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Contents:

Introduction

Theories of deglutition

Neuro- physiology of deglutition

Phases of deglutition

Types of swallowing

Deglutition in cleft patients

References

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Deglutition or Swallowing

Introduction

Deglutition/ swallowing is an innate unlearned behavior first occurring in the

Fetus. Swallowing is complicated mechanism principally because the pharynx subserves

respiration as well as swallowing.

Swallowing can be initiated voluntarily but there after it is almost entirely under

reflex control.

One of the important physiological functions of the human body that

has long been recognized to influence the positions of teeth and the jaws in relation

to the rest of the head is DEGLUTITION

Definition

The taking in of a substance through the mouth and pharynx, past the

cricopharyngeal constriction through the esophagus and into the stomach.

A complicated act usually initiated voluntarily but always completed reflexively

whereby food is moved from the mouth through the pharynx & esophagus to the

stomach.

Teeth are moved physiologically by the growth of investing tissues, especially the

bone and that to obtain bone growth we must stimulate it through pressure. This

pressure may be normal and tend to the teeth into their proper positions of

occlusions, or the pressure may be abnormal and tend to move the teeth into

improper positions of malocclusion.

Some Antagonistic Forces Acting on the Masticatory Apparatus Lip tongue

Cheeks tongue Eruption of teeth masticatory musclesmasseter, temporalis and medial

pterygoid

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Air pressure of the skin - tongue (in closed mouth) Airpressure in nasal cavitytongue (open mouth)

Masseterelasticity of periodontal ligament (particularly of molars).

Internal pterygoidsame as masseter in vertical movement

External pterygoid in anterior movementposterior one third of temporalis,suprahyoid group, digastric and muscles of neck.

External pterygoid in lateral movementexternal pterygoid of opposite side

Theories of deglutition:

1) Theory of constant propulsion

2) Theory of oral expulsion

3) Theory of negative pressure

4) Theory of integral function

THEORY OF CONSTANT PROPULSION:

Early concepts of deglutition is based on the knowledge of anatomy andthe experiments carried on the animals. They assumed that the various structures involved in deglutition acted upon

the bolus of food consecutively to propel it from the mouth through the

pharynx into the esophagus.

In the classical work of Magendie 3 stages of propulsion were noted with certain important modifications this theory is closely related to modern

concepts of swallowing

THEORY OF ORAL EXPULSION: (1880) kronecker et al in 1880 suggested that the bolus was ejected from the mouth

directly into the stomach by the piston like action of tongue and mylohyoid

musculature.

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Cannon in 1911 believed that kroneckers theory applied to only fluids &semifluids,he believed that solids and semisolids were handled by a

consequtive peristaltic type action , similar to that of magendie

Oral expulsion theory is not supported by current findings

Manometric and flouroscopic techniques used by the authors in proposingthis theory were unable to detect the rapid changes in the pharynx

THEORY OF NEGATIVE PRESSURE:

Barclay used flouroscopy and observed a moment of radiolucency in thehypopharynx immediately preceeding the decent of the bolus.

He postulated that this radiolucent area indicating pharyngeal dilation wasevident of the negative pressure, which he felt was the primary propulsive

force in deglutition.

This negative pressure was obtained by simultaneous lowering of larynx andforward motion of the tongue while the opclosedenings of the pharynx were

In an experiment by Atkinson 1956he found double peaked positive air pressure in pharynx, first peak

corresponded to the entrance of bolus into pharynx and the second wave

corresponded to the constrictor action.the presence of these positive

pressures refutes the suction action to be the source of bolus transmission.

Further palato-pharyngeal valve is often open for a moment at the beginningof normal deglutition. So negative pressure cannot be present to propel the

bolus while the palatopharyngeal valve is open.

THEORY OF INTEGRAL FUNCTION:

Cineflourography allows visualization of the dynamics of deglutition.

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Studies using this method supports the magendies concept Bolus passes distally through a series of muscular valves by highly

integrated reflexes

Reflexes

Storey (1976) considers swallowing to be essentially an airway protective

reflex and has classified the reflex events associated with maintaining the

integrity of the airway and alimentary canal where they cross in pharynx as

a. Protective reflexes :

- These are concerned with preventing entry into or alimentary canal (eg.

Sniffing, sneezing, coughing, ganging, swallowing)b. Supportive reflexes:

- These are concerned with obtaining air & food (eg. Suckling, mastication,

airway maintenance)

- The hierarchical organization is :

- Protective reflexes before supportive reflexes

- Airway maintenance reflexes before alimentary canal reflexes.

- Under normal circumstances deglutition is preprogrammed & reflexly

controlled and once triggered is an all or none response.

Indications of reflex nature of swallowing:

Swallowing occurs during sleep

During general anaesthesia it is increased.

Grandma epileptic seizures are characterized by vigorous swallowing.

Variations in swallowing occur with

Degree of lubrication of food with saliva eg. Problems arise in the event of

salivary gland dysfunction & in diseases where there is reduced salivary

flow.

The state of mucous membrane eg. Friable, atrophic tissues associated with

chronic disease.

The material swallowed eg. Solid & liquids are handled differently as are

solids of varying consistency.

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Phases of swallowing:

Fletcher divided the Deglutitional Cycle into 4 phases, which are highly

integrated and synergistically co-ordinate.

1) Preparatory swallow2) Oral phase of swallowing

3) Pharyngeal phase of swallowing

4) Esophageal phase of swallowing

Preparatory swallow:

Initiated when the tip of tongue separates a bolus of food from the

remaining mass of food in the mouth.

Pharyngeal phase of swallowing

Involuntary & constitutes passage of food through the pharynx into

esophagus.

Esophageal phase of swallowing

Another involuntary phase that promotes

Passage of food from the pharynx to the stomach.

1) Preparatory swallow:

Preparatory phase starts as soon as liquids are taken in or after the bolus

has been masticated.

The liquid or bolus is taken in swallow preparatory position on the on the

dorsum of tongue.

In the infant, bolus accumulation may be seen also between the base of

tongue & the epiglottis.

The oral cavity is sealed by lip & tongue.

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2) Oral phase of swallowing

Soft palate moves upwards & the tongue drops downwards & backwards.

At the same time the larynx & hyoid bone move upward.

These combined movements create a smooth path for bolus as it is pushed from

oral cavity by wave like rippling of tongue. In case of liquid it flows ahead of lingual constrictions.

Oral cavity stabilized by muscles of mastication maintain an anterior & lateral

seal during this phase.

Distal movement of the bolus begins with- depression of pharyngeal portion of the tongue

- elevation of the soft palate

distal squeezing action of tongue against hard palate Ardran described it as tooth paste This analogy more accurate for solids than liquids. Ramsay observed progressive narrowing and obliteration of lumen behind

bolus and called it stripping wave.

lingual pressure in the anterior and lateral peripheral seal areas were similar

3) Pharyngeal phase of swallowing

Begins as the bolus passes through the fauces.

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The pharyngeal tube is raised upward en-mass & the nasopharynx is sealed off

by closure of soft palate against the posterior pharyngeal wall (i.e. Passavants

ridge)

Hyoid bone & the base of tongue move forward as both pharynx & tongue

continue their peristaltic movement of bolus.

Occurs in less than 2 seconds.

As the bolus passes from oral cavity to the upper end of esophagus throughthe oral and laryngeal portions of the pharynx there are 4 openings to be

closed

- Nasopharynx

- Eustachian tube

- Glottis

Naso-pharynx - closed of from oropharynx

approximation of posterior pillars of fauces

- palatopharygeous muscle

elevation of the uvula

- levator palatini

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Auditory tube - salpingo-pharyngeal muscle

Epiglottisminor role in protection of laryngeal air way adduction of vocal cordscricoarytenoids

aryepigloticus

larynx pulled upapposed to tonguestylopharyngeal

salpingopharyngeal

palatopharyngeal

inferior constrictor

Deglutition apnea:

Momentary arrest of breathing during pharyngeal stage of deglutition .

Occurs when bolus is pushed from pharynx into esophagus

Protective mechanism

When at rest the pharynx is closed by the approximation of the anterior andposterior walls of the pharynx

Posterior wall is firmly attached to the prevertebral fassia Anterior wall of the laryngo-pharynx is formed by the larynx To open the pharynx larynx must be elevated, which is assisted by the hyoid

bone elevation

Movement of the hyoid:

Hyoid bone suggest as a posterior pedestal for the attachment of the tongue

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Shelton et al described 3 phases of hyoid movementPhase 1: simultaneous cephalad movement of hyoid

elevation of larynx

dorsad movement of pharyngeal portion of tongue

Occurs prior to the descent of bolus

Phase 2: cephaloventrad

Occurs as the bolus descends through the pharynx into esophagus

Phase 3: return of hyoid to pre swallow position

posterior belly of digastric , stylohyoid

obliquely postero-inferiorly

Ramsay stated that movements of the hyoid bone depends on size of the bolus

The bolus is literally crammed down the pharynx , past larynx

- backward downward action of tongue

- hyoglossus, inferior lingualis

Pharynx is elevated at the same time

Later pharynx descendsinfra hyoid muscles

Middle and superior constrictors of pharynx

- peristaltic wave

- Bolus passes into esophagus

- bolus carried down and prevented from regurgitation

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4) Esophageal phase of swallowing

Commences as food passes the cricopharyngeal spincter.

While peristaltic movements carry the food through esophagus, hyoid bone,

palate & tongue return to their original position. Esophagus normally exhibits 2 types of peristaltic movements

i. Primary peristalsis

ii. Secondary peristalsis

1) Primary peristalsis

Passes all over from pharynx to stomach in about 8-10sec.

Food swallowed by person who is in upright position is usually transmitted to the

lower end of esophagus even more rapidly than peristaltic wave itself in about 5-8sec, due to additional effect of gravity pulling the food downwards.

2) Secondary peristalsis

If primary wave fails to move all the food entered the esophagus into stomach

secondary peristaltic wave results from distention of esophagus by retained food &

continue until all food has emptied into stomach.

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Clinical conditions affecting swallowing :

Oral Dysphagias :

- Clinical conditions affecting oral mucous membrane particularly Tongue

causing Glossitis preventing its elevation which may prevent the development of

required intraoral pressure gradient

Conditions include1) Iron deficiency anaemia

Leading to glossitis & may be associated with candidial infection.

2) Pernicious anaemia

Glossitis may be first sign

3) Other conditions include, apthous stomatitis, bechets syndrome & lichen

planus.

- Pharyngeal dysphagias- With a palatal cleft, paresis of soft palate or nasopharngeal carcinoma, closure of

nasoparynx may not occur satisfactorily & liquid, food may pass into nasal cavity.

- After palatal clefts tumors responsible for majority of pharyngeal dysphagias.

- Esophagial dysphagias:

- Hysterical spasm of cricopharngeous or emotional esophageal dysphagias may

accompany emotional stress. Eg. Students undergoing oral examinations/ viva.

- Salivary flow is reduced due to stress leading to dry mouth & cricopharngeal

muscle spasm as well.

- Speaking & swallowing become difficult.

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Frequency of swallowing:

- The average individual swallows about once a minute between meals & 9 times a

minute.

- Even during sleep swallowing act is performed at infrequent intervals.- Over 24 hours period, swallowing occur as many as 1000 times.

Suckling:

- Newborn & infants feed by a process called suckling in which the intakes

consists of fluids.

- Suckling is complex process involving development of negative pressure or

suction in oral cavity combined with jaw movement to express milk from the

nipple.- Can ber elicited in human fetus at 20 weeks in utero although full swallowing &

suckling begin only after approx 32-36 weeks.

- Indication of their responsiveness & vigour & neurological maturation.

Divided in 2 phases

1. Lowering of jaw with forward & downward displacement of body of tongue.

2. Elevation of jaw upward & Backward displacement of tongue.

Infantile swallow (visceral swallow)

Moyers lists characteristic of infantile swallow as follows:

The jaws are apart i.e. tongue placed between gum pads.

The mandible is stabilized primarily by contraction of muscles of VII cranial

nerve & interposed tongue.

This swallow is guided & to a great extent controlled by sensory interchange

between the lips & the tongue.

Mechanism

Gum pads not in contact during the act of swallowing. .

Plunger like action is associated with nursing.

Cheek pads flow between posterior gum pads during nursing, unopposed by the

peripheral portion of tongue.

Associated with tongue thrust is the anterior positioning of mandible.

Condyles may be felt gliding rhythmically forward & backward in the nursing

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act.

Concave midline contour of dorsum.

Parsed lips due to perioral sphincter action.

Transitional period:

With the change of semisolid & solid food & the eruption of teeth there

Transitional period:

is also a modification of the swallowing act.

The tongue no longer is forced into the space between gum pads or incisal

surfaces of teeth which contact momentarily during swallowing.

Diminishing of buccinators activity & appearing contractions of definition

mandibular elevators during swallow.

The change to adult swallow pattern occurs gradually which is called astransitional period. Conditioning Factors

Neuromuscular maturation

Change in head posture

Gravitational effect on mandible

This transitional period is of 6 to 12 months.

Mature swallow (somatic swallow) :

Seen after 18 months of age

Mature swallow characteristics listed by moyers are readily observable.

1. Teeth are together

2. The mandible is stabilized by contractions of mandibular elevators, which are

primarily v th cranial nerve muscles.

3. The tongue tip is held against the palate above & behind incisors.

4. There are minimal; contractions of lips.

5. There are minimal contractions of lips.

Mechanism

- Dorsum is less concave & approx the palate during deglutition.

- Tip of tongue is contained behind incisors periphery flow between apposing

posterior segments.

- Anterior mandibular thrust has disappeared

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Abnormal swallowing:

Tongue thrust

DefinitionProfit defined tongue thrust swallowing as placement of tongue tip forward

between incisors during swallowing.

PROFFIT and MASON (1975)

Tongue thrusting is one or a combination of 3 conditions:

Forward placement of tongue during swallowing so that the tip of the tongue

contacts the lower lip.

Inappropriate placement of the tongue between or against the anterior dentition

during speech.

Forward positioning of the tongue at rest so that the lip is against or between the

anterior teeth

Norton & Gellin. A condition in which the tongue protrudes between anterior &

posterior teeth during swallowing with or without affecting tooth position

SUBTENLEY and SUBTELNY (1962)

Tongue thrust pattern of swallowing, is marked by:

a) Contraction of circumoral musculature

b) Separation of maxillary and mandibular posterior teeth.

c) Protrusion of tongue between incisors

EtiologyFletcher (1975)1. Genetic factors :

They are specific anatomic or neuromuscular variations in orofacial regions that

can participate in tongue thrust.

2. Learned behavior (Habit):

Improper bottle feeding prolong thumb sucking prolonged tonsillar & upper

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respiratory tract infections, prolonged duration of tenderness of gums & teeth

result in change in swallowing pattern to avoid pressure or tender zone.

3. Maturational factors:

Late maturation from infantile pattern of swallow.

Late maturation from immature pattern of general oral behavior.4. Mechanical restrictions:

Macroglossia

Enlarged tonsils & adenoids

5. Neurological disturbances:

Hypersensitive palate precipitate crude pattern of manipulation & swallowing.

Disruption in tactile sensory control & coordination of swallowing.

Moderate motor disability & loss of preceision in oral function.

6. Psychological factors Substitution of tongue thrust for forcibly discontinued thumb sucking.

Exaggerated motor image of tongue.

Modern view:

Tongue thrust is seen in 2 circumstances

1. Younger children with reasonably normal occlusion: it is a transitional stage in

normal physiologic maturation.

2. Individual of any age with displaced incisors : as an adaptation for overket &

overbite.

Simple tongue thrust swallow:

Definition:

It is defined as tongue thrust with teeth together swallow

- Displays contractions of lips, mentalis & mandibular elevators.

- Teeth are in occlusion as tongue protrudes into open bite teeth together swallow

with thrust.

- History of digit sucking adaptive mechanism to maintain open bite created by

thumb sucking.

- Well circumscribed open bite.

- Also found with hypertrophy of tonsils which are enlarged enough to prompt a

tooth apart swallow.

- Precise secure interception reinforced by simple tongue thrust swallowing.

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- Diminishes with age .

- Treatment is simple, prognosis is certain.

Complex Tongue Thrust:

- Definition: tongue thrust with a teeth apart swallow - combined contractions of

lips facial & mentalis muscles.

- Lack of contractions of mandibular elevators.

- Teeth appear swallowing.

- H/O breathing or chronic nasorespriratory diseases & allergies.

- More diffuse open bite.

- Seen in cases where tonsils are so inflamed to cause tooth apart swallow.

- Poor occlusion fit & intercuspation(distinguishing feature)

- Dose not diminished with age.

- Poor prognosis.

- Generalized anterior open bite (distinguishing factors)

Retained infantile swallow:

- Definition : undue persistance of infantile swallow well post clinical features the

normal time for this departure massive grimace.- Anterior & lateral thrusting.

- Inexpressive face due to use of facial muscles for swallowing.

- Difficulty in mastication since they only occlude on one molar each quadrant.

- Low gag threshold.

- Poor prognosis.

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- Usually associated with craniofacial developmental syndromes & neural deficit.

- Excessive anterior face height.

Management

- Habit interception- Since tongue thrust is age related management involve habit interception

followed by treatment of malocclusion.

- 3-11 years

- Normal occurrence. Not to be concerned, reassure parents.

- If under 7 years there is no need to be concern since speech sound that elicits a

lisp are not matured until 7-8 years.

- Both fixed and removable cribs or rakes are valuable acids in breaking habit.

- Child tongue to correct method of swallowing.- Muscle exercises of tongue to adopt to a new swallowing pattern.

- 11 years or older not a normal pattern.

Methods of examination of tongue thrust

- Electro-myography

- Tongue pressure changes intraorally

- Roentgeno-cephalometric analysis

- Cineradiography

- Palatography

Electromyography: Moyers investigated functional movements of the orofacial

musculature using the electromyograph. Since then, Tulley,Marx and many othershave contributed. Although the labial musculature can be studied in this way, and

an important contribution has been made to our understanding of lip posture, it is

quite impossible to study the tongue musculature by electromyography.

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Measurement of intraoral pressures: With the introduction of small transducers,

intraoral pressures can be measured more accurately than with other methods

previously described. Winders21 was probably the first in this field, and he has

been followed by many other investigators who have confirmed that the tongue is

probably more important than the surrounding musculature in its effect. Lear and

Luffingham23 showed that the speed and intensity of the rapid movements of the

tongue in speech and swallowing were probably not so significant as the resting

posture, which will be seen to confirm many clinical observations.

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Cinefluoroscopy: Ardran and Kemp, Cleall, Tulley and others have shown that

this technique has limitations in terms of speed and is only two dimensional. It

does not lend itself to serial studies because, although the dosage is small usingimage intensifiers, it is difficult to persuade patients that it is clinically necessary.

Cephalometric head films: Peat and others have shown the possible differences

between the relaxed and habitual postures of the tongue and this, in turn, has made

some contribution to our knowledge. However, this technique is subject to

variation.

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Neurophysiologic experiments: Bosma and his co-workers, Grossman,Berry,and

Fawcus, have carried out various neurologic tests on the behavior of the tongue. So

far, the use of stereognostic tests has indicated very considerable individualdifferences in lingual sensorimotor factors, and I am sure that this work will

continue.

Serial cinephotography: This is difficult to analyze scientifically, but it does

highlight the individual variations. Although cinephotography cannot display the

intraoral movements of the tongue, work by Whillis and other film studies carried

out by the Veterans Organization have shown tongue movements through surgical

defects in the face. This longitudinal approach has proved to be of great value, as

will be seen later.

Muscle activity during swallowing in cleft patients

The electromyographic activity of the thyrohyoid muscle (TH), the geniohyoid

muscle (GH), and the myohyoid muscle (MH) of patients with CLP when

compared with noncleft subjects during swallowing and drinking water with and

without artificial nasal obstruction. In the normal situation without nasal

obstruction, a significant difference in muscle activity between the two groups wasfound only for TH. In normal subjects, the duration and magnitude of muscle

activity were significantly larger in all the muscles when a nasal obstruction was

applied. Meanwhile, in the CLP patients these values exhibited a significant

increase in GH and MH only. With nasal obstruction, the burst durations of GH

and MH are significantly longer in the normal cases than in the CLP patients.This

suggest that in CLP patients during swallowing, TH working from the pharyngeal

stage compensates for the weakness of GH and MH working in the oral phase. This

may cause a premature transfer of the bolus to the pharynx before making it

properly into the oral cavity.

The influence of maximum perioral and tongue force on the incisor teeth

Pressure the lips influence the position of the incisors along with the antagonistic

of tongue. Posen used pomometer to measure the muscular activity of the lips.

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Perioral muscle force increases with age Perioral force is considered to be maximum in class II DIV 2 subjects A Significant relation exists between maximum strength and force of the lips

and final angulation of the incisors

Peri-oral musculature is classified based on their tonicity as8-9 yrs patients 90-120 gmhypotonic

120- 150 - normal

150 -180 hypertonic

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REFERENCES:

1) Text book of physiologyGyton

2) Human AnatomyChaurasia

3) Patterns of deglutitionA.J Wildman et alAO oct 1964

4) Muscle contraction patterns in swallowingAO VOL 42

5) Malocclusions, orthodontic corrections and orofacial muscle adapatations

vol 40 no 3

6) deleterious effects of oral habitsInd. J. dent sciences 2009

7) A Cineradiographic Study of Deglutitive Tongue Movement and

Nasopharyngeal Closure in Patients with Anterior Open Bite - Angle Orthod

2000;70:

8)Pressure from the lips on the teeth and malocclusion : Urs Ther, and Bengt

Ingerva - AJO 1986 Sept

9) AJO-DO, Volume 1969 Jun (94 - 104): A critical appraisal of tongue thrusting

- Tulley

10) AJO-DO, Volume 1963 Jun (418 - 450): The "three M's": Muscles,

malformation, and malocclusion - T. M. GRABER

11) Alderisio, J. P., and Lahr, Roy: An Electronic Technique for Recording the

Hypodynamic Forces of Lip, Cheek, and Tongue, J. D. Res. 32: 548-553, 1953

12) Baker, R. E.: Tongue and Dental Function, AM. J. ORTHOD 40 : 927-939,

1954.

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