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BDS3 Orthodontics > Malocclusion > Flashcards

Malocclusion Flashcards

1
Q

components of facial skeleton

A

maxillary base
mandibular base
maxillary & mandibular alveolar processes
maxillary complex is attached to anterior cranial base while the mandible articulates with the posterior cranial base

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2
Q

why a lateral ceph

A
  1. standardised
  2. reproducible - ptx positioned in a cephalostat, a set distance from the cone & film
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3
Q

class I ceph angles

A

SNA relates maxilla to anterior cranial base; av value is 81o +/- 3o
SNB relates mandible to anterior cranial base; av value is 78o +/- 3o
ANB relates mandible to maxilla; av value is 3o +/- 2o

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4
Q

AP class II relationship

A

mandible placed posteriorly relative to maxilla
mandible most commonly too small, maxilla too large or combination of both or mandible normal sized but placed too far back due to obtuse cranial base angle

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5
Q

AP class II ceph angles

A

SNA usually average but may be increased if maxilla prognathic
SNB usually decreased
ANB >5o

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6
Q

AP class III

A

mandible placed anteriorly relative to maxilla
maxilla too small most commonly, mandible too large or combination of both
normal sized jaws but mandible positioned too far forwards due to acute cranial base angle

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7
Q

AP class III ceph angles

A

expect SNA to be decreased if maxilla deficient
SNB often average but may be increased if mandible prognathic
ANB <1o or negative

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8
Q

definition of local cause of malocclusion

A

a localised problem or abnormality within either arch usually confined to 1, 2 or several teeth producing a malocclusion
tends to get worse with time
scope for interceptive tx
good to recognise early

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9
Q

local causes of malocclusion (5)

A
  1. variation in tooth number
  2. variation in tooth size or form
  3. abnormalities of tooth position
  4. local abnormalities of soft tissue
  5. local pathology
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10
Q

causes of variation in tooth number (5)

A
  1. supernumerary teeth
  2. hypodontia
  3. retained primary teeth
  4. early loss of primary teeth
  5. unscheduled loss of permanent teeth
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11
Q

supernumerary teeth

A

tooth or tooth like entity which is additional to the normal series
most common in anterior maxilla
M > F
1% primary dentition
2% permanent dentition

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12
Q

4 types of supernumerary teeth

A
  1. conical
  2. tuberculate
  3. supplemental
  4. odontome
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13
Q

conical supernumeraries

A

small, peg shaped
close to midline (mesiodens)
may erupt so xla
usually 1 or 2
tend not to prevent eruption but may displace adjacent teeth

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14
Q

tuberculate supernumeraries

A

tend not to erupt
paired
barrel shaped
usually xla
one of the main causes of failure of eruption of permanent upper incisors

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15
Q

supplemental supernumeraries

A

extra teeth of normal morphology
most often upper laterals or lower incisors
often xla; decision based on form & position

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16
Q

odontome supernumeraries

A

compound - discreet denticles
complex - disorganised mass of dentine, pulp & enamel

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17
Q

hypodontia

A

developmental absence of 1 or more teeth
F > M 3:2
4-6% population
commonly upper laterals / 2nd premolars

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18
Q

retained primary teeth

A

a disruption in sequence of eruption
a difference of >6 mths between shedding of contra lateral tooth = alarm bells, take radiograph to see what’s going on

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19
Q

reasons for retained primary teeth

A
  1. absent successor
  2. ectopic successor / dilacerated
  3. infra occluded (ankylosed) primary molars
  4. dentally delayed in terms of development
  5. pathology / supernumerary
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20
Q

what to do if absent successor

A
  1. maintain primary for as long as possible if good prognosis
  2. xla deciduous tooth early to encourage spontaneous space closure in crowded areas
    early ortho referral for advice
21
Q

infra occluded molars

A

process where a tooth fails to achieve or maintain its occlusal relationship with adjacent teeth

temporary ankylosis
common 1-9%
percussion sound

22
Q

causes of early loss of primary teeth

A
  1. trauma
  2. periapical pathology
  3. caries
  4. resorption by permanent successor
23
Q

balancing extraction

A

xla of tooth from opposite side of same arch
designed to minimise midline shift

24
Q

compensating extraction

A

xla of tooth from opposing arch of same side
designed to maintain occlusal relationship

25
Q

early loss of incisors

A

very little impact
no compensating or balancing

26
Q

early loss of canines

A

unilateral loss in crowded arch give centre line shift
will get some mesial drift of buccal segments
consider balancing xla

27
Q

early loss of molars

A

more space loss with Es > Ds
more space loss in upper > lower
6s drift mesially and steal 5s space
don’t tend to balance or compensate

28
Q

unscheduled loss of 6s

A

routine assessment of 6s at 8-9yrs
seldom ideal tooth of choice for relief of crowding
but planned loss at correct age is better than later enforced loss

29
Q

factors that influence the impact of the loss of 6s

A

age at loss
crowding
malocclusion

30
Q

age at loss of 6s

A

upper - not very important
lower -
if 7s erupted (late) often poor space closure
if too early there is distal drift of 5s particularly if Es lost at same time as 6s

31
Q

if crowding

A

upper - potential for rapid space loss
lower
spaced - will have spaces
aligned - will have spaces
crowded - best results likely

32
Q

unscheduled loss of central incisor

A
  • effect depends on timing of loss; early results in drift of adjacent teeth & late will result in long term space
  • ideally maintain space so re implant or simple denture
  • plan how to deal with space longer term i.e. definitive prosthesis
  • if lateral incisor drifts to fill space then re open space for prosthesis or build up lateral
33
Q

variation in tooth size or form

A
  1. macrodontia = too large
  2. microdontia = too small
  3. abnormal form
34
Q

macrodontia

A

larger teeth than average
localised / generalised
problems inc:
- crowding
- asymmetry
- aesthetics

35
Q

microdontia

A

smaller teeth than average
localised / generalised
leads to spacing
linked to hypodontia

36
Q

abnormal form of teeth

A

peg shaped laterals
dens in dente
geminated / fused teeth
talon cusps
dilaceration
accessory cusps & ridges

37
Q

ectopic teeth

A

most commonly
8s > upper 3s > FPM 6s > upper 1s

38
Q

ectopic maxillary canines

A

1-3% of population and 80% palatal
check for palpable buccal canine bulge from 9yrs onwards!! further investigation i.e. PAs or refer if in doubt

39
Q

ectopic canines

A

long path of eruption (eye teeth)
palatal canines often occur in well aligned arches
higher incidence: absent / peg shaped U laterals or class II div 2 incisor relationship
buccal canines more associated with crowding

40
Q

clinical assessment of ectopic canines

A
  1. visualisation / palpation of any obvious bumps of 3
  2. inclination of 2
  3. mobility of c or 2
  4. colour of c or 2
41
Q

radiographic assessment of ectopic canines

A

2 radiographs required to localise position usually OPT & upper anterior oblique occlusal
use parallax technique
3Ps = presence, position, pathology

42
Q

management of ectopic canines

A
  1. prevention
  2. xla of c to encourage improvement in position of 3
  3. retain 3 and observe (accept its position)
  4. surgical exposure & ortho alignment
  5. surgical xla
  6. autotransplantation
43
Q

ectopic first molars

A

<5%, commonly U arch, reversible before 8, caries risk
sign of:
crowding, mesial path of eruption, abnormal morphology of E
management:
separator, attempt to distalise 6, xla E

44
Q

ectopic upper central incisors

A

no obvious causes
but perhaps supernumerary or trauma to primary predecessor

45
Q

transpositions

A

interchange in position of 2 teeth
either true / pseudo
commonly:
upper canines & first premolar
lower canines & incisors
either accept, xla or correct

46
Q

local abnormalities of soft tissues

A
  1. digit sucking
  2. fraenum
  3. tongue thrust
47
Q

impact of digit sucking (4)

A
  1. proclined upper incisors
  2. retroclined lower incisors
  3. anterior over bite
  4. unilateral posterior crossbite
    - due to narrow maxillary arch
    - may cause mandibular displacement
48
Q

local pathology causing malocclusion (3)

A
  1. caries
  2. cysts
  3. tumours
49
Q

tongue thrust

A

can either be because of an AOB where tongue protrudes forwards to create anterior oral seal or can cause an AOB

BDS3 Orthodontics (3 decks)

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