Fixed appliances in Orthodontics I: Theory and Components Flashcards
Indications for FA
Correct overjet/overbite
Correct mild/mod skeletal discrepancy
Space closure
Rotation
Why can it induce greater range of movement?
They are attached but less effective at moving blocks of teeth
What are the brackets attached to and how do they work?
What do they allow for?
Bracket attached to surface allows for vertical and tilting movement. Force couple generated from interaction between bracket and archwire running through it (rotational and apical movements)
Types of tooth movement possible?
Tipping Bodily movement Rotation Torque Vertical movements
Removable appliances can only?
Tip
What determines type and direction of movement?
Interaction between bracket and wire determines type and direction of movement. Shape of bracket affects movement. Rectangular usually. Narrow bracket allow for greater archwire span therefore more flexibility. Wider reduces interbracket archwire span (reduced flexibility but more useful for derotation and MD control).
What does narrow bracket allow for? Wider bracket = ?
Greater archwire span so more flexibility
Reduced archwire span but more MD control
Greater control is gained by?
More similar fit of archwire in bracket
Round wire in rectangular slot?
MD tilt, vertical height and rotational position control
Round wire used for
only BL tipping and initial alignment
Rectangular - Rectangular slot
BL apical movements and premature tipping before slot is reached
Final alignment and space closure
Most common?
Fixed appliance with rectangular wires achieves movements in all 3 planes
First order wire bend
Made in plane of archwire
Second order
Vertical plane to achieve MD changes
Third order - work for? and do?
work for rectangular wires - twist plane of wire to create buccolingual apical force = TORQUE
How can amount of force applied to tooth be changed
Can be controlled by varying cross sectional diameter and form of archwire
Problems with fixed appliances
Enamel demineralisation Root resorption Soft tissue lacerations Perio Unwanted movement Pulp devitalisation
What can FA achieve
and how
Tooth alignment in all three planes - rotation, torque and tip control
Space closure - bodily movement
Components of FA
Brackets
Molar tubes/bands
Archwires
Auxiliaries
Bracket materials
Metal - SS
Ceramic - plastic
Aesthetic bracket materials
Ceramic
Lingual SS
Plastic
Problems with plastic brackets
Fracture
Distortion
Discolouration
Problems with ceramic brackets
Fracture
Abrasion of other teeth
Increased friction
Cost
Ceramic use
Only in upper arch
Only in lower if no overbite
Lingual appliance problems
Difficult technique
Cost
Traumatic to tongue
Lower molar bands - parts
Single tube for archwire
Hook for aux wires
Upper molar bands - parts
Additional tube for headgear
Hook for aux
Why are separators placed for molarbands
More comfortable
Easier
More accurate band selection
Directly bonded molar tubes - disadvantages
Difficult moisture isolation
Problem with wire if debonds
Can’t use with headgear
Archwire function and mechanism
Active - move teeth with wire
Passive - move teeth along wire
Active wires - material
Passive wires - material
NiTi -
SS - bodily movement
Auxiliary components
Elastics and springs
Weingarts
Gripping archwires
Tucker
tucking ends of quickties
Adam’s pliers
Making bends
Light wire plier cutters
Cutting light wires
Crown shears
Cutting ends of quickties
Distal end cutters
Cutting end of archwires in mouth
What do modules do
IO elastics?
Transpalatal archwire/quadhelix?
Secure archwire in archwire slot/ wire ligatures which are easier to tighten
Intra oral elastics used for traction - should be changed every day
Palatal/lingual arches can be placed in a quad helix fashion to provide extra anchorage for expansion e.g - made in lab from impression of teeth with bands on. bands then removed and placed into impression
