthy structures in green color 7. SOPROLIFE (SOPRO ACTEON Imaging, La Ciotat cedex, France) is a similar device consisting of intraoral camera with the capability of high magnification for detecting caries by black green fluorescence due to the loss of mineral and control excavation in dentine 11, 12. There are studies that use a diode laser fluorescence (DIAGNOdent pen, KaVo Dental GmbH, Biberach, Germany) to control the excavation of carious dentine not with standing that the apparatus itself is designed primarily for the diagnosis of initial carious lesions 9, 13. The comparative studies with regard to accuracy, sensitivity and specificity of various methods for assessment of the residual dentine have been conducted. Usually these are in vitro experiments on extracted teeth, where as a standard a histological findings, visualized by confocal microscopy, scanning electron microscopy or confocal laser scanning microscopy, etc. are evaluated 14, 15. The results give priority to the modern fluorescent techniques that objectify in best way the infected dentine and give the possibility of minimally invasive excavation in the deep dentinal caries treatment 11, 16, 17.
The purpose of this study is to investigate changes in the color of dentine in depth at mechanical caries excavation using two methods of control – visual and tactile and fluorescence with Facelight, in vitro.
2. Material and methods
Object of our experiment were 32 extracted teeth with similar sized dentinal occlusal or proximal carious lesions (D3), divided into 4 groups with 8 teeth in each one (Table 1).
During the excavation, the samples were evaluated clinically by two methods:
A visual tactile method 18 and fluorescence method with caries detector – Facelight (W&H Dentalwerk Bürmoos GmbH, Bürmoos, Austria) – an innovative method for detection of infected dentine, in which the tooth is illuminated with violet light up to 405 nm. Glasses with filter up to 500 nm of the optical spectrum are used. Infected dentine can be seen in red and healthy structures in green-like color.
The criteria used for dentin evaluation are presented in Table 2.
We used the following criteria for healthy and affected dentine specified in our previous study (19).
Criteria for excavation up to healthy dentine (Table 2):
- In visual and tactile control method – yellow or light yellow dentine; hard consistency, slightly creaking and resistance when probing;
- In fluorescence control method with Facelight – pale red fluorescence disappears.
Criteria for excavation up to affected dentine:
- In visual and tactile control method – dark yellow or light brown dentine; medium-hard consistency, a slight resistance when probing with a white trail;
- In fluorescence control method with Facelight – a weak pale red fluorescence only at the bottom of the cavity.
The cavity preparation was conducted by one examiner and the evaluations were made by 3 examiners after preliminary calibration.
Preparation of extracted teeth for the experiment
The extracted teeth used in this study were stored in a solution of distilled water with thymol. At least 24 hours prior to the excavation they were left in pure distilled water. After completion of the excavation and clinical assessments the roots were separated from clinical crowns, then the samples were dried in alcohol solutions of increasing concentrations (30%, 70%, 90%). Cavities were isolated by restoration using temporary filling material (Adhesor, SpofaDental a.s. HQ, Jičín, Czech Republic). Then samples were packed with an epoxy resin in plastic cylinders with a diameter of 1.5 cm and height of 3.5 cm. After resin polymerisation, the specimens were bisected in the axial axis of the tooth in the mesio-distal direction. Temporary restorations were removed from both halves, and then they were used for the purposes of that in vitro study about the applying of photographic equipment for dentinal changes characterisation during the excavation.
Developing of methods for valuation of changes in dentine during excavation, using highly specialized digital photographic equipment and software (original authors method):
Dental samples were documented using highly specialised digital photographic equipment consisting of the following components: body – Nikon D90, lens – Nikon AF-S Micro-Nikkor 105mm f/2.8G VR, flash – Nikon SB-R 200 Speed light Remote Kit R1 (Nikon Corp., Tokyo, Japan). Photographing of the objects was carried out under the following conditions – focal distance 105 mm, coefficient of approximation – 1: 1. The resulting images underwent software analysis of the color under the developed original methodology, as follows: First we put Line D – parallel to the enamel dentine junction. Then Line A – forming an angle of 90° with the line parallel to the enamel dentine junction and intersecting the pulp chamber, Line B and Line C – bisectors of the angle between Line A and Line D, were drawn.
Three levels of depth were determined:
Level 1 – on the surface of the excavation
Level 2 – 80 pixels (0,4 mm) down the non excavated dentine
Level 3 – 160 pixels (0,8 mm) down the non excavated dentine
Points where the three Lines are crossing the three Levels (Fig.1) were analysed with the use of specialised digital software (Adobe Photoshop CS 5.5, Adobe Systems, San Jose, CA, USA). Randomly chosen point on the area of healthy dentine was used as control point.
In each of the three points, as well as in the control point the color was measured for each parameter according to the color system – HSB (Hue, Saturation, and Brightness) (Fig. 2). HSB system is defined as a device-independent way for determining the color, i.e., once the color defined by this system; it can be reproduced isometrically by different devices. This system presents a color as a relationship of three parameters:
Hue – shade of color. Practically it is the color itself. Measured in linear degrees – 0 – 360°;0° = red, 60° = yellow, 120° = green, etc.
Saturation – color saturation. Measured in percentages -0%=no color, 100% =highest color intensity.
Brightness – the brightness of the color. It is expressed in percentage of the black (0%) to white (100%).
Changes of the color of all points were used for analysing the change of the basic parameters and comparison of the samples.
Statistical methods. The data were statistically analysed with SPSS-19 software (SPSS Inc, Chicago, IL, USA).
- Color characteristics (HSB) of healthy dentine (control point) in the four studied groups
The following table 3 presents color characteristics of healthy dentine, which serves as control when comparing the color characteristics of the three investigated points in depth of excavated caries lesion.
It is notable from the table that the color characteristics of healthy dentine in the four studied groups showed similar values for the parameter H (hue) without any statistically significant differences when comparing between groups [p> 0,05]. It should be noted that the hue substantially reflects the primary color. Values between 39.00 and 41.00 are perceived by the eye close to the value of 60 (yellow color), which is considered as a characteristic of healthy dentine by visual tactile scale of Bjørndal .
Values for Saturation and Brightness complement the basic color. Saturation of 4 surveyed groups range between 3 – 10%, which is an indicator of low intensity, typical of the lighter colors, such as yellow color and nuances of yellow, which characterizes healthy dentine studied by us.
Brightness, which is measured as a percentage from black (0%) to white (100%), in our studied samples was over 77%, which is an indicator of approaching white. Differences between groups in terms of saturation and brightness show greater variation, which is understandable due to the fact that their values are influenced mainly by the individual terms of object capturing.
- Color characteristics (HSB) of dentine in the bottom of excavated cavity in depth
In the following tables characteristics of color in the center of dentine in excavated cavities (in solid or stagy dentine) in depth – 3 levels on a distance of 80 pixels (0.4 mm) or a common depth – 0.8 mm are given.
Table 4 presents the changes in the color of dentine in Group 1, after mechanical excavation to affected dentine, controlled in depth with visual and tactile method (Fig.3).
Table 4 shows that the surface of the remaining affected dentine at the bottom of the cavity has a color completely different when compared with the control group [shades of yellow] towards brown shades that are darker at the surface and become brighter in depth without reaching the color of healthy dentine in depth of around 1 cm [control].
Saturation in various test points decreases from 42.13% to 18.50% and the brightness increased from 68-63% to 75.63% (p<0.05). In comparison to healthy dentine the values of saturation and brightness did not reach the values of control (P <0.05).
Table 5 presents the changes in the color of dentine in Group 2, after mechanical excavation to healthy dentine, controlled in depth with visual and tactile method (Fig. 4).
The colors of all studied depths are as close as possible to the control (healthy dentine) (p>0.05). The same relationship is also seen in terms of the saturation and brightness of the obtained average values of test points in the three levels of the depth (p>0.05).
When controlling the excavation with Facelight (Fig. 5), the color of dentine is estimated as affected when a light pink fluorescence is noticed, localized only in the bottom of the cavity. The affected dentine is reliably darker than the control (healthy dentine) (p<0.05), saturation stands out from control in the entire depth of examined dentine, and brightness distinguishes authentically from control only on the surface of the dentine (Table 6). It is notable that in depth, the color of studied points remains constant and reliable differences in depth are not being found.
We introduce the “non-infected” dentine term because the presence of fluorescence in the bottom of the cavity is due to microbial bio-products in dentinal tubules during the carious process, and the absence of fluorescence in the dentine is assumed as dentine without microorganisms, which we refer to as “non-infected dentine” (Fig. 6). It differs in color from the healthy dentine registered with visual and tactile control, which will be shown in the following presented results (table 7).
When excavating to “non-infected dentine” (excavation stops when the fluorescence disappears, which is considered to be a lack of micro-organisms), the color of the surface is fairly darker than the control (healthy dentine) and lighter than the affected (Table 7). Differences in hue and saturation in comparison to control are supported with statistical confidence (p<0.05). This is different from the trend observed in group 2 (with excavation also to healthy dentine but with visual and tactile control), where the values are very close to the control (p>0.05). The second feature that we observe in this group is that the color remains constant in depth, but becomes less intense and with higher brightness (p<0.05).
Our hypothesis was based on the studies referred in the literature 12, 22, which presented evidences that changes in the color of carious dentine were comparable to the rate of carious process progression – partial or complete carious destruction, degree of demineralization and infection of the dentine during the carious process. There is a directly proportional relationship between the color of dentine and the extent of its destruction by caries (demineralization) on one hand and the degree of infection on another, on the basis of which a system of visual tactile control during excavation is created 3, 16, 20. On the other hand, the degree of infection of the dentine is comparable to the degree of fluorescence with Facelight detector by which we controlled the mechanical excavation.
Color of the dentine is characteristic for the level of demineralization of dental hard tissues. Our study showed that from the three parameters of color, the hue is the most stable indicator that can be used as a basis for comparative study, and saturation or brightness are complementary for color characteristic. The color of healthy dentine is close to yellow, where similar values with those of the controls are prerequisite for reliable comparative results in each group and between groups.
The results indicate that visual and tactile assessment of the excavation to healthy dentine is sufficiently precise and objective, when the purpose of the excavation is to reach a healthy dentine. This is not recommended in modern trends for minimally invasive excavation, when uncontrolled removal of dentine until reaching healthy dentine is rejected and “over excavation” is considered as harmful as insufficient excavation. There are evidences that reaching the area of healthy dentine results in a greater probability of microorganisms penetration in the depth of dentinal tubules, and further risk of dentine infection 15, 21.
According to the results obtained in our study, we can conclude that dentine evaluated as affected by Facelight control has a degree of demineralization, which remains uniform in depth and differs significantly from healthy dentine. If we make analogy between color changes and the degree of dentine demineralization in depth, due to the advancing front of the carious process, we could say that in fluorescence control, affected dentine remains demineralized to greater extent in the studied depth of 1 mm. Our results show another very interesting trend that “non-infected dentine” does not necessarily have the classical yellow characteristic of healthy dentine. The non-infected dentine, obtained by fluorescence control is partially demineralized and it must be preserved without the need of “over excavation” of dentine. Similar in vitro study was carried out by Benarjee et al on 12 extracted carious molars 3, 22. Researches for micro hardness (at Knoop), emission of auto fluorescence signal [using a confocal laser scanning microscope], and digital photo images on the sliced surfaces of tooth samples in set points were conducted. The results obtained were used for direct comparisons between color, auto fluorescence and micro hardness of each lesion. The authors demonstrated that a correlation, exists between the changes in the analyzed parameters. According to them, the transmission of fluorescent signal stops before reaching a dentinal layer, which micro hardness values are close to those typical for healthy dentine. This dentine layer had a light yellow to light brown color and a relatively preserved hardness 3, 16, 22. That allows researchers to propose the use of auto fluorescence signal emitted by carious lesions as an objective and reliable criteria for control during excavation.
According to the results obtained in our previous study 19, there is a reverse-proportional relationship between the color of the dentine and the intensity of the fluorescent signal. Similar conclusion, however for a correlation between the hardness of the dentine and intensity of the fluorescence signal observed in other studies 11, 20, 22. There is also evidence for in vivo studies demonstrating the close association and relationship between the texture and color of carious dentine and quantity of microorganisms in it 14, 15.
The overall conclusion that can be done is that at the bottom of the excavated cavities, the remaining affected dentine differed in all 3 characteristics of the color, which is in the area of the brown tones and in depth hue changes to yellow, the saturation to low rates, which is indicative of a reduction in saturation and brightness changes in the direction of increasing the percentage (towards white). This indicates the presence of remaining demineralized dentine as the degree of demineralization decreases in depth when using the visual and tactile control and remains more uniform demineralized when fluorescent control is used.
Excavation to healthy dentine with visual and tactile-controlled method differed in color from “non-infected dentine” registered with fluorescent method of control, whose color is an indicator for a partial demineralization but with no microorganisms or microbial bio-products, which is a prerequisite such dentine to be retained and it is preferred instead of over excavating to healthy dentine or reaching the underlying pulp. In the first case, the color is fairly close to the color of healthy controls, and the second is distinguished reliably from it.
Our study shows that changes in the color of dentine registered by HSB system can be used as an objective method for monitoring the degree of demineralization in depth of the carious process in in vitro studies.
The methods for excavation under visual and tactile method for control provide inconsistent and non-satisfactory results: Mechanical excavation to affected dentine under visual and tactile method for control leads to remaining of demineralized dentine up to the depth of 0.8 mm. The demineralization zone does not acquire the characteristics of healthy dentine, and cannot be defined as non-infected. In excavation to healthy dentine, the characteristics of dentine in depth match those of healthy dentine, but with high possibility of over excavation.
On the other hand, during excavation controlled by fluorescent method of control, the color characteristic of the dentine when the fluorescence signal disappears indicates the presence of partially demineralized but non-infected dentine, which can be preserved doing cavity preparation. Thus the fluorescent control allows selective and gentle excavation, which is recommended in minimally invasive treatment of dentinal caries.
The publication is a result of research under Contract № 43/2013, project №20/2013, funded by the Council of Medical Science at Medical University of Sofia, Bulgaria. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
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