JM Zheng wrote the final draft of the manuscript. QZ Jiang contributed to obtaining the funding, and was responsible for experimental design, data collection and analysis. All authors critically reviewed the final draft of the manuscript. All authors read and approved the final manuscript.
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Corresponding author. Received Nov 10; Accepted Jun This article has been cited by other articles in PMC. Associated Data Data Availability Statement The data and materials of the present study were available from the corresponding author. Keywords: Deciduous tooth decay, Vitamin D receptor, Gene polymorphisms. Results A total of children recruited in this study, Open in a separate window. Table 3 Binary logistic regression analysis adjusted for genotypes, age and S.
Discussion Dental caries is caused by a complex interaction between genetics and the environment [ 22 ]. Availability of data and materials The data and materials of the present study were available from the corresponding author. Consent for publication Not applicable. Competing interests The authors declare that they have no competing interests. References 1.
Prevalence and measurement of dental caries in young children. Pediatr Dent. Dental caries. Sheiham A. Dental caries affects body weight, growth and quality of life in pre-school children.
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Genetics and biology of vitamin D receptor polymorphisms. Hujoel PP. Vitamin D and dental caries in controlled clinical trials: systematic review and meta-analysis.
Nutr Rev. Enamel hypoplasia of the teeth associated with neonatal tetany: a manifestation of maternal vitamin-D deficiency. Association between enamel hypoplasia and dental caries in primary second molars: a cohort study. Pascoe L, Seow WK. Enamel hypoplasia and dental caries in Australian aboriginal children: prevalence and correlation between the two diseases.
Clark A, Mach N. Role of vitamin D in the hygiene hypothesis: the interplay between vitamin D, vitamin D receptors, gut microbiota, and immune response. Front Immunol. Slotwinska SM, Slotwinski R. Host response, malnutrition and oral diseases. Part 1. Cent Eur J Immunol. Mol Endocrinol. Valdivielso JM, Fernandez E.
Vitamin D receptor polymorphisms and diseases. Clin Chim Acta. Int J Paediatr Dent. World Health OrganizationOral health surveys: basic methods. Geneva: World Health Organization Studies on dental caries: I. Dental status and dental needs of elementary school children. Public Health Rep. Oral Dis. Association of vitamin D receptor gene polymorphisms in Chinese patients with generalized aggressive periodontitis.
J Periodontal Res. Gene-environment interactions in the etiology of dental caries. J Dent Res. Shuler CF. Inherited risks for susceptibility to dental caries. J Dent Educ. Genetic variation in human disease and a new role for copy number variants. The primary aim of this novel study was to produce a thermal map of a sound, human tooth-slice to visually characterize enamel and dentin. The secondary aim was to map a human tooth-slice with demineralized enamel and dentin to consider future injection botox levre hydratant 1000ml potential of thermal maps for caries-detection.
Calculation of thermal diffusivity and thermal conductivity was undertaken, and two methods of data-processing used customized software to produce thermal maps from the thermal characteristic-time-to-relaxation and heat-exchange.
The two types of thermal maps characterized enamel and dentin. In addition, sound and demineralized enamel and dentin were distinguishable within both maps. This supports thermal assessment of caries and requires further investigation on a whole tooth. The portion of tooth visible within the human mouth, known as the crown, has two main layers of mineralized tissue: enamel and dentin. Enamel is primarily made of hydroxyapatite, the crystals of which can vary in shape from rods and needles to rhombohedral.
They can have a variety of orientations and form enamel prisms. Between the prisms, inter-prismatic crystals, organic material such as proteins, lipids and carbohydrates can be found, as well as water. Enamel mineralization can vary between teeth and within the same tooth. The surface layer of enamel has the greatest level of mineralization, with the layer closest to dentin having the least Kunin et al.
There are different types of dentin in teeth. The outer layer, mantle dentin, is made of calcospheritic globules with interglobular spaces. Tubules may be found in mantle dentin but is usually void of them.
The next layer is circumpulpal dentin, which forms the bulk of the tooth-tissue. It is initially deposited as a cellular layer which matures to predentin and then undergoes mineralization. Tubules are present to house the odontoblast process, with mineralized intertubular dentin between. This peritubular mineral is deposited from the tubular amorphous material. Continuous production of dentin occurs throughout the life of the tooth and, if the tooth is exposed to caries or erosion for example, defensive mechanisms are available, producing either reactionary dentin usually from an odontoblast, or reparative dentin from other cells, e.
Both the mineral layers enamel and dentin are heterogeneous and provide protection to the vital soft-tissue - the pulp - centrally. These mineralized tissues are susceptible to dental decay—dental caries—one of the commonest, preventable diseases affecting the human population Marcenes et al.
Imaging techniques aid detection of dental caries, the simplest being produced from the sensory organ of the eye, which uses the visible light of the electromagnetic spectrum. Light can interact with the mineralized tooth-tissue in a number of ways, such as reflection, scattering, transmission, or absorption.
Absorption can produce heat or fluorescence. These interactions can contribute to optical detection methods, such as transillumination, optical coherence tomography and quantitative light-induced fluorescence.
There are no health-risks from these methods, which are non-ionizing. Digital imaging fiber optic transillumination DiFOTI has limited penetration depth of dental caries but can be improved by using longer wavelengths of near-infrared — nmespecially 1, nm, due to enamel transparency at these wavelengths.
Penetration-depth of optical coherence tomography OCT can also be limited but detection of lesions just beyond the dentin-enamel junction have been reported. Mineralized tooth-tissue possesses the ability to auto-fluoresce and quantitative light-induced fluorescence QLF uses this property, whereas DIAGNOdent Kavo and the LF-pen is thought to use fluorescence from protoporphyrin IX and associated bacterial products, not the mineralized tissue Hall and Girkin, ; Karlsson, ; Park et al.
Over a century ago, the first acceptable dental radiographs for clinical use were reported by Harrisonutilizing X-rays from the electromagnetic spectrum. X-rays have limitations - such as the extent of demineralization needed before caries can be detected Whaites, and its location, e. Occlusal lesions are positioned in the center of the biting-surface of the tooth and are less easily detected due to the bulk of sound mineralized tissue which surrounds them.
This surrounding sound tissue reduces penetration of the X-ray beam, compared to the demineralized lesion which would allow a greater proportion of X-rays to pass onto the image receptor, providing contrast between the lesion and sound tissue. This results in the occlusal lesion being masked by the sound surrounding tissue. X-rays are also ionizing in nature with associated biological risks, e. An infra-red thermal camera captures naturally-emitted electromagnetic radiation from the infra-red region.
Infra-red radiation has longer wavelengths nm to 1mm than X-rays 0. The Herschel family were central in discovering infra-red radiation and William Herschel was credited inand John Herschel produced the first Thermogram in Holst, By the mids, the military was maximizing the heat-seeking capacity of thermal imaging.
Technological advancement in recent years provides accessible and affordable thermal cameras with potential for clinical diagnostic application in medicine.
Currently, thermal imaging is not used to detect dental caries but warrants further investigation. In Kaneko et al.
Their findings were positive but the thermal properties of the mineralized tissue were not considered. These values were obtained from the use of thermocouples, a thermometer, a thermistor, a pulse-laser and infra-red thermography Lisanti and Zander, ; Phillips et al.
Table 1. Thermal diffusivity and thermal conductivity values of human enamel and dentin. A map provides spatial information from co-ordinates on two axes, such as X and Y. The use of a thermal value for each co-ordinate corresponding to a pixel of tooth-tissue could be represented from a grayscale, producing a thermal map specific to that tooth-tissue.
This could show the spatial relationship of the thermal properties of the tooth-tissue as an image, rather than a series of numerical values. This may be more clearly understood from the map providing a 2-dimensional relationship of the thermal properties across the whole surface of the tooth-tissue. The thermal properties of enamel and dentin may be sufficiently different to visually distinguish enamel from dentin.
Demineralized areas within both tissues may also have different thermal properties due to tissue-changes, such as mineral loss from caries, which may be seen in the thermal map. The primary aim of this study was to produce a thermal map of a sound, human tooth-slice to visually characterize human enamel and dentin.
The secondary aim was to map a human tooth-slice with demineralized enamel and dentin to consider future diagnostic potential of thermal maps in caries-detection. Both teeth were cut bucco-lingually with an Accutom-5 Struers, Copenhagen, Denmark into 1 mm-thick tooth-slices and then polished with an grit abrasive sheet, with the addition of distilled water as needed.
Slice-thickness was measured with a digimatic micrometer IP65 Quantumike Mitutoyo. Photographs and radiographs of each tooth-slice were taken. A period of 35 min stabilization was allowed prior to commencing data-collection.
Figure 1. Thermal cube with hotplate and heating-mat green in position, with camera secured on the cube by a fixed-mounting normal to the samples.
The parameters used with the camera were: Emissivity 0. The carrier was manually transferred to the aluminum hotplate. Data-capture by the thermal camera commenced prior to transfer of the carrier. Figure 2. Thermograph of Sample 1—Sound tooth-slice, with circular areas-of-interest shown to enable calculation of the characteristic-time-to-relaxation used in the computation of the thermal diffusivity of the tissues.
Once the value of thermal diffusivity was known, thermal conductivity could be calculated:. The thickness of the sound tooth-slice measured less than a millimeter in all areas, with the greatest enamel-thickness in the middle at 0. The carious tooth-slice was thicker in all areas, with the maximum thickness of enamel at 1. Table 2. Dimensions of tooth-slices as recorded with a calibrated digimatic micrometer.
The initial rewarming temperatures for the sound tooth-slice in both crown- and root-dentin green and pink broken-lines were lower than the two areas of enamel purple and blue broken-lines.
It took circa 30 s to reach thermal equilibrium of all tissues Figure 3.
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The rate of rewarming in both regions of enamel are the same and marginally quicker i. The results for the right-hand side enamel and crown-dentin respectively, show differences in characteristic-times-to-relaxation: enamel at 3.
The results indicate from the sound tooth-slice that enamel has a higher value of thermal diffusivity 3. All values are provided in Table 3. These values fall mainly within the accepted range for thermal diffusivity of enamel at 2.
Figure 3. Table 3. Within the carious tooth-slice, the rate of rewarming in the two sound enamel areas-of-interest purple and blue broken-lines are similar, whereas the enamel carious lesion is slower red solid-line Figure 4. Carious enamel fails to reach equilibrium in the 30 s time-period.
Crown-dentin green broken-line warms quicker than root-dentin pink broken-line. The carious dentin mustard solid-line is the slowest of all tissues to rewarm and fails to reach equilibrium within the time-frame.
The characteristic-time-to-relaxation for carious enamel is 5. This is the only occassion where enamel has a slower characteristic-time-to-relaxation than dentin. All other values give enamel 4. The enamel has a lower value of thermal diffusivity, ranging from 1.
Thermal diffusivity shows the crown-dentin 0.
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The carious area of dentin has an increased value of 1. The thermal conductivity of carious enamel 0. All other values of thermal conductivity for enamel and dentin within the carious tooth-slice are lower than others' findings.
Figure 4. The two thermal maps distinguish the mineralized tissues of enamel, dentin and the carious areas of both tissues using the thermal properties of characteristic-time-to-relaxation and heat-exchange during rewarming Figure 5. Figure 5.
Sample 1- Sound tooth-slice and Sample 2 - Carious tooth-slice. Initially, a photograph is shown, followed by an X-ray, then the characteristic-time-to-relaxation thermal map and, finally, the heat-exchange thermal map depicting enamel, dentin and carious areas of enamel and dentin. Infra-red thermal imaging is a technique which is yet to be maximized within the field-of-medicine and its subsidiary specialty - dentistry.
Published work for determining the thermal properties of tooth-tissue Panas et al. Tooth-slice thicknesses of 2. Lin et al. Simultaneous heat-application to the irregular occlusal surface would be unlikely, compared to the application of vertical heat to the flat surface of the samples within this study and Panas et al.
The tooth-slices within this study were viewed directly—unlike Lin et al. They were also heated directly—unlike Panas et al. Neither of these additional layers was considered in their final calculations. Despite these variations, a single-sample Lin et al. Multiple samples from different teeth have not previously been reported from this technique, nor have areas of demineralization or caries. All samples are from different donors with inherent anomalies in the tissue-types, as previously described.
Investigation of a point location or a single line of a single tissue-sample with any temperature-recording-method, e. The larger the area-of-interest used for each tissue and the greater the sample-size, the more valid and reliable any inference from the findings.
Within this study, two samples, one sound and one carious with a demineralized area, were investigated with multiple areas-of-interest for each tissue. Enamel values of thermal diffusivity and conductivity fall within proximity of known-ranges for the sound tooth-slice but do differ slightly between the two sides examined.
Greater variation is seen within the demineralized enamel, where the carious area-of-interest returns the lowest values.
This could be explained by the loss of mineral, but caution is needed as the range of values for the sound areas-of-interest differ by a similar proportion within the same sample.
These findings appear appropriate to the nature of the tissues being investigated and a more general outcome as described by Panas et al. That is, following the application of heat and analysis with thermal imaging, a difference between the thermal response of enamel and dentin was detectable, with enamel tending to conduct heat quicker than dentin.