Orthdontic Mechanics

Question 1

What are action of removable appliance?

Answer 1

• Tip teeth
• Enable differential tooth eruption
• Space maintenance

Question 2

What are use of Removable appliance ?

Answer 2

• Reducing overbite
• Arch expansion
• Space maintainer
• Distalising buccal segment with HG
• Habit breaker

Question 3

Functional Applinace

What are 5 method that functional appl alter occlusion?

Answer 3

• Proclination of lower incisors
• Retroclination / palatal tipping of upper incisor
• Distal movement of upper molars
• Mesial movement of lower molars
• Skeletal effect -1mm mandible growth , restrict maxillary 1mm growth but cannot accelerate mandibular growth

Question 4

5 ideal properties of bracket system.

Answer 4

1- Secure and robust
2- Full archwire engagement
3- Low friction / high friction
4- Easy to attach auxiliaries
5- assist OH
6- Comfortble
7- Bio compatible

Question 5

What are Potential failing with fixed appliances treatment ?

Answer 5

• Inaccurate bracket placement
• Variation in tooth structure
• Variation in skeletal pattern
• Slop / wire is not fully ligate
• Force diminution - less with NiTi

Question 6

What is bracket prescription? Or
Factors that make brackets different for each tooth?

Answer 6

• 1st order - In and out
• 2nd order - Tip
• 3rd order - torque

Question 7

What is function of bracket?

Answer 7

• Enable 3D controlled tooth movement

Question 8

Tooth movement which can achieve by Fixed appliances?

Answer 8

• Intrusion
• Extrusion
• Rotation
  -Tipping
• Bodily movement

Question 9

What is difference between tipping and bodily movement?

Answer 9

• Tipping - Movement around centre of rotation
• Bodily movement - movement of tooth

Question 10

What is difference between tip and torque?

Answer 10

• Tipping - movement around centre of rotation
• Torque- Change of centre of rotation

Question 11

Bracket history ?

Answer 11

• 1910 - Pin and tube
• 1916 - Ribbon arch
• 1925 - Edgewise bracket
• Straight wire system

Question 12

Slot size of preadjust bracket system?

Answer 12

• 0.022 - 0.028

Question 13

Factors effect fixed appliance result?

Answer 13

• Error in bracket position ( too much composite on one side)
• Error in bracket position
• Play within system - built in accuracy ( 9-10degree with 19*25 aw in 22x28 bracket slot)

Question 14

Properties of self lighting system?

Answer 14

• Secure and robust
• Full archwire engagement
• Low friction
• quick and easy to use
• Comfortable
• Less chair side require
• special tool require
• Costly

Question 15

Types of self lighting system?

Answer 15

• Active Clip - Speed and INovation
• Passive Clip - Damon and twin lock

Question 16

Advantages and disadvantages of Stainless steel appliance system?

Answer 16

• Advantages - low friction , low cost, easy to remove , easy to keep clean
• Disadvantage - Aesthetic , Psychological, allergies

Question 17

Disadvantage of ceramic brackets ?

Answer 17

• Tooth wear- Quarts harder than enamel
• High friction - metal insert
• Bonding and debonding - Bond strength can be greater than enamel shear strength

Question 18

Importance of friction

Answer 18

• To Prevent undesired tooth movement and to optimize tooth movement , friction must be understood and controlled .

less friction - more tooth to move
More friction- don’t want to move

If you get this wrong you will loose Anchorage

Question 19

Define friction ?

Answer 19

• Friction is the force resisting relative motion

Question 20

Orthodontics and friction

Answer 20

• Friction occurs at each point AW touch bracket
• Friction force is greater than orthodontic force binding occur and no tooth movement is observed results Anchorage loss

Question 21

When friction occurs?

Answer 21

• During alignment
• Sliding mechanism

Question 22

Friction is influenced by ?

Answer 22

• Archwire factor
• Bracket factor
• Ligation factor

Question 23

Friction - managing influencing factors?

Answer 23

• Wire / bracket clearance
• Archwire stifness
• Round vs rectangular wires
• Method of ligation
• Bracket / wire surface condition
• Bracket / wire martial
• Slot width.

Question 24

Mosquitoes and mathieu’s

Answer 24

• Mathieus stronger and less likely to distort

Question 25

Weingart plier

Answer 25

• Excellent for placing and removing archwire
• Hold wire close to its end
• Apply for locally to the tube

Question 26

How much forces do you need ?

Answer 26

Tipping- 35-60
Bodily movement - 50-120
Intrusion- 10-20
Extrusion- 35-60
Rotation- 50-100
torque - 50-100

Question 27

Bracket rotate from wire during sliding mechanism. This must be prevented

Answer 27

• Self ligating brackets - less friction -
• Orings
• Figure of 8
• SS ligature

Question 28

Adv and dis advantages of Elastomeric

Answer 28

-quick to place
- child friendly aesthetic
- lost between appointment
- Variable friction
- Release flouride
- Difficult to clean
- Cost
- Range of activation
- Force degradation

Question 29

Quick lig ss adv and dis adv?

Answer 29

• Take time to place
• Less friction
• adult friendly
• can’t be loss between appt
• Range of activation
• Control of force level
• Cost

Question 30

Which one does quick space closure?
O- Ligs
Powerchain
Niti coil spring ?

Answer 30

• Niti coil spring 0.81mm/ month
• Powerchain - 0.58mm/ month
• O- lig 0.35mm /month

Question 31

Evidence of loss of periodontal support?

Answer 31

• Recession
• Drifting
• over eruption
• Rotations
• Increased OJ

Question 32

Orthodontics and Periodontal disease.

Answer 32

• Excellent OH
• Disease related
• mechanism must take into account for reduced tooth support and changes to centre of rotation
• Light force , wires and auxiliary
• Longer period between appointment
• Regular gdp / periodontist review