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Ortho > Aetiology of Malocclusion > Flashcards

Aetiology of Malocclusion Flashcards

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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
Frankfort plane is created by joining what together
orbitale to porion
26
Mandibular plane is created by joining what together
Menton to Gonion
27
What is the average value of the FMPA
27° +/- 4°
28
For a long facial type what are the values associated with its vertical jaw relationship
LAFH to UAFH >55% (more LAFH) FMPA > 31° Steeply inclined mandibular plane Backward mandibular growth rotation Anterior open bite tendency
29
For a short facial type whatare the values associated with ts vertical jaw relationship
LAFH to UAFH <55% FMPA < 23° Tendency to parallelism of jaws Forward mandibular growth rotation Deep overbite tendency
30
What are arch width discrepancies and what do they cause
Disproportion of maxillary and mandibular dental arches Causes unilateral or bilateral buccal segment cross-bites Often exaggerated by antero-posterior discrepancies
31
What happens in mandibular displacement and what would it cause
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
What causes facial asymmetries
Displacement of normal mandible due to unilateral cross-bite
33
What causes true mandibular asymmetry
Hemi-mandibular hyperplasia/elongation Condylar hyperlasia
34
What causes Dento-alveolar disproportion
Discrepancy between size of teeth and jaws
35
What causes crowding and spacing
Crowding caused by: – Small jaws, normally sized teeth – Large teeth (macrodontia) Spacing caused by: – Large jaws, normally sized teeth – Small teeth (microdontia)
36
What is the prevalence of malocclusion
68%
37
What is the definition of Local Causes Of Malocclusion
a localised problem or abnormality within either arch, usually confined to one, two or several teethproducing a malocclusion
38
What are the local causes of malocclusion
Variation in tooth number Variation in tooth size or form Abnormalities of tooth position Local abnormalities of soft tissues Local pathology
39
What could the cause of varation in tooth number be
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
What is a supernumerary tooth and what are the stats of them
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
What are the 4 types of supernumeray teeth
1. Conical 2. Tuberculate 3. Supplemental 4. Odontome
42
What is a conical supernumerary tooth
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
What does mesiodens mean
A supernumerary tooth present between the central incisors
44
What is a tuberculate supernumerary tooth
tend not to erupt paired barrel-shaped usually extracted one of the main causes of failure of eruption of permanent upper incisors
45
What is a supplemental supernmerary tooth
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
what is a odontome supernumerary tooth
Compound -discreet denticles Complex -disorganised mass of dentine, pulp and enamel
47
What is hypodontia and wha are the stats of it
developmental absence of one or more teeth Females > males 3:2 4-6% population (excluding8’s) Commonly upper laterals (2s) > second premolars (5s)
48
When would retention of primary teeth be alarming
A difference of more than 6 months between the shedding of contra-lateral teeth
49
Why would a primary tooth be retained
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
If a patient has retained prim. teeth due to an absent successsor how would you treat it
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
Wha causes early loss of primary teeth
1. Trauma 2. Periapical pathology 3. Caries 4. Resorption by successor
52
What affects the localisation of crowding in early loss of a primary tooth
which tooth is extracted when the tooth is extracted patient’s inherent crowding
53
What is meant by balancing extraction
extraction of a tooth from the opposite side of the same arch Designed to minimise midline shif
54
What is meant by compensating exctraction
extraction of a tooth from the opposing arch of the same side Designed to maintain occlusal relationship
55
What type of extraction would you do with each tooth in early loss of prim. teeth
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
What factors influence the impact of the loss of 6's
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 2. Crowding Uppers have potetntial for rapid space loss 3. Malocclusion
57
What are the variations in tooth and form
1. Too large - macrodontia 2. Too small - microdontia 3. Abnormal form
58
Talk about Macro/microdontia
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
What abnormal forms of teeth can you get
1. Peg shaped laterals 2. dens in dente 3. geminated/fused teeth 4. talon cusps 5. dilaceration 6. accessory cusps and ridges
60
What are ectopic teeth
Teeth not in the dental arch
61
What teeth are more commonly ectopic
third molars (8s) upper canines (3s) first permanent molars (6s) upper centrals (1s)
62
Talk about ectopic canines
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
What radiographs would you need to take to radiographically assess ectopic canines Whattechnique would you use
usually OPT & upper anterior oblique occlusal Parallax technique -3 Ps= presence, position, pathology
64
What management options of an ectopic canine are there
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
What are the possible causes of ectopic central incisors
No obvious cause Supernumerary -Tuberculate -Odontome Trauma to primary predecessor -Ankylosis of primary tooth -Displacement of tooth germ -Dilaceration of root
66
What does transposition of teeth mean and what are the classifications
Interchange in the position of two teeth True/Pseudo
67
What teeth are more commonly transpositioned and what are the treatment options
upper canines & first premolar lower canines & incisors Treatment options: 1) accept 2) extract 3) (correct)
68
What can cause local abnormalities of soft tissues
1. Digit sucking 2. Fraenum 3. Tongue thrust
69
What could a labial Fraenum cause
Median diastema

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