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Relationship Between the Number of Occlusal Contacts and Masticatory Muscle Activity in Healthy Young Adults

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The electromyographic (EMG) potentials of left and right masseter and temporalis anterior muscles were recorded in 23 healthy young adults during: 1. a 3-second maximum voluntary clench (MVC) on cotton rolls positioned on the posterior teeth (standardized recording); and 2. a 3-second MVC in intercuspal position. EMG potentials recorded in intercuspal position were standardized as a percentage of the mean potentials of the standardized recording, and the EMG muscle activity was calculated. The number of occlusal contacts in intercuspal position was assessed by using eight microm thick shim stocks. Two groups of subjects with either 1. Less than ten occlusal contacts (11 subjects with "few contacts"); or 2. At least ten occlusal contacts (12 subjects with "many contacts") were selected. The MVC muscle activity in the "few contacts" group was significantly lower than that recorded in the "many contacts" group (p<0.005). In conclusion, the number of occlusal contacts and masticatory muscular function are significantly related, at least in young adults with a sound stomatognathic apparatus.
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JOURNAL OF
CRANIOMANDIBULAR
PRACTICE,
Copyright © 2002
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ABSTRACT: The electromyographic (EMG) potentials of left and right masseter and temporalis anterior
muscles were recorded in 23 healthy young adults during: 1. a 3-second maximum voluntary clench
(MVC) on cotton rolls positioned on the posterior teeth (standardized recording); and 2. a 3-second MVC
in intercuspal position. EMG potentials recorded in intercuspal position were standardized as a percent-
age of the mean potentials of the standardized recording, and the EMG muscle activity was calculated.
The number of occlusal contacts in intercuspal position was assessed by using eight µm thick shim
stocks. Two groups of subjects with either 1. Less than ten occlusal contacts (11 subjects with “few con-
tacts”); or 2. At least ten occlusal contacts (12 subjects with “many contacts”) were selected. The MVC
muscle activity in the “few contacts” group was significantly lower than that recorded in the “many con-
tacts” group (p<0.005). In conclusion, the number of occlusal contacts and masticatory muscular func-
tion are significantly related, at least in young adults with a sound stomatognathic apparatus.
Dr. Virgilio F. Ferrario received his
Ph.D. degree in bioengineering from the
Polictecnico of Milan, Italy in 1969. He
received his M.D. degree from the
University of Milan School of Medicine, in
Italy in 1980. He is a Professor of Human
Anatomy at the Dental School of Milan
University, and Director of the
Laboratory of Functional Anatomy of the
Stomatognathic Apparatus, Department of
Human Anatomy, Faculty of Medicine,
University of Milan, Italy. Dr. Ferrario
has been involved in research on the
anatomical bases of stomatognathic
function and malfunction and is currently
developing functional tests to analyze the
activity of masticatory muscles.
M
ost functional activities of the stomatognathic
apparatus require stable tooth contact between
the maxillary and mandibular dental arches.
This position, namely, the maximum intercuspation,
should be the position of maximum stability for the
mandible.
l-2
Both static (i.e., biting) and dynamic (i.e.,
chewing) activities seem to be more efficient when a suf-
ficient number of dental contacts provide a stable refer-
ence for the contraction of supramandibular masticatory
muscles.
3-4
The literature reports several methods for the detection
and measurement of occlusal contacts from the simpler
assessments made by using articulating paper or occlusal
wax/silicone to the more complex instrumental methods
(occlusal sonography, computerized occlusal contact sen-
sors, pressure sensitive films, photocclusion).
5-11
An
actual contact between opposing teeth can also be mea-
sured with very thin shim stock strips.
2-3,12
This last
method is among the most precise, reliable, and repro-
ducible methods reported in clinical and basic dental lit-
erature.
12-13
Significant correlations between the electromyo-
graphic (EMG) characteristics of masticatory muscles
(amplitude of the electric potentials, duration of contrac-
tile activity) and the number of dental contacts have
Relationship Between the Number of Occlusal Contacts and
Masticatory Muscle Activity in Healthy Young Adults
Virgilio F. Ferrario, M.D., Ph.D.; Graziano Serrao, M.D., Ph.D.;
Claudia Dellavia, D.D.S.; Elisabetta Caruso; Chiarella Sforza, M.D., Ph.D.
OCCLUSION
Manuscript received
July 9, 2001; revised
manuscript received
November 21, 2001;
accepted
December 1, 2001
Address for reprint
requests:
Dr. Virgilio F. Ferrario
Department of Human
Anatomy
Via Mangiagalli 31
I-20133 Milano,
Italy
e-mail: farc@unimi.it
already been found.
3,4,10
In particular, Hidaka, et al.
10
found that the increment in the area of dental contact was
proportional to the increment in masticatory muscle
force with a relatively constant average bite pressure.
Unfortunately, both investigations had some limitations:
Bakke, et al.
3
analyzed women only and Hidaka, et al.
10
studied only twelve subjects. Moreover, the latter authors
quantified dental contacts using an instrument (the Dental
Prescale), which can produce false positive data.
6-l0
In neither of those studies was the masticatory muscle
activity (the integrated areas of the EMG potentials over
time) calculated.
14
This parameter, which integrates the
separate assessments usually made during EMG record-
ings, can be used as a global index of masticatory muscle
activity during dynamic tasks.
14
In the current investigation, the relationship between
EMG muscle activity (area of the EMG potentials over
time) during maximum voluntary teeth clenching and the
number of occlusal contacts in intercuspal position as
detected by shim stocks was quantitatively analyzed in a
group of healthy young adult men and women.
Materials and Methods
Data from 23 white northern Italian men (14 subjects)
and women (nine subjects) were included in this study.
The subjects were selected from a group of dental school
students aged from 20 to 37 years (mean age, 22.7, SD
4.37) according to the criteria described by Ferrario, et
al.
15-l7
Briefly, all subjects had a sound full permanent
dentition (28 teeth at least), with bilateral Angle Class I
first permanent molar and canine relationships (± 2 mm),
overjet and overbite ranging from 2-4 mm, no anterior or
lateral crossbite, no cast restorations or cuspal coverage,
no previous craniofacial trauma or surgery, and no tem-
poromandibular or cranio-cervical disorders.
All subjects gave their informed consent to the experi-
ment. All procedures were noninvasive and performed
with minimal discomfort to the subject. The study proto-
col was approved by the local ethics committee. All EMG
recordings and occlusal contact detection were performed
by a single operator between 9:00 and 11:00 in the morn-
ing. In all subjects, an EMG examination was performed
immediately after occlusal analysis.
Occlusal Contacts
Actual occlusal contacts were tested by using eight
mm wide, and eight µm thick, shim stocks (Hanel, Roeko,
D-89122 Langenau, Germany). The protocol devised and
described by Anderson, et al.
12
was used: in brief, a single
operator positioned the shim stock in relation to the
occlusal surface of each maxillary tooth and asked the
subject to close in intercuspal position using light to mod-
erate force.
2
Teeth holding the shim stock were recorded
as having an occlusal contact with their antagonists. The
test procedure began from the right upper second molar
and proceeded along the dental arch until the upper left
second molar. During testing, the subjects were seated on
a dental chair in an erect position with back straight.
EMG Recordings and Measurements
The masseter and temporalis anterior muscles of both
sides (left and right) were examined. Bipolar surface
electrodes were positioned on the muscular bellies paral-
lel to muscular fibers: temporalis anterior, vertically
along the anterior margin of the muscle (close to the coro-
nal suture); masseter, parallel to the muscular fibers, with
the upper pole of the electrode at the intersection between
the tragus-labial commissura and the exocanthion-gonion
lines
15-18
(Figure 1).
The skin was carefully cleaned prior to placing the
electrodes, and recordings were performed five to six
minutes later, allowing for the conductive paste to ade-
quately moisten the skin surface. During testing, dispos-
able silver/silver chloride bipolar electrodes with a
diameter of 10 mm and an interelectrode distance of 21±1
mm (Duo-Trode; MyoTronics Inc., Seattle, WA, USA)
were used, while a disposable reference electrode was
OCCLUSAL CONTACTS AND EMG ACTIVITY FERRARIO ET AL.
2 THE JOURNAL OF CRANIOMANDIBULAR PRACTICE APRIL 2002, VOL. 20, NO. 2
Figure 1
Bipolar surface electrodes positioned on the masseter (MM) and
temporalis anterior (TA) muscles.
applied to the forehead.
EMG activity was recorded using four of the eight
channels of an instrument (De Gštzen srl; Legnano,
Milano, Italy). The analog EMG signal was amplified
(gain 150, bandwidth 0-10 KHz, peak-to-peak input
range from 0 to 2,000 µV) using a differential amplifier
with a high common mode rejection ratio (CMRR = 105
dB in the range 0-60 Hz, input impedance 10 G), digi-
tized (12b resolution, 2230 Hz A/D sampling frequency),
and digitally filtered (high-pass set at 30 Hz, low-pass set
at 400 Hz, band-stop for common 50-60 Hz noise).
The instrument was interfaced with a computer which
presented the data graphically and recorded it on mag-
netic media for later quantitative and qualitative analyses.
The signals were averaged over 25 ms, with muscle activ-
ity of the four tested muscles assessed as the mean square
root (r.m.s.) of the amplitude (unit: µV). EMG signals
were then recorded for further analysis. Details for the
EMG apparatus and raw data analysis can be found in
Ferrario and Sforza.
18
An initial recording for the standardization of EMG
potentials was made as detailed by Ferrario, et al.
17
Briefly, two 10 mm thick cotton rolls were positioned on
the mandibular second premolar and molars of each sub-
ject, and a three second maximum voluntary clench
(MVC) was recorded. For each muscle, the mean EMG
potential was set at 100%, and all further EMG potentials
were expressed as a percentage of this value (unit: µV/µV
x 100).
EMG activity was then recorded during a maximum
voluntary clench test in intercuspal position lasting five
seconds: the subject was invited to clench as hard as pos-
sible and to maintain the same level of contraction for
duration of the testing. During recording, the subjects sat
with their heads unsupported and were asked to maintain
a natural erect position. Reproducibility of surface EMG
measurements of the same muscles has already been
tested in our laboratory and found to be correct.
17
For each subject, the central three seconds of the max-
imum voluntary clench test were then analyzed, and the
EMG potential was standardized as detailed previously.
Subsequently, the masseter, temporalis, and mean total
muscle activities were computed as the integrated areas
of the EMG potentials over time (unit: µV/µV ¥ s%)
(Figures 2 and 3).
14
Data Analysis and Statistical Calculations
For each subject, the total number of occlusal contacts
in intercuspal position was computed. About half of the
sample (twelve subjects, seven men and five women) had
at least ten dental contacts, while the other half of the
sample (eleven subjects, seven men and four women) had
nine or fewer dental contacts. From the original sample
of 23 subjects, two groups were formed: Òmany con-
tacts,Ó and Òfew contacts.Ó
Within each group, descriptive statistics (mean and
standard deviation) were calculated for each variable
(age, number of occlusal contacts, masseter, temporalis,
and mean total muscle activities).
The mean values computed in the two groups were
then compared using a studentÕs t-test for independent
samples. Chi-square tests were used to compare the dif-
ferent number of teeth with/without dental contacts in the
two groups. For all analyses the level of significance was
set at 5% (p<0.05).
Results
The mean number of dental contacts in intercuspal
position measured in the many contacts group (all sub-
jects with at least ten contacts) was 13 (SD 2.4), while in
the few contacts group, on average only seven contacts
(SD 1.3) were found. Dental contacts were symmetrical
in almost all subjects, and only eight subjects had a dif-
ference of more than one contact between the right and
left side of the mouth.
As far as the first permanent molars and premolars are
concerned, the percentage distribution of dental contacts
was similar in the two groups. Differences were found for
the anterior teeth: while in the many contacts group, sub-
jects had 24% of their contacts on incisors and canines,
the few contacts subjects had only 8% of contacts on the
same teeth (Table 1).
When the number of teeth with or without one occlusal
contact at least was compared between the two groups
(Table 2), significant differences were found for the
canines (p<0.005) and the incisors (p<0.001). In contrast,
molars and premolars had a similar occurrence of con-
tacts in the two groups.
Table 3 shows the mean characteristics of the two
groups of subjects. While age was not significantly dif-
ferent between the two groups, the subjects with many
contacts produced significantly higher muscle activity in
both their masseter and temporalis anterior muscles than
the subjects with few contacts (p<0.005). The total mean
muscle activity was also different between the two
groups. On average, differences around 40 µV/µV¥ s%
were found for all muscles.
Discussion
In the present study, the masticatory muscle EMG
characteristics recorded during maximum voluntary
clench in two groups of subjects with low and high
FERRARIO ET AL. OCCLUSAL CONTACTS AND EMG ACTIVITY
APRIL 2002, VOL. 20, NO. 2 THE JOURNAL OF CRANIOMANDIBULAR PRACTICE 3
number of occlusal contacts in the intercuspal position
were compared. Significant differences were found for
muscle activity computed for both the masseter and tem-
poralis anterior muscle, with a reduced EMG activity in
subjects with a lower number of occlusal contacts than in
subjects with a higher number of contacts (Table 3). This
result agrees with previous investigations performed in
both static and dynamic conditions.
3,4,10
In those studies,
separate parameters obtained from the EMG recordings
(timing, duration, amplitude) were significantly related to
the number of occlusal contacts. Unfortunately, in no
case was a global index of masticatory muscle activity
provided. Moreover, both Bakke, et al.
3
and MacDonald
and Hannam
4
used raw EMG data, without any standard-
ization recording.
Muscle activity, namely the integrated areas of the
EMG potentials over time, has already been used as a
global index of masticatory muscle activity during
dynamic tasks.
14
During free and side-imposed mastica-
tion, both masseter and temporalis muscle activity has
been found to be related to food texture: larger values
were found for foods with a greater mechanical hard-
ness.
14
The muscle activity computed in the present study
differs from that calculated by Mioche, et al.,
14
because
standardized EMG potentials were used. In fact, they
reported a large inter-individual variability for their (raw)
muscle activity and related it to both anthropometric dif-
ferences (thickness of the subcutaneous fat layer, elec-
trode locations relative to active motor units) and var-
iations in the masticatory pattern.
The current standardization method (EMG values as
percentage of a maximum voluntary clenching on cotton
rolls) should neutralize the anthropometric differences
due to skin and electrode impedance, electrode position-
ing, and relative muscular hypo- or hypertrophy.
17
The
relative EMG values found in the experiment should thus
be affected only by the occlusal surfaces.
17
The method used in the present study for the detection
OCCLUSAL CONTACTS AND EMG ACTIVITY FERRARIO ET AL.
4 THE JOURNAL OF CRANIOMANDIBULAR PRACTICE APRIL 2002, VOL. 20, NO. 2
Figure 2
Standardized muscle activity calculated for the masseter and temporalis anterior muscles of one male in the Òmany contactsÓ group while performing
maximum voluntary clenching. Muscle activities: temporalis = 150 µV/µV ¥ s%; masseter = 200 µV/µV ¥ s%.
and location of occlusal contacts (shim stock strips) was
chosen for its simplicity, low cost, and high reproducibil-
ity.
l2
Technology currently supplies several instrumental
methods (occlusal sonography, computerized occlusal
contact sensors, pressure sensitive films, photocclusion)
which can provide information relative to timing and
force characteristics of occlusal contacts which are unde-
tectable by the simpler methods, but their actual cost/
benefit ratio in a clinical setting is yet to be determined.
6
For instance, thickness and rigidity of the sensor interacts
with dental proprioception, and false positive data can
occur.
10
Different methods for the identification of occlusal
contacts produce different numbers and patterns of con-
tacts in intercuspal position.
7,9,19
For instance, silicone
impressions record not only single contacts, but also the
area of Ònear contactÓ because of their increased thick-
ness.
7,9
In contrast, articulation papers identify single
Òspots.Ó
9
Moreover, methods that introduce a thickness of
more than 20 µm between the dental arches are likely to
alter dental proprioception and increase the number of
artifacts.
6,10
Articulation papers thinner than 20 µm are not of prac-
tical to use because the colored spot does not resist saliva.
In contrast, shim stock can be used to test pairs of teeth:
those teeth holding the shim stock are considered to have
occlusal contact with their antagonists.
2,l2
Reproducibility and reliability of the method are
already reported to be suitable for clinical assessments.
l2
Shim stock thickness (8-13 µm) is under the propriocep-
tion threshold of periodontal receptors, and the method is
not likely to record false positive contacts.
2,12,13
Several other factors should be considered in the
analysis of dental contacts in intercuspal position. Their
number may also be a function of the mandibular, head,
and body positions, the applied force, the time of
day.
5,12,13,20-22
In the present study, all measurements were
made in the morning, and with a standardized head and
FERRARIO ET AL. OCCLUSAL CONTACTS AND EMG ACTIVITY
APRIL 2002, VOL. 20, NO. 2 THE JOURNAL OF CRANIOMANDIBULAR PRACTICE 5
Figure 3
Standardized muscle activity calculated for the masseter and temporalis anterior muscles of one male in the Òfew contactsÓ group while performing
maximum voluntary clenching. Muscle activities: temporalis = 75 µV/µV ¥ s%; masseter = 75 µV/µV ¥ s%.
OCCLUSAL CONTACTS AND EMG ACTIVITY FERRARIO ET AL.
6 THE JOURNAL OF CRANIOMANDIBULAR PRACTICE APRIL 2002, VOL. 20, NO. 2
Table 1
Number and Percentage of Dental Contacts in Intercuspal Position
Group 2nd molar 1st molar 2nd premolar 1st premolar Canine Incisors
Contacts N % N % N % N % N % N %
“Many” 23 15 31 20 31 20 31 20 18 12 18 12
“Few” 21 26 19 24 17 21 17 21 4 5 2 3
Many contacts: 10 contacts for each subject (n=12)
Few contacts: 10 contacts for each subject (n=11)
Table 2
Number of Teeth Without (0) or With (1+) One Occlusal Contact in Intercuspal Position
Group Molars Premolars Canines Incisors
Contacts 0 1+ P 0 1+ P 0 1+ P 0 1+ P
“Many” 3 45 NS 7 41 NS 10 14 0.005 23 15 0.001
“Few” 5 49 12 32 19 3 2 42
Many contacts: 10 contacts for each subject (n=12)
Few contacts: 10 contacts for each subject (n=11)
Comparison: Chi-square test, one degree of freedom
NS: not significant, p>0.05
Table 3
Muscle Activity (Standardized Potentials) During Maximum Voluntary Clench
As a Function of the Number of Occlusal Contacts
Age Activity TA Activity MM Mean activity
Group (yrs) (µV/µV • s%) (µV/µV • s%) (µV/µV • s%)
“Many” Mean 21.69 130.02 113.51 120.97
(n=12) SD 2.39 30.42 33.71 31.35
“Few” Mean 23.80 91.6 74.73 82.79
(n=11) SD 5.76 16.3 24.2 18.54
Comparison p NS 0.001 0.005 0.002
Many contacts: 10 contacts for each subject (n=12)
Few contacts: 10 contacts for each subject (n=11)
Comparison: Student’s t-test t for independent samples, 21 degrees of freedom
NS: not significant, p>0.05
TA: temporalis anterior; MM: masseter
body position.
l,5,l2,13
In contrast, it is more difficult to stan-
dardize the amount of occlusal force, unless a simultane-
ous electromyographic recording is made.
l0,23,24
This is a
limitation of the present study, because the number and
area of occlusal contacts depend on bite force.
2,10,22-25
Another limitation of the current investigation may be
the reduced number of analyzed subjects. Nevertheless,
the number of subjects is not very different from that of
other investigations when restricted criteria of occlusal
and dental normality are used.
3-5,l0,20,2l,23
A third limitation
pertains to the sample selection. Only healthy subjects
were included in the study, and at present, not all the cri-
teria used can be extended to patients.
11
The number of occlusal contacts in intercuspal position
was used to divide the present sample of 23 subjects into
two groups, namely those with few contacts and those
with many contacts. The threshold between the groups,
ten contacts, was chosen because it corresponds to the
minimal values reported in the literature.
2,25
The two
groups were homogeneous for number, gender, and age
(Table 3).
In maximum intercuspation, 68% of the teeth of the
many contacts subjects had a contact with at least one
antagonist, while only 49% of the teeth of the few con-
tacts subjects had dental contacts. The difference was due
to both anterior (incisors, canines) contacts, and the pres-
ence of two contacts on each posterior tooth. It seems that
the reduced number of anterior contacts was the main
variation between the two groups. In both groups, the
number of dental contacts along the arch decreased from
posterior to anterior: 94% of the molars of the many con-
tacts group and 89% of the molars of the few contacts
group had at least one contact (Table 2). Premolar teeth
had at least one contact in 85% (many contacts) and 73%
(few contacts) of cases, respectively. Fifty-eight percent
of the canines of the many contacts subjects and 14% of
the few contacts subjects had an occlusal contact, a statis-
tically significant difference (Table 2). Incisors had con-
tacts in 31% (many contacts) and 5% (few contacts) of
cases (p>0.001). The percentage contacts computed for
the incisors in the many contacts group are comparable to
other reports in the literature,
3
while for the other teeth,
the present values are 10-15% lower. It needs to be men-
tioned that Bakke, et al.
3
used 50 µm thick strips, about
six to seven times the thickness of the present shim
stocks. In this case, a certain number of false positive
contacts may have occurred.
2,l2-l3
The number of molars
without occlusal contacts (6% in the many contacts, 11%
in the few contacts groups), as well as the number of pre-
molars without occlusal contacts in the many contacts
group (15%), are comparable to other reports in the liter-
ature.
2
In contrast, the percentage of premolars with no
contacts in the few contacts group (27%) is larger than
previous values.
2
In conclusion, and within the limitations of the present
study, this investigation confirmed that occlusal contacts
and muscular function are significantly related, at least in
young adults with a sound stomatognathic apparatus.
Any alteration to the occlusal surfaces may therefore
modify the actual performance of masticatory muscles,
because these two factors mutually interact, and com-
bined (morphology and function) clinical assessments
should be performed in all patients.
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J Oral Rehabil 1982;
9:469-477.
Dr. Graziuno Serrao received his M.D. degree from the University of
Milan School of Medicine, Italy in 1984, and his Ph.D. in Morphological
Sciences from the same University in 1996. He is currently a staff
member of the Laboratory of Functional Anatomy of the Stomatognathic
Apparatus.
Dr. Claudia Dellavia received her D.D.S. degree from the University of
Milan School of Dentistry, Italy in 1999. She has been working at the
Laboratory of Functional Anatomy of the Stomatognathic Apparatus
since 1994. Dr. Dellavia is currently attending at a postgraduate course
in Morphological Sciences in the University of Milan.
Ms. Elisabetta Caruso is a graduate student of the Dental School of
Milan University. She is preparing her DDS thesis at the Laboratory of
Functional Anatomy of the Stomatognathic Apparatus.
Dr. Chiarella Sforza received her M.D. degree from the University of
Milan School of Medicine, Italy in 1986, and her Ph.D. degree in Sports
Medicine in 1989 from the same University. She is a Professor of Human
Anatomy at the School of Sport Sciences of Milan University. She has
been a staff member of the Laboratory of Functional Anatomy of the
Stomatognathic Apparatus since its foundation in 1989, where she
coordinates research activities.
OCCLUSAL CONTACTS AND EMG ACTIVITY FERRARIO ET AL.
8 THE JOURNAL OF CRANIOMANDIBULAR PRACTICE APRIL 2002, VOL. 20, NO. 2
... Актуальность. По данным ряда авторов известно, что полная адаптация к съемным протезам наступает в течение трех месяцев [3][4][5]9]. Основным критерием привыкания пациентов к съемным протезам является синхронность работы жевательной мускулатуры и, как следствие, нормализация функции жевания. ...
... По данным ряда авторов известно, что полная адаптация к съемным протезам наступает в течение трех месяцев [3][4][5]9]. Основным критерием привыкания пациентов к съемным протезам является синхронность работы жевательной мускулатуры и, как следствие, нормализация функции жевания. ...
... Оценивание биоэлектрической активности жевательной мускулатуры является объективным способом контроля физиологического состояния жевательной мускулатуры в покое и при совершении акта жевания [3,8,9]. ...
Article
Relevance . According to a number of authors, it is known that full adaptation to complete removable dentures occurs within 3 months [3–5, 9]. The main criterion for patients getting used to removable dentures is the synchronization of the work of the masticatory muscles and, as a consequence, the normalization of the chewing function. The aim of the study was to evaluate the bioelectrical activity of the masticatory muscles in patients using the CSPP. Materials and methods . In patients of the control (n = 23) and main (n = 63) groups, electromyographic examination was performed using the electroneuromyographic system "Synapsis" (Neurotechnology, Russia). Registration of the bioelectric activity of the chewing muscles was carried out directly on the day of applying the prostheses, after 1 and 3 months, respectively. Results and discussion . The electromyographic indices of the masticatory muscles in the patients of the control group decreased within one month after the treatment and amounted to 231 ± 18.2 μV for the right and 229 ± 16.1 μV for the left proper chewing muscles. The values were also reduced for the right and left temporal muscles – 228 ± 15.2 μV and 225 ± 24.1 μV (p < 0.05). It should be noted that the electromyographic parameters in patients of the main group were comparable to the lower limit of the norm and amounted to 269 ± 16.5 μV and 256 ± 20.4 μV, respectively, after one month of treatment. Conclusions . In the treatment of dysfunction of the temporomandibular joint with the use of thermoplastic prostheses, an increase in the biopotentials of the masticatory muscles is observed. In the orthopedic treatment of patients with terminal dentition defects using thermoplastic prostheses, the electromyographic parameters of the masticatory muscles are most close to normal after 3 months of using these prostheses.
... Occlusion has been considered to affect MMA [34,35]. Previous studies on MMA and craniofacial morphology were controversial [9,11,12]; this might be due to a lack of an adequate control group and the ambiguity of the criteria for normal occlusion. ...
Preprint
Full-text available
Objectives: Masticatory function, including masticatory muscle activity and occlusal function, can be affected by craniofacial morphology. This study aimed to investigate the relationship between craniofacial morphology and masticatory function in participants who had completed orthodontic treatment at least two years before and had stable occlusion. Materials and Methods: Fourty-two healthy participants were prospectively enrolled and divided into three vertical cephalometric groups according to the mandibular plane angle. Masticatory muscle activity (MMA) in the masseter and anterior temporalis muscles was assessed using surface electromyography. The occlusal contact area and occlusal force (OF) were evaluated using the Dental Prescale System. Masticatory muscle efficiency was calculated by dividing MMA by OF. The craniofacial morphology was analyzed using a lateral cephalogram. The masticatory function was compared using one-way analysis of variance. Pearson correlations were used to assess the relationships between craniofacial morphology and masticatory function. Results: The hypodivergent group had the lowest MMA and the highest efficiencies in the masseter and anterior temporalis muscle (p < 0.05). MMA showed a positive relationship with mandibular plane angle, whereas the occlusal function demonstrated a negative relationship (p < 0.05). The anterior temporalis muscle activity negatively correlated with ramus height (p < 0.05). Conclusions: Vertical craniofacial morphology was related to masticatory function in participants with normal occlusion after orthodontic treatment. Participants with hypodivergent facial profiles may have low MMA and high occlusal function, resulting in good masticatory muscle efficiency. Clinical relevance: Vertical craniofacial morphology is an important factor to consider in orthodontic diagnosis and prosthetic treatment planning.
... In our study, an average patient from the study group had 11 missing teeth, in contrast to four missing teeth for an average control patient. Previous investigations have reported that activity of jaw-closing muscles is determined by the number of occlusal contacts-patients with a larger number of teeth that connect in maximal intercuspation showed higher muscular electromyographic (EMG) activity [29,30]. In our study, nearly 40% of subjects from the study group would require extensive prosthodontic rehabilitation, even though demand for treatment might not be well correlated with objectively determined treatment needs. ...
Article
Full-text available
According to recent scientific consensus, there is an increasing amount of evidence on the correlation between oral health and cardiovascular disease morbidity. The aim of the present study was to investigate the number of missing teeth, the presence of residual roots with necrotic pulp and teeth with caries, the type of teeth deficiencies, and periodontal status in patients after myocardial infarction (MI). A total of 151 patients after MI and 160 randomly selected controls without history of MI were enrolled in the study. Epidemiological data were collected, and dental examination was performed. Findings showed significantly more women, subjects with lower level of education, lower income, higher percentage of nicotine addiction, more frequent presence of arterial hypertension, diabetes, and obesity than in the study group. Moreover, oral status of the subjects who suffered from MI was inferior to the control group. An average patient from the study group had 11 missing teeth, when compared to four missing teeth in an average control subject (p < 0.0001). The majority of patients in the control group had occlusal contacts in intercuspal position in premolars and molars (group A), in contrast to the patients after MI, who had at least one missing supporting zone (group B) (p < 0.0001). Severe periodontitis was found in 50.3% of tests and in 30.4% of controls (p < 0.0001). A correlation was found between the edentulousness and the risk of myocardial infarction after adjusting for other known risk factors of cardiovascular diseases (OR = 3.8; 95% CI = 3.01–7.21; p < 0.0001). This case–control study showed that MI patients had more missing teeth, more residual roots with necrotic pulp, much higher incidence of edentulism and occlusal contacts in intercuspal position in fewer than four occlusal supporting zones, as well as worse periodontal status when compared to healthy subjects without a history of MI. Due to the methodology of unmatched controls, the presented results must be interpreted with caution.
... Occlusal contacts have been found to be associated with muscle thickness and function (Bakke et al., 1992;Ferrario et al., 2002). ...
Article
Full-text available
Background: Masseter muscle thickness and its relationship with vertical craniofacial morphology have been extensively studied in adults, but data on children are lacking. Objective: To examine the association between masseter muscle thickness and vertical cephalometric parameters in a group of Class II malocclusion growing children. Methods: The current study design was retrospective and cross-sectional, looking at a sample of 211 growing children with Class II malocclusion between the ages of 6 and 15 derived from two centers. Ultrasonographic masseter muscle thickness measurements and vertical cephalometric variables, including the gonial angle, were evaluated before any orthodontic treatment had been carried out. Multiple linear regression analysis was used to examine the association between masseter muscle thickness and vertical cephalometric measurements, including age and patient origin as independent variables in the analysis. Results: In the present sample, masseter muscle thickness was found to be independent of sex, but correlated with age, with older children presenting thicker masseter muscles. In the total patient sample, using multiple regression analyses, children with thicker masseter muscles had significantly smaller intermaxillary and gonial angles. No other cephalometric vertical characteristics showed associations with masseter muscle thickness. Conclusion: In growing children with Class II malocclusion, those with thicker masseter muscles are more likely to display smaller intermaxillary and gonial angles respectively.
... Saeki reported that atrophy of the periodontal ligament reaches a maximum 14 days following the removal of the occlusal contacts [18]. Moreover, Ferraio et al. [19] stated that occlusal contacts and muscular function are significantly related; that said, any al-K Author's personal copy A. Genc et al. teration of the occlusal surfaces may therefore modify the actual performance of masticatory muscles. The results of the present study broadly support the results of other studies in this area by interlinking the consequences of altered masticatory environment, i.e., an alteration in occlusal relationship, with structural changes in periodontium, masseter muscles, and masticatory function. ...
Article
Objectives This prospective study was designed to assess whether patients with skeletal deformities show characteristic masseter inhibitory reflex (MIR) and blink reflex (BR) patterns. A secondary aim was to investigate whether these reflexes change following bilateral sagittal split osteotomy (BSSO). Materials and methods Fourteen consecutive patients who underwent single-jaw BSSO and 14 class I subjects who constituted the control group were enrolled into the study. MIR and BR, obtained by the stimulation of supraorbital (SBR) and mental nerves (MBR), were electrophysiologically recorded. Sensory impairment in the mental nerve distribution was clinically tested. Three evaluation periods were specified as immediately before (T0), 1 month (T1) and 6 months (T2) after surgery. Results MIR early silent period duration was significantly shorter in the patients at T0 (p < 0.001). Sensory deficits developed on 23 sides after BSSO, of which, 17 recovered after 6 months. At T1, MBR was inelicitable bilaterally in 3 patients and unilaterally in 2 patients. These responses were still unrecordable bilaterally in 1 patient, and unilaterally in 4 patients at T2. MIR were unrecordable on 18 sides at T1 and recovered on 11 sides at T2. There were no parallels between the clinical sensory deficits and the abnormal results of the reflexes. Conclusions Shorter MIR in patients with dentofacial abnormalities may be a reflection of an adapted trigeminal reflex mechanism. Although MBR and MIR abnormalities do not develop parallel to the clinical sensory deficits, their course might provide insights into the disturbed trigeminal reflex pathways.
... Harzer et al. [28] stated that the setback of the mandible by SSRO improves the activity of the masticatory muscles. It was also reported that improved occlusal contact increases bite force [29]. Our previous study in Japan suggested that a chewing exercise for grown-up children facilitates an increase in oral function and changes in chewing patterns [30]. ...
Article
Full-text available
Recovery of oral function is one of the most important objectives of orthognathic surgery. This study investigated the effects of a chewing exercise on chewing patterns and other oral functions after sagittal split ramus osteotomy (SSRO). Ten subjects performed a chewing exercise. The control group comprised 19 patients. For masticatory function, the masticatory pattern, width, and height were assessed. For oral function, the occlusal, lip closure, and tongue pressure forces were measured. The chewing exercise was started 3 months after SSRO, and was performed for 5 min twice a day for 3 months. The masticatory pattern normalized in 60% of the patients and remained unchanged for the reversed and crossover types in 40% of the patients. In contrast, 21.0% of patients in the control group showed a change to the normal type. This may be a natural adaptation due to the changes in morphology. A more detailed study is needed to determine what does and does not improve with chewing exercise. The masticatory width significantly increased after performing the exercise. For oral function, a significant increase in the occlusal force was observed, with no significant difference in the control group. Chewing exercises immediately after SSRO improve masticatory patterns.
... Orthognathic surgery studies have also shown that postoperative EMG improvements are primarily because of the improvement in occlusal stability that result in an improvement in the neuromuscular equilibrium. 40,45,46 In the present study, an increase in OCZ during the observation period was observed with TMJR. In general, because of the lack of EMG and MVC TMJR studies, one can only speculate the causes for both the increase in sEMG activity and the increase in MVC. ...
Article
Purpose Unilateral alloplastic total temporomandibular joint reconstruction (TMJR) might influence the contralateral side joint function. This study’s purpose was to estimate the risk for contralateral TMJR and the jaw function of the contralateral untreated temporomandibular joint (TMJ). Patients and Methods A prospective cohort study design was used for patients who underwent unilateral alloplastic TMJR. The primary predictor was time after TMJR, the secondary predictors were pre-TMJR mandibular angle resection, prior ipsilateral TMJ surgeries and TMJR design (custom, stock). The primary outcome variable was the need for contralateral TMJR. The secondary outcome variables were the results of jaw function - jaw tracking, maximum voluntary clenching (MVC), surface electromyography (sEMG), and pressure pain thresholds (PPT) and patients’ quality of life (OHrQoL). Data were collected preoperatively (T0), and 1 year (T1), 2-3 years (T2) and ≥ 4 years postoperatively (T4). ANOVA with post hoc Tukey -HSD and multiple linear regression analysis were used for statistical analysis. P <.05 was considered significant. Results 39 patients were enrolled, 15 males and 24 females, average age 48.9±16.2. Two patients (5.1%) required a contralateral TMJR. Contralateral condylar motion, incisal laterotrusion and protrusion slightly decreased, while incisal opening (p=.003), rotation angle (p=.013), opening deflection, sEMG activity, MVC (p=.01), PPTs and OHrQoL all increased. Pre-TMJR mandibular angle resection had an impact on PPTs and subjective outcomes and prior ipsilateral TMJ surgeries on the opening rotation angle. Conclusion Based on this study, bilateral TMJR does not appear necessary when the contralateral TMJ is healthy. Unilateral alloplastic TMJR is associated with improved contralateral jaw function and OHrQoL.
Article
Aim: To evaluate the surface electromyography (sEMG) activity of the superficial masseter and anterior temporalis muscles at rest, during maximum voluntary clenching (MVC), and mastication, over 6 months of wearing clear thermoplastic or wrap-around retainers. Furthermore, the patients' oral health-related quality of life was assessed using the Oral Impacts on Daily Performance (OIDP) index at 6 months. Materials and methods: Sixty patients aged 14-39 years (19 males/41 females) who received upper and lower retainers after finishing orthodontic treatment were recruited. The patients were randomly divided into a clear thermoplastic retainer group (n = 30) or a wrap-around retainer group (n = 30). The sEMG activity was recorded at retainer delivery (T0), after 3 months (T1), and after 6 months of wearing (T2). The OIDP index was evaluated at T2. Results: None of the sEMG parameters for the masseter and temporalis muscles were different between the two groups at T0, T1, or T2. Over the period of 6 months, both masticatory muscles in both groups demonstrated increased sEMG activity during MVC and mastication; however, only the temporalis muscle demonstrated decreased normalized sEMG activity at rest (P < 0.05). The frequency and severity of the OIDP in the eating aspect at T2 was low and similar in both groups. Conclusions: sEMG activity of the two masticatory muscles tended to increase during MVC and mastication, while temporalis muscle activity tended to decrease at rest during the observation period, regardless of retainer type. Notably, these sEMG changes did not affect the patients' subjective masticatory function.
Article
Full-text available
Background Studies have demonstrated a relationship between dental malocclusion and posture defects. The aims of the study were to present (1) the effect of a physiotherapeutic approach to a patient with a distal occlusion defect with the use of a set of exercises to strengthen the muscles responsible for mandibular protrusion, and (2) a non-invasive and easy-to-use method to monitor the effects of therapy. Methods Five year old girl with a distal occlusion and with a low basic postural tone was referred to physiotherapy. A therapeutic program i.a. concerning a strengthening of the temporomandibular joint muscles with the use of a flexible tape was proposed. To assess the functional changes of the masticatory apparatus a photoanthropometric method was used. In side-face photos, proportions of 2 linear measurements and values of two angles on the first day of therapy, after 2 and after 4 months of exercises, with the mandible located freely and in the maximum protrusion were compared. Results A comparison of indices and angles showed a marked improvement in mandibular mobility already after two and four months of the exercises. Using the elastic resistance tape in addition to general developmental exercises allowed for increasing the mobility in the temporomandibular joint. Conclusion Malocclusion should not be considered separately, without taking into account the body posture. The work of the physiotherapist can benefit the orthodontist, correcting postural defects and consequently affecting malocclusion. A comparison of linear measurements and angles can be used to assess the progress of the therapy.
Article
Full-text available
Aim: Dental occlusion often rhymes with confusion, discrediting many research protocols. The profession seems to be in "major chaos about occlusion." This may be due to the lack of a precise classification of occlusal dysfunctions. We suggest using a classification based on the separation of three occlusal functions, with the identification of precise, objective clinical diagnostic criteria. This article aims to define a precise classification of occlusal functions, in order to be able to establish a positive diagnosis of occlusal disorders. This occlusal analysis method could then be used in the daily practice of dentists and orthodontists, with a view to align epidemiological studies that focus on occlusion, in order to obtain results capable of comparison in different studies. Materials and methods: A analysis of the literature in PubMed database published between the early 1970s and the present day identified many confusing definitions of occlusal disorders. In this paper, we propose the separation of occlusal functions into three subcategories: Stabilizing, centering, and guiding functions, defining three different subcategories of occlusal disorder. Results: Occlusal function allows the definition of three kinds of malocclusion: Stabilizing dysfunction, centering dysfunction, and guiding dysfunction. The individualization of clear subcategories could allow the study of the more pertinent impacts of pathogenic malocclusion. Conclusion: This classification of occlusal functions or dysfunctions allows lines to be drawn between different occlusal situations that are frequently confused, such as a loss of posterior occlusal support and loss of occlusal vertical dimension, infra-occlusion and loss of posterior support, short or reduced dental arch, reversed and scissor occlusion, sagittally and transversely deflected mandible, posterior occlusal interference and balancing contact, as well as natural and iatrogenic malocclusion. Clinical significance: An occlusal analysis that makes use of the three occlusal functions, "stabilizing, centering, guiding," could offer diagnostic standardization. It may also allow the avoidance of incorrect interpretations. Therefore, this occlusal function classification may be relevant to many fields, for instance, for epidemiological studies of occlusion and the periodontium, TMD and occlusion, or TMD and orthodontic treatment.
Article
Full-text available
Occlusal stability and mandibular elevator muscle function was studied in 25 women (20-30 yr of age). They had 27-32 fully erupted teeth with few treated occlusal surfaces, and craniomandibular function including mandibular mobility was normal. The aim was to analyze the influence of natural patterns of occlusal contact on electromyographic activity, unaffected by pain and functional disorders. Occlusal stability was assessed in the intercuspal and in lateral contact positions as the number of teeth with physical contact and the number of opposing pairs of teeth in contact. Electromyographic activity was recorded by surface electrodes over anterior and posterior temporalis and masseter muscles. In general, positive correlations were found between occlusal stability in intercuspal position and moderate to strong static and dynamic contractions, most significant in masseter muscles, indicating that forceful contraction of these muscles implies stable occlusion. Systematically, the duration of activity during chewing was negatively correlated with occlusal stability in the intercuspal position, most pronounced in working-side muscles. This pointed to shorter contractions with stable occlusion and is interpreted as the result of less need for stabilizing activity. It is concluded, that the correlations between occlusal stability and elevator muscle function are probably based on feedback mechanisms from periodontal pressoreceptors.
Article
Young adults and Adults were investigated with respect to the number of occlusal tooth contacts. In the habitual intercuspal position (centric occlusion) there was, on a highly significant level, a smaller number of tooth contacts at light pressure than at hard pressure.When Young adults were compared with Adults there was a significantly smaller number of contacts at light pressure in the Adults. During hard pressure, there was no significant difference between the groups. There was no significant difference in the number of tooth contacts at light and hard pressure between patients referred for orthodontic treatment and others.In the group of Young adults, approximately 5% of the contacts appeared on a restoration at light pressure, while approximately 10% did so at hard pressure. There was no significant difference between those with and without contacts on a restoration with respect to the number of contacts at light and hard pressure. If the number of contacts on study casts of 106 adults (Adults-A), after occlusal adjustment in an articulator, was compared with the number of hard pressure contacts found clinically in thirty-five of them, no significant difference was found.
Article
This clinical study compared two occlusal registration methods (Occlusal Indicator Wax and Accufilm) with the T-Scan system for the identification of guided closure contacts. The patients were divided into two groups according to the centric relation-maximum intercuspation (CR-MIP) discrepancy and comparisons of guided closure contacts were performed with the paired methods. Wax and Accufilm materials were significantly different in their agreement on guided closure contacts. The T-Scan system demonstrated less of a disparity with both methods but more closely resembled the Occlusal Indicator Wax material. The CR-MIP slide also significantly affected the agreement between methods during identification of guided closure contacts.
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Records of intercuspal position were made in 45 healthy young adults with morphologically normal occlusions. The observed perforations were analyzed according to the frequency of occlusal contacts. Most subjects had asymmetric distribution in number and location of occlusal contacts. Regardless of symmetry, a significantly higher number of subjects had approximately seven contacts on each side that were located between all posterior teeth. Contacts were most frequent between maxillary and mandibular first and second molars.
Article
The inter- and intraexaminer reproducibility in the interpretation of the registrations of the photocclusion technique as well as the number of occlusal contacts and their intensity in natural normal dentition in centric occlusion were studied in 20 adults. No significant differences were found regarding the inter- and intraexaminer interpretations for both number and intensity of occlusal contacts. A mean number of 23.8 contacts per individual, an almost symmetric and balanced distribution of the contacts between left and right sides of the dentition, and an absence of any significant differences between female and male subjects characterized the normal natural dentition.
Article
In this study the location and severity of occlusal contacts in the morning and evening on 3 separate days were recorded for 10 women. Biofeedback therapy was used after evening recordings to encourage muscle relaxation. The findings suggest that occlusion and occlusal contacts change throughout the day and depend on the physical state of the masticatory muscles and the mental state of the patient. Although this conclusion is understandable, its effects on the philosophies of occlusal rehabilitation are questionable. Further studies are needed to evaluate the significance of the contact variations in occlusal restorations placed at different times.
Article
Young adults (Md 24) and Adults (Md 41) were examined with respect to the distribution of occlusal contacts in molars, premolars and anterior teeth when exerting light and hard pressure respectively in the habitual intercuspal position. There was no difference between the right and left side and the number of contacts per tooth was low. In all groups of teeth there was a smaller number of contacts at light pressure. The lower number of contacts at light pressure in Adults when comparing with Young adults was related only to the anterior teeth. The increase of the number of contacts at hard pressure was greater for the anterior teeth than for the molars. In cases where there was a greater number of contacts present on one side, the distribution did not alter significantly when changing from light to hard pressure. Neither did the articulator-adjusted intercuspal position differ significantly in this respect from the clinically recorded intercuspal position at hard pressure. A further result was that about 50% of the individuals had 60% or more contacts on one side at light pressure. These findings stress the importance of meticulous care when performing occlusal adjustment, as the number of contacts per tooth is low and indicates the need for observing the difference between light and hard pressure.
Article
Electromyographic recordings from the anterior temporal muscle fibers bilaterally, the posterior temporal muscle fibers bilaterally, the superficial masseter muscle bilaterally, and the left medial pterygoid muscle were used to study the effects of changing the location, size, and direction of effort on specific contact points during maximal clenching tasks in human subjects. Vertical clenching efforts in the natural or simulated intercuspal position generally showed the highest muscle activities for all the muscles recorded. When the contact point moved posteriorly along the arch from incisors to molars, the activity in the ipsilateral temporal muscles was seen to increase, while the activity in the ipsilateral medial pterygoid and the masseter muscles bilaterally was seen to decrease during vertical clenching tasks. Eccentric efforts on specific contact points generally resulted in lower activity than the corresponding vertical effort. This was usually seen in all muscles, but not all values were significant. The ipsilateral temporal and contralateral pterygoid muscles showed the most activity during maximal clenches in lateral direction with little contribution from the other muscles. The temporal muscles showed the most activity in retrusive clenching, with activity in the other muscles nearly nonexistent. The medial pterygoid and masseter muscles were found to be the most active muscles during protrusive and incisal clenching, while the temporal muscle activity was low. When the size and number of contacts were increased anteriorly, a generalized increase in muscle activity was seen. The same trend occurred posteriorly but was not as consistent or significant. Cross-arch contacts were associated with a slight but significant bilateral increase in masseter muscle activity and an increase in temporal muscle activity ipsilateral to the cross-arch contact when maximum vertical clenches were performed. However, no significant increases were observed when the effort was directed laterally. The findings of this electromyographic study on change of the contact point, size of contact point, and the direction of effort applied on a contact point confirm their specific associations with the activity of muscle groups. Significant data have also been made available for a biomechanic approach of the investigation of degenerative joint changes.
Article
Young adults and Adults were investigated with respect to the number of occlusal tooth contacts. In the habitual intercuspal position (centric occlusion) there was, on a highly significant level, a smaller number of tooth contacts at light pressure than at hard pressure. When Young adults were compared with Adults there was a significantly smaller number of contacts at light pressure in the Adults. During hard pressure, there was no significant difference between the groups. There was no significant difference in the number of tooth contacts at light and hard pressure between patients referred for orthodontic treatment and others. In the group of Young adults, approximately 5% of the contacts appeared on a restoration at light pressure, while approximately 10% did so at hard pressure. There was no significant difference between those with and without contacts on a restoration with respect to the number of contacts at light and hard pressure. If the number of contacts on study casts of 106 adults (Adults-A), after occlusal adjustment in an articulator, was compared with the number of hard pressure contacts found clinically in thirty-five of them, no significant difference was found.