Orthodontic Anchorage

Question 0

What does anchorgae indicate intraorally?

Answer 0

A

Question 1

What is anchorage amd how can it be delivered in the oral cavity?

Answer 1

….

By other teeth,

Question 2

How can anchorage be altered?

Answer 2

Tooth attachment pemitting certain types of movement
Bending archwires allowing certain types of movement
Incorporating more teeth ass anchorage units

Question 3

What are the different types if anchorage?

Answer 3

Intraoral
- intermaxillary
- intramaxillary (groups of teeth)
- implant (immovable object)
Extraoral
- mostly headgear (cervical/occipital/cranial) - description based on dirction of pull

Question 4

What are the types of tooth anchorage?

Answer 4

Simple (tipping) - little apical movement. Depends on rubber band force. If excessively strong, can end up moving molar instead of canine.
Compound - increases root surface area of anchoring teeth
Stationary - bodily movement
Reciprocal - root surface area approx the same and hence should assume similar movement of each tooth

Question 5

What are e general pronciples when considering anchorage during treatemnt planning?

Answer 5

Extraoral potential greater than intraoral (using a nondental structure outside mouth provides greater anchorage)
Bodily movement more potential than tipping movement
Heavy forces MAY produce more anchorage than light forces (biological systems are not entirely mechanical. Heavy force in tooth pushes it across pdl space up agaisnt alveolar bone squashing everything in between causing necrosis. No reaction occurs and hence no tooth movement)
Molars more than incisors
Ankylose teeth have the greatest anchorage potential

Question 6

What can be done to set up anchorage (e.g. Space maintainence)?

Answer 6

Dglaying extractions
Space maintainence
Tweed system (fixed appliance)

Question 7

What does the Tweed system do?

Answer 7

Fixed appliance that retracts lower incisors and protracts upper arch. (Start by incrsing overjet). Headgear applied to support upper arch during this. The upper teeth presumably do not move.
Bends in archwire to facilitate distal tipping of lower posteriors
Class III elastics discontinued with headgear and then class II elastics applied to push lower arch foward.

Question 8

What are the types of headgear availible?

Answer 8

Cervical
Straight pull - pull along line of occlusal plane
High pull - pull above occlusal plane
Reverse pull - to manage class III with mandibular excess or class III with maxillary deficiency

Question 9

What are the main components of headgear?

Answer 9

Outer bow
Inner bow - attaches to bands on upper molars
Elasticised head strap

Magnitude of force
Less than 500gs for tooth movement (however 30gs is enough to move teeth. Anything above capillary pressure is sufficient)
1-2 kgs for orthopaedic force

Question 10

What are the main uses of headgear?

Answer 10

Tooth movement
- management of class II by distalising upper molars (regaining space)
- advance lower molars
Reinforce anchorage - tweed system
Restrain or redirect growth of midface
Orthopaedic changes to mx and md

Question 11

What can make headgear application more difficult?

Answer 11

Tilted and rotatee upper molars. Heargear cant rotate teeth hence other mechanics need to be considered.

Question 12

What is the difference between the centre pf rotation and centre of resistance?

Answer 12

Centre if resistance is where the most mass is.

Centre of rotation can vary depending on where the forces are applied.

Question 13

What happends if the pull of headgear is not delivered through the centre of rotation?

Answer 13

Cervical pull headgear
- occlusal - generate distalisation and extrusion but also cause tipping in an anticlockwise direction
- apical - distalisation, extrusion and clockwise rotation
High pull headgear
- occlusal to centre if rotation - clockwise rotation
- apical - anticlockwise rotation

All this is fine as long as it is what you actually want to achieve

Question 14

How cant he direction if force be altered with headgear?

Answer 14

Force by band
Length of outer bow
The angle of outer bow to inner bow can create a different vector system changing the direction and mode of force

Question 15

What are the complications of headgear?

Answer 15

Worsening of malocclusion (e.g. Extrusion of molars in open bite cases - these need high pull headgear, not cervical)
Root resorption - langford and sims 1981
(Need to time headgear so that sevens are almost through)
Impactions of second and third molars (from distalising 6s)
Crossbites - if inadequate inner bow expansion to compensate molar distalisation
Patient cooperation - 24 hours for orthopaedic effect, 12 hrs a day for tooth movement

Question 16

What should be watched out for when plaing a mini screw?

Answer 16

Domt put it into roots of teeth.
Make sure its not somewhere where future tooth movement is anticipated.
Should be in keratinised tissue roughly about 8-11mm from the crest if the bone.

Question 17

Why cant thick wires be use for lingual mechanics in orthodontics?

Answer 17

Very small interbracket distance between lower anteriors.

Question 18

Why do some practitioners not use LA when placing mini screws?

Answer 18

Bone doesnt have a nerve supply hence doesnt hurt. Only topical required. If pain felt when placing mini screws youre probably not in the right place (tooth root, pdl… Etc..)