Microhardness of nonfluorosed and fluorosed dental cementum: An in vitro study

Nazam Lakhani; K Vandana Laxman

doi:10.4103/srmjrds.srmjrds_81_16

ORIGINAL ARTICLE

Year : 2017 | Volume : 8 | Issue : 2 | Page : 74-77

Microhardness of nonfluorosed and fluorosed dental cementum: An in vitro study

Nazam Lakhani, K Vandana Laxman
Department of Periodontics, College of Dental Sciences, Davangere, Karnataka, India

Date of Web Publication

8-Jun-2017

Correspondence Address:
K Vandana Laxman
Department of Periodontics, College of Dental Sciences, Room No 4, Davangere - 577 004, Karnataka
India

Source of Support: None, Conflict of Interest: None

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DOI: 10.4103/srmjrds.srmjrds_81_16

Abstract

Aim: The literature on the effect of fluoride on dental caries is well discussed in contrast to periodontal tissues. However, a recent review has explored an epidemiological association between fluorosis and periodontal disease and also the influence of fluorosis on periodontal structures along with the comparison of influence of periodontal treatment on fluorosed and nonfluorosed teeth. There is a scarcity in literature dealing with the effect of fluorosis on biological tissues such as bone and cementum. During the progression of periodontitis, there is a possibility of mechanical (microhardness), chemical (mineral), and histologic changes in cementum. Considering the higher incidence of periodontitis in the endemic fluorosed area around Davangere, there is an opportunity to study the cemental changes due to fluorosis which would influence the initiation and progression of periodontal disease. Hence, the aim was to study the microhardness of fluorosed and nonfluorosed cementum. Materials and Methods: A total of 24 healthy nonfluorosed and fluorosed orthodontically extracted premolars were collected to assess and compare the mechanical properties (Vickers hardness tester) of fluorosed versus nonfluorosed cementum. Results: The results of this study showed that the mean hardness of the fluorosed cementum (57.7 ± 9.4) was lower than nonfluorosed (60.40 ± 6.23) cementum. Conclusion: The clinical importance of this study is that clinicians need be aware of this difference during periodontal, orthodontic, caries treatment, crown procedures, and implant therapy.

Keywords: Dental caries, dental cementum, dental fluorosis, mechanical property, periodontitis

How to cite this article:
Lakhani N, Laxman K V. Microhardness of nonfluorosed and fluorosed dental cementum: An in vitro study. SRM J Res Dent Sci 2017;8:74-7

How to cite this URL:
Lakhani N, Laxman K V. Microhardness of nonfluorosed and fluorosed dental cementum: An in vitro study. SRM J Res Dent Sci [serial online] 2017 [cited 2023 May 28];8:74-7. Available from: https://www.srmjrds.in/text.asp?2017/8/2/74/207656

Introduction

Fluorine is a common element in the earth's crust and is an essential element for the calcification of bones and teeth. It is also established that fluoride ion has played a major role in reducing dental caries dramatically over the past 40 years. Disturbances in the enamel development (dental/enamel fluorosis), bone homeostasis, and mineralization can occur due to excessive systemic exposure to fluoride. The severity of fluorosis on periodontal tissues, both soft and hard, depends on the dose, timing, and duration of fluoride exposure during development.^[1]

The literature on the effect of fluoride on dental caries is well discussed in contrast to periodontal tissues. However, 15 years of research and a recent review by Vandana not only presented an epidemiological association between fluorosis and periodontal disease but also revealed the influence of periodontal treatment on fluorosed and nonfluorosed teeth. There is a scarcity in literature dealing with the effect of fluorosis on biological tissues such as bone and cementum.^[2]

During the progression of periodontitis, there is a possibility of mechanical, physical, and chemical changes in cementum. Considering the higher incidence of periodontitis in the endemic fluorosed area around Davangere, there is an opportunity to study the cemental changes due to fluorosis which would influence the initiation and progression of periodontal disease.

Mechanical properties of fluorosed cementum have been studied scantily. Mechanical intervention on dental surfaces during periodontal treatment is not uncommon. These procedures carried out on dental surfaces could lead to their wear, generating the need for more information on flourosed tooth structures. Therefore, it is of utmost importance to study tooth surface microhardness, so as to be aware of the wear suffered by teeth, during therapeutic and maintenance procedures, which form a part of periodontal therapy.^[3] The amount of tissue loss depends on various factors or parameters, one of these, are possibly the microhardness of the tissue being manipulated. The response to orthodontic treatment, caries treatment, restorative measures, crown and bridge procedures and implant therapy may be influenced by cemental microhardness.

The possible mechanical properties which may be different in fluorosed cementum would influence the pathogenesis of periodontal disease and/or outcome of periodontal treatment. Hence, the comparison of fluorosed versus nonfluorosed cementum is a new area of interest in fluorosis research. Medline search using keywords fluorosed and nonfluorosed cementum does not reveal much data. Hence, the present study aims to assess and compare the mechanical properties (microhardness) of fluorosed versus nonfluorosed dental cementum using Vickers hardness tester (VHN) (Mitutoyo hardness testing machine).

Materials and Methods

A total of 24 healthy nonfluorosed and fluorosed orthodontically extracted premolars were obtained from the Department of Oral and Maxillofacial Surgery, College of dental sciences, Davangere. Participants with the age group of 18–25 years of both the sexes were included in the study. Written consent was obtained from all subjects, and ethical clearance was obtained from the Institutional Review Board (IRB; Ref No. CODS/2184) of College of Dental Sciences, Davangere, Karnataka, according to Rajiv Gandhi University of Health Sciences, Karnataka protocols.

The extracted teeth were required to meet the following inclusion criteria: fully erupted, extracted nontraumatically due to orthodontic reasons, no history of recent periodontal instrumentation or dental prophylaxis, for fluorosed teeth; the fluorotic enamel stains was confirmed by the clinical examination and history of the subjects hailing from natural high water fluoride areas in and around Davangere (fluoride concentration >1.5 ppm). The exclusion criteria were: teeth with proximal caries extending to the cementum, fillings extending beyond cementoenamel junction, and intrinsic stains caused by other reasons such as porphyria, erythroblastosis fetalis, tetracycline therapy.^[4] Sample size was 11.72 using n = z ²^σ/(x₁− x₂)².

Procedural steps

Collection of teeth specimens

Healthy nonfluorosed and fluorosed teeth were collected and were immediately washed in running tap water and stored in bottles containing 0.9% saline.^[4]

Assessment of microhardness (mechanical property) of cervical cementum using Vickers hardness tester

For the evaluation of microhardness, tooth sections (premolars) embedded in acrylic were positioned in an adjustable VHN (Mitutoyo hardness testing machine). The clamp was locked into a position so that the exposed surface stayed parallel to the horizontal plane, immobilizing the specimen completely during the measurement, where Vickers microhardness measurements were taken at room temperature. Penetrations on cervical third of cementum were carried out with the Vickers instrument. Care was taken to avoid the possible interference of one penetration being too close to the other. Using a light microscope coupled to the microhardness tester each of the markings made with the spherical drill was located. Next, maintaining the alignment with these markings, penetrations on cervical third of cementum were carried out with the Vickers instrument. The penetration diagonals were measured. Moreover, through these values, the microhardness of that spot was calculated. For this experiment, the microhardness tester was calibrated at 50-gauge applied for 30 s for teeth.^[3]

Statistical analysis

The data obtained from the microhardness assessment was subjected for statistical analysis. Data were compiled on MS-excel sheet. Mean and standard deviation of fluorosed and nonfluorosed cementum was analyzed using SPSS 17.0 (Chicago, US: SPSS Inc.). P< 0.05 was considered statistically significant. P > 0.05 = Not significant; P< 0.01 = Highly significant.

Results

A total of 24 healthy nonfluorosed and fluorosed orthodontically extracted premolars were collected to assess and compare the microhardness of fluorosed versus nonfluorosed cementum using VHN. The results of this study are interpreted in [Table 1].

Table 1: Hardness of cervical cementum of nonfluorosed and fluorosed teeth

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The results showed that the hardness values varied between 52.6 VHN and 75.7 VHN for the healthy nonfluorosed cervical cementum sections and for the fluorosed cervical cementum sections, the values ranged from 29.3 VHN to 65.9 VHN. The mean hardness of the fluorosed cementum was lower than nonfluorosed cementum but was not statistically significant.

Discussion

Various methods for the assessment of microhardness (mechanical property) of healthy and diseased teeth done by various authors were using Brinell hardness number, VHN, Knoop hardness number (KHN), nanoindentation. In this study, assessment of microhardness of fluorosed and nonfluorosed teeth was done using VHN.

Measurement of hardness in the tooth is not easy. However, because the structures that enamel and dentin present, prisms running from the enamel-dentin junction (EDJ) to the surface in the case of enamel and a heterogeneous composite material in the case of dentin,^[5],[6],[7] it is easy to imagine that their hardness values are different, even from one site to other inside enamel and dentin themselves; and that they would be chemically dependent.

In de- and re-mineralization experiments, hardness testing, together with intraoral models, has great importance.^[8] A variety of methods have been used to test the hardness of human tooth, including abrasion,^[9] scratch,^[10] and indentation techniques ^[11] These tests have shown considerable local variations in enamel and dentin hardness, the currently preferable methods include using a microscratch or micro-indentation, where the Knoop diamond indenter is commonly used.^[8] Recently, nano-indentation using atomic force microscopy was used to measure the hardness of dentin. In tooth hardness studies, a square shape has to be always conserved. Therefore, the Vicker indenter is more useful than the Knoop's because indentations, which produce errors in hardness measurements, are easily detected and close to the outer surface and the EDJ a small elongation of the diagonals of the indentations, that produce errors in hardness measurements, is easily detected. Therefore, it is proposed that the Vicker indenter can be used with good results, in the tooth hardness studies.^[12]

In the current study, in nonfluorosed cervical cementum, hardness was 60.40 ± 6.23 microns as compared to 57.7 ± 9.4 microns fluorosed cervical cementum. As per the author's knowledge, this study presents the difference in hardness of cervical cementumin nonfluorosed and fluorosed teeth for the first time in literature.

There is a paucity of information on hardness values for cementum. Hodge and McKay in 1933 used a scratch test and reported that cementum had a mean range of 85–90 Bierbaum hardness numbers.^[13]

Ichiro and Nihei in 1959 using a VHN, observed mean hardness values for adult human cementum to range from 14 to 21 diamond pyramid hardness numbers. No data were presented regarding the anatomical location or periodontal condition of the teeth studied.^[14]

Rautiola and Craig in 1961 conducted a study on freshly extracted 18 teeth to evaluate the microhardness of cementum of normal teeth and teeth exposed to the periodontal disease. It was observed that the mean KHN for unexposed cementum was 39.3 compared to exposed cementum which was 39.6, indicating that the microhardness was unaltered by exposure to a periodontal pocket or by exposure following the gingival recession.^[15]

Cirano et al. in 2004 conducted study on 30 canines using VHN and reported the mean microhardness of cementum was 19.70 VHN.^[3]

Sundaram et al. in 2014 analyzed the hardness and modulus of elasticity of cervical third of cementum of Mandibular canines, first, second premolar and Maxillary first, second premolar, first molar (n = 20) using nanoindentation. The hardness and elastic modulus of cementum were 0.720 ± 0.305 GPa and 15.420 ± 3.902, respectively.^[16]

The studies related to the objective of our study is not comparable directly as their subjects age, sex, water fluoride exposure, and methodology vary and differ from this study.

Most of the studies assessing cementum hardness in the English literature have done so using micromechanical testing techniques. No statistically significant difference was found on the evaluation of microhardness of cementum in teeth with or without periodontal involvement using microindentation technique. Furthermore, healthy human dental cementum of premolar teeth showed no significant differences in the elastic modulus and hardness of the cementum between the buccal and the lingual surfaces or between the upper and the lower teeth, when analyzed using microindentation.^[16]

Cementum was found to have an average hardness of 40 KHN compared to the central crown and root dentin of 69 KHN. No difference was observed in hardness between inner and outer cementum. A narrow peripheral band of dentin underneath cementum had a comparable hardness to cementum and was much softer than the adjacent central dentin. Preliminary measurements indicated that calculus was much harder than cementum and somewhat harder than dentin.^[15]

Factors influencing hardness could be such as histology features, chemical composition, specimen preparation, and load and reading error in indentation length.^[12] The elastic recovery of indentations placed in cementum obliterated within several hours while they remained nearly intact for 6 months in dentin. It is apparent that even though clinicians have long maintained that cementum which is exposed to periodontal pockets is soft, the results of the microhardness studies of cementum seem to dispute this contention. There appears to be no difference in hardness of healthy and diseased teeth.^[15] This particular report is contradicting the strong belief of soft cementum in periodontitis is highly questionable. Further studies are strongly required to comprehend this particular report.

The clinical transfer of cementum hardness measurements are related to calculus removal during scaling and root planing- the limited measurements on the hardness of calculus indicate that this material is somewhat harder than dentin and much harder than cementum. The average value of 86 KHN for calculus when compared to 39 KHN for cementum may explain why root hypersensitivity exists following periodontal treatment. In attempting to remove the hard calculus, the soft cementum and peripheral dentin perhaps are removed. This would very likely be the case if root planing were carried out as a clinical procedure with the intent of achieving a hard root surface since the roots of all teeth are relatively soft through the entire cementum and into the dentin to an average depth of 100 microns. Thus, the long-standing clinical concept that the “soft” outer cementum should be planed away needs further evaluation.^[15]

Conclusion

The microhardness of fluorosed cementum was found to be lower (57.7 ± 9.4) than nonfluorosed cementum (60.40 ± 6.23).

The clinical importance of this study is that clinicians need be aware of this difference during periodontal, orthodontic, caries treatment, crown procedures, and implant therapy.

The possible shortcoming of this self-funded pilot study is the limited number of specimens. Further studies can be done using nano-indentation method, histologic, and mineral content of dental cementum.

Acknowledgment

The authors would like to thank Mr. Laxman, Laxmi foundry, Harihar and Mr. Mohan, GMIT, Davangere for technical assistance.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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