Content uploaded by C.C. Gage
Author content
All content in this area was uploaded by C.C. Gage on Nov 05, 2019
Content may be subject to copyright.
Effects of mouthguards on vertical dimension,
muscle activation, and athlete preference:
a prospective cross-sectional study
C. Colby Gage, DMD, DHEd n Kellie C. Huxel Bliven, PhD, ATC n R. Curtis Bay, PhD n Jeremiah S. Sturgill, DMD, MPH, DHEd
Jae Hyun Park, DMD, MSD, MS, PhD
Mandibular repositioning and subsequent neuromuscular signaling are
proposed mechanisms of action for commercial mouthguards marketed
for performance enhancement. A prospective cross-sectional study of
24 healthy adult weightlifters with normal occlusal relationships was
designed to determine whether 2 self-fit performance mouthguards; a
custom-fabricated, bilaterally balanced, dual-laminated mouthguard; and no
mouthguard (control) differed in their effects on vertical dimension, muscle
activation, and user preference during a 75% maximum power clean lift.
Each subject was tested for each of the mouthguard categories: Power
Balance POWERUP, Under Armour ArmourBite, custom, and no mouthguard.
Interocclusal distance was measured at baseline and with each
mouthguard. Mean and peak activity of the anterior temporalis, masseter,
sternocleidomastoid, and cervical paraspinal muscles was measured dur-
ing sitting and during a 75% maximum power clean lift. A mouthguard
preference questionnaire was completed. Analyses were conducted to
determine whether interocclusal distance differed among mouthguard
type and to examine the effect of mouthguard type on mean and peak
muscle activation during the clean lift. Interocclusal distance was affected
by mouthguard type (
P
= 0.01). Mean and peak activity of the anterior
temporalis and masseter muscles and mean activity of the sternocleido-
mastoid muscle differed among mouthguards (
P
< 0.05). Mouthguard
type did not influence muscle activation of the cervical paraspinal muscle
group. Overall, the Power Balance mouthguard produced more muscle
activity. Participants preferred custom mouthguards nearly 2:1 over self-fit
performance mouthguards (
P
= 0.05). Participants perceived that they
were stronger and were less encumbered when using a custom mouth-
guard during submaximum power clean lifts.
Received: June 1, 2015
Accepted: June 29, 2015
Key words: anterior temporalis muscle, interocclusal distance, masseter
muscle, mouthguard, paraspinal muscles, sternocleidomastoid muscle,
The relationship between optimal man-
dibular position and muscular strength
among trained athletes has been
reported.1 Stenger theorized that optimal
positioning of the temporomandibular
joint (TMJ) with a mandibular ortho-
pedic repositioning appliance improved
the position of the cervical vertebrae and
promoted proper cranial nerve signaling,
affecting muscular performance in the
extremities.1 Various designs of mandibular
orthopedic repositioning appliances have
been reported to reposition the mandible
so as to increase the vertical dimension,
which theoretically prevents overload-
ing of the joint and decreases aberrant
vascular and neurological signaling from
the stomatognathic system.2-6 This optimal
positioning of the mandible enhances
posture and ultimately muscular activation
and performance in the rest of the body.2-6
These proposed muscular and neurological
benefits of mandibular repositioning have
been researched in subjects with symptom-
atic and asymptomatic muscles and TMJ
dysfunction.6-8 However, the physiological
effects of mandibular repositioning in a
healthy population are still unclear.9
Studies using surface electromyography
(EMG) have been conducted to better
understand how mandibular reposition-
ing can elicit a neuromuscular response.
Neuromuscular splinting seeks to restore
the optimal length-tension relationship of
the muscles of mastication, as evidenced by
increases in occlusal force, muscle activa-
tion, and normalization of TMJ function-
ing. EMG of the muscles of mastication as
well as the sternocleidomastoid (SCM), tra-
pezius, and cervical flexor muscles during
maximum-effort jaw clenching in different
mandibular positions demonstrates a pos-
sible link between mandibular position
and muscular enhancement in the rest of
the body.7,10-12 An increase in the vertical
dimension of occlusion in individuals with
derangements of the TMJ complex has
been shown to increase EMG activation, in
that jaw clenching increases activity in the
anterior temporalis and superficial masseter
muscles.13 The activity of the trapezius and
sternocleidomastoid muscles has also been
shown to increase 7 to 33 times during
clenching compared to during rest, which
could account for improved performance
during dynamic movements.14
The relationship between increased activ-
ity of the muscles of mastication in healthy
individuals and athletic performance is
still largely unknown and has only recently
resurfaced in the literature.15,16 Few studies
have attempted to correlate their findings
on athletic performance with data gathered
from the changes in dental occlusion or
muscle activity.17 Given that many con-
tact sports require the use of a maxillary
mouthguard, the use of an oral appliance
that favorably repositions the mandible
and provides orofacial protection would
serve 2 purposes. Similarly, healthy indi-
viduals participating in noncontact sports,
such as weightlifting, might benefit from
increases in muscle activation resulting
from use of a mouthguard.
The quest for a custom or self-fit
mouthguard that would provide both ben-
efits has been a driving factor in consumer
marketing in recent years.6,18 Two com-
mercially available self-fit mouthguards,
Under Armour ArmourBite Mouthguard
(UA; Under Armour, Inc.) and Power
Balance POWERUP Mouthgear (PB;
Power Balance Technologies, Inc.), use
proprietary inserts that claim to impart
Sports Dentistry & Mouthguards
48 November/December 2015 General Dentistry www.agd.org
performance-enhancing properties.19,2 0
The primary purpose of the present
study was to determine the effect of
self-fit UA and PB and a custom (CUS),
dual-laminated, bilaterally balanced
mouthguard on vertical dimension and
head and neck muscle activation during
a dynamic athletic movement in healthy,
physically active individuals. The power
clean lift was specifically chosen because
of its widespread use among the projected
participant population.
Although coaches and athletes are aware
of the need for mouthguard protection
during contact sports, many athletes
have chosen not to wear mouthguards
because of discomfort, breathing difficulty,
speech difficulties, or lack of availabil-
ity.21-25 Protective mouthguards do not
appear to negatively affect heart rate, gas
exchange, and power production; a psycho-
logical barrier may be the greatest impedi-
ment.18,21,23,26,27 The secondary purpose of
this study was to assess participants’ percep-
tions of each mouthguard type in relation
to its perceived effect on strength, explosive
power, and exertion; its comfort; their
overall preference; and their willingness to
use it during practice and competition.
Materials and methods
Design
This study used a prospective cross-
sectional study design. The independent
variable was mouthguard type: PB
(Fig. 1), UA (Fig. 2), CUS (Fig. 3), and,
as control, no mouthguard (NMG). The
dependent variables were interocclusal dis-
tance; normalized mean and peak muscle
activation of the anterior temporalis,
masseter, SCM, and cervical paraspinal
muscles during a 75% maximum power
clean lift; and participant preferences for
the various types of mouthguards while
performing a 75% maximum power clean
lift. Specifically, participants ranked the
4 conditions (3 mouthguards and control)
with respect to perceived strength, per-
ceived explosive power, ease of use, and
comfort. Participants also used a 5-point
Likert scale to indicate how likely they
would be to use any mouthguard during
regular practice or during competition.
Last, participants indicated which of the
3 mouthguards they preferred to use for
regular practice and competition.
Participants
Twenty-four (14 male and 10 female)
healthy, physically active individuals
participated. The mean age of participants
was 32.2 (SD, 7.3) years; mean height
was 173.4 (SD, 8.8) cm; mean weight was
77.5 (SD, 12.1) kg. To be included in the
study, participants had to be at least 18
years of age, an experienced weightlifter
(defined as having a minimum of 2 years
of experience), and currently involved in
regular weightlifting, including the power
clean lift, more than 3 days per week. The
participants were currently in good health,
had no current acute or chronic illnesses,
and were free of musculoskeletal injuries
for at least 1 month prior to testing.
Exclusion criteria included absence of the
Fig. 1. Power Balance POWERUP Mouthgear. Fig. 2. Under Armour ArmourBite Mouthguard. Fig. 3. Custom dual-laminated, bilaterally balanced
mouthguard.
www.agd.org General Dentistry Special sports dentistry section 49
first molars; presence of a removable oral
prosthesis; open or impinging deep bite;
TMJ or muscle pain on palpation; previ-
ous diagnosis of internal derangements
of the TMJ; medical disorders that might
affect muscle function, such as arthralgias
or myalgias; and presence of a significant
(greater than 2-mm) centric slide. The
local institutional review board approved
the study, and all participants provided
informed consent.
Electromyography
The MyoSystem 1200 EMG acquisition
system (Noraxon U.S.A., Inc.) was used
to record surface EMG activity simul-
taneously from the anterior temporalis,
masseter, SCM, and cervical paraspinal
muscles during maximum-effort occlu-
sion and power clean lift tests. A single-
ended amplifier was used (impedance >
10 MW; gain, 1000) with a fourth-order
Butterworth filter (10-500 Hz) and a
common mode rejection ratio of 130 dB.
A receiver with a sixth-order filter (gain,
2; total gain, 2000) was used to further
amplify the signal. The signal was passed
to a computer through a 16-channel
NorBNC connector system and a 12-bit
analog-to-digital card (Noraxon U.S.A.,
Inc.). The sampling rate was 1000 Hz.
EMG files were stored on the computer
and MyoResearch software (version
MR-XP 1.07, Noraxon U.S.A., Inc.) was
used for processing and analysis. Data
were full-wave rectified (ie, linear envelope
detection), integrated with a sixth-order
Butterworth filter, and smoothed over a
15-ms moving window (version MR-XP
1.07, Noraxon U.S.A., Inc.).
The peak of 3 maximum voluntary
isometric contractions (MVICs) was
averaged for each muscle and used for
normalizing EMG in the seated occlusion
and power clean lift tests. The mean and
peak EMG data for each muscle during
the maximum-effort jaw clenching and
75% maximum power clean lift tests were
normalized as a percent of MVIC.
Procedures
Participants attended 2 sessions. During
the first session, participants completed
paperwork, including informed consent,
biographical information, and self-
reported 1-repetition maximum effort in
the power clean lift. Next, each participant
received an extraoral examination, which
consisted of a review of the medical and
dental health history, head and neck
muscle palpation, and observation of man-
dibular mobility.
A single investigator (CCG) recorded
intraoral measurements of each partici-
pant. Interocclusal distance was used to
measure changes in vertical dimension of
the jaws induced by each mouthguard.
Initial interocclusal distance of jaws at
rest was measured at the central incisors
with an intraoral ruler. This measurement
was taken while the patient was sitting,
maintaining a natural head position,
and repeating the word emma 3 times
to attain a predictable rest position of
the mandible. Other intraoral measures,
taken for descriptive purposes, included
the maximum overjet of the maxillary
teeth and maximum overbite. All mea-
surements were recorded to the nearest
0.50 mm (Table 1).
Following the extraoral and intraoral
examinations, maxillary and mandibu-
lar alginate impressions were taken for
fabrication of the custom mouthguards.
Sufficient vestibular detail was obtained to
allow optimal fit of the final mouthguards.
Regisil polyvinylsiloxane occlusal registra-
tion material (DENTSPLY International)
was used intraorally to capture occlusal
registration. The casts were poured imme-
diately in high-detail die stone and used to
fabricate the custom mouthguards.
The custom mouthguards were con-
structed from a 3-mm-thick clear ethylene
vinyl acetate that was laminated over
the dental cast at 90 psi on a Drufomat
Scan Pressure Machine (Dreve Dentamid
GmbH). A second, 1-mm-thick layer of
clear ethylene vinyl acetate was placed on
Table 1. Baseline intraoral
measurements of participants
(N = 24).
Measurement Mean (SD)
95% Confidence
interval
Overbite (mm) 2.58 (0.65) 3.23-1.94
Overbite (%) 3 3.13 (10. 63) 43.76-22.49
Overjet (mm) 2.79 (0.93) 3.26 -2.32
Interocclusal
distance (mm)
3.54 (0.93) 4.46-2.62
Table 2. Surface electrode placement and maximum voluntary isometric
contraction (MVIC) test position.
Muscle Electrode placement28 MVIC test position29
Anterior temporalis Electrodes were placed vertically over
the midbelly, just above the zygomatic
arch.
While seated, the participant clenched
the teeth and performed a maximum-
effort bite.
Masseter Electrodes were placed vertically
along the muscle fiber, at the midpoint
between the zygomatic arch and angle
of mandible.
While seated, the participant clenched
the teeth and performed a maximum-
effort bite.
Sternocleidomastoid Electrodes were placed obliquely,
mid-distance between the mastoid
process and sternal notch and slightly
posterior to the muscle belly.
While the par ticipant was seated, the
head was rotated to the opposite side
and resistance was applied to the lateral
aspect of the face.
Cervical paraspinals Electrodes were placed vertically and
approximately 2 cm lateral to the spine
in the midcervical region (approxi-
mately at C4) over the muscle belly.
While the par ticipant was seated, the
head was extended from a neutral
position and resistance was applied to
the posterior head (in the area of the
external occipital protuberance).
Sports Dentistry & Mouthguards Effects of mouthguards on vertical dimension, muscle activation, and athlete preference
50 November/December 2015 General Dentistry www.agd.org
the posterior (first premolar to second
molar) occlusal surfaces of the mouth-
guards. The occlusal registration was then
used to mount the maxillary and mandibu-
lar casts of each mouthguard on an articu-
lator. Each mouthguard was trimmed and
polished, and the opposing occlusion was
indexed into the mouthguard at approxi-
mately 3 mm of posterior opening.
Participants were instructed and super-
vised in fitting of PB and UA mouth-
guards. The manufacturers’ instructions
for boil time and oral adaptation tech-
niques were followed.
The second session was conducted
in a neuromuscular research laboratory
for performance tests (maximum-effort
occlusion and 75% maximum power
clean lift) 2 weeks after the initial session.
At this time, all mouthguards were veri-
fied for adequate retention during mouth
opening. An intraoral ruler was used to
measure the distance between the maxil-
lary mouthguard and the mandibular
incisors to determine the interocclusal
distance for each mouthguard.
Participants were prepared for EMG
measurements; preparation included
shaving the skin surface to remove any
overlying hair and cleaning the skin with
a 70% isopropyl alcohol swab to mini-
mize skin impedance. Self-adhesive silver/
silver chloride surface electrodes with
a 10-mm diameter and 10-mm inter-
electrode distance were used (Noraxon
U.S.A., Inc.). Bipolar surface electrodes
were placed on the skin overlying the
anterior temporalis, masseter, SCM, and
cervical paraspinal muscles, and a refer-
ence electrode was placed on the clavicle
(Tabl e 2).28 Correct placement of all
electrodes was confirmed by monitoring
activity during a maximum-effort occlu-
sion (anterior temporalis and masseter) or
isolated muscle testing (SCM and cervi-
cal paraspinal) by EMG signal identifica-
tion on an oscilloscope.
After proper electrode placement was
confirmed, standardized manual muscle
testing procedures were used to record an
MVIC for each muscle (Table 2).29 Prior
to each test, the myoelectric signal was
calibrated with the participant in a relaxed,
seated position to establish baseline EMG
activity. During MVIC tests, participants
were instructed to provide maximum
clenching or to resist with maximum effort
against the investigator’s manual resistance
for 5 seconds. The average of 3 MVICs for
each muscle was used for EMG normaliza-
tion during data processing.
Following MVIC tests, participants
performed maximum-effort occlusion tests
with each mouthguard while EMG data
were collected for each muscle. Sitting in
a comfortable position, participants were
instructed to bite (clench) using maximum
effort for 5 seconds. Three repetitions of
occlusion EMG were collected for each
type of mouthguard and the control con-
dition. The order of mouthguards used
during testing was randomized to reduce
order effect across participants. The nor-
malized mean EMG during clenching was
used in data analyses.
Next, participants performed 75%
maximum power clean lifts under each
condition while EMG data were collected
for each muscle. The power clean lift
was performed as the participant lifted
the bar from the ground to the level of
the clavicles in a fluid, explosive manner.
A triaxial accelerometer (NeuwGhent
Technology) was attached to the bar to
track its movements during the power
clean lift. The accelerometer measured
±10 g in each axis (x, y, and z) with a
500-Hz bandwidth and sensitivity of 200
mV/g. Leads, 1 per axis, were connected
into NorBNC analog input channels
and into a personal computer, where the
results were displayed using MyoResearch
software (version MR-XP 1.07, Noraxon
U.S.A., Inc.). The accelerometer signals
were synchronized with EMG data and
later used to mark the start and end of
the power clean lift.
Participants completed a perception
form at the end of the lifts. The form was
developed by the study investigators and
consisted of several single-item questions.
Participants ranked, in order from 1 to 4,
the 4 conditions (3 mouthguards and no
mouthguard control) with regard to each
of the following parameters: perceived
strength, perceived explosive power, ease
of use, and comfort. Participants also
used a 5-point Likert scale (1, very likely;
5, very unlikely) to indicate how likely
they would be to use any mouthguard
during regular practice and during
competition. The participants were also
asked an open-ended question at the end
to specify the characteristics of their least
favorite mouthguard, if one existed.
Statistical analysis
Descriptive and inferential analyses were
performed on collected data. A 1-way
analysis of variance with repeated measures
was used to determine whether interoc-
clusal distance differed among the 4 condi-
tions (PB, UA, CUS, and NMG).
A mixed linear model with random
effects for participants was used to exam-
ine the mean and peak muscle activation
during the 75% maximum power clean
lift across mouthguard type (fixed factor)
while controlling for maximum-effort
occlusal force muscle activation (covari-
ate). Effectively, muscle activation during
the lift was “normalized” for each partici-
pant by controlling for his or her muscle
activation while biting the mouthguard in
a nonlift mode. Hence, a significant result
for these analyses may be interpreted as
a significant difference between mouth-
guards when results have been controlled
for normalized activation within the
individual. Bonferroni-corrected pairwise
comparisons were used for post hoc
analyses. Data were logged due to non-
normality of the distributions and back
transferred to geometric means.
Freidman nonparametric tests were used
to determine whether participant percep-
tions differed among the 4 conditions. The
α level was established a priori at 0.05,
2-tailed. Data were analyzed with SPSS
software (version 22.0, IBM Corporation).
Table 3. Mouthguard type and
interocclusal distance (N = 24).
Mouthguard
Mean (SE)
interocclusal
distance (mm)
95%
Confidence
interval
NMG 3.54 (0.46 ) 2.62-4.46
PB 5.33 (0.46)a4.41-6.25
UA 3.52 (0.46) 2.60-4.44
CUS 3.69 (0.46) 2.77-4.61
Abbreviations: CUS, custom mouthguard; NMG, no
mouthguard (control); PB, Power Balance POWERUP
Mouthgear; UA, Under Armour ArmourBite Mouthguard.
aSignificantly different from no mouthguard
(
P
= 0.001), Under Armour mouthguard (
P
= 0.001),
and custom mouthguard (
P
= 0.006).
www.agd.org General Dentistry Special sports dentistry section 51
Results
Interocclusal distance
The type of mouthguard evaluated had a
statistically significant effect on interoc-
clusal distance (P < 0.001). PB produced
the largest interocclusal distance, 5.33 mm
(SE, 0.46 mm), which was significantly
greater than that of the CUS (P = 0.006),
NMG (P = 0.001), and UA (P = 0.001)
values (Table 3).
Muscle activation
Mean and peak muscle activation values
for anterior temporalis, masseter, SCM,
and cervical paraspinal muscles are pre-
sented in Table 4 and Charts 1 and 2. The
mouthguard had a statistically significant
effect on mean activation of the anterior
temporalis muscle (P = 0.002) and no
significant effect on its peak activation
(P = 0.46). Mean activation of the anterior
temporalis muscle was significantly greater
with PB than with either CUS (P = 0.002)
or NMG (P = 0.05). CUS elicited signifi-
cantly greater mean activation of the ante-
rior temporalis than did UA (P = 0.03).
The mouthguard had a significant
effect on mean (P = 0.001) and peak
(P = 0.03) activation of the masseter
muscle. PB elicited significantly greater
mean (P = 0.002) and peak (P = 0.019)
activation of the masseter than did UA
and greater mean activation than did
NMG (P = 0.015). CUS elicited signifi-
cantly greater mean activation of the mas-
seter than did UA (P = 0.05).
The mouthguard had a significant effect
on mean activation of the SCM muscle
(P = 0.014) and no significant effect on its
peak activation (P = 0.073). PB produced
significantly greater mean activation of the
SCM than did NMG (P = 0.01).
The mouthguard had no statistically
significant effect on mean (P = 0.47) or
peak (P = 0.78) activation of the cervical
paraspinal muscles.
Perceptions of mouthguards
There was a statistically significant dif-
ference (P = 0.03) in how participants
ranked the lifting condition (PB, UA,
CUS, NMG), based on perceived
strength, from strongest (1) to weakest
(4). Participants perceived themselves as
strongest while using CUS (mean rank,
1.9), followed by UA (mean, 2.4) and
NMG (mean, 2.8), and weakest using
the PB mouthguard (mean, 2.9). There
was no statistically significant difference
in participants’ ranking based on their
perception of explosive power; that is,
most powerful to least powerful did not
differ (P = 0.07). There was a significant
difference (P = 0.049) in participants’
ranking of their perception of ease of
completion from easiest (1) to hardest (4).
Participants perceived use of the CUS
mouthguard to result in the easiest lifting
condition (mean, 2.1), followed by NMG
(mean, 2.4) and UA (mean, 2.4). Lifting
was ranked as hardest to complete when
PB was used (mean, 3.1).
Participants’ ranking of mouthguards for
perceived comfort, from most comfortable
(1) to least comfortable (4), did not differ
significantly (P = 0.17). The 3 mouthguards
and control achieved the following mean
ranks: CUS, 2.2; UA, 2.8; PB, 2.7; and
NMG, 2.2. However, common responses
to the open-ended question about charac-
teristics of the individual participant’s least
favorite mouthguard indicated that the pad
of PB and the shape of UA were uncom-
fortable. These participants reported that
the mouthguard felt too big, they could
not close their mouth, or it was difficult to
bite or clench when wearing PB or UA.
When asked if they would use a mouth-
guard for practice, athletes provided the
following responses: very unlikely, 4.2%;
not likely, 16.7%; neutral, 33.3%; likely,
37.5%; very likely, 8.3%. For competi-
tion, participants predicted the following
levels of usage: not likely, 16.7%; neutral,
41.7%; likely, 25.0%; very likely, 16.7%.
No respondents indicated that they would
be very unlikely to use a mouthguard
during competition.
Participants indicated a significantly
greater preference (P = 0.049) for a custom
mouthguard (54.2%) over UA (16.7%),
PB (25.0%), or NMG (4.2%).
Discussion
The purpose of the current study was to
investigate differences in interocclusal
distance, head and neck muscle activation
during 75% maximum power clean lifts,
Table 4. Mean and peak muscle activation (% MVIC) during power clean lift, by mouthguard type.
Mouthguard
Anterior temporalis Masseter Sternocleidomastoid Cervical paraspinals
Mean (SE) Peak (SE) Mean (SE) Peak (SE) Mean (SE) Peak (SE) Mean (SE) Peak (SE)
PB 10.4 (1.2 ) 66 .9 (1.1) 18 .3 (1.2 ) 31.0 (1.2) 27.1 (1.2 ) 63.2 (1.2) 45.6 (1.2) 93.0 (1.2)
95% CI 7.3 -14. 9 58. 4-76. 8 11.7-28.7 21.4 -44.9 19.7-37.2 45.7-87.4 32.6-63.5 63.5 -13 6. 2
UA 6.7 (1.2) 71.2 (1.1) 11.0 (1.2) 21.4 (1.2) 21.5 (1. 2) 48 .5 (1.2) 44.7 (1.2) 85.4 (1.2)
95% CI 4.7-9.6 62.0-81.7 7. 0 -18.2 14. 8 -31.1 15 .6 -2 9.5 35.0-67.0 32.0-62.3 5 8 .4-124.7
CUS 9.0 (1.2) 68 .6 (1.1) 15.2 (1.2) 27. 4 (1. 2) 27.4 (1.2 ) 59.4 (1.2) 53.4 (1.2 ) 97.9 ( 1. 2)
95% CI 6.3-12.9 59. 9-78.7 9.6-23.9 18.8-39.8 19.9-37.6 42.9-82.2 38.4-74.2 6 7. 3-142. 5
NMG 8.0 (1.2 ) 62 .5 (1.1) 11.7 (1.3) 23.0 (1.2) 18.5 (1.2) 41.9 (1.2) 4 0.5 (1.2 ) 86.7 (1.2)
95% CI 5.6-11.4 54.7-71.6 7. 4 -18. 7 15.7-33.7 13.6-25.4 30 .5-5 7.7 29.0-56.5 59.2 -126 . 8
Abbreviations: CI, confidence interval; CUS, custom mouthguard; MVIC, maximum voluntary isometric contraction; NMG, no mouthguard (control);
PB, Power Balance POWERUP Mouthgear; UA, Under Armour ArmourBite Mouthguard.
Sports Dentistry & Mouthguards Effects of mouthguards on vertical dimension, muscle activation, and athlete preference
52 November/December 2015 General Dentistry www.agd.org
and mouthguard perceptions and prefer-
ences among healthy, athletic individuals
using different types of mouthguards.
The desire to transform a protective
mouthguard for contact sports into a
specialized appliance for performance and
strength has prevailed among coaches and
athletes seeking a competitive edge.24,30,31
Performance mouthguards such as the
commercially available maxillary mouth-
guards tested in this study are designed with
the premise that an increase in posterior
thickness will open the lower airway and
optimize afferent and efferent signaling from
the sensorimotor system. It has been recom-
mended that, for contact sports, a mouth-
guard that is 6 mm thick be constructed if
the interocclusal distance is 5 mm.1
The custom mouthguard used in this
study was dual laminated with a pressure
laminator and was bilaterally balanced on
a dental articulator in accordance with the
athlete’s habitual occlusion. This design
allowed for an even distribution of biting
forces along the mouthguard and had a
final posterior thickness of approximately
3.0-3.5 mm. Measured from the mouth-
guard to the mandibular incisors, the mean
vertical openings induced by the mouth-
guards in this study were CUS, 3.69 mm;
PB, 5.33 mm; and UA, 3.52 mm. Control,
the measurement taken without a mouth-
guard, was 3.54 mm.
Lindauer et al showed that increases in
muscle activity for both the masseter and
temporalis muscles are associated with
increases in voluntary maximum occlusal
force between 9 and 11 mm of opening
(measured at the first molar).32 Arima et
al studied the effect of vertical dimension
on occlusion and EMG activity of the
masseter muscle in healthy participants.33
Their results indicated that the greatest
force during maximum clenching occurred
when the vertical distance between the
first molars measured 8 mm. As the verti-
cal dimension increased and approached
20 mm, both the EMG activity of the
masseter muscle and the occlusal force
generated decreased. It is important to note
that the distances measured by Lindauer et
al and Arima et al would have been greater
had they measured between the maxillary
and mandibular incisors instead of between
the molars.32,33 The goal of the present
study was to observe the activation of the
anterior temporalis, masseter, SCM, and
cervical paraspinal muscles in response to
a change in mandibular position during
a dynamic and practical sport-oriented
anaerobic movement while controlling
for baseline (seated, maximum-force)
activation. Surface EMG provides a reli-
able, noninvasive approach that indirectly
measures nervous signaling and muscle
fiber recruitment in a way that was suitable
for the purposes of this study.34 Other neu-
romuscular pathways, such as decreasing
joint loading and improving TMJ proprio-
ception, are difficult to measure and cannot
be determined through noninvasive mea-
sures.35,36 If an increase in overall muscular
performance should be expected through
the use of a specially designed mouth-
guard, then the mechanism should include
Chart 1. Mean muscle ac tivation during power clean lift, by mouthguard type.
Error bars represent SE.
a
P
≤ 0.05, b
P
≤ 0.01
Abbreviations: CUS, custom mouthguard; MVIC, maximum voluntary isometric contraction; NMG, no mouthguard (control);
PB, Power Balance POWERUP Mouthgear; SCM, sternocleidomastoid; UA, Under Armour ArmourBite Mouthguard.
Chart 2. Peak muscle activation during power clean lift, by mouthguard type.
Error bars represent SE.
a
P
≤ 0.05
Abbreviations: CUS, custom mouthguard; MVIC, maximum voluntary isometric contraction; NMG, no mouthguard (control);
PB, Power Balance POWERUP Mouthgear; SCM, sternocleidomastoid; UA, Under Armour ArmourBite Mouthguard.
www.agd.org General Dentistry Special sports dentistry section 53
60
50
40
30
20
10
0 Anterior temporalis Masseter SCM Cervical paraspinals
Muscle
Normalized mean activation (% MVIC)
PB
UA
CUS
NMG
a
a
b
a
b
a
b
120
100
80
60
40
20
0 Anterior temporalis Masseter SCM Cervical paraspinals
Muscle
Normalized peak activation (% MVIC)
PB
UA
CUS
NMG
a
concurrent activation potentiation of mus-
cles directly affected by the oral appliance
as well as muscles around the head and
neck complex. This relationship has been
described as the craniocervical-mandibular
system.12 A recent meta-analysis describing
this association found only articles of poor
quality that generally lacked consideration
for practical significance.16
Subtle changes in the position of the
mandible can have significant effects on
muscle function.35,37 During explosive
movements such as the power clean lift,
variations in technique as well as starting
and ending posture (neutral head posture
vs extended neck posturing) could also
affect muscle activation trends. The fibers
of the anterior temporalis muscle run
nearly perpendicular to the occlusal plane,
which make them particularly responsive
to changes in vertical dimension of the
mandible.38 The superficial masseter
muscle runs at a slightly oblique angle
from its attachment at the inferior border
with the zygoma, which helps stabilize the
maxillomandibular relationship during
explosive athletic movements.
In the present study, mean muscle
activation of the anterior temporalis
and masseter muscles was significantly
influenced by mouthguard type, leading
toward an increase in activity during the
power clean lift compared to control. In
a similar sample of healthy participants,
a 2-mm vertical increase of the mandible
caused EMG activity of the masseter,
temporalis, and SCM muscles to decrease
during seated rest and maximum clench-
ing efforts.12 The earlier results differ from
those in the present study, likely due to
the functional demands on the head and
neck during the power clean lift. As far as
the authors of the present study are aware,
this is the first study to measure muscle
activation in athletes using maxillary
mouthguards during a powerlift.
The SCM is a bilateral flexor and unilat-
eral rotator of the neck. Mean SCM acti-
vation was significantly influenced only by
PB, which had the greatest mean vertical
repositioning effect. Increases in isometric
strength of the cervical flexors have been
reported in deep bite patients with TMJ
dysfunction who are provided with a bite-
elevating appliance that creates a vertical
dimension 24%-42% greater than habitual
occlusion.7 In healthy patients, arbitrary
increases in vertical dimension from 2-12
mm have been reported to increase isomet-
ric cervical flexion while the individual is
seated clenching in a mandibular ortho-
pedic repositioning appliance; a decrease
in flexion is noted as vertical dimension is
increased further.17 It is unclear how the
functional demands of the power clean lift
would influence activation of the SCM
and why only 1 mouthguard had a signifi-
cant influence on its activation.
The cervical paraspinal muscles make
up vertical fibers of the upper trapezius
and erector spinae muscles involved with
neck extension. In the present study, the
presence of a mouthguard had no signifi-
cant effect on cervical paraspinal muscle
activation, which suggests that further
research is needed to determine if these
muscles are modulated by oral appliances
during a powerlift.
The authors are not aware of any long-
term observation of healthy athletes using
performance mouthpieces or mouth-
guards similar to those used in the present
study. It is possible that prolonged use
could lead to transient muscle deprogram-
ming, as has been observed with continu-
ous splint wear.39
The present study compared qualitative
data on 2 commercially available self-fit
mouthguards (UA and PB), 1 custom-
fabricated mouthguard (CUS), and no
mouthguard (NMG) while athletic adults
performed submaximum power clean
lifts. Participants perceived that they were
strongest (mean rank 1.9 out of 4.0) and
reported that the lifts were easiest (rank
2.1) while using CUS. Design features of
CUS allowed consistent vestibular adapta-
tion rather than the variable adaptation
common with self-fit mouthguards. In
addition, the participant’s occlusion was
indexed on the biting surface of CUS with
a dental articulator, while PB and UA had
flat surfaces. These design features may
have contributed to overall preference for
CUS but did not contribute to statistically
significant differences in comfort during
the power clean lift.
The majority (37.5%) of participants
were likely to use 1 of the mouthguards
provided during regular practice. However,
when the athletes were asked the likeli-
hood of using a mouthguard during
competition, the majority (41.7%) were
neutral. The participants were largely
inexperienced with mouthguards in gen-
eral, and their responses indicated some
level of hesitation to compete while wear-
ing an unfamiliar appliance. Only 16.7%
reported that they were not likely to use
the provided mouthguards.
When asked to rank overall prefer-
ence for the mouthguards, 54.2% of
participants said they preferred CUS
while lifting, 25.0% preferred PB, and
16.7% chose UA. A similar preference for
custom mouthguards has been previously
reported.40 The remaining 4.2% of the
participants stated that they would not use
a mouthguard. While the PB was preferred
by one-quarter of the participants, it was
ranked as the mouthguard type that made
lifting the hardest (mean rank 3.1 out of
4.0). The overall fit of the mouthguard
was not reported as more uncomfortable
than that of other mouthguards, but
participants frequently reported that the
design features of PB were uncomfortable
or the mouthguard was difficult to bite.
Some participants using PB reported that
they could not clench properly during
the lift. PB consistently induced a greater
vertical opening of the mandible, sug-
gesting that vertical repositioning in the
range of 5 mm, measured at the incisors,
may cause athletes to perceive that they
are working harder during submaximum
power clean lift attempts.
Conclusion
During the power clean lift, maxillary
mouthguards can affect activation of head
and neck muscles, specifically the anterior
temporalis, masseter, and SCM muscles,
through a mechanism related to changes
in vertical dimension. These findings
demonstrate that muscle activation during
the power clean lift is related to length-
tension relationships within muscles of
mastication that may not affect other
areas, such as the cervical paraspinal mus-
cles. Participants, who indicated a nearly
2:1 preference for the custom mouthguard
over UA and PB mouthguards, perceived
that they were stronger and less encum-
bered when using a custom mouthguard
during power clean lifts.
Author information
Dr. Gage is chief resident, Postgraduate
Orthodontic Program, Arizona School
of Dentistry & Oral Health, A.T. Still
Sports Dentistry & Mouthguards Effects of mouthguards on vertical dimension, muscle activation, and athlete preference
54 November/December 2015 General Dentistry ww w.agd.org
University, Mesa, where Dr. Bliven is an
associate professor, Kinesiology Program,
College of Graduate Health Studies, and
Dr. Bay is a professor, Department of
Interdisciplinary Health Sciences, Arizona
School of Health Sciences. Dr. Sturgill
is in private practice in orthodontics,
Richmond, Virginia. Dr. Park is profes-
sor and chair, Postgraduate Orthodontic
Program, Arizona School of Dentistry &
Oral Health, A.T. Still University, Mesa.
Acknowledgments
Funding for this study was provided by
the Academy for Sports Dentistry. The
authors would like to thank Dan Brett of
Sportsguard Laboratories, Inc., for assis-
tance with custom mouthguard fabrication,
Trevor Nicholas for assistance with data
collection, and CrossFit Leiftime Fitness.
References
1. Stenger JM. Physiologic dentistry with Notre Dame
athletes.
Basal Facts.
1977;2(1):8-18.
2. Bates RE Jr, Atkinson WB. The effects of maxillary
MORA’s on strength and muscle efficiency tests.
J Craniomandib Pract.
1983;1 (4) :37-42.
3. Goldstein LB, McArdle WD, Last FC, et al. Temporo-
mandibular joint repositioning and exercise perfor-
mance: a double-blind study.
Cranio.
1985;3(4):
385-391.
4. Forgione AG, Mehta NR, Westcott WL. Strength and
bite, 1: an analytical review.
Cranio.
1991;9(4):305-
315.
5. Heit T, Derkson C, Bierkos J, Saqqur M. The effect of
the physiological rest position of the mandible on ce-
rebral blood flow and physical balance: an observa-
tional study.
Cranio.
2015;33(3)195-205.
6. Gelb H, Mehta NR, Forgione AG. The relationship be-
tween jaw posture and muscular strength in sports
dentistry: a reappraisal.
Cranio.
1996;14(4):320-325.
7. al-Abbasi H, Mehta NR, Forgione AG, Clark RE. The
effect of vertical dimension and mandibular position
on isometric strength of the cervical flexors.
Cranio
.
1999;17(2):85-92.
8. Forgione AG, Mehta NR, McQuade CF, Westcott WL.
Strength and bite, 2: testing isometric strength using a
MORA set to a functional criterion.
Cranio.
1992 ;
10(1):13-20.
9. Belvedere PC. “Performance-enhancing oral applianc-
es”: fact or fiction?
Dent Today.
2011;30(6):10, 12.
10. Aldana K, Miralles R, Fuentes A, et al. Anterior tem-
poralis and suprahyoid EMG activity during jaw
clenching and tooth grinding.
Cranio.
2011;29(4):
261-269.
11. Strini PJ, Strini PJ, Barbosa Tde S, Gaviao MB. Assess-
ment of thickness and function of masticatory and
cervical muscles in adults with and without temporo-
mandibular disorders.
Arch Oral Biol.
2013 ;5 8 (9) :
110 0 -11 08.
12. Ceneviz C, Mehta NR, Forgione A, et al. The immedi-
ate effect of changing mandibular position on the
EMG activity of the masseter, temporalis, sternoclei-
domastoid, and trapezius muscles.
Cranio.
2006;
24( 4) :237-244.
13. Zuniga C, Miralles R, Mena B, et al. Influence of varia-
tion in jaw posture on sternocleidomastoid and trape-
zius electromyographic activity.
Cranio.
1995;13(3):
157-162.
14. Ehrlich R, Garlick D, Ninio M. The effect of jaw clench-
ing on the electromyographic activities of 2 neck and
2 trunk muscles.
J Orofac Pain.
1999;13(2):115-120.
15. Alexander CF.
A Study on the Effectiveness of a Self-fit
Mandibular Repositioning Appliance on Increasing Hu-
man Strength and Endurance Capabilities
[master’s
thesis]. Knoxville: University of Tennessee; 1999.
16. Perinetti G, Turp JC, Primozic J, Di Lenarda R, Contardo
L. Associations between the masticatory system and
muscle activity of other body districts. A meta-analysis
of surface electromyography studies.
J Electromyogr
Kinesiol.
2011;21(6):877-884.
17. Chakfa AM, Mehta NR, Forgione AG, Al-Badawi EA,
Lobo SL, Zawawi KH. The effect of stepwise increases
in vertical dimension of occlusion on isometric
strength of cervical flexors and deltoid muscles in non-
symptomatic females.
Cranio.
2002;20(4):264-273.
18. Dunn-Lewis C, Luk HY, Comstock BA, et al. The effects
of a customized over-the-counter mouth guard on
neuromuscular force and power production in trained
men and women.
J Strength Cond Res.
2012;26(4):
1085-1093.
19. Kittelsen JD, Cross HD III, Belvedere PC, Herman M,
inventors; Bite Tech, Inc., assignee. Composite mouth-
guard. US patent 6,691,710. February 17, 2004.
20. Rafih Z, Makkar A, inventors; Rafih Z, Makkar A, as-
signees. Oral appliance for improving strength and
balance. US patent 9,022,903. May 5, 2015.
21. Rapisura KP, Coburn JW, Brown LE, Kersey RD. Physio-
logical variables and mouthguard use in women dur-
ing exercise.
J Strength Cond Res.
2010;24(5):
1263-1268.
22. Liew AK, Abdullah D, Wan Noorina WA, Khoo S. Fac-
tors associated with mouthguard use and discontinua-
tion among rugby players in Malaysia.
Dent Traumatol.
2014;30(6):461-467.
23. Gardiner DM, Ranalli DN. Attitudinal factors influ-
encing mouthguard utilization.
Dent Clin North Am.
2000;44(1):53-65.
24. Cetin C, Kececi AD, Erdogan A, Baydar ML. Influence
of custom-made mouth guards on strength, speed and
anaerobic performance of taekwondo athletes.
Dent
Traumatol.
2009;25(3):272-276.
25. Fakhruddin KS, Lawrence HP, Kenny DJ, Locker D. Use
of mouthguards among 12- to 14-year-old Ontario
schoolchildren.
J Can Dent Assoc.
2006;73(6):505.
26. Kececi AD, Cetin C, Eroglu E, Baydar ML. Do custom-
made mouth guards have negative effects on aerobic
performance capacity of athletes?
Dent Traumatol.
2005;21(5):276-280.
27. Arent SM, McKenna J, Golem DL. Effects of a neuro-
muscular dentistry-designed mouthguard on muscular
endurance and anaerobic power.
Comp Exerc Physiol.
2010;7(2):73-79.
28. Criswell E.
Cram’s Introduction to Surface Electromy-
ography.
2nd ed. Sudbury, MA: Jones and Bartlett Pub-
lishers; 2010.
29. Kendall FP, McCreary EK, Provance PG, Rodgers MM,
Romani WA.
Muscles: Testing and Function, With Pos-
ture and Pain.
5th ed. Baltimore: Lippincott Williams &
Wilkins; 2005.
30. Roettger M. Performance enhancement and oral appli-
ances.
Compend Contin Educ Dent.
2009;30(2):4-8.
31. Smith SD. Muscular strength correlated to jaw posture
and the temporomandibular joint.
N Y State Dent J.
1978;44(7):278-285.
32. Lindauer SJ, Gay T, Rendell J. Effect of jaw opening on
masticatory muscle EMG-force characteristics.
J Dent
Res.
1993;72(1):51-55.
33. Arima T, Takeuchi T, Honda K, et al. Effects of interoc-
clusal distance on bite force and masseter EMG in
healthy participants.
J Oral Rehabil.
2013;40(12):900-
908.
34. Hugger S, Schindler HJ, Kordass B, Hugger A. Clinical
relevance of surface EMG of the masticatory muscles,
1: resting activity, maximal and submaximal voluntary
contraction, symmetry of EMG activity.
Int J Comput
Dent.
2012;15(4):297-314.
35. Forrester SE, Allen SJ, Presswood RG, Toy AC, Pain MT.
Neuromuscular function in healthy occlusion.
J Oral
Rehabil.
2010;37(9):663-669.
36. Casares G, Thomas A, Carmona J, Acero J, Vila CN. In-
fluence of oral stabilization appliances in intra-articu-
lar pressure of the temporomandibular joint.
Cranio.
2014;32(3):219-223.
37. Learreta JA, Beas J, Bono AE, Durst A. Muscular activi-
ty disorders in relation to intentional occlusal interfer-
ences.
Cranio.
2007;25(3):193-199.
38. al-Quran FA, Lyons MF. The immediate effect of hard
and soft splints on the EMG activity of the masseter
and temporalis muscles.
J Oral Rehabil.
1999;26(7):
559-563.
39. Nanda A, Jain V, Srivastava A. An electromyographic
study to assess the minimal time duration for using
the splint to raise the vertical dimension in patients
with generalized attrition of teeth.
Indian J Dent Res.
2011;22(2):303-308.
40. Duddy FA, Weissman J, Lee RA Sr, Paranjpe A, Johnson
JD, Cohenca N. Influence of different types of mouth-
guards on strength and performance of collegiate ath-
letes: a controlled‐randomized trial.
Dent Traumatol.
2012;28(4):263-267.
Manufacturers
DENTSPLY International, York, PA
800.877.0020, www.dentsply.com
Dreve Dentamid GmbH, Unna, Germany
49.0.2303.8807.55, www.dreve.com
IBM Corporation, Armonk, NY
800.426.4298, www.ibm.com
NeuwGhent Technology, LaGrangeville, NY
845.223.3359
Noraxon U.S.A., Inc., Scottsdale, AZ
800.364.8985, www.noraxon.com
Power Balance Technologies, Inc., Carson, CA
888.487.7201, www.powerbalance.com
Under Armour, Inc., Baltimore, MD
888.727.6687, www.underarmour.com
www.agd.org General Dentistry Special sports dentistry section 55
