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