Orthdontic Mechanics Flashcards
What are action of removable appliance?
- Tip teeth
- Enable differential tooth eruption
- Space maintenance
What are use of Removable appliance ?
- Reducing overbite
- Arch expansion
- Space maintainer
- Distalising buccal segment with HG
- Habit breaker
Functional Applinace
What are 5 method that functional appl alter occlusion?
- 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
5 ideal properties of bracket system.
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
What are Potential failing with fixed appliances treatment ?
- Inaccurate bracket placement
- Variation in tooth structure
- Variation in skeletal pattern
- Slop / wire is not fully ligate
- Force diminution - less with NiTi
What is bracket prescription? Or
Factors that make brackets different for each tooth?
- 1st order - In and out
- 2nd order - Tip
- 3rd order - torque
What is function of bracket?
- Enable 3D controlled tooth movement
Tooth movement which can achieve by Fixed appliances?
- Intrusion
- Extrusion
- Rotation
-Tipping - Bodily movement
What is difference between tipping and bodily movement?
- Tipping - Movement around centre of rotation
- Bodily movement - movement of tooth
What is difference between tip and torque?
- Tipping - movement around centre of rotation
- Torque- Change of centre of rotation
Bracket history ?
- 1910 - Pin and tube
- 1916 - Ribbon arch
- 1925 - Edgewise bracket
- Straight wire system
Slot size of preadjust bracket system?
- 0.022 - 0.028
Factors effect fixed appliance result?
- 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)
Properties of self lighting system?
- Secure and robust
- Full archwire engagement
- Low friction
- quick and easy to use
- Comfortable
- Less chair side require
- special tool require
- Costly
Types of self lighting system?
- Active Clip - Speed and INovation
- Passive Clip - Damon and twin lock
Advantages and disadvantages of Stainless steel appliance system?
- Advantages - low friction , low cost, easy to remove , easy to keep clean
- Disadvantage - Aesthetic , Psychological, allergies
Disadvantage of ceramic brackets ?
- Tooth wear- Quarts harder than enamel
- High friction - metal insert
- Bonding and debonding - Bond strength can be greater than enamel shear strength
Importance of friction
- 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
Define friction ?
- Friction is the force resisting relative motion
Orthodontics and friction
- 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
When friction occurs?
- During alignment
- Sliding mechanism
Friction is influenced by ?
- Archwire factor
- Bracket factor
- Ligation factor
Friction - managing influencing factors?
- Wire / bracket clearance
- Archwire stifness
- Round vs rectangular wires
- Method of ligation
- Bracket / wire surface condition
- Bracket / wire martial
- Slot width.
Mosquitoes and mathieu’s
- Mathieus stronger and less likely to distort
Weingart plier
- Excellent for placing and removing archwire
- Hold wire close to its end
- Apply for locally to the tube
How much forces do you need ?
Tipping- 35-60
Bodily movement - 50-120
Intrusion- 10-20
Extrusion- 35-60
Rotation- 50-100
torque - 50-100
Bracket rotate from wire during sliding mechanism. This must be prevented
- Self ligating brackets - less friction -
- Orings
- Figure of 8
- SS ligature
Adv and dis advantages of Elastomeric
-quick to place
- child friendly aesthetic
- lost between appointment
- Variable friction
- Release flouride
- Difficult to clean
- Cost
- Range of activation
- Force degradation
Quick lig ss adv and dis adv?
- Take time to place
- Less friction
- adult friendly
- can’t be loss between appt
- Range of activation
- Control of force level
- Cost
Which one does quick space closure?
O- Ligs
Powerchain
Niti coil spring ?
- Niti coil spring 0.81mm/ month
- Powerchain - 0.58mm/ month
- O- lig 0.35mm /month
Evidence of loss of periodontal support?
- Recession
- Drifting
- over eruption
- Rotations
- Increased OJ
Orthodontics and Periodontal disease.
- 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
