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Ortho > Aetiology of Malocclusion > Flashcards

Aetiology of Malocclusion Flashcards

1
Q

What is considered a relevant feature to indicate the possibility of an unerupted ectopic canine

A

Mobility of the deciduous canine

palpable palatal elevation of the alveolar mucosa

Discolouration of the deciduous canine

Inclination/Angulation of the upper lateral incisor

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2
Q

What would early loss of a primary tooth cause

A

Crowding and dental centreline shift

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3
Q

what are the recognised effects of a digit-sucking habit on the developing dentition

A

Retroclination of the lower incisors

Proclination of the upper incisors

Anterior open bite

Unilateral posterior cross-bite

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4
Q

What supernumerary teeth are the most likely to erupt into the oral cavity

A

Supplemental and conical

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5
Q

what are the main factors that influence any decisions that need to be made regarding whether or not to balance or compensate the extraction of a grossly carious 6

A

Age of patient, degree of crowding, malocclusion type

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6
Q

lass II skeletal jaw relationship is most commonly associated with what

A

A retrognathic mandible

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7
Q

What is is most commonly associated with a Class III jaw relationship

A

Anteroposterior maxillary deficiency

Not as common but also Mandibular prognathism

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8
Q

What would be the signs of long face syndome

A

Backward growth rotation of the mandible.

Increased maxillary posterior dentoalveolar height.

An increased lower anterior face height percentage.

Ante-gonial notching of the mandible

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9
Q

What is the likely cause of a left-sided unilateral posterior crossbite that is not associated with a lateral displacement of the mandible on closure

A

A true asymmetry of the mandible with the chin point shifted to the left

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10
Q

What is the correct term used to describe a mismatch between the size of a patient’s teeth and jaws

A

Dento-alveolar disproportion

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11
Q

What are the geneeral aetiological factors of malocclusion

A

Skeletal: Size, shape and relative positions of the upper and lower jaws

Muscular: Form and function of the muscles that surround the teeth i.e. lips, cheeks and tongue

Dentoalveolar: Size of the teeth in relation to the size of the jaws

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12
Q

What are the components of the facial skeleton

A

Maxillary base

Mandibular base

Maxillary and mandibular alveolar processes

The maxillary complex is attached to the anterior cranial base while the mandible articulates with the posterior cranial base

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13
Q

What creates malocclusion

A

disharmony
between the components of the facial
skeleton

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14
Q

What is the aetiology of skeletal variation

A

Genetic and environmental factors

Possible environmental factors (Masticatory muscles, Mouth breathing, Head posture)

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15
Q

What are the 3 skeletal variations

A
  • Antero-posterior
  • Vertical
  • Transverse
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16
Q

What are the Cephalometrics of class 1

A

SNA (relates maxilla to anterior cranial base)
- ave value 81 +/-3

SNB (relates mandible to anterior cranial base)
- ave value 78 +/-3

ANB(relates mandible to maxilla)
- ave value 3 +/-2

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17
Q

What is a class 2 skeletal base

A

Mandible placed posteriorly relative to maxilla.

Mandible too small (most commonly), maxilla too
large, or combination of both

Mandible normally sized but placed too far back
due to obtuse cranial base angle

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18
Q

What are the cephalometrics of class 2

A

SNA usually average but may be increased if maxilla prognathic

SNB usually decreased

ANB >5

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19
Q

What is skeletal class 3

A

Mandible placed anteriorly relative to maxilla

Maxilla too small (most commonly), mandible too large, or combination of both

Normally sized jaws but mandible positioned too far forwards due to acute cranial base angle

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20
Q

what are the cephalometrics of class 3

A

Expect SNA to be decreased if maxilla deficient.

SNB often average but may be increased if mandible prognathic.

ANB < 1° or negative

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21
Q

what may disguise underlying skeletal discrepancy

A

Dento-alveolar structures

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22
Q

When talking about the vertical jaw relationship what do you need to look at

A

Frankfurt plane
– Lower orbital rim to superior border of external auditory meatus.

Mandibular plane
– Lower border of mandible.

Planes normally meet at the external occipital protuberance

Upper anterior face height
– Brow ridge (glabella) to base of nose

Lower anterior face height
– Base of nose (sub nasale) to inferior aspect of
chin

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23
Q

What is the average ration of lower anterior face height to upper anterior face height

A

50%/50%

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24
Q

What does the frankfort plane and mandibular plane create

A

The frankfort mandibular plane angle (FMPA)

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25
Q

Frankfort plane is created by joining what together

A

orbitale to porion

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26
Q

Mandibular plane is created by joining what together

A

Menton to Gonion

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27
Q

What is the average value of the FMPA

A

27° +/- 4°

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28
Q

For a long facial type what are the values associated with its vertical jaw relationship

A

LAFH to UAFH >55%
(more LAFH)

FMPA > 31°

Steeply inclined mandibular plane

Backward mandibular growth rotation

Anterior open bite tendency

29
Q

For a short facial type whatare the values associated with ts vertical jaw relationship

A

LAFH to UAFH <55%

FMPA < 23°

Tendency to parallelism of jaws

Forward mandibular growth rotation

Deep overbite tendency

30
Q

What are arch width discrepancies and what do they cause

A

Disproportion of maxillary and mandibular dental arches

Causes unilateral or bilateral buccal segment cross-bites

Often exaggerated by antero-posterior
discrepancies

31
Q

What happens in mandibular displacement and what would it cause

A

Occurs where inter-arch width discrepancy
causes upper and lower posterior teeth to
meet cusp to cusp.

Mandible forced to deviate to one side to achieve position of inter-cuspation

Possible association with Temperomandibular joint disorders

32
Q

What causes facial asymmetries

A

Displacement of normal mandible due to unilateral cross-bite

33
Q

What causes true mandibular asymmetry

A

Hemi-mandibular hyperplasia/elongation

Condylar hyperlasia

34
Q

What causes Dento-alveolar disproportion

A

Discrepancy between size of teeth and jaws

35
Q

What causes crowding and spacing

A

Crowding caused by:
– Small jaws, normally sized teeth
– Large teeth (macrodontia)

Spacing caused by:
– Large jaws, normally sized teeth
– Small teeth (microdontia)

36
Q

What is the prevalence of malocclusion

A

68%

37
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 teethproducing a malocclusion

38
Q

What are the 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

39
Q

What could the cause of varation in tooth number be

A
  1. Supernumerary teeth (extra)
  2. Hypodontia (developmentally absent teeth)
  3. Retained primary teeth
  4. Early loss of primary teeth
  5. Unscheduled loss of permanent teeth
40
Q

What is a supernumerary tooth and what are the stats of them

A

a tooth or tooth-like entity
which is additional to the normal series

most commonly in anterior maxilla

males > females

prevalence:
-1% in primary dentition
-2% in permanent dentition

41
Q

What are the 4 types of supernumeray teeth

A
  1. Conical
  2. Tuberculate
  3. Supplemental
  4. Odontome
42
Q

What is a conical supernumerary tooth

A

Small, peg shaped

Close to midline (mesiodens)

May erupt (extract)

Usually 1 or 2 in number

Tend not to prevent eruption but may displace adjacent teeth

43
Q

What does mesiodens mean

A

A supernumerary tooth present between the central incisors

44
Q

What is a tuberculate supernumerary tooth

A

tend not to erupt

paired

barrel-shaped

usually extracted

one of the main causes of failure of eruption of permanent upper incisors

45
Q

What is a supplemental supernmerary tooth

A

extra teeth of normal morphology

Most often upper laterals or lower incisors

Can be third premolars, fourth molars

Often extract – decision based on form & position

46
Q

what is a odontome supernumerary tooth

A

Compound
-discreet denticles

Complex
-disorganised mass of dentine, pulp and enamel

47
Q

What is hypodontia and wha are the stats of it

A

developmental absence of one or more teeth

Females > males 3:2

4-6% population (excluding8’s)

Commonly upper laterals (2s) > second premolars (5s)

48
Q

When would retention of primary teeth be alarming

A

A difference of
more than 6 months between the shedding of contra-lateral teeth

49
Q

Why would a primary tooth be retained

A
  1. Absent successor
  2. Ectopic successor or dilacerated
  3. Infra-occluded (ankylosed) primary molars
  4. Dentally delayed in terms of development
  5. Pathology / supernumerary
50
Q

If a patient has retained prim. teeth due to an absent successsor how would you treat it

A

Either maintain primary
tooth as long as possible
(if good prognosis)

Or, extract deciduous
tooth early to encourage
spontaneous space
closure in crowded cases

51
Q

Wha causes early loss of primary teeth

A
  1. Trauma
  2. Periapical pathology
  3. Caries
  4. Resorption by successor
52
Q

What affects the localisation of crowding in early loss of a primary tooth

A

which tooth is extracted

when the tooth is
extracted

patient’s inherent
crowding

53
Q

What is meant by balancing extraction

A

extraction of a tooth from the opposite side of the same arch

Designed to minimise midline shif

54
Q

What is meant by compensating exctraction

A

extraction of a tooth from the opposing arch of the same side

Designed to maintain occlusal relationship

55
Q

What type of extraction would you do with each tooth in early loss of prim. teeth

A

incisors
-very little impact
-no compensating or balancing ext

canines
-Unilateral loss in crowded arch can give centre-line shift
-Will get some mesial drift of buccal segments
-Consider balancing extraction

Molars
-More space loss with E’s > D’s
-More space loss in upper > lower
-6’s drift mesially and steal 5 space

56
Q

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

A
  1. Age at loss

upper arch less important
If L7s erupted (late)
-Often poor space closure
If too early
-Distal drift of 5’s, particularly if E’s lost at same time as 6’s

  1. Crowding

Uppers have potetntial for rapid space loss

  1. Malocclusion
57
Q

What are the variations in tooth and form

A
  1. Too large - macrodontia
  2. Too small - microdontia
  3. Abnormal form
58
Q

Talk about Macro/microdontia

A

Macrodontia
-tooth/teeth larger than average
localised or generalised
problems=crowding,asymmetry,aesthetics

Microdontia
-tooth/teeth smaller than average
-localised or generalised
-leads to spacing
-linked to hypodontia

59
Q

What abnormal forms of teeth can you get

A
  1. Peg shaped laterals
  2. dens in dente
  3. geminated/fused teeth
  4. talon cusps
  5. dilaceration
  6. accessory cusps and ridges
60
Q

What are ectopic teeth

A

Teeth not in the dental arch

61
Q

What teeth are more commonly ectopic

A

third molars (8s)
upper canines (3s)
first permanent molars (6s)
upper centrals (1s)

62
Q

Talk about ectopic canines

A

80% palatally and often in well aligned arches

Higher incidence with:
-Absent/peg shaped U laterals
-Class II, div 2 incisor relationship

Buccal canines more associated with crowding

63
Q

What radiographs would you need to take to radiographically assess ectopic canines

Whattechnique would you use

A

usually OPT & upper anterior oblique occlusal

Parallax technique
-3 Ps= presence, position, pathology

64
Q

What management options of an ectopic canine are there

A
  1. Prevention
  2. Extraction c to encourage improvement in position of 3
    (interceptive)
  3. Retain 3 and observe ( accept its position)
  4. Surgical exposure and orthodontic alignment
  5. (Surgical) Extraction
  6. Autotransplantion
65
Q

What are the possible causes of ectopic central incisors

A

No obvious cause

Supernumerary
-Tuberculate
-Odontome

Trauma to primary predecessor
-Ankylosis of primary tooth
-Displacement of tooth germ
-Dilaceration of root

66
Q

What does transposition of teeth mean and what are the classifications

A

Interchange in the position of two teeth

True/Pseudo

67
Q

What teeth are more commonly transpositioned and what are the treatment options

A

upper canines & first premolar
lower canines & incisors

Treatment options:
1) accept
2) extract
3) (correct)

68
Q

What can cause local abnormalities of soft tissues

A
  1. Digit sucking
  2. Fraenum
  3. Tongue thrust
69
Q

What could a labial Fraenum cause

A

Median diastema

Ortho (7 decks)

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