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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
Q

retentive

A
  • Resistance to displacement forces
26
Q

4 displacement forces URA subjected to everyday

A
  • Tongue
  • Mastication
  • Speaking – vibrations in palate
  • Gravity
  • Active component – forces applied to teeth translate back onto the retentive component
27
Q

posterior retentive element usually placed on

A

first permanent molars for posterior retnetion

28
Q

common posterior retention design

A

16 + 26, Adam’s clasp, 0.7mm HSS

29
Q

why thicker wire used for retentive component compared to active component?

A

Thicker as don’t want to be as flexible

(0.7mm HSSW compared to 0.5mm HSSW)

30
Q

anterior retention example for

anterior crowding + 6mm overjet

A

11 + 21, Southend Clasp, 0.7mm HSSW

31
Q

why should you always write and draw designs

A

to minimise the chance of errors

32
Q

anchorage

A
  • Resistance to unwanted tooth movement
33
Q

anchorage based around what law

A

Newtons 3rd law – every action there’s equal opposite reaction

34
Q

base plate

A

use Self-cure PMMA

35
Q

where to mark distal of baseplate is 7s fully erupted

A

half way across them

36
Q

3 functions of baseplate

A
  • Unite all the components
  • Retention – through adhesion, cohesion
  • Anchorage
37
Q

3 types of PMMA

A
  • Heat
  • Self
  • Light

cure

38
Q

what are the two optoins for URA PMMA

A

heat and self cure PMMA

not light

39
Q

why choose self cure PMMA over heat cure PMMA for URA

A

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
Q

aim for tooth movement per month in URA

A

1mm

41
Q

what distances to measure pre treatment

A

space tooth being moved (e.g. premolar width that was extracted)

overjet

42
Q

6mm gap distal to canine aim to be closed in

A

6 months

so 6mm gap mesial 3/distal 2

43
Q

what happens is the canine/tooth to be moved is unable to move e.g. fixated to bone

A

Gap distal shorter

Whilst gap mesial increase

  • Increased overjet -> 12mm
  • Every action has equal and opposite reaction*
  • Forward movement for distal canine
44
Q

how does baseplate provide anchorage

A

covering entire palate so giving resistance to forward movement

45
Q

what should you see on monthly measurements in ortho treatment of:

anterior crowding + 6mm overjet

A

distal (decrease) and mesial (increase)

overjet (remain)

46
Q

balancing forces

A

only move 1-2 teeth at time

  • Too many – balance wrong – anchorage goes wrong
    • Snowball

BDS3 Orthodontics (13 decks)

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