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
Desirable features of metal brackets?
- good bond
- low friction
- non toxic
- corrosion resistance
- poor biohost i.g plaque resistance
- cheap and easily available
- resist deformation by patient
- easy to debond
- radiopaque
- long shelf life
Ceramic brackets properties
- brittle
- high compressive strength
- low tensile strength
- hard
- resistance to stain
- chemically inert
Ceramic bracket pros / cons
Pros :
-asthetic ,
-abrasion resistance,
-chemically inert
-poor biohost,
-good biocompatibility
-useful for nickel allergy patient.
Cons :
Expensive
Abrasive to tooth
Friction with archwire
Brittle
Difficult Debond. Carful with RCT / heavily filled tooth
Plastic Brackets ?
- Good for asthetic
- wear off easily
- staining
- 0 torque transfer
Self ligating brackets how many kinds?
- Active : In- ovation R and speed
- passive - Damon and smart clip
Self ligating bracket Adv/ dis advantage
Advantages:
-Full archwire engagement
- less chair side assistance requires
- less chair time required
- reduced number of appointments
- improved infection control.
Disadvantages:
- takes practice
- clips fracture or opening between appt
- No partial ligation
- wire sliding round
- cost
- no evidence of faster alignmentment or space closure
Cleats
- Cross elastics
- place powerchain or power thread
Eyelets
- uses auxiliaries to pull palatal canine into alingment e.g powerchain or thread
- run archwire through
Buttons
- cross elastics to correct crossbite
- to add chain to derotate tooth
BITE TURBO
- reduce overbite
- made of steel or composite
Begg bracket
- to pull palatal canine
- run archwire through and use Begg pin to hold wire. Rarely use
Ideal properties of orthodontic adhesive
- easy to use
- single component
- No enamel pre tx required
- adhesive to wet
- adhesive to metal/ palctic/ ceramic
- sufficient bond strength to enamel and bracket
- cheap
- non toxic
- poor biohost
- sustained fluoride
- cohesive strength less than enamel
- long shelf life
- good aesthetics
- BOND SHOULD LAST 2 years
Explain Bonding process?
- Pumice with oil free brush
- isolate teeth ( cheek tetractor) and suction
- Dry suction and air dry
- place etch 37% o-phosporic acid 15-30 seconds
- rinse water spray
- Dry - oil free compressed air until frosty white appearance.
- infilled resin or primer
- place bracket
- remover excess adhesive
- light cure 440-480 nm for 10s / interspace
- remove lip retractor
How can you remove pellicle and plaque?
- cups vs bristle brush
- prophypate vs Pumice
Pumicing
Study shows it has no effect on bond failure
Why etch ?
To increase surface area for bonding by increasing surface area.
Etch concentration
30% - 50% o- phosphoric acid
Bond Application what does it do!?
- unfilled resin or primer
- protects etched enamel
COMMON CAUSE OF DERMATOSES IN DENTAL PERSONNEL
Example of light cure composite
- Transbond
- adhesive precoat
Potential failing with fixed appliances?
- Inaccurate bracket position.
- Slop
- variation in tooth structure.
- Variation in skeletal pattern. (D.A compensation).
- Force diminution- Less with NITI
What are the factors that make the brackets different for each tooth
3 order movements
- 1st order- In / out
- 2nd order- Tipping
-3rd order- Torque
