Functional Development Question And Answers

Functional Development

Question 1. Write short note on trajectories of forces.
Or
Write briefly on trajectories of force.
Or
Write short note on trajectory of force in maxilla.
Answer. The trajectorial theories of force states that, “the lines of orientation of the bony trabeculae corresponded to the pathways of maximal pressure and tension and that bone trabeculae are thicker in the region where the stress is greater”. Trajectories were fist discovered by Benninghof by making small holes in fresh skull, so they are also called Benninghoffs lines.

Trajectories of force are divided into two categories, i.e.

• Trajectories of maxilla.
• Trajectories of mandible.

Trajectories of Maxilla

• Due to trajectories maxilla provide maximum strength with minimum material.
• Trajectories of maxilla are divided into vertical pillars and horizontal reinforcing members.
• Vertical pillars are frontonasal or canine pillar, malar zygomatic pillar and pterygoid pillar.

Read And Learn More: Orthodontics Question And Answers

• Frontonasal vertical pillar: It transmits pressure from incisors canine and fist premolar. It runs vertically along piriform aperture and crest of nasal bone, it terminates in frontal bone.
• Zygomatic vertical pillar: This buttress transfer stress from posterior teeth and receive force of massater muscles. In zygomatic area it split of in three parts, i.e. to zygomatic arch, at lateral border of orbit and at lower border of orbit. Then it finally terminates at base of skull.
• Pterygoid vertical pillar: It runs from conchae of nasal cavity and posterior teeth and it terminates in mid portion of base of skull.

• Horizontal reinforcing members: Supraorbital rim act as receptor of forces from both canine and zygomatic pillar. Various other reinforcing members are wall of Infraorbital, orbital wall, lesser wings of sphenoid, zygomatic buttress, hard palate.

Trajectories of Mandible

Mandible is made up of two types of trajectories, i.e. minor and major trajectory.

Minor Trajectories

• Trajectories are also visible at symphysis and gonial angle.
• A trabecular pattern is visible which run from coronoid process into ramus and body of mandible.
• Various stress trajectories are because of the effect of muscle attachment.

Major Trajectories

• Origin of trabecular columns occur beneath the teeth in alveolar process and join in a trajectory system.
• Due to this concentration of trabeculae mandibular canal and mandibular nerve are protected.
• Lower border of mandible consists of thick cortical layer of trabeculae which offr high resistance to bending forces.

Question 2. Differentiate infantile swallow and adult swallow.
Or
Differentiate adult swallowing and visceral swallowing.
Answer. Swallowing is an important function carried out by the stomatognathic system.

Infantile/ visceral Swallowing

• The ability to feed from the breast is present in the newborn child.
• Tongue lies between the gum pads
• Mandible is stabilized by obvious contraction of facial muscle especially the buccinator.
• Seen in neonate and gradually disappear with eruption of teeth and growth of mandible.
• The swallow as guided and to a large extent controlled by sensory interchange between lips and tongue.

Adult Swallowing

• Mature swallowing is seen after a year of life.
• The tip of the tongue contact the palatal rugae posterior to the maxillary anterior teeth.
• The mid portion contacts the hard palate
• Posterior aspect assumes a 45° angulation against the posterior pharyngeal wall to permit the bolus of food to move into the digestive tract.
• Facial expression muscles are passive but mandibular elevators are contracted.

Question 3. Write short note on buccinator mechanism.
Or
Write short answer on buccinator mechanism.
Answer.

Buccinator Mechanism

It refers to the continuous band of muscles which surrounds the dentition and are tightly anchored at pharyngeal tubercle of occipital bone.

• Buccinator mechanism begins with decussating fibers of orbicularis muscle which joins the right as well as left fibers of lip. These constitutes anterior component of buccinator mechanism.
• Buccinator mechanism then follows laterally and posteriorly at corner of mouth which joins other fibers of buccinators muscle which are inserted in pterygomandibular raphae.
• At pterygomandibular raphae fibers of buccinators muscle interwind with fiers of superior constrictor muscle and run posteriorly and medially to fi with pharyngeal tubercle.
• All muscles in buccinator mechanism act like a rubber band which tightly surrounds the mandible.

Clinical Significance

• Imbalance in buccinator mechanism causes malocclusion.
• In oral habits such as thumb sucking, tongue thrusting balance between buccinators mechanism and tongue become lost which leads to open bite, increased proclination and constricted maxillary arch.

Question 4. Write short note on Wolff’s law. 
Or
Describe Wolff’s law.
Or
Write short note on Wolff’s law of transformation of bone.
Answer. It is also known as Wolffs law of bone transformation.

• In the year 1870, Julius Wolf explained the reason for the arrangement of trabecular pattern. He attributed the trabecular arrangement pattern to functional stresses.
• A change in the magnitude of force could produce a marked change in the internal architecture and external form of the bone. These changes are accomplished by means of selective resorption of existing bone and resorption of new bone.
• These remodeling changes can take place in the compact bone under periosteum or in trabecular pattern of cancellous bone or on the walls of marrow spaces.
• Increase in function leads to an increase in density of bony trabeculae, while lack of function leads to a decrease in trabecular density. This is called the “Wolffs law.
• Due to such transformation, not only the quantity of bone tissue is kept minimum that would be needed for functional requirements, but also its structure is such that it is best suited for the forces exerted on it.

Question 5. Write short note on infantile swallowing.
Answer. Swallowing pattern in infants is different from adults that’s why it is known as infantile swallow.

• Newborn child has ability to take his/her feed from breast.
• During suckling the nipple is drawn in mouth by negative pressure within.
• Tongue lies over lower gumpad and protrudes between nipple and lower lip.
• Milk is directed continuously to pharynx by automatic peristaltic movement of tongue as well as mylohyoid muscle.
• During all this procedure normal breathing continues.
• Milk passes between faucial pillars and lateral channels of pharynx.
• If excess milk is present in the mouth it dribbles toward the chin.

According to Moyers following are the characteristic of infantile swallow:

• Jaws are apart and tongue is placed between upper and lower gum pads.
• Mandible gets stabilized by contraction of muscles of facial expression and interposed tongue.
• Swallow is guided and controlled by sensory interchange between lips and tongue.

Question 6. Describe the functions of stomatognathic system and add a note on buccinators mechanism.
Answer.

Functions of Stomatognathic System:

• Mastication
• Deglutition
• Respiration
• Speech.

Mastication

Mastication is divided into two parts, i.e.

• Infant feeding, i.e. before teeth eruption.
• Mature or adult mastication, i.e. after teeth eruption.

Infant Feeding:

• Infants have their food by suckling which is an automatic reflex.
• In infants both suckling as well as swallowing occur together as suckle-swallow, this is characterized by caving in the cheeks, bobbing of the hyoid bone, extended head with anterior mandibular thrust and elongated tongue, with lips pursed around the nipple.

Moyers Lists the Features of the Infantile Swallow as:

• Infantile swallow is guided by the lips and tongue.
• Jaws are apart with the tongue placed between the gum pads.
• Mandible is positioned by muscles of the facial expression.

Various Types of Infant Feeding are:

• Breastfeeding: Milk is directed to the pharynx due to peristaltic movement of the tongue.
• Botte feeding: Milk is directly expelled inside the mouth.
• Spoon feeding:
  • Lips are sealed around the edge of spoon to draw food into the mouth.
  • Tongue passes the bolus of food to swallowing between gum pads and erupting teeth.
  • Mature swallowing patterns are observed usually by 18 months of age.

Adult Mastication:

Mastication is defied as the reduction of food in size, changing in consistency, mixing it with saliva and forming into a bolus suitable for swallowing.

Features of adult swallow are:

• Teeth should remain together.
• Mandible should be stabilized through muscles of mastication.

The six stages of mastication as outlined by Murphy:

• Preparatory phase: In this phase ingested food is positioned by the tongue. Now the mandible moves towards the chewing side.
• Food contact phase: As ingestion of food is completed, there occurs a momentary pause in chewing. This is because sensory receptors recognizing the consistency of food.
• Crushing phase: Crushing of the ingested food begins with high velocity and afterwards it slows down.
• Tooth contact phase: As 4-5 strokes of crushing phase get completed, tooth contact occur with change in direction of chewing.
• Grinding phase: In this phase unilateral chewing of food particles occur. While grinding vigorously contact of the maxillary and mandibular molars happens.
• Centric occlusion: This is the last stage now the movement of the teeth comes to an end. After this stage, preparatory stage of the next stroke of mastication begins.

Deglutition

Deglutition is the act or process of swallowing. Fletcher divided the deglutition pattern into four stages:

• Preparatory phase: This phase begins as soon as food is ingested. In this phase bolus is placed in swallow preparatory position and sealing of mouth is done by lips or tongue.
• Oral phase: During oral phase soft palate pull upward and tongue drops downward and backward. Larynx and hyoid shift upward. Muscles of mastication actively stabilizes food. A smooth path is formed for the bolus and solid food is pushed by the tongue and liquid food flows down.
• Pharyngeal phase: It starts as the bolus of food passes through the faucial pillars. Nasopharynx get closed and tongue as well as hyoid bone move forwards.
• Esophageal phase: During this stage food passes via cricopharyngeal sphincter through esophagus to stomach.

Respiration

• Physiologic respiration is the process by which living organisms capture and excrete the gaseous fuel and waste of cellular respiration. In this oxygen get absorbed and carbon dioxide get disposed.
• Mouth and nose combination forms the anatomic beginning of respiratory system.
• Patency of airway in nose as well as oral cavity is maintained by bony skeleton and adaptive posture of tongue.
• In pharynx patency is again dependent on the tone of the muscles of tongue, soft palate and pharyngeal walls.
• Second opening of larynx and closure of epiglotts prevent food from entering the airway.
• Development of respiratory spaces and maintenance of oral and pharyngeal airway space contributes to growth of orofacial bones.

Speech

• Speech is basically a learned behavior.
• Lips, tongue and velopharyngeal structures modify the outgoing breathing stream to produce different variations in speech.
• Four functional subsystems interact in production of speech. The systems are:
  • Respiration: Through this larynx generates speech and voice.
  • Phonation: This lead to sound and production.
  • Resonators: They provide quality to voice.
  • Articulation: It helps in the production of different sounds.
• So speech production is the coordinate action and accurate muscle activity.
• If an articulating structure is affected speech can be affected.