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The Relationship Between Jaw Posture and Muscular Strength in Sports Dentistry: A Reappraisal

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Abstract

From the late 1970s until the early 1990s, there have been several reports of improved appendage muscle strength and athletic performance. Much of the criticism of using a mouthguard alone or in conjunction with a splint, such as a mandibular orthopedic repositioning appliance (MORA), to enhance athletic performance has been aimed at study designs, controls, periods of time, double blindness, and the placebo effect. Although it would appear that designing a study which pleases both clinician and researcher would be a difficult task, studies have been performed that do meet the "gold standard." The results favor the premise that jaw repositioning can enhance appendage muscular strength and athletic performance. Studies performed during the mid-1980s, and to which the scientific community refers to continually, on closer examination are flawed.
320
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JOURNAL OF
CRANIOMANDIBULAR
PRACTICE,
Copyright © 1996
by CHROMA, Inc.
ABSTRACT: From the late 1970s until the early 1990s, there have been several reports of improved
appendage muscle strength and athletic performance. Much of the criticism of using a mouthguard
alone or in conjunction with a splint, such as a mandibular orthopedic repositioning appliance (MORA),
to enhance athletic performance has been aimed at study designs, controls, periods of time, double
blindness, and the placebo effect. Although it would appear that designing a study which pleases both
clinician and researcher would be a difficult task, studies have been performed that do meet the “gold
standard.” The results favor the premise that jaw repositioning can enhance appendage muscular
strength and athletic performance. Studies performed during the mid-1980s, and to which the
scientific community refers to continually, on closer examination are flawed.
Dr. Harold Gelb received his B.S. degree
from New York University in 1944 and his
D.M.D. degree from Tufts University
College of Dental Medicine in 1947.
Currently Dr. Gelb is an Adjunct Clinical
Professor in the Department of General
Dentistry at Tufts University College of
Dental Medicine. He is founder of the
Craniomandibular Pain Center at
Tufts University College of Dental
Medicine. Dr. Gelb is a Diplomate of the
American Board of Orofacial Pain.
Dr. Noshir R. Mehta is Chairman and
Professor of General Dentistry and
Director of the Gelb Craniomandibular
and Orofacial Pain Center at Tufts
University College of Dental Medicine.
He received his D.M.D. degree and his
M.S. degree in periodontics at Tufts,
where he has been working in occlusion
research. He is a Diplomate of the
American Board of Orofacial Pain, and
a national and international lecturer.
Dr. Mehta maintains a practice limited
to periodontics and temporomandibular
disorders.
S
everal dentists who had been treating patients with
temporomandibular disorders and orofacial pain
for years, reported increased strength and perfor-
mance in their patients as a result of changing their max-
illomandibular relationships.
l-3
In the 1970s, the work of John Stenger,
4
the dentist for
the Notre Dame football team, attracted attention. He
published several articles related to mouth protection in
which he correlated some of his statistical findings on
improved strength in both football and track and field. Dr.
Stenger and several of his colleagues, namely, Drs.
Lawton, Ricketts and Wright, had published a paper ear-
lier, in 1964, in the Journal of the American Dental
Association,
5
dealing with the use of mouthguards and
documenting their relationship with cervical stress release
and postural influences. Similar results were reported by
William Osmanski, a former professional football player,
who fitted mouthguards to a specified thickness for a
group of athletes.
3
The primary goal of proponents of mouthguards was to
provide universal protection of the teeth and jaws from
trauma. Although much has been said and published
on this subject over the past 40 years, the idea that
mouthguards, mouth “protectors,” or bite appliances
could also provide some increment of increased muscle
balance, strength, and/or coordination when it surfaced
18 years ago seemed to be an intriguing idea deserving
of further research.
An article
l
which appeared 18 years ago dealt with
oral orthopedic examination and the findings related to
muscle testing of players on the Philadelphia Eagles foot-
ball team. On clinical examination, the author found a
significant number of TMD-related symptoms and made
specific correlations in this and subsequent articles. At
The Relationship Between Jaw Posture and Muscular
Strength in Sports Dentistry: A Reappraisal
Harold Gelb, B.S., D.M.D. ; Noshir R. Mehta, B.D.S., D.M.D. ;
Albert G. Forgione, Ph.D.
PHYSIOLOGY
Manuscript received
February 26, 1996; revised
manuscript received
May 21, 1996; accepted
May 21, 1996.
Dr. Harold Gelb
635 Madison Avenue
New York, New York
10022
that time, a low percentage of players surveyed (22%)
had worn nightguards. Three years later more than 85%
of the players wore mouthguards. Since that time, much
has been published relative to the necessity of wearing
mouthguards.
Athletic Performance and Jaw Posture
One of the first articles to appear on this subject was by
Stephen Smith,
l
who performed a sample study on pro-
fessional football team players with an emphasis on the
temporomandibular joint and associated musculature.
Smith ascertained that there was a correlation between
the corrected jaw posture and the ability to give a stronger
contraction. This was measured first with both the teeth
together in habitual occlusion, and then with a wax bite
position, which was fabricated by bringing the player’s
lower jaw from physiologic rest position toward the
closest speaking space with midlines evenly aligned.
The measurements were made using a Cybex II
Dynamometer in conjunction with the kinesiologic del-
toid press method.
6, 7
The Cybex data was not as signifi-
cant as first believed.
Smith was the first person to investigate Stenger’s pro-
posed relationship. In Smith’s experiment, isometric
strength in three mandibular positions was tested subjec-
tively: 1. acquired centric occlusion; 2. the wax bite posi-
tion; and 3. the position produced by an unadjusted
football mouthguard. This study was criticized later
8
for
not including a statistical analysis of the data.
However, Forgione, et al. ,
8
calculated nonparametric
statistics on Smith’s published data and found significant
differences in isometric strength of the deltoid muscles
between the three conditions. Strength while biting on the
unadjusted mouthguard was significantly greater than
while biting in acquired centric occlusion. Strength biting
on the wax bite set at the functional criterion was signifi-
cantly greater than biting on the unadjusted mouthguard.
In a later study, Smith
9
recorded strength in response to
the Isometric Deltoid Press (IDP) objectively with an
electronic strain gauge. Again, Forgione, et al.,
8
calcu-
lated statistics of the published data and found isometric
strength biting at the mandibular position, determined by
the functional criterion, to be significantly greater than
biting in acquired centric occlusion or on an unadjusted
mouthguard.
In 1980, Kaufman fabricated and positioned several
splints for the United States Olympic luge and bobsled
teams. He discovered that headaches previously reported
by luge athletes during their runs, were alleviated to
varying degrees in some of the athletes by use of these
appliances. Some of these athletes also indicated an
increase in strength when pushing off at the start.
These original findings were then followed up by a
double-blind study
10
conducted to observe the effects of
the mandibular orthopedic repositioning appliance
(MORA) on football players on the 1982 C.W. Post
College football team. Forty players were randomly
divided into two groups, one wearing the MORA
11
and
the other wearing conventional mouthpieces (CM).
12
The
players were tested primarily to discover the effects of the
MORA on performance, number, type and severity of
injuries, as well as on three measures of physical fitness:
strength, jumping ability, and balance and agility.
The overall results were positive and in favor of the
MORA. Among players using the MORA there were less
severe injuries, decreased numbers of knee injuries, and
greater strength and satisfaction. No significant findings
favored the CM. These findings highlight the importance
of the MORA to football players.
Two other studies conducted at well-known teaching
institutions showed a positive correlation between changes
in jaw relationship and increases in strength and muscle
efficiency. One study
13
showed a highly significant
increase in muscle strength and efficiency (power) of a
group of athletes as recorded by vertical jump (five per-
cent increase) and a 17.3% increase in the grip test.
However, there was no significant increase in strength
recorded for the maximum hip sled or bench press test.
The other study tested 23 athletes, and compared
mandibular position with appendage muscle strength.
Three different mandibular positions were tested, along
with all four appendages. The results indicated that
mandibular position affects appendage muscle strength
and may be important to total well-being. However, con-
siderable variability of optimum muscle strength by
muscle groups and mandibular positions was noted.
14
Another double-blind study, performed at the University
of Illinois, involved 20 randomly selected volunteer
undergraduate students.
15
The subjects were given oral
examinations, and two appliances were then constructed
for them: a MORA, which repositioned the mandible
three dimensionally, as described by Gelb,
16
and a placebo
appliance that did not alter the occlusion.
The following bite conditions were then tested for
each individual: centric occlusion, centric occlusion with
the placebo splint inserted, and the position with
the MORA inserted. Data was collected using a Cybex II
Dynamometer with the subjects seated in a stabilized
chair. The information obtained was for three bite condi-
tions: a normal bite, a normal bite with the placebo splint
inserted and a normal bite with the MORA splint inserted.
Statistically significant differences were recorded between
the MORA and normal bite conditions for shoulder
GELB ET AL. JAW POSTURE AND MUSCULAR STRENGTH
OCTOBER 1996, VOL. 14, NO. 4 THE JOURNAL OF CRANIOMANDIBULAR PRACTICE 321
extension, peak torque; shoulder extension, average
torque; and external rotation, average torque. No statisti-
cal differences were observed between the placebo and
the normal bite condition.
Charges/Countercharges
Critics of the group favoring increased strength have
contended that their work lacked:
1. Adequate controls in the research design (such as
double-blind experimental designs).
2. Proper statistical analysis.
3. Knowledge of strength testing.
On the other hand, research indicating that the maxil-
lary and mandibular orthopedic repositioning appliance
(MORA) is ineffective for strength increases has been
criticized because:
1. It did not allow adequate time for the MORA to
work.
2. The MORA will only work on subjects with TM dis-
orders or occlusal problems.
3. It is not known whether or not the appliance has
placed the mandible in its optimal physiologic rela-
tionship.
11, 17
One other early study should be mentioned, because of
inferences made that need to be corrected.
11
In this study
14 basketball players, none of whom had any clinical or
historic evidence of TMD, myofascial pain dysfunction
syndrome (MPDS) or posterior bite collapse, were tested
in a randomly assigned order with an experimental open-
ing appliance, a placebo appliance that did not alter the
mandibular position or vertical dimension, and no appli-
ance. Results clearly demonstrated there was no change
in strength among the three groups.
Interestingly, of the 14 athletes, nine were Class I;
three were Class II, subdivision 1; and two were Class II,
subdivision 2. The results of the study reportedly indi-
cated that “opening the bite” of the normal subject will
not increase upper body strength.
If one assumes the study was done as stipulated, these
authors would also agree that “opening the bite,” or just
increasing the vertical dimension of a normal subject,
will not increase upper body strength, but this bears no
relevance to the three-dimensional maxillomandibular
relationship for each individual subject. This study, like
others previously mentioned, showed a total lack of
understanding of the model analysis as described by
Lieb,
l8
or as addressed by Verban.
l9
Scientific Flaws
Although many of the earlier studies were definitely
flawed from a scientific viewpoint, from a strictly clinical
standpoint, positive changes were noted. These changes
of increased strength and performance deserved further
investigation.
Two articles which appeared in March 1984 in the
Journal of the American Dental Association warrant
mention.
20, 2l
They describe two obviously flawed studies
carried out at two universities in the same state. These
studies were later refuted by credible scientific research.
Yet, the later scientific studies were rarely mentioned at
major meetings or in succeeding studies. Only the two
obviously flawed studies were mentioned when the sub-
ject matter on which these articles were based was dis-
cussed. Is there a “double (gold) standard,” because it
serves a special group’s purpose? This double “gold”
standard denies the use of information of the utmost value
to all practitioners regardless of their specialties.
The two flawed studies reported in JADA showed little
comprehension of the procedures for fabricating appli-
ances for TMD and athletically involved patients that
have been advocated for years. Each of these studies used
treatment splints that were fabricated using the design
recommended by Gelb, but not the three-dimensional
model analysis as prescribed by Lieb,
18
which calls for
subsequent mounting on a Galetti Articulator to achieve
the corrected maxillomandibular relationship for each
subject.
In one study,
2l
the vertical dimension between the
incisors was increased by a constant 2 to 3 mm for all
subjects. None of the subjects gained or lost muscle
strength through the use of the mandibular orthopedic
repositioning appliance.
In the other study,
20
the occlusal portion of the splint
occupied the subject’s freeway space and was adjusted to
provide even contact in centric occlusion. Forty-two per-
cent of the subjects (20) had clicking in the TMJ, but
none of the subjects had palpation tenderness of the mas-
ticatory muscles or the TMJ. All subjects underwent a
chiropractic-applied kinesiologic evaluation to test iso-
metric muscle strength. This examination showed nine
subjects would benefit trom wearing a MORA. Five sub-
jects received treatment splints, and four wore placebo
splints.
This procedure is certainly questionable, since the bite
positionings were not adjusted by kinesiologic guidance
or by the chiropractor’s suggestion.
Verban
l9
summed up much of what was wrong with
these two studies in a letter to the editor published in the
July 1984 JADA. He said, “It is not the MORA, but rather
the position obtained with the MORA that is important.
This position is not universal and must be determined for
each individual. Under this hypothesis, a study in which
JAW POSTURE AND MUSCULAR STRENGTH GELB ET AL.
322 THE JOURNAL OF CRANIOMANDIBULAR PRACTICE OCTOBER 1996, VOL. 14, NO. 4
each MORA is constructed exactly the same could not
prove a benefit of statistical significance.”
Yates in the June 1984 JADA, responding to another
letter to the editor, shows his lack of understanding by
saying, “I should like to remind him that our testing pro-
cedures come from the claims of MORA supporters,
22
who show pictures in their publications indicating that
strength is increased simply by inserting the MORA.”
This could not be further from scientific reality and
indicates a lack of understanding of the actual procedures
performed.
Gaining New Perspectives
Forgione, Mehta, Westcott and McQuade
8, 23
surveyed
20 experimental and clinical studies and two review
commentaries. Their study attempted to organize what
has been reported to date; identify the inappropriate use
of terms; point out questionable statistical practices;
question the conclusions of faulty experimental designs;
and scrutinize the unfounded generalizations that have
resulted. They state that if Stenger’s original concept is
proved to be correct, it will have implications, not only
for athletic performance, but for the more central role of
occlusion in health and behavior.
In their review they found that a commentator,
24
a
reviewer,
25
and the authors of three of the studies
11, 20, 2l
made emphatic general statements critical of the original
results and several studies that followed supported
Stenger’s original proposed relationship in spite of sev-
eral factors, which they enumerated as follows:
1. Most of these experiments used subjects with no
apparent malocclusion or lack of posterior support,
and other subjects who had mixed occlusions.
2. Most researchers set bite appliances by techniques
other than kinesiological guidance, a functional tech-
nique, assuming or implying that all MORAs are
equivalent.
3. Researchers used data showing no increase in isoki-
netic tests of strength to criticize studies of isometric
strength while commenting upon “strength” unquali-
fiedly.
4. Some researchers employed either questionable sta-
tistics, experimental design or both.
5. Some authors and a commentator have invoked
placebo as a criticism of evidence that supported
Stenger’s proposal even though the placebo effect
has not been demonstrated in any of the studies that
employed a placebo control condition. The belief
that the placebo effect is omnipresent has even fos-
tered an explanation for its lack of appearance.
In addition, they mention the possible role of body test
position, and its consequent influence on the bite as it
affects results.
Their manuscript dealt not only with a review of the
current literature on variation in strength of extraoral
muscles as a function of bite relationship, but also
includes a reversal design study using a K-MORA (kine-
siologically determined using the isometric strength of
the deltoid muscle), a deflection appliance, and a placebo
appliance.
8, 23
In this study of the effect on isometric strength of
biting on three different intraoral devices and habitual
occlusion, it was concluded that a relationship does exist
between bite and isometric strength. They also found that
the previous speculation concerning the role of the
placebo effect was not substantiated by the data gathered
in their experiment.
The Female Experience
A methodologically refined replication of Smith’s
experiment was performed by Fuchs
26
in 1981. This
unpublished dissertation compared isometric strength of
40 females divided equally into five groups; TMJ patients,
athletic TMJ-symptomatic subjects, sedentary TMJ-
symptomatic patients, normal athletic subjects, and
normal sedentary subjects. Identical with Smith’s experi-
ments, a wax bite was fabricated for each subject guided
by the IDP. But unlike Smith’s research design, a disoc-
cluded and a placebo condition were both included. The
strength of six body parts (left and right arm, left and
right foot, upper and lower body) were measured under
four bite conditions: 1. mouth open 3 mm; 2. bite in
acquired centric; 3. K-MORA, an intra-oral device that
supports a mandibular position determined by a func-
tional criterion, which is a locking response to the IDP, a
muscle challenge used by kinesiologists; and 4. bite with
a placebo wax buccal device. An electronic strain gauge
identical with that employed by Smith
9
recorded responses
in kilogram/second with the analog output simultane-
ously recorded on the stripchart of a Beckman Dynograph.
Mean strength scores for the whole sample were found to
be markedly different. Tukey’s multiple comparison
technique showed no significant differences among
mouth open, acquired centric, and placebo conditions.
Greater strength was obtained with the K-MORA than in
all the other conditions. For the lower body, a significant
difference in strength was obtained between the
K-MORA and the mouth open. Similarly, the K-MORA
strength was greater than the placebo in the upper body
and left foot even though the K-MORA performance was
stronger than habitual occlusion in only the right arm and
left foot. Fuchs then concluded that with no exception,
GELB ET AL. JAW POSTURE AND MUSCULAR STRENGTH
OCTOBER 1996, VOL. 14, NO. 4 THE JOURNAL OF CRANIOMANDIBULAR PRACTICE 323
the strength means were greater and the standard devia-
tions lower in the K-MORA position than in any other
position. Fuchs replication of Smith’s research helps
answer the unchallenged placebo criticisms in the litera-
ture that tend to obviate Stenger’s and Smith’s seminal
findings prematurely.
A double-blind study (Abduhl Jabbar, et al., 1994)
27
was designed to test the bilateral isometric strength of the
extremities and shoulder girdle of female TMD patients.
The patients all demonstrated obvious loss of vertical
dimension of occlusion by a deep overbite occlusion,
missing posterior supporting teeth or obvious tooth wear
due to bruxism or repeated occlusal adjustments. The
strength testing was carried out at the Neuromuscular
Disease Research Laboratory of the Department of
Neurology at the Tufts New England Medical Center, an
independent medical facility, using the apparatus and
procedures
28, 29
routinely used to assess the isometric
strength of patients with neuromuscular disease.
A standard neuromuscular test with the Maximal
Voluntary Isometric Contraction apparatus was used to
assess strength of right and left shoulder, elbow and knee
flexion and extension, as is routinely performed with all
neuromuscular disease patients. Twelve strength tests
were carried out for each of three conditions: 1. Baseline,
biting in habitual occlusion; 2. Elevated, biting on a
K-MORA; 3. Placebo, biting with the placebo appliance
inserted. The order of conditions 2 and 3 was counterbal-
anced without knowledge of the subjects.
Twelve repeated measures ANOVAs (each subject as
their own control) were conducted for each of the 12
strength measures. All F-tests indicated a significant
main effect for treatment differences (p<0.0001). Mean
strength biting on the K-MORA was consistently greater
(p<0.001) than baseline or placebo strength. Baseline and
placebo conditions were equivalent.
These findings confirm observations that individuals
with loss of vertical dimension of occlusion respond to a
bite-raising appliance by increased isometric strength.
Isometric strength of the sternocleidomastoid muscles
(SCM) was assessed in 15 subjects demonstrating deep
bite and loss of vertical dimension by al-Abasi, et al.
30
In
the preliminary part of the experiment all subjects were
tested sitting, with the head unsupported and the teeth 1.
disoccluded and 2. biting in habitual occlusion. Strength
with the teeth disoccluded was significantly greater than
biting in habitual occlusion. Four types of acrylic lower
appliances were then fabricated:
1. Habitual bite, elevated to the functional criterion of
the IDP. (This vertical dimension was transferred
to an articulator and three other appliances were
fabricated at the same vertical dimension. )
2. Edge-to-edge.
3. Retruded.
4. Lateral shift of l mm to the left.
Each subject was tested twice, biting with and without
appliance in habitual occlusion, edge-to-edge, retruded
and lateral shift positions. Analysis of variance showed a
significant difference between groups. The mean stern-
ocleidomastoid muscle (SCM) strength of 27.17 lbs.
obtained when biting in all the elevated vertical positions
was greater than 21.73 lbs. obtained biting without a bite
elevating appliance.
More detailed analysis showed:
1. Without an appliance, SCM strength, biting in habit-
ual occlusion, was lower than in the edge-to-edge
position but not in the retruded and lateral shift posi-
tions; and
2. With appliances, SCM strength of the same subjects
was greater in habitual and edge-to-edge positions
than in retruded but not lateral shift positions.
The findings indicated that, while biting at an elevated
position determined by the IDP, SCM isometric strength
can increase regardless of position. However, an elevated
edge-to-edge position and an elevated habitual position
maximized SCM isometric strength.
Far Eastern Contributions
Researchers in Korea and Japan have taken an interest
recently in this relationship between vertical dimension
of occlusion and muscle strength. The effect of a bite-ele-
vating appliance on back muscle strength of 22 male foot-
ball players and 22 female archers was tested by Kang
and Lee.
31
Both groups of athletes and a control group
were tested using a digital back muscle dynamometer
before and after 30 days of appliance wear. Back muscle
strength increased with the bite-elevating appliance
(15.2% in males and 12.4% in females), but the control
group’s mean strength did not change.
Tsukimura
32
tested back strength of eight subjects at
different vertical dimensions. In the disoccluded mandibu-
lar position, back strength was the weakest, but tended
not to increase as a 2, 5 and 10 mm splint was worn and
decreased when a 15 mm appliance was worn. Maximum
strength was obtained in the 2-10 mm range of splinting.
Yokobori and Horii
33
performed the critical experi-
ment supporting the contention of Forgione, et al.,
8
that
isokinetic and isometric strength may not be related.
Forty college athletes were fitted with bite-elevating
appliances and tested on both isometric and isokinetic
tasks, with and without the appliance. With the appliance,
significant increases in isometric strength were obtained
in back extension, leg extension, and plantar extension,
JAW POSTURE AND MUSCULAR STRENGTH GELB ET AL.
324 THE JOURNAL OF CRANIOMANDIBULAR PRACTICE OCTOBER 1996, VOL. 14, NO. 4
GELB ET AL. JAW POSTURE AND MUSCULAR STRENGTH
OCTOBER 1996, VOL. 14, NO. 4 THE JOURNAL OF CRANIOMANDIBULAR PRACTICE 325
but not in arm flexion and grip strength. Isokinetic
strength of knee extension and flexion showed no differ-
ence when tested on a Cybex at angular velocities of 60,
120 and 240 deg/s. Interestingly, these authors also found
that equilibrium was improved in these subjects while
wearing the appliances.
A study presented last year
34
suggested that wearing
appropriate complete dentures is essential to not only
the restoration of masticatory function, but also the main-
tenance of the ability of physical exercise. A previous
study done by the same investigators suggested that the
occlusal support played an important role for the normal
dentate subjects who exhibited teeth clenching during
physical exercise. Since the occlusal support is obtained
by wearing complete dentures in edentulous patients,
physical exercise should be affected whether wearing
dentures or not.
Summary
The clash that exists between the clinician and some
scientists is becoming ever more visible as the differ-
ences between applied and basic biological research
narrow, and the time lag between a fundamental discov-
ery and clinical application shrinks. In a number of cases,
the opposite can be true. It is no surprise that
clinical application of value to the patient may outstrip
scientific verification because of differences in training
and individual interests. Scientists spend five to ten years
of postgraduate training learning how to conduct proper
research, whereas physicians devote the bulk of their
training to patient care. This also holds true for dentists.
35
The time has finally come for dental clinicians
and scientific researchers to develop greater mutual
respect, thereby providing better and more cost-effective
care to our patients sooner and with less suffering.
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Dr. Albert G. Forgione is Chief Clinical Consultant of the Gelb
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Together with Dr. Mehta, he started the TMJ Center at Tufts in 1979.
... The usefulness of mouthguards and oral splints to enhance performance in sports is currently debated (Garner, 2018;Gelb et al., 1996). Altering the vertical dimension of occlusion (VDO) and the relationship of the mandible to the maxilla appears to have an effect on the entire neuromuscular system controlling posture, and consequently, motor performance (Abdallah et al., 2004). ...
... Until now most studies concentrated on the effects of wearing dental appliances during the performance. One of the few studies examining the long-term effects of wearing an occlusal device is discussed by Gelb et al. (1996): back muscle strength increased by 10% and more after 30 days of bite-elevating appliance wear respect to a control group. What is not clear is whether the subjects were tested with or without the device on. ...
... Finally, it is worth mentioning the placebo effect invoked by some researchers to explain the strength gain wearing mouthguards during exercise. In their review, Gelb et al. (1996) reject the placebo as a plausible mechanism based on the consideration that even such an effect has to be demonstrated. What is largely undisputed however is that bite raising, until a certain VDO is reached, had no detrimental effect on athletic strength and performance provided the intervention is not uncomfortable or causing breathing difficulties (Forgione et al., 1991). ...
Article
The use of oral appliances is considered effective in improving sport performance. Jaw clenching or stretching,improved breathing or positioning of the jaw have been proposed to explain the improvement. In this study, we reported the effects of regularly practiced mandibular stretching at submaximal opening of the jaw in Crossfit athletes. Seventeen test subjects undergoing mandibular stretching (MS) showed significantly reduced (p < 0.001) performance time in a high-intensity workout measured before and after seven days of 10-minutes stretching practiced twice daily, while no improvement was observed in control subjects who did not perform the stretching. Additionally, blood lactate levels appeared to recover more quickly in MS subjects. Crossfit is a type of training regimen that pushes the limits of bodily recovery processes. Jaw stretching, eliciting the trigeminocardiac reflex (a reflex decrease in heart rate and blood pressure following trigeminal stimulation) and central oxygen-conserving mechanisms could help relieve post-training stress and improve training recovery.
... Thus, different interventions have been performed in order to analyze, and better understand the impact of postural chain connection alterations, on human performance [8,9]. Among them, the role of the dento-mandibular apparatus and, in particular, occlusion and jaw position, received increased attention, and became the object of several investigations published in recent years [5,9,10]. Indeed, studies have even reported that acute interventions in occlusion condition may induce positive effects in posture, postural control, balance, walking and running biomechanics, endurance, and strength performance [11][12][13][14][15][16][17]. ...
... In addition, indirect evidence suggested an additional hypothesis, by which the TMS and the skeletal muscles are connected with the fascia system through muscle and fascia chains, respectively, and how this may explain the neuronal connection of TMS and body posture [26]. Although several hypotheses and observations exist, the results of the few literature reviews that explored the possible associations between occlusion, jaw position, and athletes' performance, brought out the complexity of this topic, underlying the presence of controversial results, and difficulties in testing procedures standardization [9,10,27]. However, in recent years the sciences applied to sport performance analysis as well as the knowledge associated with the dento-mandibular apparatus have progressed consistently, and this is demonstrated by the number of works covering this field, published in recent years. ...
Article
Full-text available
The role of the dento-mandibular apparatus and, in particular, occlusion and jaw position, received increased attention during last years. In the present study, we aimed to systematically review, on the light of the new potential insights, the published literature covering the occlusal splint (OS) applications, and its impact on exercise performance. A structured search was carried out including MEDLINE®/PubMed and Scopus databases with additional integration from external sources, between March and June 2021. To meet the inclusion criteria, studies published in the English language, involving humans in vivo, published from 2000 to 2021 and that investigated the role of occlusal splints on athletes’ performance were selected. Starting from the 587 identified records, 17 items were finally included for the review. Four main aspects were considered and analyzed: (1) occlusal splint characteristics and occlusion experimental conditions, (2) jump performance, (3) maximal and explosive strength, and (4) exercise technique and biomechanics. The results of the systematic literature analysis depicted a wide heterogenicity in the experimental conditions and suggested the application of the OS as a way to improve athletes’ or individuals’ oral health, and as a potential tool to optimize marginal aspects of exercise performance
... Therefore, the psychophysical conditions of athletes and their posture are important. Good posture results in reduced muscle work, less strain on ligaments, greater resistance to fatigue, and better management of movements [14][15][16]. Intense muscle exertions protracted over time, however, push the athlete to the limit, resulting in a framework of muscle fatigue that makes the balancing and coordination system less efficient, as well as a hydrosaline-hormonal imbalance, with a massive release of catecholamines and cortisol [3,17]. In addition, at the occlusal level, especially in endurance sports, or in those involving the use of maximum potential force, there is abnormal clenching of the dental arches (over-occlusion), resulting in excessive compression of the TMJ, which occurs as a physiological epiphenomenon during physical exertion. ...
Article
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Citation: Inchingolo, A.D.; Pezzolla, C.; Patano, A.; Ceci, S.; Ciocia, A.M.; Marinelli, G.; Malcangi, G.; Montenegro, V.; Cardarelli, F.; Piras, F.; et al. Experimental Analysis of the Use of Cranial Electromyography in Athletes and Clinical Implications.
... While mouthguards are widely used within athletic population, the findings from previous research investigating the effects of mouthguards in performance remains controversial [ 19 , 20 ]. Several methodological issues have been pointed to previous research, such as questionable statistics and/or experimental designs [21] . Additionally, some studies have a low level of methodological quality, due to high potential of bias, lack of proper randomization procedures, allocation concealment of operators or even blinding of subjects regarding which group are they assigned (experimental or placebo) [22] . ...
Article
Background It is widely accepted that mouthguards are effective for injury protection in sports. However, findings on the effects of mouthguards in strength and power production remains controversial. Therefore, the aim of this study was to determine whether controlled-mandible position mouthguards influence strength and power production in well trained athletes. Methods Twenty-two male amateur rugby players (25 ± 3.84 yrs; 1.92 ± 0.07 m; 93.91 ± 11.99 kg) volunteered for this study. Every participant performed an 1RM bench press test (113.20 ± 16.83 kg) to determine his maximal strength. In a randomized order, a ballistic bench press using 40% of the obtained 1RM (44.93 ± 6.76 Kg) was performed in a guided bar attached to a linear position transducer (LPT) for the following conditions: a) no mouthguard (CON); b) controlled mouthguard (MCM - jaw in centric relation); c) non-controlled mouthguard (NCM) and d) occlusal splint (OS). Vertical dimension of occlusion was also assessed for each of the testing conditions. Results Athletes using a controlled mouthguard demonstrate a significant (p< 0.05) higher peak acceleration and peak force than those using no mouthguard. Additionally, when analysing the results of vertical dimension of occlusion, a significant difference (p< 0.05) was observed between controlled mouthguard and the other tested conditions. Conclusion Controlled mouthguards enhance peak force and peak acceleration in the ballistic bench press exercise without negatively affecting any other measure assessed in this study. We speculate that this is possibly due to an increased stability of temporomandibular joint.
... 2021 sistema estomatognático [24][25][26]. Após a década de 80 [27,28] em seus trabalhos, acredita-se na relação de equilíbrio mandibular e na melhora da força muscular em indivíduos com a dentição completa. Atualmente, a má oclusão dentária pode levar a várias alterações iniciando com as dores e potencialização por sensações que afetarão a qualidade dos treinamentos [29][30][31][32]. ...
Article
Full-text available
Introduction: Maintaining oral health by preventing and motivating healthy habits (tooth brushing and flossing) is effective in preventing diseases in the oral cavity. It is speculated that oral health improves performance in athletes and reduces injuries. Objectives: Diagnose the oral health conditions of athletes; Treat oral lesions; Develop educational and motivational actions in the promotion and prevention of oral health. Methods: 14 athletes of both genders from the athletics modality were studied. They answered a questionnaire with objective questions about their knowledge of the interferences of oral changes in sports performance. Oral health indicators were also evaluated, such as Control Plaque Index (CPI), Bleeding Index (BI), and Simplified Oral Hygiene Index (SOHI) at the beginning of the study. Then, dental treatments were performed according to the individual needs of each athlete, accompanied by lectures on prevention and motivation of healthy oral health habits. After six months, mouth indicators were reassessed. In all phases of the experiment, there was supervision by dental surgeons. Results: The collected data allow us to point out the significant reduction in oral health indexes. Athletes have no prior knowledge of the influence of oral health and sports. Another important point addressed in the study was the misuse of dental floss. Conclusion: We can make the following notes: 1) This is the first study using the athletics modality and involving both genders; 2) It was also observed that, all athletes had little knowledge about oral health and its relationship with performance; 3) The oral health indicators were reduced after oral health education actions through lectures on the prevention and motivation of healthy habits such as better brushing and the correct use of dental floss.
... Raquel et al., 2017 afirmou que o uso do PBI evita que os músculos mastigatórios sejam submetidos a estresse repetitivo que podem desequilibrar a musculatura orofacial, prejudicando assim o atleta. Dessa forma, o aumento da DVO parece afetar a ativação muscular e desempenho no resto do corpo (Gelb et al., 1996;Raquel et al., 2017). ...
Article
Full-text available
Os protetores bucais são dispositivos intraorais que visam prevenir traumatismos dentários e maxilofaciais decorrentes da prática esportiva. Por ser um dispositivo interoclusal, é necessário entender e saber se este pode interferir no equilíbrio corporal do atleta, tendo em vista que a existência da relação entre o sistema temporomandibular e o controle postural já foi comprovada analisando diferentes oclusões dentarias e posições mandibulares. O objetivo deste estudo foi avaliar a influência do protetor bucal individualizado (PBI) no equilíbrio e postura corporal como também extrair seu relato da percepção do uso quanto a possíveis alterações no equilíbrio, postura corporal podendo interferir no desempenho esportivo. Este estudo é um ensaio clínico não randomizado que incluiu 65 atletas atendidos por demanda espontânea no ambulatório de Odontologia do Esporte da Faculdade de Odontologia da Universidade de São Paulo (FOUSP). A utilização do PBI teve influência significante na variável distancia glabela mento (p=0,005). Em relação ao relato da percepção de uso, 75,68% relataram alterações no equilíbrio e 70,28% na postura corporal, 70,28% relataram melhora de desempenho e 67,56% melhora no gesto esportivo. Conclui-se que utilização do PBI causa mais confiança nos atletas na execução dos exercícios e consequentemente, no desempenho esportivo.
... A recent literature evaluation taking into consideration the connection between occlusion, TMJ, and sport performance presented a few articles on this topic, but that had a limited reliability, as they were not randomized clinical trials or meta-analyses [8,9]. Some of the latest research has found muscular and postural modifications by means of kinesiology analysis, but it did not take into consideration reliable tests such as the Messerman or stomatognathic reset tests [10]. ...
Article
Full-text available
Clinical practice and some scientific evidence seem to suggest that there is some kind of relationship between the components that form the postural chain. For professional dancers, good posture and balance are essential. The aim of the present retrospective study is to evaluate whether gnathological treatment could have an impact on the postural balance and sports performance of professional ballet dancers. Electromyographic (EMG) data and balance tests were recorded before and after six months of treatment with a customized occlusal splint. Twenty athletes were examined during ballet exercises in terms of balance and speed of execution by two experienced clinicians. The results showed statistically significant changes for all EMG tests carried out and the Flamingo Balance Test. It appears that the use of a customized occlusal device improved neuro-muscular coordination and the overall performance of dancers.
... The occlusion and mandibular positions affect both full-body functioning and sports performance (Watanabe et al., 1998;Fujii, 2016;Fujii, 2017;Fujii, 2019;Fujii, 2020;Miyaji, 2020;Mehta, & Forgione, 1996). In this report, I describe the effectiveness of dental treatment in a runner with intermittent low back and hip pain. ...
... In the same way, Mannheimer and Rosenthal [15] reported that the position of the cervical spine changes temporomandibular joint (TMJ) disorder and changes the direction of the head and consequently changes the position of the mandible. Therefore, the position of the appropriate mandibular joint can improve the exercise ability when the movement occurs, and the muscle strength can be changed according to the position of the jaw [16]. Recently, there have been reports of improvements in performance by changing the position of the jaw joints after wearing a mouthguard [17][18][19]. ...
Article
Full-text available
The present study examined the influence of a customized mouthguard on body alignment and balance performance in professional basketball players. Twenty-three professional male basketball players, aged 25.8 ± 8.6 years old, were voluntarily assigned to participate in three treatments, including no treatment (no mouthguard), acute treatment (wearing a mouthguard), and repeated treatments (8 weeks follow-up). Body alignment status, such as spinal and pelvic posture and balance performance, were measured at each time point using a 3D Formetric III (Germany) and a postural control device (Posturomed 202, Germany), respectively. A repeated MANOVA analysis with a Bonferroni post hoc test was applied, and the adjusted p-value was set at 0.02. No significant treatment effect was observed in body alignment (p = 0.302). However, univariate analysis showed a significant difference in pelvic torsion, where it was decreased after acute and repeated mouthguard treatments compared to no treatment (p < 0.001). Kyphotic angle also increased significantly following 8 weeks of treatment compared to no treatment (p < 0.001) and acute treatment (p < 0.002). There was a significant treatment effect on balance performance (p < 0.001). Both static and dynamic balance performance improved following 8 weeks of treatment (p < 0.001). Our study revealed that a customized mouthguard provides a benefit to balance performance. Notably, repeated treatment impacts on balance performance more than acute treatment. Although our findings did not show a significant effect on body alignment, some positive results, such as pelvic torsion and kyphotic angle, may provide substantial information for developing future longitudinal studies with large sample sizes.
Article
A study was done to examine the effects of wearing splints, for treatment of temporomandibular joint dysfunctions, on muscle strength and equilibrium in athletes.Forty collegiate athletes participated. All the subjects were interviewed and examined by dental investigators. Splints were constructed on the basis of vertical dimensions deemed appropriate by the subjects' dentists. Three areas were then studied : First, isometric muscle strength of grip, arm flexion, back extension, leg extension, and plantar flexion were measured with and without splints. Second, isokinetic muscle strength of knee extension and flexion were measured at angular velocities of 60 deg/s, 120 deg/s, and 240 deg/s, with and without splints. Third, a stepping test with closed eyes was used to determine equilibrium by measuring transfer distance, transfer angle and rotation angle with and without splints.The results are summarized as follows :1) Isometric muscle strength of back extension, leg extension, and plantar flexion were significantly increased when wearing splints (p<0.05) . Arm flexion strength and grip strength showed no significant alteration.2) Isokinetic muscle strength showed no significant difference at any angular velocity.3) In the stepping test with closed eyes, transfer distance showed a significant decrease when splints were worn (p<0.01) . Transfer angle and rotation angle showed no significant alteration.From the present results, it is suggested that wearing of splints is an effective aid for improving the muscle strength and equilibrium of athletes.
Article
More athletes are using mandibular orthopedic repositioning appliances (MORAs), and many have claimed they cause surprising performance improvements. However, most research on this subject has suffered from serious design problems. In this double-blind experiment, control, experimental, and placebo groups of college students were tested for left and right maximal grip strength and endurance, maximal quadriceps and hamstring dynamic strength, and maximal quadriceps and hamstring static strength. Statistical analysis of the results showed that the devices did not increase the strength of the muscle groups measured or the muscular endurance of the hand.
Article
The present study was carried out to compare back strengths and electoromyogram of all related muscles among 8 healthy subjects as well as among different maxillomandibular relation for the purpose of investigating influences of postural changes in vertical maxillomandibular relation on the back strengths. The results obtained are described below:1. Back Strength1) In the opening position, back strengths were small in all subjects.2) In the intercuspal position, back strengths tennded to increase when a splint was worn.3) In other maxillomandibular relations, back strengths tended to increase when a 2-, 5- or 10-mm splint was worn, but tended to decrease when a 15-mm splint was worn.4) Many of the subjects showed the maximum strengths when they wore a 2- to 10-mm splint.2. Muscular Activity1) In comparison with the activity of the masseter muscle measured in the opening position and the intercuspal position, its activities tended to markedly increase in other maxillomandibular relations. In comparison with those measured in other maxillomandibular relation, its activities tended to increase when a 2-, 5- or 10-mm split was worn.2) Although the activity of the sternomastoid muscle measured in the opening position tended to decrease in all subjects in comparison with those measured in other maxillomandibular relations, no certain tendencies were observed on comparison of its activity measured in the intercuspal position.3) There were no certain tendencies in activities of the trapezius muscle in all maxillomandibular relations.4) There were no certain tendencies in activities of muscles of the upper and lower extremitis, including the gastrocnemius muscle.
Article
Typescript (photocopy). Thesis (Ed. D.)--Boston University, 1981. Vita. Includes bibliographical references (leaves 117-121).