Orthodontics Flashcards
Diastema rule for closure
if >2mm, it will not close on its own (not developmental)
close with retainers: TPA/nance/hawley with finger springs or through ortho (do oath first, then cut the frenum)
Closure least likely to occur with early loss of primary CI
upright and stabilize a molar
upright: 6-12 months
stabilize: 2-6 months
via fixed edgewise orthodontic appliance
second molars that are uprighted should be banded, b/c brackets may easily come off from the muscles of mastication
Most difficult to upright: lingually tipped mandibular molar
High angle cases result in excessive VDO (bite opening)
0.018 or 0.022 inch wire
Steps:
- Separate
- Band
- Upright
- crown lengthen
- crown
Mechanism for ortho forces
Heavy Force = early hyalinization (necrosis) and osteoclast resorption of underlying PDL. Delayed movement.
Light Force = little hyalinization and osteoclast resorption on the front side. Earlier movement.
Compression = osteoclast *Main factor in ortho Tension = osteoblast
To have oath movement, you need PDL. Thus, implants are subjected to oath movement no matter how slow.
Mandibular Growth
- Infants have ramus at 1M site.
- Growth occurs at condyle and posterior surface of rams
- Body of mandible grows via periosteal apposition
- Condyle growth via endochondral replacement and surface remodeling on the anterior surface of the ramus
Maxilla growth pattern resembles neural tissue
Mandible pattern resembles genital tissue (grows later)
Most common tooth to have a supracrestal circumferential fibrotomy
Rotated maxillary central incisor
PDL reorganizes in 3-4 months
- Long face predisposes people to what type of malocclusion?
- Short face?
- Class II
2. Class III
Treatment Planning Priority:
- Crossbite: Posterior > Anterior
- impacted teeth
- inter-arch relations > intra-arch relations
- habits
Ideal angles:
- SNA
- SNB
- ANB
Sella Turcica to Nasion THEN from Nation to Point A or B
- SNA = 82 degrees
- SNB = 80 degrees
- ANB = 2 degrees (4 = Class II, 0 = Class III)
Cross bite is most often due to
retained primary teeth
RISK: loss of arch length if not corrected.
Tx: increase space MD of the arch
Retained: Best by the natural dentition of the incisors, not by appliances
Premature exfoliation of primary canines may indicate deficient arch length, leading to a lingual collapse of the incisors.
Anterior crossbites = Reverse overjet = Class III
Posterior cross bites take priority and are the most common type of active tooth movement in PEDO
Scissor bite = lingual cross bite = collapsed mandible with over extended maxilla
Thumb Sucking
Thumb sucking ONLY during the mixed dentition stage causes malocclusion via:
A. increased pressure on buccinators (not negative pressure) → narrow/constricted max arch (expanded arch) → mandible shift to one side on closure → bilateral cross bite
B. max. incisors procline with reclined mand. Incisors → anterior open bite → Class II Malocclusion
Results: cross bite anterior open bite (collapsed arch) proclaimed max incisors Retroclined mand. incisors class II
Tx: palatal expander (TPA, Hawley, Hyrax, Quad-helix, Haas) turned every 1-2 months. Need 3 months to stabilize.
Most common:
- Anterior open bites
- Deep Bites
- Class III
- Blacks - mostly asymmetrical
- Whites
- Asians
Class III are rare in the U.S. than Class II
Tongue Thrust
open bite
Skeletal vs functional cross bite
Skeletal corset will show a smooth transition in CO/MI.
Functional corset occurs from thumb sucking, where the patient will tend to function on one side during closure.
Moyer’s Analysis
- MD width of MAND. Incisors (Max incisors show too much unpredictability in size for PEDO)
- mixed dentition analysis
most common cause of Class I malocclusion
tooth size and supporting bone (length) discrepancy
Class I (70%) > Class II (20%) > Class III
Class III “subdivision” means you have a class III on one side and a class I on the other
When both jaws are protruded, you will see lip incompetence, lip opening and lip strain.
