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BDS4 Orthodontics > Fixed Appliances > Flashcards

Fixed Appliances Flashcards

1
Q

What is a fixed appliance?

A

An appliance which is fixed to the teeth and cannot be removed by the patient
-> Consists of brackets, bands, archwires and auxillaries
-> Precision tooth movers

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2
Q

What are some of the ADV of fixed appliances?

A

 3D control
 Complex tooth movements
 Control of root
 Less dependant on compliance- not removable

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3
Q

What are some of the DIS of fixed appliances?

A

 Requires excellent oral hygiene
 Risk of iatrogenic damage- relapse, decal, root resorption
 Poor intrinsic anchorage- lack of baseplate
 Longer treatment time- 2-2.5 years

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4
Q

What are some of the ADV of removable appliances?

A

Used for tipping

Intrinsic anchorage

Easier cleaning

Less risk of iatrogenic damage

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5
Q

What are some of the DIS of removable appliances?

A

Simple tooth movements only

No control of root movement

Can be lost

Better compliance required

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6
Q

What are the uses of fixed appliances?

A

 Correction of mild to moderate skeletal discrepancies -Camouflage

 Alignment of teeth- straightening

 Correction of rotations

 Centreline correction- align with mid facial-axis

 Overbite and overjet reduction

 Closure of spaces/creating spaces

 Vertical movements of teeth- extrusion/intrusion

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7
Q

What is orthodontic camouflage?

A

Accepting underlying skeletal base relationship and treat malocclusion to class 1 incisor relationship

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8
Q

When do be people tend to notice a centre line deviation?

A

If it is greater than 4mm

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9
Q

What are Andrews Six Keys? (treatment aim)

A
  1. Tight approximal contacts with no rotations
  2. Class I incisors
  3. Class I molars
  4. Flat occlusal plane or slight curve of Speed
  5. Long axis of the teeth have a slight mesial inclination except the lower incisors
  6. The crowns of the canines back to the molars have a lingual inclination
  • Tooth proportion and size must fit within anatomical average to achieve this- very difficult clinically due to subtle differences in individuals
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10
Q

What are the different components that can be used on fixed appliances?

A

 Brackets- precision milled (different sizes for different teeth usually, although some universal brackets exist)
 Band- only done on posteriors due to aesthetics (used in heavily restored teeth without sufficient enamel structure to bond to- MIH)
 Arch wire- goes through bracket (communicates bracket to tooth to allow force to be exerted allowing tooth movement as per prescription)
 Modules-elastic donuts, hold wire to bracket (changed every visit)
 Auxiliaries- spring, plastic tubing to protect sites, elastomeric chain to close spaces
 Anchorage components- what is the demand?
 Force generating components- coils and springs

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11
Q

Why do patients who receive combined orthognathic and orthodontic surgery have their terminal molars banded?

A

Gives robust end point of appliance- keeps things secure during osteotomy in case of iatrogenic damage

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12
Q

What is straight wire?

A

Doesn’t require bending (prescription is included)

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13
Q

Why are molar tubes used instead of bands?

A

More discrete

Less irritating to soft tissue

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14
Q

What are the components of brackets and their function?

A

 Bracket slot (horizontal)- allows arch-wire to run through

 Tie wings- 4 on each bracket, modules attach here

 Bracket base- part that bonds to tooth
-> angulation is based on prescription (inclination and torque also pre-prescribed)

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15
Q

Why may canine brackets have hooks on them?

A

Can be used to attach elastics or springs

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16
Q

What materials can brackets be made from?

A

 Metal
-> SS, CoCr, Ti, Au

 Polymers

 Ceramics

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17
Q

What are the features of bands?

A

 Stock, so size must be estimated

 Have pre-welded attachments- tubes and cleats (can be traumatic- press these in to make them flush)

 Space prep visit required- as contacts are often very tight

 Cemented with GIC (removed with slow speed tungsten carbide bur)

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18
Q

What bracket prescription is used in GDH?

A

MBT prescription
 Helps us get nice occlusal finish
 Each tooth has different degree of tip, in/out and torque

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19
Q

How are brackets bonded to teeth?

A

Using acid etch technique with self etch primers (prevents excess rinsing and drying)
-> failure rate is low

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20
Q

What is the issue with using self etch primers to bond brackets?

A

Must be well mixed and agitated on tooth

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21
Q

What are the steps in bonding brackets?

A

Brackets are usually pre-coated in composite and sealed in a pod (individual for each tooth)
 Pop pod just after etching
 There are orientation marks to help clinician- goes distally gingivally
-> more expensive

If bracket was not pre-coated we would add composite before placing
-> less efficient, slower, more flash to trim away

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22
Q

What are the issues with excess flash when bonding orthodontic brackets?

A

Staining

Caries risk

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23
Q

Which materials can be used to make archwires?

A

 Stainless Steel (SS)
 Nickel Titanium (NiTi)
 Cobalt Chromium (CoCr)
 Beta-Titanium (TMA)
 Composite/glass

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24
Q

What are the ADV/DIS of NiTi Ortho wires?

A

ADV:
Flexible
Shape memory- produces light force as it tries to rebound to original shape and form from deflections (this is why the wires are not pre-bent)

DIS:
Higher friction- can prevent efficient sliding and tooth movement

25
Q

What are the advantageous properties of SS wire?

A

Low friction- good for sliding teeth along wire

Formable- can be bent
-> loops can be created for elastics

26
Q

What is the normal wire protocol in Fixed appliance treatment?

A

NiTi- early aligning wire
-> Start of with round light then work up to larger/rectangular

SS- Working wire for moving teeth after initial alignment

27
Q

What are the function of modules?

A

Elastomeric bands (typically) that go over tie wings to allow communication of wire and bracket

28
Q

What are self-ligating appliances?

A

Appliances with brackets that have gates (that are opened/closed using an instrument) which keep archwire in place

29
Q

What are the ADV and DIS of self ligating appliances?

A

ADV:
 More efficient movement as no degradation of modules
-> can be combined with elastomeric if required
 Lower friction- better sliding

DIS:
 Can get fused with plaque and calculus which can block gate closed (bracket need replaced)

30
Q

What is the function of a nance button?

A

Prevents mesial migration of posterior movements using palatal vault for anchorage reinforcement

31
Q

What are examples of force generating components?

A

Elastic power chain

NiTi coil springs

IO elastics

Active ligatures

32
Q

What is the function of a spring?

A

Can be used to push crowded teeth apart or open up space if teeth congenitally missing

33
Q

What is plastic sheathing used for?

A

Helps protect spans where extraction has been carried out, preventing deflection of wire due to occlusal forces (trauma to ST)

34
Q

What is the issue with elastic power chain?

A

Power chain only works short term until elastic properties degrade (50% as active after 2 weeks- needs replaced every 6 weeks)
-> good for space closing or pulling teeth into arch

35
Q

What is the function of NiTi coil springs?

A

 Placed between two brackets (cut more than you need to press into space)
 This will want to push back to initial length and can be used to distalise teeth creating space

36
Q

How do intra-oral elastics work? How are they altered for class II/III

A

Attach from canine to FPM

Class 3- brings lowers back and uppers forward
-> Lower canine to upper FPM

Class II- opposite

37
Q

What is anchorage?

A

Resistance to unwanted tooth movement
-> Every force applied has equal but opposite reactionary force
-> First aspect of planning- can be difficult to recover if incorrectly set up

38
Q

What is simple anchorage?

A

Smaller tooth vs bigger tooth
 Bigger tooth has more root surface area so acts as anchor and when force is applied smaller tooth is likely to be pulled back more

39
Q

What is compound anchorage?

A

2 teeth put together to increase size of root area, giving less unwanted and more favourable tooth movement

40
Q

What is reciprocal anchorage?

A

Reciprocal = equal (run elastics between to create equal force and equal rate of movement)

-> can be used to fix diastemas

41
Q

When is absolute anchorage used?

A

High anchorage demand case (and cant afford any unwanted movement)

42
Q

How is absolute anchorage achieved?

A

Using TADs (non-osteointegrating bone screw)- placed in buccal cortex under LA (interradicular)
-> requires careful planning so not to damage roots

43
Q

What cases are TADs useful for?

A

Hypodontia

Moderate AOB- placed in palate

44
Q

How is cortical anchorage achieved?

A

Using a transpalatal or lingual arch
-> Vertical anchorage when pulling canines from palate

45
Q

How is inter maxillary anchorage achieved?

A

Elastics

46
Q

Why has headgear been replaced by TADs?

A

Less risk of trauma/occular injury

No compliance issue- patients found it difficult to wear headgear for required 12-14 hours

47
Q

Why is lifelong retention required following fixed appliance treatment?

A

Teeth are not stable- relapse will occur as PDL fibres have elastic memory and want to recoil into original position

48
Q

Which features have highest relapse potential?

A

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

49
Q

What is the retainer wear protocol for pressure formed?

A

2 weeks full time (apart from eating and drinking)
-> then night time only

If perforated or worn- can be replaced by GDP

50
Q

What can be done with pressure formed retainers if patient has hypodontia?

A

Can add false teeth if hypodontia in aesthetic zone and not had prosthetic treatment yet

51
Q

What are the features of a Hawley Retainer?

A

 Acrylic baseplate with adam’s clasp on 6s
 Labial bow- can help against relapse of proclined upper anteriors (poor aesthetics)
 Can add teeth (backed up with metal) into acrylic for hypodontia patients (before prosthetic treatment)

52
Q

Which cases commonly require fixed retention?

A

 Spaced closure
 Diastema
 Proclination of lower
labial segment
 Periodontal cases
 Ectopic canines
 Instanding upper 2’s
-> sometimes any case

53
Q

What are the issues with fixed retainers?

A

Requires careful monitoring- check looseness

Orthodontist required to fixed breakages

Difficult OH

54
Q

How does decalcification appear?

A

Chalky white

Brown mottled

55
Q

What is the average amount of root resorption during orthodontic treatment?

A

1mm- can be more if naturally short or spindle shaped roots

-> monitor frequently with radiographs

56
Q

How long does fix appliance treatment last?

A

Average case- 18-24 months

Hypodontia case- 24-30 months

Orthognathic case- 24-30 months

57
Q

How often does a patient need to attend for adjustment of fixed appliance?

A

Every 4-8 weeks

58
Q

Which issues may a patient encounter at the start of fixed orthodontic treatment?

A

Pain

Mucosal irritation

Ulceration

Appliance breakages

BDS4 Orthodontics (14 decks)

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