Unerupted Ectopic Canines/Incisors

Question 1

How can adult teeth be distinguished from deciduous?

Answer 1

 Darker colour
 Less wear
 Mamellons
 Longer length of root compared to deciduous on OPT (look in relation to other teeth)

Question 2

When do upper canines tend to erupt?

Answer 2

Girls- 11-12

Boys- 12-13

Palpate and check for canines from age 9

Question 3

What are the signs of abnormal dental development?

Answer 3

 Lack of symmetry- contra-lateral does not erupt within 6 months

 Sequence- are they coming through in correct order (4->5->3- usually, if crowded sometimes 5 comes in last)

Question 4

What are the steps in the development path of Upper 3?

Answer 4

 Starts up high in alveolus above root of lateral incisors

 Moves slightly buccal and passes down lateral side of 2

 Sometimes canine can erupt in path in line with arch right on top of deciduous tooth
-> Assess mobility of deciduous canines and palpate for canines in buccal sulcus

Question 5

What are the signs of ectopic canines seen in lateral incisor?

Answer 5

Mobile lateral- due to root resorption

DP tipping

Question 6

What is a peg lateral?

Answer 6

Lateral incisor that is narrower at incisal edge than at gingival margin

Question 7

What is the incidence of ectopic canines?

Answer 7

1-2%

Question 8

What type of imaging may be helpful for ectopic canines after taking plain radiographs?

Answer 8

CBCT
 Root resorption cases- extra detail
 Unsure about exact position in relation to other teeth
-> Consider if there a path of traction/scope to surgically remove

Question 9

What are the causes of impacted canines?

Answer 9

 Crowding (buccal impaction is commonly due to crowding- as canine is last tooth in 345 sequence- pushed out of line if short of space, not all though)

 Genetics- familial but not direct, females

 Associated with other dental anomalies- class II div II, hypodontia, missing laterals (lack of guidance)

 Long path of eruption
-> palatal canines tend to get stuck

 Ectopic position of tooth germ

Question 10

What is the IOTN score for missing unerupted tooth?

Answer 10

5i

Question 11

When may you have to accept the position of unerupted ectopic canine?

Answer 11

XLA Uc unlikely to make much difference U3

Positioned mesial to the midline of U2

Patient above age where interceptive treatment for ectopic canine is likely to work (window of opportunity 10-13)

Insufficient space for U3

Question 12

What are the risks of doing nothing with ectopic canines?

Answer 12

Resorption of the roots of adjacent teeth (40% risk of lateral incisor root resorption)

Resorption of the canine crown (14%)

Ankylosis of the unerupted canine

Eventual loss of primary canine and complex restorative solutions being required in the future

Cystic change of canine (rare)

Question 13

When may an ectopic canine be surgically removed?

Answer 13

If case deemed to be not alignable:
-> Too high above apical third of incisor roots
-> Too close to dental midline
-> Angle greater than 55 degrees to midsagittal plan

If there is no significant risk of damaging the adjacent teeth during a surgical procedure

Patient is happy with the dental appearance and the retained primary canine has a good long term prognosis

Radiographic evidence of early root resorption of the adjacent teeth

Patient does not want to wear orthodontic appliances

Question 14

What are the steps in surgical exposure and fixed appliance treatment for ectopic canines?

Answer 14

Make sufficient space for the tooth
-> retained deciduous canine may require removal.

Surgically expose the canine
-> Open or closed exposure depending on site of canine

Orthodontic traction
-> gold chain (closed exposure)
-> Traction hook for an open exposure

Upper and Lower fixed appliances
-> may need palatal arch due to high anchorage demand

Fixed and removable retainers

Question 15

When may autotransplantation be indicated for ectopic canines?

Answer 15

Malposition of the tooth is too great for orthodontic alignment to be possible

No evidence of ankylosis

Canine root development is ideally 2/3 to 3/4 length

Patient is looking for a quicker treatment option

Question 16

What are the risks of autotransplantation in ectopic canines?

Answer 16

Difficult to remove atraumatically

Requires RCT

High risk of root resorption and ankylosis

Question 17

Why should you refer patient with ectopic canines to see orthodontic specialist?

Answer 17

Patient has high treatment need- 5i

Significant risks to dental health if you do nothing

Fixed appliance treatment is likely to be required

Question 18

What special investigations can be useful for patient with unerupted central incisors?

Answer 18

Anterior occlusal maxilla or periapicals

+/- Orthopantomogram *
Bitewings to assess for caries

-> CBCT subject to the findings on the plain films

Question 19

What position are ectopic 1s usually in?

Answer 19

Buccal

Question 20

What are the local causes of unerupted centrals?

Answer 20

Unerupted supernumerary – most common reason for a delayed upper central incisor

Retained primary tooth

Early loss of primary tooth

Trauma to the deciduous tooth leading to dilaceration of the unerupted tooth

Crowding

Ectopic position of the tooth germ

Question 21

How does dilaceration of permenant successor occur?

Answer 21

Damage to deciduous tooth causing it to impinge on permanent tooth germ making root go different direction

Can also occur due to supernumeraries

Question 22

What syndromes are associated of unerupted or delayed eruption in 1s?

Answer 22

Down Syndrome

Cleidocranial dysostosis

Cleft lip and palate

Hereditary gingival fibromatosis

Turner syndrome

Rickets

Question 23

What are the treatment options for unerupted centrals?

Answer 23

Accept

Bring central into line of arch

Remove unerupted central

Question 24

Why is accepting position of unerupted central not advisable?

Answer 24

Effect of a large anterior space on facial and dental aesthetics may harm the patient’s self-esteem and social interaction

Drift of adjacent teeth can make future orthodontic and restorative treatment more complicated

If an unerupted tooth is left in situ there is a risk of movement of the tooth towards adjacent tooth roots and subsequent root resorption of adjacent teeth

Risk of cyst formation (rare)

Question 25

How is the unerupted central brought into the line of the arch?

Answer 25

Make sufficient space for the tooth (may require fixed appliance or URA)
-> if position of unerupted tooth is favourable and the patient is aged 9, wait a year to see if tooth erupts spontaneously

Surgically expose tooth- usually closed exposure (buccally) with gold chain attached to palatal surface of the tooth at time of surgery

Apply traction by adding gold chain to fixed appliance
-> traction can begin after two weeks

Question 26

What are the risks of bringing an unerupted central into the line of the arch?

Answer 26

Tooth fails to erupt/move

Ankylosis of central incisor

External root resorption

Poor result in gingival aesthetics

Question 27

What are the indications for removing an unerupted central incisor?

Answer 27

Patient not keen on complicated and prolonged orthodontic/minor oral surgery tx

If the unerupted tooth fails to respond to the orthodontic traction (i.e. ankylosed)

Severe dilaceration so not possible to align tooth within the bone

Question 28

What are the risks of removing unerupted central incisor?

Answer 28

Damage to adjacent tooth roots

Loss of space in arch for prosthodontics in future if it is not managed

Loss of alveolar bone- issues with bridges and implants in future

Question 29

What can be used to replace unerupted central if it removed?

Answer 29

Move 2 into position of 1 and restore to appear like a 1

Ortho treatment to open space for RBB, implant, denture

Autotransplantation- if poor prognosis of central and premolars require extraction to address other aspects of malocclusion

Segmental osteotomy

Do nothing more and allow further mesial drift of UR2, UL1
-> If patient <9 years you may get quite a bit more space closure
-> Space could be reopened at a later date with Orthodontic appliance treatment

Question 30

What is primary failure of eruption?

Answer 30

Failure of eruption with no identifiable local or systemic cause (can occur in partially erupted teeth)
-> Eruption process has been disturbed

Question 31

What is the issue with orthodontic force in teeth with primary failure of eruption?

Answer 31

It may precipitate ankylosis of the tooth

Question 32

What are the features of primary failure of eruption?

Answer 32

Unilateral or bilateral

Lateral open bites

Posterior teeth most frequently affected

Question 33

What is the prevalence of primary failure of eruption?

Answer 33

0.06%

Question 34

What gene mutation is associated with primary failure of eruption?

Answer 34

Parathyroid hormone 1 receptor (PTH1R) gene