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Module 8 > Orthodontics > Flashcards

Orthodontics Flashcards

Topics covered: Orthognathic surgery, Removable appliances - design and use,

1
Q

What does the term Orthognathic mean?

A

Straight jaws

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2
Q

What is Orthognathic surgery and what does it involve?

A

Surgical manipulation to produce optimal dentofacial function and aesthetics.

This involves changing the skeletal relationships to correct facial deformity.

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3
Q

What is a dental deformity?

A

A dental deformity is when facial and dental disproportions are severe enough to be handicapping in function and/or social acceptability.

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4
Q

What % of the population have a dental deformity?

A

2.5% of the population

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5
Q

What system can be used to categorise the level of deformity?

A

Mild
Moderate
Severe
Extreme

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6
Q

What orthodontic tx is usually carried out for mild discrepancies?

A

No tx or orthodontic camouflage

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7
Q

What orthodontic tx is usually carried out for moderate discrepancies?

A

Camouflage or surgery

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8
Q

What orthodontic tx is usually carried out for severe discrepancies?

A

Accept or surgery

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9
Q

What orthodontic tx is usually carried out for extreme discrepancies?

A

Surgery

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10
Q

What are the indications for orthognathic surgery?

A
  1. Presence of a skeletal discrepancy:

(a) Anteroposterior:
- Class II or III

(b) Vertical:
- open bite
- deep bite
- vertical maxillary excess (gummy smile)

(c) Lateral:
- crossbites
- asymmetry

  1. Other clinical/psychological factors:

(a) Function
- eating
- speech
- TMD
- sleep apnoea

(b) Aesthetics:
- teasing and bullying
- social discrimination
- psychological distress

(c) Pain/discomfort:
- not due to jaws, may be to other issues

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11
Q

What factors must you consider as part of your case selection?

A
  1. Psychological status
  2. Family support
  3. Dental health
  4. Cooperation
  5. Age
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12
Q

On average what age does skeletal growth stop?

A

~18-20 years

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13
Q

Name 2 reliable indications that can be used to indicate that growth has stopped?

A

Height and shoe size - not changing over 1-2 years

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14
Q

When comparing females to males, which gender often completes skeletal growth first?

A

Females often complete skeletal growth before males (~1-2 years before)

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15
Q

List the team of individuals that may be involved in orthognathic surgery?

A
  1. Orthodontics
  2. Oral and Maxillofacial Surgery
  3. Clinical Psychology
  4. Restorative Dentistry
  5. Maxillofacial Technology
  6. Dental Hygienist
  7. Dietician
  8. Speech and language therapy
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16
Q

List the 7 steps of orthognathic surgery treatment process.

A
  1. Referral to ortho
  2. Assessment and diagnosis
  3. Joint clinic
  4. Pre-surgical orthodontics
  5. Orthognathic surgery
  6. Post-surgical orthodontics
  7. Retainers/review
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17
Q

What does the assessment and diagnosis stage involve during the orthognathic surgery tx process?

A
  1. Assessment of pt complaint
  2. Questions regarding family hx of discrepancies/malocclusions
  3. MH, DH, SH
  4. Clinical exam
  5. Special tests - radiographs, study models, clinical photographs, other imaging, psychological data/BMI
  6. Diagnosis
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18
Q

What can the cephalometric prediction software determine during orthognathic surgery treatment planning at the joint clinic?

A

It can determine:

  1. What orthodontic treatment is required pre-surgery - including extractions.
  2. Whether surgery is required in one or both jaws, +/- the chin.
  3. Where teeth will be positioned in relation to soft tissue in order to plan for retainers and adjunctive restorative treatment post-surgery
  4. The outcome of the surgery for the pt.
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19
Q

What does the orthognathic surgery psychological assessment (that is carried out at the joint clinic) involve?

A

A questionnaire and a referral to the clinical psychologist if required for psychological therapies throughout treatment.

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20
Q

What % of pts requiring orthognathic surgery, have psychological distress or a psychiatric disorder?

A

20%

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21
Q

What is the BMI cut off point at which pts cannot go undergo orthognathic surgery due to the risk of life following GA?

A

BMI >30

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22
Q

What values do the WHO classify for:
- Underweight
- Normal weight
- Overweight
- Obesity

A

Underweight = <18.5
Normal weight = 18.5-24.9
Overweight = 25-24.9
Obesity = >30

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23
Q

Why is pre-surgical orthodontics required before orthognathic surgery?

A

So teeth occlude properly at the time of surgery.

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24
Q

What does pre-surgical orthodontics (prior to orthognathic surgery) involve?

A
  1. Alignment
    - correction of crowding, spacing, and rotations.
  2. Decompensation
    - reverse orthodontics
  3. Coordination
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25
Q

How would you carry out decompensation for class II skeletal patten?

A

Procline retroclined upper incisors
Retrocline proclined lower incisors

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26
Q

How would you carry out decompensation for class III skeletal patten?

A

Retrocline proclines upper incisors
Procline retroclined lower incisors

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27
Q

In orthognathic surgery, what dictates extractions?

A

Crowding and decompensation

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28
Q

For Class II cases, which teeth would you extract during orthognathic surgery?

Clue - this is the opposite of non-surgical orthodontic cases!

A

Lower premolars

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29
Q

For Class III cases, which teeth would you extract during orthognathic surgery?

Clue - this is the opposite of non-surgical orthodontic cases!

A

Upper molars

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30
Q

What does pre-orthognathic surgery coordination involve?

A

Planned arch expansion or contraction to form a good occlusion with no crossbites

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31
Q

What last 4 steps are taken immediately before orthognathic surgery?

A
  1. High-quality impressions for study models and surgical template (wafer)
  2. Placement of hooks between each bracket for IMF during and after surgery
  3. DPT/Lateral Ceph (+ CBCT if necessary)
  4. Clinical photographs
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32
Q

How many surgical wafers are required if the patient is having orthognathic surgery for both jaws?

A

2 surgical wafers are required if pt is having surgery on both jaws:

  • Intermediate wafer = maxillary position
  • Final wafer = mandibular position
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33
Q

How long does the pt normally have to stay in hospital following orthognathic surgery?

A

1-3 nights

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34
Q

What method of anaesthesia is used for orthognathic surgery?

A

Endotracheal anaesthesia

35
Q

How long does the orthognathic surgery procedure take when operating on a single jaw compared to bimaxillary?

A

1 jaw = 2-3 hours
Bi-maxillary = 4-5 hours

36
Q

On average how many euros does the orthognathic surgery procedure cost?

A

6360 euros

37
Q

Which Le Fort fracture is most commonly used when undertaking orthognathic surgery on the maxilla?

A

Le Fort 1 (dentoalveolar segment)

38
Q

When would you used Le Fort 2 and 3 fractures in orthognathic surgery?

A

When managing a craniofacial deformity

39
Q

Name 4 different procedures that can be used in orthognathic surgery of the mandible.

A
  1. Bilateral sagittal split osteotomy
  2. Vertical subsigmoid osteotomy
  3. Body osteotomy
  4. Genioplasty
40
Q

Which mandibular orthognathic surgery method is the most versatile and untaken in the majority of Tayside cases?

A

Bilateral sagittal split osteotomy (BSSO)

41
Q

What does Bilateral sagittal split osteotomy (BSSO) involve?

A
  1. Making a cut from the medial aspect of the mandible just above the lingula (to avoid damaging the IAN)
  2. Extending the cut down the external oblique ridge to the inferior border of the mandible
  3. Identify mandibular nerve and protected before splitting of the mandible with a chisel or osteotome
  4. Move mandible forwards or backwards as required, fix into the final wafer and then fixate using plates and screws
42
Q

What is the main benefit of the Bilateral Sagittal Split Osteotomy (BSSO) technique?

A

Allows bone to bone contact - open graft is required

43
Q

When do you commence post-orthognathic surgery orthodontics?

And why?

A

Immediately on the ward before discharge.

As during the healing period the number of cytokines in and around the surgical site increase dramatically and allow orthodontic correction to be sped up.

44
Q

If the occlusion is good what can be done post orthognathic surgery?

A

Elastics can be placed to guide the occlusion into best fit

45
Q

If the occlusion is poor post orthognathic surgery, what must be done?

A

Pt must return to theatre to have the plates unscrewed, the bony segments repositioned and re-fixated in the correct position.

46
Q

When should you take your post-orthognathic surgery lateral ceph?

What are you assessing for in this lateral ceph?

A

A week or so after pt has been discharged to assess:

  • Skeletal changes that have taken place during surgery
  • To check that the surgery has gone to plan
  • To plan post-operative orthodontics
47
Q

How long is the patient monitored for post-surgery?

A

Monitored over a time period of 2 years

48
Q

What early, intermediate, and late complications can occur post orthognathic surgery?

A

Early:
- Bruising
- Swelling
- Pain/Discomfort
- Feeding
- Infection

Intermediate:
- Numbness in lips palate and tongue (100%) - reported by almost all pts

Late:
- Prolonged numbness (10%) - 1 in every 10 patients affected
- Relapse (partial/total)
- Infected screw/plate (12%) - 1 in every 8 patients, may require antibiotics and metal work removed
- Speech/TMD problems

49
Q

Removable appliances can be active or passive. List some examples of active components that can be utilised to move teeth in a removable appliance.

A

Springs
Biteplanes
Screws
Bows

50
Q

Name an example of a passive removable appliance that is useful for occlusal settling or if a pontic is required until a fixed prosthesis is placed.

A

Hawley retainer

51
Q

List 6 different types of removable appliance.

A
  1. Retainer
  2. Active plate
  3. Pre-surgical orthopaedics
    (cleft care)
  4. Space maintainer
  5. Interceptive appliance
  6. Functional appliance
52
Q

What are the advantages of removable appliances?

A
  1. Can be easily removed by the pt for OH and sports
    - good compliance req
  2. Increased anchorage - lower forces are being used as tipping is the main tooth movement that can be produced using this brace
  3. Easy to adjust
  4. Less iatrogenic damage
    - (e.g. root resorption and decalcification)
    - due to the lighter forces applied, and the ability to remove the brace to allow for tooth brushing.
  5. Baseplate can be modified
  6. Good at moving blocks of teeth
  7. Can be passive
  8. Lower cost than fixed appliance - even though lab is required
53
Q

If a pt that uses an upper removable appliance (URA) has poor OH and diet, where in the mouth might decalcification be observed?

A

Often seen on the palatal aspect where the acrylic meets the gingival margin, if diet and OH has been poor.

54
Q

What are the disadvantages of removable appliances?

A
  1. Need good patient compliance
  2. Limited movements
    - tipping
  3. Affects speech
    - palatal coverage normally creates a temporary lisp until the pt adapts over time
  4. Technician required
  5. Lower appliances are difficult to tolerate - as they encroach on the tongue space
  6. Inefficient at multiple tooth movements - often another appliance is required to make additional movements
55
Q

List the 4 components that make up a removable appliance:

A
  1. Active components
  2. Retentive components
  3. Anchorage
  4. Baseplate
56
Q

What length of 18/8 austenitic stainless steel wire is used to move a single tooth or groups of teeth in a removable appliance?

A

0.5mm or 0.7mm

57
Q

How does increasing the amount of SS wire in a removable appliance effect the forces exerted onto the teeth?

A

More wire = greater range of spring = lighter forces exerted onto teeth

58
Q

How can you increase the amount of wire in a removable appliance?

A

By incorporating loops or coils

59
Q

What formula would you use to calculate the force exerted by a spring in a removable appliance?

A

F = d.r4 / l3

F - force
D - deflection of the wire
R - radius of the wire
L - length of the spring

60
Q

How can you reduce the forces applied by SS wire in a removable appliance?

A

By increasing the length of the wire or reducing the diameter of the wire.

61
Q

What is the consequence of reducing the diameter of the wire/spring in a removable appliance?

A

It can make it more susceptible to distortion and breakage.

62
Q

How can you protect the arm of the spring in a removable appliance?

A

By shielding it with the acrylic or steel tubing

63
Q

If the radius of a stainless steel wire spring in a removable appliance was doubled how would this impact the force applied on the tooth?

A

Increasing the radius of the wire by 2 will result in the force applied increasing by 16 times.

64
Q

If the length of a stainless steel wire spring in a removable appliance was doubled how would this impact the force applied on the tooth?

A

Increasing the length of the spring by 2 will reduce the force applied by 8 times.

65
Q

What is the maximum range of force that is applied to each tooth by SS spring in a removable appliance?

A

No more than 25 - 40 grams per tooth

66
Q

Where should a spring in a removable appliance apply force to and why?

A

The spring should apply force as close to the centre of resistance as possible, to reduce the chance of the tooth rotating and excessively tipping

Therefore a spring should be adjusted so that it is as near to the gingival margin as possible without causing trauma to the soft tissues.

67
Q

List 4 examples of springs using in removable appliances.

A
  1. Palatal finger springs
  2. Buccal canine retractors
  3. Z springs
  4. T springs
68
Q

List 2 common used of screws in removable appliances.

A
  1. Expansion of arch to correct a buccal crossbite
  2. Distalisation of a buccal segment
69
Q

How much does each half move per quarter turn of the screw in a removable appliance?

A

0.25mm

70
Q

What are the advantages of using screws in removable appliances?

A
  1. Teeth that are clasped can be moved
  2. Can move multiple teeth at the same time
  3. Some screws can expand teeth in 2 or 3 directions
71
Q

In what case might a 3-way screw in a removable appliance be useful?

A

When there is a class III malocclusion with both buccal and anterior crossbites

72
Q

What are the disadvantages of screws in removable appliances?

A
  1. Can make the appliance bulkier
  2. Makes the appliance more expensive to fabricate and more expensive for the pt
  3. Less versatility as the teeth can only be moved in the direction of the screw
73
Q

How is retention of removable appliances achieved?

A

Through retentive components such as clasps and cribs

74
Q

List 5 examples of clasps and cribs that can be used in removable appliances to gain retention.

A
  1. Adams cribs
  2. Delta cribs
  3. Southend claps
  4. C clasps
  5. Ball hooks
75
Q

Which teeth are Adams Cribs and Delta Cribs mainly used on?

A

Molars and premolars

note - can also be used on incisors and canines

76
Q

Why are cribs less effective retentive components on primary teeth?

A

As there is less of an undercut

77
Q

Which clasp can be used as part of a removable prosthesis to aid expansion?

A

C clasp

78
Q

What is the difference between a ‘C’ clasp and a Southend clasp?

A

A ‘C’ clasp is the equivalent of a Southend clasp except it is divided into 2 to allow separation to occur.

79
Q

Where do ball hooks engage?

A

The interdental embrasure

80
Q

What diameter of SS wire is used for Adams’ cribs or delta clasps on a molar tooth in a removable appliance?

A

0.7mm

81
Q

What diameter of SS wire is used for Adams’ cribs or delta clasps on a premolar/deciduous tooth in a removable appliance?

A

0.6mm

82
Q

What diameter of SS wire is used for Southend clasps in a removable appliance?

A

0.6 or 0.7mm

83
Q

What diameter of SS wire is used for ball hooks in a removable appliance?

A

0.7mm diameter with a soldered ball on the end.

84
Q
A

Module 8 (6 decks)

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