Ortho Revision
Terms
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- Prioritised reasons for orthodontic treatment
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1. Reduce psychosocial impact
2. Improve oral function
3. Adjunct to disease control - Risks of TMD
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Unilateral crossbite with a shift - 16%.
Class III, etc. - 9%
Normal occlusion - 5% -
Normal:
OJ
OB -
OJ = 2-3mm
OB = 1-2mm - Prevalence of malocclusion
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normal - 35%
Class I - 45%
Class II - 15%
Class III - 1-3%
Crossbite - 5%
Deep bite - 12% (rare in blacks)
Open bite - 1% (10% in blacks) - Who seeks orthodontic treatment?
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People with malocclusion - 65%
Dentists - 55%
Lay person - 35%
Would seek treatment if it was free - 50% - Known causes of malocclusion
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1. Hereditary
2. Developmental
3. Trauma
4. Function - Inhereted factors of malocclusion
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No more than 50% are inherited.
Certain types have a strong inheritance component - mandibular prognathism. - Developmental processes causing malocclusion
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Disturbances of embryological development:
- Causes of malocclusion
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1. Facial form and congenital abnormalities.
2. Postnatal growth disturbances.
3. Inherited facial disproportions.
4. Environmental causes - Facial form and congenital abnormality - hemifacial microsomia
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Congenital defect. Ectomesenchymal tissue fails to migrate to side of face - lack of tissue = changes in shape and form of face.
Usually unilateral (10% bilateral)
Chin deviated to side of defect.
Upper jaw affected as grows in response to lower jaw. Dentition may be affected. Fudimentary ear.
Possibly due to rupture of the stapedial artery during transition from bilateral carotid to unilateral carotid - Postnatal - Hemimandibular hypertrophy
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Unilateral excessive growth of the mandible during and after puberty. Abundant tissue in the condyle and possibly ramus on one side. Chin deviates as child grows. Dentition influenced.
Maxilla affected as follows mandibular growth. - Inherited - Class III
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Hapsberg prognathic mandible (spanish monarchs all had protrusive mandible).
Class III relationships show greatest hereditary relationship
Genetics can only explain 49% of variation - Environmental causes - trauma to condyle
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Condylar fracture:
-75% recover fine
-25% get ankylosis of condyle.
Scarring restricts movement of the affected condyle resulting in impaired development on that side. Condyle is a major growth site. - If a facial form analysis shows that the incisors are protrusive, then the crowding from space analysis will be...
- Underestimated.