An introduction to facial growth and development by DrNayAung

1. An intr oduction to
facial g r owth and development
Nay Aung, BDS PhD
28.12.2022

2.  Facial growth and development is a complex three-dimensional process occurring until the
late teens and then to a small extent in adulthood.
 Growth refers to an increase in tissue size as a result of cellular hypertrophy, hyperplasia, an
increase in extracellular volume or a combination of these factors.
 Development refers to an increase in tissue organization and specialization.
 It is essential that the reader appreciates that there is tremendous individual variation in the
timing, magnitude and direction of facial growth.
An introduction to facial growth and development

3.  An understanding of normal facial growth and development is important to an orthodontist
for several reasons:
 Understanding the aetiology of malocclusion;
 Recognition of abnormal growth patterns;
 Treatment timing (e.g. functional appliances, orthognathic surgery);
 Understanding factors influencing treatment stability.
The importance of understanding facial growth

4.  The skull can be divided into two main components:
 Neurocranium (cranial vault and cranial base);
 Viscerocranium (facial skeleton).
 The neurocranium has an important role in supporting and protecting the brain, and provides
a passageway for nerves and blood vessels.
 The viscerocranium is particularly important for mastication, respiration and supporting the
eyes.
Components of the skull

5.  Four processes are important during normal growth and development of the craniofacial
skeleton:
 Endochondral ossification;
 Intramembranous ossification and sutural growth;
 Surface remodeling;
 Primary and secondary displacement.
Processes involved in skeletal growth
(A) The four main processes involved in growth
and development of the craniofacial complex.

6. (A) The four main processes involved in growth
and development of the craniofacial complex.

7.  Endochondral ossification is the process in which bone develops from a cartilaginous
precursor.
 Cartilage is well adapted to undergoing compressive loading because of its avascular nature.
 Therefore, it is a good precursor in loaded areas such as the long bones, cranial base and
mandibular condyle.
 Intramembranous ossification is a process in which bone is formed by osteoblasts present in
mesenchymal tissue.
 It is an important mechanism of bone formation in non-weight-bearing areas such as the
cranial vault, mandible and maxilla.
Processes involved in skeletal growth

8.  Surface remodeling refers to the deposition and resorption of bone by the periosteum and
endosteum.
 It alters the shape and size of individual bones and is important during growth and
development of the entire facial skeleton.
 Primary displacement refers to the change in position of a bone by its own enlargement.
 Secondary displacement occurs when the position of a bone is changed because of growth of
an adjacent attached bone.
 For example, growth of the cranial base has an important secondary displacing effect on the
position of the maxilla.
Processes involved in skeletal growth

9.  Facial growth and development is dependent on the interplay between genetic potential and
environmental influences.
 There has been much debate about which tissues have the genetic programming to control
facial growth.
 The following have being suggested:
 Bone;
 Cartilage;
 Soft tissues.
The control of facial growth

10.  Many lines of evidence suggest it unlikely that osteoblasts and osteoclasts within bone hold
the genetic programming to determine the magnitude, direction and timing of skeletal
growth.
 Instead, it is accepted that the periosteum and sutures provide adaptive responses to external
influences.
 Another popular theory is that the cartilages within the skull are the pacemakers of facial
growth.
 It is suggested that the condylar cartilage and synchondroses grow to a genetically
predetermined length and are replaced by bone, and thereby influence growth of the
craniofacial skeleton.
The control of facial growth

11.  Experimental and clinical evidence indicates that growth of the condylar cartilage is not
genetically predetermined, and like that of the sutures it is adaptive.
 In contrast, the cranial base synchondroses and the nasal septal cartilage have some genetic
pre-programming that influences the magnitude of future growth.
 Growth of the cartilaginous nasal septum may be important for maxillary growth because it
may place a downwards and forwards displacing force on the maxilla, creating tension across
the maxillary sutures, leading to bone deposition and growth.
The control of facial growth

12.  The functional matrix theory suggests that the genetic control of facial growth resides in the
soft tissues enveloping the craniofacial skeleton.
 The skull is said to consists of various skeletal units which are associated with a functional
matrix whose activity determines the size, shape and position of the unit.
 Two types of functional matrix have been suggested:
 Capsular matrices (e.g. neurocranial capsule, oro-naso-pharyngeal capsule);
 Periosteal matrices (e.g. muscle and tendon attachments, teeth).
The control of facial growth

13.  Growth of capsular matrices causes displacement of the associated skeletal units.
 For example, growth of the brain causes outward displacement of the cranial vault, and
enlargement of the airway may lead to downward and forward displacement of the maxilla
and mandible.
 Growth of the periosteal matrices is thought to influence the size and shape of the associated
skeletal unit.
 For example, muscular pull and tooth eruption result in development of muscular processes
(e.g. coronoid process) and the alveolar process, respectively.
 Although the exact mechanism of facial growth control is not understood, current thinking
supports the functional matrix theory and that some genetic control resides within the cranial
base synchondroses and nasal septal cartilages.
The control of facial growth

14.  Because of tremendous individual variation, it is not possible to predict the magnitude and
direction of future facial growth, and chronological age cannot be used to predict the onset of
the adolescent growth spurt.
 Some cephalometric features can help in predicting the likely direction of future mandibular
growth rotations, however, these are not entirely reliable.
Growth prediction
(B) Various cephalometric features can indicate the likely direction of mandibular growth rotation.
These features include the lower anterior face height, the shape of the lower border of the mandible, the inclination
of the mental symphysis, inclination of the condylar head and curvature of the mandibular canal.

15.  Concerning timing, mandibular growth follows the general body pattern of skeletal growth
which accelerates at puberty.
 Hence, serial statural height measurements and the presence of secondary sexual
characteristics can help determine the onset and stage of the pubertal growth spurt and
associated acceleration in mandibular growth.
Growth prediction
(C) The general pattern of skeletal and neural growth is
illustrated (Scammons curves).
Mandibular growth has some similarity to the general
skeletal growth pattern.

16. (D) This figure shows the height curve for males.
The average growth curve (50th centile) as well as
curves between 3rd and 97th centile are shown.
The pubertal growth spurt is marked as well as the
secondary sexual characteristics that may be present at
the beginning and end of the spurt.
At least three consecutive measurements (red crosses)
are required to estimate with reasonable accuracy that
growth curve any particular patient maybe following.

17.  The information can be helpful in timing the start of functional appliance treatment.
 The growth spurt that accompanies puberty can be expected at the age of 14±2 years in boys
and 12±2 years in girls.
 The average duration of the growth spurt in boys and girls is 3.5 and 2 years, respectively.
 These figures are variable, both within and between populations.
Growth prediction

18. Thank you so much for your kind attention.