Journal of
Dental Research
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Tongue and Lip Forces Exerted during Deglutition in Subjects with and without
an Anterior Open Bite
William L. Kydd, Jack S. Akamine, Robert A. Mendel and Bertram S. Kraus
J DENT RES 1963 42: 858
DOI: 10.1177/00220345630420031801
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Tongue and Lip Forces Exerted during Deglutition in
Subjects with and without an Anterior Open Bite
WILLIAM L. KYDD, JACK S. AKAMINE, ROBERT A. MENDEL,
and BERTRAM S. KRAUS
Departments of Prosthodontics and Orthodontics, University of Washington
School of Dentistry, Seattle, Washington
The anterior open-bite malocclusion is one of the most perplexing problems facing the
dentist at this time. It is most disconcerting for the clinician to treat an anterior openbite occlusion only to find that in the postretention phases the patient tends to relapse
to his former problems. The dentition is subjected to forces acting on the teeth produced by the perioral musculature, by the tongue, and also by mastication via the
opposing teeth. The relative importance of these elements in influencing the position
of a tooth or group of teeth is not known.
The purpose of this study was twofold: (1) To devise a technique to determine
whether measurable differences existed in magnitude and duration of force exerted
by the lingual and perioral musculature of a series of female subjects fourteen to twenty
years of age. The subjects had been treated orthodontically and were divided into two
groups. Group A relapsed to an anterior open bite after treatment. Group B did not
relapse to an anterior open bite but maintained a normal overbite and overjet relationship a minimum of one year after treatment. (2) To define any specific difference between the groups. This study measured the forces exerted by the lingual and perioral
musculature on the anterior dentition during the act of swallowing. An effort was
made to determine whether a difference existed between two classifications of patients
in regard to tongue and upper-lip pressure on the maxillary incisor.
The resistance strain gauge, with modifications, has been used to study biting forces,
tooth mobility, behavior of prosthetic appliances, pressures exerted on the dentition,
and the swallowing pressure exerted on the hard palate and teeth.
Alderisio and Lahr' have used strain gauges to study muscle forces of the lip, cheek,
and tongue. Pressures recorded were not reported in numerical values. Winders2' 3 has
measured with strain gauges the forces exerted on the dentition by the perioral and
lingual musculature during the performance of four functional exercises. Studying resting and swallowing pressures on the dentition of 25 subjects, he has concluded that
there was no statistically significant correlation between the swallowing pressures and
the anterior-posterior position of the teeth. Kydd4 5 has experimented with this technique and has studied the use of a resistance-type strain gauge. He later evaluated
the average maximum forces exerted by the tongue and perioral structures on 30 subjects.
Kydd and Toda6 studied pressures exerted by the tongue during swallowing on three
This investigation was supported in part by USPHS research grant D-1829 from the National
Institute of Dental Research, National Institutes of Health, Bethesda, Maryland.
Received for publication October 8, 1962.
858
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Vol. 42, No. 3
TONGUE AND LIP FORCES DURING DEGLUTITION 859
areas of the hard palate: (1) the anterior palatal area; (2) lateral palatal area; and
(3) central palatal area. From 15 subjects they have concluded that magnitudes of
swallowing pressures exerted by the tongue in the anterior and lateral palatal areas
were greater than those found in the central area of the palate. They have also found
that the palatal morphology of the subject had an influence on swallowing pressures
exerted by the lingual musculature on the hard palate.
In the other methods used to measure intraoral pressures, the pressure transducers
have not been placed directly within the mouth, but connecting tubes have been used
for pressure transmission within a closed system. Investigators who have used this
system or modifications of it include Feldstein7 Rushmer and Hendronj8 Margolis and
FIG. 1.-Strain-gauge placement on the labial and lingual surfaces of upper central incisor
Prakash,9 Fyke and Code,10 Sims,"l Kelley, Wilbur, Schlegel, and Code,12 and Gould
and Picton.13
METHODS AND MATERIALS
The devices employed in this study consisted of pressure transducers utilizing resistance-strain gauges. The pressure transducers reponded to a force exerted upon
them by altering the voltage, which in turn was amplified and recorded.
A pressure transducer was made by using resistance-strain gauges. A method of
placement was devised to situate the transducer as close to the labial and lingual surface of the maxillary central incisor as possible (Fig. 1). The transducers protruded
less than 2 mm. from the labial and lingual surfaces of the maxillary central incisors,
so that recording artifact from adjacent tissues was not significant.13
The pressure transducer was composed of two systems. The first was a stainless-steel
cantilever beam that flexed on its free end as pressure was applied. Within its proportional limit, the amount of deflection of the tapered steel and epoxy-resin cantilever
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860 KYDD, AKA MINE, MENDEL, A ND KRA US
J. dent. Res.
Alay-June 1963
beam was nearly proportional to the stress exerted on it. The second system of the
pressure transducer consisted of the resistance-strain gauges. The strain gauges were
bonded to either side of the cantilever beam by an amine-hardened epoxy resin. As
the cantilever beam was stressed in either direction, the strain-gauge wire was also
deformed, with an accompanying alteration in the resistance. This low-frequency
change in resistance induced an amplitude modulation in the 400-cycle carrier wave.
This modulation of the carrier wave was amplified and recorded.
The pen deflections that were recorded were converted back to their respective
pressure values by a known calibration pressure applied to the testing device. From
this calibration recording, a graph was constructed to convert millimeters of pen deflection to pressures in grams per square centimeter.
The calibration devices consisted of a closed cylindrical plastic chamber containing
a platform on which the transducers were mounted, an inflatable rubber balloon that
was the analogue of tongue and lip, and a mercury manometer with rubber tubing
connected to the balloon. The balloon was inflated to contact the pressure transducer,
and pressure was exerted in uniformly increasing increments to cover the magnitude
of the subject responses. Since within a closed system all gases exert pressure equally
in all directions, the pressure that was registered on the mercury manometer would
be equal to the pressure exerted by the balloon on the transducer. Before and after
each recording session, the transducers were checked for accuracy by recalibration.
The use of a single strain gauge with only two lead wires will cause a recording artifact. Variation in ambient temperature of the oral cavity introduces a variable resistance
in one leg of the bridge, causing the recorder to see a strain that is actually an artifact.
Compensation for temperature variation in the leads can be provided by using the
Siemens three-lead method. In this three-lead method, two of the leads are in adjacent
legs of the bridge, which cancels their resistance changes due to temperature and does
not disturb the bridge balance. The third lead is in series with the power supply and
is therefore independent of bridge balance. In this way the gauges were temperaturecompensated (Fig. 2).
Simultaneous recording of tongue and lip pressure on the maxillary central incisor
during swallowing was registered on two sample populations. Group A consisted of 5
cases, at least 1 year out of the retention phase of treatment, who exhibited good
occlusions. Group B was made up of 6 patients who had been treated and relapsed into
an anterior open bite and who clinically exhibited a tongue thrust. All of the subjects
ranged from fourteen to twenty years of age.
The experiment was disguised by telling the patient the testing procedure consisted
of "an electronic device to test the effectivenss of the retention phase of their orthodontic treatment." The patients were given no other information regarding the experiment, to minimize the subject bias.
Data were obtained while the subjects performed the three following swallowing
exercises: (1) the swallowing of 2 cc. of water; (2) the swallowing of saliva on command; and (3) the involuntary swallowing of saliva, while the subject was left alone
in the testing room. The subjects were seated comfortably in a chair in a relaxed atmosphere. During most of the recordings, the subjects were reading magazines, with a
background of music.
At the initial appointment, the orthodontic bands were pinched direct, and gold
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Vol. 42, No. 3
TONGUE AND LIP FORCES DURING DEGLUTITION 861
siamese edgewise brackets were soldered to receive the edgewise wire framework of
the pressure transducer. The three succeeding appointments were spaced at 1-week
intervals. During each appointment or trial, the afore-mentioned exercises were performed with at least seven repetitions of each exercise.
Raw data obtained consisted of two simultaneous recordings, one representing the
activity of the tongue and the other the lip. Elapsed time was automatically recorded
in seconds by a time marker. Dimensions of these raw data explored were time interval
between maximal recorded pressures of the lip and tongue on the dentition. This represented in time the difference between pressure of lip against the teeth and pressure
of tongue against the teeth. A value of zero denoted that both tongue and lip applied
maximum recorded pressures simultaneously. Positive values indicated those instances
when the lip acted before the tongue.
ACTIVE
STRAIN
3 IDENTICAL LEADS IN
COMMON SHIELDED CABLE
BENDING
LOAD
V
FIXED
BASE ___
_
iFI~tt
0
|
30
~~~~~WIRE-WOUND
|RESISTORS
CANTILEVER
BEAM
FIG. 2.-Three-wire lead for temperature compensating wire strain gauges. The two gauges double
the sensitivity per unit load.
The second recording was the duration of pressure application of the tongue and lip.
Values represented mean time in seconds elapsed between initiation, duration, and
termination of the pressure curve. This measurement represented duration of pressure
that was applied to the dentition by the lip.
The raw data that were compiled and the two dimensions of measurement were
subjected to an analysis of variance (Tables 1 and 2) to determine whether statistically
significant differences existed between the anterior open-bite subjects and the control
group, between swallowing exercises, and in duration and magnitude of pressure exerted
by the tongue and lip. Tables of mean values were also compiled (Tables 3 and 4).
RESULTS
General observations of maximal pressures.-The anterior open-bite cases
and the controls exhibited significant differences in maximal pressure exerted by the
tongue and upper lip during all types of swallowing utilized in the following ways:
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862 KYDD, AKA MINE, MENDEL, AND KRAUS
J. dent. Res.
May-June 1963
(1) the mean tongue pressure of the anterior open-bite sample (285 gm/cm2) exerted
was at least twice as much as the controls (123 gm/cm2); and (2) simultaneously,
the mean upper-lip pressure of the open-bite sample was 45 gm/cm2, while the control
sample had a mean pressure of 70 gm/cm2, which indicates that the open-bite sample
had only 65 per cent of the lip pressure of the controls.
Significant differences in the duration of pressure applied by tongue and upper lip
during swallowing were exhibited between anterior open-bite cases and the controls.
Mean values indicated that the thrusters exerted both tongue and lip pressures against
the teeth for longer durations than the controls (Table 3). The lip pressure of the
TABLE 1
ANALYSIS OF VARIANCE OF TIME INTERVALS BETWEEN
LABIAL AND LINGUAL PRESSURE PEAKS
D.F.*
Sumres
Squares
M.S. t
F.1
P-§
0.23
0.20
0.23
0.10
1.76
0.76
5%
.........
1
2
63
33
4.61
...............
99
11.84
Source of Variance
Between anterior open-bite
subjects and controls ...
Between swallow types
Interactions .......... ...
....
Replication error
Total
6.60
5%
.................... ........
0.13
1.00
........
..........
I F-distribution.
Degrees of freedom.
t Means square.
*
§ Level of significance.
TABLE 2
ANALYSIS OF VARIANCE OF DURATIONS OF PRESSURE EXERTED BY
TONGUE AND BY LIP DURING THREE TYPES OF SWALLOWING
Source of Variance
Between anterior open-bite
subjects and controls
Between swallow types
Between tongue and lip .....
Residual error .............
.....
Total
.................
D.R.
Squares
M.S.
F.
P.
1
2
1
193
5.70
7.80
7.17
75.16
5.70
3.90
7.17
0.38
15.00
10.26
18.86
1.00
1%
1%
1%
197
95.83
.....................
.........
.........
TABLE 3
MEAN DURATIONS OF TONGUE AND LIP PRESSURES (IN SECONDS)
INVOLUNTARY S.
COMMAND S.
WATER S.
ALL S.
SAMPLE
Lip
Tongue
Lip
Tongue
Lip
Tongue
Lip
Tongue
jects ................
Controls.............
2.26
1.97
1.81
1.30
2.22
1.62
1.62
1.38
1.57
1.34
1.38
1.21
2.02
1.64
1.60
1.30
Total population....
2.13
1.58
1.94
1.54
1.47
1.30
1.84
1.45
Anterior open-bite sub-
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TONGUE AND LIP FORCES DURING DEGLUTITION 863
Val. 42, No. 3
thrusters was longer than that of the controls by 380 milliseconds. The tongue-pressure
duration was longer by 300 milliseconds. The total sample showed a mean pressure
duration in all swallows of 1.84 seconds for the lip and 1.45 seconds for the tongue.
Involuntary swallowing evoked the longest duration (2.13 seconds, lip; 1.54 seconds,
lip; 1.30 seconds, tongue). In the total sample, the lip showed longer mean duration
in all exercises and exceeded the duration of the tongue force by a mean difference of
390 milliseconds.
The time interval between maximum lip and tongue pressures was found to be nearly
the same in the tongue-thruster and control groups. In the whole sample studied, the
mean time interval between lip and tongue maximum pressures was 376 milliseconds
(Table 4). This means that in the sample studies a phase relationship occurred; i.e.,
a maximum lip action occurred approximately two-fifths of a second before the maximum action of the tongue.
A significant difference was found between the anterior open-bite cases (Group A)
and Group B. The anterior open-bite subjects (Group A) exerted pressures on the
TABLE 4
MEAN TIME INTERVALS BETWEEN LIP AND TONGUE PRESSURE PEAKS
(IN MILLISECONDS)*
Command
Involuntary
Swallow
Swallow
Sample
Anterior open-bite subjects
Controls .....................
Total population.........
*
Values
Water
Swallow
All
Exercises
515
311
411
324
339
299
422
309
436
372
321
376
accurate to 10 milliseconds.
dentition for a longer duration than did the latter (Group B). It was also found that
in the whole sample involuntary swallowing evoked pressures of the longest duration,
command swallowing second, and water swallowing pressures of the shortest duration.
It was also found that the upper lip presses against the teeth longer than does the
tongue.
For the open-bite sample, the mean tongue-to-lip pressure ratios computed for each
individual, trial, and exercise were found to be of approximately 3 to 1 or more.
However, the normal sample ratios did not exceed 3 to 1. Stated briefly, the individuals
exerting three times the tongue pressure as lip pressure had relapsed to an anterior
open bite.
In this study, the tongue did not protrude past the labial edge of the upper central
incisor during swallowing in the anterior open-bite subjects-i.e., tongue thrustersexcept once during this study.
DISCUSSION
Three investigators have reported estimates of swallowing frequency. Kincaid14
reported a mean of 1,600 per day, measured by placing a hydraulic cuff over the hyoid
bone of his subjects and recording movements of the larynx during swallowing. He
too found swallowing frequency to be highly variable. Kunvara15 determined frequency
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864 KYDD, AKA MINE, MENDEL, AND KRA US
J14-ay-June 1963
of swallowing by counting the number of tongue thrusts during swallowing. He reported
2,400 per day. Straub16 reported 2,400 per day (two per minute during waking hours
and one per minute during sleep) but did not mention how this was determined. The
average of these different estimates is 2,166 swallows per day. The lip pressure of the
anterior open-bite subjects was longer than that of the controls by 380 milliseconds.
The tongue-pressure duration was longer by 300 milliseconds. Mean pressure duration
of tongue and lip of the anterior open-bite subjects was approximately I second longer
than the tongue- and lip-pressure duration of the controls. This difference in duration
was found to be statistically significant. The question then arises: Could a difference
of I second have any biological and clinical significance?
The line of demarcation between what is and what is not clinically significant is
difficult to draw because of great variability among individuals. However, if these
differences were projected over a greater period of time, their significance might be
more clearly assessed. It was therefore decided to project these differences over a
24-hour period by multiplying mean intra-swallow values by estimated frequency of
swallowing during a 24-hour day. An estimate of frequency of swallowing was derived
from the literature.
Mean difference of lip- and tongue-pressure duration of thrusters and non-thrusters
in the present study was determined to be I second. Multiplying this by 2,166 swallows, it was found that such a difference would amount to 11 minutes per day (i.e.,
thrusters apply tongue and lip pressures against the teeth 11 minutes longer than do
non-thrusters in a 24-hour period). For the sake of perspective, it was decided to
compare this difference with the duration of swallowing pressures of the sample over
a projected 24-hour period. The sample showed a mean duration in all swallows of
1.84 seconds for lip and 1.45 seconds for tongue or a mean duration of 1.65 seconds.
This mean duration projected onto a 24-hour period would amount to 61 minutes.
The difference of 11 minutes compared with the total duration of swallowing pressures
of 61 minutes represents an 18 per cent increase of pressure duration in the anterior
J. dent. Res.
open-bite cases.
No difference was found in time interval between maximum lip and tongue pressures
in the anterior open-bite and control groups. Neither were any differences found between the three types of swallows tested. In the sample studied, the mean time interval
between lip and tongue maximum pressures was 376 milliseconds (Table 4). This
means that maximum lip action occurred approximately 2 second before maximum
action of the tongue.
Considering each sample separately, we find the following measurements: the mean
pressure of the tongue in the open-bite sample was 285 gm/cm2 and the mean lip
pressure for the same sample was 45 gm/cm2, or approximately 6.3 to 1.0 tongue to
lip pressure. This approximated the 5.1 to 1.0 composite computed ratio of tongue
and lip mean ratios taken from the entire open-bite sample. This points out the excessive tongue-to-lip forces exerted in the open-bite sample (Group A) in comparison
with the non-open-bite subjects (Group B).
Group B exhibited a mean tongue pressure of 123 gm/cm2, with 70 gm/cm2 registered for the mean lip pressure. This is also in accord with the computed lip-to-tongue
mean ratio of the entire sample of 1.4 to 1.0.
The entire sample, consisting of both groups, had a mean maximal tongue pressure
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Vol. 42, No. 3
TONGUE AND LIP FORCES DURING DEGLUTITION 865
of 211.88 gm/cm2 as compared with 56.53 gm/cm2 for the lip, showing a tongue-to-lip
pressure in the ratio of 3.7 to 1.0.
When we consider the three different swallowing exercises involving the entire
sample, we find the following values. (1) Swallowing on command exhibited the
highest mean tongue maximal pressure of 235.24 gm/cm2 as compared with the mean
maximal pressure of the lip of 67.95 gm/cm2 that is also the highest lip pressure of
the three exercises. Therefore, the proportion of tongue pressure to lip pressure for
swallowing on command is 3.56 to 1.0. (2) Pressure exerted during involuntary swallowing proved to be the intermediate exercise. The mean tongue pressure was 216.58
gm/cm2, with 67.31 gm/cm2 registered for the mean lip maximal pressure with a ratio
of 3.2 to 1.0. (3) The exercise with the least pressure exerted proved to be the swallowing of 2 cc. of water. The mean tongue pressure of 183.83 gm/cm2 is contrasted to the
mean lip pressure of 34.33 gm/cm2, with a corresponding value of 5.38 to 1.00.
Swallowing on command and involuntary swallowing seemed to exert the same
relative pressure, as well as a similar tongue-to-lip ratio, with the swallowing of water
exercise offering the least pressure exerted but having the largest imbalance of tongue
pressure to lip pressure.
The highest and lowest mean maximal pressures of both the open-bite (Group A)
and the Group B sample were as follows: (1) the open-bite (Group A) pressures for
the tongue ranged from 103 to 573 gm/cm2, while those for the lip ranged from 5 to
178 gm/cm2; (2) the Group B pressure range for the tongue was from 50 to 278
gm/cm2 and for the lip a range of 7 to 196 gm/cm2. The Group A open-bite individuals
have a higher range of tongue pressure than the Group B, and, conversely, the Group
B individuals have a higher range for the lip pressure than do the anterior open bites
(Group A). This also might cast some doubt as to the validity of clinical observation in
determining what is an abnormal and normal tongue activity in a given patient when
we see the great overlapping in the range of tongue forces in either group.
The range of mean swallowing pressures exerted by the tongue, in this study, was
from 43.27 to 573 gm/cm2, which included all types of swallowing exercises. This is
of the same order of magnitude as that reported by Winders3 in his study of pressure
on the dentition. The analysis of variance of computed lip over tongue ratios showed
significant differences between open-bite and normal samples. It did not show a difference in the ratios between the three types of exercises.
SUMMARY
A technique was devised to measure the magnitude and duration of forces exerted
the dentition during deglutition. Pressures exerted on the area of the maxillary
central incisors by the lip and tongue were measured in two groups of orthodontically
treated subjects. The Group A, anterior open-bite cases, i.e., tongue thrusters, consisted of 6 subjects. The Group B or non-thrusters, consisted of 5 subjects who did
not relapse to an anterior open bite. A pressure transducer was used to record pressure
on the labial and lingual of the maxillary left central incisor.
The following results were observed: (1) The mean tongue pressure of the anterior
open-bite sample was twice that of the controls. These differences were statistically
significant. (2) Anterior open-bite subjects, i.e., tongue thrusters, exerted both tongue
and lip pressures for a longer duration than did the non-open-bite subjects. (3) There
on
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866 KYDD, AKAMINE, MENDEL, AND KRAUS
J. dent. Res.
May-June 1963
was a lip-tongue synergy in the oral stage of swallowing for all subjects. The lip
always applied pressure prior to the tongue. However, a difference did exist in duration
of pressure and magnitude of pressure applied to the teeth by tongue and lip during
swallowing. (4) The tongue did not protrude past the labial edge of the upper central
incisors during swallowing among the anterior open-bite subjects, i.e., tongue thrusters,
with the exception of 1 of the 6 subjects.
A basic difference between anterior open-bite subjects, i.e., tongue thrusters, and
subjects without an anterior open bite was found in the duration of lip and tongue
pressures applied to the anterior teeth. Anterior open-bite subjects, i.e., tongue thrusters, applied both tongue and lip pressure against the anterior teeth for a longer duration of time than did the subjects without an anterior open bite.
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Swallowing, Angle Orthodont., 28:226-38, 1958.
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Effects, and Results in Relation to Orthodontic Treatment and Speech Therapy, Amer. J. Orthodont., 47:596-617, 1961.
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