Functional Development Question And Answers

Functional Development

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.

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• 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.