biology of orthodontic tooth movement (dr. sun) Flashcards
the PDL is approx. ____mm in width.
0.5mm
what is the effect of tissue fluids in the PDL?
dampening effect/ shock absorber (viscoelastic element)
the nerve ending for perception of pain and proprioception in the PDL are __________ (myelinated/ unmyelinated).
unmyelinated
the PDL is adapted to resist __________ (short/long) duration forces.
short (seconds)
_______________ of ____________ occurs when prolonged forces act on the PDL.
remodeling of bone and adjacent PDL
a force magnitude as low as _____gm can induce tooth movement.
2
PDL remodeling is caused by _________, which are abundant in the PDL.
fibroblasts
PDL fibers have to remodeled in order to induce tooth movement. which fibers are especially important?
Sharpey’s fibers
_________ is required for tooth movement beyond the PDL space.
bone resorption
osteoclasts originate from _________ cells.
hematopoietic stem cells
T/F: osteoclasts are not readily available in the PDL
True, must be recruited from blood vessels or bone marrow
the ________ theory of tooth movement states that bony changes are caused by electric signals.
bioelectric theory
the __________ theory of tooth movement states that bony changes are caused by chemical signals
pressure-tension theory
what are the two principles of the bioelectric theory?
- force induces piezoelectric signals
2. bioelectric potential changes cell activity
what are the three principles of the pressure-tension theory?
- pressure and tension alter blood flow
- formation and release of chemical messengers
- chemical messengers change cell activity
____ seconds of light OR heavy pressure causes displacement of PDL within PDL space.
1-2 seconds
T/F: 3-5 seconds of heavy pressure occludes blood vessels on the pressure side
True
what does minutes of light pressure cause?
oxygen tension at compression side decreases the PG-E and IL-1 release
what does hours of light pressure cause?
chemical messengers cause metabolic change–>second messengers release–> osteoclast recruitment from blood flow–> frontal bone resorption
what does 2 days of light pressure cause?
tooth movement beyond PDL space
when is blood flow cut off to compressed PDL during heavy pressure?
within minutes
when does cell death occur in compressed area during heavy pressure?
hours
when does tooth movement beyond the PDL occur during heavy pressure?
7-14 days
when does osteoclast recruitment and activation–> undermining bone resorption occur during heavy pressure?
3-5 days
during light pressure, osteoclasts are recruited from ____________, but from _________ during heavy pressure.
blood flow, bone marrow inside the alveolar bone opposite the PDL
______ force is required for tooth movement, but ______ force is not absolutely necessary
sustained, continuous
based on clinical experience ____hrs of force is required to see movement.
4-8
tipping or translation has the larger compression area
translation, therefore greater force needed to produce the same pressure
within jaw bones, _________ may slow tooth movement, while ______ may accelerate it
osteopetrosis, osteoporosis
tooth movement is faster in the _______ and slower in the __________ because bone density is lower in the __________.
maxilla, mandible, maxilla
what two drug types inhibit tooth movement
prostaglandin inhibitors (NSAID, corticosteroids) and bisphonates
what are some methods to accelerate tooth movement?
- local injury: regional acceleratory phenomenon (RAP)
- corticotomy assisted tooth movement (Wilckodontics)
- other: vibration, phototherapy, ultrasound
optimal force
the amount of tooth movement increases with pressure only to a certain extent
T/F: optimal force varies with teeth and depends on the pressure produced at the PDLs
True
using light force is key to which kind of space closure strategy?
differential
T/F: no anchorage control is need for reciprocal space closure
True
stationary anchorage control
only allow bodily movement of the molars, which requires stronger pressure
skeletal anchorage
use temporary anchorage devices (TADs) to prevent unwanted tooth movement
regarding pulpal reactions, when should we try to avoid major tooth movements?
for calcium hydroxide filled anterior teeth with open apicies
T/F: most ortho patients do NOT experience root resorption, but 1-2% do.
FALSE: most patients do, with 1-2% being severe cases
permanent root structure loss usually occurs at the _______.
apex
which 2 teeth are more prone to root resorption?
incisors and second premolars
apical external root resorption categories
1- slight blunting
2- moderate 1/4
what are the risk factors for excessive root resorption?
abnormal root morphology
prolonged tx time (excessive force)
genetics
history of root resorption
usually alveolar bone height is resorbed by ______ during ortho tx
