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What is a growth center?
- Area believed to be under genetic control
- Exhibits 'tissue-separating capabilities'
- Dictates how much growth and in which direction
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What is a growth site?
- Not necessarily under genetic control
- Active skeletal growth occurs in a secondary compensatory manner
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What is the remodeling theory?
- Periosteum is the target of genetic activity
- Bone only added appositionally at surfaces
- Jaw growth characterized by bone deposition at posterior surfacesCalvarial growth occurs by deposition on ectocranial surfaces and resorption on endocranial
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What is the sutural theory
- Sutures and CT are the primary targets of genetic activity
- Proliferative activity in the cells of the sutural tissues
- Endochondral bones grow at epiphyseal plates
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What is the nasal septum theory?
- Cartilage is the primary target of genetic activity
- Cranial base, nasal septum, mandibular condyles drive growth
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What is the functional matrix hypothesis?
- Soft tissues are primary targets of genetic activity
- Skeletal structures grow in response to extrinsic environment
- Functional cranial components (ex: eye guiding socket)
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What is the servosystem theory?
- Nasal septum and cranial base are primary targets of genetic activity
- Condylar growth is secondary
- Combination of nasal septum and functional matrix theory
- Our best explanation for how things work
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How much do we really know about growth control?
- Unknown for certain, just theories currently
- Revealed by findings in developmental molecular bio
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What is similar between a 6 year old and adult body?
Proportion (limbs are lengthening)
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When are neural and cranial growth nearly complete?
By age 12
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Which grows faster, jaw or cranium?
Beyond age 5 to 15 there is more facial growth than cranial growth
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Craniofacial growth chart
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What occurs on the maxillary surfaces from 6-12?
- Resorptive remodeling on anterior surfaces
- Continued apposition at maxillary suture
- Increase in transverse dimension
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What is late mesial shift?
Closing of interpximal space on exfolation of primary 1st molars
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How much arch length decrease in Late mesial shift? Leeway space in each arch?
- Arch length decreases 2-3mm
- Maxillary leeway space=2.2mm
- Mandibular leeway space=4.8mm
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Which direction does the molar relationship head toward in late mesial shift?
Toward Class I
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Possible shiftings of teeth from primary molar relationships
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What does distal step develop into?
Class II molar relationship
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What does flush terminal plane develop into?
Class I and Class II almost evenly
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What does mesial step >2mm develop into?
Mostly class I, some class II and class III
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What happens to arch length as you head toward permanent dention?
It decreases (primary molars bigger than perm premolars)
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What happens to intercanine distance as you get older?
Intercanine distances increases, esp with maxillary canine
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Canine eruption diagram 7,9,14 years
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Eruption sequence for permanent teeth
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What are the three major problems of mixed dentition?
- Skeletal/Dental Class II
- Posterior Crossbite
- Crowding
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What are the treatment options for crowding?
- Less than 4mm: Non-extraction
- 5-9mm: Non-extraction or extraction (esthetics, incisor position)
- Greater than 10mm: extraction
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In mixed dentition, can we measure space available? Required?
You can measure space available, but NOT space required
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What is the direct measurement technique for space?
- Usually done on radiographs for unerupted teeth
- True width on model/width of erupted on radiograph = true width unerupted/width on radiograph
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What is the Tanaka and Johnston method?
- Predicts unerupted permanent canines and premolars
- Estimated width of mandibular canine and premolars in one quadrant= 1/2 mesiodistal width of four lower incisors +10.5mm
- or +11mm for maxillary canine and premolars
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What are Moyers prediciton values?
- Predicts unerupted permanent canines and premolars
- Uses ratio of mandibular incisor widths to canine/premolar widths
- Mandibular incisors must be erupted
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What are some ways to address crowding in the mixed dentition?
- 1. Hold Leeway Space
- 2. Gain space- separation
- 3. Serial extaction
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