correlation between bite force and electromyographic activity in dentate and partially edentulous...

7/27/2019 Correlation Between Bite Force and Electromyographic Activity in Dentate and Partially Edentulous Individuals

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Correlation between bite force and electromyographic activity in dentate

and partially edentulous individuals

Authors:

Lner Botrel ROSA, M.S., School of Dentistry, University of So Paulo (USP)

Ribeiro Preto

Marisa SEMPRINI, D.D.S., Ph.D Professor, School of Dentistry, University of

So Paulo (USP) Ribeiro Preto

Selma SISSERE D.D.S., Ph.D Assistant Professor, School of Dentistry,

University of So Paulo (USP) Ribeiro Preto

Jaime Eduardo Cecilio HALLAK, D.D.S., Ph.D Assistant Professor, School ofMedicine, University of So Paulo (USP) Ribeiro Preto

Valria Oliveira PAGNANO, D.D.S., Assistant Professor, School of Dentistry,

University of So Paulo (USP) Ribeiro Preto

Simone Cecilio Hallak REGALO, D.D.S., Ph.D Assistant Professor, School of

Dentistry, University of So Paulo (USP) Ribeiro Preto

Correspondence:

Simone Cecilio Hallak Regalo

[email protected]

Department of Morphology, Stomathology and Physiology, Faculty of Dentistry of

Ribeiro Preto, University of So Paulo.

Avenida do Caf s/n Ribeiro Preto, CEP 14096-030, So Paulo, Brazil.

Tel.: 55 16 36024015 Fax: 55 16 36330999

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Abstract

Dental absence interferes in the physiological functioning of the

masticatory system, promoting occlusal and functional alterations. The purpose

of this study was to verify maximal bite force and maximal bite force correlated

with electromyographic activity in 14 partially edentulous and 14 dentate

individuals.

Bite force in right and left molar and incisor regions were registered using

a dynamometer with capacity of up to 1000N, adapted for oral conditions and at

the same time electromyography was performed using Myosystem-Br1 with

electrodes positioned on right and left masseter and temporalis muscles, and one

reference electrode on the frontal bone. The highest value out of three recordings

was considered the individuals maximal bite force. Statistical analysis of the biteforce data was performed by means ofttest and Pearsons bivariate correlation

test was used for the analysis between bite and electromyographic activity using

SPSS 12.0 software.

Dentate individuals showed greater maximal bite force in the three

regions. Correlations between electromyographic activity and bite force in the

dentate group obtained positive coefficients for every muscle in the right molar

region, for the left temporalis in the left molar region, and for every muscle in the

incisive region. For the partially edentulous group, only the left temporalis muscle

presented a positive correlation in the right molar region, there was positive

correlation for the right masseter and right and left temporalis in the left molar

region, and, in the incisive region, every muscle presented negative correlation.

These data evidence the strong influence of dental loss over the maximal

bite force and small correlation between bite force and electromyographic

activity.

Key words: bite force, electromyography, correlation, tooth loss, masticatorymuscles

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Introduction

Dental loss leads to important changes in the masticatory system, which

affects the bone, the buccal mucosa and the muscular function. The alveolar

bone tends to reabsorb without the occurrence of new bone formation and the

mucosa presents a decreased number of receptors, thus diminishing the number

of afferent inputs (13).

The contact between superior and inferior teeth in different functions is

firstly monitored by the mecanoreceptors in the periodontal ligament. The

stimulus of the afferent sensorial inputs sends information to synapses, resultingin afferent responses and triggering muscular activity. When a patient loses one

or more teeth, there is loss of function, loss of the periodontal ligament and its

receptors, and aesthetic impairment (5).

Current research is concerned in determining the bite force in healthy

human beings as well as in those with diverse alterations, aimed at assessing

and understanding the functionality of the masticatory system (7,9,10). Bite force

is intimately related to mastication and is determined by the jaw elevator muscles

and regulated by the nervous, muscular, skeletal, and dental systems. Thus, the

condition of these systems will directly influence the capacity to masticate and

bite (18). The determination of maximal bite force levels has been used in

dentistry with the aim of understanding biological factors such as the

craniomandibular anatomy, neuromuscular mechanisms, masticatory efficiency,

and muscular strength (11, 14).

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The quantitative evaluation of the strength of jaw elevator muscles is a

well-known clinical parameter. Significant correlations between bite force and

facial morphology have been found and researchers agree that the former is

influenced, among other factors, by ones dental condition (4). According to

Gibbs et al. (6), in individuals with posterior dental loss, there is an increase in

the load transmitted to the remaining teeth, reducing the bite force in order to

diminish the stress on these teeth, consequently reducing the muscular strength

as well.

Maximal occlusal force can provide essential information to helpestablish appropriate diagnoses concerning the masticatory function (12).

Electromyography has been used for analysis of the implications of functional

disorders in the masticatory musculature, being both a research instrument

employed as an evaluation procedure and a follow-up tool for treatment (16, 17).

The assessment of the myoelectric activity in masticatory muscles is becoming

increasingly useful for dentists, furthering the knowledge on these muscles

performance, on the movements of regulatory reflexes, and on the changes in

muscular patterns. Given the importance of the masticatory musculature on the

several functions of the stomatognathic system, the proposal of this work was to

investigate maximal bite force and its correlation with the electromyographic

activity in partially edentulous individuals compared to dentate individuals,

identifying to what extent dental loss may influence strength acquisition and

electromyographic activity.

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MATERIAL AND METHOD

Participants

Twenty-eight subjects of both genders took part in the study, enrolled intwo groups. The first, comprising 14 partially edentulous individuals (minimal

absence of 10 posterior teeth), recruited at the Removable Partial Prosthesis

Clinic of the Ribeiro Preto College of Dentistry of the University of So Paulo,

with mean age 35,0 5 years; and the second group consisting of 14 complete

dentate individuals with mean age of 30,0 5, selected among the students,

employees and faculty of the Ribeiro Preto College of Dentistry, all considered

suitable according to the exclusion/inclusion criteria of the research. The

volunteers were fully informed about the experiment and agreed to participate

providing signed informed consent for Electromiography research according to

resolution 196/96 of the National Health Council Brazil, approved by the Ethics

Committee of the Ribeiro Preto College of Dentistry of the University of So

Paulo, process number 2005.1.432.58.6.

Exclusion Criteria

The selection of the sample and the inclusion/exclusion criteria were

determined through anamnesis and clinical exams. The anamnesis interview

provided information on personal data, medical records, dental history, presence

of parafunctional habits, and possible symptoms of temporomandibular

dysfunction. The items used as exclusion criteria were the presence of local or

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systemic-originated disorders which may impair the craniofacial growth or the

masticatory system, such as neurological disorders, cerebral palsy, among

others; use of medications that can interfere, directly or indirectly, on muscular

activity, such as antihistamines, sedatives, cough syrups, homeopathic remedies

or other drugs with depressive action on the Central Nervous System; treatments

that can interfere on muscular activity, directly or indirectly, during the period of

the study, such as orthodontic treatments, phonoaudiological therapy, and

otorhinolaryngologic treatment.

Seventy-five partially edentulous individuals were evaluated, and 14 wereselected. In order to be included in the sample, the subjects had to present

absence of the first superior and inferior molars, where the bite force apparatus

was placed. Among partially edentulous individuals in the Brazilian population

these are the teeth with the highest rates of absence. None of the individuals in

the sample were wearing removal partial dentures at the time for not considering

that the absence of teeth could impair the function of the stomatognathic system.

For the control group, 100 dentate young individuals were evaluated, 14 being

randomly selected to compose the dentate control group.

Bite force and Electromyography

The electromyographic signals and bite force measures were collected

simultaneously, with the volunteers sitting on a comfortable chair (office-like),

with the arms extended along the body and the hands lying on their thighs.

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Bite force records were taken with a digital dynamometer, model IDDK

(Kratos, Cotia, So Paulo, Brazil), with a 1000N capacity, adapted to the mouth

(Figure 1). The apparatus has a set-zero key, which allows the exact control of

the values obtained and also peak registers, that facilitates the record of the

maximal force during measures. It has two arms with plastic disks on each end,

over which the force to be measured is applied. Its high-precision charge cell and

electronic circuit to indicate force, supply precise measures easily viewed on a

digital display. The dynamometer was cleaned with alcohol and disposable latex

finger cots (Wariper-SP) were positioned on the biting arms as a biosecuritymeasure. The participants were given detailed instructions and bite tests were

performed before the actual recordings were made, in order to ensure the

reliability of the procedure. The volunteers were then asked to bite the

dynamometer three times with maximal force, with a two-minute rest interval

between records. Evaluations were performed in the first molar (left and right)

and central incisive regions. For partially edentulous individuals, the shape of the

bite force apparatus enabled the adaptation to the missing teeth region. Maximal

bite force was measured in N through the peak force record indicated on the

screen for subsequent analysis. The highest value out of three records was

considered as the individuals maximal bite force.

Method error

The method error of bite force measurements was performed in five

subjects. Recordings were obtained in two different sessions with a 7-day

interval. In each session, an average of three bites was considered for each

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side, and used later to assess the results. Paired measurements were analyzed

to identify systematic errors. No differences were found between first and

second (one week later) series (2).

Electromyography data

Electromyography was performed using five channels of the Myosystem-

Br1 apparatus (DataHomins Ltda.). The electromyographic signals were

analogically amplified with a gain of 1000x, filtered by a pass-band of 0.01-

1.5KHz and sampled by a 12 bit A/D converter with a 2KHz sampling rate. The

signals were digitally filtered by a pass-band filter of 10 to 500 Hz in the data

processing. Surface differential active electrodes (two 10mm-long and 2mm-wide

Silver-chloride bars, separated by a distance of 10mm, with input impedance of

10G and common-mode rejection ratio of 130dB at 60 Hz) were used in the

study. The skin region where electrodes were placed was cleaned with alcohol

and shaved when necessary.The differential active electrodes were positioned in the ventral region of

both masseter and in the anterior portion of the left and right temporal muscles.

The position of the electrodes was determined by palpation and they were fixated

with adhesive bandage tape, with the longest extension of the bars perpendicular

to the direction of the muscle fibers. A stainless still circular electrode (three

centimeters of diameter) was also used as a reference electrode (ground

electrode), fixated on the skin over the frontal bone region.

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Data Analysis

Statistical analyses were accomplished with the SPSS software, version

12.0 (Chicago, IL) and the data on bite force between dentate and edentulous

individuals were analyzed using independent t-test. A 5% level of significance

(p0.05) was adopted. The analysis of correlation between bite force and

electromyographic activity was performed with the Pearson bivariate correlation

test.

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RESULTS

Bite Force

In the analysis of maximal bite force between groups, dentate individuals

presented greater bite force (p< 0.05) in the molar region. In respect to the

incisive region, although dentate individuals presented greater force, the

difference was small and non-significant (Table 1).

Correlation between maximal bite force and electromyographic activity

The correlation analysis between bite force and electromyographic activity

was performed independently in the two groups for the left and right molar and

incisive regions. In the dentate group, a positive correlation was found for the

Right Molar region, showing that the greater the bite force, the greater the

electromyographic activity for the four muscles analyzed. In the partially

edentulous individuals, negative correlations were found for the left and right

masseter and right temporal muscles. The analysis shows that, in the dentate

group, the correlation values for masseter muscles are higher than those for

temporal muscles, while the opposite relation is observed in partially edentulous

individuals (Table 2).

In the dentate group, the correlation for the Left Molar region was only

positive with the left masseter muscle and, for partially edentulous individuals,

the correlation was positive for the right masseter and left and right temporal

muscles. The correlation values were higher for the temporal muscle compared

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to the masseter in dentate individuals, while the inverse pattern was observed in

partially edentulous individuals (Table 3).

The analysis shows positive correlations between the four muscles

analyzed and the Incisive region in the dentate group, showing that the greater

the bite force, the higher the electromyographic activity. On the other hand,

negative correlations were found for the four muscles in the partially edentulous

group, that is, the greater the bite force, the lower the electromyographic activity

in these individuals. Correlation values for the masseter muscles are higher than

those for the temporal muscles in the dentate group, the opposite being observedin the partially edentulous individuals (Table 4).

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DISCUSSION

The number of teeth in the oral cavity and the absence of dental contacts

are important factors that influence the functioning of the masticatory system (21,

22), since most activities of this system rely on the stability of dental contacts

between the maxilla and the jaw (3).

The main objective of this research was to compare partially posterior

edentulous individuals, with age ranging from 20 to 40 years, and dentate

individuals, observing possible alterations caused by dental loss in terms of bite

force and the correlation between bite force and electromyographic activity,evidencing the need for posterior buccal rehabilitation, not only due to the

aesthetic value of the smile, but mostly in order to maintain the functional

balance of the masticatory system.

In the present study, the partially edentulous individuals were selected

according to the criteria of presenting loss of at least 10 superior or inferior molar

or premolar teeth, regardless of their location in the dental arch. The difficulty to

standardize the dental loss in partially edentulous individuals caused the

posterior dental absence to be diverse within the group, which may have

influenced the results obtained in this work.

In the maximal bite force evaluation, the individuals of both groups were

properly instructed and collaborated with the experiment. The standardization of

the methodology and the performance of three repetitions with two-minute

intervals between each for the obtention of maximal bite force were

accomplished so that errors and interferences were minimized.

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A digital dynamometer with a capacity of up to 1000N, adapted to the

mouth conditions, was used in this study. The device has two arms with plastic

disks on each end, over which the force to be measured was applied. Its high

precision charge cell and electronic circuit to indicate force, supply precise and

easily readable measures on the digital display. The diameter of the arms,

together, is of approximately 10mm, adequate for an oral aperture that does not

interfere in the force employed, preventing muscular strain (or even suboptimal

sarcomere length) and exaggerated displacement of the condyles (2, 1).

Gibbs et al. (6), analyzing the effects of dental loss on masticatory force,observed that the greater the posterior dental absence, the lower the bite force

and masticatory efficiency of individuals, a result that is similar to those observed

in this work, where the analysis of maximal bite force between groups showed

significantly greater bite force in the molar region in dentate individuals (p< 0.05).

In the analysis of bite force in the incisive region, as dentate and partially

edentulous individuals had all the anterior teeth, no significant differences were

observed, and the values obtained for the incisive region in the dentate and

partially edentulous individuals were, respectively: 110 N (10) e 90 N (10),

which prove acceptable and show that the morphological alterations in the dental

arches lead to functional alterations, which may result in changes in the

masticatory pattern and muscular physiology.

The values obtained in this study for the left and right molar regions in the

dentate and partially edentulous groups were, respectively: 470 N (45), 110 N

(27), 480 N (45), and 80 N (23), which highlights the huge difference between

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the values obtained when individuals have a complete dentition evidenced in the

present study by the statistically significant difference in bite force between the

dentate and partially edentulous groups in the molar.

The correlation between electromyographic activity and bite force was

analyzed with the Pearson correlation test for the masseter and temporal

muscles in the two groups, in the left and right molar and incisive regions. The

values obtained were not statistically significant.

In the present study, the correlations between electromyographic activity

and bite force in the dentate group presented positive coefficients for all themuscles in the right molar region, for the left temporal muscle in the left molar

region and for all the muscles in the incisive region.

In the right molar region of the partially edentulous group, the left temporal

muscle was the only to present a positive correlation. In the left molar region, the

correlation was positive for the right masseter and right and left temporal

muscles. In the incisive region all muscles presenting negative correlations.

Positive correlations were found for most regions analyzed in the dentate

group, which shows that the greater the bite force, the higher the

electromyographic activity for the four muscles studied and, in the partially

edentulous group, correlations were negative in most of the regions analyzed.

These results suggest the existence of an asymmetry in the contribution of the

muscular activity to the bite force in dentate and partially edentulous individuals.

To Raadsheer et al. (15), the absence of positive correlations suggests

that the analysis of a single comparison (force) may be little appropriate as a

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parameter, other factors such as mastication and muscular thickness should be

analyzed. The correlation between the magnitude of bite force and the number of

teeth in contact has been determined in previous studies. The muscular force

that results in greater bite force enhances the masticatory function and the

occlusal stability, thus enabling a greater number of teeth to be in contact.

Besides, the distribution of the muscular force over a broader occlusal area also

distributes the pain and increases the positive feedback of periodontal receptors

(8, 19).

The dental absence interferes in the physiological functioning of themasticatory system, which leads to occlusal and functional changes. In face of

such disharmony, a defense mechanism is activated in an attempt to determine a

pattern of action which is less traumatic to the other components of the system.

However, each individual presents, physiologically, a tolerance for dysfunctions,

and depending on the intensity and frequency with which they are repeated,

many can not stand the action of time and may develop severe dysfunctional

problems. Tallents et al. (20), while studying the relation between the loss of

posterior teeth and intra-articular disorders using magnetic resonance, observed

that the results indicated a significant increase in the prevalence of symptoms in

patients with posterior dental loss, and that the absence of these can accelerate

the onset of degenerative articular diseases.

The maintenance of a reasonable amount of natural and healthy teeth is

the best way to ensure good masticatory efficiency as the patients age

increases.

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This leads us to reflect on the need for future studies to investigate the

masticatory activity in partially edentulous individuals, taking into account the

alterations found, which prove the presence of functional alterations in the

masticatory system in partially edentulous individuals.

We conclude from the above that dental loss leads to alterations in the

stomatognathic system; maximal bite force is greater in dentate individuals and,

in respect to the correlations between bite force and electromyography, it has

been shown that, for dentate individuals, the greater the bite force, the higher the

electromyographic activity, which was not true for partially edentulous individuals.

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Tables

Table 1: Maximal Bite Force (N) and standard-error in the molar and incisive

teeth regions in each experimental group.

Region GroupSample

(n)

Force

(N)

Standard

errorSig.

Right MolarPartially edentulous 14 110 27

0.0005**Dentate 14 470 45

Left MolarPartially edentulous 14 80 23

0.0005**Dentate 14 480 45

IncisivesPartially edentulous 14 90 11

0.224Dentate 14 110 11

* *indicates statistical significance for p< 0,05

Table 2: Correlation coefficients (r) between electromyographic activity and

maximal bite force in the Right Molar region for the dentate and partially

edentulous groups.

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Muscle r - dentate Sig.

dentate

r partially

edentulous

Sig. Partially

edentulous

Right Masseter 0.314 0.274 -0.078 0.791Left Masseter 0.509 0.063 -0.038 0.896Right Temporal 0.289 0.317 -0.203 0.487Left Temporal 0.019 0.950 0.173 0.553


maximal bite force in the Left Molar region for the dentate and partially

edentulous groups.


dentate

r partially

edentulous

Sig. Partially

edentulousRight Masseter -0.073 0.803 0.039 0.894Left Masseter 0.073 0.804 -0.202 0.489

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Right Temporal -0.186 0.524 0.114 0.699Left Temporal -0.081 0.782 0.039 0.894


maximal bite force in the Incisive region for the dentate and partially edentulous

groups.


dentate

r partially

edentulous

Sig. Partially

edentulousRight Masseter 0.300 0.297 -0.045 0.879

Left Masseter 0.393 0.164 -0.134 0.649Right Temporal 0.458 0.099 -0.126 0.667Left temporal 0.103 0.727 -0.221 0.448

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correlation between bite force and electromyographic activity in dentate and partially edentulous...

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