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removable appliances Flashcards

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1
Q

How do RA work?

A

Tip teeth
Move blocks of teeth
influence eruption of opposing teeth

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2
Q

Why do RA only tip teeth?

A

Because they have only a single point of contact and applies a force which tilits a tooth about its fulcrum

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3
Q

Why can removable appliances move blocks of teeth?

A

because they are connected via a baseplate so more efficient than fixed appliances

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4
Q

How can RA affect the eruption of opposing teeth?

A

Flat anterior guide plane

Buccal capping

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5
Q

When is a flat anterior guide plane useful?

A

overbite reduction

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6
Q

When is buccal capping useful?

A

intruding posterior teeth

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7
Q

What are the problems arising from just tipping teeth?

A

aesthetics

occlusal fit

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8
Q

What are the advantages of removable appliances?

A 
removed for tooth brushing
palatal coverage increases area for anchorage
less risk of iatrogenic damage
used as a passive retainer
transmits forces to blocks ofteeth
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9
Q

What are the disadvantages of removable appliances?

A 
appliance can be left out
only tiliting movements possible
affects speech
intermaxiliiary traction not possible
lower appliances less tolerable
inefficient for mutliple tooth movements
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10
Q

Why are RA less succesful in the lower arch?

A

less tolerated as appliance encroaches on the tongue space
Less space
Less retention due to less undercut
Less sulcus depth for buccal springs

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11
Q

T/F RA can perform vertical movements?

A

F

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12
Q

T/F the movements of teeth in RA are less precise?

A

T

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13
Q

T/F RA cannot derotate a tooth?

A

T

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14
Q

When are RA most commonly used now?

A 
Space maintainence
retainer
tooth over the bite
bite opening
arch expansion
functional appliances
simple tooth movements
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15
Q

What are the advantages of an acrylic baseplate?

A

Can provide an anterior and posterior bite plane
accomadate a screw
gives anchorage from palatal vault

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16
Q

How can you be sure the patient is wearing the removable appliance?

A 
speech has improved
confident in removing and replacing
wear facets
has become loose/passive
gingivitis on palate
teeth have moved
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17
Q

What are the components of RA?

A

Active components
retentive components
base plate
anchorage

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18
Q

Which component should be designed first?

A

Active

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19
Q

When should extraction be done, before or after the RA is fitted? and why?

A

after (as a general rule)
because patient may decide once RA fitted that they do not want to continue with the treatment
AND
if there is a delay in time between extracting the tooth and fitting the RA the the space will close

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20
Q

What is the most commonly used active component?

A

spring

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21
Q

What is the relationship between F and othodontic springs?

A 
F proportional to dr^4/l^3
and elastic modulus 
d is deflection
r is radius
l is length
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22
Q

What are example of active components on removable appliances?

A

springs
bows
screws

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23
Q

WHat are the three types of springs used as buccally?

A

self supporting
sleeved
reversed loop

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24
Q

What is the type of spring used as a palatal springs?

A

palatal spring

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25
What is the diameter of the wire used in the self supporting retractor and how mich do dou you activate it by?
0.7mm activate 1mm
26
What are the advantages of the self supporting retractor?
still | good control of spring positions
27
What are the disadvantages of the self supporting retractor?
stiff so provides a high force | high in sulcus so damages mucosa
28
WHat are the advanatges of the sleeved buccal retractor?
flexible and good control
29
What are the disadvanatages of the sleeved buccal retractor?
high in sulcus so can traumatise mucosa
30
How thick is the sleved buccal retractor and by how much do you activate it?
0.5mm ss wire | 2mm activation
31
What are the advanatges of the reverse loop buccal retractor?
it is short vertically so less traumatic | good lateral control of spring position
32
What are the disadvanatges of the reverse loop buccal retractor?
it is stiff | short range of action
33
How thick is the wire in the reverse loop buccal retractor and how much do you activate it by?
0.7mm | activated by 1mm
34
Which springs push teeth labially?
z springs
35
Which springs push teeth buccally?
t springs
36
How thick is the wire on the z springs?
0. 5/0.6/0.7 | 0. 5mm used for single tooth
37
How much do you activate z springs by?
single tooth: 1-2mm | double tooth: 3-4mm
38
WHat are the disadvanatges to Z springs?
displaces the appliance so need good retention
39
WHat are the advanatges of z springs?
easy to adjust | vary degree of activation depending upon the amount of teeth needing to move
40
How do you activate z springs?
activate by turning 45 degrees in direction of movement
41
When are T srprings needed?
buccal segment teth
42
What are the advanatges of T springs?
easy to adjust
43
What are the disadvanatges of T springs?
displaces the appliance so need good retention | Limited range of action
44
What is so special about screws?
only means in a RA that can the tooth being retained can also be moved
45
WHen are screws used?
mesio-distal movement expansion correcting x bite
46
How do you activate T springs?
by pulling away from he acylic
47
How do you activate a screw?
turn 0.25mm/week
48
Why can you only activate a screw by 0.25mm?
this is dependant upon the space of the pdl | if you were to exceeed this, you would crush the pdl and this would cause cessation of movement
49
What feature is designed after active components?
retention
50
WHat is retention?
the resistance to movement away from tissues
51
How do we retain on posterior teeth?
adams clasp
52
How do we retain on anterior teeth?
Southend clasp (BEST RETENTION) Labial bow Adams clasp
53
WHat is the size of the wire used on adams clasps?
0. 7mm ss wire | 0. 6mm ss wrire can be used on premolars too
54
What is the size of wire used on southend clasp?
0.7mm ss wire
55
What is the size of wire used on a labial bow?
0.8mm ss wire
56
What are the components of an adams clasp?
a bridge two arrowheads two flyovers two tags
57
How do adams clasps gain retention?
by engaging into the undercut beneath the maximum bulbosity of the tooth
58
What are the advantages of using adams cribs?
E/O traction tubes can be soldered onto them | Double cribs can be used to straddle two teeth
59
WHat is the purpose of a labial bow?
retention guidance (canines during retraction) Active (retract incisors) retention
60
where should the labial bow be placed on the crown?
near the gingival sulcus to engage in some undercut
61
How can labial bows be used for incisor retraction?
split the labial bow | and then re solder once teeth moved
62
By which direction do teeth move relative to point of contact of spring?
90 degrees to point of contact
63
Where must the line of force pass through to avoid rotation of the tooth?
must pass through the centre of resistance
64
When using labial bows as active components, do we need a thin or thick wire?
thin | so it is more flexible
65
When is buccal capping used in remoable appliances?
occlusal interferences need to be removed to allow tooth movement and where a reduction in the overbite is undesirable
66
WHat is the name of the appliance used in conjusvtion with head gear?
Nudger appliance
67
When would you use a nudger appliance?
when you want distal movement of posteror teeth and then move on to fixed appliances
68
What are the ideal requirements of a spring?
``` apply the correct force over a good range move the tooth in the right direction difficult to position incorrectly recistant to accidental damage atraumatic hygeinic ```
69
what is the stress of wire?
F/unit area
70
What is the strain of the wire?
deflection/unit length
71
What is the modulus?
stress/strain
72
if you double the length of the wire what happens to the stiffness?
it decreases by a factor of 8
73
What happens if you double the radius of the wire?
the stiffness increases by a factor of 16
74
What happens to the force upon activation of the wire?
double the activation doubles the force
75
What is the size wire used for the palatal retractor?
0.5mm | ss
76
How much force is created with a 3mm activation on the palatal spring?
20-40g
77
what happens if you activate the palatal spring more then 3mm what happes?
it may self insert on the wrong side | applies too much force
78
When can you use palatal springs?
for mesiodstal movement of canines premolars and moalrs
79
What are the forces used to tip teeth?
25-50gms

Orthodontics (28 decks)

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