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Minor Oral Surgery > Impacted Canines 2 > Flashcards

Impacted Canines 2 Flashcards

1
Q

What are the four categories of canine position?

A
  • canine overlap with adjacent incisor
  • vertical canine height
  • angulation to midline
  • position of canine root apex
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2
Q

What is an impacted tooth?

A

one that is prevented from erupting into position because of malposition, lack of space or other impediments

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3
Q

Impacted canines have been shown to occur twice as commonly in females as males. True or false

A

True

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4
Q

The majority of canine impactions are bilateral. True or false

A

False

(92% unilateral)
(8% bilateral)

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5
Q

Why is the canine often regarded as the “corner stone of the maxillary arch”?

A
  • long root and good bony support, beneficial for lateral excursion
  • excellent abutment tooth for fixed and removable prostheses
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6
Q

When does canine development commence?

A

4- 5 months of age

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7
Q

How long is the path of eruption of a canine ?

A

22mm

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8
Q

When does crown calcification of the permanent maxillary canine begin?

A

1 year

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9
Q

When is crown calcification of the maxillary permanent canine complete?

A

between 5- 6 years of age

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10
Q

Where does canine development commence ?

A
  • high in the maxilla
  • lateral to the piriform fossa
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11
Q

What is the path of migration/eruption of the maxillary permanent canine?

A

migrates forward and downwards to lie buccal and mesial to the apex of the deciduous canine

it continues to move down the distal aspect of the root of the maxillary lateral incisor

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12
Q

What is a potential consequence of canine eruption into position ?

A

closure of median diastema

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13
Q

What are the ways in which canine displacement can be classified?

A
  • palatally
  • buccally
  • in line the arch

occasionally they can be seen lying horizontally over apices of the maxillary incisor

they may also be found displaced near the nose

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14
Q

What class of canine displacement often has sufficient space to erupt ?

A

palatally displaced canines

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15
Q

What class of canine displacement often has insufficient space to erupt ?

A

buccally displaced canines

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16
Q

What is the main aetiological factor for buccally displaced canines?

A

crowding

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17
Q

What theories have been suggested to address the aetiology of palatally impacted canines?

A
  • guidance theory
  • genetic theory
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18
Q

What is the guidance theory?

A
  • the guidance theory suggests that the distal aspect of the lateral incisor is the guide for canine eruption
  • a study by Becker found that palatally impacyed canines were found to be closely associated to spaced dentitions and lateral incisors that are peg-shaped/incisors of small mesiodistal width/incisors that are congenitally absent

most cases in the Becker study were associated with anomalous lateral incisors

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19
Q

What does the genetic theory describe?

A
  • it considers that impacted canines are a product of poly-genetic multifactoral inheritance
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20
Q

What is the genetic theory of palatally impacted canines based on ?

A

the fact that palatally displaced canines are concomitant with other dental anomalies such as
* peg laterals
* lateral premolar hypodontia
which occur bilaterally

  • there is also a gender, familial and population difference in occurence
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21
Q

State some factors that have been documented in the multifactorial aetiology for impacted canines

A
  • presence of supernumeraries
  • odontomes
  • pathological lesions e.g. cysts
  • delayed exfoliation of deciduous canine (thought to be an indicaator rather than a cause)
  • early trauma to maxilla
  • cleft lip and palate
  • ankylosis
  • displacement of crypt
  • long path of eruption
  • syndromes e.g. cleidocranial dysplasia
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22
Q

A distally inclined lateral incisor may be indicative of … impaction

A

palatal

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23
Q

A mesially inclined lateral incisor is indicative of … impaction

A

buccal

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24
Q

The colour and mobility of the deciduous canine tooth should be assessed. They may give an indication of …

A

root resorption

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25
Q

When is radiographic assessment indicated for assessment of eruption ?

A
  • assymetry on palpation
  • pronounced difference in eruption of canines between left and right
  • if canines cannot be palpated in their normal position and occlusal development is advanced
  • lateral incisor late erupting
  • lateral incisor shows pronounced buccal displacement or proclination
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26
Q

Palpation of canine region should begin at…

A

8 years old

27
Q

When should lack of positive palpation become abnormal ?

A

> 10 years old

28
Q

What dimensions are required radiographically to view impacted canines? Why are these dimensions required

A
  • vertical
  • mesio-distal
  • bucco-palatal
  • to evaluate relationship to the midline
  • to evaluate relationship with adjacent teeth
  • evaluate resorption
29
Q

What radiographic views are commonly used to assess ectopic canines?

A
  • panoramic
  • periapical
  • cephalometric
  • lateral skill
  • maxillary occlusal
30
Q

How many views are required to localise impacted canines in a bucco-lingual plane?

A

2

31
Q

What are the most common means of radiographic localisation of impacted canines ?

A
  • parallax
  • CBCT
32
Q

What is the preferred means of localisation of impacted canines?

A

parallax

33
Q

Briefly describe what parallax is?

A

the apparent displacement of an image relative to the image of a reference object caused by an actual change in the angulation of the x-ray beam

34
Q

What is often the reference object in parallax imaging of impacted canines?

A

the root of an adjacent tooth

35
Q

Briefly outline the SLOB rule

A

same lingual, opposite buccal

  • the image of a tooth that is further away from the x-ray tube moves in the same direction of the tube
  • the image of a tooth that is closer to the x-ray tube moves in the opposite direction of the tube
36
Q

What types of radiographs can be used to obtain a vertical parallax ? Why is this a vertical parallax?

A
  • OPG
  • Anterior occlusal radiograph
  • The angulation of the beam changes in the vertical plane from 8 degrees for an OPG to 60 degrees on an anterior occlusal
37
Q

What type of radiographs can be used to achieve a horizontal parallax?

A
  • two periapicals
  • periapical and an anterior occlusal radiograph
38
Q

What radiographic technique has greater sensitivity for palatally impacted canines?

A

horizontal parallax

39
Q

CBCT was designed to overcome some shortcomings of the conventional CTs. State one such limitation

A

with conventional CTs a high dose of radiation is required to produce a complete image

40
Q

The radiation from CBCTs is equivalent of …

A
  • 20% of conventional CTs
  • full mouth periapicals
41
Q

Briefly describe how CBCT works

A
  • uses a cone shaped X-ray beam to acquire a volumetric dataset of the region of interest
  • computed image reconstruction then produces 3D images at high resolution
42
Q

What is a common problem in orthodontics regarding unerupted teeth (especially canines)?

A

underestimation of the degree of resorption associated with the unerupted teeth

43
Q

What is the benefit of using CBCT over plain radiographs for imaging unerupted teeth?

A

CBCT increases detection of resorption by 50%

44
Q

What is the cause of underestimation of resorption associated with unerupted teeth when using plain radiographs?

A

this is due to the superimposition of the incisor roots and the crown of the impacted canine obsuring the morphology

45
Q

What is an important consideration forclinicians prescribing CBCT?

A

as outlined by IR(ME)R 2000 and british orthodontic society, there is a need to report all the image data, including those areas that are outside of the jaw

46
Q

What are the possible consequences of impacted canines?

A
  • cyst formation
  • internal resorption of impacted tooth
  • external resorption of impacted tooth
  • ankylosis
  • infection and migration of neighbouring teeth with loss of arch length
47
Q

What groups are at increased risk of resorption and pathology associated with impacted teeth?

A
  • females
  • > 14 years
  • angulation of canine to midline is >25 degrees
48
Q

What is postulated to be the most likely cause of root resorption associated with impacted canines?

A
  • inherent pressure due to migration of the displaced erupting canine

PLUS

  • physical contact between the root of the incisor and the prominences of the canine crown
49
Q

Some studies have shown tha once an impacted canine has been moved away, there is no further risk of resporption. True or false

A

true

50
Q

What are the main requirements of interceptive treatment of impacted canines?

A
  • extraction of deciduous canine should be between 10-13 years old
  • No crowding should be present
51
Q

According to Baccetti et al, what was shown to be an effective method for increasing the rate of eruption of impacted canines?

A

use of:

  • rapid maxillary expander (space resolution ?)
  • cervical pull headgear
52
Q

The success of interceptive treatment depends on …

A
  • degree of impaction
  • age at diagnosis
  • canine position
53
Q

Orthodontic opinions should always be sought before embarking upon interceptive treatment. True or false

A

True

54
Q

What are the four aspects of canine position that should be assessed for interceptive management?

A
  • amount of crown that horizontally overlaps with adjacent incisor
  • vertical height of the crown
  • canine angulation towards th midline
  • position of the canine root apex in horizontal plane
55
Q

Outline where there is good, average and poor prognosis regarding impacted crown overlap with the incisor

A
  • Good prognosis - no overlap
  • average prognosis- overlap up to half of incisor root width
  • poor prognosis- complete overlap of impacted canine over incisor root
56
Q

Outline when there is good, average and poor prognosis of regarding the vertical height of an impacted crown

A
  • good prognosis- crown is at CEJ/half way up the incisor root
  • average prognosis- crown is > half way up the root but below the full root length
  • poor prognosis- crown is above the full root length
57
Q

Outline when there is good, average and poor prognosis of regarding the angulation of the impacted canine

A
  • good prognosis - 0-15 degrees towards the midline
  • average prognosis- 16-30 degrees toward the midline
  • poor prognosis >30 degrees toward the midline
58
Q

Outline when there is good, average and poor prognosis of regarding the position of the apex of the impacted canine

A
  • good prognosis- if the impacted canine apex is above the canine position
  • average prognosis- apex above the 1st premolar position
  • poor prognosis- apex above the second premolar position
59
Q

According to the criteria in the RCS England guidelnes on the management of palatally ectopic maxillary canines, when is it clincally suitable for the orthodontist to make the decision to extract the deciduous canine?

A

if the impacted canine prognoss is good in all four categories required for interceptive treatment

60
Q

Following interceptive treatment, if the canine fails to erupt or improve within ____ months, what treatment will most likely be required?

A
  • 12 months
  • surgical exposure and alignment
61
Q

When is prognosis for impacted canines considered to be average?

A
  • 2 categories suggest a good prognosis
  • 2 catergories suggest an average prognosis
62
Q

Definitive treatment for an impacted canine with an average prognosis could be the extraction of the (impacted) canine. What factors does this depend on?

A
  • overall malocclusion
  • patients age
  • crowding
  • condition of dentition
63
Q

When is orthodontic treatment essential when managing impacted canines ?

A
  • when criteria suggests a poor prognosis
  • evidence of pathology
  • in these cases deciduous canine should not be removed

Minor Oral Surgery (36 decks)

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