Biology of ortho treatment Flashcards
what is the goal of ortho apliances
To move the tooth via biological remodeling NOT mecahnical force
why does the tooth not move to bite force but does to light ortho force?
- PDL is a shock absorber in the alveolar bone
what allows the PDL to act as a shock absorber
The fluid in the PDL
- uncompressible, with bending alveolar bone
- squeezes out and cellular elements feel pressure
how does the tooth move in bitting
Relative to the jaw, but not moving against the alveolar bone
why is bone bending important for the jaw
stop decalcification of the bone
what does bone bending do
- Force against crystalline structure mechanically distorts crystals
- production of rapid current flow as electrons move
- force removed allows the crystals to come back to OG position
what is alveolar bone lost when a tooth is extracted
No rhythmic loading needed to generate piezo-electric currents, resulting in decalcification and resorption
what is the flow of electrons due to the rhythmic loading of bone
piezo-electric currents
is the piezo-electric current needed for ortho tooth movement
No
is electric current needed for ortho tooth movement
Yes, needed to alter cell membrane potentials
what theory do we use to do ortho movement
Pressure-tension theory
what happens if heavy force is sustained
PAIN
how does sustained pressure effect the tooth/alveolar bone
Puts pressure on the tooth then alveolar bone pushes back leading to a movement relative to the alveolar bone
what kind of signal is used for the pressure-tension expalanation
Chemical
how does pressure-tension lead to chemical release
- Mechanical distoration of cells in pDL leads to release of cellular contents
- decrease in Blood flow in pDL opposite of force applied changes O2 and CO2 levels in PDL releasing chemical
what happens as the PDL is increasing compressed
Blood flow is completely cut off
-necrosis
how long does pressure take to change CO2 and O2 levels and Prostaglandin/cytokine release
minutes
how long does it take for metabolic changes/cAMP changes/cell differeations to occur in cells when pressure is changed
about 4 hours
when does remodeling occur after pressure applied
About 2 days
time for blood Vessels within PDL to become occluded in the pressure side due to heavy pressur
3-5 sce
time for Blood flow to be cut off in compressed PDL under heavy pressure
minutes
time for cell death in compressed area under heavy pressure
hours
time for Cell differentiation in adjacent marrow spaces undermining resorption begins under heavy pressure
3-5 days
time for undermining resorption removing lamina dura adjacent to compresses PDL and tooth movement occurs under pressure
7-14 days
where are cells coming from to remodel in the case of heavier sustained pressure
Area adjacent to PDL not necrotic
one marrow spaces outside the lamina dura
what does undermmining resorption get its name
Large nectrotic areas in the PDL needed for osteoclasts to resorb the lamina dura
what does the necrotic area in the PDL of the undermining resorbing send
chem signals to stimulate formation of osteocalasts
what produces more movement, heavy or light force initiation
light force
how do yo u know if force is tooth heavy
if the tooth is loose(loss of lamina dura)
why does tooth tipping occur
When a single force is applied to the crown of a tooth
- resistance comes from the root
where is the center of resistance when pulling on a crown
Center of root
how do you do bodily movement on the tooth
Apply two forces simultaneously to the crown to load entire area of the PDL
how much force is needed to do body movement compared to tiping
2x as much (100g vs 50g)
how much loading occures during extrusion
loads the entire PDL volume
how much force is needed to extrude or rotate a tooth
The same as tiping
why does rotation or extruding not require more force than tipping
Roots are irregularly shapped, so any force lead to tipping somewhat
Force needed to rotate, extrude, and tip
50g for all of them
what is torque
Tooth movement where root apex is moved further than crown in a desired dirction
how much is needed for torque
about 75 g
how can we do intrusion
V. light compression at the apex (10g)
why do you need a light force in intrusion
force is concentrated in one small area so small force compresses more
how long must you wear an appliance to lead to movement
at least 4-8 hours a day
what is the best way to move a tooth
Light continuous force
how does light force cause a tooth to move
frontal resorbtion on the PDL side of the lamina dura
what is interrupted force
a spring with poor force decay where force drops to zero before reactivation
does undermining resorption occur in all patients
Yes, but just slightly
is heavy interrupted force okay
May be clinically acceptable even though it may cause pain
is continuous force possible with removable appliances
No
what force does a removable appliance create
Intermittent force
- maybe with some interrupted force
what is the appointment interval for ortho
4-6 weks
- movement takes 7-14 days
- 2 weeks to recover
does heavy or light force springs need more intervals
Heavy needs more interval checkups
- without will lead to tissue damage
should there be pain if you do the correct amount of force
not immediately, but later may feel aching for 2-4 days and leaves until appliance is reactivated
what leads to pain in ortho devices
ischemic areas in the PDL going to sterile necrosis
how to allivate some pain
chew gum of bite repeatedly on plastic wafer
what happens to the pulp initially after ortho appliances are installed
some inflammation at the root apex due to mild pulpitis
what is the effect of mild pulpitis in the tooth after ortho appliances are installed
no significance, with no loss of tooth vitality
why might a tooth lose vitality after initial ortho treatment
- history of previous trama or poor control of heavy ortho forces
- large movements of tooth after undermining resorption leading sever of vessels at apex through the labial cortical plate
can you move endo teeth
Yes
can clasts attack the root
yes, but can get repaired
what protects tooth against osteoclasts
- Uncalcified cememtum in non necrotic PDL
what parts of the tooth tend to get attacked by osteoclasts
cememntum adjacent to necrotic area
what happens to the attacked root eventually
New cememntum is formed to fill defect
does root remodling occur in ortho
Yes
when would apical root resorption not restore itself
Leads to coalscence of creates
- islands of root structure separated from root surface
where does loss of root structure tend to occur
Apex
how much root resorption occurs per year in a fixed appliance
about 1 mm (nota problem)
how much can a root resorb
- Mild to moderate generalized resoprtion
- Severe generalized
- severe local resorption
what is severe generalized resorbting
Loss of most of the roots on most teeth (rare)
what is severe localized resorption
loss of 1/4 of root in some teeth (2-3% of ortho patients)
what teeth tend to get severe localized resorption
Max incisors
what may lead to severe localized resoprtion
bring root apicies into contact with cortical bone
- movement linguallly (tipping crown facially)
when should you take x-rays to help be sure of severe localized resorption
6-9 months after ortho tretament begins
what do you do if severe localized resorption occurs
Keep treatment short, and compromise treatment goals
can ortho affect jaw bone growth
Yes
can you modify jaw if its not growing
No ( treat at period of rapid growth/adolescent growth spurt)
what is the ideal for tooth movement when growth modification is desired
No tooth movement( goal is not corection of maloclusion in growth mod treatment, correction of improper jaw relationship is)
when does skeletal growth occur
between early evening and midnight ( should wear at all hours)
what does excessive maxillary growth lead to
Class II
Long face problems
what is done to restrain maxillary growth
headgear
how much force to use for headgear
250g per side minimum to the maxilary first molars
when should headgear be worn
Early evening and at night (but not during the day) for about 12 hours
how often is headgear treatment successful
75% (some based on patient coperation
how can we speed up maxillary growth
Face mask (not very successful due to lack of force and suture shape)
why does the suture shape keep maxillary growth from occuring
Very well interdigitiated
when is a good time to spur growth of the maxilary
At an early age, before sutures lock up
can you restrict mandibular growth
not really, but can get the chin to rotate down and back
why does restriction of mandibular growth occur
children don’t like to ear it
difficult to load the whole TMJ
painful
what is the only way to stop mandibular grwoth
Surgery
how do you use class III elastics to restrain mandibular growth
elastics from miniplates at the base of zygomatic arch to mandibular canines
when to use elastics to mdoify mandibular growth
10-11 years old (need good bone, but early as possible )
- later than the facemask
how much force to use for modifying mandibular growth with elastics
150g on each side(worn all the time)
what is the rsult of soft tissue pulling the mandible foward
condylar process grows up and back
what are the major reasons for retetion
- Gingival and perio tissues require tmie for reorganization after ortho appliancecs removed
- teeth may be inherently unstable
- changes produce growth that can alter tratment
how long after removal does it take from the PDL to reorganize
3-4 months
how are the teeth while PDL reorganizes
unstable ungainst occlusal and soft tissue pressures
what can gignival fibers do if no retainer used
Are stretched and can rotate a tooth back to og position
how can one help with gingival fiber pull for aggressive rotations
sever the gingival fiber network aroudn the teeth before braces are moved (leading the interdental papilla
how far can teeth be moved to cause a change in the effect of soft tissue pressures
2mm for front incicors facially 0-1mm fo canines facially 2mm for the 1st premolars facially 2-3mm for 2st premolars facially 3mm for molars facially
all in the mandible
how can growth afect treatment
Growth continues after treatment regardless of how you changed it during appliance use
mandibular growth forward, presses incisors against teeth so you get movement
