GROWTH
Lecture 2-ORTH 411
Textbook: Premkumar, Sridhar. Orthodontics: Preparatory Manual for
Undergraduates- . Elsevier Health Sciences. Kindle Edition.
Course Coordinator: Ayman Raouf Khalifa
Email: ayman.raoufahme.dent@o6u.edu.eg
Year 2020-2021
Intended learning outcomes (ILOs)
R
Recognize the basis of normal facial growth and development from birth until completion of growth
Post natal growth of the skull
Growth of the skull is divided into:
1. Growth of the cranium:
a. growth of cranial vault.
b. growth of cranial base.
2. Growth of the face:
a. growth of the middle face (naso- maxillary complex).
b. growth of the mandible.
1.a. Growth of the cranial vault:
Follows the neural curve.
1. Bone formation by intramembranous mode i.e. by sutures and bone deposition.
2. At birth the vault is divided by sutures and fontanelles:
• Frontal bone by metopic suture ( no frontal air sinus).
• Mastoid bone is underdeveloped.
• Supraorbital bone is underdeveloped.
3. Inner surface of the vault is under the influence of growth of the brain ( resorption) while deposition occurs on the outer surface.
4. Significance of the sutures is to make birth easy.
5. Most important sutures in the vault are the:
a.Coronal and lambdoid which open during anteroposterior growth.
b.Midsagittal suture opens during lateral growth.
6. Lateral growth of the brain leads to increase in width by expansion of
the suture.
1.b. Growth of the cranial base
• It is attained early by synchondrosis and later by drift ( bone apposition).
the sutures encouraging bone formation on both sides of
• Anteroposterior growth of the cranial base leads to displacement of the maxilla forward thus gives a chance for the maxilla to grow
backward and gives space for the oro- and nasopharynx.
• Vertical growth of the cranial base leaves space for the ramus to grow vertically followed by vertical growth of alveolar processes giving
space for eruption of teeth and elongation of alveolar process.
2a. Growth of the middle face:
• It includes growth of the orbits, nasal cavity, maxillary sinuses, upper alveolar process and palate.
• It follows the somatic curve of growth and meanwhile is related to the cranium which is more developed at birth as it follows the neural
curve.
• The middle face grows in width, depth and height which is the most remarkable.
Growth in width (sagittal growth):
• During the 1st seven years of life growth is by displacement as the skull is divided into two halves by the sagittal suture system
(interpareital, metopic, nasal, middle palatine, symphysis of the mandible and the cranial base cartilage).
• Brain growth and cranial base growth lead to increase in facial width through displacement.
• Union of metopic suture and symphysis makes the frontal bone and mandible respectively continuous bones.
• After seven years neural growth is completed and growth in width is attained by drift rather than displacement.
• Combined lateral growth movements of orbits, nasal walls, maxillary sinuses, and molar region are produced by bone deposition to their
lateral aspects and resorption from their medial surfaces.
Growth in depth (antero-posterior):
• The nasomaxillary complex is attached to the cranial base by a group of sutures: fronto- nasal, fronto-maxillary, fronto-zygomtic,
zygomatico-maxillary, zygomatico-temporal and pterygo-palatine.
• These sutures are aligned that any growth in the cranial base would 2ry displace the middle face forward and downward.
• Bone drift occurs in the following areas:
➢ Lateral orbital rim: backwards.
➢ Zygomatic arch: backwards.
➢ Nasal bone: forward.
➢ Tuberosity : backward.
• There is resorption in the anterior portion of the maxilla and deposition at its back ( posterior growth and anterior movement i.e. 1ry
displacement).
Growth in height:
• Increase in height is most prominent postnataly.
• At birth the nasal and orbital floors are at one level.
• During the first seven years 2ry displacement of the nasomaxillary complex is in a downward direction following growth of the anterior
base cranial base which accounts for half of the vertical growth.
• Growth of the nasal cartilage is downward as a result of increased respiratory demand (functional matrix theory).
• Drift accounts for almost the other half of vertical growth in the midface.
• The nasal floor is resorptive while the palate and alveolar process are depository in nature leading to drift of the naso-maxillary complex
downward.
• The eruption of teeth also causes the alveolar bone to grow forward and downward, therefore the alveolar growth affects the height and
width of the maxilla.
2b.Growth of the mandible:
• At birth the mandible is like a curved bar of bone with short rami, no alveolar or coronoid processes, two carrot shaped condylar cartilages
extending to the mandibular foramina, and the mandibular angle is 175º.
• Condyles grow backwards, upwards and laterally.
• The anterior border of the ramus is resorptive while the posterior border is depository but deposition exceeds resorption thus increasing depth
of the ramus.
• Coronoid process drifts backwards.
• Alveolar process increases in the vertical dimension due to teeth eruption.
• Chin prominance increases by deposition at the chin and resorption just above it.
• The outer surface of the mandible is depository while the inner surface is selectively resorptive (deposition occurs at areas of muscle
insertion).
• Lower surface of the mandible is depository except at the antigonial notch.
Growth changes of the mandible:
1. Uprightening of the ramus accompanied by decrease of the gonial angle from 175 degrees at birth to 120 degrees in adults.
2. Mandibular foramen moves into a more posterior and superior position.
3. Mental foramen moves more posteriorly from below the mesio-buccal cusp of D to be located between roots of the premolars.
4. Increase in inter-ramal width and more prominence of the chin.