Stomatognathic system

Presented ByRAJ KR.SINGHJR-2

Introduction Components of stomatognathic system Functions of stomatognathic system Abnormal functions related to stomatognathic system Clinical considerations Conclusion

overview

Salzman defines ‘stomatognathics as

The approach to the practice of orthodontics, which takes into consideration, the interdependence of form & function of the teeth, jaw relationship, temporo- mandibular articulation, craniofacial conformation & dental occlusion

Introduction

It is important to examine teeth in static as well as in dynamic occlusion, as function can influence the overall pattern and the relationship of parts, the very foundation of stomatognathic system

Teeth & their supporting structures Jaw bones & their functional osteology Muscles of the face & head TMJ Tongue , Nerves, Vascular supply & their related

structure

Components

Muscles of oro-facial region include -

Muscle of mastication Helps to support mandibular movement during

mastication and speech Tongue muscle Includes extrinsic and intrinsic group of

muscles ,balancing the buccinator mechanism Muscles of facial expression Helps in various facial expressions and assists

buccinator mechanism

Muscles

Tongue is the very powerful muscle against the buccinator mechanism

A middle fibrous septum divides the tongue into right & left halves

Each half contains four extrinsic & four intrinsic muscles

Tongue

• The integrity of the dental arches & the relations of the teeth to each other within each arch & with opposing members are the results of the morphogenetic pattern as modified by stabilizing & active functional forces of muscles

Forces due to tongue musculature and labial musculature (the

buccinator mechanism) are normally in equilibrium which leads to the eruption and maintenance of the teeth in a stable position called the neutral zone

Even after eruption any change or disruption in the magnitude, direction, or frequency of these muscular forces will tend to move the teeth into a position where the forces are again in equilibrium

Buccinator mechanism

When any body is acted upon forces exerted by surrounding bodies, it is said to be in equilibrium if the resultant of all such forces & moments due to those forces are equal to zero

Four major primary factors which directly influence dental equilibrium ;

1. Intrinsic forces by tongue, cheek,& lips2. Extrinsic forces by habits & orthodontic appliance3. Forces from dental occlusion 4. Forces from PdL

Equilibrium theory

Microglossia

Force from buccinator mechanismcould not be counteractedby the tongue

Resulted in the collepsed max. & mand.arch

Absence of buccinator mechanism

Normal muscle activity are associated with normal jaw relationship and normal occlusion

Class II Div.1 malocclusion

Abnormal mentalis muscle activity Lower tongue position Increased buccinator muscle activity The maxillary arch narrows and assumes the V shape

Mandibular retrusion & Excessive apical base Difference - Middle & post. Temporalis & deep masseter fibre shows greater magnitude of contraction - they adapt & enhance the mand. retrusion

Class II malocclusion with deep overbite

Functional retrusion tendency increased, - in addition to middle , posterior temporalis & deep masseter activity, -stretch reflex may be elicited for the lateral pterygoid fibres which inserts into the articular disc ,- pulling the disc forward as the condyle is functionally retruded

In class ll Div. 2 malocclusion activity of the cheek and lip muscles is usually normal, contrary to Division 1 malocclusion

The tongue at least tends to accentuate the excessive curve of Spee and that it interferes with the eruption of the posterior teeth by occupying the interocclusal space increasing the interocclusal gap

The upper lip is relatively short, though not necessarily hypotonic

The lower lip is hypertrophic and redundant and appears to be relatively passive during the deglutition cycle

During swallowing, there is actually a greater activity of the upper lip

The tongue does appear to lie lower in the floor of the mouth

The maxillary arch is usually narrow

Class lll malocclusion

There is a variation in the number of muscle fibers per motor neuron within the muscles of mastication

Lateral pterygoid muscle - relatively low muscle fiber/motor neuron ratio,capable of fine adjustments in length needed to adapt to horizontal changes in the mandibular position

Masseter - greater number of motor fibers per motor neuron, more gross functions of providing the force necessary during mastication

Temporalis- when whole muscle contract it raise the mandible & the teeth are in contact; but when the ant.portion contract, it raises mand.verticaly ,

if the middle portion , ‘it elevates & retrude the mand.

If the post. portion ‘ it leads to only retrusion of mandible.

TMJ is diarthroidal synovial joint consisting of head of mandibular condyle articulating with temporal fossa of temporal bone and assists in mandibular movement during various functions

TMJ

Supported by

True ligaments

- Capsular ligaments- Temporomandibular ligament

Accessory ligament

- Sphenomandibular ligament- Stylomandibular ligament

Ligaments of TMJ

Mastication In the infant food is taken by suckling as described by

BOSMA, the classic suckle swallow Act of chewing food when the food is broken down

into smaller particle sizes for swallowing It is a functional activity that is automatic and

practically involuntary, yet when desired it can be readily brought under voluntary control

Functions of stomatognathic system

Forces of mastication

Varies in Females-79 to 99 pounds Males –118 to 142 pounds

Force applied to molar is several times that of incisor

First molar-91 to 198 pounds Central incisor-29 to 51 pounds

Fletcher summarizes recent work on the masticatory stroke in the adult , using six phases outlined by MURPHY

Preparatory phase Food contact phase Crushing phase Phase of tooth contact Grinding phase Centric occlusion

SWALLOWING (DEGLUTITION)

Swallowing is a series of coordinated muscular contractions that moves a bolus of food from the oral cavity through the esophagus to the stomach. It consists of voluntary, involuntary, and reflex muscular activity.

Essential features of swallowing

Obligate muscles Geniohyoid Mylohyoid Posterior tongue Superior constrictor Palatopharyngeus

Facultative muscles Massater Orbicularis oris Temporalis

Muscles involved

First stage Voluntary and begins with

selective parting of the masticated food into a mass or bolus

The bolus is placed on the dorsum of the tongue and pressed lightly against the hard palate

Lips are sealed and the teeth are brought together

The presence of the bolus on the mucosa of the palate initiates a reflex wave of contraction in the tongue that presses bolus backward

As the bolus reaches the back of the tongue, it is transferred to the pharynx

Second stage The soft palate rises to

touch the posterior pharyngeal wall, sealing off the nasal passage

Once the bolus has reached the pharynx, a peristaltic wave caused by contraction of the pharyngeal constrictor muscles carries it down to the esophagus

The epiglottis blocks the pharyngeal airway to the trachea and keeps the food in the esophagus

During this stage of swallowing the pharyngeal muscular activity opens the pharyngeal orifices of the Eustachian tubes, which are normally closed

Symptoms of tongue thrust is observed during this stage

Third /fourth stage This stage consists

of passing bolus through the length of the esophagus and into the stomach

As the bolus approaches the cardiac sphincter, the sphincter relaxes and lets it enter the stomach

Jaws apart with the tongue between the gum pads

Mandible is stabilized by the contraction of the muscles of the 7th cranial nerve and the interposed tongue

The swallow is guided and to a greater extent controlled by interchange between lips and the tongue

Characteristics of infantile swallow (Moyers)

Infantile swallowing usually persists for 5-6 months of age, when a transitional stage begins with the eruption of incisors

Certain proprioceptive impulses come into play and the peripheral portion of the tongue starts to spread laterally This change in tongue function is gradual

Usually, by 18 months of age, the mature swallow pattern comes into play

Moyers (1971) listed the characteristics of mature swallow

The teeth are together The mandible is stabilized by contraction of the mandibular elevators, which are primarily Vth cranial n. musclesThe tongue tip is held against the palate, above and behind the incisors There are minimal contractions of the lips during the mature swallow

Somatic swallow

Persistence of the infantile swallowing reflex even after the eruption of the permanent teeth

Very few have this type of swallow Teeth occlude on only one molar in each quadrant They demonstrate violent contractions of 7th cranial nerve

musculature during swallowing and tongue is markedly protruded between all teeth during initial stages of swallow

The patients will have an expression less face since facial muscles are used for stabilizing the mandible

Retained infantile swallow

Swallowing pattern in class llA With normal skeletal relationship with occlusion Class II Division 1 "Teeth apart" swallow

with lower lip contraction and tongue thrust

B With Class II skeletal relationship (mandibular retrusion). "Teeth apart" swallow with strong tongue thrust

C Class Il, Division 1 with "teeth together" swallow, lower lip not active— its position secondary to the jaw relationship

Speech is the third major function of the stomatognathic system

Controlled contraction and relaxation of vocal cords

create a sound with desired pitch

Once the pitch is produced, the precise form assumed by mouth determines the resonance and exact articulation of the sound

Speech

Tooth contacts do not occur during speech

A malpossed tooth contact during speech can lead to a new speech pattern that avoids tooth contact , by way of sensory inputs quickly relayed to CNS

Once speech is learnt, it comes almost entirely under the unconscious control of the neuromuscular system. In that sense it can be thought of as a learned reflex

There are two processes in the production of speech

Phonation -It is the production of airflow and the establishment of

frequency Articulation of sound -Varying the relationships of the lips and tongue to the

palate and teeth, one can produce a variety of sounds

Important sounds formed by lips are “M”, “B”, and “P”. During these sounds lips come together and touch (Bilabial sounds)

In saying “S”\ Z teeth are important. The incisal edges of maxillary and mandibular incisors closely approximate and air is passed between them ( siblant sound)

e.g. Anterior open bite, large gap b/w incisors

The tongue and palate are important in forming the ‘T’ “D” sound (linguoalveolar)

e.g Irregular incisors

The tip of the tongue touches the palate directly behind the incisors.Tongue touches maxillary incisors to form the “Th” sound

The lower lip touches the incisal edges of maxillary incisors to form the “F” and “V”sounds (labiodental)

e.g. Skeletal class III

For sounds like “K” or “G” the posterior portion of tongue touches the soft palate

Speech problems which may be improved by orthodontics are those of faulty articulation

The articulatory valves are◦ Velopharyngeal valve◦ labiodental, ◦ linguodental, and ◦ linguoalveolar valve

Respiration, like mastication & swallowing is an inherent reflex activity

Bosma & coworkers have analysed respiration in infant & found that quiet respiration is carried out through nose, with the tongue in proximity to the palate , obturating the oral passage

Respiration

Both pharynx & larynx are active during respiration & it is this area that infant differentiates between respiration & associated activities such as cough , grunt, cry & sneeze

Posture of tongue also has significant effect on respiration

Base of the tongue forms the anterior wall of the pharynx which serves as the portal for both, the alimentary tract and the airway

-Maintenance of the pharyngeal airway demands that the tongue base not be allowed to intrude into this airway; and this is taken care of by the genioglosus muscle

- Development of respiratory spaces & maintenance of the airway are significant factors in orofacial growth

Mouth breathing Etiology 1) Naso-pharyngeal obstruction due to Nasal deformities – DNS Irritation or thickening of mucosal membrane of nose Bone pathology Enlarged adenoids 2) Mouth habits Thumb sucking lip biting, finger or nail biting, tongue thrusting 3) Abnormal development Macroglossia Short upper lip 4) Psychosomatic problems

Abnormal functions related to stomatognathic system

Effects Tongue position is low and forward to keep oral airway

open Force against the buccal surfaces of maxillary

posterior teeth is not balanced by tongue in the palatal area

Upper lip flaccid, short, with lack of tonicity Labial flaring of maxillary anterior teeth Hypertrophy of lower lips

Frequently marked overbite Dryness of mouth Gingivitis and increased dental caries Affected gingiva is demarked from unaffected gingiva,

the junction has been referred by ‘Worwick’ as tension ridge

Bruxism Bruxism is a conscious or subconcious act

performed by an individual which overrides the protective neurologic mechanism of masticatory system. In bruxism there is increase in tonic activity in the jaw muscles

Emotional or nervous tension, pain or discomfort and occlusal interferences are the factors that can increase muscle tonus and lead to non-functional clenching

Effects Tenderness of masticatory muscle Incisal wear, occlusal facets TMJ pain, headache or tiredness of masticatory

muscles

Tongue thrust

It is also known as perverted or deviated swallow, retained infantile swallow, tooth apart swallow, tongue thrust syndrome or abnormal swallow

Fletcher has collected a grouped patterns associated with or characteristic of tongue thrust. They may include some or all of following-

A thrusting movement of tongue against or between anterior teeth

Slight or no contraction of muscles of mastication Strong contraction lip musculature Movement hyoid bone in oblique or forward direction Distortion of speech sound

Etiology Prolonged Bottle feeding Hereditary Oral habits – Thumb sucking, open bite Ankyloglossia or macroglossia may cause tongue thrust Tonsillar tissue – If tonsiller tissue enlarged, can create

obstruction in oro-pharyngeal area posterior to root of tongue. As a consequence tongue may be forced to posture forward

CNS disorders – Neuromuscular problems can be severe enough to prevent normal adult swallow

Recent investigations has been accumulating demonstrate that so called tongue thrust seems more likely to be the effect than the cause of malformations

Classification a) Simple tongue thrust This is localized posturing forward, of the tongue

during rest and active function with localized anterior openbite

b) Complex tongue thrust Forward tongue posture, tongue thrusting during

swallowing, contract of perioral muscles, excessive buccinator hyperactivity. When all these symptoms present the pattern is often called as complex tongue thrust

Effects of tongue thrust Anterior openbite Lateral or posterior open bite Proclinated upper incisors,interdental spacing Hypotonic upper lip and appear retracted or short Bilateral narrowing of maxillary arch

Lisping These are commonly occurring speech defects

Etiology Main cause is continuity of infantile mode of speech. If the tongue is moved forward without mandible and lies on top of lower incisors lisping may result

Certain malocclusions like openbite, maxillary protrusion, mandibular retrusion and mal-aligned tooth also cause lisping

During diagnosis all functions of stomatognathic system should not be proper and it can be primary etiologic factor in a malocclusion

Many dysfunctions are acquired in the early stages of development

Malocclusions that are acquired as a result of dysfunctions can usually be treated simply by elimination of disturbing environmental influences, which will foster normal development

 

CLINICAL CONSIDERATIONS

  Respiration We should check for breathing weather it is nasal or oro-nasal by

various tests Inductive plethysmography (Rhinomanometry) is

gold standard and measures extent of airflow through oral and nasal passage

The etiologic factors of mouth breath is first recognized and then they are removed Later on the restoration of oral health is done by giving proper habit breaking appliances and also different exercises like deep breathing, vigorous exercises, playing on blowing type of musical instruments and lip exercises

Mastication

The therapy includes elimination of triggering elements, mainly discrepancies between, centric relation and CO by occlusal adjustment, by giving occlusal bite plate, protective mouth guard or rubber splints

Deglutition Between 2 to 4 years of age mature swallow is seen in normal developmental patterns. If the infantile swallowing persists well after 4 years of life and is considered a dysfunction or abnormal because of its association with certain malocclusion

A proper diagnosis of tongue thrust should be done on the basis of clinical features or by checking the swallowing patterns. Circum oral tension is being used as diagnostic criteria by many clinicians

If the tongue thrust is present at 3 to 9 years of age no appliance therapy is usually indicated only the dentist instruct the patient how to swallow correctly. On recall appointments if the openbite improves or remains same, this approach is continued until 9 years of age. If open bite continues to increase intraoral therapy is indicated

If tongue thrusting is associated with lisping, only a speech therapist should be encouraged to correct the speech problem using articulation therapy

Speech Speech is largely learned reflex The presence of speech defects in childhood is due to

lack of sufficient training and maturity As these factors are provided, the speech defects

disappears.The guardians and teachers should encourage childrens to pronounce correctly

Articulating defects is improved by orthodontists Speech therapy may be required in conjunction

Before appreciating abnormal functions of the oro-facial muscles a knowledge of their normal development and maturation is must

Abnormal functions or habits may be considered normal for a certain stage of child’s development

In young patients, new ideas are more easily learned and more easily broken, and ill effects can be checked from getting adapted so the treatment of habit should be started as early as possible

CONCLUSION