Postnatal growth of the craniofacial region

Question 1

How does the height-velocity curve change throughout the life course?

Answer 1

There is a rapid rate of growth at birth, which progressively decelerates until around 3 years of age.
Slowly decelerating phase persisting until the adolescent spurt in the early teenage years, and is interrupted by a brief juvenile growth spurt at 6-8 years of age.
An adolescent growth spurt, followed by a progressive deceleration in growth velocity until adulthood.

Question 2

How does the skull of a neonate differ from that of an adult?

Answer 2

• Face of the neonate is disproportionately small due to a poorly developed nasal cavity, maxilla and mandible. The reduced size is compounded by the relative enormity of the cranial vault and orbits
• Individual bones within the neonatal skull are smaller than those of adults, with exception to the ear ossicles
• 6 fontanelles or fibrous membranes are present in the neonatal skull - these provide flexibility to the skull as it passes through the birth canal, close by 18 months of age
• Additional sutures present in the neonatal skull, including the metopic suture within the frontal bone, and the symphyseal suture within the mandible
• The spheno-occipital synchondrosis - cartilaginous growth plate present between the basilar region of the occipital bone and the body of the sphenoid. This is a significant growth centre, persisting until the second decade

Question 3

Endochondral bone growth occurs through…

Answer 3

Cartilaginous replacement

Question 4

Intramembranous bones grow as a result of…

Answer 4

Periosteal remodelling

Question 5

What occurs as a result of growth in the craniofacial region?

Answer 5

• Relocation - takes place via differential changes in both size and shape, mediated by surface deposition and resorption
• Displacement of individual bones - independent process, often occurring simultaneously to relocation. It is mediated by soft tissues, which apply external forces on the bones, resulting in their displacement

Question 6

What is the cranial vault composed of?

Answer 6

It is composed of squamous parts of the frontal, temporal, occipital, and paired parietal bones.

Question 7

The intramembranous bones of the cranial vault grow in which 2 ways?

Answer 7

1. Compensatory growth of bone at the sutures
2. Surface periosteal and endosteal remodelling

Question 8

Which mechanisms are used to achieve post-natal growth of the cranial base?

Answer 8

1. Endochondral growth
2. Surface remodelling

Question 9

What are synchondroses and what is their main function?

Answer 9

They are isolated regions of cartilage, which persist in the cranial base and make significant changes to this area during post-natal growth.

Function: Mediate pressure-adapted primary endochondral growth and act directly to increase the anteroposterior dimension of the skull base.

Question 10

Which synchondroses make the most significant contributions to the post-natal growth of the cranial base?

Answer 10

The spheno-ethmoidal and spheno-occipital synchondroses

Question 11

Which synchondroses ossifies at the age of 7?

Answer 11

The spheno-ethmoidal synchondroses

Question 12

Which synchondroses persists for longer before ossifying?

Answer 12

The spheno-occipital synchondroses

Question 13

How does the mandible grow?

Answer 13

The mandible grows downwards and forwards in relation to the cranial base and is achieved by:
1. Bony remodelling via subperiosteal resorption and deposition
2. Cartilaginous growth at the condyle

Question 14

Mandibular rotations can occur in either…

Answer 14

A forward or backward direction

Question 15

Forward rotations are associated with centres of rotation through the…

Answer 15

Condyles, incisors and premolars

Question 16

Backward rotations are associated with centres of rotation through the…

Answer 16

Condyles or the most distal-occluding molars

Question 17

What do the different rotations of the mandible represent?

Answer 17

They represent an imbalance in growth between the anterior and posterior face height

Question 18

What results in a total backward growth rotation of the mandible?

Answer 18

An excess of growth in anterior face height

Question 19

What results in a total forward growth rotation of the mandible?

Answer 19

An excess of growth in the posterior face height

Question 20

What could be the effect of extreme rotations of the mandible?

Answer 20

There could be an effect on the eruptive paths of the teeth as well as an effect on the skeletal relationships of the jaws.

Question 21

What is dentoalveolar compensation?

Answer 21

This is a compensatory mechanism which attempts to maintain a normal interarch occlusal relationship despite variation in the skeletal pattern.

Question 22

Which factors are responsible for dentoalveolar compensation?

Answer 22

1. Normal mechanisms of tooth eruption
2. Soft tissue forces
3. Occlusal forces and mesial drift