APRIL 1953 VOLUM E 46 • NUMBER 4

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cJ OF FffE
Tfffi 1Affi/i /C'AA7 DENTAI ASSOC/AT/OJV

The physiology of the stomatognathic system

Bernard Jankelson,* D .M .D .; George M. Hoffman,f D .M .D .,
and J. A. Hendron, ]r.,% Seattle

The maintenance or restoration of the PURPOSE AND SCOPE

normal physiology of the stomatognathic OF T H E INVESTIGATION
system can best be achieved if procedures
are based on a thorough knowledge of The purpose o f the investigation was to
normal function. determine the facts of the physiology of
Because this region is obscured by the
overlying soft tissues of the face, investi­
Prize-w inninq essay read before the M id w in te r M e e t ­
gation has been difficult and incomplete. in g o f the C h ic a g o Dental Society, Fe bru ary II, 1953.
Furthermore, the problem is one of move­ This in ve stiga tio n was d o n e using the facilitie s o f the
d e p artm e nt of biop h ysic s and_ p h y siology, University
ment and does not lend itself readily to of W a sh in g to n Schoo l o f M e d icin e , a n d was su pporte d
(in part) by a research gra n t from the N a tio n a l H e art
investigative methods that are essentially Institute o f the N a tio n a l Institutes of H ealth, Public
H ealth S e iv ice.
static in character, such as anatomic dis­ *D ip lo m a te , A m e ric a n Board o f Prosthodontics; c lin i­
cal a sso ciate an d spe cial lecturer in prosthodontics,
section, still roentgenography and check- U niversity of W a sh in g to n Sch o o l o f Dentistry; directo r,
bites. Yet it is on the necessarily meager Seattle Prosthetic Sem inar.
fT echnical research associate.
information provided by these procedures tX -ra y engineer, de p artm e n t o f b io p h ysic s and ph y­
that presently accepted concepts of sio lo g y, University of W a sh in g to n Schoo l of M e d icin e .
1. H ild e b ra n d , G . Y. Studies in m asticato ry m o v e ­
stomatognathic physiology are based. ment o f hum an low er ¡aw. Ska nd ina v. A rch . f. Physiol.,
vol. (su p p l.) 1931, p. 3.
Notable exceptions to the use of static 2. Kurth, L. E. M a n d ib u la r m ovem ents in m astication.
methods o f inquiry are the work of J .A .D .A . 29:1769 O ct. 1942.
3. Kurth, L. E. M a n d ib u la r m ovem ents and a rticu ­
Hildebrand,1 of Kurth,2’ 3 and of Bos­ lator o cclusion . J .A .D .A . 39:37 Ju ly 1949.
well,4 all working in the field of jaw 4. Boswell, J. V. Practical occlusio n in relation to
com ple te dentures. J. Pros. Den. 1:307 M a y 1951.
movements. 5. Klatsky, M eye r. A cin e flu o ro g ra p h ic study o f the
hum an m asticato ry a p p a ra tu s in function. A m . J. O rth o -
A beginning in the field of cinefluorog- dont. & O ra l S u rg. 26:664 Ju ly 1940.
raphy for dental investigation was made 6. Riesner, S. E. H e a d and fac ia l pain s associate d
with distu rb a n ce s of the te m p o ro m a n d ib u la r joints.
by Klatsky5 and by Riesner.6 Ne w Y o rk D.J. 13:65 Feb. 1947.

375
376 • THE JO U R N A L OF THE A M E R IC A N DENTAL A SSO C IA TIO N

the region. Since investigation o f physi­ 2. Moderately resistant food: roast

ology is essentially a problem of dynamics, beef, short ribs, crisp apple.
it was necessary to explore further stoma- 3. Soft food: cheese.
tognathic function with the tools most Cinefluorographic studies were made
suited for the investigation of movement. during eating and during the “ glide”
Although the entire stomatognathic (nonmasticatory grinding) from both
system came into the investigation, this posteroanterior and lateral aspects. Dur­
report deals largely with those aspects of ing the investigation of mastication, the
function that involve tooth contact or question of the frequency of tooth contact
occlusion. Especially explored was the was explored. Cinefiuorography alone
question of the occurrence and the man­ proved inadequate for the investigation of
ner o f tooth contact during the act of this aspect of the problem and it was
eating and during swallowing. found necessary to further investigate the
frequency of tooth contact and the num­
DESCRIPTION OF EXPERIM ENTS ber of chewing strokes by means of other
apparatus which will be described later.
The action of both the natural dentition Cinefluorographic studies were made of
(varying degrees of wear) and of the the action of the condyles during incision,
artificial dentition (zero degree cusps to mastication and deglutition, and during
45 degree cusps) were studied. Thirty- the “ glide.” Opacification o f soft tissues
five subjects, of both sexes, ranged in age was found to be unnecessary for study of
from 11 to 82 years. In order to eliminate tongue and palate, as definition proved
the variables that might have occurred to be adequate.
through the use of subjects with precon­
ceived ideas, no dentists or dental students MATERIALS AND M ETH ODS
were used in the investigations. For the
studies of incision, mastication and de­ Cinefluorographic Technic • The appara­
glutition, subjects were given food, then tus used has been described previously.11
requested only to “ eat the food,” begin­ Cinefiuorography was done by radiating
ning on signal. Incision, mastication and through the subject with a 500 milli-
deglutition were studied only as they ampere rotating anode tube, to a high
occurred naturally during the act of eat­ intensity fluorescent screen. The screen,
ing. Instructions such as “ chew it hard” 7 encased in a light-proof x-ray table, was
were purposely avoided because they photographed by a motion picture camera
might introduce a conscious effort that at the rate of 15 frames per second. In
would interfere with and alter the per­ order to gain the greatest length of film
formance of a normal physiologic act. without exceeding a radiation limit of
For the studies of the “ glide” 2’ 3 (non- 20 r, the camera and x-ray circuit were
masticatory grinding8), the subjects were synchronized through a pulsing device to
instructed to slide the mandibular teeth
into protrusive and lateral positions while
keeping the teeth in contact.9
Since it became apparent early in the 7. M c L e a n , D . W . D is c u s s io n o f V. R. T r a p o z z a n o 's
investigation that, as previously re­ a n d J . B. L a z a r r i's E x p e r im e n t a l st u d y o f the t e s tin q o f
o c c lu s a l p a t t e r n s o n the s a m e d e n t u r e b a s e s . J. Pros.
ported,10’ 5 the act of eating varied with D e n . 2:458 J u ly 1952.
8. S h a n a h a n , T. E. J . P e rs o n a l c o m m u n ic a t io n .
the character of the food, studies of the 9. H a n a u , R. L. A r t ic u l a t io n d e fin e d , a n a ly z e d a n d
various phases of eating were made with fo rm u la t e d . J . A . D . A . 13:1694 D e c . 1926.
10. W a ll a c e , J . S. T h e p h y s i o l o g y o f m a s t ic a t io n a n d
three types of fo o d : k in d r e d s t u d ie s. L o n d o n , J. & A . C h u r c h ill, Ltd., 1903,
p. 8, 9.
1. Highly resistant food: tough steak,
11. R u sh m e r, R. F.; B ark, R, S., a n d H e n d r o n , J. A .
fibrous celery. C li n i c a l c in e f iu o r o g r a p h y . R a d i o lo g y 55:588 O c t . 1950.
 JA N KELSO N — H O F F M A N — H ENDRO N . . . VO LUM E 46, APRIL 1953 • 377

turn off the x-ray during the time the

film was in motion between frames. With
roentgen-ray exposure of 200 milliam-
peres and 100 kilovolt peak at a 40 inch
tube-screen distance, a total of seven sec­
onds running time was acquired. The re­
sulting film (Fig. 1) was seven feet long
when made with a 35 mm. camera. T o
allow lengthy analysis of this compara­
tively short time o f action, the individual
strips of film were spliced end-to-end,
forming a loop that could be run re­
peatedly through a projector for any de­
sired time. For the purpose of making a
demonstration film, such loops were
printed on duplication film to give long
repetitive runs of each individual strip.

Simultaneous Occlusal Contact and Ver­

tical M otion Graphing • A subject with
“ normal” occlusion was chosen. It was
also necessary that this subject have op ­
posing posterior metallic full crowns. The
subject’ s occlusion was equilibrated to a
fine degree. Stainless steel orthodontic
bands were fixed to the crowned teeth in
a manner to assure definite electrical con­
tact, and extremely flexible 22 gauge
stranded plastic-covered copper wire was
soldered to the orthodontic bands and
carried forward and out of the mouth.
The wires were affixed to the buccal sur­
faces of the teeth in the respective arches
in order to avoid interference with normal
mastication. Four millivolts was applied Fig. 1 ' Cinefluorographic record of the se­
to the crowns through the 22 gauge wires quence of events during eating
and an EKG amplifier (oscillograph)
was placed in series with this circuit. The
output of the amplifier drove one pen of
a multiple channel direct-writing re­ M ethod of Recording Vertical Motion
corder. When the opposing crowns made Simultaneously with Tooth Contact • An
contact, the circuit was closed and the accordion bellows tube was affixed under
four millivolts was amplified and re­ the gnathion of the mandible and
corded graphically as an abrupt deflection anchored by a strap over the head. The
caused by sudden excursion or displace­ pneumatic pressure within the bellows
ment of the galvanometer, which estab­ actuated a strain gauge, the output of
lished the fact o f absolute occlusal con­ which was amplified to drive another
tact. Thus it was possible to establish the channel of the recorder. This assured
frequency of occlusal contact during correlation o f vertical motion to occlusal
mastication (Fig. 2 ). contact (Fig. 2).
378 • THE JO U R N A L OF THE A M E R IC A N DENTAL ASSO C IA T IO N

The number of subjects analyzed by the hand and arm twisted the food for­
this method was limited and this is not ward and downward. After the food was
presented as a complete analysis of the torn off with the teeth in the end-to-end
subject. position, the mandible dropped, the lips
guided the bolus toward the tongue, and
Report of the Results • Division of the the tongue and cheeks placed it between
act of eating into incision, mastication the teeth as the mandible closed to begin
and deglutition was purposely avoided mastication.
during the investigation. This classifica­
tion is used herewith, however, because Moderately Resistant Food • After the
of its convenience for purposes of report­ mandible had engaged in prehension of
ing. the food, movement of the mandible pos­
teriorly toward centric position began.
INCISION H ow far toward centric position this
movement progressed apparently de­
Incision was investigated by cinefiuorog­ pended on how rapidly the resistance of
raphy* from the lateral and postero- the food increased as it was compressed
anterior views, and by the stylus graphing between the teeth (Fig. 2 ). When m od­
originating from the accordion bellows erately resistant food was involved, re­
tube and strain gauge, as described trusion was interrupted before the
earlier. Subjects were requested to “ eat mandible had returned completely to
the food” so that incision would occur centric position (Fig. 3 ). Then the short
incidentally, as a natural part of the act oscillating movements (Fig. 4) began
of eating, and not as a voluntary separate cutting into and thinning the food at that
act. A report of performance with each position. The food tore off at the thinned
type of food follows. part before the teeth had cut completely
through and before contact of teeth o c­
Highly Resistant Food • The mandible curred. The mandible then opened, the
opened, then closed in protrusion, and the lips guided the bolus toward the tongue,
food was grasped between the teeth in and the lips and the cheek and tongue
the protrusive or end-to-end position. acted together to place the food between
When the mandible contacted the food, the teeth preparatory to chewing. Partici­
retrusion o f the mandible! began, but re- pation in the act by the hand and arm,
trusion stopped when definite resistance and by the head, neck and shoulders, was
was encountered (Fig. 3 ). Hence incision evident throughout the act.
of extremely tough food often occurred
entirely in the end-to-end position. As the Soft Food ' The mouth opened, the
mandibular teeth pressed further into the mandible moved forward and grasped the
food and muscular tension increased, the food in the protrusive position, then
movement abruptly changed from an sheared into the food moving toward
essentially continuous stroke to a move­ centric position without interruption
ment of rather minute forced oscillations (Fig. 3 ). The food was not cut entirely
(Fig. 2, 3, 4 ). Pending further investiga­ through by the teeth but was parted at
tion, the true character and significance the thinned out area.
of this movement must remain in the
realm of speculation. All the time that Discussion of Findings on Incision • It
the mandible was cutting into the food was noteworthy that only with food so
and tearing it back toward the centric soft that the food did not build up pres­
position, the head and shoulders were sure as the teeth moved into it, did the
rigid or were pulling backward, while act of incision appear as an uninterrupted
 JA N K E L SO N — H O FFM A N — H ENDRO N . . . VO LUM E 46, APRIL 1953 • 379

Fig. 2 ' Com posite graph of vertical m otion

and tooth contact during eating o f crisp apple.
A : Strokes during rapid tapping o f teeth. B :
Incising m ovem ent. C : M asticatory cycles. D :
t
D e lib era te ^
\
t a p p in g --.
T ooth contact deflections. E : Current leakage
deflections

shearing or tearing movement toward

centric position. The greater the re­ 5
sistance of the food, the sooner progress
toward centric position stopped and the
relatively continuous stroke changed to
the oscillating type. The obvious cutting

£
efficiency of the minute oscillating strokes
of this action, and the fact that the action
occurred when heavy pressures were
necessary to cut into the food, make it
likely that they had a cutting function.
That they were also a means o f control
was suggested by the fact that they were
equally or more apparent through a much
greater range in the incising of a crisp
apple, where great pressure was not a fac­
tor, but where sudden splitting of the
apple necessitated control of movement
to avoid sudden heavy shock contact of
teeth.
It was plain that incision of food is
seldom performed by the teeth alone. The
action of the mandibular teeth, grasping
the food and tearing and thinning it Sh ift
backwards, was aided by the head and
shoulders pulling in the same direction,
at the same time as the hand and arm
pulled, twisted, and tore the food for­
ward and downward in the opposite di­
s 4 2 strokes

rection, until it broke at the portion that

had been thinned by the teeth. With re­
sistant, tough fibrous food, the morsel * 4 7 strokes
First
parted where it had become thinner as s w a llo w (

the teeth cut into it and as the pull of

the hand tore and twisted it off while the
teeth grasped it between them and held
it. With softer foods the movement of
the teeth toward centric position con­ -irst p oin tf
' c o n ta c t\
tributed a greater proportion of the tear­ • final
s w a llo w
ing action. Incision, then, was not a
simple act ofteeth cutting through food
380 • THE JO U R N A L OF THE A M E R IC A N DENTAL A SSO C IA T IO N

incision of food by six subjects wearing

denture prostheses. The cusp angulation
of dentures worn by those in the group
varied from 0 degrees to 45 degrees.
Stability of the bases ranged from ade­
1 1 quate to inadequate.
Those subjects with inadequate bases
incised by pushing the food by hand up­
M O OERATELY R E S IS T A N T SO FT FO O D
ward and backward against incisors or
FO O D
cuspids, while the tongue was retruded,
arched, and braced to support the post­
Fig. 3 • Schem atic illustration of incision
dam area of the maxillary dentures. The
mandibular teeth followed the progress
o f the food upward as it was pushed
until it was severed.12 Rather, in each and sheared off against the maxillary in­
subject studied there was evidence of cisors by the hand, but they did not act
participation in the act by the muscles as cutters. Rather they functioned as a
that drew the head back or braced it mild stabilizer and participated in ma­
rigidly, by the hand and arm that held neuvering the incised portion after it be­
the food and pulled forward and twisted came separated. Subjects with more ade­
to tear it off, while the mandible was quate denture bases tended to function
braced or was moving posteriorly. The more nearly like those with natural den­
food was torn, and parted at the thinned tition. Limitations on function imposed
portion, before it had been entirely cut by the inadequacy of any individual
through by the teeth. In no instance was prosthesis were compensated to a remark­
there evidence of balanced contact of the able degree by the adoption of modified
posterior teeth during incision, either in methods for incising the food. The extent
the studies of natural dentition or of care­ of modification depended largely on the
fully balanced artificial dentition. Our ob­ degree of instability of the denture bases.
servations confirm the saying, “ Enter Cusp angulation had no apparent in­
bolus, exit balance.” fluence on the manner of incision since
even with 45 degree cusps on dentures
Incision with Artificial Dentition • Cine- set to fine articulator balance, there was
fluorographic studies were made of the no occlusal balance during incision. In
no case was there any evidence of occlusal
balance during incision as long as the
bases remained in place against the tis­
sues. The influence of the tongue as a
retaining factor was obvious, however.
The role of denture stabilization during
incision, heretofore attributed to occlusal
balance, may with much more validity be
credited to the supporting action of the
tongue arched against the posterior
palatal area of the denture.

Fig. 4 • Enlarged view of oscillating m ove- 12. Gysi, Alfred. Masticating efficiency in natural
tnent during incision and artificial teeth. D. Digest 21:69 Feb. 1915.
 JA N KELSO N — H O FFM A N — H ENDRO N . . . VO LUM E 46, APRIL 1953 • 381

....
f f
f f

Î
Chev/ing meat Chewing crisp apple
Full dentition—bite relatio.n normal Full dentition—marked overbite

Fig. 5 • Chewing cycles. D ots were traced from consecutive cinefluorographic sequences
(posteroanterior a sp ect). Line betw een each dot represents ¡ ¡ 1 5 second of time

M ASTICATION allowance should be made for the error

it might introduce, especially in the
Mastication was studied by: evaluation of the terminal stroke. Kurth
1. Critical repetitive observation of reports that, using stroboscopic photo­
projected cinefluorographic film in m o­ graphs,2 25 visual images per second were
tion. necessary for a clear picture of the direc­
tion of the mandibular movement.
2. Projecting, one at a time, the suc­
Cinefluorography alone proved inade­
cessive frames of cinefluorographic strips,
quate for the investigation of certain
and tracing the path of a lead shot that
aspects of mastication. Composite graph­
had been placed between the mandibular
ing of vertical movement and of tooth
central incisors just before taking the film.
contact during mastication, as described
3. Composite graphing of vertical mo­ in an earlier paragraph, yielded much
tion and occlusal contact as already de­ information. A composite graph of a
scribed. young woman with full natural dentition
eating an apple is shown in Figure 2.
Findings " Critical repetitive observation Tooth relationship was normal and the
of the projected moving cinefluorographic occlusion was checked for premature con­
film studies was made as a prelude to the tacts. The subject was asked to tap the
detailed analysis reported later. teeth lightly together and then to eat the
The path of travel of the mandible as apple. The tapping was for the purpose
evidenced by tracings of successive frames of ascertaining, as a control, the charac­
of cinefluorographic film strip taken from ter of the deflection made by the stylus
the posteroanterior aspect is shown in when tooth contact occurred (Fig. 2, D ).
Figure 5. Space between each shot repre­ The small deflections (Fig. 2, E) con­
sents a time lapse of 1/15 o f a second. ceivably made by leakage of electrical
This interval is an advantage in evaluat­ current through the apple and saliva
ing speed of travel during the stroke. It are easily distinguishable from those
is a disadvantage in following a con­ made by tooth contact. In some strokes,
tinuous path of travel, however, and as tooth contact was approached, the
382 • THE JO U R N A L OF THE A M E R IC A N DENTAL A SSO C IA TIO N

Discussion of Findings on Mastication '

The experimental findings during masti­
cation established the following charac­
teristics of the masticatory cycles
( “ masticatory cycles” is a descriptive term
used by Shanahan151).

1. The chewing strokes were not uni­

B form in the closeness of their approach to
occlusal contact. The first strokes into a
hard resistant bolus terminated far short
Fig. 6 • Enlarged view o f Figure 2, A showing of occlusal contact; succeeding strokes
oscillating m ovem ent during voluntary tapping approached occlusal contact more closely
o f teeth. A : Closing com pon ent o f masticatory
cycle. B : O pening com ponent of masticatory
as the bolus was softened and reduced in
cycle. C : Oscillating m ovem ent size.
2. The strokes slowed as they ap­
proached occlusal contact.
3. The more or less continuous up­
graph shows a series o f steps (Fig. 6) ward stroke often changed to a controlled
similar in character to that found during oscillating type of movement as tooth
incision (Fig. 4 ). Occurrence of the oscil­ contact became imminent. The nature
lating movement during rapid tapping and the significance of the movement is
(Fig. 2, A and 6) suggests that it might not established.
be part of an involuntary mechanism 4. A lateral movement of varying
designed to avoid any shock contact of range often was evident at the terminal
teeth. portion of the stroke. There is insufficient
Contrary to the impression that food data at the present time on which to base
usually is chewed inadequately in terms any determination of its nature or func­
of chewing strokes, 54 strokes were made tion. Whether it is a shearing action as
in the chewing of a large bite of apple. some have assumed7 or a natural phe­
That tooth contact during chewing did nomenon of the shift in direction as the
not occur, or was insignificant, is evi­ opening component of the chewing cycle
denced by the absence of a typical tooth- is approached, or whether it is a combina­
contact deviation on the graph. The tion of both, is not known. Since the
characteristic contact deviation (Fig. lateral movement was equally or more
2, D ) , absent during chewing, appeared evident in those initial strokes of masti­
in some instances at the first swallow, in cation that stopped far short of tooth
others only during the second or third contact, the assumption that they repre­
swallow. In those instances in which it sent a shearing movement directed by the
did not occur during the first swallow, inclined planes of the teeth7 is un­
a residual portion of food usually was warranted.
still between the teeth, even though the 5. Even allowing for the 1/15 second
main portion which had been manipu­ time lag indicated in Figure 5, there is a
lated away by the tongue had been swal­ noticeable lack of uniformity of the scope
lowed. The residual food was then and direction of the terminal lateral
chewed further for a limited number of movements. The lack of uniformity would
strokes and a second swallow occurred.
Sometimes food still remained in the
mouth, and further chewing and a third
13. Shanahan, T. E. J. Dental p h y sio lo g y for dentures.
swallow was evident. J. Pros. Den. 2:3 Ja n . 1952.
 JA N KELSO N — H O FFM A N — HENDRON . . . VO LUM E 46, APRIL 1953 • 383

seem to preclude the assumption that patient’s habitual muscular pattern of opening
this part of the cycle was guided by cuspal and lateral movement.

inclination. Chewing of food was not involved. In

6. No regular pattern of the chewing justice to this excellent work it must be
stroke was found. Each stroke and each noted that it was not presented as a study
part of the stroke was essentially adaptive of actual function, but as an illustration
to the character of the food being chewed. of the difference between the stroke and
Furthermore, the character of the food the glide. The findings are valid and well
was in a continuous state of change as supported. They do not conflict with our
the mandibular teeth closed into it. The findings because they are not descriptive
act o f chewing was influenced by the of the same act.
constantly changing consistency, shape, Other findings, which at first glance
and size of the food, by its taste and even may seem contradictory to those given
by the state of the subject’s emotions.14 here, were recently reported by M cLean.7
He states that the investigation is o f a
7. The chewing stroke blended into subject chewing Dentyne chewing gum
the opening part of the cycle at various under instruction to “ chew it hard.” Since
levels short of tooth contact. It was ap­ the function of chewing is to prepare food
parent that food was between the teeth for swallowing, the chewing of Dentyne
at all times during chewing, tooth contact chewing gum is not functional. Further­
being negligible and nonfunctional except more, this substance has few of the
as a tactile warning to terminate the characteristics of food while it is being
stroke. chewed— it does not change volume, its
8. During the opening component of consistency is not affected by the chewing
each chewing cycle the cheeks and the stroke or by ensalivation. The instruc­
tongue maneuvered the bolus into place tion to “ chew hard into soft gum” is a
between the teeth while the mandible directive to the subject to consciously per­
dropped into position for the beginning of form the act in a specified way. The find­
the next chewing stroke. ings as reported are valid for the chewing
o f gum, with specific instruction as to
Even though it might seem that these the manner of chewing. Again, they do
findings are incompatible with those of not conflict with our findings because
other investigators, they do not detract they are not descriptive of the same acts.
from the validity of previous reports.2' 4,7 Boswell’s4 concept that the cycles have
Important differences in the conditions their termini at centric occlusion is based
o f the various experiments preclude any on findings recorded, during the chewing
likelihood that the investigators were re­ of various foods, by an ingenious appara­
porting on the same acts. Our report tus held in place by an arrangement of
deals with a description of action ob­ straps around the subject’s chin and head.
served during the uninhibited masticatory The difference in findings could be ac­
function of numerous subjects. Kurth,2’ 3 counted for by the presence of this device.
who has contributed much to this field Boswell’s report deals with the per­
o f investigation, reports on movement formance o f subjects wearing this device
made by a subject who during chewing; our report deals with the
performance of subjects who were not
. . . was first instructed to make free move­
ments of the mandible to the right and left, wearing this device during chewing.
and to protrude, without using the opening
component. . . . Then the patient was told to
describe a functional stroke of mastication, the 14. O 'R o u r k e , J. T. S ig n if ic a n c e o f t e s tin g f o r b it in g
direction of which was determined by the st re n g t h . J . A . D . A . 38:627 M a y 1949.
384 • THE JO U R N A L O F THE A M E R IC A N DENTAL A SSO C IA T IO N

Again, the findings do not conflict be­ Shown clearly in Figure 2 is the decisive
cause they are not descriptive of acts per­ contact during deglutition, in contrast to
formed under the same conditions. the lack of contact during chewing. In­
deed, it cannot be stressed too forcefully
T H E “ G L ID E ” (N O N M A S T IC A T O R Y that it was only during the act of degluti­
g r in d in g ) tion that functional contact of opposing
teeth was demonstrated.
Cinefluorographic Findings ' Our find­
ings corroborate those of Kurth2’ 3 in that Centric Occlusion During Deglutition ’
we found that the movement of the Rushmer13 reports that
structures of the stomatognathic system
Efficient deglutition depends on the plasticity
during the “ glide” bore no resemblance to and mobility o f the tongue. Conform ation of
the movements occurring during the chew­ the superior lingual surface to the palate forms
ing of food. This observation applies to an air-tight seal w hich separates the anterior
oral cavity from the oropharynx.
the action of the teeth, condyles, palate,
tongue and hyoid bone. Their relative This conformation of the tongue to the
quiescence in the “ glide” compared to palate occurred consistently in the cine­
the vigorous movements in chewing was fluorographic sequences o f deglutition.
especially noticeable. At no time during Very consistent, too, was the forceful,
mastication were we able to detect evi­ piston-like thrust of the tongue as it pro­
dence of the “ glide.” pelled the bolus into the oropharynx. In
short, when swallowing, the scene of ac­
D E G L U T IT IO N tion shifted energetically posteriorly to­
ward the pharynx. Forcible retrusion to
Occurrence and Frequency of Occlusal reach the site o f its work, and forcible
Contact of Teeth ' Shown clearly in the retrusion to accomplish that work of
oscillograph recording (Fig. 2) is the de­ sealing and of propulsion, characterized
cisive contact of teeth during deglutition. tongue action during deglutition. The
In the cinefluorographic studies also, vigorous retrusion of the tongue (Fig. 7)
closure of the mandible against the explains why the mandible was inevitably
maxilla during deglutition was consist­ carried into maximum retrusion during
ently evident. The physiologic necessity involuntary deglutition whenever the
for the mandible to be “ forcibly anchored path of closure was free of occlusal inter­
in the occlusive position” 15 became ap­ ference and clarifies the common observa­
parent when the extremely forceful con­ tion that in those cases where the
tractions and thrust of the tongue and mandible is prevented by cuspal inter­
suprahyoid muscles were observed. The ference from attaining centric occlusion,
contraction of these muscles, which have it goes to that position after the inter­
their origin in the mandible, plays a de­ ference is removed.
cisive role in the act of deglutition. Only during deglutition does tooth
Stabilization of the mandible against the contact occur as a functional act. The
maxilla allows these muscles to function forceful contractions and propulsive
with the utmost efficiency. No phase of thrusts of muscle groups which have their
the chewing of food can be accomplished origin in the mandible necessitate that
with the teeth in contact because when
the teeth are in contact no food is be­
tween them.16 On the other hand, de­ 15. R u sh m e r, R. F., a n d H e n d r o n , J . A . T he a c t o f
d e g lu t it io n : a c in e f l u o r o g r a p h i c st u d y . J . A p p l . P h y sio l.
glutition is performed most efficiently 3:622 A p r i l 1951.
with the teeth in contact, acting as an 16. Sh a w , D . M . F o rm a n d fu n c tio n in ^ te e th , a n d a
r a t io n a l u n if y in g p r in c ip l e a p p l i e d t o in t e r p r e t a tio n .
anchor for the functioning muscles. In t e r n a t. J. O r t h o d o n t . 10:703 N o v . 1924.
 JA N KELSO N — H O FFM A N — H EN DRO N . . . VO LUM E 46, APRIL 1953 • 385

I I Tongue at r e s t

E x c u r s i o n o f the t o n g u e during
deglutition

V7sI P o l a t e position d u r i n g deglutition

Fig. 7 • D irection and range of m ovem ent of tongue during deglutition

the mandible be anchored preferably minute forced oscillations during incision

against the maxilla. Centric occlusion and mastication is reported for the first
provides this anchorage in the most favor­ time. The nature of these movements and
able position for action of the tongue their significance is speculative. Subjects
during deglutition. This confirms the al­ with inadequate denture prostheses com ­
most universal clinical observation of the pensated for the inadequacy during in­
importance of centric occlusion. cision by pushing the food by hand
against the maxillary teeth. The man­
SU M M A R Y AND CONCLUSION dibular teeth did not participate in the
act as cutters. In no case was there any
Cinefluorographic and other investiga­ evidence of tooth balance during incision,
tions led to the following conclusions : and tooth balance had no part in the
Incision is not a simple act of teeth stabilization of the maxillary dentures.
cutting through food until it is severed. The dentures were stabilized by the
It is a coordinated effort by hand and tongue.
arm, by teeth, and by head, neck and Masticatory cycles are described. The
shoulders. Contact of teeth seldom occurs cyclic strokes were adaptive to the food
during the act because the food tears off being chewed and exhibited no regular
at the thinned portion before it is cut pattern. The findings indicate that food
entirely through. The character of the is between the teeth at all times during
food being incised greatly influences the chewing, tooth contact being negligible
nature of the act. The occurrence of and nonfunctional except as a tactile
386 • THE JO U R N A L OF THE A M E R IC A N DENTAL A SSO C IA T IO N

warning to terminate the stroke. The few balance of teeth in eccentric positions is a
light incidental contacts found during physiologic necessity, or that lack of
chewing seem to be the part of the stroke eccentric balance is less conducive to
that “ overshot the mark.” masticatory function.17 The voluminous
The evidence strongly suggests that literature on occlusion furnishes little ex­
centric occlusion is the only tooth contact perimental evidence on this question.
of any significance that occurs during
stomatognathic function. Evidence of ec­
centric tooth balance during eating was 17. B u rg e ss , J. K. D is c u s s io n o f F. W . F r a h m ’s In c is a l
q u i d a n c e — its in flu e n c e in c o m p e n s a t io n a n d b a la n c e .
not found. There was no evidence that J . A . D . A . 13:782 J u n e 1926.

Space maintenance for children

Norman H. Olsen, D.D.S., Chicago

The problem of space maintenance for growth center of the mandible is in the
children involves not only a special hyaline cartilage of the condyle. There
mechanical skill but also a thorough are four sutures of prime importance in
grounding in the underlying biological the growth of the maxilla; these sutures
principles of changing dentition. A knowl­ are parallel to each other and cause a
edge of growth and development is forward and downward growth of the
essential for diagnosis and treatment in maxilla.
cases of premature loss o f deciduous den­ In the mandibular condyles, there is a
tition. In view of the fact that the func­ proliferation and a replacement of the
tion of the deciduous dentition1 is to hyaline cartilage by bone. The new bone
provide mastication as well as to main­ contributes to an increase in the over­
tain the line of occlusion and space for all length of the mandible as well as in
the permanent teeth, it is apparent that the height of the mandibular ramus. The
any break in natural development may height of thè mandibular body is de­
require the dentist’s intervention to re­ pendent on the apposition of bone on
store nature’ s balance. the free alveolar surface.
In cases of anodontia although the
G R O W TH AND DEVELOPMENT

In describing the growth of the facial D e p a rtm e n t of p e d o d o n t ic s , N o rth w e ste rn U n iv e rs it y

D e n ta l S c h o o l.
skeleton, Sicher2 differentiates the growth 1. K o p e l, H . M . T he s p a c e m a in t e n a n c e p r o b le m in
the p r im a r y d e n t it io n . J . D e n . C h i ld r e n 17:21 3 r d q u a r t.
of the maxilla from that of the mandible. 1950.
The maxilla depends on sutural growth 2. W e in m a n n , J o s e p h P., a n d S ic h e r , H a r r y . B on e
a n d b o n e s: f u n d a m e n t a ls o f b o n e b io lo g y . St. L ou is,
for its development, whereas the main C . V. M o s b y C o ., 1947.