Ortho Flashcards
What way can fixed appliances move teeth?
3 planes (3d)
What appliances are more anchorage demanding?
Fixed
What 3 movements can fixed appliances make?
Tipping
Bodily movement
Torque
What are indications for fixed appliances?
Multiple tooth movements needed
Rotations
Bodily movement
Space closure (extractions or hypodontia)
Lower arch treatment
What are contra-indications for fixed appliances?
Poor OH
Active caries
Poor motivation
Good dietary control - avoid hard/sticky foods, restrict sugars and acids
What are risks of fixed appliances?
Decalcification
Root resorption
Loss of periodontal support
TMJ dysfunction
Failed tx & relapse
Reversible risks - pain, ulcerations etc
What are the 2 types of fixed attachments ?
Bands
Bonds/brackets
When would bands be placed instead of brackets?
Usually on molars or premolars or teeth with ceramic crowns
What is pre-adjusted edgewise fixed appliance?
One we use - slot, base and tie wing
Built in adjustments for individual teeth
What are standard edgewise brackets?
Brackets that require arch wire bends to produce ideal tip
What are the 3 phases of active treatment?
Levelling and aligning
Major tooth movement - correction of overjet and overbite, space closure, centre line correction
Finishing - detailed alignment
Describe the alignment phase? (Wires etc)
Light flexible arch wires, changed each visit
Wires of increasing stiffness
Deformation energy dissipates as wires straighten and pull teeth into alignment
Each new wire is deformed less but has higher deformation energy
What are the properties of NiTi wires
High flexibliity
Deliver a low force over a long range
Shape memory
What is used for major tooth movements?
Stainless steel wires
What are sliding mechanics?
When teeth are pushed or pulled along the arch wire by:
- power chain
- coil springs
- elastic bands
What metals are in SS wires?
Iron
Chromium
Nickel
What are the properties of SS wires?
Stiff
Resist deformation
Supports teeth as they move along the wire while closing space
What is used during finishing stage?
Lighter wires to allow occlusal setting
Fine adjustments to bracket position
Bends to arch wire
Elastics
What are the active components of removable appliances?
Springs
Biteplanes
Screws
Bows
What are the passive components of URA’s?
Retainers - e.g. Hawley
What are the different types of URA?
Interceptive appliance
Space maintainer
Pre-surgical orthopaedics (cleft care)
Active plate
Retainer
Functional appliance
What are the advantages of URA’s?
Can be removed for OH and sports
Increased anchorage
Easy to adjust
Less iatrogenic damage
Baseplate can be modified
Good at moving blocks of teeth
Passive if needed
Cheaper
What are the disadvantages of URAs?
Need good pt compliance
Limited movements - tipping
Affects speech
Technician required
Lower appliances difficult to tolerate
Inefficient at multiple tooth movements
What size are springs wire on URA?
0.5mm for single tooth
0.7mm for groups of teeth
What are springs made of on URA?
18/8 austenitic stainless steel
what force should be applied by springs for single tooth movement?
25 - 40 grams per tooth
where should a spring be placed on a tooth?
close to the gingival margin to reduce tupping tendency to minimum
give 4 examples of springs for URA
palatal finger springs
buccal canine retractors
z springs
t springs
what 2 movements can screws in baseplate make?
expansion
distilisation
how much seperation does 1/4 turn of a screw cause?
0.25mm
what are the disadvantages of screws?
bulky
expensive
what claps can be used for retention?
Adam’s or delta cribs - molars and premolars
Southend and C clasps - incisors
Ball hooks - interdental embrasure
what size/material are adams/delta cribs?
molars - 0.7mm ss round wire
premolar/deciduous - 0.6mm
what size/material are southend clasps?
0.6 or 0.7mm wire
what size/material are ball hooks?
0.7mm wire with soldered ball on end
how do adams clasps work?
engage undercuts at the mesial and distal corners of the edges
should engage 1mm of undercut
describe anchorage
for every action there is an equal and opposite reaction
resistance to unwanted tooth movement
how can we reinforce anchorage with URAs?
clasp more teeth
move only 1 or 2 teeth at a time
use lighter forces
occlusal capping
add headgear
how does a baseplate support anchorage?
palatal coverage
are baseplates active or passive?
can be both
what details should you give the lab for URA construction?
what appliance is for
retention components
active components
baseplate modifications
drawing of design
what would you see in the mouth if pt is wearing URA?
palatal mucosa should have indentation or redness
what would you look for in review appt of URA?
slightly mobile teeth if movement is occurring
if teeth are not moving, look for a cause (acrylic in the way, insufficient activation of springs, unerupted teeth, retained roots)
what should be done to URA at review appts?
reactivated 1-2mm and tighten cribs
how much tooth movement should occur each month with a URA?
1mm
why is it necessary to reduce the overbite before reducing the overjet?
as incisors tip, the lower incisors prevet further overjet reduction due to increasing overbite
what can be added to URA to allow overjet to be reduced without increasing the overbite?
anterior bite plane
what type of bone formation leads to formation of maxilla and mandible?
intra membranous
describe intra membranous bone formation
mesenchymal cells - differentiation- osteoblasts - calcification = bone
what type of bone formation makes condylar cartilage and nasal septum cartilage?
endo chondral
describe endochondral bone formation
cartilage cells - hypertrophy - calcified matrix - osteogenic invasion = bone
describe growth of the mandible
area on condensation above ventral part of developing mandible
develops in cone shaped cartilage
migrates inferior & fuses with mandibular ramus
cone shaped cartilage replaced by bone but upper end persists acting as growth cartilage
describe development of the maxilla
remodelling - deposition and resorption occurring on opposite ends
progressively changes the size of whole bone
sequentially relocate each component of the whole bone
how do functional appliances work?
stretch muscles of mastication
posture mandible
differential tooth eruption
what are the skeletal effects of functional appliances?
places a backwards force on the maxillary arch
accelerates condylar growth
redirects condylar growth
what are the dentoalveolar effects from functional appliances?
retracts upper teeth
proclines lower teeth
different rates of tooth eruption
when are functional appliances most effective?
best success in:
mild to moderate increase in overjet (upto 11mm)
increase in overbite
active facial growth
willingness to comply
what are the indications for functional appliances?
motivated patient
pre-adolescent growth phase
skeletal discrepancy mild to moderate
increased overjet/overbite (if class ii)
proclined maxillary incisors (if class ii)
well aligned arches
what are contra-indications for functional appliances?
poor motivation
age >14
poor dental health
condylar disease (juvenile rheumatoid arthritis)
proclined lower incisors
what are advantages of functional appliances?
removable (easy to clean)
may avoid extractions
accelerates skeletal growth
reduces incidence of trauma
early treatment
economical
less damage to tooth tissue
what tooth tissue damage is reduced with functional appliances?
root resorption
chance of decalcification
effect on bone levels
what are disadvantages of functional appliances?
compliance
lack of detailed tooth movements
candidosis with removable appliances
when would only a functional appliance be used?
skeletal class ii cases with aligned arches
when would you use functional and fixed appliance?
skeletal class ii plus irregularity/crowding
how do you assess if a pt needs treatment?
clinical judgement
iotn
how do you assess if the pt wants treatment?
motivation
cooperation
how do you assess if its the right time for tx?
dental stage
growth
motivation
how do you assess what type of tx is needed?
visualise tooth movements required
space analysis
appliance type
what sources of space are there?
extractions
increased arch length
increased arch width
interproximal reduction
what space requirements need extractions?
0-4mm = non-extraction
4-8mm = borderline
8+mm = extractions
How would you decide for XLA in borderline cases?
Side profile
Skeletal pattern
Class I div 2
MH
Why are premolars favourite choice of XLA for ortho?
No aesthetic impact on smile
Space near to crowding
Straight forward XLA
Molars good anchorage
When would you extract 4’s?
When most space required
When canines are crowded
When would you extract 5’s
When less anterior crowding
Allows molars to move forward
Why are 6’s not routines extracted for ortho
Hard xla
Provides little space anteriorly
Long tx
When would you choose to extract the 6’s
When poor quality - caries/large restorations
When would you extract 1 lower incisor
Class 3 malocclusion
Lower incisor crowding
Severe rotation
Severe displacement
When would uppers 2s be extracted
Very palatally displaced
Trauma
Contra lateral tooth congenitally absent/peg
Canine has good shape/size/colour
When would upper 3’s be extracted
Ectopic
Only when upper 4 is in good position
When would upper 1’s be extracted
Trauma
Dilaceration
Ectopic
Why are lower 3’s a bad choice for xla
Poor contact point 2-4 leads to long term perio problems
What non-orthodontic factors are considered when planning XLA cases
Tooth quality - hyperplasticity
Pathology - caries/pulp path/perio
Congenitally absent teeth
Abnormal shape
Difficult XLA
What is considered when choosing retention regimen?
Likely stability of result
Initial malocclusion
OH
Compliance
Pt preference
Name 3 types of retainer
Vacuum/pressure formed (VFR/PFR) - Essix
Hawley
Bonded (DBR)
What is the role of GDP in ortho work
Identify - exam/refer/IOTN
Maintain OH
Ortho first aid
Retention
What would you include in an ortho referral letter
Urgency
Suitability of pt
Whether malocclusion is suitable for tx by particular orthodontist/practice (IOTN)
Pt details
Reason & complaint
MH
OH levels
Trauma
SH
Motivation
Summary of malocclusion
What order do lower permanent teeth erupt
6, 1, 2, 3, 4, 5, 7, 8
What order do upper teeth erupt
6, 1, 2, 4, 5, 3, 7, 8
Do upper or lower teeth erupt first
Lowers except 5’s
What distance is usually required between the distal of 2 and mesial of 6 to prevent crowding
22mm
Name 4 abnormalities in tooth formation
Crown root dilaceration
Supernumeraries
Peg shaped laterals
Hypodontia
What is crown root dilaceration
Trauma causes displacement of unerupted permanent crown and root formation continues in a different direction
What usually causes dilaceration
Trauma in deciduous dentition
What do peg laterals increase risk of
Ectopic canines
What teeth are most commonly missing in hypodontia
Upper 2s
Lower 5s
How does hypodontia present
Delayed exfoliation of deciduous teeth
Delayed eruption of permanent teeth
What can cause abnormalities in eruption and exfoliation
Eruption cyst
Impacted teeth
Infra-occluded deciduous teeth
retained deciduous
Cross bites in the mixed dentition
How do eruption cysts appear
Blue mucosa over unerupted teeth
What teeth are eruption cysts most common with
E’s and 6’s
name 4 causes of impacted teeth
obstruction (supernumerary)
primary failure of eruption
insufficient space
ectopic teeth
what causes infraoccluded deciduous teeth
ankylosis
adjacent teeth erupt and ankylosed teeth remain unchanged vertically - gives appearance of submerging
what can cause premature loss of deciduous teeth
caries
balancing and compensating extractions
trauma
what trauma can result in a centre line shift in incisors
avulsion
when would you use balancing extraction
if concerned will cause a centre line shift during eruption of the permanent incisors
what primary teeth extraction are more likely to cause a centreline shift
Cs and Ds
when are compensating extractions usually done
lower 6’s so compensate with upper 6
prevent overeruption
what can cross bites cause
displacement-tooth and jaw
tooth wear
easily corrected in mixed dentition
what is optimum age for 6 XLA
9-10
what does thumb sucking cause
proclined upper anteriors
retroclined lower incisors
buccal segment crossbites
reduced overbite or anterior open bite
what are some management techniques for digit sucking
deterrent devices/habit breakers
elastoplast on finger
encouragement
nail varnish
what % 6 year olds have midline diastema
98%
what size diastema doesnt require tx
<3mm
what would be tx of choice for large diastema
fixed appliances
