Growth and Orthodontic Treatment

Question 1

What is the definition of growth?

Answer 1

An increase in size and number

Question 2

What is the definition of development?

Answer 2

Implies an increase in specialisation or function

Question 3

What is the definition of growth centre?

Answer 3

Where independent growth occurs (genetically determined)

Question 4

What is the definition of endochondral ossification?

Answer 4

Bone develops from cartilaginous precursor, seen in the long bones of the limbs and cranial base

Question 5

What is the definition of intramembranous ossification?

Answer 5

Bone is formed by osteoblasts present in mesenchymal tissue

Takes place in mandible, maxilla and cranial vault

Question 6

What is the definition of surface remodelling?

Answer 6

Process of resorption and deposition of bone which allows the size and shape of facial bones to change

Question 7

Describe the definition of primary displacement

Answer 7

Change in position is caused by bone itself changing in size

Question 8

Describe the definition of secondary displacement

Answer 8

Caused by the growth of an adjacent bone - such as in the change in the position of maxilla due to growth of the cranial base

Question 9

Name 2 components which controls the timing and extent of growth

Answer 9

1. Genetics

2. Environment

Question 10

Describe Moss’s Functional Matrix Theory

Answer 10

Growth of the face is determined by growth of soft tissues i.e orbit increases as eye grows, cranium increases as brain grows

Question 11

Describe the Cartilagenous Theory of craniofacial growth

Answer 11

Proposes cartilage as the primary determinant of growth

Question 12

Describe the implications of growth on orthodontic treatment

Answer 12

• Majority of orthodontic treatment carried out on individuals who are growing
• Many authorities studying growth emphasis variation in amount and direction of growth

Question 13

Name 3 growth problems which may be present in orthodontic cases

Answer 13

1. Severe skeletal II (insufficient growth of mandible)
2. Severe skeletal III (excess growth on mandible)
3. Severe skeletal open bites (excess vertical growth)

Question 14

Describe 4 headings under which orthodontic implications of growth may be consdiered

Answer 14

1. What changes are likely due to growth?
2. Can the orthodontist influence growth?
3. Can the orthodontist make use of growth?
4. Growth prediction

Question 15

Describe growth of the cranial vault

Answer 15

• Cranial vault composed of squamous parts of parietal, frontal, temporal and occipital bones
• Cranium grows as brain grows
• Growth is sutural and appositional
• All intramembranous growth

Question 16

Name 4 components of the cranial base

Answer 16

1. Occipital
2. Sphenoid
3. Ethmoid
4. Frontal

Question 17

Name 2 pieces of chondrocranium present at birth

Answer 17

1. Spheno-occipital synchrondrosis

2. Nasal cartilage

Question 18

Describe the growth of the cranial base

Answer 18

• Anterior cranial base (apart from thickness of frontal bone) is finished growing at around 8-10 years
• Area used as reference to evaluate growth in other areas
• Base grows in intermediate fashion between calvarium and face

Question 19

Describe how the bones are arranged to make up the cranial base, including explanations of anterior and posterior

Answer 19

• Anterior base is made up of frontal, ethmoid and anterior part of sphenoid and includes the SES (fuses 6-7 years)
• Posterior base is made up of posterior part of sphenoid and occipital and includes SOS (grows until 13-15F / 15-17M)

Question 20

Describe maxillary growth

Answer 20

• Predominant enlargement is posterior and superior, with downward and forward displacement
• Processes are primary and secondary displacement, intramembranous ossification and surface remodelling
• Deposition of bone on ridges increases face height

Question 21

Describe the effect of teeth on maxillary growth

Answer 21

• Growth is reduced without presence of teeth

- Mouth breathing where teeth are not in contact or edentulous patients will show reduced vertical growth

Question 22

Describe 3 types of maxillary growth which occurs

Answer 22

1. Maxillary displacement
2. Tuberosity growth (increase arch length for molars)
3. Inferior relocation of palate

Question 23

Describe the V-principle of growth

Answer 23

Infiltrating bone in the middle of the palate causes lateral displacement of bone which widens the arch

Question 24

Describe condylar growth

Answer 24

• Site of growth but not growth centre
• Condyle does not establish rate or amount of growth
• It is adaptive

Question 25

Name 2 methods of growth in the mandible

Answer 25

1. Endochondral in the condylar region

2. Intramembranous at other growth sites

Question 26

Describe the predominant growth trend in the mandible

Answer 26

Posterior and superior growth, which displaces the mandible downward and forward

Question 27

Describe the posterior relocation of the ramus of the mandible

Answer 27

Deposition of bone on posterior aspects of ramus and resorption of bone on anterior aspect of ramus causes remodelling in a posterior direction which lengthens the dental arch

Question 28

Describe chin button growth

Answer 28

Depository on the chin with resorption at B point

Question 29

Describe how orthodontics influences growth

Answer 29

Dentoalveolar effect of orthodontic treatment is beyond argument however whether orthopaedic effects are produced is open to debate

Question 30

Describe 5 orthodontic situations which rely on growth

Answer 30

1. Functional appliance treatment
2. Distal movement of posterior teeth
3. Overbite reduction
4. Spontaneous space closure following extraction
5. Occlusal settling

Question 31

Describe how orthodontists can influence the growth of the maxilla

Answer 31

It is possible to influence growth and position of maxilla using reverse pull headgear, however, there is limited evidence to support long term skeletal effects

Question 32

Describe how orthodontists can influence the growth of the mandible

Answer 32

Functional appliances may produce favourable growth in some cases or restrict maxilla slightly but the majority of the effect is dentoaveolar

Question 33

Describe the best way orthodontists can make use of growth

Answer 33

Periods of rapid facial growth are favourable to orthodontic treatment, as they assist in overbite reduction and spontaneous space closure

Question 34

Describe how rapid facial growth is favourable for reduction of overbites

Answer 34

• Biteplane used to prevent posterior teeth from contacting
• During rapid growth, posterior teeth with overerupt and contact in higher position
• This will reduce the overbite

Question 35

Describe growth prediction and completion

Answer 35

• Accurate individualised growth prediction is not possible
• Best is to add average values adjusted for age and sex
• To check if growth is complete, possible to look for superimposition of 2-3 cephs over 18-24 month period