Developmental anomalies in orthodontics

Question 1

What are supernumerary teeth?

Answer 1

A tooth (or tooth like structure) that is additional to the normal series

Question 2

What is the incidence of supernumeraries?

Answer 2

Low, 35% of cases in the primary dentition are superseded by supernumerary in the permanent. They are 2x as common in males and 5x more common in the maxilla than mandible.

Question 3

How do we classify supernumeraries?

Answer 3

Supplemental - extra tooth of normal ish form
Conical - generally early forming and peg shaped
Tuberculate - generally late forming and barrel shaped

Question 4

What is an odontome and how are they classified?

Answer 4

A mass of dental structures
Compound - containing many small separate tooth like structures (denticles) - usually found anteriorly
Complex - a large mass of disorganised enamel and dentine - usually found posteriorly

Question 5

Classification by site of supernumeraries?

Answer 5

Mesiodens - midline between the central incisors
Paramolar/parapremolar - adjacent to the molars/premolars
Distodens/distomolar - distal to the arch

Question 6

What are conical supernumeraries?

Answer 6

Peg shaped
Mesiodens if on the midline - can cause diastema
Root formation ahead or with permanent incisor
Unlikely to impede eruption or may itself erupt
If high and will not interfere with orthodontic treatment, it can be left
If on the palate it can be removed under LA as it can be difficult to clean
Risk of cystic change or resorption low

Question 7

What are tuberculate supernumeraries?

Answer 7

Barrel shaped
Root formation is delayed compared to permanent incisor
Usually palatal
More likely to impede eruption
Often occur in pairs
Usually need to be removed - usually surgical

Question 8

What are the associated conditions with supernumeraries?

Answer 8

• cleft lip and palate
• gardner’s syndrome - causes multiple polyps in the colon and osteomas - tumours in the skull
• cleidocranial dysostosis - inherited/new mutation gene, collarbones completely/partly missing and hyperplastic maxilla

Question 9

What are the problems with supernumeraries?

Answer 9

• impede eruption of other teeth
• cause displacement or rotation of erupted teeth
• produce spacing between erupted teeth
• contribute to crowding if they erupt
• undergo cystic change

Question 10

What is hypodontia?

Answer 10

The developmental absence of one or more teeth <6

Question 11

What is the most common tooth to be missing in hypodontia?

Answer 11

L5’s > U2’s > U5’s > L1’s

Question 12

Is hypodontia more common in women or men?

Answer 12

Women 3:2

Question 13

What is oligodontia?

Answer 13

Absence of >6 teeth

Question 14

What is anodontia?

Answer 14

Absence of all teeth

Question 15

What are the associated conditions with hypodontia?

Answer 15

Cleft lip and palate
Downs syndrome
Ectodermal dysplasia - defects of hair, skin, nails, sweatglands

Question 16

What is the treatment options for hypodontia?

Answer 16

Open the gap with orthodontics and replace with bridge, denture, implant or close the gap and camouflage teeth

Question 17

What is microdontia?

Answer 17

Teeth which have smaller than average dimensions - range from mildly to severely microdont
Can affect the crown, root or whole tooth
Upper 2’s are mostly affected - peg shaped laterals - can often see this in one upper 2 and then the other lateral incisor missing

Question 18

What are the treatment options for microdontia?

Answer 18

Accept - generally done if mild or in a less aesthetically pleasing area
Create space to have the microdont teeth built up - composite, veneer, 3/4 crown
Extract the microdont tooth and close the space and adjusting canine to look like a lateral

Question 19

What is macrodontia/megadontia?

Answer 19

Teeth which have larger than average dimensions
Can affect the crown, the root or the whole tooth
Upper 1’s/lower 5’s are most commonly affected - often bilateral
Often but not always can be differentiated from a double tooth by lack of coronal notching and normal pulpal form

Question 20

What are treatment options for macrodontia?

Answer 20

Accept - generally done if mild or in a less aesthetically challenging area (lower 5’s)
Extract and reduce space for a normally sized prosthesis
Extract and close space
Camouflage restoratively to resemble 2 teeth (If a very large upper 1 and missing upper 2) eg crown

Question 21

What are double teeth?

Answer 21

Fusion of 2 separate tooth germs leading to a reduced number of teeth in the arch
Gemination - developmental separation of a single tooth germ
More common in primary (0.5-1.6%) than secondary (0.1-0.2%) dentition and anteriorly rather than posteriorly
Clinically varies from a small notch on a wide crown/root to 2 apparently separate crowns with a shared root
Concrescence - fusion of the roots only (freq terminal molars)

Question 22

What are the treatment options for double teeth?

Answer 22

Generally no intervention needed in the primary dentition
Be wary of caries at the interface between the 2 crown segments, especially if extending subgingival - may want to restore any notch for aesthetic and preventative reasons - flowable composite
If 2 separate root canals - can surgically divide - specialist
Extraction - if caries into the pulp, replacement and closure of space depending on malocclusion

Question 23

What is invagination?

Answer 23

An enamel lined ‘infolding’ in the crown of a tooth, which can extend into the root
Produced by an invagination of the enamel epithelium into the dental papilla during development
Upper 2’s most commonly affected, followed by upper 1’s
Milder forms appear similar to a deep cingulum pit (Dens invaginatus)
In more severe forms the invagination starts at the incisal edge (dens in dente) and can lead to a grossly abnormal crown and root

Question 24

What is the management of invagination?

Answer 24

Although defects are generally enamel lined it can be quite poor and thin
Difficulty cleaning means high caries risk and bacterial ingress to the pulp leading to pulpal disease
Can try to maintain less severe forms with adhesive restorations (fissure sealants, small composites) - early intervention is key
Can attempt RCT but often challenging due to abnormal morphology
If grossly abnormal, extraction may be best with closure of prosthetic replacement

Question 25

What are accessory cusps?

Answer 25

Additional outward projections of enamel and dentine off the body of the tooth proper.
Fairly common - cusp of Carabelli
Talon cusp - on maxillary incisors - check for caries at the interface
Size and pulpal involvement varies
If causing occlusal interferences - may need to be reduced - if extensive reduction may require a pulpotomy (take PA)

Question 26

What is a dilaceration?

Answer 26

An abrupt deviation along the long axis of the crown or root
Upper incisors most commonly affected, can lead to failure of eruption
Management: if less marked divergence, can expose, bond traction and attempt orthodontic alignment - need to consider where the root will end up once the crown is aligned (if at right angle to crown may end up coming through labial sulcus)
If more significant will likely need to remove - extraction can be challenging.

Question 27

What are the causes of dilaceration?

Answer 27

Traumatic - due to intrusion of primary incisor into developing tooth germ
Position of dilaceration corresponds with stage of development at time of trauma
Generally crown angled palatally and hypoplasia at the site of dilaceration

Developmental - may be due to an obstruction of the eruption path
- generally crown angled upward and labially and no hypoplasia is seen
Upper 1’s most affected

Question 28

What is delayed eruption and when do we investigate?

Answer 28

When a tooth has not erupted in line with normal timings, if a tooth hasn’t erupted 6 months after its contralateral, investigate
Localised delays often do require intervention

Question 29

What are causes of delayed eruption?

Answer 29

Cleidocranial dysplasia, down syndrome, cleft lip and palate, hereditary gingival hyperplasia
Crowding, supernumeraries, trauma, ectopic tooth germ, early loss of primary teeth, retention of primary teeth, local pathology and transpositions

Question 30

What are ectopic teeth?

Answer 30

teeth in an abnormal place or position

Question 31

What are impacted teeth?

Answer 31

Physical impediment to eruption by another structure sucj as bone, adjacent teeth and soft tissues.

Question 32

Which directions will impacted teeth come out?

Answer 32

Upper - palatal
Lower - lingual

Question 33

What are the causes of unerupted upper canines?

Answer 33

Genetic - family history, > frequency bilateral than expected, associated malformations
Guidance theory - missing or absent lateral incisor, retention of primary canine and crowding

Question 34

What are the consequences of unerupted upper canines?

Answer 34

Root resorption - up to 2/3rds of U2’s have root resorption when U3’s are ectopic
Most root resorption occurs before 14

Coronal resorption - most likely in adults
Cystic change - generally thought to be low risk

Question 35

When do we screen for maxillary canines?

Answer 35

Majority of the normal erupting canines should be palpable in the buccal sulcus by 10 years old, start palpating at 9.
If you cannot palpate by 10 consider referral

Question 36

When are eruptions of canines considered late?

Answer 36

12.3 - girls
13.1 - boys

Question 37

What is a mechanical failure of eruption (ankylosis)?

Answer 37

Uncommon isolated condition causing a localised failure of eruption of a single tooth with no other identifiable causes.
Other teeth are apparently normal, may appear to submerge due to the vertical growth of the alveolar complex and other teeth surrounding - tooth gets fused into bone and is infraoccluded. Teeth fail to respond to orthodontic forces.

Question 38

What is primary failure of eruption?

Answer 38

Rare isolated condition causing localised failure of eruption of multiple teeth with no other identifiable causes.
- Primarily affects posterior teeth
- Affects all teeth posterior to the most anteriorly affected tooth leading to a lateral open bite and the teeth fail to respond to orthodontic forces so require restorative options to manage

Question 39

What is cleft lip and palate?

Answer 39

Congenital disorder affecting the lip and palate affecting males more than females

Question 40

What is cleft palate?

Answer 40

An isolated congenital condition affecting just the palate and affecting females more than males

Question 41

What syndromes are associated with CLP?

Answer 41

Treacher collins, van der Woude, hypohydrotic ectodermal dysplasia and Down syndrome.

Question 42

What is a characteristic of Van der Woude?

Answer 42

A pitting of the lower lip

Question 43

What is Down Syndrome?

Answer 43

Trisomy of chromosome 21

Question 44

What are the key dental findings of patients with Down Syndrome?

Answer 44

Class III malocclusion - maxillary hypoplasia
Hypodontia
CLP
Microdontia
Delayed eruption of secondary dentition
Short roots

Question 45

Hypohydrotic ectodermal dysplasia

Answer 45

Smooth dry skin with sparse hair with total or partial absence of sweat glands.

Question 46

What are the dental findings of hypohydrotic ectodermal dysplasia?

Answer 46

Class III malocclusion
Anodontia/severe hypodontia
Deformed teeth/conical crowns
Delayed eruption
Xerostomia
CLP