BDS [Orthodontics] course

1. FUNCTIONAL DEVELOPMENT
PROF (Dr.) SAIBEL FARISHTA

2. THE FUNCTIONS OF THE ORO-FACIAL REGION INCLUDE MASTICATION,
SWALLOWING, RESPIRATION, SPEECH, FACIAL EXPRESSION AND MAINTAINANCE
OF MANDIBULAR POSITION.
MASTICATION
IT IS A COMPLEX ACTIVITY AIMED AT BREAKING DOWN AND INSALIVATION
OF THE FOOD, PREPARATORY TO SWALLOWING.
IN INFANTS – FOOD IS TAKEN IN BY SUCKING AS THEIR DIET IS MOSTLY
CONFINED TO LIQUIDS. THEREFORE MASTICATION IN TRUE SENSE IS NOT
PRESENT IN INFANTS. AS THE INFANT SWITCHES ON TO SOLID OR SEMI-SOLID
FOOD, IT LEARNS TO USE THE LIPS TO KEEP THE FOOD FROM BEING FORCED
OUT OF THE MOUTH. THE BOLUS OF FOOD IS MIXED WITH SALIVA BY THE
ACTION OF THE TONGUE AND IS FORCED BETWEEN GUM PADS OR THE
OCCLUSAL SURFACES OF THE ERUPTING TEETH.

3. 1) PREPARATORY PHASE – IN THIS PHASE, THE INGESTED FOOD IS POSITIONED
BY THE TONGUE TOWARDS THE CHEWING SIDE AND THE MANDIBLE MOVES
TO THE SAME SIDE.
2) FOOD CONTACT – THIS PHASE IS CHARACTERIZED BY A MOMENTARY PAUSE
IN MASTICATION. THE SENSORY RECEPTORS EVALUATE THE APPARENT
VISCOSITY OF THE INGESTED FOOD AND THE PROBABLE LOAD ON THE
MASTICATORY APPARATUS.
3) CRUSHING PHASE – THE FOOD IS CRUSHED BY EQUAL ACTIVITY ON BOTH
SIDES OF THE DENTAL ARCH. THE CRUSHING STARTS WITH A HIGH VELOCITY
AND GRADUALLY SLOWS DOWN.
4) TOOTH CONTACT –
5) GUIDING PHASE –
6) CENTRIC OCCLUSION –
IN ADULTS – MASTICATION OF FOOD OCCURS IN THESE 6 PHASES
[MURPHY] – 1) PREPARATORY PHASE 2) FOOD CONTACT 3) CRUSHING PHASE
4) TOOTH CONTACT 5) GUIDING PHASE 6) CENTRIC OCCLUSION

4. DEGLUTITION
THE SWALLOWING PATTERNS ARE DIFFERENT IN INFANTS AND IN ADULTS.
TWO MAIN FORMS OF SWALLOWING ARE RECOGNIZED – 1) INFANTILE
SWALLOW 2) MATURE SWALLOW
INFANTILE SWALLOW – DURING THE PROCESS OF SUCKLING, THE NIPPLE
IS DRAWN INTO THE MOUTH BY NEGATIVE PRESSURE FROM WITHIN. THE
TONGUE LIES OVER THE LOWER GUM PADS AND PROTRUDES BETWEEN
THE NIPPLE AND LOWER LIP.
THE MILK IS DIRECTED CONTINUOUSLY TO THE PHARYNX BY AN
AUTOMATIC PERISTALTIC MOVEMENT OF THE TONGUE AND MYLOHOID
MUSCLE. DURING THE PROCESS OF SWALLOWING, REGULAR BREATHING
CONTINUES. EXCESS MILK IN THE MOUTH DRIBBLES DOWN THE CHIN.

5. THE CHARACTERISTICS OF AN INFANTILE SWALLOW [MOYERS] –
1) THE JAWS ARE APART WITH THE TONGUE BEING PLACED BETWEEN THE
UPPER AND LOWER GUM PADS
2) MANDIBLE IS STABILIZED BY CONTRACTION OF THE MUSCLES OF 7TH
CRANIAL NERVE AND INTERPOSED TONGUE
3) THE SWALLOW IS GUIDED AND CONTROLLED BY SENSORY
INTERCHANGE BETWEEN THE LIPS AND TONGUE.
AS THE INFANT BEGINS TO EAT SOLID FOOD, THERE IS A DISTINCT
CHANGE IN THE SWALLOWING PATTERN. THE TONGUE IS CONTAINED
WITHIN THE ARCHES AND THE MANDIBLE IS NO LONGER PROTRUDED.
THIS IS THE ONSET OF MATURE SWALLOW.
MATURE SWALLOW – IS SEEN AFTER 1 YR OF LIFE. THE INFANTILE
SWALLOW GRADUALLY DISAPPEARS WITH ERUPTION OF BUCCAL TEETH IN
PRIMARY DENTITION. DURING TRANSITIONAL PERIOD, CHARACTERISTICS
OF BOTH INFANTILE AND MATURE SWALLOW CAN BE OBSERVED.

6. DEGLUTITON OCCURS IN 4 PHASES
1) THE PREPARATORY SWALLOW 2) ORAL PHASE 3) PHARYNGEAL PHASE
4) OESOPHAGEAL PHASE
1) THE PREPARATORY SWALLOW – THE FOOD AFTER MASTICATION IS
ASSEMBLED AS A COMPACT BOLUS ON THE DORSUM OF THE TONGUE.
TO ACHIEVE THIS, THE TEETH ARE PARTED A LITTLE AND CHEEK
MUSCLES CONTRACT. THE TEETH ARE THEN BROUGHT INTO
OCCLUSION TO STABILIZE THE JAWS AND TO CLOSE THE ORAL CAVITY
PROPERLY. THE POSTERIOR ASPECT OF TONGUE PRESSES AGAINST THE
SOFT PALATE TO ISOLATE THE ORAL CAVITY FROM PHARYNX. BY THIS
TIME, THE ORAL CAVITY FORMS A SEALED UNIT.
2) ORAL PHASE – THE SOFT PALATE IS RAISED TO SEAL OFF THE NASAL
CAVITY AND THE POSTERIOR PART OF TONGUE DROPS DOWN. THIS
CREATES A SMOOTH PATH FOR THE BOLUS AS IT IS PUSHED INTO THE
PHARYNX BY THE PERISTALTIC ACTION OF TONGUE.

7. 3) PHARYNGEAL PHASE – THIS PHASE STARTS AS SOON AS THE FOOD
PASSES THROUGH THE FAUCIAL PILLARS. AS THE FOOD REACHES THE
PHARYNGEAL WALLS, THERE IS A REFLEX UPWARD MOVEMENT OF THE
ENTIRE PHARYNGEAL COMPLEX. WHEN THE PHARYNGEAL WALLS
TOUCH THE SOFT PALATE, A PERISTALTIC MOVEMENT SETS UP TO MOVE
THE FOOD DOWN.
4) OESOPHAGEAL PHASE – IT STARTS AS THE FOOD PASSES THE
CRICOPHARYNGEAL SPHINCTER. PERISTALTIC ACTIVITY OF THE
OESOPHARYNGEAL WALL OCCURS TO PASS THE FOOD INTO THE
STOMACH. THE TONGUE AND PALATE RETURN TO THEIR ORIGINAL
POSITION TO START THE NEXT CYCLE.

8. RESPIRATION
SPEECH
BUCCINATOR MECHANISM

9. TRAJECTORIES OF FORCE
THE TRAJECTORIAL THEORY OF BONE STATES THAT THE LINE OF
ORIENTATION OF THE BONY TRABECULAE CORRESPONDS TO THE
PATHWAYS OF MAXIMAL PRESSURE AND TENSION – THE BONY TRABECULAE
ARE THICKER IN THE REGION WHERE THE STRESS IS GREATER.
‘BENNINGHOFF’ STUDIED THE NATURAL LINES OF STRESS IN SKULL BY
PIERCING SMALL HOLES INTO A FRESH SKULL. LATER, WHEN THE SKULLS
WERE DRIED, HE OBSERVED THAT THE HOLES ASSUMED A LINEAR FORM IN
THE DIRECTION OF THE BONY TRABECULAE. THESE WERE CALLED
‘BENNINGHOFF’S LINES’ OR TRAJECTORIES, WHICH INDICATE THE
DIRECTION OF THE FUNCTIONAL STRESSES.
TRAJECTORIES OF THE MAXILLA – 1) FRONTONASAL BUTTRESS 2) MALAR
ZYGOMATIC BUTTRESS 3) PTERYGOID BUTTRESS
TRAJECTORIES OF THE MANDIBLE – 1) CONDYLE - SYMPHYSIS - CONDYLE

10. T
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11. THANK YOU