Removable appliances

Question 1

Difference in action between ortho appliances

Answer 1

RA: tip teeth around fulcrum (1/2 along tooth)

Fixed appliance: capable of more complex tooth movements
- bodily movement
- rotation
- intrusion
- root control

Question 2

Active components of RA

Answer 2

Springs - 18:8 stainless steel
Screws - midline expansion screws
Labial bows - Robert’s retractors

Question 3

Principles of cantilever spring

Answer 3

inc wire thickness inc force/deflection by a factor of 4
inc length of arm reduces force/deflection by a factor of 3

Question 4

Retentive components

Answer 4

Adams clasps - molars/premolars
Southend and half jackson: incisors

Question 5

Baseplate of RA

Answer 5

Anterior biteplane: reduce deep overbite
Posterior biteplane: produce vertical opening between the anterior teeth to allow proclination of lingually placed upper incisors

Question 6

Types of RA

Answer 6

Ant/Post biteplanes
URA with midline expansion screw
Palatal springs to procline upper incisors
Palatal finger spring to retract canine/premolars
Roberts retractor to retract proclined incisors
Buccal canine retractor

Question 7

Midline expansion appliance

Answer 7

Correction of crossbite
1 turn of screw expands by 1mm

Question 8

Palatal spring retractor

Answer 8

retracting canines/premolars
1/2 width of canine or premolar

Question 9

Roberts retractor

Answer 9

retracting incisors