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 Table of Contents  
ORIGINAL ARTICLE
Year : 2018  |  Volume : 52  |  Issue : 6  |  Page : 151-156

Influence of malocclusion on masticatory sounds: A In vivo study


1 Reader, Departments of Orthodontics and Dentofacial Orthopaedics, Sri Venkateswara Dental College and Hospital, Chennai, Tamil Nadu, India
2 Intern, Department of Orthodontics, Sri Venkateswara Dental College and Hospital, Chennai, Tamil Nadu, India
3 Head of Department, Department of Orthodontics, Sri Venkateswara Dental College and Hospital, Chennai, Tamil Nadu, India
4 Prof., Departments of Orthodontics and Dentofacial Orthopaedics, Sri Venkateswara Dental College and Hospital, Chennai, Tamil Nadu, India

Date of Submission16-May-2018
Date of Acceptance26-Oct-2018
Date of Web Publication7-Dec-2018

Correspondence Address:
Dr. Umarevathi Gopalakrishnan
No. 6, R1, VRISA, 3rd Main Road, 4th Cross Street, LH Nagar, Adambakkam, Chennai - 600 088, Tamil Nadu
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jios.jios_88_18

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  Abstract 


Background: Orthodontic correction is usually focused on dental esthetics; however, masticatory function is an important parameter to assess the success of treatment. The main objective of this study is to determine if an association exists between malocclusion and chewing sounds, after being assessed with three different food types. How far a malocclusion alters an individual's chewing nature can aid us in assessing the potential of teeth alignment in mastication and the consequence of orthodontic correction on the same. Methodology: The study was conducted on three groups of patients (Class I normal occlusion, Class I with increased overjet, and Class II div 1). The patients were asked to chew three types of food items; apple, biscuit, and peanut. The recordings were taken inside an acoustically treated soundproof box using an AKG HC 577 L microphone with a sampling frequency of 44.1 kHz in mono with 32 bits per sample. The recordings were analyzed using WavePad FFT software in a Mac laptop and plotted as a spectrogram using the Hanning window function. Results: The results showed that there was no significant difference between the groups for all the three types of food materials. Conclusion: The results of this study showed insignificant association between malocclusion and masticatory sounds. A more comprehensive study with a larger sample size will be needed to analyze the results further.

Keywords: Frequency and intensity of sound, masticatory sounds, sound intensity


How to cite this article:
Gopalakrishnan U, Abdullah F, Nafi FF, Mahendra L, Madasamy R. Influence of malocclusion on masticatory sounds: A In vivo study. J Indian Orthod Soc 2018;52, Suppl S2:151-6

How to cite this URL:
Gopalakrishnan U, Abdullah F, Nafi FF, Mahendra L, Madasamy R. Influence of malocclusion on masticatory sounds: A In vivo study. J Indian Orthod Soc [serial online] 2018 [cited 2018 Dec 16];52, Suppl S2:151-6. Available from: http://www.jios.in/text.asp?2018/52/6/151/247063




  Introduction Top


The very first step in the process of digestion is mastication where the food is physically broken down to smaller particles by the teeth thereby facilitating enzymatic processing during the latter stages of digestion. The set of movements from the point of ingestion till swallowing is known as the masticatory sequence.[1],[2] Several factors are known to influence this function such as size of tooth, number of functional tooth units, occlusal contact area, and malocclusion.[3],[4],[5],[6] Literature review points that the mastication process can be measured in many ways; by assessing the particle size distribution of food when chewed (masticatory performance), by counting the number of masticatory strokes (masticatory efficiency), electromyography of masticatory muscles, swallowing threshold, and visual analog scale of occlusal contacts.[7],[8],[9],[10] However, little emphasis has been given to the sounds produced during mastication which is another facet for an individual to corroborate his/her own oral function. An individual's perception of food is not only driven by taste or smell but also from the masticatory noise from food breakdown.[11] However, these sounds of mastication are sometimes undesirable especially during public gatherings often adding to the social stigma. This can have an influence on one's social and psychological “functioning.”[12],[13] This is seen, especially in adolescent individuals, who refrain from eating in public or under eat thus decreasing the quality of life.

Literature review showed many studies assessing the sounds of mastication to analyze the texture of food, quality of chewing, and masticatory efficiency; however, there are none relating the sounds of mastication to malocclusion.[14],[15],[16],[17],[18],[19],[20] Watt was first to depict the use of sound for oral diagnosis and also stated on the scrutiny required in this subject.[21] Gnathosonic studies indicated a relationship between the sounds of tooth contact to nature of the tooth contact and the quality of the muscle activity during mastication.[22],[23],[24] Lee et al. in his article stated that sound analysis depicted two important findings; first was the decrease in the total sound level as the chewing progressed and the second was the higher sound levels observed in open mouth chewing than closed mouth chewing.[25] Drake in 1963 was the first who did an introductory study in food crushing sounds by tape recording and analyzing these sounds regarding amplitude, frequency, and duration.[26] Henrikson et al. concluded in his study that large overjet led to reduced masticatory performance.[27] The association between masticatory sounds and malocclusion still remains an unexplored field. The main aim of this study is to determine if an association exists between malocclusion and chewing sounds assessed with three different food types. How far a malocclusion alters an individual's chewing nature can aid us in assessing the potential of the consequence of orthodontic correction on the same.


  Methodology Top


Extraoral and intraoral examination was performed to ensure the participants met the inclusion criteria of presence of all teeth with or without third molars. Patients with previous orthodontic treatment, reverse/edge to edge overjet, anterior or posterior crossbite, anterior or posterior open bite, bruxism, artificial crowns, temporomandibular joint problems, severe attrition or periodontally compromised dentition were excluded from the study. The power of the study set at 80 determined the sample size to be 20 patients. The study was conducted in three groups of patients, Group 1– Class I with normal overjet, Group 2– Class I with increased overjet, and Group 3– Class II with increased overjet. Institutional ethical approval was obtained IEC/IRb No:SVDC/IRB/4/2017. Informed consent was taken from the subjects after briefly explaining them about the study and associated procedures.

The subjects were asked to chew three types of food items and the recordings taken. Food items are categorized as wet crisp (apple), dry crisp (biscuit), and crunchy (peanuts). For standardization apples and biscuits were cut into pieces of equal size, and peanuts were taken a tablespoon full. The foods were given in same sequence of apple, biscuit, and peanuts. The recordings were done inside an acoustically treated soundproof box [Figure 1] which was constructed based on the mass law of acoustics. A box of the size 55 cm × 55 cm was constructed using acoustic foams to minimize the external noise. A 15 cm × 15 cm opening was made at the bottom of the box and a condenser microphone was placed inside the box on a custom-made stand. The box was clamped to the wall in an isolated room with no windows or any other openings. The door was covered with acoustics foams for further noise cancelation of external environment. Each subject was instructed to have the food item inside their mouth and then place their head inside the box through the window opening at the bottom with their mouth positioned in front of the microphone. Then, he/she is instructed to start chewing the respective food item once the investigator taps their right shoulder. The patients were instructed to raise their right hand once they are done with chewing and before swallowing. In this way, masticatory phase is covered, beginning after intake of food piece but not the swallowing of the bolus. Audio recordings were taken with AKG HC 577 L microphone with a sampling frequency of 44.1 kHz in mono with 32 bits per sample. The recordings are analyzed using Wavepad FFT software in a Mac laptop and plotted as a spectrogram using the Hanning window function. The following features of sound were analyzed – duration of the chewing cycle, sound levels in decibels regarding highest and lowest value and frequency of sound at these sound levels.
Figure 1: Acoustically treated soundproof box

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  Results Top


Dependent variables for each of the three different food groups were computed individually. Data were found to follow nonnormal distribution. Hence, a nonparametric test Kruskal–Wallis one-way analysis of variance was used. Significance was set at P ≤ 0.05.

In the wet crisp category [Table 1], the duration of chewing cycle for Group 1 was 12.3510 s; for Group 2, it was 12.59 s and for Group 3, it was 14.26 s. The sound level recorded for Group 1 had the highest value of −48.8 dB and the lowest value of −119.25 dB whereas for Group 2, the highest value was −49.2 dB and the lowest value −119.6 dB and for Group 3, the highest value was −51.9 dB and the lowest value was −119.05 dB. Frequency at the highest sound level for all three groups was 86 hertz. Frequency at the lowest sound level for Group 1 was 16014 Hz; for Group it was 16073.5 Hz and for Group 3; 16082 Hz. [Figure 2] shows the spectrogram demonstrating the pattern of distribution between intensity and frequency of sounds produced during chewing of wet crisp food.
Table 1: Statistics for wet crispy category

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Figure 2: The spectrogram demonstrating the pattern of distribution between intensity (y-axis) and frequency (x-axis) of sounds produced during chewing of wet crisp food

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In the dry crisp category [Table 2], the duration of chewing cycle for Group 1 was 15.72 s; for Group 2, it was 17.16 s; and for Group 3, it was 16.12 s. The sound level recorded for Group 1 had the highest value of −49.7 dB and had the lowest value of −119.95 dB whereas for Group 2, the highest value was −49.2 Db, and the lowest value was −119.8 dB and for Group 3, the highest value was −48.75 dB and lowest value was −119.1 dB. Frequency at the highest sound level for all three groups was 86 Hz. Frequency at the lowest sound level for Group 1 was 15896 Hz; for Group 2, it was 16046 Hz; and for Group 3; it was 15890 Hz. [Figure 3] shows the spectrogram demonstrating the pattern of distribution between intensity and frequency of sounds produced during chewing of dry crisp food.
Table 2: Statistics for dry crispy category

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Figure 3: The spectrogram demonstrating the pattern of distribution between intensity (y-axis) and frequency (x-axis) of sounds produced during chewing of dry, crisp food

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In the crunchy category [Table 3], the duration of chewing cycle for Group 1 was 16.31 s; for Group 2, it was 19.91 s, and for Group 3, it was 16.77 s. The sound level recorded for Group 1 had the highest value of −47.55 dB and the lowest value of −119.35 dB whereas for Group 2, the highest value was −49.5 dB and the lowest value −119.45 dB and for Group 3, the highest value was −47.9 dB and the lowest value was −119.70 dB. Frequency at the highest sound level for all three groups was 86 Hz. Frequency at the lowest sound level for Group 1 was 15959.5 Hz; for Group 2, it was 15905 Hz; and for Group 3, it was 15857.5 Hz. [Figure 4] shows the spectrogram demonstrating the pattern of distribution between intensity and frequency of sounds produced during chewing of crunchy food.
Table 3: Statistics for crunchy category

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Figure 4: The spectrogram demonstrating the pattern of distribution between intensity (y-axis) and frequency (x-axis) of sounds produced during chewing of crunchy food

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No statistical significance (P < 0.05) was found for all the parameters tested.


  Discussion Top


Chewing is a physiological process wherein the food particles are reduced in size and moistened with saliva to make a bolus that can be easily swallowed. Muscles of mastication are the ones which generate the force for chewing. The tongue, cheeks, and lips also play a major role here as they control and direct the food on to the surfaces of the teeth. People with normal occlusion showed simpler and more regular pattern of chewing cycles whereas those with malocclusions demonstrated chopping, reversed, contralateral, and irregular masticatory strokes. Chewing sound analysis in rodents showed orofacial motor function affected in neurodegenerative disorders.[28] This formed the vindication for our study as poor muscle coordination is most frequently seen in malocclusion.[29] The prevalence of malocclusion was higher in lip incompetence group, and the structure of malocclusion associated with lip incompetence was also significantly different, featuring increased overjet. This formed the basis for grouping the study based on overjet. If a person is going to chew with his mouth closed, the sounds expressed will be less in correlation with Lee's finding.[25] Chewing sounds are air conducted noises or vibration produced due to contact of tooth with food, with the opposing teeth and the movement of the soft tissues during this process. We chose three types of food since the texture of the food also places an important role as specific sounds are produced pertaining to a particular food category.[30] There is some dampening of the crushing sounds by tongue and cheeks. The loudness of a food during chewing depends on the deformation of the inner structure of the food, i.e., cell arrangement, impurities, and existing cracks. Wet crisp materials, for example, apples, are termed wet crisp since the cells contain fluids whereas dry, crisp products, for example, biscuit, have air inclusions. This justifies our choice of three different food materials.[26]

A sound waveform has three basic physical characteristics: frequency, amplitude, and temporal variation. Frequency refers to the number of times per second that the vibratory pattern (in the time domain) oscillates. Amplitude refers to sound pressure. Temporal variation of sound is a function of time that is sound duration. The common measure of sound level is the decibel (dB), in which the decibel is the logarithm of the ratio of two sound intensities.[31] We assessed duration of the chewing cycle, sound intensity, and frequency at highest and lowest intensity. There was no significant association for all the parameters assessed with regard to all groups. The insignificant findings from our study need to be given consideration since they correlate with Profitt's words that “the forces exerted by the masticatory muscles are determined independent of the malocclusion.”[32] Though the systematic review on the influence of malocclusion on mastication infers that malocclusions decrease masticatory performance because of fewer intermaxillary contacts,[33] the parameter used for assessing mastication in all the articles were particle size of food after chewing, electromyography of the muscles and occlusal contacts. None of the studies assessed the association between malocclusion and masticatory sounds. The results are suggestive that interocclusal contacts, and hence, the malocclusion per se is not influencing the sounds produced during chewing. Further detailed analysis involving a greater sample size and taking consideration of other confounding factors such as Hawthorne effect, soft-tissue factors such as lip competence would provide a better insight into the association between malocclusion and masticatory sounds.


  Conclusion Top


The results of this pilot study showed insignificant association between malocclusion and masticatory sounds. A more comprehensive study with a larger sample size will be helpful in analyzing these findings further.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4]
 
 
    Tables

  [Table 1], [Table 2], [Table 3]



 

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