Loyola University Chicago Loyola University Chicago

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Master's Theses Theses and Dissertations

1976

The Influence of Rest Position of the Hyoid Bone upon The Influence of Rest Position of the Hyoid Bone upon

Neuromusculature Adaptation to Forced Posterior Displacement Neuromusculature Adaptation to Forced Posterior Displacement

of the Tongue of the Tongue

Kent B. Augustson Loyola University Chicago

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Recommended Citation Recommended Citation Augustson, Kent B., "The Influence of Rest Position of the Hyoid Bone upon Neuromusculature Adaptation to Forced Posterior Displacement of the Tongue" (1976). Master's Theses. 2874. https://ecommons.luc.edu/luc_theses/2874

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This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License. Copyright © 1976 Kent B. Augustson

TIIE INFLUENCE OF REST POSITION OF THE HYOID BONE UPON NEUROMUSCULATURE

ADAPTATION TO FORCED POSTERIOR DISPLACEMENT OF THE TONGUE

by

Kent B. Augustson D.D.S.

A Thesis Submitted to the Faculty of the Graduate School of

Loyola University in Partial Fulfillment of

the Requirements for the Degree

of Master of Science

June

1976

' - . .. ·-, ! ~ ~ .. _., L •. .)C, '· ' _·:

DEDICATION

to Carolyn, my wife and inspiration

ii

ACKNOWLEDGMENTS

I would like to extend my thanks to Dr. Douglas C. Bowman, my

thesis advisor, for his guidance and continued interest in this study.

My appreciation also goes to Dr. Bernard Pawlowski and Dr. Joseph

Gowgiel, members of my thesis advisory board.

I wish to acknowledge Drs. Cuozzo and Gobeille, whose work in this

area preceeded mine.

I am indebted to Loyola University and Drs. Braun, Madonia, and

Toto for making my graduate education possible.

I fondly acknowledge my parents, whose example in thought and

action provides a continuing inspiration.

Most importantly, I wish to acknowledge my wife Carolyn, to whom

this work is dedicated. I thank her for her love and understanding

during her marriage to a student.

iii

VITA

The author, Kent Binns Augustson, is the son of Elmer Moritz

Augustson and Geraldine Binns Augustson. He was born March 23, 1948,

in Galesburg, Illinois.

His elementary and secondary educations were obtained in the

public schools of Galesburg, Illinois. He graduated from Galesburg

Senior High School in 1966. In the fall of 1966 he entered the

University of Kansas in Lawrence, Kansas, where he majored in

Comparative Physiology and Biochemistry. He received the degree of

Bachelor of Arts in 1970. He attended Loyola University, School of

Dentistry from 1970 to 1974, when he received the degree Doctor of

Dental Surgery. Remaining at Loyola, in 1974 he began his studies

i~ the Orthodontic Certificate and Oral Biology Masters Programs.

iv

TABLE OF CONTENTS

ACKNOWLEDGMENTS

VITA

LIST OF TABLES •

LIST OF ILLUSTRATIONS

INTRODUCTION AND STATEMENT OF PROBLEM

REVIEI.J OF LITERATURE

Deglutition • • • • . • • • • • • • Hyoid Bone • • • • • . • • • Cinefluorography • • • • • • Myometrics • • • • •

METHODS AND MATERIALS

Selection of Subjects • • • • • • • ••• General Procedure • • • . • • • • • • • • Tongue Crib Appliance Fabrication and Placement Cinefluorographic Equipment and Technique Cinefluorographic Analysis • • • • Myometric Equipment and Technique • • Myometric Analysis • • • • •

RESULTS . . . ' . . . . . . . . DISCUSSION . . . " . . . . . . SUMMARY AND CONCLUSIONS . . . BIBLIOGRAPHY • • • • • • . . . . . . . . .

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2

2 8

15 16

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21 22 22 25 26 27 29

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51

53

,...

Table

I.

II.

.LIST OF TABLES

Quantified Results • • • • • . . . . . . . . . . . Subjects Exhibiting Extremes in Mandibular Plane-to-Hyoid Distance

vi

. . . . . . . . . .

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34

LIST OF ILLUSTRATIONS

Figure

1. Tongue Crib Appliance . . . . . . . . . . . . . . . . . 2. Appliance Viewed from Above Demonstrating

Anterior-Posterior Position of Crib Portion

3. Frontal View of Appliance Demonstrating Inferior Projection of Crib Portion •••.•••••••

4. Lingual View of Appliance Demonstrating Extension of Acrylic Portion • • • .

5. Plate Position for Control Myometric

. . . . . . . .

Recording . . . . . . . . . . Plate Position for Experimental Myometric Recording • • • • • • . . . . . . . . . . . .

7. Hyoid Position Before and Aftet' Placement of Tongue Crib Appliance

a. Subjects J.S. and K.A.

b. Subjects J.E. and H.Z.

c. Subjects C.B. and C.E.

d. Subjects C.H. and K.H.

e. Subjects D.P. and D.H. . f. Subjects A. H. and C.H. • • 41 • • .. •

g. Subjects A. C. and D.G.

h. Subjects M.S. and M.P. . . i. Subjects S.G. and M.E.

j. Subjects O.M. and D.T.

k. Subjects B.M. and S.N. . . . . vii

. . .

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INTRODUCTION AND STATEMENT OF PROBLEM

The purpose of this study was to determine whether the position

of the human hyoid bone, in its spatial relationship to the mandibular

plane, limits or influences the ability of the tongue neuromusculature

to adapt to forced posterior displacement.

In two previous studies at Loyola University, Cuozzo (1973) and

Gobeille (1974), the hyoid position did seem to influence tongue accom­

modation. It was hypothesized that subjects with hyoids positioned

near the mandible have greater potential for tongue accomodation than

subjects presenting hyoids positioned further from the mandible.

This study was designed to test the hypothesis. Two groups of

subjects were chosen for the work. One group was comprised of girls

with the mandibular plane-to-hyoid distance relatively long. The other

group was comprised of girls with the mandibular plane-to-hyoid distance

relatively short. Tongue crib appliances were utilized to displace the

tongue posteriorly. With cinefluorographic and myometric techniques,

adaptive potential of the two groups was compared.

1

REVIEW OF THE LITERATURE

Deglutition

Magendie (1822) divided the act of swallowing into three stages.

Even today, Magendie's Theory of Constant Propulsion remains basically

correct, current studies with cinefluorography notwithstanding.

The three classic stages of swallowing are: (1) oral, (2) pharyn­

geal and (3) esophageal. The oral stage is voluntary and conscious, the

pharyngeal involuntary, but still conscious, and the esophageal both in­

voluntary and unconscious.

The oral or preparatory stage begins as the tongue collects the

substance to be swallowed and forms the bolus. The bolus is contained

in a cupped depression on the dorsal surface of the tongue. The bolus,

at this point, is circumscribed by a peripheral seal. Anteriorly, the

tip of the tongue is positioned against the palatal mucosa behind the

anterior teeth. The tongue seals laterally against the buccal teeth and

adjacent palatal mucosa. Posteriorly, the seal is formed by the tensor­

depressed soft palate and the faucial pillars against the pharyngeal

portion of the tongue.

Passage of the bolus into the oral pharynx is accomplished with two

different actions. First, the lumen expands making room for the bolus

to pass. Then the lumen narrows and closes behind the bolus, propelling

it into the oral pharynx. Thus, the pharyngeal stage is begun by eleva­

tion of the soft palate, relaxation of the faucial pillars, and depres-

2

sian and grooving of the posterior tongue. Closure of the lumen behind

the bolus is accomplished by pressure of the dorsum of the tongue on the

hard palate and then on the soft palate. The soft palate is carried

down by contraction of the faucial pillars. Then it is carried forward

to oppose the tongue by contraction of the superior and middle constric­

tors of the pharynx. It has been noted in the literature that the ini­

tial elevation of the soft palate to oppose the posterior pharyngeal

3

wall effectively seals against nasal leakage. Ardran (1954) likened

bolus propulsion to toothpaste being squeezed from a tube. Ramsey et al.,

(1955) calls the progressive narrowing and obliteration of the lumen

behind the bolus a "stripping wave." The further closing of the lumen

is affected by the constrictor muscles acting against the base of the

tongue. As the bolus passes through the laryngeal pharynx there is a

characteristic vigorous upward movement of the larynx and trachea, laryn­

geal pharynx, hypopharynx, and upper esophagus. There is a concomitant

upward and forward movement of the hyoid. During the elevation of the

above mentioned structures, the true and false vocal folds are reflexly

approximated. Thus, the laryngeal additus is protected against bolus

penetration. The downward tilting of the epiglottis during this stage

tends to streamline the lumen and to some extent secondarily protect the

laryngeal additus. As the bolus reaches the hypopharyngeal constrictor

(cricopharyngeus) the sphincter is relaxed and the bolus enters the

esophagus.

Ramsey et al., (1955) stated that, with the exception of a few

reflex relationships, both the timing and order of the swallowing events

vary considerably in different individuals. They also vary in the same

individual under different conditions. He further stated that there are

persons who by training or habit vary markedly from the usual mechanism.

During the last twenty years the literature has been filled with studies

of deglutition. There has been a great deal written on these variations

to which Ramsey refers - tongue thrust swallow being the most controver­

sial.

Straub (1960) professed these criteria for a normal swallow: (1)

teeth firmly together, (2) muscles of facial expression relaxed, and (3)

tongue remaining within the confines of the oral cavity. Conversely,

Straub felt that the abnormal swallow was hallmarked by a lack of com­

plete tooth contact, protrusion of the tongue between the teeth at some

point, and tenseness in the perioral musculature. He felt that improper

bottle feeding was prime in the etiology of the tongue thrust swallow.

Straub stated that the abnormal swallowing habit usually produces an

open bite, and is capable of causing many "serious malocclusions." He

advocated function dictating form.

Rosenblum (1963) studied orofacial muscle activity during degluti­

tion in twenty subjects with normal occlusions. A motion picture tech­

nique was utilized. Analysis of the films showed that perioral activity

occurred in subjects with normal dentitions more than 50% of the time.

Wildman et al., (1964) studied fifty-two ten year old children, di­

vided equally into normal and tongue thrust swallowers. Specifically,

4

static tongue posture and oral coordination of the two groups were in­

vestigated. There was "no significant difference ••. found between the

two groups in either tongue carriage or repetitive ability."

The classical description of the clinically normal swallow came

under further question. Hedges et al., (1965) studied twelve to four­

teen year old children with excellent occlusions and no speech problems.

These children demonstrated two distinct swallowing patterns: one with

teeth together and one with teeth apart. As a result, it was suggested

that "the term 'acceptable' be substituted for 'normal' as a more prac­

tical and a more inclusive designation," when describing swallowing

patterns.

Cleall (1965) studied deglutition in adolescents divided into three

groups: normal - with excellent occlusion, Class II Division I malocclu­

sions, and a tongue thrust group. He found variations from the classic

normal swallow in the group with excellent occlusions. Cleall stated

that 20% of the normal group exhibited no lip closure during swallowing,

11% protruded the tongue tip beyond the incisors, and 40% made no molar

contact. He concluded, "The concept of 'normal' swallowing in which the

teeth come into occlusion, the lips remain in repose, and the tongue re­

mains within the confines of the oral cavity is no longer tenable."

Cleall placed palatal cribs in the tongue thrust patients, thereby chang­

ing the local environment. From their ability to adapt, he surmised

that spontaneous correction of tongue thrust may result from orthodontic

correction - function adapting to form.

5

-Brauer and Holt (1965), after examining approximately two hundred

grade school and junior high school children, devised a tongue thrust

classification. The classification was based on deformities observed

rather than etiology. They intimated in their approach that function

was dictating form. Interestingly, two of the criteria in this study

for tongue thrust swallowing were perioral contraction and a lack of

tooth contact during the swallm-1.

A number of investigators concentrated on the tongue. Peat (1968)

stated that there are two postural positions of the tongue for each

individual. The first, an habitual position, exhibits tongue tip con­

tact with the incisor teeth and/or lips. It also exhibits dorsum tongue

contact with the soft palate and sometimes with the soft palate and the

hard palate together. The second, a relaxed postural position, presents

increased convexity of the dorsum and contact with only the soft palate.

Fishman (1969) studied postural and dimensional aspects of the

tongue in rest position and occlusion. He included three groups in his

study: normals, a malocclusion group, and a group of lispers. His

observations on the normal group concurred with Peat's observations.

Fishman concluded, "Similarities and differences between normal, speech

and malocclusion groups have demonstrated that form and function have

some direct relationships to abnormal tongue posture and movement."

Harvold (1968) discussed animal experiments in which the dentition

exhibited sequellae when certain characteristics of the tongue (i.e.

size or position) were changed.

6

7

Cleall and Milne (1970) studied the posture and function of the

oropharyngeal structures during the period of mixed dentition. The

authors reported the oropharyngeal structures revealed a marked ability

to adapt to changes in the local dental environment. Specifically, the

forward position of the tongue was noted during the transition between

deciduous incisor loss and permanent incisor eruption.

Hanson et al., (1970) studied twenty-two factors in 193 subjects

and found only two "to be functionally associated with tongue-thrust

with any meaningful consistency. They are enlarged tonsils and lingual •

cross-bite." He contended that enlarged tonsils contribute to habitual

forward carriage of the tongue; and lingual cross-bite contributes by

forcing a narrowing and elongation of the tongue.

Subtelny (1970) observed swallowing behavior in ten normal subjects

and in thirty with malocclusions. He found appreciable differences in

tongue-tip function with differences in contiguous dentoskeletal form.

The interpretation was that the tongue was functionally adapting to the

specific anterior oral environment to achieve a seal during swallowing.

When the tongue-tip had adapted, the basic swallowing pattern was the

same in all the subjects. He concluded that the protrusive tongue activ-

ity could be a functional adaptation to its environment.

Subtelny (1973) reaffirmed his advocacy of form dictating function.

However, he mentions three factors which seem to contraindicate ortho-

dontic treatment and successful adaptation: abnormal skeletal relation-

ships, neurologic impairment in the control of orofacial muscle function,

- 8

and abnormal tongue size. Subtelny summarizes, "When form is modified

by orthodontic and/or surgical procedures within the anatomical and

physiologic limitations of the patient and within the reference of an­

ticipated changes incident to growth and development, stable adjustments

in occlusion and favorable adaptations in orofacial muscle activity may

be anticipated."

Hanson et al., (1973) contended that more progress would be made

if researchers paid less attention to perpetuating the dichotomy between

form and function. Rather, he felt, researchers should consider more

seriously the possible reciprocation between form and function. He

pointed out that his research indicated crowding of the tongue, whether

it be a narrow maxillary arch, enlarged tonsils, or the presence of an

intruding thumb, might well promote a tongue-thrust habit. Hanson stated

that conversely, myometric research makes it difficult to avoid the con­

clusion that the tongue does have the strength and persistence to cause

malocclusion.

Hyoid Bone

"The hyoid bone is shaped like a horseshoe, and is suspended from

the tips of the styloid processes of the temporal bones by the stylohyoid

ligaments.", Gray (1959). The bone is comprised of a body and paired

greater and lesser cornua.

Embryologically, according to Orban (1966), the hyoid has its ori­

gins from the second and third branchial arches. The upper median part

of the body and the lesser cornua are derived from the second arch. While

The greater cornua and the majority of the body come from the third

arch.

The body of the hyoid is quadrilateral in form. It gives origin

to the Hyoglossus muscle. Insertions for the Geniohyoid, Mylohyoid,

Sternohyoid, and Omohyoid muscles are found on the body.

The greater cornua project back from the lateral borders of the

body. To the end of each is fixed the lateral hyothyroid ligament. The

greater cornua give origin to the Hyoglossus and Constrictor pharyngis

medius muscles. While the Thyrohyoid and Stylohyoid muscles insert in

the same.

The lesser cornua are small conical eminences found at the junction

between the greater cornua and the body. The attachment to the stylo­

hyoid ligament is at the apex of each cornua. The Chondroglossus muscle

originates from the medial base.

By these attachments the hyoid bone is connected to and influenced

by: (1) the tongue, (2) the mandible, (3) the base of the skull, (4) the

sternum, (5) the scapula, (6) the thyroid cartilage, and (7) the pharnyx.

Sicher (1970) refers to the hyoid as the "skeleton of the tongue."

With this in mind, a brief discussion of tongue musculature is apropos.

The tongue musculature is divided into extrinsic and intrinsic groups.

The extrinsic muscles are the Genioglossus, the Hyoglossus, the Chondro­

glossus (sometimes described as part of the Hyoglossus), and the Stylo­

glossus. The intrinsic group is comprised of the Longitudinalis superi­

or, the Longitudinalis inferior, the Transversus, and the Verticalis.

9

10

The Genioglossi can act to move the tongue forward, backward, or down­

ward. The Hyoglossi, of particular interest in this study, depress the

tongue and draw its sides down. The Styloglossi draw the tongue upward

and backward. The intrinsic muscles are mainly concerned with changing

the shape of the tongue, i.e. shortening, narrowing, and curving actions.

In a cephalometric study of mandibular movements, Thompson (1941)

reported that movements of the mandible influenced hyoid position. He

noted that the hyoid moved only slightly posteriorly during the opening

rotation of the mandible.

Mainland (1945) stated that the hyoid acts as a platform. By fixing

one set of muscles, the platform is stabilized such that another set of

muscles can work from it.

Correlating the movements of the head and the hyoid, Wood (1956),

found that when the head is in dorsiflexion the hyoid is elevated. When

the head is in ventriflexion, however, the hyoid is directed downward.

Smith (1956) showed that the hyoid moves forward and slightly up­

ward as the mandible moves into protrusive position. On maximum opening

of the mandible, downward and backward hyoid movement was pointed out.

Hyoid position in Class I, II, and III malocclusions was observed

by Grant (1959). He found, from a representative cephalometric film of

each subject, the hyoid position to be constant. Grant stated that mus­

culature, not the occlusion of the teeth, determines hyoid position.

Shelton et al., (1960) studied cinefluorographically, tongue, hyoid

and laryngeal displacement during swallowing. Three phases of displace-

- 11

ment were described. Phase 1 "included simultaneous cephalad displace­

ment of the hyoid, elevation of the larynx and usually a dorsad movement

of the pharyngeal portion of the tongue." Hyoid movement here was some­

times slightly dorsad or ventrad, but always secondary to the cephalad

movement. Phase 2 "included simultaneous ventrad or ventrad and cepha­

lad displacement of the hyoid and elevation and closure of the larynx."

Here hyoid displacement ranged from directly ventrad to obliquely ceph­

aloventrad. Phase 3 "included simultaneous descent of the hyoid either

obliquely dorsad and caudad or dorsad and caudad and then more directly

caudad." There was also ventrad movement of the pharyngeal portion of

the tongue and descent and opening of the larynx.

Brodie (1961) called attention to the fact that the hyoid's role

as a functional part of the skeletal system has been a recent evolution­

ary development. He related the actions of the hyoid to maintenance of

an ainmy during mandibular movements.

Durzo and Brodie (1962) conducted a longitudinal cephalometric study

of five normal occlusions. They found the hyoid to be positioned supero­

inferiorly opposite the lower portion of the third and upper portion of

the fourth vertebrae. It was stated that position anteroposteriorly de­

pends on the relative length of the muscles running from the hyoid to

the base of the cranium and the mandibular symphysis. They stated that

during development the hyoid descends as cervical vertebrae grow and as

the posterior cranial base and mandible descend. But the relative posi­

tion of the hyoid is invariable.

In a study of 165 subjects, Bench (1963), found that the hyoid

gradually descends from a position opposite the lower half of the third

and the upper half of the fourth cervical vertebra (at age 3) to a posi­

tion opposite the fourth cervical vertabra (at adulthood).

Wildman (1964), in his cinefluorographic study of deglutition,

stated that since the hyoid bone serves as the "posterior pedestal" on

which the tongue is mounted, it is a particularly helpful structure to

study in relation to the swallowing act.

A cephalometric positional study of the hyoid bone was attempted

by Stepovich (1965). He stated that hyoid position could not be dupli­

cated from one cephalometric film to the next. He attributed the prob­

lem in duplicating the hyoid position from one film to the next to two

factors: (1) the hyoid is totally suspended by muscles and ligaments,

and (2) the hyoid cannot be easily related to a fixed point in the head,

which is itself unstable.

12

Sloan et al., (1967), in a study of comparative hyoid movement dur­

ing swallowing in Class I and Class II malocclusions, showed the antero­

posterior location of the hyoid was consistently found to be near the

anterior root of the pterygoid plates. He found that the Class I malo­

cclusions, although exhibiting no skeletal differences from the other

classes of malocclusion in the study, exhibited significantly lower and

more posterior hyoid locations (relative to the mandible). The Class II

malocclusions, conversely, showed higher and more forward hyoid positions.

The position of the hyoid bone and that of the mandible in retruded

---13

contact position, intercuspal position, and postural position in 144

persons were studied by means of cephalometric films by Ingervall et al.,

(1970). The following observations were made: (1) The position of the

hyoid bone varied less in superoinferior direction on repeated determin­

ations in the postural position of the mandible than the contact posi­

tions. (2) The hyoid moved downward and backward from intercuspal to

retruded contact position. (3) The postural position showed the hyoid

occupying a more superior position than in the intercuspal position.

Ingervall (1970), in a follow-up study, sought to determine whether

the size of hyoid movement concomitant with movement of the mandible be­

tween postural, intercuspal and retruded contact positions, varies with

facial and dental arch morphology. He found that if the height of the

face is small, the hyoid bone tends to move inferiorly on movement of

the lower jaw from intercuspal position to postural position. But if

the facial height is great, the hyoid bone will move superiorly.

A cinefluorographic technique was used by Milne and Cleall (1970),

to measure changes occurring in the posture and function of the oro­

pharyngeal structures during the transitional dentition stage. They

stated that the oropharyngeal structures demonstrated a marked ability

to adapt to changes in the local dental environment. It was pointed out

as being probable that the adaptive movements of the hyoid bone are limi­

ted to those which would not interfere with the maintenance of an ade­

quate airway.

Yip and Cleall (1971) conducted a cinefluorographic study of the

resting posture and the pattern of movement of the oronasopharyngeal

structures before and after surgical removal of both tonsils and ade­

noids on twenty-eight children. "The positions of the hyoid bone ap­

peared to be in a more upward and forward position both at rest and dur­

ing all the stages of swallowing after the operation."

In a later study, Ingervall et al., (1971) recorded the act of

deglutition cineradiographically to study the movements of the hyoid

bone and to clarify whether contact between the teeth occurs in inter­

cuspal or retruded contact position. It was confirmed that the hyoid

undergoes marked supero-anterior movement during the later part of the

act of swallowing and reaches its most supero-anterior position when

the bolus is in the lower part of the oropharynx. The pattern of hyoid

movement seemed independent of the position of the mandible during con­

tact. It even seemed to be independent of whether or not there was in

fact contact during swallowing.

14

Wickwire (1972) found that when the mandible is set back in Class

III correction, the tongue is carried lower in the mouth, as demonstrated

by a change in hyoid position.

Cuozzo and Bowman (1975) performed a study to determine the amount

of change in positioning of the hyoid bone during deglutition following

forced distal positioning of the tongue by a tongue crib. Ten female

subjects, ranging in age from nineteen to thirty years, were included.

They were Class I normal occlusions. Cuozzo and Bowman judged accommo­

dation in terms of hyoid repositioning (determined from cinefluorographic

-films) and myometric results. They found a strong correlation between

initial hyoid position and the ability to adapt. From these results,

they hypothesized that individuals with hyoids held relatively close to

the mandibular plane can reposition the tongue posteriorly or inferior­

ly. Conversely, those with hyoid bones held relatively distant from

the mandibular plane would be expected to find such accommodation dif­

ficult due to encroachment on the airway space.

Gobeille (1974), in a follow-up of Cuozzo's work, studied ten open

bite, tongue-thrust patients. His method of study as well as his re­

sults were similar to Cuozzo's. Gobeille stated, "The hypothesis of

hyoid-mandibular plane distance was again born out."

Cinefluorography

Cinefluorography is the roentgen method for investigating function.

There have been numerous studies reporting various aspects of swallowing

behavior as revealed by cinefluorography.

15

Perhaps the first such investigators were Rushmer and Hendron (1951).

Referring to their study of deglutition, Saunders et al., (1951) stated,

" ••• the development of relatively high speed cineradiography offers the

most favorable opportunity of analyzing details of the mechanism and the

precise phase and sequence of the motions."

Sloan et al., (1964) stated that the cinefluorographic record pro­

vides these basic data: (1) motion of the structures, (2) variation in

their radiographic density, and (3) chronology of the changes occurring

during the functional cycle. In this study, Sloan establishes eight

basic steps necessary to the correlation of cephalometric analysis and

cinefluorographic craniopharyngeal films.

Cleall et al., (1966) in a cinefluorographic study of head posture

and its relationship to deglutition stated several characteristics of

cinefluorography. The greater degree of magnification in cinefluoro­

graphic equipment compared with the conventional cephalometric set-up

16

is due to a shorter x-ray source to patient distance and a larger patient

to image distance. Further, cinefluorographic film is such that while

the structures are plainly visible in motion, single frames are much

less clear than cephalometric radiographs.

Cinefluorography enables the researcher to view the previously in­

accessible oral cavity and its related pharyngeal complements. The

quantity of literature in the area is growing. The following studies,

mentioned within this literature review, utilized cinefluorography:

Ardran and Kemp (1954); Ramsey et al., (1955); Shelton et al., (1960);

Wildman et al.' (1964); Brauer and Holt (1965); Cleall (1965); Hedges

et al,, (1965); Sloan et al., (1967); Milne and Cleall (1970); Hanson

et al., (1970); Subtelny (1970); Ingervall (1971); Yip and Cleall (1971);

Cuozzo and Bowman (1975); and Gobeille (1974).

Myometrics

Tomes (1873) stated, "The agency of the lips and tongue is that

which determines the position of the teeth themselves." Since, there

has been much research in the area of determining quantitatively muscle

influence on the dentition.

17

Kydd (1956) studied maximum tongue force in a thirty year old eden-

tulous patient. Strain gauges were mounted on a mandibular denture base.

He found the maximum anterior force to be about 5 lb. and the maximum

lateral force in the second bicuspid region to be approximately 2.5 lb.

Muscle pressures in seven subjects with normal occlusion were in-

vestigated by Winders (1956). The results indicated an apparent im-

balance of forces exerted by the tongue and perioral musculature. The

tongue was found to exert greater force. In a later study, 'vinders

(1958) recorded buccal-lingual pressures in both Angle Class I and Class

II Division I subjects to determine muscle effect on tooth position.

He found that there was no statistically significant correlation between

the swallowing pressures and the anteroposterior position of the teeth.

He further stated, "During function, there is an imbalance of myometric

forces acting on the dentition - the tongue exerting a much greater force

than the perioral musculature." In still a later study, Winders (1962)

once again reaffirmed his theory that the tongue exerts a greater force

than the perioral musculature. He also noted greater lingual pressure

in tongue-thrust subjects. However, it was found that this swallowing

pattern can be superimposed on any occlusal pattern.

Comparing a group of tongue-thrusters to a group of normals, Kydd

and Neff (1964) found the former to swallow at a lower frequency. The

tongue-thrust subjects, however, exhibited twice the force for a longer

duration in swallowing. They concluded that the effective pressures were

similar.

18

Lear and Moorrees (1964), considering force per swallow, frequency

of swallow, and resting force, concluded that the force contribution

during deglutition, if converted to terms relating to continuous rather

than spasmodic function, is only 1/40 - 1/20 as great as was made by

resting forces.

The adaptability of labiolingual musculature was studied by McNulty

et al., (1967). Partial dentures were fabricated for three subjects re-

placing maxillary incisors. One partial denture was set up with the

incisors identical to the subject's original denture, the other with

the incisors positioned in a three millimeter protrusion. Muscle force

increased labially and decreased lingually initially. Within twenty-four

hours, however, the musculature had largely adapted.

Lear and Moorrees (1969) studied seven young men with normal occlu-

sions in an attempt to determine dentition stability and symmetry re-

lated to buccolingual muscle function. Only one of the seven subjects

exhibited a close counterbalance between buccal and lingual pressures in

both arches. They stated that their findings should not be construed

as either vindicating or confounding the concept of balance between

buccal and lingual forces.

Using pressure transducers embedded in plastic palatal appliances,

Proffit et al., (1969) observed linguopalatal pressure in a group of

five to eight year old children. No positive correlation between lateral

pressure and arch width was found. It was suggested, however, that lat-

eral pressure tends to decrease with increased intermolar width.

~ r '

I ,, i

19

Proffit and McGlone (1972) performed a study on nine children with

oral cavities showing a wide range of sizes. Functional tongue pres­

sures against the maxillary arch were measured. Correlations between

these oral activities and cavity size were small. It was suggested that

functional activities contribute only to a limited extent to oral cavity

growth compared to the lesser resting forces. The authors used the term

"semi-functional" matrix referring to this limited contribution of the

functional activities.

Brader (1972) studied Winders data and reaffirmed the concept of

equilibrium between the tongue and the perioral musculature. He hypoth­

esized that the radius of curvature of the dental arch influences the

stresses on it. This, he proposed, added to the resting buccolingual

pressures confirms the equilibrium statement.

Maximum perioral and tongue forces in both normal and malocclusions

were studied by Posen (1972). A significant relationship was shown to

exist between maximum strength and force of the lips and the final posi­

tion and angulation of the incisors. Conversely, there was strong evi­

dence that the role of the tongue on the same is minimal, except where

there is a perverted position of the tongue during function or rest.

Muscle pressures and tooth positions were compared in North American

whites and Australian aborigines by Proffit (1975). It was found that,

despite their expanded arches, there was no indication that expanding

tongue forces for the aborigines are even as great as in American sub­

jects. The restraining resting lip pressures, on the other hand, were

20

almost precisely the same in both groups. Proffit warned against "physi­

ologic reactance" (defined as alteration of the physiologic activity

being studied by the presence of instrumentation). He contended that

tongue activity can be altered as the tongue avoids the pressure trans­

ducers. Proffit concludes by stating that it appears the form of the

dental arch dictates the functional pattern of the tongue and lips to

a much greater extent than function alters form. He further states,

that to the extent to which function does alter form, resting pressures

seem more important than functional pressures.

METHODS AND MATERIALS

Selection of Subjects

Forty-seven adult females, judged to have good Class I occlusion,

were screened for this study. The screening process consisted of a

lateral cephalometric x-ray. From this cephalogram, the distance on

a perpendicular from the mandibular plane to the inferior-most point

on the body of the hyoid bone was measured. On this basis, two groups

of twelve were chosen for the study. One group was comprised of sub-

jects with mandibular plane-to-hyoid distances ranging from 16-19 mm.

The second group of subjects' mandibular plane-to-hyoid distances ranged

from 26-39 mm. A cinefluorographic sequence of each subject's normal

swallowing pattern was taken as part of the control data. As a result,

this original grouping of subjects, based on measurements taken from

~ateral cephalometric x-rays, was re-evaluated. Some of the mandibular

plane-to-hyoid measurements varied significantly from the cephalogram to

the cinefluorograph. It was determined that the hyoid rest position as

portrayed by the cinefluorograph was more accurate. Consequently, the

subjects were redistributed into three groups based upon their mandibular

plane-to-hyoid distances determined from cinefluorographic sequences:

(1) subjects with mandibular plane-to-hyoid distances of 24-32 mm., (2)

subjects with mandibular planes-to-hyoid distances of 19-24 mm., and (3)

subjects with mandibular plane-to-hyoid distances of 14-17 mm.

21

I

'I

22

General Procedure

For each subject the following control data was collected: (1) a

myometric recording, and (2) cinefluorographic sequences of normal

deglutition.

A tongue crib appliance was fabricated for each subject. The pur-

pose of the crib was to restrain the tongue posterior to its normal

position,

Experimental data was collected after the appliance had been in

place for 24 hours. The myometric recording and cinefluorographic se-

quence were repeated prior to crib removal.

Tongue Crib Appliance Fabrication and Placement

The appliance used in this study was modelled after that of Gobeille

(1974) ~ee Fig. 1). The crib superstructure was borne by a straight

length of .045 inch diameter orthodontic wire soldered at each end to

cuspid orthodontic bands. This wire spanned the palate approximately

15 mm. distal to the central incisors (See Fig. 2). The superstructure

consisted of: (1) a "U" shaped crib, and (2) an acrylic palate. Both

the "U" shaped crib portion and the acrylic portion were attached to a

length of .045 inch inside diameter orthodontic tubing which fitted over

the transoral .045 inch wire. This allowed the entire superstructure to

rotate around the transoral wire soldered to the cuspids.

The "U" shaped crib projected inferiorly from the tubing approxi-

mately 10 mm (See Fig, 3). When the subject was in occlusion, the crib

projected into the lingual aspect of the mandibular arch. It served to

Figure 1. Tongue Crib Appliance

Figure 2. Appliance Viewed from Above Demonstrating Anterior-Posterior Position of Crib Portion

23

Figure 3. Frontal View of Appliance Demonstrating Inferior Projection of Crib Portion

Figure 4. Lingual View of Appliance Demonstrating Extension of Acrylic Portion

24

prevent the tongue from slipping inferiorly and anteriorly during deglu­

tition.

The acrylic portion extended anteriorly to the cingula of the max­

illary incisors. Laterally it was cut away from the canines and pre­

molars. The portion at the posterior of the crib was trimmed to mimic

the lingual aspect of the incisor teeth and the anterior hard palate

(See Fig. 4) •

The crib design enabling the superstructure to rotate around the

transoral wire was an attempt to allow for near physiologic feedback

during deglutition. Anterior pressure exerted by the tongue was trans­

mitted to the incisors and anterior palate.

25

The appliance was cemented in each subject for a period of 24 hours.

Cinefluorographic Equipment and Technique

A Picker Cinefluorograph with a high image intensifying screen was

used for the deglutition film sequences. Mounted at one end of a "C"

arm was the x-ray head. The other end held the image amplifier with

camera and optical system. The "C" arm was adjustable in the vertical

dimension, capable of being locked in any position. A cephalostat was

attached to the "C" arm. The ear rod nearest the image amplifier was

stationary. This provided constant subject-to-film distance.

The subject \vas seated in a chair of fixed height. The head was

stabilized with the ear rods after asking the subject to "sit up as

straight as possible." Head position was further adjusted until the

Frankfort plane was parallel to the floor. An adjustable stand with a

26

horizontal arm was used to stabilize the chin in this position. The

height of the chin support was recorded for duplication on subsequent

sittings.

The subject was given 3-4 cc. of barium and instructed to swallow

on command. Two swallows were recorded per sitting, one with barium

and one with residual oral fluids, The sequence was shot at 60 frames

per second on 16 mm. Kodak Shellburst Film. The unit was set for 90

kvp, and 13m, Each subject received approximately .75 r. total ra-

diation.

Cinefluorographic Analysis

A Vanguard Motion Analyzer was utilized in viewing the film sequen-

ces, Viewing speed was variable from 5 to 30 frames per second. It

was also possible to view individual frames.

The following structures were traced viewing the control film:

(J} palate, (2) maxillary central incisor, (3) mandibular central in-

cisor, (4) lower border of mandible and mandibular symphysis, and (5)

the hyoid bone, A template was used for the incisors and the hyoid.

The hyoid template was made from a lateral cephalometric film taken of

each subject during screening. The hyoid was traced in three positions:

(1) rest position, (2) most posterior superior position, and (3) most

anterior superior position. The control tracing was then superimposed

on the experimental film sequence and the hyoid was again traced in three

positions.

Analysis was further accomplished by superimposing a grid on each

subject's tracing. The mandibular plane was used as the X axis. The

Y axis was constructed by bisecting the mandibular plane and dropping

a perpendicular at this point. This allowed quantitative analysis of

hyoid changes.

Myometric Equipment and Technique

The anterior component of tongue force during deglutition was meas­

ured using a Myograph C pressure transducer, manufactured by Narco-Bio

Systems. This transducer was capable of measuring in the range of

0-500 gm. The recordings of the transducer were registered by pen de­

flections on the graph paper of a polygraph. This instrument was a

Narco Physiograph.

27

A plate soldered to the end of a length of .014 inch diameter or­

thodontic wire was placed intraorally. This had soldered to it a length

of .045 inch diameter orthodontic wire which enabled the entire unit to

"couple" into a .045 inch inside diameter sheath at the end of an exten­

sion arm on the pressure transducer. The plate bearing unit was slipped

beneath the contact of the maxillary central incisors for the control

recording. The plate extended approximately 2 mm. distal to the incisive

papilla (See Fig. 5). For the experimental recording, the plate bearing

unit was threaded through a section of .045 inch inside diameter tubing

mounted on the crib. The plate extended approximately 2 mm. distally

from the appliance (See Fig. 6).

During myometric recording sessions, the subject's head was stabili­

zed with the head rest of a dental chair. Water was introduced with an

Figure 5. Plate Position for Control Myornetric Recording

Figure 6. Plate Position for Experimental Myometric Recording

28

I I

,

29

eye dropper, facilitating normal repetitive swallowing.

Myometric Analysis

Ten representative swallows were chosen from each recording. Cal-

ibration was accomplished by hanging standard weights from the myograph

at the end of each session. The myograph used was linear in its record-

~ng. The heights of pen deflection for the ten representative swallows

were averaged. This average height was then extrapolated to the height

pen deflection of a known weight to determine the force value in grams.

RESULTS

The results in their entirety are presented in Table 1. The data

includes: (1) subject's height, (2) vertical hyoid position at rest

(mandibular plane-to-hyoid distance in rom.) as determined from the lat-

eral cephalometric x-ray, (3) vertical hyoid position at rest (mandibu-

lar plane-to--hyoid distance in rom.) as determined from the control cine-

fluorographic sequence, (4) horizontal hyoid position at rest (mid-point

mandibular plane-to-hyoid in rom.) as determined from the control cine-

fluorograph, (5) vertical change in hyoid position (in rom.) after 24

hours with crib appliance in place, (6) horizontal change in hyoid posi-

tion (in rom.) after 24 hours with crib appliance in place, (7) anterior

tongue force (in gm.) prior to appliance placement, and (8) anterior

tongue force (in. gm.) after 24 hours with crib appliance in place.

Figure 7a-k demonstrates hyoid positioning before and after tongue

crib appliances were placed in each subject.

The total number of subjects was reduced from 24 to 22. This was

due to the loss of cinefluorographic data as a result of equipment fail-

ure. As previously mentioned, the remaining 22 subjects were placed in

three groups according to their mandibular plane-to-hyoid distances de-

termined from cinefluorographic sequences: (1) subjects with mandibular

plane-to-hyoid distances of 24-32 rom., (2) subjects with mandibular plane-

to~Hyoid distances of 19-24 rom., and (3) subjects with mandibular plane-

to~hyoid distances of 14-17 mm.

30

I I I

31

Group 1, with mandibular plane-to-hyoid distances ranging from

24-32 mm., generally did not exhibit hyoid repositioning in the infer-

!or-posterior direction. There was one exception. K.A. showed dramatic

inferior-posterior repositioning.

Group 2, with mandibular plane-to-hyoid distances ranging from

19-24 mm., exhibited diversity in hyoid response. Four subjects (K.H.,

D.P~, D.H., and C.M.) showed hyoid repositioning in the inferior-poster-

ior repositioning.

Group 3, with mandibular plane-to-hyoid distances ranging from

14-17 mm., generally exhibited inferior-posterior repositioning of the

hyoid. Two subjects (S.G. and D.T.) did not follow this pattern.

Table 2 depicts the subjects in Groups 1 and 3. These subjects

exhibited the sample's extremes in terms of hyoid rest position. T

tests were run to determine whether hyoid repositioning in either the

vertical or horizontal dimension was statistically significant. The

difference between the two groups' vertical repositioning was calculated

to be significant at the .05 level, (T value of 2.491). The horizontal

repositioning difference was not found to be significant at the .05 level.

It fell in the probability range of .20>P>.l0, (T value of 1.531).

Myometric results were varied throughout the three groups. Hyoid

repositioning in the inferior-posterior dimension was deemed adaptation

to the posterior tongue displacement. Myometric values in some cases

correlated with such adaptive hyoid repositioning or lack thereof, and

in other cases seemed independent of the hyoid reaction.

I

II I , I,

! I

32

Seven subjects (K.H., D.H., M.S., M.P., M.E., O.M., and S.N.) ex-

hibited what were appraised as being adaptive anterior tongue force

levels coinciding with their adaptive hyoid repositioning. Three more

subjects (J.E., C.B., and D.T.) exhibited increased force values com-

mensurate with their lack of hyoid adaptation.

Conversely, three subjects (D.P., C.M., and D.G.) had adaptive

hyoid changes but adaptation was not shown myometrically. And, six sub-

jects (J.S., H.Z., C.E., A.H., A.C., and S.G.) did not exhibit adaptive

hyoid repositioning, yet myometrically anterior tongue force levels in-

dicated adaptation.

Finally, three subjects (K.A., C.H., and B.M.) showed anterior

tongue force levels that made adaptation judgment in terms of myometrics

difficult.

SUBJECT

Group 1

J.S. K.A. J.E. H. Z. C.B. C,E. C,H.

Group 3

D.G. M.S. M.P. S.G. M.E. O.M. D.T. B.M. S.N.

TABLE II

SUBJECTS EXHIBITING EXTREMES IN MANDIBULAR PLANE-TO-HYOID DISTANCE

Hyoid to GoGn in nun.

32 29 28 26 25 25 24

17 17 17 17 16 15 15 14 14

Hyoid to Mid-Mand Corpus in nnn.

19 4 10 10 34 2 11

10 14 19 25. 13 8 23 12 11

Vert. Change in nun.

+5 -11 +4 -4 +2 +1 +3

-7 -5 -8 +1 -11 -5 -1 +2 -6

Horiz. Change in nun.

+2 -2 +2 +10 +3 -1

0

+1 -2 -3 -1 +1 +4 +1 -6 -4

34

35 Figure 7a

KA

Control Q Experimental ~

j

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36 Figure 7b

HZ

Control 0 Experimental ~

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Figure 7c

Control 0 Experimental ~

37

CB

CE

~~~~~~11! 11

1':"11 ~ ' II

r

Figure 7d

1,11111111

38 1

111''11 1,,11,

I 1

1

111111

llill11.1!

'II~ !1~1 r:

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CH

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11111

:1111il

II ~ II

11!111

,rrll11

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l

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1 11~ '11.!1111

1"1111[1

ill~ 1

1!111ilrl1

111

111]11

· Ill I 111 !:

'I :1

KH i!i ! 1',11111

·1111

11'1

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ll,ill

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1

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l,il,'"' 1','1'

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Control 0 '/'I I

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, Ill

Experimental ~ 1:1

' 1 39 I Figure 7e

DP

DH

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40 Figure 7f

AH

CM

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Figure 7g

AC

DG

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41

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r Figure 7h

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42

MS

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SG

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44

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45

BM

SN

r DISCUSSION

As mentioned, the relative vertical position of the hyoid bone, re-

lated to the mandibular plane, varied considerably from the lateral

cephalometric x-ray to the control cinefluorographic sequence. The

lateral cephalometric x-ray provides a static reading on hyoid position.

This poses a problem. The hyoid is a "floating bone", completely sup-

ported by muscle and ligamentous attachments. Cinefluorographic data

however, is dynamic. It allows the viewer to visualize physiologic

functional patterns. As a result, hyoid rest position can, in the au-

thor's opinion, be more accurately determined from cinefluorographic

sequences. Ingervall (1970) pointed out significant variations in hyoid

position between intercuspal and postural positions of the mandible. He

further found lateral cephalometric x-rays taken with the mandible in

postural position allowed reproducable hyoid positioning. The cephalo-

grams taken in this study for original screening purposes were shot in

the traditional intercuspal position. This could explain the variance

between the cephalometric and cinefluorographic hyoid rest position

noted. For the clinician to utilize lateral cephalometric x-rays to

monitor hyoid rest position, they should be taken with the mandible in

postural position.

For purposes of this study, repositioning of the hyoid bone in an

inferior-posterior direction was deemed adaptation. Two of the three

main sets of extrinsic tongue muscles, the hyoglossi and the genioglossi,

46

I ,li

r have attachments on the hyoid bone. Any repositioning of the hyoid bone

in an inferior-posterior direction accommodates posterior displacement

of the tongue.

47

The lack of adaptive repositioning of the hyoid bone in group 1 was

judged to be a result of the initial hyoid position. These subjects pre­

sented with hyoid positions relatively distant from the mandibular plane.

Hyoid repositioning in an inferior-posterior direction could have en­

croached on air-way space. Cuozzo (1975) mentioned this possibility in

explaining similar results. Brodie (1961) noted specifically the an­

terior suprahyoids (mylohyoids and geniohyoids) as holding the larynx

forward to insure patency of the air-\vay.

One subject in group 1 (K.A.) did show adaptive hyoid repositioning

despite the initial mandibular plane-to-hyoid distance of 29 mm. The

initial horizontal position of the hyoid bone provided a possible ex­

planation. The hyoid was positioned near the middle of the corpus. Only

one other subject in this group (C.E.) exhibited similar anterior hyoid

rest position. This forward carriage of the hyoid bone could account for

K.A.'s ability to show hyoid accommodation without embarrassing the air­

way. C.E. exhibited myometric adaptation. Possibly the adaptive poten­

tial of her intrinsic tongue musculature made hyoid repositioning un­

necessary.

Group 2 subjects had mandibular plane-to-hyoid distances ranging

from 19-24 mm. K.H., with a distance of 24 mm., was placed in this group

even though C.H. was placed in group 1. It was determined that while a

r mandibular plane-to-hyoid distance of 24 mm. is relatively long, it was

judged to be in the average or medium range for someone of K.H. 's stat­

ure. It should be noted that K.H. showed adaptive hyoid repositioning,

which supports this judgement.

48

The remaining subjects in group 2 showed varied hyoid response. As

alluded to above, to accurately predict hyoid adaptive potential overall

anatomic considerations, i.e. body size and structure, must be evaluated.

These factors become increasingly important when dealing with the middle

range of mandibular plane-to-hyoid distances. In such cases secondary

factors (if in fact they are only secondary) such as size of subject,

hyoid position in the horizontal dimension, and intrinsic tongue muscula­

ture adaptation become increasingly important determinants in adaption

patterns.

Group 3, with hyoids positioned relatively near the mandibular

plane, generally showed adaptive hyoid repositioning in the inferior­

posterior direction. It can be theorized that this hyoid stature allows

adaptation because the air-way space is not encroached upon by such ac­

commodation. It should be noted that the two exceptions in this group

(S.G. and D.T.) exhibited hyoid rest positions quite posterior relative

to the mandibular corpus. It is hypothesized that despite the relatively

high carriage of the hyoid, adaptation in an inferior-posterior direction

was limited due to the relative posterior position of the bone. From

this posterior position it is theorized that adaptive positional changes

might embarrass the air-way. The hyoid behavior of K.A. in group 1 and

r S.G. and D.T. mentioned here suggests the horizontal hyoid position may

be a significant determinant of hyoid adaptive potential.

49

In interpreting the statistical results, it should be stressed that

groups 1 and 3 were comprised of the sample extremes in terms of mandib­

ular plane-to-hyoid distance. The groups were compared to determine if

the vertical hyoid position had any statistical effect on the hyoid bone's

adaptive potential in the inferior-posterior direction. The T test run

on the changes in vertical dimension revealed that the two groups indeed

differed in their ability to move the hyoid inferiorly. This offers

statistical support for the theory first proposed by Cuozzo (1975). It

appears hyoid adaptive potential is influenced by its spatial relation­

ship to· the mandibular plane.

The horizontal adaptive changes were not significantly different

(.20>P>.lO), when the two groups were compared. When interpreting this

it must be kept in mind, however, that the subjects studied were grouped

on the basis of vertical hyoid position. Thus, only initial vertical

position's effect on horizontal repositioning was tested. This is not

to say that horizontal position is not a factor in hyoid adaptation.

It has been mentioned that myometric results were varied when re­

lated to adaptive changes in hyoid positioning. It must, however, be

remembered that hyoid repositioning is only one way in which the tongue

might adapt to forced posterior displacement. The intrinsic tongue mus­

culature plays a role. It was not monitered in this study. Nevertheless,

it is reasonable to assume that the intrinsic tongue musculature's own

adaptive potential accounts for some of the apparent discrepancy between

myometric and cinefluorographic results.

Also, there are inherrent difficulties in any myometric recording.

50

These must be realized. First, there is always the possibility of alter­

ing physiologic activity with the instrumentation used. Proffit (1975)

refers to this as "physiologic reactance". Secondly, it has been well

documented that there is a great deal of variability in the "normal"

swallowing pattern. The accuracy of myometric recordings as performed

in this study depended on the tongue tip placement against the recording

plate. There is the possibility that because of normal variation in

tongue position some subjects' anterior tongue force was only partially

captured at one or both recording sessions.

SUMMARY AND CONCLUSIONS

The purpose of this study was to determine whether the position of

the human hyoid bone, in its spatial relationship to the mandibular

plane, limits of influences the ability of the tongue musculature to

adapt to forced posterior displacement.

Twenty-two adult female subjects were included in the study. My­

ometric recordings and cinefluorographic sequences of deglutition were

taken. Tongue crib appliances were placed in each subject. After 24

hours wear, and prior to removal of the appliances, the myometric re­

cordings and cinefluorographic sequences were repeated.

Conclusions:

(1) The mandibular plane-to-hyoid distance does seem to

influence the ability of the tongue neuromusculature

to adapt to forced posterior displacement.

(2) Hyoid bones positioned relatively distant from the

mandibular plane seemed unable to reposition in an

inferior··posterior direction in response to forced

posterior tongue displacement.

(3) Hyoid bones positioned relatively near the mandibular

plane seemed to possess the potential for inferior­

posterior adaptive repositioning in response to forced

posterior tongue displacement.

(4) The horizontal position of the hyoid bone seemed also

to influence its physiologic adaptive capacity.

51

(5) Lateral cephalometric x-rays taken in the traditional

intercuspal position were found to be unreliable

monitors of hyoid rest position.

(6) From the lack of correlation between myometric and

cinefluorographic data, it was hypothesized that the

intrinsic tongue musculature plays a significant role

in adaptive behavior of the tongue.

52

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Bench, R. W., "Growth of the Cervical Vertebrae as Related to the Tongue, Face, and Denture Behavior", Am. J. Orth., 49: 183-214, 1963.

Brader, A. C., "Dental Arch Form Related with Intraoral Forces: PR=C", Am. J. Orth., 61:541-561, June, 1972.

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C1eall, J. F., Alexander, W. J., and Mcintyre, M. D., "Head Posture and Its Relationship to Deglutition", Angle Orth., 36: 335-350, Oct., 1966.

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Grant, L.A., "A Radiographic Study of the Hyoid Bone Position in Angles Class I, II, And III Malocclusions", Unpublished Masters Thesis, University of Kansas City, 1959.

Gray, H., Anatomy of the Human Body, ed. 26, Philadelphia, Lea and Febiger, 1956.

53

Gobeille, D. M., "Adaptability of Muscle and Hence Hyoid Position Following Forced Distal Repositioning of the Tongue in Open Bite Patients", Unpublished Masters Thesis, Loyola University, 1974.

Hanson, Marv:f.n L. , Barnard, Logan W. , and Case, James L. , "Tongue­thrust in Preschool Children Part II: Dental Occlusal Patterns", Am. J. Orth., 57: 15-22, Jan. 1970.

Hanson, Marvin L., and Cohen, Melvin S., "Effects of Form and Function on Swallowing and the Developing Dentition", Am. J. Orth., 64: 63-82, July, 1973.

Harvold, Egil P., "The Role of Function in the Etiology and Treatment of Malocclusion", Am. J. Orth., 54: 883-898, Dec., 1968.

Hedges, Robert B., McLean, C. Donald, and Thompson, Frederic A., "A Cinefluorographic Study of Tongue Patterns in Function", Angle Orth., 35: 253-268, Oct., 1965.

Ingervall, B., Carlsson, G. E., and Helkima, M., "Change in Loca­tion of Hyoid Bone with Mandibular Positions", Acta Odont. Scand., 28: 337-361, 1970.

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APPROVAL SHEET

The thesis submitted by Kent B. Augustson has been read and approved by the following committee:

Dr. Douglas C. Bowman, Director Associate Professor, Physiology and Pharmacology, Loyola

Dr. Bernard M. Pawlowski Clinical Associate Professor, Orthodontics, Loyola

Dr. Joseph M. Gowgiel Associate Professor and Chairman of Anatomy Loyola

The final copies have been examined by the director of the thesis and the signature which appears below verifies the fact that any necessary changes have been incorporated and that the thesis is now given final approval by the Committee with ref­erence to content and form.

The thesis is therefore accepted in partial fulfillment of the requirements for the degree of Master of Science.

L~kc.o~ Direc~'s Signature Date