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POSTUROLOGY                                                                                                                                                       www.stomaeduj.com




EFFECTS OF MASTICATORY MOVEMENTS ON THE HEAD,
TRUNK AND BODY SWAY DURING THE STANDING
POSITION




                                                                                                                                                                Original Articles
Kiwamu Sakaguchi1a , Keiko Shima1b* , Noshir R. Mehta2c , Tomoaki Maruyama3d , Leopoldo P. Correa2e, Atsuro Yokoyama1f
1
  Division of Oral Functional Science, Graduate, Department of Oral Functional Prosthodontics, School of Dental Medicine, Hokkaido University, Sapporo, Japan
2
 Craniofacial Pain Center, Department of Diagnostic Sciences, Tufts University School of Dental Medicine, Boston, MA, USA
3
 Computer Science Course, Department of Industrial Engineering, National Institute of Technology (KOSEN), Ibaraki College, Hitachinaka, Japan
aDDS, PhD, Associate Professor; e-mail: sakaguti@den.hokudai.ac.jp; ORCIDiD: https://orcid.org/0000-0002-5955-3043
bDDS, PhD; e-mail: shimak@den.hokudai.ac.jp
cDMD, MDS, MS, Professor Emeritus; e-mail: noshir.mehta@tufts.edu; ORCIDiD: https://orcid.org/0000-0003-0360-9535
dPhD, Associate Professor; e-mail: maruyama@ee.ibaraki-ct.ac.jp; ORCIDiD: https://orcid.org/0000-0002-0553-4787
eBDS, MS, Associate Professor; e-mail: leopoldo.correa@tufts.edu
fDDS, PhD, Professor; e-mail: yokoyama@den.hokudai.ac.jp; ORCIDiD: https://orcid.org/0000-0003-4763-418

ABSTRACT                                                                           https://doi.org/10.25241/stomaeduj.2022.9(3-4).art.1

Introduction Mastication involves complex tongue movements, coordination of lip, and cheek movements
and is associated with head movement to facilitate the intraoral transport of food from ingesting to
swallowing; it affects many functions of the whole body. However, studies to evaluate the relationship
between masticatory movements and the body posture are still lacking to our knowledge. The purpose of
this study was to characterize the effects of masticatory movements on the head, trunk, and body sway
during the standing position.
Methodology A total of 30 healthy subjects were evaluated. The MatScanTM system was used to analyze
changes in body posture (center of foot pressure: COP) and the 3-dimensional motion analysis system was
used to analyze changes in the head and trunk postures while subjects remained in the standing position
with the rest position, centric occlusion, and masticating chewing gum.
Results The total trajectory length of COP and head and trunk sways during masticating chewing gum were
significantly shorter and smaller respectively than it was in the rest position and centric occlusion (p<0.016).
COP area during masticating chewing gum was significantly smaller than it was in the 2 mandibular positions
(p<0.016).
Conclusion Masticatory movements positively affect the stability of the head, trunk, and body sways and
enhance the postural stability during the standing position.
KEYWORDS
Masticatory Movements; Head, Trunk, and Body Sways; Changing Body Posture; Standing Position;
Postural Stability

1. INTRODUCTION                                                                 in rhythmical coordination with the mandibular
One of the purposes in dental prosthetic treatment                              movement during mastication [9]. The height of the
includes the recovery of the masticatory function.                              body’s center of mass is somewhere between 55%
Mastication involves not only simple sequential                                 (women) and 57% (men) of the standing height [10],
jaw-opening and jaw-closing movements but also                                  and the small area of the sole of the foot supports
complex tongue movements, coordination of lip,                                  the weight of the whole body. Therefore, stability in
and cheek movements and is associated with head                                 head posture is indispensable to the control of the
movement to facilitate the intraoral transport of                               body posture during the standing position.
food from ingesting to swallowing [1-3].                                        Previous studies have analyzed the relationships
It has been reported that masticatory movements                                 between the mandibular position and body posture
affect many functions of the whole body, including                              [11,12]. Further studies have discussed relationships
the awakening effect [4,5], promotion of cerebral                               between mastication and the static [13,14] and
function [6], reaction latency to external disturbances                         dynamic [7] balance of body posture, leg muscle
[7], and are closely related to health promotion [8].                           activity [15], neck muscle activity [16], head position
There is a report in the literature that the head moves                         [17], and upper half of body [18].
              OPEN ACCESS This is an Open Access article under the CC BY-NC 4.0 license.
              Peer-Reviewed Article
    Citation: Sakaguchi K, Shima K, Mehta NR, Maruyama T, Correa LP, Yokoyama A. Effects of masticatory movements on the head, trunk and body sway
    during the standing position. Stoma Edu J. 2022;9(3-4):81-87.
    Received: October 06, 2022; Revised: October 29, 2022; Accepted: November 05, 2022; Published: November 15, 2022.
    *Corresponding author: Kiwamu Sakaguchi, Division of Oral Functional Science, Department of Oral Functional Prosthodontics, Graduate School of
    Dental Medicine, Hokkaido University, Sapporo, Japan.
    Tel.: +81-11-706-4270; Fax: +81-11-706-4903; e-mail: sakaguti@den.hokudai.ac.jp
    Copyright: © 2022 the Editorial Council for the Stomatology Edu Journal.




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                    Sakaguchi K, et al.
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                    However, studies to evaluate the relationship                                 2.2 Analysis of simultaneous measurements of head,
Original Articles   between masticatory movements and the body                                    trunk, and body sways (Fig. 2)
                    posture are still lacking to our knowledge. The                               The MatScanTM system (Tekscan Inc., Boston, MA,
                    purpose of this study was to characterize the effect                          Nitta Corp., Osaka, Japan) was used to analyze
                    of masticatory movements on head, trunk, and body                             body sway [11,12,20]. This instrument provided a
                    sways during the standing position.                                           dynamic evaluation of body posture. This system
                                                                                                  could measure weight distribution and changes
                    2. METHODOLOGY                                                                in the position of the center of foot pressure (COP)
                                                                                                  on a footplate during a standard measuring period.
                    2.1 Study population and ethics                                               The COP is the center of vertical force acting on the
                    30 healthy students (15 males and 15 females) with                            support surface. It indicates gravity shifts in the
                    an average age of 28.6 years (range 22-32 years) were                         anteroposterior and lateral directions.
                    recruited among the students and staff members of
                    the Graduate School of Dental Medicine Hokkaido
                    University. The sample size was calculated using the
                    software program G*Power 3.1.9.2 (Heinrich-Heine-
                    Universität Düsseldorf ). When the sample size was
                    calculated by setting α = 0.05, β = 0.8, and effect
                    size = 0.8, 26 participants were needed. All subjects
                    met the following inclusionary criteria: (1) no history
                    of head and neck or back problems, (2) no history
                    of signs and symptoms of temporomandibular
                    disorders or orofacial pain, (3) no history of
                    orthopedic or otolaryngologic problems affecting                                Figure 2. Analysis of simultaneous measurements of the head, trunk
                    body balance, (4) absence of prosthesis (i.e., crowns,                        and body sways. Data sampling was performed simultaneously at a
                                                                                                  sampling rate of 60 Hz using a self-made external synchronization device.
                    bridges, implants or removable prosthetics) and
                                                                                                  For the head and trunk sway measurements, a three-dimensional motion
                    class I dental occlusion, and (5) the pattern during                          analysis system (Library Co., Ltd., Tokyo, Japan) was used to analyze the
                    mastication assessed by a linear or concave opening                           motion of the target points set on the head and trunk respectively. In the
                    path from centric occlusion toward the working side                           head sway analysis, the coordinates were transformed to a coordinate
                    and a subsequent convex closing path in the vicinity                          system, a trunk coordinate system, based on the trunk to eliminate the
                    of centric occlusion [19].                                                    trunk sway. The center of foot pressure (COP) and weight distribution were
                                                                                                  measured using a footplate, the MatScanTM system (Tekscan Inc., Boston,
                    The movement of the mandibular incisal point                                  MA, Nitta Corp., Osaka, Japan). CCD: Charge coupled device.
                    during chewing gum on habitual chewing side was
                    recorded by the optical jaw motion tracking device                            The three-dimensional motion analysis system
                    (FUJITA Medical Instruments Co, Japan) and was                                (Library Co., Ltd, Tokyo, Japan) was used to analyze
                    analyzed using the overlapping of each cycle and                              head and trunk sways. This instrument enabled the
                    average path [19] (Fig. 1).                                                   measurement of the three-dimensional movements
                                                                                                  of target points on the surface of the facial skin and
                                                                                                  body surface simultaneously. The movements of the
                                                                                                  target points were recorded by three charge coupled
                                                                                                  device (CCD) cameras, and the three-dimensional
                                                                                                  coordinates were calculated by using an analyzing
                                                                                                  software (Library Co., Ltd, Tokyo, Japan). The target
                                                                                                  points on the face and trunk skin were marked by
                                                                                                  attaching 4 points respectively (Fig. 3).




                      Figure 1. An example of overlapping of cycle and average path during
                    chewing on the right side. Using the centric occlusion of each cycle as the
                    standard, coordinates for each cycle were determined by vertically dividing
                    the opening and closing paths into 10 equally spaced sections in the
                    frontal view. From these coordinates, the average path and SD (standard
                    deviation) were calculated. The method used to calculate the average path
                    is as follows: (A) 5-14 cycles on the habitual side chewing were recorded,
                    and the coordinates for each cycle were determined by vertical division
                    into 10 equally spaced sections. (B) Overlapping of each cycle and average
                                                                                                    Figure 3. Target points set on the head and trunk. Four target points
                    path. (C) Average path and SDs of each level.
                                                                                                  were set on the head (No. 1-4) and trunk (No. 5-8) respectively for the
                    This study was approved by the ethical committee                              motion analysis. No. 1: nasion, No. 2: top of the nose, No. 3 and 4: right and
                    of the Graduate School of Dental Medicine Hokkaido                            left zygomatic bones, No. 5: jugular notch, No. 6: xiphoid process, No. 7 and
                                                                                                  8: right and left clavicle middle point. Round reflecting markers (10 mm in
                    University (2019-No.2). The study methodology was                             diameter) were used as target points to be recognized by using their
                    explained, and written consent was obtained from                              luminance values, and double-sided tape was used for setting these
                    all participants prior to their inclusion in the study.                       markers on the head and trunk.luminance values.




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Effects of masticatory movements
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The center of the 4 target points was calculated in           values in each trial was calculated (LWD). The same




                                                                                                                                                         Original Articles
each sampling frame. Then the mean coordinate                 calculation was carried out for the anteroposterior
of all the centers of the 4 target points on the face         weight distribution value (AWD). The calculation for
was defined as the virtual central coordinate of the          the LWD and AWD was as follow: LWD (%) = 50 - (the
head (MCB-h). In the same way, the mean coordinate            right-anterior value + the right-posterior value), and
of all the centers of the 4 target points on the trunk        AWD (%) = 50 - (the right-posterior value + the left-
was defined as the virtual central coordinate of the          posterior value).
trunk (MCB-t). The head sway was analyzed based on
the coordinate system located on the trunk (A trunk
coordinate system). The trunk sway was analyzed
based on the coordinate system on the ground.

For all tests, the subjects were asked to remove their
shoes and socks, to stand with their feet apart to the
width of their shoulders in a natural stance on the
force platform of the MatScanTM system. To assist in
obtaining the natural standing posture, the subjects
were asked to look directly into a reflected image of
their eyes, two meters away with arms hanging free
at their sides and to remain in this position during the       Figure 4. A four-quadrant weight distribution. Pressure at the soles of
measurements. Simultaneous measurement of the                 both feet was measured in equalized four-quadrant sections: (1) left
head, trunk, and body sways was conducted under               anterior, (2) right anterior, (3) left posterior, and (4) right posterior. L: left side,
the following three conditions: (1) The subjects              R: right side.
maintained the rest position (teeth slightly apart            The head and trunk sway values were used to
and masticatory muscles in a relaxed non-contractile          evaluate the stability of the head and trunk position
condition). (2) The subjects maintained the centric           respectively. Each trial of the three-dimensional
occlusion without clenching. (3) The subjects chew            motion analysis system was recorded in 1200 frames
softened chewing gum on their habitual chewing                for 20 seconds. The 3-dimensional coordinate of
side and were requested not to swallow it for the             the center of the 4 target points of the head was
time tested. These three conditions were randomly             acquired for every frame. The head sway value was
conducted in each subject, based on the table of              defined as the mean distance between MCB-h and
random numbers. Testing under each condition was              each center of the 4 target points. The trunk sway
recorded for 20 seconds. The recording was started            value was obtained in the same manner as the head
after the subject stood on the MatScanTM sensor               sway value.
and the investigator confirmed that their head and            Each trial was repeated three times and the average
body positions were stable. Each trial was recorded           value of the three trials was used as the representative
three times with a one-minute rest period.                    value for each subject.

2.3 Parameters                                                2.4 Statistical analysis
The total trajectory length of the COP and COP areas          The total trajectory length of the COP, the COP areas
(Rectangular area, Outer peripheral area, Root mean           (Rectangle area, Outer peripheral area, Root mean
square area) were used to evaluate the stability of the       square area), the lateral and anteroposterior weight
body posture [11,12]. Each trial of the MatScanTM             distribution and the head and trunk sway values
system was recorded in 1200 frames for 20 seconds.            were compared to evaluate whether the masticatory
The 2-dimensional coordinates of the COP were                 movements affected the head, trunk, and body
acquired for every frame. First, the effective distance       sways. All comparisons were performed using
of the COP between one frame and the next frame               Friedman’s two-way analysis of variance (p<0.05)
was calculated based on the pitch of the sensor               and the Wilcoxon t-test with Bonferroni correction
sheet in each trial. The total trajectory length of the       (0.05/3 = 0.016) were used. SPSS version 21 (SPSS
COP for each trial was then calculated by summing             Japan Inc., Tokyo, Japan) was used for statistical
up all the effective distances of the COP between             analysis.
1200 consecutive frames. The COP areas were the
rectangular area, the outer peripheral area, and the          3. RESULTS
root mean square area of the total trajectory of 1200
COPs respectively.                                            The results of the comparisons (median values)
The lateral and anteroposterior weight distribution           in total trajectory length of COP among the rest
were used to evaluate the balance of body posture             position, centric occlusion, and masticating chewing
[11,12]. A four-quadrant weight distribution value            gum are shown in Fig. 5. The total trajectory length of
was measured in percentages (%) for every frame in            COP in the centric occlusion was significantly shorter
each trial (Fig. 4). First, the lateral weight distribution   than it was in the rest position. The total trajectory
and the anteroposterior weight distribution values            length of COP during masticating chewing gum was
for each frame were calculated. Next, the mean                significantly shorter than it was in the rest position
value of the sum of all lateral weight distribution           and in centric occlusion.


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                    Sakaguchi K, et al.
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                                                                                                      The results of the comparisons (median values)
Original Articles                                                                                     in the head and trunk sway values among the rest
                                                                                                      position, centric occlusion, and masticating chewing
                                                                                                      gum are shown in Fig. 8. The head and trunk sway
                                                                                                      values in the centric occlusion were significantly
                                                                                                      smaller than they were in the rest position. The head
                                                                                                      and trunk sway values during masticating chewing
                                                                                                      gum were significantly smaller than they were in the
                                                                                                      rest position and centric occlusion.



                      Figure 5. Comparison of total trajectory length of COP among rest
                    position (RP), centric occlusion (CO), and mastication of gum (MA).
                    Differences among RP, CO, and MA were tested with the Friedman’s
                    two-way analysis of variance (P < 0.05), and multiple comparisons was
                    assessed by the Bonferroni adjustment (0.05/3 = 0.016) after Wilcoxon
                    t-test. *: P<0.016, and n = 30. Medians (IQR) of RP, CO, and MA were as
                    follows: RP 40.2(34.4 - 45.9), CO 37.7(33.5 - 44.3), MA 36.2(29.6 - 42.4).

                    The median COP areas (Rectangle area, Outer
                                                                                                        Figure 8. Comparison of head and trunk sway values among RP, CO, and
                    peripheral area, Root mean square area) are shown in                              MA. *: P < 0.016, and n = 30. Medians (IQR) of RP, CO, and MA for head sway
                    Fig. 6. The median COP areas in the centric occlusion                             value were as follows: RP 0.18(0.16 - 0.23), CO 0.16(0.14 - 0.19), MA 0.15(0.12
                    were significantly smaller than it was in the rest                                - 0.19). Medians (IQR) of RP, CO, and MA for trunk sway value were as follows:
                    position. The median COP areas during masticating                                 RP 0.53(0.46 - 0.66), CO 0.45(0.41 - 0.57), MA 0.41(0.32 - 0.50).
                    chewing gum were significantly smaller than they
                    were in the rest position and centric occlusion.                                  4. DISCUSSION

                                                                                                      The results for the total trajectory length of COP
                                                                                                      (Fig. 5), COP areas (Rectangle area, Outer peripheral
                                                                                                      area, and Root mean square area) (Fig. 6), head and
                                                                                                      trunk sway values (Fig. 8) suggested that the body
                                                                                                      posture was significantly more stable when the
                                                                                                      subjects bit down in centric occlusion than when
                                                                                                      they maintained their mandibles in the rest position.
                                                                                                      Stability in the head position is indispensable to
                      Figure 6. Comparison of COP areas (rectangle area, outer peripheral             the control of the body posture. The anterior and
                    area, and root mean square area) among RP, CO, and MA. *:P<0.016, and             posterior cervical muscles are concerned with the
                    n=30. Medians (IQR) of RP, CO, and MA for rectangle area were as follows:         stability and movement of the head [21-24]. The
                    RP 1.6(0.8-1.9), CO 1.1(0.7-1.7), MA 0.8(0.5-1.1). Medians (IQR) of RP, CO, and
                    MA for outer peripheral area were as follows: RP 0.8(0.5-1.0), CO 0.6(0.5-0.8),
                                                                                                      loss of posterior occlusal support deprives the
                    MA 0.5(0.4 - 0.7). Medians (IQR) of RP, CO, and MA for root mean square area      stomatognathic system of valuable proprioceptive
                    were as follows: RP 0.8(0.5 - 1.0), CO 0.6(0.5 - 0.8), MA 0.5(0.4 - 0.7).         information, and likely alters muscle contraction
                                                                                                      patterns. These changes are reported to effect the
                    The results of the comparisons (median values) in                                 cervical muscles through the trigeminal nerve [16].
                    the lateral and anteroposterior weight distributions                              The cervical nerves C1 to C4 are primarily involved in
                    among the rest position, centric occlusion, and                                   controlling head posture [25] and the proprioceptive
                    masticating chewing gum are shown in Fig. 7. There                                inputs from the muscles and articulations of the
                    were no significant differences in the distribution                               neck are important in the maintenance of postural
                    of foot pressure among the rest position, centric                                 balance [26]. Stimulation of the vestibular system
                    occlusion, and masticating chewing gum.                                           by changing the head position has a descending
                                                                                                      influence on the triceps surae muscle and the soleus
                                                                                                      muscle, both antigravity muscles [27].
                                                                                                      Based on these previous reports, the stability of
                                                                                                      the head is maintained through the action of the
                                                                                                      cervical area. The present result found that the body
                                                                                                      posture was significantly more stable in the centric
                                                                                                      occlusion than in the rest position, and suggests that
                                                                                                      bilateral occlusal contacts in the centric occlusion
                                                                                                      caused a change bilaterally in the peripheral inputs
                                                                                                      from each organ in the stomatognathic system and
                     Figure 7. Comparison of lateral and anteroposterior weight distributions
                    among RP, CO, and MA. All comparisons were not significant (P>0.016), and
                                                                                                      resulted in improving both the stability of the neck,
                    n=30. Medians (IQR) of RP, CO, and MA for lateral weight distribution were        the head, and the trunk positions. Consequently,
                    as follows: RP 1.9(-0.8-3.4), CO 0.3(-1.1-2.4), MA 1.5(-0.5-2.6). Medians (IQR)   body posture was more stable when the subjects
                    of RP, CO, and MA for anteroposterior weight distribution were as follows:        bit down in the centric occlusion compared to when
                    RP 0.7(-5.5 - 5.7), CO -2.6(-5.4 - 5.4), MA -1.1(-4.0 - 5.9).                     they maintained in a muscular rest position.



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Effects of masticatory movements
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The results for the total trajectory length of COP (Fig. 5),   4.1 Limitations




                                                                                                                                      Original Articles
COP areas (Rectangle area, Outer peripheral area, and          This study has some limitations. The simultaneous
Root mean square area) (Fig. 6), head and trunk sway           measurements of head, trunk, and body sways were
values (Fig. 8) suggested that the body posture was            carried out to evaluate a relationship between the
significantly more stable when the subjects masticated         stomatognathic function and body posture in the
chewing gum than when they bit down in centric                 present study. However, analyses were not done on the
occlusion or they maintained their mandibles in a              motion analysis of the lower legs and muscle activities
muscular rest position.                                        in the head, neck, trunk, and lower legs. The future
Yagi et al. [26] reported that the leg muscles, which          direction of study should be to include the motion
directly regulate the movement of the ankle joint,             analysis of the lower legs and the analysis of electrical
and the dorsal neck muscles, which change the static           activities of craniocervical and whole body muscles to
equilibrium through the central nervous system,                elucidate the relationship between mastication and
are important for maintaining the standing posture.            body posture in detail. Moreover, it also needs further
Takahashi et al. [15] indicated that the H reflexes in         analysis on the subjects with the other patterns of
both the pretibial and soleus muscles undergo a                masticatory movement path other than Pattern I (the
nonreciprocal facilitation during mastication. Takada et       pattern of masticatory movement path with a linear or
al. [28] found the increase in amplitude of the pretibial      concave opening path and a convex closing path) [30].
and soleus H reflex showed a positive correlation with         Kushiro et al. [13] investigated the effect of masticating
the strength of teeth clenching. Lundgren and Laurell          chewing gum on the postural stability during upright
[29] confirmed on average 37% of the total maximal             standing, using only the force plate for postural
bite force in habitual occlusion was utilized during           assessment, and they suggested that mastication of
chewing. Moreover, Watanabe et al. [30] suggested that         chewing gum affects the postural control by enhancing
the pattern of masticatory movement path with a linear         the postural stability during upright standing. Goto et
or concave opening path and a convex closing path              al. [14] also conducted a similar study and reported that
(Pattern I) had the stability of the path and rhythm and a     the chewing gum indirectly affected postural control by
superior masticatory function compared to the pattern          influencing the vestibular function to stabilize posture
of the masticatory movement path with a similar open           during upright standing. Our results in the present study,
path to that in Pattern I and a concave closing path.          which were obtained by adding the motion analysis
The present results found that the body posture was
                                                               to the force plate analysis, corroborate these previous
significantly more stable when the subjects masticated
                                                               studies, and suggest that the jaw sensory motor system
chewing gum than when they bit down in centric
                                                               can modulate postural control mechanisms. Gum
occlusion or maintained their mandible in the rest
                                                               chewing activity can enhance postural stability during
position (Figs. 5, 6 and 8). Based on the previous reports
                                                               upright standing in healthy young adults. Detailed
[15,26,28-30], one can infer that when the subjects
                                                               investigations on the mechanism underlying these
masticated chewing gum, the occlusal force might
                                                               effects should be performed in future studies. Our
have been larger compared to it in centric occlusion,
and the pattern of the masticatory movement path               findings could be taken into consideration in treatment
had the stability of the path and rhythm and a superior        and rehabilitation planning for some patients with
masticatory function. Moreover, the present results            postural instability due to balance disorders.
showed the possibility that the peripheral inputs from
each organ in the stomatognathic system during                 5. CONCLUSION
mastication may have strongly affected the muscles,
pretibial and soleus muscle, and the upper central             Masticatory movements affect the head, trunk, and
nervous system, which regulate the craniocervical              body sways and enhance the postural stability during
muscles, as the positive feedback control to maintain          standing position.
and stabilize the standing posture. Namely, a positive
impact to the posture control system during mastication        CONFLICT OF INTEREST
may have extended to both the upper and lower                  No potential conflict of interest was reported by the authors.
extremities. Consequently, the mastication movement
may have affected the postural control by enhancing            FUNDING
the postural stability standing position.                      This study was supported by JSPS KAKENHI Grant Numbers
Stable human standing is usually considered to depend          JP15K11188 and JP19K10219.
on an integrated reflex response to vestibular, visual,
and somatosensory input [31]. When the center of               AUTHOR CONTRIBUTIONS
gravity changes its position in space, the neuromuscular       KS: data gathering and analysis, literature collection and writing
system must compensate so that the center of gravity           some parts of manuscript. KS: concept and design, protocol,
remains in a balanced position [21]. The present results       data gathering and analysis, their interpretation and drafting the
found that there were no significant differences in            manuscript, manuscript revision and submission. NRM: concept
the distribution of the foot pressure among the rest           and design, data interpretation, critical revision of the manuscript
position, centric occlusion, and masticating chewing           for important intellectual content. TM: technical support of the
gum anteroposteriorly and laterally (Fig. 7). These            measurement system. LPC: concept and design, critically revised
results suggest that changes in mandibular position and        the manuscript. AY: administrative, technical, and material
masticating chewing gum did not affect the postural            support; study supervision. All authors read and approved the
balance anteroposteriorly and laterally.                       final manuscript.



Stoma Edu J. 2022;9(3-4): 81-87                                                   pISSN 2360-2406; eISSN 2502-0285                        85
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    86              Stoma Edu J. 2022;9(3-4):81-87                                                           pISSN 2360-2406; eISSN 2502-0285
Effects of masticatory movements
                                                                                                                                   www.stomaeduj.com




                                                                             Kiwamu SAKAGUCHI




                                                                                                                                 Original Articles
                                                                       DMD, MDS, MS, Associate Professor
                                  Division of Oral Functional, Department of Oral Functional Prosthodontics
                                                                       Graduate School of Dental Medicine
                                                                                        Hokkaido University
CV                                                                                  Kita-ku, Sapporo, Japan
Kiwamu Sakaguchi is an Associate Professor at the Department of Oral Functional Prosthodontics, Division of Oral Functional
Science, Graduate School of Dental Medicine, Hokkaido University, Japan. He received his DDS at the Hokkaido University in
1995 and his PhD from the same university in 1999. He joined the Craniofacial Pain Center at Tufts University where he engaged
in research from 2003 till 2004.


Questions
1. What other movements are involved in mastication besides the simple sequential
jaw-opening and jaw-closing movements?
qa. Complex tongue movements;
qb. Coordination of lip, and cheek movements;
qc. Head movement to facilitate the intraoral transport of food from ingesting to swallowing;
qd. All.

2. Which of the following is not an inclusionary criteria for this study?
qa. No history of head and neck or back problems;
qb. No history of signs and symptoms of temporomandibular disorders or orofacial pain;
qc. No history of orthopedic or otolaryngologic problems affecting body balance;
qd. Malocclusion.

3. WWhich statistical tests were used to assess comparisons of the data in this study?
qa. Friedman’s two-way analysis of variance;
qb. Wilcoxon t-test with Bonferroni correction;
qc. Both;
qd. None.

4. Which of the following is a conclusion of this study?
qa. Masticatory movements affect head, trunk, and body sways and enhance the postural stability during
standing position;
qb Masticatory movements affect head, trunk, and body sways and deteriorate the postural stability during
standing position;
qc. Jaw clenching affect head, trunk, and body sways and enhance the postural stability during standing
position;
qd. Bruxism affect head, trunk, and body sways and enhance the postural stability during standing position.




Stoma Edu J. 2022;9(3-4): 81-87                                                  pISSN 2360-2406; eISSN 2502-0285                    87