JMBS2013(2-7)

© Journal of Medicine and Biomedical Sciences, ISSN: 2078-0273, Vol. 4. No. 2, 2013

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Toqeer A. Iqbal, Shadab A. Butt, Sh. Hamid. Effect of low frequency noise on cementum of mice and human, a light microscopic study. Journal of Medicine and Biomedical Sciences 2013; 4(2), 42-48. DOI: 10.7813/jmbs.2013/4-2/7

EFFECT OF LOW FREQUENCY NOISE ON CEMENTUM OF

MICE AND HUMAN, A LIGHT MICROSCOPIC STUDY

Toqeer Ahmed Iqbal1, Shadab Ahmed Butt2, Shabnam Hamid3

1MPhil Trainee, 2Head of Anatomy Department, 3Assistant Professor Anatomy Department,

Army Medical College Rawalpindi (PAKISTAN) E-mails: [email protected], [email protected]

DOI: 10.7813/jmbs.2013/4-2/7

ABSTRACT Background: Noise pollution has become one of the common problems of the urban

community of most of the developing countries and it is increasing with time. The study was conducted to evaluate the effects of low frequency noise on the cementum in mice and these effects were compared with those on cementum of human beings living in the noisy environment for a considerable time. Methods: 30 female BALBc mice (Groups A, B and C) and ten healthy human teeth (Group D) were selected and divided into four equal groups. Group A being control and kept in normal environment of animal house, experimental group B was kept in silent condition and experimental group C was exposed to low frequency noise of 200 Hz for three months. Group D comprised of ten healthy human teeth from the persons who were under dental treatment for some other reason, and who were living in noisy area of a metropolitan city for more than ten years. The results of the experimental groups were compared with the control, and with each other. Results: Erosion of cementum was found to be present in all the four groups but significantly more in groups C and D. Conclusion: It was concluded that low frequency noise adversely affects the normal structure of periodontium, both in experimental animals and human.

Key words: Low frequency noise, cementum, periodontal ligament

1. INTRODUCTION Noise pollution remained an important nuisance factor for human through the ages. In ancient

Rome, special laws were formulated to restrict the iron wheeled wagons from travelling at night because these caused disturbing noise while passing on stony passages. Similarly, in Europe, horse riding was banned during night for peaceful night sleep of public. But the quality and magnitude of noise emitted from these ancient sources is far less disturbing than present day noise pollution 1.

Noise pollution has become one of the common problems of the urban community of most of the developing countries. The problem is being increased by industrialization and large infra-structure networks. The sound and noise are same as far as their mechanical properties are concerned. The only difference is that noise is the undesirable sound causing discomfort to the listener 2. It travels in the form of pressure waves through a medium. The speed of propagation depends upon the density and viscosity of the medium

The frequency and intensity of sound are different. The frequency is number of oscillations per second, denoted as Hertz (Hz). The intensity is the loudness of sound and is measured in Decibels (dB). The audible range of frequency is between 20 to 20000 Hz. Infrasound is the frequency below 20 Hz and ultrasound is above 20000 Hz. The term low frequency noise (LFN) is attributed to frequency of ≤ 500 Hz 3, although some authors claim it to be between 20 to 250 Hz 4. Low frequency noise is an essential part of noise generated in daily life by automobiles, heavy machinery, fans, generators and aircrafts.

Cementum is a hard avascular tissue that covers the root of the tooth. It is secreted by cementocytes. Histologically, it is divided in two types. Acellular cementum, which provides attachment for the tooth and consists of mineralized matrix but lacks collagen fibrils and cells. Cellular cementum has an adaptive role in response to tooth wear and tear and movement. It contains cementocytes


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entrapped in mineralized matrix and covers about two third of the root of tooth 5. In human, the thickness of cementum is 50 µm at cervical region and increases apically where it is 200 µm 6. At cervical region of tooth, cementum meets enamel at cemento-enamel junction (CEJ). Cementum resorption is common at cervical region but it often does not involve the underlying dentin and may alternate with periods of regeneration 7, 8.

In rodents, cementogenesis is a complex process beginning with the deposition of a matrix on the dentin surface by Hertwig’s epithelial root sheath (HERS). These cells then migrate from the dental papilla and differentiate into cementoblasts. The matrix they produce surrounds the cells producing cementum, the cementoblasts. In mice, the progenitor cells differentiating into cementoblasts arise from the dental follicle.

The effects of low frequency noise on histomorphology, physiology and biochemical parameters have been studied on different organs and systems of body. Vibroacoustic disease (VAD) is defined as pathology involving whole body in response to chronic exposure to low frequency noise. It is characterized by proliferation of extra cellular matrix without inflammation 9. The cause of injury can be direct vibrational effect, stress, vascular involvement or combination of these factors 3.

Chronic exposure to low frequency noise affects different body systems including endocrine system, cardiovascular system, immune system, reproductive system, vestibular system, respiratory system, central nervous system, digestive system and oral cavity.

1.1. Comparative animal and human studies Mouse attains sexual maturity at the age of five to six weeks in comparison to human at 10 to

15 years. The histological picture of the teeth in mice is similar to that of human 10. A few studies have been done to compare human and animal parameters. The most commonly

used animal is mice 11, but other animals like dog, rabbit and monkeys have also been used. In 1971, Reitan and Kvam 12 studied comparative effects of tooth movement among equal number of human, dogs and rats. The comparative study of structure of human and rat cementum has also been done 13.

It has been postulated that low frequency noise adversely affects normal supportive structure of teeth.

2. MATERIAL AND METHODS The study was carried out in the Department of Anatomy, Army Medical College Rawalpindi, in

collaboration with National Institute of Health (NIH), Islamabad, Armed Forces Institute of Dentistry, Rawalpindi and Dental department, Capital Hospital, CDA, Islamabad. The experiment was carried out with the permission of ethical committee of Center for Research in Experimental and Applied Medicine (CREAM), of the Army Medical College, Rawalpindi. Informed consent was taken from the human taking part in study.

2.1. Groups Thirty adult BALB/c mice, half male and half female, weighing 25-28 grams were used in the

experiment and were kept in controlled environment of Animal house of NIH, Islamabad. They were fed with standard NIH laboratory diet for three months. Mice were randomly divided into three groups (n = 10 animals, half male and half female, in each group).

Ten healthy human teeth were collected from the adult persons, both male and female, living in the noisy areas of Rawalpindi/Islamabad for ten years or more 14. The teeth were extracted for some other indication like alignment or impaction 15.

The animals in control group A were kept in normal environment of animal house, Experimental group B was kept in silent conditions and Experimental group C was exposed to low frequency noise of 200 Hz continuously for three months. The experimental group D comprised of ten healthy human teeth.

2.2. Exposure to LFN Low frequency noise (LFN) of 200 Hz was produced by analogue frequency generator

purchased from local market. The frequency output was confirmed with the help of digital universal frequency counter (Thurlby Thunder, model No TF 830, 1.3 GHz) and oscilloscope (Hitachi VC 6155). The intensity of sound was measured with sound level meter (Radioshack analogue model 33-4050). Frequency and intensity of sound were recorded at start, middle and end of experiment (Figure 1).


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Fig. 1. Photograph of digital frequency analyzer (A) confirming the frequency of analogue frequency generator (B).

2.3. Microscopic Studies

2.3.1. Animals At the end of 90 days, the animals were euthanized. Hemisected mandibles of mice with intact

teeth were fixed in 10 percent formalin 12. 5µm thick sagittal slices were made using rotary microtome. The staining of sections was done with Hematoxylin & Eosin (H&E) for routine histological study 16.

(Figure 2).

Fig. 2. Dissected mandible

2.3.2. Human teeth Teeth were examined after extraction for any deformity, implant or caries in cervical region.

These were fixed in 10 percent formalin and decalcified with 5% nitric acid for two weeks 14. 3 mm thick specimen was taken from apical third of root of human tooth. 5 µm thick transverse sections were made from this specimen 12.

3. RESULTS The animals remained healthy and active throughout the experimental period. The histological

sections of periodontium showed all of its components under H&E stain. 3.1. Group A (Control) The specimens from group A, showed smooth margin of cementum surface with regularly

arranged sharpy`s fibers inserting into it. Only one out of ten specimens showed erosion of cementum (Table 1, Fig 3).


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Fig. 3. Photomicrograph of sagittal section of specimen from group A showing erosion of cementum (single arrow) and decreased density of cells in between the fibres of periodontal

ligament (double arrow). AB: alveolar bone, C: cementum, D: dentin. H&E 40 X.

3.2. Group B (Experimental) In group B, erosion of the cementum was seen in only one out of ten specimens. This incidence

of erosion was seen to be similar to that found in group A but less than groups C and D (Table 1, Fig 4).

Fig. 4. Photomicrograph of specimen from group B showing smooth attachment of periodontal ligament fibres, blood vessels lined up along alveolar bone and

regular margins of cementum and alveolar bone. H&E 40X. 3.3. Group C (Experimental) The specimen of group C showed erosions and distortion of cementum in six out of ten

specimens. These findings were almost same as in group D but the incidence of erosion was less in groups A and B. Great distortion of attachment of periodontal ligament fibers towards alveolar bone and cementum was also seen (Table 1, Fig 5).


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Fig. 5. Photomicrograph of sagittal section of specimen from group C showing erosion of cementum (arrow). AB: alveolar bone, C: cementum, D: dentin. H&E 40X.

3.4. Group D (Experimental) Erosion of cementum was recorded in 5(50%) out of 10 specimens. This finding was same as

that in group C but significantly different from groups A and B (Table 1, Fig 6).

Fig. 6. Photomicrograph of specimen from group D, showing eroded cementum. C: Cementum, D: Dentin, P: Pulp. H&E 40X.

4. DISCUSSION Environmental noise pollution, a form of environmental pollution, is a continuous threat to

normal health and well-being. It is becoming increasingly severe and widespread than ever before, and it will continue to increase in magnitude and severity because of change in life style, increase in population, urbanization, and the associated growth in the use of increasingly powerful and highly mobile sources of noise. It is likely to continue due to sustained growth in highway, rail, and air traffic, which are the important sources of environmental noise

The objective of this study was to see the effects of the low frequency noise on the histomorphology of the periodontium in mice and its comparison with those on human beings exposed to noisy environment. The results of the experimental groups B, C & D were compared with those of control group A, as well as with each other.

Very few studies are available on erosion of dental cementum. Erosion of cementum and enamel has been found in professional wine tasters 17. In present study, all animals remained healthy and active throughout the experimental period. This was same as previous studies conducted on LFN.


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The incidence of erosion of cementum was same (10% of specimens) in control group A and experimental group B. but in experimental group C and D, this erosion increased to 60% and 50% of specimen respectively. The results were statistically significant when group A was compared with groups C and D. Statistically significant results were also found when group B was compared with groups C and D (Table 2). These results are consistent with an earlier study done by Mendes et al 3 in 2007.

Cementum is an avascular tissue that covers the root of the tooth and serves as attachment site for periodontal ligament. With its erosion, this supportive function is lost leading to poor anchorage of tooth with the alveolar socket.

It is clear from above discussion that most of the findings are similar between groups C and D but different from silent group B.. Since group A and D were exposed to normal everyday environment to which low frequency noise is an essential part and group C was exposed to only low frequency noise, it is clear that it is the low frequency component of noise which produces harmful effects on normal health.

Table 1. Comparison of data among groups A, B, C & D

Parameter Group A Group B Group C Group D

Finding % Finding % Finding % Finding %

Cementum erosion Present 10 Present 10 Present 60 Present 50 Absent 90 Absent 90 Absent 40 Absent 50

Table 2. Comparison of p-value among groups A, B, C and D

P-Value: Groups A&B A&C B&C A&D B&D C&D

1

0.01907*

0.01907*

0.05096*

0.05096*

0.00911*

* p value ≤ 0.05 significant

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13. P. Sunita, B. Yu, B. Yun et al. Structure, chemical composition and mechanical properties of human and rat cementum and its interface with root dentin. Acta Biomateriala. 5: 707-718(2009).

14. Li DY JQ. Comparative study on the histomorphology of the JE of human and several laboratory animals. Shanghai Kou Qiang Yi Xue. 13(6): 539-543(2004).

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