robbypowell's version from 2018-09-13 20:14


Fischer Lecture:


define: statics
-the branch of mechanics concerned with bodies at rest and forces in equilibrium
define: kinetics
-branch of mechanics concerning bodies with a change in velocities
define: force
-load applied to an object that will tend to move it to a different position in space.
-although now we would tend to talk more about 'acceleration'


-Violo's Atlas


efficient treatment is better
-minimized adverse effects
-root resorption
-compliance decay
-more profitable


many uncontrolled variables
-Forces applied to the system are the one variable that we can control (given compliance)


1st law: inertia/
-an object at rest or in constant velocity is in equilibrium and will remain at that velovity (even if 0) unless acted on by an outside force


2nd law
-all forces have magnitude and direction


third law:
-for every force, there is an equal and opposite reaction
-if a finger presses on a stone... then the stone presses back on the finger


define: Line of action
-the line along which a force or the resultant of any number of forces may be considered to act


convention is that labial forces are positive forces
-extrusive forces are positive forces


-define center of resistance
-point that, if force is applied, tooth will move withouth tipping or rotation
-66% of the tooth (to apex)
-more accurately, midpoint of embedded portion of root
-for molars, furcation


define: define center of rotation
-the point at which a tooth ACTUALLY rotates as a result of the vector of resistance and forces




Question Answer
force application at bracket level corresponds to what movement?uncontrolled tipping
force application at CEJ level corresponds to what movement?controlled tipping
force application at center of resistance corresponds to what movement?translocation
force application apical to the center of resistance corresponds to what movement?torque


Question Answer
a force acting at some distance from the center of resistance will produce a _____


Fischer: runs large group practice---(multi-specialty)


invisalign is a great appliance... for getting the teeth almost straight.
- Dr. Tom Fischer


Question Answer
in order to get pure rotation without any translation... an equal force must be applied on the opposite end of center of resistance... this creates a ____couple
when a moment is applied without a coupling force you get both _____ and ____tipping & translation (of center of resistance)
t/f: couples have no relation to the center of resistance... (in terms of distance)true?
an edgewise appliance creates couples in _____ planes of space3 planes (BL, MD, Occluso-apically)
equilibrium... the sum of the moments and the sum of the forces always equal 0... for the overall system... BUT NOT FOR EACH TOOTH


bending wires overcomes the inherent shortcomings of the edgewise appliance
-symmetrical v bends...
-crosses the two brackets at the same angle... (
-results in moments with no extrusion or intrusion
-asymetrical... distance from bend is different for the two brackets... and angle is likely different too
-would result in moments, intrusive forces and extrusive forces




Extraoral forces


what influences the vector...
-where are you pulling from?
-what is the length of the outer arm?
-where are the arms of the facebow?


-what is the point of attachment?
-(not tooth, but arm of outer bow)
-what is the point of origin?
-cervical pull vs high pull


Alignment requires CONTROLLED tipping
-moving roots through bones takes a long time
-tipping takes much less time


Alignment requires CLEARANCE
-between bracket and wire
-play in the bracket slot
-idealler round & undersized
-proffitt says 0.003 minimum clearance
-for minimizing friction
-minimizing binding
-less binding on SS
-allowing for FREE SLIDING along arch wire
AW needs:
-long range of activation


-FLAT LOAD deflection curve
-can bend alot (to get into misaligned tooth) without distorting it
-50 Grams of Force (for alignment)
-for incisors and bicuspids


-Nickle Titanium generates consistent force regardless of amount of deflection,
-compared to SS which generates greater force with greater deflection
-SS can be used for alignment when no tooth is deflected greatly (2 or less mm))
-must be braided though
-will have greater binding


How to use NiTi-
-Activation & Reactivation:
-still needs reactivation to overcome force decay
-can take same wire out, let it return to memory... then put back in
-reactivates force


--- is bending loops in wires obsolete?


------ leveling:
-there are 2 ways to level a deep bite...
-extrude posteriors
-useful for growing patients
-intrude anteriors (focus on)
-useful for adults (non-growing adults)


-we want to level curve of spee
-put reverse curve of spee in archwire
-2nd order couple on molar
-moment that will procline the incisors
-"relative intrusion"
-appearance of intrusion due to angulation change
-0.016 round stainless steel wire will give the appropriate force of 100 g
-independent of slot size
-preferably pre-heat tx'ed
(class 3 surgical patients need decompensation, so the extreme proclination that we would associate with a rectangular reverse curve of spee wire is useful)
-JO 1973
-sstudied relapsed deep bite relapse
-if mandible doesnt grow then deep bite relapses
-occlusal plane angle tipping with reverse curve of spee AW SHOULD BE AVOIDED ON ADULTS
-no growth to accommodate in man or TMJ/glenoid fossae


key to intrusion:
-light continuous forces directed THROUGH the AXIS
-sometimes you can procline or recline as necessary




3 possibilities for correcting molar relationships:
-Differential Growth of Jaws
-Distal Driving of Upper Molars
-possible to do
-most easily accomplished with fixed light continuous
-NiTi springs
-continous force over their range
-no force decay
-cantilever.. also pushes premaxilla forward
-have to maintain the gain...
3 methodds:
-continue to use springs
-moment on molar... with distal tip force, molar cant come forward
-Carriere fixed functional
-differential A-P movement with extractions
-Class II camoflauge by exo upper 4's
-if patient is too old for growth
-good lower arch form
-good facial proportions
-esp max excess class 2's
-BEWARE when


-Upper and Lower 4's
-inherent problem with class 2 elastics
-extrude upper incisors and extrude lowar molars
(class 3 elastics would do opposite)
-extract 4 second bicuspids
-when you dont want to retract maxillary incisors
-claimed to help close the bite
-extract upper 4's and lower 5's
-routine mechanics will pull upper molars forward
-class 2 elastics
-maintain position of lower incisors
-extract upper 5's and lower 4's (in a class 3 situations)



-Differential A-P movement with elastics
-just use rubber bands and let them go to work...
-profitt says.. it works?
-Mandible rotates open
-so yay brachy-patient
-NOOOO for Dolicho-
Skeletal Class 1, Dental Class 2 div 1 with spacing... esp favor for brachy- avoid for Dolicho-


Differential growth
-extra-oral forces
-distal driving force on the upper arch
-restrict maxilla growth (supposedly)
-that was the initial idea anyway


-functional applies
-purport to accelerate growth of lower jaw
-not especially popular now
-still used for cranifacial anomalies
=muscles win over bone
-use functional appliance to position chin in face then do grafting surgery
-did work... do work...
-need growth potential (alot)
-growth direction
-between CVM 2 and CVM3 (really... want them to be in CVM 2)
-very compliance dependent for removable
-there are NO predictors for compliance...
-maybe how well they do in school is a measure of compliance
-Do you know how they train dolphins to jump?
-sea world in san diego
-animal behaviorists design experiments with genetically matched pods
-use giant rope... on bottom of tank
-reward dolphin for swimming over rope
-raise rope over time until out of water
-fixed functional appliances:


-not done in prepubertal growth
-not true mandibular stimulating
-tends to have more dental effect than skeletal
-dont get the same facial benefits


-cleaner and easier to clean




-one group did better than other
-the group that was had a trainer that gave out fish in the morning
-trainer said.. how do you get someone to do something for you if they don't like you?


attached to molar and cuspid
--Compliance sensitive--
-lower lingual arch
-ball and socket on molar
-attached to canine
-class 2 elastics
-1o week intervals
-mixed dentition
-only been used on halfstep class 2
-keeps brackets off front teeth
-teenagers like
-used on unilateral class 2 adult
-invisalign as anchor
-braces to finish


closing extracture space
group a... want anteriors to move back only
-group b want to split the space anterior and posterior
group c want to keep anteriors where they are and move posteriors forward


-often... roots can be all over if you're not careful!
-most of the time group B
-create a counter-acting couple force to prevent tipping
0.018 vs 0.022 slot
-closing loops... friction free is most advantageous
-can use sliding... but not as efficient
-en masse
-more efficient
-no patient cooperation
-what type of loop?
-depends on the mechanics that you want
-prescribed amount and no more
-force-level 250 grams (for group B)
-move incisors back as much as it moves post forward
-in 0.16x22 ss or 0.017x0.025 TMA
-to generate appropriate force level
-T-Loop most studied and shown to be effective
-we do a 40 degree v bend to give us the M/F ratio
-loop placed symmetrically
-10mm wide
-6 mm tall
-10:1 M/F ratio
-250 grams


=group B
-re-inforce posterior anchorage
-Nance appliance
-just use canine back... then move anteriors
-can use same T-loop
-group C
-take teeth out close to the back
-t-loop again


friction free technique called:
-Differential Moments
-using asymmetrical V-bends for T-Loop


by offsetting v-bend we can make one moment bigger than the other...
-super complicated... dont f with it until youre an expert


Beware of side effects
-tipping segments
-poorly activated loops
-wrong moment:force ratio
-flaring of anteriors
-not activated enough or moment too big


how does the T loop work
-root movement