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Orthodontics > Aetiology of Malocclusion > Flashcards

Aetiology of Malocclusion Flashcards

1
Q

What are the 3 types of skeletal variation?

A

Antero-posterior
Vertical
Transverse

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2
Q

In cephalometrics what does SNA relate to?

A

Relates maxilla to anterior cranial base

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3
Q

In cephalometrics what does SNB relate to?

A

Relates mandible to anterior cranial base

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4
Q

In cephalometrics, what does ANB relate to?

A

Relates the mandible to maxilla

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5
Q

What is the definition of local causes of malocclusion?

A

A localised problem or abnormality within either arch, usually confined to one, two or several teeth producing a malocclusion

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6
Q

What are some local causes of malocclusion?

A

Variation in tooth number
Variation in tooth size or form
Abnormalities of tooth position
Local abnormalities of soft tissues
Local pathology

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7
Q

What can cause a variation in tooth number?

A

Supernumerary teeth (extra)
Hypodontia (developmentally absent teeth)
Variation of Timing
–Retained primary teeth
–Early loss of primary teeth
–Unscheduled loss of permanent teeth

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8
Q

What is a supernumerary tooth?

A

A tooth or tooth-like entitity which is additional to the normal series

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9
Q

What are the 4 types of supernumerary teeth?

A

Conical
Tuberculate
Odontome
Supplemental

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10
Q

What is a conical supernumerary tooth?

A

Small, peg shaped
Occurs close to the midline (mesiodens)
May erupt (extract if so)
Usually 1 or 2 in number
Tend not to prevent eruption but may displace adjacent teeth

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11
Q

What is a tuberculate supernumerary tooth?

A

One of the main causes of failure of eruption of permanent upper incisors
Tend not to erupt
Paired
Barrel-shaped
Usually extracted

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12
Q

What are supplemental supernumerary teeth?

A

Extra teeth of normal morphology
Most often upper laterals or lower incisors
Often extract- decision based on form and position

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13
Q

What is an odontome supernumerary tooth?

A

Compound
-discreet denticles (tooth like objects in a mass)
Complex
-disorganised mass of dentine, pulp and enamel

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14
Q

What is the definition of hypodontia?

A

Developmental absence of one or more teeth

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15
Q

What is counted as a Retained Primary Teeth?

A

A disruption in the sequence of eruption
A difference of more than 6 months between the shedding of contra-lateral teeth

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16
Q

Why are some primary teeth retained?

A

There is an absent successor
Ectopic successor or dilacerated
Infra-occluded (ankylosed) primary molars
–ankylosed primary teeth remain in a fixed position, while the adjacent teeth continue to erupt, moving occlusally
Dentally delayed
Pathology/supernumerary

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17
Q

What to do if there is an absent successor?

A

Either maintain the primary tooth as long as possible (if there is a good prognosis)
Or extract deciduous tooth early to encourage spontaneous space closure in crowded cases

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18
Q

What is an infra-occluded primary tooth?

A

Submerged
Definition
–Process where a tooth fails to achieve or maintain its occlusal relationship with adjacent teeth
Temporary ankylosis

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19
Q

What is a balancing extraction?

A

By extraction of a tooth from the opposite side of the same arch
Designed to minimise midline shift

20
Q

What is a compensating extraction?

A

By extraction of a tooth from the opposing arch of the same side
Designed to maintain occlusal relationship

21
Q

What factors influence the impact of the loss of 6s?

A

AGE AT LOSS
-upper arch: less important
-Lower arch
–If 7’s erupted late there is often poor space closure
CROWDING
-Upper arch, potential for rapid space loss
-Lower arch,
–spaced- will have spaces
–aligned- will have spaces
–crowded- best results likely
MALOCCLUSION

22
Q

What causes a variation in tooth size or form?

A

Macrodontia- too large
Microdontia - too small
Abnormal form

23
Q

What is microdontia?

A

Tooth/teeth smaller than average
Localised or generalised
Leads to spacing
Linked to hypodontia

24
Q

What is macrodontia?

A

Tooth/teeth larger than average
Localised or generalised
Problems
-Crowding
-Asymmetry
-Aesthetics

25
Q

What are examples of abnormal form of teeth?

A

Peg shaped laterals
Dens in dente
Germinated/fused teeth
Talon cusps
Dilaceration
Accessory cusps and ridges

26
Q

At what age can you bucally palpate canines from?
Why do this?

A

9 years onwards
Check for ectopic maxillary canines

27
Q

What incisor relationship are ectopic canines more likely in?

A

Class II division2 incisor relationship

28
Q

What 2 radiographs are normally used to localise position of an ectopic canine?
What technique is used?

A

OPT and upper anterior oblique occlusal
Parallex technique
- 3 P’s, Presence, Position, Pathology

29
Q

What are the management options for ectopic canines?

A

Extraction of C to encourage improvement in position of 3 (interceptive)
Retain 3 and observe
Surgical exposure and orthodontic realignment
Surgical extraction
Autotransplantion

30
Q

What is the prevention for ectopic canines?

A

Appropriate monitoring from age 9 onwards
Clinical assessment
Symmetry

31
Q

What are ectopic first molars a sign of?

A

Crowding
Mesial path of eruption
Abnormal morphology of E

32
Q

What is the management of ectopic 6’s?

A

Attempt to distalise 6’s
Extract E
Separator

33
Q

What is a transposition?
Definition

A

Interchange in the position of two teeth

34
Q

What are the treatment options for a transpositioned tooth?

A

Accept
Extract
Correct

35
Q

What can a labial fraenum cause?

A

A median diastema

36
Q

How does mandibular displacement occur?

A

Occurs where inter-arch width discrepancy causes upper and lower posterior teeth to meet cusp to cusp
Mandible is then forced to deviate to one side to achieve a position of inter-cuspation
Means mandible displaces from midline to achieve occlusion

37
Q

What is a dental cause of facial asymmetries?

A

Displacement of normal mandible due to unilateral cross-bite

38
Q

What is hemi-mandibular hyperplasia?

A

Asymmetry, increase in ramus height, rotated facial appearance and prominence of the lower border of the mandible

39
Q

What is hemi-mandibular elongation?

A

Horizontal displacement of the mandible and chin on affected side

40
Q

What is condylar hyperplasia?

A

Over enlargement of the mandible

41
Q

What is dento-alveolar disproportion?

A

Discrepancy between size of teeth and jaws

42
Q

What can crowding be caused by in dento-alveolar disproportion?

A

Small jaws, normally sized teeth
Large teeth (macrodontia)

43
Q

What can spacing be caused by in dento-alveolar disproportion?

A

Large jaws, normally sized teeth
Small teeth (microdontia)

44
Q

How do you assess anteroposterior relationship
Extra-oral?
Intra-oral?

A

Extra oral
-Maxilla to mandible relation
Intra-oral
-incisor classification
-overjet
-canine relationship
-molar relationship
-anterior crossbite

45
Q

How do you assess vertical relationship
Extra-oral?
Intra-oral?

A

Extra-oral
-in facial thirds
-angle of lower border of mandible to maxilla
Intra-oral
-centrelines
-posterior crossbite

46
Q

How do you assess transverse relationship
Extra-oral?
Intra-oral?

A

Extra-oral
-facial symmetry
Intra-oral
-overbite
-anterior open bite

47
Q

What is the difference between overbite and overjet?

A

Overbite- Lower jaw too far behind upper jaw
Overjet- extent of horizontal overlap between maxillary central incisors and mandibular central incisors

Orthodontics (7 decks)

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