ONLINE ONLY ARTICLES - ORIGINAL ARTICLE
|Year : 2019 | Volume
| Issue : 3 | Page : 475
Analysis of optical mineralogy of cemento – enamel junction in deciduous dentition
Preethi Arunachalam, R Ramya, R Swarnalakshmi, Amritha James, M Ramya, K Rajkumar
Department of Oral Pathology, SRM Dental College, Chennai, Tamil Nadu, India
|Date of Submission||18-Jul-2019|
|Date of Acceptance||07-Sep-2019|
|Date of Web Publication||19-Dec-2019|
Department of Oral Pathology, SRM Dental College, Bharathi Salai, Ramapuram, Chennai - 600 089, Tamil Nadu
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Background: Optical analysis of mineralized tissues with polarized microscopy is based on the mechanism of light interaction with biological tissues and spatial distribution of light. Understanding the light propagation mechanisms in mineralized tissues has huge clinical relevance in terms of esthetics and restoration. The present study aims to analyze the mineralogy characteristics of the cementoenamel junction (CEJ), which is a vital region involving merger of tissues with varied embryological origins.
Aim: To analyze the mineralogy characteristics and CEJ patterns in deciduous teeth.
Objectives: The variations of CEJ pattern in deciduous teeth and mineralogy characteristics such as retardation and birefringence are compared to the adjacent regions of underlying dentin corresponding to the permanent dentition.
Results: Mineralogy characteristics showed variation near the CEJ when compared to the adjacent regions of underlying dentin (statistically significant [P < 0.05]). When compared to permanent dentition, they showed a numerical difference, but the values were statistically insignificant. CEJ pattern analysis predominantly showed edge-to-edge interrelation, followed by root cementum overlapping the enamel and gap type.
Conclusion: Analyzing CEJ in primary dentition is of paramount importance as it is a vulnerable zone in terms of caries progression and restorative margins. Increased edge-to-edge type of CEJ suggests a natural shield-like protection offered by enamel. Variations in mineralogy characteristics in the CEJ of deciduous dentition suggest the increased mineral content than in the adjacent regions of underling dentin. However, further investigations using advanced techniques for mineralogy analyses such as atomic force microscopy can help yield more intricacies of hard tissues of tooth.
Keywords: Birefringence, cementoenamel junction, deciduous dentition, Michel–Levy interference chart, optical mineralogy
|How to cite this article:|
Arunachalam P, Ramya R, Swarnalakshmi R, James A, Ramya M, Rajkumar K. Analysis of optical mineralogy of cemento – enamel junction in deciduous dentition. J Oral Maxillofac Pathol 2019;23:475
|How to cite this URL:|
Arunachalam P, Ramya R, Swarnalakshmi R, James A, Ramya M, Rajkumar K. Analysis of optical mineralogy of cemento – enamel junction in deciduous dentition. J Oral Maxillofac Pathol [serial online] 2019 [cited 2020 Jan 18];23:475. Available from: http://www.jomfp.in/text.asp?2019/23/3/475/273491
| Introduction|| |
The cementoenamel junction (CEJ) represents the anatomic limit between the crown and root surface. The border created by these two dental tissues has much significance as it is usually the location where the gingiva attaches to tooth by periodontal fibers. Acellular extrinsic fibers cover the cervical root surfaces in both permanent and deciduous teeth. They contain collagen fibers and noncollagenous proteins as organic matrices, both of which make it fully mineralized. Several studies have been conducted to study the nature and peculiarity of CEJ using light microscopy, stereomicroscopy and scanning electron microscope (SEM). However, Cloquet in 1899 was the first person to describe the three possible relationships of the levels of CEJ by optical microscopy, but there said to be an inability in the course of interpretation. Polarized light microscope is a unique contrast-enhancing technique that uses polarized light in improving the quality of the image obtained with birefringent materials when compared to other techniques. Cemental tissue can be viewed under a polarized light microscope which elicits high degree of sensitivity because of the differing collagen fiber orientation and organization and variable densities of fibrils relative to mineral and ground substance that can be utilized for both quantitative and qualitative studies.
The CEJ in permanent teeth is of great interest, as it is essential in the diagnosis of probing depth, periodontal attachment loss and dentinal sensitivity due to tooth erosion. The prevalence of cervical caries and adhesion problems in restorations during etching and bonding also reveals the significance of CEJ position. It also influences in stress distribution within the tooth-supporting structure to the alveolar bone and periodontal ligament as a cushion pad. In permanent dentition, cementum overlaps enamel in 60% of cases; cementum meets enamel edge to edge in 30% of cases (butt joint) and 10% cementum and enamel showing gap junction.
CEJ in deciduous dentition also shares prime importance, because the continuous passive eruption and growth of the jaws displace the primary teeth from their original position, thereby exposing the CEJ to the oral cavity during mixed dentition period. As cementum is thinner, irregular and rougher in primary dentition compared to permanent teeth, extreme care is necessary to prevent from developing caries and during application of restorative agents., The mineral composition of cementum determines the depositional pattern, and in case of any defective formation of cementum, it is essential to understand the mineralogy characteristics. However, detailed information on the nature and patterns of the CEJ of deciduous teeth is not explored extensively.
Thus, the purpose of this study is to establish the patterns of CEJ in primary dentition and the mineralogy characteristics such as retardation birefringence near the CEJ of deciduous tooth when compared to the adjacent regions of underlying dentin and to correlate it with the permanent dentition under polarized light microscopy.
| Materials and Methods|| |
Thirty freshly extracted deciduous and permanent teeth collected were sectioned longitudinally in a buccolingual aspect using an Arkansas stone to 50 μm thickness. Tooth with up to one-third root resorption, nonrestored deciduous tooth, teeth extracted for orthodontic treatment and retained deciduous tooth were included in the study. Tooth having root resorption more than one-third, grossly decayed teeth, root stumps, restored tooth and tooth subjected to endodontic treatment, fractured tooth, caries involving CEJ and supernumerary tooth were excluded from the study. These teeth specimens were then mounted and examined under a polarized light microscope to analyze the variation in CEJ pattern. Mineralogy characteristics such as retardation and birefringence were assessed using the Michel–Levy interference chart. Birefringence (B) was inferred by comparing the color of the CEJ and the adjacent region of dentin of the sectioned tooth with that of the Michel–Levy interference chart. With the ideal thickness (t) of the sections being 0.05 mm, retardation was calculated using the formula,
Retardation (G) = Thickness (t) × Birefringence (B)
The data obtained were statistically analyzed using SPSS 25.0 software (IBM corporation, India). t-test was done to compare the mean birefringence and retardation near the CEJ and the adjacent regions of underlying dentin in deciduous and permanent teeth samples having the significance set at P < 0.05.
| Results|| |
In our observations under a polarized light microscope, deciduous dentition showed that an edge-to-edge (60%) interrelation between enamel and cementum was the most prevalent feature observed followed by cementum overlapping the enamel (26%) and gap junction of 14% [Figure 1]. CEJ patterns in permanent dentition are shown in [Figure 2]. The percentage variation of the CEJ patterns between permanent and deciduous dentition reveals a significant difference as shown in [Graph 1]. Birefringence and retardation which were evaluated showed a significant mineralization near the CEJ when compared to the adjacent regions of underlying dentin in deciduous dentition (P < 0.05) as shown in [Table 1]. Whereas in case of permanent dentition it was not statistically significant (P > 0.05), [Table 2], there was numerical difference between CEJ and adjacent regions of underlying dentin.
|Figure 1: Types of cementoenamel junction of deciduous tooth viewed under a polarized light microscope. (a) Edge to edge relation; (b) Cementum overlapping enamel; (c) Gap relation (exposed dentin)|
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|Figure 2: Types of cementoenamel junction of permanent tooth viewed under a polarized light microscope. (a) Edge to edge relation; (b) Cementum overlapping enamel; (c) Gap relation (exposed dentin)|
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|Table 1: Mean and P value of birefringence and retardation in deciduous dentition|
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|Table 2: Mean and P value of birefringence and retardation in permanent dentition|
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| Discussion|| |
The optical properties of crystals are one of the most reliable properties available to distinguish and identify minerals, where the visible light is transmitted through the crystal, and thus are dependent on structure, symmetry of the crystal and chemical composition of the mineral. The variation of absorption color with vibration direction of the light is described as pleochroism, which depends on the orientation of the material in the light path and is a characteristic of anisotropic materials. Polarized light microscopy provides information on absorption color and optical path boundaries between crystals of differing refractive indices. Image contrast arises from the interaction of plane-polarized light with a birefringent (or doubly refracting) specimen to produce two individual wave components that are each polarized in mutually perpendicular planes. The velocities of these components are termed as the ordinary and the extraordinary wavefronts (slow and fast rays). Birefringence depends on the difference between the indices of refraction of the ordinary and extraordinary rays. These rays, which vibrate in two different directions perpendicular to one another, then interfere upon leaving the mineral. The interfering waves then enter the analyzer. Retardation of the specimens is also a significant property in the production of color from the crystals, which is calculated from the distance between the slow and fast rays after they have left the crystal. Retardation thus depends on the thickness of the mineral and the birefringence of its rays. The colors hence observed under the illumination of white light in the microscope eyepiece can be utilized to quantitatively draw conclusions about the optical characteristics of particular mineral using the Michel–Levy interference chart.
Analysis of the anatomy of the CEJ is helpful in understanding the adaptive property and pathological processes that occur in this region. Cementum contains two types of fibers, i.e., extrinsic (Sharpey's) fibers which are embedded ends of the principal fibers and intrinsic fibers which are fibers of cementum proper. Acellular extrinsic fibers cover cervical root surfaces of the teeth which contain collagen fibers and noncollagenous proteins as organic matrices, both of which are fully mineralized. The inherent crystalline nature and the histological features are better visualized under polarized microscopy than transmitted light microscopy because of the crystals property to split a polarized light into two, called birefringence. The selection criteria for the collection of the teeth to be investigated by a polarized microscope in this study were chosen in order to describe the mineralogical characteristics of the CEJ in sound deciduous teeth. The variations established in our study regarding the mineralogy characteristics in the CEJ of deciduous dentition suggest increased mineral content than in the adjacent region. When corresponds to permanent dentition, though they showed a numerical difference, it was statistically insignificant. Several studies have been conducted to study the nature and peculiarity of CEJ in permanent tooth using light microscopy, stereomicroscopy and scanning electron microscopy. Cloquet in 1899 was the first person to describe three possible relationships among the dental hard tissues at the level of CEJ by optical microscopy. Conventionally, three types of CEJ are encountered in permanent dentition: (a) overlap, in which cementum overlaps enamel; (b) abutment, cementum butts with enamel and (c) gap, a space between cementum and enamel, exposing cervical dentin.
In spite of the similar features in permanent and primary teeth, some peculiar characteristics were observed in the present study with regard to the variation in CEJ patterns in primary dentition. Cementum and enamel edge-to-edge interrelation was the most prevalent feature observed in overall samples, which shows the significant variation from the permanent dentition in our study. The difference of CEJ patterns dictates that this region should be handled with care from progression of caries, application of chemicals, usage of dental instruments and restorative materials. Primary teeth present a thinner cementum, clinically implying the possibility of easy passage of chemicals, including bleaching agents, when applied both externally and internally. Studies done by means of SEM highlighted the prevalance of overlapping cementum on enamel and an edge - to - edge relationahip, with no gaps between enamel between enamel and cementumm being observed. Although literature showed the presence of enamel overlapping the cementum interrelationship in permanent teeth and deciduous teeth, it has been attributed to an interpretational error as the ground section method showed some major sources of artifact formation due to shrinkage during the preparation of specimen. It is also said to be a misconceived concept because of the optical illusion and also by the basis of cementogenesis, cementum is initiated only after completion of enamel formation. However, the current study did not locate the fourth pattern.
Thus, the nature and location of CEJ in deciduous dentition was explored and substantiated with permanent dentition with the aid of polarized light microscopy. Further studies using advanced techniques such as atomic force microscopy and petrographic microscope require in overcoming the limitations encountered in our study, such as anatomical changes occurring during teeth grinding and interpretational errors while assessing CEJ as they provide only two dimensional analyses and do not allow examination of the entire circumference of the CEJ.
| Conclusion|| |
Analyzing CEJ in primary dentition is of paramount importance as it is a vulnerable zone in terms of caries progression, restorative marginal adaptation and because of its continuous passive eruption. Variations in mineralogy characteristics in the CEJ of deciduous teeth suggest increased mineral content than in the adjacent regions. Predominant edge-to-edge type of CEJ suggests a natural shield-like protection offered by enamel. However, advanced techniques such as atomic force microscopy, electrochemical strain microscopy and SEM can help yield more intricacies of hard tissues of tooth and for its mineralogy analyses.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
| References|| |
Astekar M, Kaur P, Dhakar N, Singh J. Comparison of hard tissue interrelationships at the cervical region of teeth based on tooth type and gender difference. J Forensic Dent Sci 2014;6:86-91.
] [Full text]
Stutz AJ. Polarizing microscopy identification of chemical diagenesis in archaeological cementum. J Archaeol Sci 2002;29:1327-47.
Kumar GS. Orban's oral histology and embryology. Haryana, India. Elsevier Health Sciences; 2014.
Vandana KL, Haneet RK. Cementoenamel junction: An insight. J Indian Soc Periodontol 2014;18:549-54.
] [Full text]
Francischone LA, Consolaro A. Morphology of the cementoenamel junction of primary teeth. J Dent Child (Chic) 2008;75:252-9.
Sørensen BE. A revised Michel-Lévy interference colour chart based on first-principles calculations. Eur J Mineral 2012;25:5-10.
Hassan RM, Mohamed DG. Cementoenamel junction in Egyptian maxillary first premolar: scanning electron microscopy and energy-dispersive X-ray analysis study. Int J 2015;3:545-56.
Ceppi E, Dall'Oca S, Rimondini L, Pilloni A, Polimeni A. Cementoenamel junction of deciduous teeth: SEM-morphology. Eur J Paediatr Dent 2006;7:131-4.
[Figure 1], [Figure 2]
[Table 1], [Table 2]