week 5 Flashcards
what is the presence of removable appliances in the US
crozat applianes in early 1900s then dropped out of favor
what is the presence of removable appliances in Europe
complete reliance on andresen activators, schwarz between 1925-1965
Pros of removable appliaces
removable
More hygience
more esthetic
Easter for certain growth mod than fixed
disadvantages of Removable appliances
Rely on patient compliance
Less Precise force control than fixed appliances
involves lab work
Primary use of removable appliances
GRowth modification
minor tooth movements retention
what does a bionator do
Stimulates mandibular growth
Controls tooth eruption
what does a twin block do
Stimulates mandibular growth
Can include an expander
Can add headgear
what does a frankle appliance work on
Tissue borne with buccal shields/lip pads to reduce cheeck and lip pressure for expansion
what does a frankle appliance do
stimulates mandibular growth (lingual pads)
why use a face mask and reverse pull HG
for preadolescent patients exhibiting maxillary deficiency
how does a removable appliance work for tooth movement
Force for active tooth movement provided by finer springs
what provides retention for removable tooth movement devices
Acrylic, Labial bow and molar clasps
why use an anterior bite plate
Decrease overbite
why use a posterio bite plate
to increase overbite
what is a Hawley retainer
A labial bow, with clasps or rests on posterior teeth in acrylics with many variations of designs
why use spring retainers
Both retention and minor tooth movement
why use a tooth positioner
Minor tooth movement and retention
how is a tooth positioner set up
Fabricated on set-up models to which desired (minor) tooth movement has been included
what are contemporary ortho fixed appliances based on
Angle’s design in the 1800s
what are angle’s 4 major designs for fixed ortho appliances
E arch
Pin and tube
Ribbon
Edgewise
what did angle’s edgewise appliance do to modernize ortho
each bracket had horiztonal slots for better control of torque
how did the begg appliance control tooth movement
Modification based on Angle’s ribbon arch
except used auxilary springs for root control
how did the Begg appliance compare to the Edgewize
Begg had a wire and bracket contact that was small with minimal friction so teth can be moved quickly
- hard to control root
do we still use the begg appliance
No
what is the design of automatic rotational control
Twin brackets or single brackets with wings
what slots are used today in brackets
.018 and .022 inch slots
when was the pre-adjusted edgewise appliance developed
in the 1980s
how did the pre-adjusted edgewise appliance help
Refined manufacturing with built in adjustments for each tooth
- no repeated bends to compensate for difference amount teeth (required for standard edgewise appliance)
what is the straight wire technique
elements of ideal tooth prescriptions are fabricated into the appliance to minimize wire manipulation
is wire bending needed anymore
it is needed for the detailing and finishing phase as the ideal prescription may not be exactly ideal for individual patients and teeth
how does one compensate for differences in tooth horizontal position
by varying bracket base thickness or molar tube profile differences of tooth position using (first order, or in-out archwire bends)
when are 1st order bends used
in a standard edgewise band to compensate for horizontal position variations
how to adjust a pre-adjsted edgewise appliance for the horizontal
Make the bracket base of upper lateral incisors,
lower incisors thicker
Molar tube profile shorter than adjacent bracket slots
how to aid in changes mesio-distal angulation in standard edgewise
vary bracket slot tipping using 2nd order bends
how to do mesial distal angulation in preadjusted brack
align vertical slot with root of long axis, if alignment needed straight wire will be defllected once engaged to that tooth causing a change in angulation
how do you compensate for labial lingual angulation
3rd order bends
what are the steps of doing banding
Tooth separation
Band fitting
Band cememntation
- sealing with wax before curing adesive
what are the aspects of brackets
Direct and indirection bonding
Rebonding and debonding
what should archwire be adjusted to
Make sure the jaw/size/ype of archwires are correct
- know properties of different types of arch wire
hos is archwire tied to brackets
Elastic and stainless steel ties
why use power chains
Space closure
why use elastics
Improve occlusion move impacted teeth
shift midlines
why use open coil springs
Opening space
retracting teeth
why use closed coil spring
maintaining space
what are the fixed appliances for correcting class II occlusion
Herbst
MARA
Forsus
what are the advantages for class II correction
Patient compliance not need
larger dental movement than elastics
Herbst and MARA may be potentially have skeletal growth modification effects
what to use a jasper jumper to fix
Class II correction
when to use a lip bumper
Arch expansion
Molar distalization
Incisor proclination
what is a hyrax used for
Palatal expansion of the skeleton and dental
what does a lower arch expander expand
dental only
when to use a quad helix with finer sprins and w arch
preadolescent and early mixed dentition patients
what are helicies of a quad helix with finer springs used for
Activation and increase in range of tooth movement
what stainless steel is used with quad helix with finger springs and W arch
heavy (.040)
why use a transpalatal arch and lingual holding arch
Used for anchorage and space maintenance purposes
what arch wire is used for transpaltal arch and lingual holding arch
Heavier (.036 or above, stainless steel) than regular archwires
why use a pendulum appliance
Molar distalizaion
what is a pendulum appliance bound to
Bound to premolars
how does a pendulum appliance work
TMA wires with helicies inserted to molar tubes
Anchorage from palate
Primarily molar movement with some movement of anterior teeth as well
why use a habit appliance
To correct tongue or finger habit
what wire is used in a habit appliance
Heavy stainless steel wire
what is a habit appliance anchored to
Molars
what is the measure of force we use as a dentist
grams
what happens when you resolve a force vector
will produce compnents
is vector resolution the same as vector addition
opposite
how can you add vectors
resolve them to components in the 3 planes
what is the center of resistance
a point at which resistance to movement can be concetrated for mathmetical analysis
what determines the center of restistance for a free and retrained object
Free: center of mass/point of balance
Partially restrain: nature of external constains
where is the center of resistance for a teeth
the approximate midpoint of what is embedded in bone (Halfway between the apex and alveolar crest)
what does the center of resistance vary with
Alveolar bone height and the amount of root in both
does the center of restisance depend on ortho force
No (unless force changes bone height)
where does the center of resistance move during alveolar bone loss
Moves apically
where does the center of resistance move during root resorption
Moves coronally
what happens if the line of action does not pas through Center of resistance
Produces rotation of the tooth
- a moment
what is magnitiude
Mangitude of force times the perpendiculat distance from the Center of restistance to the line of action
what is a couple
2 forces, equal in magnitude, parallel and non colinear in oppsite direction
what does a couple produc
Pure rotation
what does a single force produce
rotation plus translation
how does a couple produce a pure rotation
The translational forces cancel out
what is the center of rotation
the point around which an object rotates
can the center of rotation change
yes, varies with force/moment/couple applied tot he tooth
why would you change the center of rotation
Different types of tooth movement and clinical goals
types of ortho tooth movement
Translation
Pure rotation
Combo of translation and rotation (tipping)
what is translation
All points on an object move in the same direction in the same rate
where must the line of action pass to do translation
Need to pass through center of resistance
does the bracet position determines translation
No, line of action determines
how can you produce translation without a force passing through the center of resistanec
canceling the moment produced by using a opposite moment created by a couple
what is tipping
when some points on an object move differently (direction, rate, both) than other points on the same object
where does the line of action pass to induce tipping
Does not pass through center of resistnace
what can a tipping movement be resolved to
Translational and rotational components
how does one determine the center of rotation
Examining to movements of two points on the tooth
where is the center of rotation for translation
Infintiy
where is the center of rotation for uncontrolled tipping
slightly apical to Center of resistance
where is the center of rotation for controlled tipping
Apex
where is the center of rotation for root movement (torque
Incisal edge
where is the center of rotation for pure rotation
C res
what is the difference in controlled and uncontrol/simple tipping
uncontrol: tooth rotates around a center near the middle of the root
control: tooth rotates around its apex
what is hooks law
Force of spring equals negative spring constant times the distance the spring is pulled on
what are most ortho archwires made of
Elastic (but both elastic and plastic phases are important)
what causes the Force deflection curve to change
Archwire diameters and material
what is stress
the force/area
what is strain
Change in length/original length
what is the elastic modulus
stress/strain
what is the slope of the stress strain curve
Elastic modulus
how is elastic modulus related to stiffness
directly
how is elastic modulus related to springiness
inversely
what is the difference of stress strain and Force deflection curve
S/S: intrisic (what maters is materials)
F/D: extrinsic (what maters is materials and shape/length)
should a homogenous material of differnet dimension only have one S/S or one F/D
one S/S but different F/D with different dimensions
what is springiness in a graph
1/stiffness
what is stiffness in a graph
slop of the linear portion of The F/D curve of the elastic modulus of the S/S curve
what is springback
The ability to return to OG shape
how long is spring back useful for
Beyond the lastic limit
what is range
The distance a wire can be bent elastic before permanent deformation
where does permanent deformation occur
at the yield point, .1% greater than the proportional limit
what is strength
Stiffness x range
what is the resiliance in a graph
Area under the S/S curve out to the proportional limit
what is formability
Amount of permanent deformation a wire can withstand before failure
what is the ideal ortho archwire characteristisc
High strength Low stiffness High range high formiability Capacity to taking weld/solder
what is the benifit of high strength
Produce desired force magnitude without excessive deflecting the AW
what is the benifit of low stiffness
Produce relatively constant force
what is the benifit of high range
Can deflect the AW to a great etend without permanent deformation
what is the benifit of High formability
Make bends on the AW without breaking it
is the ability to take weld/solder a mech property
No
what does the shape of an archwire affect
Shape control shear/tension force but not bending force
what does the cross-section diamter of AW affet
For bending
what does tying an archwire to brackets do to strength, springiness, and range
Increases strenth
decrease Springiness and Range
why add loops to an archwire
Increase range and springiness
what is the strength ranking of wires
Stainless> TMA>NiTi
what is the stiffness ranking of wires
Stainless> TMA> NiTi
what is the range of different wires
NiTI>TMA>stainless
what is the ranking of force required to cause the same level of deflection
Most force: stainless
Nitol
NiTI
what causes the superelastic property of Superelastic NiTI
phase transition between Austenitic and Martensic phases
what arch wireis used for inital alignment
Small size NiTI or steinless stels (if formability is needed
what arch wire is used for leveling
Relatively large size TMA or steel archwire
what AW is used for torque
Large rectangular Steel or TMA
what AW is used for finishing
Steel or TMA with size depending on purpose
what AW is used for growth modification device
LARGE stainless steel wires not used as common archiwre
