Fixed Appliances Flashcards
What is a fixed appliance?
An appliance that cannot be removed by the patients
T/F
FA are capable of more movements than RA?
T
How do FA move teeth? and how is this done?
they create a force couple to the crown which is created by the interaction of the wire with the bracket slot
Which direction of forces creates an force couple?
equal forces in opposite direction
What is the advantage of creating a force couple?
this allows greater control and more precise control of the direction of tooth movement
Which components are needed to create the forces to move teeth?
brackets
archwires
auxillaries
What materials are archwires made from?
Ni-Ti Stainless Steel Gold CoCr Titanium Molybdenum alloy Aesthetic
What x sections can arch wires come in?
round or rectangular
What are the ideal properties of archwires used in the alignment phase?
large spring back low stiffness high stored energy biocomp low surface friction
WHat are the ideal properties of archwires used in the working phase?
high stiffness
low stored energy
Biocomp
Low surface friction
In the alignment and levelling phase which shape archwires are generally used?
NiTi round/rec
In the working and finishing phases of tooth movement, which shape arch wires are used?
stainless steel rectangular/round
What brackets are available?
stainless steel, ceramic, plastic
twin and self ligating
Which auxiliary components are used?
NiTi springs
elastomeric chain
bands
Which wires round or rectangular create more force and why?
rectangular
the closer the archwire fits the bracket, the more force created
What is the width of the bracket slot for the edgeiwse bracket? What is the consequence of having a wide or narrow bracket?
0.018/0.022’’
Wide bracket : reduces the inter bracket wire span and therefore the wire is less flexible. This is however more efficient for de rotation and mesiodistal control
What is the depth of the bracket slot in the edgewise bracket?
0.025/0.032’’
What types of movements can FA perform?
DTB
Derotation
Torque
Bodily (centre line correction, space closire, overjet reduction, intrusion and extrusion)
What is torquing?
movement of the root apex bucco-lingually +/_ crown
Which shape arch wire is needed for torquing movements?
rectangular
What was the straight wire appliance developed on?
andrews 6 keys to normal occlusion (1972) correct molar relationship correct crown angulation correct crown inclination no spaces no rotations flat occlusal plane
What are examples of FA?
pre adjusted edgewise appliances
- straight wire
- self ligating eg Damon
What is different about the straight wire system compared to other systems?
the brackets incorporate measurements from those of perfect occlusion therefore simplifies the wires used as before needed to pre bend the wires
3D control over tooth movements via the bracket design
WHat is special about the self ligating appliances?
no elastic ligatures which means less pressure is exerted onto the tooth
BUT the wire is not held in intimate contact with the tooth so less control over tooth movement
NO elastics - OH is better and the Damon system is thought to be quicker than traditional orthodontic methods
What are the features of brackets?
tie wings
bracket base
disto gingival marker
arch wire slot
What are the three types of movements the straight wire system can perform?
First order
second order
third order
What type of movement is first order?
labio-lingual (inout)
What type of movement is second order?
mesio-distal tip (crown angulation)
What type of movement is third order?
inclination/torque
How is first order movement controlled?
variation in the thickness of the bracket base
What does the thickness of the bracket base for first order movement take into account?
the variation of thickness of the bucco-lingual dimension on the tooth, from the labial surface of the tooth to the contact points
How is tip/angulation incorporated into the bracket design?
this is second order
optimal mesio-distal angulation of each tooth crown relative to the occlusal plane
tooth tip is greatest for canines
Angulation of the arch wire slot
How is third order incorporated in to the bracket design?
the angle the bracket base makes with with the bracket slot
For which teeth does the gingival portion lie labially to the occlusal portion?
all except upper incisors
Which bracket bases are curved and which bracket bases are flat?
curved: canines and premolars
flat: incisors
What is special about the lower incisor brackets?
they are chamfered to avoid the bite
Where must the bracket be placed?
in the middle of the labial face of the tooth
WHat advice should you give to patients once they have had the brackets and wires placed?
OHI
Pain
breakages
Diet
What are the five phases of FA treatment?
Levelling and Alignment Overbite Overjet SPace closure Finishing
What size and maerial wire is needed for the levelling and alignemnt phase?
0.012, 0.014, 0.016., 0.018 NiTi
ROund
What shape, size amd material wire is needed for overbite reduction?
0.019 x 0.025
SS round or rectangular
What effect does the wire have during the overbte reduction phase?
it leads to relative intrusion where the incirsors are held still and eruption of the molars and vertical growth of the face around teeth
Which wire is needed for overjet reduction?
large
rigid
rectangular wire (0.019 x 0.025)
SS
Which type of wire is needed for space closure?
large
rigid
stainless steel/rectangular
0.019 x 0.025
what type of wire is needed for finishing?
small diameter
thin round
stainless steel
What are the problems with FA?
Appliance related (gingival inflammation, decalcification, root resorption, soft tissue trauma) Patient related (attendance, breakages, OH, compliance)
How much root resprtion will occur on a 2 year ortho course?
around 1mm
What is the percentage of Nickel and Titanium in NiTi?
Nickel: 50%
Ti: 50%
What materials are in SS wires?
Chromium
Nickel
What are the three types of fixed appliances?
pre-adjusted appliance
Tip Edge appliance
Self ligating system
What are the advantages of pre-adjusted appliances?
no longer need to put bends in the wires as the movements are incoroparated into the bracket design
What is the disadvantage of using pre-adjusted appliances?
need very precise positioning of the brackets
What is the tip edge appliance?
allows tipping of the tooth in the initial stages of treatment with the use of round wires then when rectangular wires are used in later stages still have good control over tooth movement this system also uses preadjusted appliances
What is the advantage of selfligating system?
eg damon appliance
less friction created as there are no modules needed to hold wire in place
this means overall treatment time maybe reduced
