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Ortho > 3rd year labs > Flashcards

3rd year labs Flashcards

1
Q

appliance design - URA to retract buccally placed 13 and 23 and reduce OB

A

A - 13 and 23 buccal canine retractors, 0.5mm HSSW and 0.5mm ID tubing
R - 16 and 26 Adams clasps 0.7mm HSSW, 11 and 21 Southend clasp 0.7mm HSSW
A
B - self-cure PMMA, FAB OJ plus 3mm

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2
Q

appliance design - URA to correct anterior CB 12

A

A - Z-spring 0.5mm HSSW
R - 16, 26, 14, 24 Adams clasps 0.7mm HSSW
A
B - self cure PMMA, PBP (needs to cover all posterior teeth)

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3
Q

appliance design - URA to retract 13 and 23

A

A - 13 and 23 palatal finger springs and guards 0.5mm HSSW
R - 11 and 21 Southend clasp 0.7mm HSSW, 16 and 26 Adams clasp 0.7mm HSSW
A
B - self-cure PMMA

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4
Q

appliance design - URA to retract 13 and 23 and reduce OB

A

A - palatal finger springs and guards 13 and 23 0.5mm HSSW
R - 16 and 26 Adams clasps 0.7mm HSSW, 11 and 21 Southend clasp 0.7mm HSSW
A
B - self-cure PMMA, FAB OJ plus 3mm

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5
Q

appliance design - URA to expand the U arch

A

A - midline palatal screw
R - 16, 26, 14, 24 Adams clasps 0.7mm HSSW
A - reciprocal anchorage
B - self-cure PMMA, FPBP

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6
Q

HSSW gauge for retentive components

A

0.7

adams clasp can use 0.6 for deciduous

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7
Q

HSSW gauge for stops

A

0.7/(flattened)

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8
Q

HSSW gauge for active components

A

0.5

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9
Q

HSSW gauge buccal canine retractor (supported)

A

0.5mm sheathed with 0.5mm ID tubing

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10
Q

HSSW gauge Roberts retractor

A

0.5mm sheathed with 0.5mm ID tubing

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11
Q

unsupported buccal canine retractor

A

0.7mm HSSW - but too much force so don’t work well - don’t really use

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12
Q

palatal finger spring - pressure exerted by spring depends on

A

size of coil (3-4mm diameter)
thickness of wire (0.5mm HSSW)
overall length of arm inc coil (approx 20mm)

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13
Q

structure of palatal finger spring in URA

A

active arm engages contact point, applies distal force
guard/guide wire
active arm on top of coil 2/3 into palate/20mm long
3-4mm coil facing mesially
mechanically retained tag embedded within acrylic
waxed out area allowing free movement of spring within acrylic

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14
Q

action of palatal finger spring

A

can be used to move any tooth M/D along the line of the arch

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15
Q

palatal finger springs to move molars

A

0.8 mm

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16
Q

palatal finger spring - importance of position of coil

A

most important as it influences how efficiently the spring moves the tooth
bisect start finish position for position of coil

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17
Q

advantages of palatal finger spring

A

provides a light pressure and is well tolerated

several springs can be added if required to retract teeth successively

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18
Q

disadvantages of palatal finger spring

A

cannot move teeth in a palatal direction so unsuitable for buccally placed teeth
if it was used it may move the tooth further buccally and tend to produce rotation

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19
Q

guard wires

A

incorporated to prevent displacement/distortion of the spring during wear

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20
Q

guard wires position

A

place away from coil and shouldn’t impede tooth movement

usually 0.5mm HSSW with slight curve so it follows the shape of the arch

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21
Q

open spring and guard wires

A

may have guard wire placed on tissue side or either side so in action it slides between the 2

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22
Q

boxed spring and guard wires

A

can have guard wire on tissue side to prevent the spring from becoming distorted

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23
Q

open palatal finger spring

A

tissues stay much healthier
baseplate of appliance can be much weaker if >1 spring used
easier adjusting as access with the pliers is easier
advisable to use twin guard wires, open springs more liable to distortion if no guard wires used

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24
Q

boxed/closed palatal finger spring

A

can lead to proliferation of the tissues into the boxed area - not serious problem as only for about 6m
- any temp modification to underlying mucosa quickly reverts to its normal condition after a short time
baseplate much stronger - greater acrylic coverage
acrylic can be used to guide tooth along line of arch
take care to ensure spring over freely within boxed area and has adequate range of movement

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25
Q

what are wire tags needed for in the baseplate?

A

mechanical retention

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26
Q

ID tubing function

A

adds strength and rigidity - prevents distortion in buccal sulcus

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27
Q

why does a z spring need a lot of retention?

A

produces a lot of displacement force

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28
Q

what are FABPs used for?

A

correction of an overbite

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29
Q

PBP

A

prop bite open to allow movement of anterior tooth
cover all posterior teeth or some will overerupt
will go back into position when remove
incisors will act as retainer

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30
Q

if 7s are PE where should baseplate finish?

A

behind 6s

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31
Q

which teeth will overerupt?

A

posteriors (incisors don’t)

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32
Q

Adams clasp - what should you check first?

A

flyover then arrowhead

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33
Q

Adams clasp - if flyover distorts and interferes with occlusion

A

may not engage into UC
if keep biting - metal fatigue - break - could inhale/swallow
arrowhead could dig into gingiva - ST trauma

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34
Q

midline palatal screw

A

expands the upper arch

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35
Q

midline palatal screw anchorage

A

reciprocal anchorage

36
Q

what should be used with midline palatal screw?

A

PBP - if deep occlusal digitation could also pull lower teeth out accidentally too

37
Q

midline palatal screw retention

A

Adams clasps 4 and 6s - can’t use Southend as would split

38
Q

midline palatal screw - if just want to expand posteriors

A

stop acrylic appropriately

39
Q

midline palatal screw - expand one side more

A

move division line - larger force on smaller area - will move more

40
Q

midline palatal screw movment

A

0.2-0.25mm per week
turn screw 1-2 per week

= 1mm movement per month

41
Q

SS work hardening

A

hard wire - draw cold metal through a series of dies of successively smaller diameter
- causes work hardening - gives wire spring properties
further work hardening during bending process of constructing components - utilise to increase spring properties

42
Q

SS wire fractures causes

A

overworking
mechanical abrasion
fatigue
weld decay

43
Q

overworking

A

bending then straightening the wire at the same point

creates extreme stresses within the immediate area

44
Q

mechanical abrasion

A

damaged by burs/stones/crushed

45
Q

fatigue

A

repeated straining action e.g. continually strained to engage a deep undercut with an Adams clasp

46
Q

weld decay

A

intergranular corrosion created by overheating alloy
causes chromium carbides to ppt at grain boundaries
oral fluids can now access the surface of other metals

= galvanic action - weakens - fracture

47
Q

18-8 SS composition

A 
72% Fe
18% Cr
8% Ni
1.7% Ti
0.3% C
48
Q

Cr in SS

A

corrosion resistant - forms passive oxide film over surface

lowers temp at which martensite forms

49
Q

Ni in SS

A

corrosion resistance and strength

50
Q

Ti in SS

A

prevents ppt of Cr carbides at grain boundaries when alloy heated during welding or soldering

51
Q

18-8 alloy form

A

austenitic
can’t be heat hardened and remains soft unless cold worked
corrosion resistant when cold worked

52
Q

martensite

A

principal component of hard steel

formed by quenching from high temps

53
Q

explain why martensite is harder

A

cube distorted by interstitial carbon atoms that do not have time to diffuse out during quenching

  • creates crystal defects within the material similar to work hardening
  • prevent atoms from sliding past one another in an organised fashion - material harder
54
Q

writing a lab prescription

A 
cross out missing teeth
aim
active components
retention
anchorage
baseplate
55
Q

active component

A

whatever applies force to teeth

56
Q

retention

A

resistance to displacement forces

57
Q

anchorage

A

resistance to unwanted tooth movement - newtons 3rd law

so only tend to move 1-2 teeth at a time in a URA

58
Q

functions of baseplate

A

connector
retention (cohesion adhesion)
anchorage

59
Q

where should the baseplate extend?

A

halfway to 7s otherwise gag reflex

60
Q

baseplate material

A

self-cure PMMA

  • quicker
  • more residual monomer (allergy)
  • disposable appliances - properties adequate
61
Q

when should you make the baseplate in heat cure?

A

if the pt has a known monomer allergy

62
Q

PMMA liquid

A

monomer

63
Q

PMMA powder

A

polymer

64
Q

heat cure PMMA advantages

A

better mechanical properties
can control curing
- easier to work with
more dimensionally stable

65
Q

IO displacement forces

A 
gravity
mastication
tongue
talking
active component
66
Q

tooth movement aim

A

1mm per month

67
Q

reasons for slow tooth movement

A

relying on bone resorption and remodelling
can cause root resorption/rip PDL
can rip/cut off blood supply - necrosis
more force = more displacement force

68
Q

increased OJ consequences

A

trauma risk
aesthetics
functional - biting

69
Q

avoiding increasing OJ with URA

A

measure OJ each month - should remain same

baseplate helps to prevent

70
Q

reasons for tx

A

oral function
dental health
aesthetics

71
Q

aims of tx

A

stability
function
aesthetics

72
Q

what movement do URAs achieve?

A

tipping

73
Q

advantages of fixed

A

precise control - rotation and controlled root movement possible
multiple tooth movement simultaneously
reduced impingement on tongue space
can’t easily be removed by pt

74
Q

disadvantages of fixed

A

OH more difficult

components can be ££

75
Q

advantages of removable

A

no OH problems
cheap
simple to adjust if correctly manufactured - less clinical time
palatal coverage increases anchorage
can be adapted to transmit force to blocks of teeth

76
Q

disadvantages of removable

A

removable
only tilting
bulky - speech can be initially impaired and can produce increased salivation
need careful removal and insertion to avoid fractures or the appliance becoming deformed

77
Q

functional

A

source of force is not contained in the appliance - most passive
constructed so mandible is maintained in a postured position - influences orofacial musculature and dentoalveolar development
growing pts

78
Q

advantages of Adams clasp

A

small, neat, unobtrusive
can use on almost any tooth
can clasp PE tooth
highly versatile - can modify
highly retentive
provides a site (bridge) where pt can apply pressure with fingertips during removal
auxiliary springs can be soldered to bridge
can solder hooks or bent in during construction to accept inter-maxillary traction
can solder tubes to bridge of clasp to accommodate facebow for EO traction

79
Q

how do teeth move?

A

prolonged force
bone remodelling
controlled by PDL - OC and OB around tooth
compression and tension areas
- causes extra blood flow in both areas increasing cellular activity

80
Q

desirable pressure

A

25g/sq cm = 1mm per month

81
Q

FABP

A

OJ+3mm - prevents retroclining L incisors

build up of platform of acrylic behind U incisor

reduces OB

get posterior open bite - will sort as lowers tend to continue erupting

remove bite platform then correct OJ

82
Q

stages in appliance delivery

A

1 - check right appliance and right pt
2 - make sure appliance is the right design
3 - run finger over to ensure no sharp areas
4 - look for potential signs of damage
5 - try in mouth - look for blanching
6 - check posterior retention
7 - check anterior retention
8 - check and activate active components
9 - show pt correct way to insert and remove, get them to demonstrate it back to you
10 - book review 4-6wks

83
Q

advice to give pt

A

will feel big and bulky, but normal, will get used to it
affects speech - lisp - practice reading out loud at home - tongue will adapt
lots of saliva - will pass quickly
will feel tender/pressure/mild discomfort on that tooth - shows appliance is working
wear 24/7 inc mealtimes
take it out to clean with soft brush after every meal
can take off for contact/active sports = protective container
avoid custom gumshields - move teeth back
avoid hard and sticky foods - will damage appliance
be careful with hot food and drink - baseplate can act as insulator
non-compliance will significantly lengthen tx
emergency contact details

84
Q

z-spring which coils should be activated?

A

both coils = for straight movement

85
Q

wire thickness and force

A

thinner wires - less force

Ortho (21 decks)

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