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BDS4 Orthodontics > Fixed Appliance > Flashcards

Fixed Appliance Flashcards

1
Q

What is a fixed appliance

A

An appliance which is fixed to the teeth and cannot be removed by the patient

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2
Q

What does a fixed appliance consist of

A

brackets, bands, archwires and auxillaries

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3
Q

What are the features of fixed appliances

A

o 3D control
o Complex tooth movements
o Control of root
o Less dependant on compliance
o Requires excellent oral hygiene
o Risk of iatrogenic damage
o Poor intrinsic anchorage

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4
Q

What are the features of removable appliance

A

o Simple tooth movements (tipping/tilting)
o No control over root movement
o Greater compliance required
o Less risk of iatrogenic damage
o Good instrinic anchorage - due to baseplate covering palate

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5
Q

When do we use fixed

A
  • Correction of mild to moderate skeletal discrepancies (camouflage)
  • Alignment of teeth
  • Correction of rotations
  • Centreline correction
  • Overbite and overjet reduction
  • Closure of spaces/creating spaces
  • Vertical movements of the teeth (extrusion/intrusion)
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6
Q

What are andrew’s 6 keys

A
  • Tight approximal contacts with no rotation
  • Class 1 incisors
  • Class 1 molars
  • Flat occlusal plane or slight curve of spee
  • Long axis of the teeth have slight mesial inclination except the lower incisors
  • The crowns of the canines back to the molars have a lingual inclination
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7
Q

What are andrew’s 6 keys

A
  • Tight approximal contacts with no rotation
  • Class 1 incisors
  • Class 1 molars
  • Flat occlusal plane or slight curve of spee
  • Long axis of the teeth have slight mesial inclination except the lower incisors
  • The crowns of the canines back to the molars have a lingual inclination
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8
Q

What is the 7th key of occlusion

A

Bolton’s ratio
relates to tooth proportions, sizes and formation so everything fits together

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9
Q

What are the components of a fixed appliance

A

bracket/tube
band
archwire
modules
auxillaries
anchorage components
force generating components

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10
Q

What are the components of the bracket

A

bracket slot
tie wing
bracket base

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11
Q

What are the different bracket materials

A

stainless steel, CoCr, Ti, Au

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12
Q

What does the bracket prescription determine

A

o Bracket prescription determines the tip, torque and in/out control
o MBT prescription used

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13
Q

How are brackets bonded on

A

o Acid etch technique
o Used for brackets and tubes but not bands
o Photoinitiation reaction using light cure 440-480nm wavelength of light
o Utilises micromechanical retention
o The brackets come in sealed pods and they have a dot marker which is a clinical indicator to help with orientation, they go towards the gingiva distally
o Don’t want much flash  caries risk

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14
Q

What are bands

A
  • Made of stainless steel with prewelded attachments: cleats or tubes
  • Requires space prior to placement so requires a separator visit
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15
Q

Where are orthodontic bands placed

A
  • Tend to be placed only on posterior teeth due to aesthetics
  • Also consider use if needing to involve heavily restored teeth with not enough enamel to bond to
  • Orthognathic patients will often have terminal molars banded as they are more robust and harder to dislodge
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16
Q

How are bands bonded

A

GI cement

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17
Q

What are the various arch wire materials

A

stainless steel
niti
cocr
beta titianium
composite/glass

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18
Q

What are the features of stainless steel wire

A

o Working archwires to slide teeth
o Used for moving teeth
o Low friction
o Formable so can put archwire bends and loops

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19
Q

What are the features of nickel titanium wire

A

o Flexible
o Light continuous force - wire tries to return to original shape
o Shape memory - wants to return to original shape and cannot bend
o Higher friction than stainless steel- undesirable, slower tooth movement
o Start with round NiTi then onto rectangular Niti then stainless steel

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20
Q

How do force generating components work

A

Teeth move by utilising the energy stored in the elastic or spring
sliding mechanism utilised

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21
Q

What are the different force generating components

A

elastic power chain
niti coils
intra-oral elastics
active ligature

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22
Q

What are elastic power chains

A

 Elastic chain running from hook to appliance on anterior tooth to posterior tooth and it helps pull the buccal segment together
 Elastic loses its properties so the elastic chain will only be 50% as active weeks later so by the time they come back, the elastic needs to be replaced

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23
Q

What are ni-ti coils

A

Still have elastic memory but in coil form so when we stretch the coil and works continuously to close the space
Better than elastic as elastic properties degrade

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24
Q

What are intra-oral elastics

A

 Can be used for class 3 or class 2 malocclusions
 The patient changes them at home
 Provides specific direction of force and helps guide teeth into ideal position

25
Q

Where are intra oral elastics placed for class 3

A

anterior tooth on lower jaw (usually canine) attached to posterior tooth on upper jaw (usually a 6)

26
Q

Where are intra oral elastics placed for class 2

A

anterior tooth on upper jaw (usually a canine) attached to a posterior tooth on lower jaw (usually a 6)
Useful for reducing OJ and OB at the same time

27
Q

What is anchorage

A

resistance to unwanted tooth movement

28
Q

What theory is anchorage based on

A

newton’s third law which is every force has an equal but opposite reactionary force

29
Q

What is simple anchorage

A

o This is one tooth against the other
o E.g trying to move back a canine against a molar
o The molar has a bigger root surface therefore the canine will move more than the molar and so the molar is the anchor

30
Q

What is compound anchorage

A

More than one tooth used as the anchor
Trying to increase the size and surface area against the tooth we are trying to move

31
Q

What is reciprocal anchorage

A

Equal forces in both directions
E.g diastema closure, two central incisors are of equal weighting and so will move the same way

32
Q

What are the types of anchorage

A

absolute anchorage
cortical anchorage
intermaxillary anchorage
headgear

33
Q

What is absolute anchorage

A

This is defined as no movement of the anchorage unit (hence zero anchorage loss) as a consequence of the reaction forces applied to move teeth

33
Q

What is absolute anchorage

A

This is defined as no movement of the anchorage unit (hence zero anchorage loss) as a consequence of the reaction forces applied to move teeth

34
Q

How can absolute anchorage be obtained

A

use of ankylosed teeth or implants

35
Q

What are temporary anchorage devices

A

non-osseointigrating mini screw

36
Q

Why are TADs useful

A

Revolutionised notoriously difficult cases e.g hypodontia cases
Can be placed into interradicular bone and placed in the palate
Can be used in the palate when there is a moderate anterior open bite and you are trying to prevent a surgical treatment pathway

37
Q

What is cortical anchorage

A

Cortical plates provide increased resistance to tooth movement

38
Q

What is an example of cortical anchorage

A

transpalatal arch

39
Q

How does cortical anchorage work

A

It moves the roots torwards the cortical plate to dercease the tendency of the molars to move mesially in response to orthodontic force
Nance button uses palatal vault for more anchorage reinforcement

40
Q

What is intermaxillary anchorage

A

Defined as anchorage in which the resistance units situated in one jaw are used to effect tooth movement in the opening jaw
Uses intra-oral elastics

41
Q

What is headgear

A

Can be used for anchorage reinforcement
Not used much anymore
Comes with risk of ocular injuries hence safety mechanisms must be ensured

42
Q

What is retention

A

maintaining the final tooth position with a passive orthodontic appliance

43
Q

What are features with high relapse potential

A

o Diastema/space closure
o Rotations
o Palatally ectopic canines
o Proclination of lower incisors
o Anterior open bite
o Instanding upper lateral incisors

44
Q

What are the 2 types of removable retainers

A

PFR
hawley

45
Q

What are the features of PFR

A

Variety of materials and thicknesses
Can include prosthetic tooth for aesthetics
Well tolerated
Usually 2 wks full time wear and then night only there after

46
Q

How does hawley retainer work

A

Labial bow to control incisors and canines
Not well tolerated in the lower arch

47
Q

What are the indications of fixed retainers

A
  • Spaced closure
  • Diastema
  • Proclination of lower labial segment
  • Periodontal cases
  • Ectopic canines
  • Isntanding upper 2s
48
Q

What are the features of bonded wire retainer

A
  • Requires careful monitoring and interdental cleaning
  • Ensure composite attachments intact and sound
  • Refer back to the orthodontist if any problems
49
Q

What are the main risks of fixed appliance

A

Decalcification
Root resorption
Relapse
Enamel Wear

50
Q

What is the average root resorption

A

on average 1mm of root length per teeth, importance of pre-op radiograph to ensure adequate root length prior

51
Q

What increases risk of root resorption

A

 Higher risk roots are narrow/tapered roots
 Spindly roots
 Shorter roots

52
Q

Describe the patient journey

A

assessment/diagnosis
tx plan
commence tx
routine adjustments

53
Q

How long does the average ortho case take

A

18-24 months

54
Q

How long does a hypodontia & orthognathic case take

A

24-30 months

55
Q

How long does a hypodontia & orthognathic case take

A

24-30 months

56
Q

How often are routine adjustments made

A

4-8 wks

57
Q

What are the initial problems encountered

A

o Pain
o Mucosal irritation
o Ulceration
o Appliance breakage

BDS4 Orthodontics (10 decks)

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