Interceptive Orthodontics

Question 1

name 5 potential causes of an unerupted maxillary central incisor

Answer 1

• supernumerary (most commonly tuberculate)
• trauma to deciduous tooth
• crowding
• downs syndrome
• CLP
• cleidocranial dystosis
• ectopic position of tooth germ

Question 2

where would the mesial cusp of the upper 6 be in a full unit class 2 (molar class)

Answer 2

in the embrasure of the lower 5 and 6

Question 3

what distance is the average overjet

Answer 3

2-3mm

Question 4

name 4 risks associated with leaving unerupted teeth in situ

Answer 4

• root resorption of adjacent teeth
• ankylosis to bone
• cyst formation
• resorption of unerupted tooth crown

Question 5

what landmarks give the best prognosis of success for spontaneous eruption of impacted canines once Cs are extracted

Answer 5

• unerupted canine has not passed midpoint of lateral

Question 6

name 5 potential treatment options for unerupted canines

Answer 6

• do nothing and monitor
• interceptive extraction of Cs
• Surgicaly removal of unerupted canines
• auto transplantation
• exposure and bonding of orthodontic attachment

Question 7

name 4 potential aetiologies for the high incidence of unerupted maxillary canines

Answer 7

• ectopic position of the tooth germ
• long path of eruption
• genetic predisposition (associated with dental anomalies in other family members)
• crowding (last tooth in upper arch to erupt)

Question 8

how do we assess intra orally if there is suspected unerupted canines

Answer 8

• palapate bucally and labially to feel for unerupted teeth
• assess mobility of Cs if still present
• assess mobility of lateral incisors incase of root resorption
• angulation of adjacent lateral incisors (tend to tip distally if root being pushed on palatal side)

Question 9

what 2 combinations of radiographs can be used to apply parallax

Answer 9

2 periapicals
OPT and maxillary occlusal

Question 10

give 2 justifications for taking a lateral cephalogram

Answer 10

• assess severity of underlying skeletal pattern (if relevant to treatment planning))
• extra view of unerupted tooth

Question 11

definition of interceptive orthodontics

Answer 11

any procedure which will eliminate or reduce the severity of a developing malocclusion

Question 12

if extracting deciduous teeth to ‘encourage permanent teeth to erupt’ what is the ideal stage of development of the successor

Answer 12

permanent tooth sees 1/2 to 2/3 root development

Question 13

how is space gained in the arch for incoming permanent teeth

Answer 13

• leeway space
• increase in intercanine width through lateral growth of jaws
• upper incisors erupt onto a wider arc (more proclined)

Question 14

discuss leeway space

Answer 14

difference between the width of the deciduous canine and molars and incoming permanent canine and premolars
- 1-1.5mm gained in upper arch
- 2-2.5mm gained in lower arch

Question 15

name 4 reasons for interception in the early mixed dentition

Answer 15

• impacted 6s
• unerupted central incisors
• early loss of deciduous teeth
• carious 6s

Question 16

treatment of impacted 6s in the early mixed dentition

Answer 16

• if patient under 7, wait 6 months and will hopefully resolve on its own
• placement of orthodontic separator between contact of 6 and E to create space
• extract E
• distal disking of E

Question 17

what is a consequence of early loss of deciduous teeth

Answer 17

localised crowding

Question 18

balancing extraction

Answer 18

aims to maintain position of dental centre lines
removal of tooth from opposite side of same arch

Question 19

compensating extraction

Answer 19

aims to prevent overeruption and maintain buccal occlusion
(always take upper)

Question 20

early loss of what teeth indicates need for balancing extraction

Answer 20

C or D

Question 21

what is the ideal time to extract carious 6s so that the space is closed by the 7

Answer 21

when the 7s bifurcation is beginning to calcify
(8s will also ideally be present and the arch will have moderate crowding)

Question 22

what amount of mandibular displacement due to cross bite indicates a need for orthodontic treatment

Answer 22

more than 2mm

Question 23

give 6 instructions for a patient you have just fitted a removable appliance

Answer 23

• wear full time even when eating
• remove when brushing (ideally brush every time after eating)
• avoid sugary foods and drinks
• avoid hard, sticky foods which may damage appliance
• speech will initially be affected
• excess saliva may initially be produced
• may want to remove for contact sports

Question 24

signs of an infra occluded (ankylosed) deciduous tooth)

Answer 24

dull percussion tone
no PDL space or lamina dura on radiographs

Question 25

risks of doing nothing for an infra occluded deciduous tooth

Answer 25

• permanent successor becomes ectopic
• infra occlusion worsens and adjacent teeth tip making tooth inaccessibe for extraction
• caries and perio due to OH difficulties

Question 26

treatment of infra occluded deciduous teeth with successor present

Answer 26

• monitor for 6-12 months
• extract if successor near complete root formation or more than 12 months

Question 27

treatment of infra occluded deciduous teeth with absent successor

Answer 27

• if deciduous good condition, retain and place onlay?
• extract if below adjacent contact points