Growth and Orthodontic Treatment Flashcards
What is the definition of growth?
An increase in size and number
What is the definition of development?
Implies an increase in specialisation or function
What is the definition of growth centre?
Where independent growth occurs (genetically determined)
What is the definition of endochondral ossification?
Bone develops from cartilaginous precursor, seen in the long bones of the limbs and cranial base
What is the definition of intramembranous ossification?
Bone is formed by osteoblasts present in mesenchymal tissue
Takes place in mandible, maxilla and cranial vault
What is the definition of surface remodelling?
Process of resorption and deposition of bone which allows the size and shape of facial bones to change
Describe the definition of primary displacement
Change in position is caused by bone itself changing in size
Describe the definition of secondary displacement
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
Name 2 components which controls the timing and extent of growth
- Genetics
2. Environment
Describe Moss’s Functional Matrix Theory
Growth of the face is determined by growth of soft tissues i.e orbit increases as eye grows, cranium increases as brain grows
Describe the Cartilagenous Theory of craniofacial growth
Proposes cartilage as the primary determinant of growth
Describe the implications of growth on orthodontic treatment
- Majority of orthodontic treatment carried out on individuals who are growing
- Many authorities studying growth emphasis variation in amount and direction of growth
Name 3 growth problems which may be present in orthodontic cases
- Severe skeletal II (insufficient growth of mandible)
- Severe skeletal III (excess growth on mandible)
- Severe skeletal open bites (excess vertical growth)
Describe 4 headings under which orthodontic implications of growth may be consdiered
- What changes are likely due to growth?
- Can the orthodontist influence growth?
- Can the orthodontist make use of growth?
- Growth prediction
Describe growth of the cranial vault
- 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
Name 4 components of the cranial base
- Occipital
- Sphenoid
- Ethmoid
- Frontal
Name 2 pieces of chondrocranium present at birth
- Spheno-occipital synchrondrosis
2. Nasal cartilage
Describe the growth of the cranial base
- 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
Describe how the bones are arranged to make up the cranial base, including explanations of anterior and posterior
- 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)
Describe maxillary growth
- 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
Describe the effect of teeth on maxillary growth
- Growth is reduced without presence of teeth
- Mouth breathing where teeth are not in contact or edentulous patients will show reduced vertical growth
Describe 3 types of maxillary growth which occurs
- Maxillary displacement
- Tuberosity growth (increase arch length for molars)
- Inferior relocation of palate
Describe the V-principle of growth
Infiltrating bone in the middle of the palate causes lateral displacement of bone which widens the arch
Describe condylar growth
- Site of growth but not growth centre
- Condyle does not establish rate or amount of growth
- It is adaptive
Name 2 methods of growth in the mandible
- Endochondral in the condylar region
2. Intramembranous at other growth sites
Describe the predominant growth trend in the mandible
Posterior and superior growth, which displaces the mandible downward and forward
Describe the posterior relocation of the ramus of the mandible
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
Describe chin button growth
Depository on the chin with resorption at B point
Describe how orthodontics influences growth
Dentoalveolar effect of orthodontic treatment is beyond argument however whether orthopaedic effects are produced is open to debate
Describe 5 orthodontic situations which rely on growth
- Functional appliance treatment
- Distal movement of posterior teeth
- Overbite reduction
- Spontaneous space closure following extraction
- Occlusal settling
Describe how orthodontists can influence the growth of the maxilla
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
Describe how orthodontists can influence the growth of the mandible
Functional appliances may produce favourable growth in some cases or restrict maxilla slightly but the majority of the effect is dentoaveolar
Describe the best way orthodontists can make use of growth
Periods of rapid facial growth are favourable to orthodontic treatment, as they assist in overbite reduction and spontaneous space closure
Describe how rapid facial growth is favourable for reduction of overbites
- 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
Describe growth prediction and completion
- 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
