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BDS3 Orthodontics > Appliance design > Flashcards

Appliance design Flashcards

1
Q

10 uses of casts

A
  • Record treatment – mention outcome tx
  • 3D representation of pt not there
  • Design appliances
  • Medical legal reasons
  • Occlusions – assess for malocclusion
    • get diagnosis
    • treatment plan
  • motivator – wax
    • don’t want to good – want realistic expectations
  • emphasise problems – more informed pt decision
  • teaching
  • forensics
  • retrospective studies
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2
Q

aim of orthodontics

A

Functioning, aesthetics, stable occlusion

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3
Q

12 stainless steel properties

A
  • malleable
  • biocompatible
  • doesn’t corrode
  • non-toxic
  • strong
  • flexible
  • resistant to abrasion
  • high melting temperature
  • elastomeric response – spring back into shape
  • durable
  • ductile
  • cheap
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4
Q

5 components of stainless steel (and %)

A

72% Iron

18% Chromium

8% Nickel

  1. 7% Titanium
  2. 3% Carbon
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5
Q

URA

A

upper removable appliance

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6
Q

LRA

A

lower removable appliance

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7
Q

how do removable appliances working

A

move teeth

  • tipping
  • tilting

see saw effect

  • around fulcrum – midpoint

move crown and root – not bending

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8
Q

advantages of removable appliances (9)

A
  • tipping of teeth
  • excellent anchorage
  • generally cheaper than fixed – acrylic and SS – cheaper than fixed (bracket per tooth)
    • LRA less tolerated – impinging on tongue space
  • Shorter chairside time required
  • Oral hygiene is easier to maintain – removable and clean them
  • Non-destructive to tooth surface – no prep
    • Composite bonds wire to teeth – need etch (destructive)
  • Less specialised training needed to manage
  • Can be easily adapted for overbite reduction
    • How deep lowers coming up behind uppers
      • Can be traumatic
  • Can achieve block movements
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9
Q

disadvantages of removable appliances

A
  • Less precise control of tooth movement
    • only tipping/tilting, not lateral or intrusion/extrusion
  • Can be easily removed by the pt
  • Generally, only 1-2 teeth can be moved at a time (fixed can do multiple)
  • Specialist technical staff required to construct the appliances
    • check scope
  • Rotations very difficult to correct – only small degree able to change
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10
Q

potential result due to crowding

A

common

  • Rotated, overlapped, ectopic, PE anteriors due to lack of space
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11
Q

issues with overjet

A

horizontal

trauma, function, undesirable look, can get incompetent lips, lip trap (rest or infront of teeth)

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12
Q

how to create space in arch (2)

A

extract

widen arch - move teeth out

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13
Q

how to show extraction on design sheet

A

cross tooth out

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14
Q

common tooth to extract for ortho space creation

A

premolars

1st more – depends on angulation

  • Cross out on design
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15
Q

what would the aim on URA design sheet be for

  • anterior crowding + 6mm overjet
A

Aim - Please construct URA to retract 13 + 23

tell them what you want to achieve

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16
Q

retract

A

move distally

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17
Q

procline

A

push forward

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18
Q

retrocline

A

push back

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19
Q

notation used in appliance sheets

A

FDI in GDH

common to see palmer outwith

20
Q

ARAB

A
  • Active components
  • Retentive
  • Anchorage
  • Baseplate
21
Q

active component

A
  • Part of moving teeth through application of force
22
Q

active component for

  • anterior crowding + 6mm overjet
A

13 and 23, palatal finger spread + guards, 0.5mm HSSW (hard, can get soft not in ortho)

23
Q

why need to state gauge of wire on design sheet

A
  • Direct relation to amount of force
    • Thinner – lighter
    • Thicker – greater
24
Q

how to draw palatal finger spread (active component)

A

Round mesial aspect of tooth

Coil is where force exerted form

Retentive part

Guideplane

25
retentive
* Resistance to displacement forces
26
4 displacement forces URA subjected to everyday
* Tongue * Mastication * Speaking – vibrations in palate * Gravity * Active component – forces applied to teeth translate back onto the retentive component
27
posterior retentive element usually placed on
first permanent molars for posterior retnetion
28
common posterior retention design
16 + 26, **Adam’s clasp**, 0.7mm HSS
29
why thicker wire used for retentive component compared to active component?
Thicker as don’t want to be as flexible | (0.7mm HSSW compared to 0.5mm HSSW)
30
anterior retention example for ## Footnote anterior crowding + 6mm overjet
11 + 21, Southend Clasp, 0.7mm HSSW
31
why should you always write and draw designs
to minimise the chance of errors
32
anchorage
* Resistance to unwanted tooth movement
33
anchorage based around what law
Newtons 3rd law – every action there’s equal opposite reaction
34
base plate
use Self-cure PMMA
35
where to mark distal of baseplate is 7s fully erupted
half way across them
36
3 functions of baseplate
* Unite all the components * Retention – through adhesion, cohesion * Anchorage
37
3 types of PMMA
* Heat * Self * Light cure
38
what are the two optoins for URA PMMA
heat and self cure PMMA not light
39
why choose self cure PMMA over heat cure PMMA for URA
Heat cure – 15 hours process – wax, lost wax Self cure – less stages 15 mins - easier and quicker -satisfactory for disposable Heat cure Vs self cure * Need heat * Self – short working time * Heat – significant working time till exposed to heat * Heat cure stronger * Heat cure – less monomers (monomer liquid, poly powder) – little residual monomer * self cure more – allergic reactions and odour * Heat cure shrinks less than self cure Heat cure fundamentally better But most URA in self-cure
40
aim for tooth movement per month in URA
1mm
41
what distances to measure pre treatment
space tooth being moved (e.g. premolar width that was extracted) overjet
42
6mm gap distal to canine aim to be closed in
6 months so 6mm gap mesial 3/distal 2
43
what happens is the canine/tooth to be moved is unable to move e.g. fixated to bone
Gap distal shorter Whilst gap mesial increase * Increased overjet -\> 12mm * Every action has equal and opposite reaction* * *Forward movement for distal canine*
44
how does baseplate provide anchorage
covering entire palate so giving resistance to forward movement
45
what should you see on monthly measurements in ortho treatment of: ## Footnote anterior crowding + 6mm overjet
distal (decrease) and mesial (increase) overjet (remain)
46
balancing forces
only move 1-2 teeth at time * Too many – balance wrong – anchorage goes wrong * Snowball

BDS3 Orthodontics (13 decks)

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