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 Table of Contents  
ORIGINAL ARTICLE
Year : 2018  |  Volume : 7  |  Issue : 2  |  Page : 65-69

Predilection of chewing side preferences and clinical assessment of its impact on temporomandibular joint


Department of Prosthodontics, C.K.S. Theja Institute of Dental Sciences and Research, Tirupati, Andhra Pradesh, India

Date of Web Publication1-Nov-2018

Correspondence Address:
Dr. S Neeharika
Flat No. 201, Sri Padmavathi Residency, Postal Colony, Renigunta Road, Tirupati - 517 501, Andhra Pradesh
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jdas.jdas_29_17

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  Abstract 


Statement of the Problem: Normal mastication in humans generally favors one side and then the other, but most people chew more on a particular side, which means they have a preferred chewing side (PCS). The relationship between the use of one habitual chewing side and the peripheral factors involved in temporomandibular disorders (TMDs) is not understood yet. Aims and Objectives: The objective of the study is to explore the effect of chewing side preference on temporomandibular joint (TMJ) in adult population. Methods: One hundred and seventy healthy dentate subjects (148 female and 22 male) were selected and clinically examined for this cross-sectional study. Chewing side preference test and TMJ clinical examination were conducted. Subjects were classified into unilateral and bilateral chewers, signs and symptoms of TMDs were recorded. Results: Statistical analysis was performed to evaluate the difference between the subjects regarding preferable chewing side, distribution of subjects with respect to signs and symptoms of TMDs, and frequency of symptoms in habitual chewers using Chi-square test, at 5% significance level. The results showed that among all the subjects, 80% preferred unilateral chewing side and there was a significant correlation with asymmetric factors of TMJ with masticatory side. Conclusion: Within the limitations of the study, it may be concluded that the presence of a PCS affects the morphology and parameters of TMJ. This signifies that it is not only sufficient enough to maintain anatomic health but also dynamic and functional factors should be considered to avoid TMDs.

Keywords: Masticatory laterality, preferred chewing side, temporomandibular disorders


How to cite this article:
Padmaja B I, Neeharika S, Bindu G H, Babu N S, Madhulika S D. Predilection of chewing side preferences and clinical assessment of its impact on temporomandibular joint. J Dent Allied Sci 2018;7:65-9

How to cite this URL:
Padmaja B I, Neeharika S, Bindu G H, Babu N S, Madhulika S D. Predilection of chewing side preferences and clinical assessment of its impact on temporomandibular joint. J Dent Allied Sci [serial online] 2018 [cited 2018 Nov 20];7:65-9. Available from: http://www.jdas.in/text.asp?2018/7/2/65/244759




  Introduction Top


The principle objective of prosthetic rehabilitation is to provide sufficient dental units for occlusal stability and mastication.[1] Mastication is a combined voluntary and involuntary act and as the masticatory act progresses, it becomes involuntary and independent on complex peripheral and central neural mechanisms.[2] In a majority of human physical activity, there exists a preference in the use of one side of the body, be it with hands, feet, or eyes.[3] Similarly, mastication can take place bilaterally at the same time, on the right and left side alternatively or consistently on one side, which is referred to as masticatory laterality or preferred chewing side (PCS).[4]

The factors that determine the PCS have not been identified yet.[2] Several discussions are still going on whether the PCS is determined in the central nervous system or is rather related to various peripheral factors such as occlusion and food texture.[3]

According to Reinhardt et al., unilateral mastication is an expression of impaired function and has been proven to be associated with signs and symptoms of temporomandibular disorders (TMDs), it is of interest that how prevalent masticatory preference patterns are in population and whether unilateral chewing is a form of functional asymmetry related to temporomandibular joint (TMJ).[2]

As PCS is suggested to be related to an asymmetry of occlusal, articular, and temporomandibular parameters, the aim of this study was to evaluate the prevalence of a PCS in a population representative sample and to determine the impact of the relationship between chewing side preference and signs and symptoms of TMD.


  Materials and Methods Top


Participants and study design

Postgraduate and undergraduate students with natural dentition were invited to participate in this cross-sectional study. A sample of 170 subjects (148 female and 22 male) with their ages ranging between 18 and 30 with a median age of 24 were selected. The study participants were selected based on the following inclusion criteria: both genders, age within the range of 18–30 years, not having been undergone orthodontic or functional jaw orthopedic treatment, good general health, without neurological disorders, subjects at the permanent dentition stage with ≥24 permanent teeth (excluding teeth extracted after surgical and/or orthodontic indications), without removable prosthetic restorations in one or both jaws. The exclusion criteria were subjects complaint of toothache, tenderness to percussion, and with the presence of orofacial muscle pain. The investigation was performed in accordance with the principles of the Declaration of Helsinki.

Preferred chewing side test

The study subjects were informed that the aim of this study was the evaluation of mastication rather than the PCS as the item of interest to avoid bias and awareness of chewing side. Subjects were instructed to sit on the dental chair in an upright position. Three markings were made on the subjects' facial skin, one at the tip of the nose, one just below the center of the lower lip, and one on the chin. The subjects were asked to move their heads as little as possible during the recording session so that the three marked dots were aligned vertically during each chewing trial, to help distinguish the path of chin movement.[2]

The PCS was evaluated using a test described by Mc Donnel et al., according to which subjects were given a piece of gum and start chewing, after a 15 s time interval, they were asked to stop chewing and to open mouth to observe on which side the gum was positioned (right or left). This procedure was repeated six times with a time interval of 5 s between procedures, totaling seven strokes recorded as right or left.

The PCS of the subjects were classified according the following criteria:

  • Consistent preferred chewing side (CPCS) - 7/7 strokes on the same side
  • Predominant preferred chewing side (PPCS) - 5/7 or 6/7 strokes on the same side
  • Observed preferred chewing side (OPCS) - 5/7, 6/7, or 7/7 strokes on the same side.


According to the Mc Donnell et al. classification, all subjects with CPCS or PPCS had an OPCS; hence, OPCS to the right or left corresponds to the PCS to right or left.[5]

Temporomandibular joint clinical examination

The clinical examination of TMD signs included the following parts:

  1. The orofacial muscles (masseter, temporal, medial & lateralpterygoid), suboccipital, and sternocleidomastoid muscles were palpated were palpated bilaterally to evaluate pain upon palpation. To evaluate pain or discomfort of the lateral pterygoid, an isometric contraction test was performed
  2. Deviations from mouth opening (more than 2 mm from the medial plane), limitation during mouth opening, and restricted lateral mobility of the mandible (<5 mm) were recorded with a millimeter ruler. The mandibular opening for each patient was recorded as follows: straight opening with no deviation, deviation to the right side, or deviation to the left side. A patient's tendency to deviate toward any side was regarded as positive diagnostic sign
  3. The occurrence of TMJ pain upon movements or lateral pressure cranially and dorsally was examined while the mouth was slightly open and condyles were palpated. Subjects expressed their perception as “indolent/painless,” “uncomfortable,” or “painful”
  4. For TMJ auscultation, the mouth was opened and closed, both TMJs were simultaneously palpated for popping or scraping sounds. TMJ clicking was categorized as clicking during opening or clicking during closing. Clicking of the TMJ, either unilateral or bilateral, was recorded
  5. The participant was asked to open his/her mouth as wide as possible to measure maximal active mouth opening. Maximal passive mouth opening was measured after the application of downward pressure on the mandible by the second and third fingers of the participant. The vertical distance between the upper and lower teeth was measured with a ruler.


Statistical analysis

To evaluate the difference between the participants regarding the presence of a preferable chewing side and their frequency of TMD signs and symptoms, Chi-square test was used. A P ≤ 0.05 was considered as significant difference. All statistical analysis were performed using the Statistical Package for Social Sciences (SPSS) for windows, version 15.0 (SPSS Inc., Chicago, IL, USA).


  Results Top


Distribution of chewing side preference

Based on the chewing laterality criteria, 81 subjects had a preferable chewing side (37 preferred right and 44 preferred left side) and 89 subjects chewed bilaterally [Table 1].
Table 1: Distribution of chewing side preference

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Masticatory laterality and gender distribution

Results revealed no statistical difference in the distribution of males and females between unilateral or bilateral chewers [Tables 2].
Table 2: Gender distribution in masticatory laterality

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Temporomandibular disorder symptoms and masticatory laterality [Table 3], [Table 4], [Table 5], [Table 6]

Frequency of temporomandibular disorder signs and symptoms in unilateral and bilateral chewers

The most frequent symptom observed in unilateral chewers was clicking sounds (60.5%), followed by deviations (32.1%), TMJ pain (7.4%), limited mouth openings (4.9%), and muscle pain (1.2%). There was a significant difference in the occurrence of clicking sounds and mouth deviations observed in the unilateral chewer group compared with the bilateral chewer groups with a P = 0.0 and also there is a significant correlation of unilateral right sounds, P = 0.004; left and right deviations, P = 0.001 and 0.0, respectively, in unilateral chewer group when compared to bilateral.
Table 3: Distribution of participants with signs and symptoms with respect to temporomandibular disorder (n=170)

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Table 4: Distribution of participants with symptoms with respect to temporomandibular disorder (n=118)

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Table 5: Distribution of temporomandibular disorder signs and symptoms in unilateral and bilateral chewers

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Table 6: Distribution of temporomandibular disorder signs and symptoms in unilateral right, unilateral left chewers and bilateral chewers

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  Discussion Top


The results of the present study show that preferred unilateral chewing is present in about 80.2% of the study participants, especially to the left (54.3%) and right (45.6%).

To our knowledge, the effect of gender on masticatory laterality has not been clearly addressed in the literature. Our results also revealed that there was no statistical difference in the distribution of chewing side preference between genders.

There was a marked preference for the masticatory side with a significant correlation with some asymmetric factors of the orofacial system such as subjective bilateral clicking sounds of TMJ and total deviations of mouth which is an indication of the existence of something, especially of an undesirable situation. Furthermore, stating PCS may be associated with signs and symptoms of TMD.

To assess the PCS, the direct method of visual observation and indirect methods by electronic programs such as cinematography, kinesiography, and computerized electromyography can be used. The direct method consists of the visual observation of the side that the bolus is positioned. Hence, this study explored the feasibility of using a simple, practical, fast, and inexpensive method to be used clinically to evaluate masticatory preferences. Several authors noted that there were no significant differences between the direct method and indirect method to determine the PCS.[2]

Several nonepidemiological investigations have been made concerning masticatory laterality and have found marked preference on the right side. Delport et al. suggested that the preference of the right side as an underlying neuromuscular mechanism, despite of stated pain or other impairments, might be due to control of central neural system.[4] In our study, majority of the unilateral chewers preferred left side which could be varying with other authors due to sample size selection and various other reasons.

According to Nissan et al., the chewing side preference distribution characteristics resembled those of the other hemispherical lateralities. Missing teeth, implant supported restoration, and complete dentures did not affect the chewing side preference.[1]

According to the relation of missing teeth to the chewing side preference showed no effect even when teeth were missing on the side of the other preferred lateralities, which presents a strong argument that chewing side preference is centrally controlled.[1],[5]

Reinhardt et al. proved that signs and symptoms of TMD have been associated with PCS, but no obvious pattern for the localization of the symptoms has been found in those who have a PCS.[6] With the study by Miyake,[1] a significant association between clinical/anamnestical unilateral TMJ pain and a PCS was found.

Patients with unilateral TMJ pain (clinical and subjective) preferred significantly one side for chewing. Due to exclusive unilateral mastication, there was significant differences in bony morphology of TMJ with reduced joint spaces, width of condylar neck, and changes in inclination of articular eminence between opposing TMJs.[7]

According to Minagi, the occurrence of TMJ pain in the nonchewing side joint might be explained by increased loading of this joint as a consequence of chewing on the contralateral side exclusively. The balancing joint is more loaded during function than the working one and exclusively unilateral mastication can change the structure of the condylar cartilage.[1]

Impaired efficiency could be expected from buccal malocclusions because of the reduced chewing area, unilateral cross bite, buccal nonocclusion, and lateral open bite. However, these were not the factors that influenced the subjects' preference on one side.

Wostmann et al. evaluated the association between the prosthetic restoration and chewing side preference. They showed that simple acrylic-based removable partial dentures are significantly associated with unilateral chewing which can be assumed that the less stable a replacement is, the less masticatory efficiency can be developed with it. He also explained that the induced chewing asymmetry leads to structural changes that might be the explanation for the connection between RPD and TMD.[4]

Metal-based partial dentures, telescope crown-retained dentures, and fixed restorations or dentitions without prosthetic restoration do not generally influence people to chew asymmetrically, which is probably due to their high stability and pressure resisting ability.

Clinical implications

The findings of this study suggests an additional element namely chewing side preference to be checked and made aware during diagnosis & treatment planning. From therapeutic point of view, rehabilitation should ideally prioritize the chewing function on the previously nonchewing and unaffected side to improve the TMJ dynamics and remodeling.[8] This may have both a potentially detrimental effect from occlusal loading and would also appear to necessitate ensuring adequate support for restorations of dental units on the PCS. Biomechanical factors such as reduced use of cantilevers, greater attention to crown root ratio, and restoration of missing teeth assume a greater significance on this side. Restoration of missing dental units on the preferred side would improve chewing efficiency and ease the occlusal burden on the existing teeth.

Limitations of the study

  1. The PCS habit does not typically allow us to discriminate healthy subjects from those with TMDs; however, it might allow us to differentiate the symptomatic side of the subject
  2. Since the study is a cross-sectional, it is advised to screen larger sample for more internal validity.



  Conclusion Top


Within the limitations of this study, the data suggested that people with masticatory laterality may be more susceptible to TMD and are more likely to have unilateral TMD. Clicking sounds and joint deviations are the symptoms most closely associated with TMD and the choice of PCS. The unilateral chewing pattern cannot be an acceptable standard as it plays a significant role in periodontal tissue stability, occlusal harmony, orofacial muscle, and anatomy of TMJ, and further longitudinal studies are essential to support this factor. Hence, evaluation of chewing side preference should be considered a part of routine dental examination.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Nissan J, Gross MD, Shifman A, Tzadok L, Assif D. Chewing side preference as a type of hemispheric laterality. J Oral Rehabil 2004;31:412-6.  Back to cited text no. 1
    
2.
Alkhiary YM, Zawahary MM, Moubarak AH. Masticatory laterality: Parameter for evaluating TMD. J Appl Sci Res 2013;9:2890-900.  Back to cited text no. 2
    
3.
Lamontagne P, Al-Tarakemah Y, Honkala E. Relationship between the preferred chewing side and the angulation of anterior tooth guidance. Med Princ Pract 2013;22:545-9.  Back to cited text no. 3
    
4.
Diernberger S, Bernhardt O, Schwahn C, Kordass B. Self-reported chewing side preference and its associations with occlusal, temporomandibular and prosthodontic factors: Results from the population-based Study of Health in Pomerania (SHIP-0). J Oral Rehabil 2008;35:613-20.  Back to cited text no. 4
    
5.
Barcellos DC, Goncalves SE, Silva MA, Batista GR, Pleffken PR, Borges AB, et al. A comparison of methods used to determine chewing side prefernce in decidous, mixed and permanent dentitions. Braz Dent Sci 2013;16:66-72.  Back to cited text no. 5
    
6.
Reinhardt R, Tremel T, Wehrbein H, Reinhardt W. The unilateral chewing phenomenon, occlusion, and TMD. Cranio 2006;24:166-70.  Back to cited text no. 6
    
7.
Jiang H, Li C, Wang Z, Cao J, Shi X, Ma J, et al. Assessment of osseous morphology of temporomandibular joint in asymptomatic participants with chewing-side preference. J Oral Rehabil 2015;42:105-12.  Back to cited text no. 7
    
8.
Santana-Mora U, López-Cedrún J, Mora MJ, Otero XL, Santana-Penín U. Temporomandibular disorders: The habitual chewing side syndrome. PLoS One 2013;8:e59980.  Back to cited text no. 8
    



 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]



 

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