Malocclusion

Question 1

components of facial skeleton

Answer 1

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

Question 2

why a lateral ceph

Answer 2

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

Question 3

class I ceph angles

Answer 3

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

Question 4

AP class II relationship

Answer 4

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

Question 5

AP class II ceph angles

Answer 5

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

Question 6

AP class III

Answer 6

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

Question 7

AP class III ceph angles

Answer 7

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

Question 8

definition of local cause of malocclusion

Answer 8

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

Question 9

local causes of malocclusion (5)

Answer 9

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

Question 10

causes of variation in tooth number (5)

Answer 10

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

Question 11

supernumerary teeth

Answer 11

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

Question 12

4 types of supernumerary teeth

Answer 12

1. conical
2. tuberculate
3. supplemental
4. odontome

Question 13

conical supernumeraries

Answer 13

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

Question 14

tuberculate supernumeraries

Answer 14

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

Question 15

supplemental supernumeraries

Answer 15

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

Question 16

odontome supernumeraries

Answer 16

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

Question 17

hypodontia

Answer 17

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

Question 18

retained primary teeth

Answer 18

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

Question 19

reasons for retained primary teeth

Answer 19

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

Question 20

what to do if absent successor

Answer 20

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

Question 21

infra occluded molars

Answer 21

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

temporary ankylosis
common 1-9%
percussion sound

Question 22

causes of early loss of primary teeth

Answer 22

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

Question 23

balancing extraction

Answer 23

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

Question 24

compensating extraction

Answer 24

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

Question 25

early loss of incisors

Answer 25

very little impact no compensating or balancing

Question 26

early loss of canines

Answer 26

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

Question 27

early loss of molars

Answer 27

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

Question 28

unscheduled loss of 6s

Answer 28

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

Question 29

factors that influence the impact of the loss of 6s

Answer 29

age at loss crowding malocclusion

Question 30

age at loss of 6s

Answer 30

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

Question 31

if crowding

Answer 31

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

Question 32

unscheduled loss of central incisor

Answer 32

- 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

Question 33

variation in tooth size or form

Answer 33

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

Question 34

macrodontia

Answer 34

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

Question 35

microdontia

Answer 35

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

Question 36

abnormal form of teeth

Answer 36

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

Question 37

ectopic teeth

Answer 37

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

Question 38

ectopic maxillary canines

Answer 38

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

Question 39

ectopic canines

Answer 39

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

Question 40

clinical assessment of ectopic canines

Answer 40

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

Question 41

radiographic assessment of ectopic canines

Answer 41

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

Question 42

management of ectopic canines

Answer 42

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

Question 43

ectopic first molars

Answer 43

<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

Question 44

ectopic upper central incisors

Answer 44

no obvious causes but perhaps supernumerary or trauma to primary predecessor

Question 45

transpositions

Answer 45

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

Question 46

local abnormalities of soft tissues

Answer 46

1. digit sucking 2. fraenum 3. tongue thrust

Question 47

impact of digit sucking (4)

Answer 47

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

Question 48

local pathology causing malocclusion (3)

Answer 48

1. caries 2. cysts 3. tumours

Question 49

tongue thrust

Answer 49

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