Keywords
asthma - mastication - electromyography - child - stomatognathic system
Introduction
Data from the International Study of Asthma and Allergies in Childhood (ISAAC) show
that asthma should be considered an important public health problem[1]. Studies show that 24% of school-age children have asthma[2]. The prevalence of asthma has grown considerably worldwide in recent decades, although
some studies have shown stabilization of this trend[3].
Morphological and physiological analysis has shown the similarities and structural
differences between the nasal mucosae and the mechanisms related to asthma, including
the influence of mouth breathing secondary to nasal obstruction. Anatomo-functional
changes not associated with asthma may influence the mastication process[4].
Mastication is the combination of stomatognathic functional events that mechanically
break down food into tiny pieces, aiding the digestion and absorption of nutrients
necessary for the body's metabolic activity[5]. Mastication is a complex process that depends on muscles, ligaments, bones, and
teeth, all controlled by the central nervous system. The muscles involved in mastication
mediate movements and postures that bring the teeth together and move them apart or
intensify the interocclusal pressure[6].
The activity of masticatory muscles can be evaluated by instruments and systems that
measure and analyze the electrical activity of muscle[7]. The literature on electromyographic analysis of masticatory muscles contains studies
of pre-adolescents[8] and young or elderly adults[8]
[ 9]
[ 10], but few reports involving children[11].
The high number of asthmatic children is an alarming public health issue[3]. Therefore, there is interest in studies that relate asthma to functional alterations
of the stomatognathic system. The objective of this study was to determine the characteristics
of mastication in asthmatic children treated at a pediatric and allergology ambulatory
clinic of the Hospital das Clínicas of Pernambuco and to measure the side prevalence
of mastication, number of cycles, total duration of mastication, and electrical activities
of the right and left masseter and temporal muscles of asthmatic and non-asthmatic
children.
Method
This was a descriptive and cross-sectional study that was conducted from April–December
2008 at the pediatric and allergology ambulatory clinic of the Hospital das Clínicas,
which is affiliated with the Universidade Federal of Pernambuco (UFPE).
The population consisted of 2 groups: a group of asthmatic children consisting of
30 children with diagnoses of moderate or serious asthma and a non-asthmatic group
consisting of 30 children without asthma. All children were between 6 and 10 years
of age. Children with neurological impairments, serious cardiopathies, orthodontic
devices, craniofacial abnormalities, or hypertrophy of the tonsils and/or adenoids,
as well as those who were suffering asthma attacks at the time of evaluation, were
excluded from this study.
This study was approved by the Committee of Research Ethics of Universidade Federal
of Pernambuco, approval # 224/2006, and was supported financially by the CNPq-Edictal
Universal Process 476370/2007-8. The adult responsible for each child was initially
apprised of the objectives of the study, later informed that the study had been approved
by the committee of ethics in research of the Universidade Federal of Pernambuco,
and afterwards was requested to sign a declaration of free consent to the child's
participation in the study under the clarified terms. The data were collected by evaluation
of the subjects in a room in the Department of Allergology of the Hospital das Clínicas
in the presence of an adult responsible for the child and at least 1 of the researchers.
We adapted a previously published protocol for evaluation of mastication[12]
[ 13]. The child was requested to sit comfortably in a chair and eat a 25-g French roll
in a normal manner. The child was recorded during mastication with a Sony Handycam DCR-TRV130 Digital-8 TRV130 NTSC set on a tripod at a distance of 5 feet from the subject, and the data
were recorded on a 8-mm tape. The duration of mastication was also recorded with a
Casio® stopwatch.
The electrical activities of the masseter and temporalis muscles were measured in
microvolts (µV) by the MIOTOOL 200/400 instrument from Miotec® connected to an LG notebook with a 110GB HD and an Intel® Pentium® Dual-Core T2330 1.10 GHz processor and running the Windows® Vista Premium operating system. Additional equipment used (all from the Miotec® company) included a Communication Cable USB connection between the computer and electromyography
instrument, Miograph 2.0 Software (a data acquisition system that provided the opportunity
to choose from 8 independent gains per channel, which was used to a gain of 1000),
a 7.2-V NiMH 1700-mA rechargeable battery with a life of approximately 40 h that allowed
operation in isolation from the utility system, 4 SDS500 sensors connected to clamp
sensors, Cable Reference (earth), and MEDITRACE® draft and disposable electrodes consisting of Ag/AgCl immersed in a conductive gel
and responsible for collecting and carrying the electromyography signals. This type
of electrode has been described previously[14].
Before the electrodes were placed, each child's skin was cleaned with a 70% alcohol
swab to remove any excess skin oil that could increase the impedance of the uptake
signal[15]
[ 16]. The electrodes were placed bilaterally and oriented longitudinally with the muscle
fibers[17]. To avoid interference in the signal acquisition, the reference electrode was placed
at the ulnar styloid process of the right arm.
The electrical activities of the right and left masseter muscles were recorded in
the following situations: mandible in the resting position (5 seconds), occlusion
with maximum voluntary contraction (5 seconds), and mastication of 1 25-g French roll
(entire time required to masticate all of the bread was recorded). The subjects were
prevented from seeing the computer screen in order to avoid any visual feedback that
could affect the evaluation. After data acquisition, the electromyographic traces
were evaluated with specific attention to recording the mastication, determining the
duration of the second mastication process, and counting the cycles from the subject's
second incision of French bread until the end of the last deglutition. The Kolmogorov–Smirnov
test was used to determine whether the data for each variable recorded in the study
were normally distributed. Student's t-test was used for comparison of the variables
between groups. The level of significance was 5% for all tests. The Excel 2000 and
SPSS v. 8.0 software programs were used for the analysis.
Results
[Table 1] presents the data for mastication speed, alternate bilateral mastication, simultaneous
bilateral mastication, unilateral mastication, alternate bilateral mastication on
the right side, and alternate bilateral mastication on the left side of the asthmatic
and non-asthmatic children. No significant difference was found between the asthmatic
and non-asthmatic groups.
Table 1.
Mastication parameters (mastication speed, alternate bilateral mastication, simultaneous
bilateral mastication, unilateral mastication, alternate bilateral mastication on
the right side, and alternate bilateral mastication on the left) of asthmatic and
non-asthmatic children.
|
Mastication Characteristics
|
Non-asthmatic
|
Asthmatic
|
p-value
|
|
N
|
%
|
N
|
%
|
|
|
Alternate bilateral mastication
|
|
Yes
|
20
|
66.7
|
16
|
53.3
|
|
|
No
|
10
|
33.3
|
14
|
46.7
|
0.430
|
|
Simultaneous bilateral mastication
|
|
Yes
|
4
|
13.3
|
3
|
10.0
|
|
|
No
|
26
|
86.7
|
27
|
90.0
|
1.000
|
|
Unilateral mastication
|
|
Yes
|
6
|
20.0
|
11
|
36.7
|
|
|
No
|
24
|
80.0
|
19
|
63.3
|
0.252
|
|
Alternate bilateral mastication on the right side
|
|
|
|
|
|
|
Yes
|
10
|
33.3
|
8
|
26.7
|
|
|
No
|
20
|
66.7
|
22
|
73.3
|
0.779
|
|
Alternate bilateral mastication on the left
|
|
Yes
|
10
|
33.3
|
7
|
23.3
|
|
|
No
|
20
|
66.7
|
23
|
76.7
|
0.567
|
[Table 2] presents the data for the total number of cycles and total duration of mastication
of a French bread (25 g) in the asthmatic and non-asthmatic children.
Table 2.
Total number of masticatory cycles and total duration of mastication in asthmatic
and non-asthmatic children.
|
N
|
Minimum
|
Maximum
|
Average
|
Standard Deviation
|
p-value
|
|
Total number of masticatory cycles
|
|
Non-asthmatic
|
30
|
10.00
|
81.00
|
30.00
|
15.84
|
|
|
Asthmatic
|
30
|
10.00
|
70.00
|
26.90
|
13.33
|
0.415
|
|
Total duration of mastication of a French bread (25 g)
|
|
Non-asthmatic
|
30
|
69.30
|
955.00
|
262.25
|
179.38
|
|
|
Asthmatic
|
30
|
90.04
|
600.00
|
256.78
|
129.92
|
0.893
|
[Table 3] shows the Pearson's correlation coefficients for the associations between the duration
of mastication of each piece of bread and the number of masticatory cycles on the
right side, number of masticatory cycles on the left side, number of masticatory cycles
on both the right and left sides, and total number of masticatory cycles. Significant
associations were observed with all variables except the number of masticatory cycles
on the right side.This means that the relationship is direct and that the time required
to masticate the piece of bread increases with the number of cycles.
Table 3.
Pearson's correlation coefficients for the associations between the duration of mastication
of each piece of bread and the number of masticatory cycles on the right side, number
of masticatory cycles on the left side, number of masticatory cycles on both the right
and left sides, and total number of total masticatory cycles.
|
Duration of mastication of each piece of bread
|
|
Non-asthmatic
|
Asthmatic
|
|
Number of masticatory cycles on the right side
|
0.63[1]
|
0.27
|
|
Number of masticatory cycles on the left side
|
0.45[1]
|
0.42[1]
|
|
Number of masticatory cycles on both right and left sides
|
0.41[1]
|
0.41[1]
|
|
Total number of masticatory cycles
|
0.93[1]
|
0.87[1]
|
1 p < 0.05
[Table 4] shows the data for the electrical activity of the masseter during rest, maximum
contraction, and mastication in non-asthmatic and asthmatic children. The electrical
activity of this muscle did not differ significantly between the non-asthmatic and
asthmatic groups. However, the average activity recorded on the right side was observed
to be higher in the asthmatic group at rest but not when bilateral contraction of
the masseter muscles was required during maximum voluntary contraction or mastication.
On the left side of face, the average electrical activity of the asthmatic group was
similar to that of the non-asthmatic group at rest but lower during maximum voluntary
contraction and mastication. These results demonstrate that the masseter muscles of
the asthmatic group did not exhibit average electrical activity equivalent to that
of the non-asthmatic group during functions requiring an increase in muscle strength.
Table 4.
Electrical activities of the masseter during rest, maximum contraction, and mastication
in non-asthmatic and asthmatic children.
|
N
|
Minimum
|
Maximum
|
Average
|
Standard Deviation
|
p-value
|
|
Right masseter at rest
|
|
Non-asthmatic
|
30
|
3.90
|
13.00
|
6.33
|
2.14
|
|
|
Asthmatic
|
30
|
2.80
|
18.00
|
6.61
|
3.60
|
0.709
|
|
Left masseter at rest
|
|
Non-asthmatic
|
30
|
4.20
|
13.80
|
6.86
|
2.85
|
|
|
Asthmatic
|
30
|
3.30
|
18.70
|
6.78
|
3.46
|
0.922
|
|
Right masseter during maximum voluntary contraction
|
|
Non-asthmatic
|
30
|
19.10
|
198.50
|
82.70
|
39.52
|
|
|
Asthmatic
|
30
|
8.90
|
192.50
|
81.00
|
45.60
|
0.878
|
|
Left masseter during maximum voluntary contraction
|
|
Non-asthmatic
|
30
|
23.40
|
242.50
|
78.73
|
43.49
|
|
|
Asthmatic
|
30
|
10.10
|
171.30
|
74.05
|
35.86
|
0.651
|
|
Right masseter during mastication
|
|
Non-asthmatic
|
30
|
17.40
|
110.50
|
48.78
|
23.01
|
|
|
Asthmatic
|
30
|
14.00
|
97.20
|
43.89
|
20.17
|
0.385
|
|
Left masseter during mastication
|
|
Non-asthmatic
|
30
|
19.90
|
124.60
|
48.36
|
24.18
|
|
|
Asthmatic
|
30
|
10.30
|
109.40
|
43.63
|
21.40
|
0.426
|
[Table 5] presents the measurements of the electrical activity of each anterior temporal muscle
during rest, maximal voluntary contraction, and mastication in non-asthmatic and asthmatic
children. Differences were suggestive in the electrical activities recorded but not
significant between the asthmatic and control groups. However, the activity measurements
for the right anterior temporal muscle at rest were higher in the asthmatic group.
Therefore, children in the asthmatic group exhibit greater electrical activity in
both the right masseter and temporal muscles at rest.
Table 5.
Electrical activities of the anterior temporal muscles during rest, maximal voluntary
contraction, and mastication in non-asthmatic and asthmatic children.
|
N
|
Minimum
|
Maximum
|
Average
|
Standard Deviation
|
p-value
|
|
Right anterior temporal at rest
|
|
Non-asthmatic
|
30
|
5.30
|
20.80
|
11.56
|
4.58
|
|
|
Asthmatic
|
30
|
5.70
|
117.70
|
15.80
|
19.96
|
0.261
|
|
Left anterior temporal at rest
|
|
Non-asthmatic
|
30
|
5.50
|
32.50
|
13.93
|
6.56
|
|
|
Asthmatic
|
30
|
5.40
|
31.30
|
12.79
|
5.74
|
0.474
|
|
Right anterior temporal during maximal voluntary contraction
|
|
Non-asthmatic
|
30
|
14.70
|
244.70
|
110.62
|
54.26
|
|
|
Asthmatic
|
30
|
19.10
|
242.20
|
99.84
|
50.76
|
0.430
|
|
Left anterior temporal during maximal voluntary contraction
|
|
Non-asthmatic
|
30
|
22.50
|
261.50
|
110.24
|
62.41
|
|
|
Asthmatic
|
30
|
22.00
|
233.90
|
101.41
|
47.78
|
0.541
|
|
Right anterior temporal during mastication
|
|
Non-asthmatic
|
30
|
5.50
|
130.80
|
55.07
|
25.41
|
|
|
Asthmatic
|
30
|
14.20
|
143.20
|
53.93
|
29.41
|
0.873
|
|
Left anterior temporal during mastication
|
|
Non-asthmatic
|
30
|
28.90
|
146.00
|
60.85
|
28.07
|
|
|
Asthmatic
|
30
|
17.70
|
110.50
|
59.62
|
22.98
|
0.853
|
Discussion
Alternate bilateral mastication was observed in 66.7% of the non-asthmatic children
and 53.3% of the asthmatic children; a previous study that aimed to describe mastication
in children with mixed dentition found that this pattern occurred in 69% of the individuals
analyzed[18]. The literature indicates that alternate bilateral mastication evenly distributes
the force of mastication, subjecting the muscles and joints to alternating periods
of work and rest and leading to synchrony and muscle and functional balance[19]
[ 20]
[ 21].
A study of 26 5-to-7-year old children at a private school in Recife indicated that
the masticatory pattern can be related to the craniofacial growth pattern and that
growth can be directly related to a child's habits at this age. In that study, 38.5%
of the children exhibited alternate bilateral mastication, which is the ideal pattern.
Such balanced distribution of masticatory force supports the harmonious growth of
the face[21].
In the present study, 13.3% of the non-asthmatic children and 10.0% of the asthmatic
children exhibited a simultaneous bilateral masticatory pattern, also known as vertical
structure. A study conducted in 2003 on 61 children with mixed dentition found that
23% exhibited predominantly vertical movements during mastication of French bread[18].
Unilateral mastication was observed in 20% of the non-asthmatic children and 36.7%
of the asthmatic children. Unilateral mastication is known to stimulate inappropriate
growth or prevent stabilization of stomatognathic structures[19]. An examination of unilateral mastication in 4-to-5-year old children with normal
occlusion found that mastication was predominantly unilateral in 65% of the children
studied[22].
The alternate bilateral pattern with right-sided predominance was observed in 33.3%
of non-asthmatic children and 26.7% of asthmatic children. Similar findings were reported
in a study of 20 children selected from 2 private schools, of which 35% exhibited
predominantly left-sided and 30% exhibited predominantly right-sided mastication[22].
The average total number of masticatory cycles was 30 in the non-asthmatic children
and 26.9 in the asthmatic children; these data are consistent with the findings of
a study of the total number of masticatory cycles in which the range was 9 to 60 cycles[23].
There are few studies comparing the duration of mastication between adults and children.
In this study, the duration of mastication was shorter in asthmatic than in non-asthmatic
children. A study comparing the durations of mastication of different types of food
in children[24] found that food consistency affects the duration of mastication. However, that study
did not relate these durations to possible changes in the stomatognathic system.
The hypothesis that asthma interferes with masticatory function cannot be confirmed
because the results of this study show that asthmatic children may tend to masticate
for a shorter length of time. The difficulties in and incoordination of breathing
experienced by asthmatic children may be directly related to their reduced masticatory
times, as such children may have difficulty maintaining the necessary balance required
for breathing during feeding.
The electromyographic activity of the masticatory muscles at rest is known to be higher
in patients with disorders of the stomatognathic system than in healthy individuals,
indicating that such disorders increase basal masticatory muscle tone[25]
[ 26]. Any condition that causes an imbalance in the orofacial muscles can lead to such
changes in tone[27]. This information is consistent with the results of the present study. The equal
or greater electrical activities at rest of the masseter and temporal muscles of asthmatic
children relative to those of non-asthmatic children may therefore be due to the incorrect
performance of mastication by asthmatic children.
These values were reversed during maximum voluntary contraction and mastication because
the muscles require a degree of coordination to perform the orofacial actions of the
stomatognathic system in a functional manner. These results also concur with those
for masticatory time, implying that asthmatic children compensate with their smaller
muscles.
Mastication requires coordinated action of the orofacial muscles, which in turn need
optimal electrical activity in order to perform their functions. In this study, the
duration of mastication was longer in non-asthmatic children than in asthmatic children.
The average electrical activity at rest of the anterior temporal and masseter muscles
was higher in the asthmatic group, but this trend was reversed during maximum voluntary
contraction and mastication. These results imply that the electrical activity is directly
linked to the function of each muscle group, with non-asthmatic children processing
their food for longer and thus requiring more electrical activity of the muscles during
mastication.
Conclusions
While the masticatory process did not differ significantly between asthmatic and non-asthmatic
children, this study found indications that the masticatory process of asthmatic children
may be somewhat altered by asthma-related anatomo-functional changes.
