Fixed Appliances Flashcards
Andrew’s 6 key?
- Molar relationship
- correct crown angulation
- correct crown inclination
- curve of spee (flat occlusal plane)
- no rotation
- no spaces
7- size and shape of tooth.
How are these 6 key of occlusion achieved?
Precise tooth positioning in 3 dimensions
How each tooth has its own Individual position within arch. How can you spot difference?
- How labially teeth are placed
- thickness of tooth (labio / lingual)
- angulation of teeth (upright or tipped)
- inclination of teeth (retroclined/ Proclined )
Standard edgewise fixed appliances
- 1 type of bracket for all teeth.
- Archwire was customised (bent) by orthodontist to incorporate the 3 orders of movement in each tooth.
Preadjusted edgewise fixed appliances (SWA)
- individual bracket per tooth with specific 3 orders of movement build in. Called Prescription of bracket.
- 1 archwire , not customised , appliance called STRAIGHT WIRE APPLIANCE
3 orders of movements
1st order - in/out
2nd order- crown tip
3rd order- crown torque
MBT bracket 2nd order movement -Tipping
Upper - 1 2 3 4 5 6 7
4 8 8 0 0 5 5
Lower- 0 0 3 2 2 2 2
MBT bracket prescription: 3 order movement t
Torque / inclination.
Upper - 1 2 3 4 5 6 7
17,10, -7,-7,-7,-14,-14
Lower- -6,-6,-6,-12,-17,-20,-10
How are the 3 orders of movement built into the bracket?
Archwires
Describe a bracket and slot size ?
MBT ( preadjusted fixed appliance bracket)
1- four tie wings
2- Archwire slot 0.022x0.028 most common in uk
3- Archwire slot 0.018x0.025
4- base
5- identification marking
6- curved base helps bracket location, seating and stress distribution
How do you know where to place a bracket to get the best end result?
- you need a reference point/ position
Correct bracket positioning on the tooth surface?
Central slot of bracket must be correctly positioned with respect to:
1- Incisal edge /cusp tip
2- mesio- distal position
3- long axis
What is LACC and LA point?
- LACC - long axis of clinical crown
-LA- midpoint of crown on LACC
What safety issues do we need to consider when bonding?
- Etch should not touch soft tissue as it’s phosphoric acid
- Inhalation and ingestion of bracket or wire piece.
Lower incisor brackets placement
-similar height and correct
What can you us to remove flesh of composite?
Hockey stick
Probe
Mitchell trimmer
What position of bracket should be for palatally placed upper lateral incisors ?
Inverted bracket
So labial root torque is introduced rather than palatal root torque.
Swapping lower canines (class 3cases) ? Why
Reverse tip NOT torque
Which guage you can use to decide elastic size?
Orthodontic force guage
Moving canine into lateral incisor position? How? Hypodontia case
- inverting upper canine
- bonding premolar slightly more distal to bring buccal eminence so premolar can have canine like appearance
Bracket materials?
Metal - stainless steel, cobalt chronium, titanium, gold
Ceramic- mono crystalline aluminium oxide ( clear ) polycrystalline aluminium oxide (opaque)
Plastic - polycarbonate, thermoplastic polyurethane.
Metal bracket
-Most commonly used
- composition varied (AISI- American iron & steel institute)
Metal bracket method of manufacture?
1- Milled (e.g Dynalock)
2- Cast (e.g. A co . St)
3- injection moulded .
Method of retention for bracket
- Primarily mechanical
- methods use to increase surface area for bonding e.g mesh, laser etched, sandblasted , silicon coated
- curved base helps bracket location, seating, and distribute stress point
