Biomechanics 1 Flashcards
first step in tx
PATHOLOGY should be controlled first
then ortho problems
- so treated in priority order
biomechanics - genreal
principles that reveal how to accomplish tooth movement
application of force –>
tissue response –> orthodontic movement
principles of bio of tooth movement
- if prolonged pressure is applies to a tooth movement will occur
- bone is selectively removed in some areas and added in others
- tooth moves through the bone carrying its attachment apparatus with it
- tooth movement is primarily a periodontal ligament phenomenom (so need this healthy structure for movement)
- like no pdl ankylossis is incapable of movement
what is necessary for tooth movement? - clincial level
prolonged application of force
graph of movement at tissue level
1-3 days – displacement
2-10 weeks delay / long phase
then accelarates up to acceleration and linear
describe the initial strain / primary displacement
- initial reaction following force
- immediate movement within the viscoelastic pdl cradle
- fluid movement
- magnitude depends on root length/ bone height/ age/ pdl elasticity
- areas of pressure and tension are created
- pressure : pdl fibers and bone are compressed
- tension pdl is stretched
pressure
pdl fibers and bone is compressed
tension
pdl is stretched
time needed for movement
minimal of 6 hours for movement
more efficient movement with longer duration of force applied
dleay / lag phase general
Chain of reaction to allow within a few weeks of 2 -10 weeks to see the clinical movements
tooth closer to bone?
pressure vs farther away = areas of tension
delay / lag phase details
no movement but intense remodeling action around the tooth
relative force dependent (force applied per unit area)
- whats the ‘clincial root value’
partial or absolute occlusion of pdl blood vessels
structureal and biomechanical changes
bone remodeling
bone remodeling occurs
delay / lag phase
force determines
how long the delay / lag force lasts
partial occlusion
lower relative forces
blood vesels adaps to new environmnet
localized angiogenesisi to bypass occluded areas
absolute occlusion
higher forces
first time force is applied
complete occlusion of blood flow
temporary necrosis of immediate area
acceleration and linera phase - timing
LIGHT CONTINUOUS FORCES allow constant responsive state in tissues and more effective ortho movement
this is a response to adaption at bone/ pdl changes - directly affected by force magnitude - higher forces may show lag phase
rapid tooth displacement
frontal resorption
light forces distributed in large areas
- right in front of root surface
transient ischemia
oxygenated is limited but still present (partial occlusion)
adaption and initiation of frontal resorption by pdl osteoclasts
movement occurs within 3-4 days
when does frontal resoprtion occur? by?
3-4 days by pdl osteoclasts
when does frontal resoprtion occur? by?
3-4 days by pdl osteoclasts
undermining resopriton details
larger forces applied
complete vascular occlusoin
tooth movement in undermining resorption
12-15 days after bone remodeling
pressure areas - more detailed
bone resorption from osteoclasts coming from the PDL
FRONTAL RESORPTION
tension areas - more detailed
bone apposition by osteoblats coming from the PDL
osteogenesis
bone formed in soft tissue where it was never there before
intramembranous and endochondral
embryonic development
ORTHO HAS NOTHING TO DO WITH THIS
BONE MODELING
bone formation on existin bone tissue
over extended areas for significant periods of time
growth and development
change in shape of structure or translation of surface
osteoclasts and osteoblsts act at different sites
which is a reparative mechanism?
bone remodeling with 4 different stages
4 stages of bone remodeling
- activation
- resorption
- reversion
- formation
light force
tooth contiues to mvoe with frontal resopriton
heavy force
repeated hyalinization - frontal resoprtion cycles
center or mass or gravity
point through which an applied force must pass for a FREE OBJECT to move linearly without rotation
point of balance
center of resistance
point through which if an applied force must pass for a RESTRICTED BODY to move linearly movement without rotation
in teeth - CR depends on the root length , morphology, and attachemnt levels
1/4 to 1/3 distance from CEJ to apec
Center of resistence in teeth
in teeth - CR depends on the root length , morphology, and attachemnt levels
1/4 to 1/3 distance from CEJ to apec
usually around fircation in molars *
force in general
mass multiplied by acceleration
vectors with magnitude (size) and direction
direction – line of action, sense and point of origin
resultant?
multiple vectors can be added
pure translation of tooth?
if forces passes through CR directly – produce pure translation
ortho forces are applied where
+ implication
on teh CROWN LEVEL
- so will generate rotation as well
center of rotation
a point about which a body appears to have rotated, as determined from its initial and final positions
it can be located ANYWHERE on or off the tooth
center of resistance is where
always on the root
removable appliances produce
SINGLE FORCES
fixed appliances may produce
single forces and or couples
- more precise outcomes
types of tooth movement and result
tipping
translation
root movement
rotation
result from the application of moments and forces (moment/force) ratio
describe tipping
greater movement of the crown
center of rotation is apical to center of resistance – apex is staying more steady
can be controlled or uncontrolled depending on location of Center of rotation
uncontrolled tipping
simplest movement
single force
non uniform stresses are generted
greatest stress at CROWN AND APEX
moment/ force ratio 0:1 to 5:1
0:1 to 5:1 ration
moment / force ratio
within the uncontrolled tipping
in uncontrolled tipping where is the center of rotation adn resistenc e
center of rotation located between C of resistance and apex
tip and apex move in OPPOITE DIRECTOIN
controlled tipping
very desirable - minimal stress at apex - less chances of root resorption
moment/ force ratio 7:1
force AND COUPLE
system of forces
center of rotation AT APEX – only major movement is at the crown
where is movement occuring in controlled tipping
movement at the CROWN
– the center of rotation at the apex moves very little
movement that allows for closure of space
translation
translation - basic
bodily movement
translation
single force at center of resistance
system of forces – force NOT passing through C resistance and couple
moment / force ratio 10: 1
translaiton ratio and movement
10: 1
root and corwn moving in same distance in same HORIZONTAL DIRECTION
center of rotation at infinity
a lot of control
root movement general
toque movement
root movement moment/ force ratio
12:1
root movement changes what
the tooths axial incliniation - want the root position to change
greater stress where with root movement
greatest stress at apex level (may cause undermininig resorption and slow the movement)
so greater stress at the apical level
greater stress where with root movement
greatest stress at apex level (may cause undermininig resorption and slow the movement)
so greater stress at the apical level
movement in root movement
root moves while crown stays stationary – center of rotation at the INCISAL EDGE OR BRACKET
ROTATION
pure rotation requires a couple
if single force is sued, C of rotation is outside the tooth
no net force acts at center of resistance
need two forces opposing
rotation movement
single force not passing through center of resistnace
c of roation outside of tooth
pure rotation
couple acts on tooth
center of rotation is located at center of resistance
- like on either sife of the tooth
when does Crot = CR
pure rotation
anchorage
resistance to unwanted tooth movemet
teeth move differently because
due to variations in their root surface – more root surface more resistance to movement
more root SA?
harder to move – more resistance
friction? - very general
opposes movement as well
friction - more detialed
it is resistance to the direction of movement, when moving a solid object tangentially against one another
sliding mechanics
teeth slide on the wire
the higher the diameter the wire , the higher the friction, the greater the anchorage
relationship between wire and friction
higher diameter of wire – the higher the friction – the greater the anchorage
anchorage
resistance to unwanted tooth movement
examples of intraoral anchorage
TPA
lingual arch
TPA
transpalatal arch
connects the maxillary 1st molars and creates an anchor u nit of 6 roots
minimum force needed for movement
6 hours a day
