Lecture 6 Flashcards
What do the mechanical effects on the PDL cells cause the release of?
- Cytokines
- Prostaglandins
- Chemical messengers
What happens to blood flow on the compressed PDL area?
-It decreases
What happens to blood flow on the PDL under tension?
-It increases
What does the alterations in blood flow create?
-Changes in oxygen/carbon dioxide levels
When a force is applied to a tooth the fluids are expressed out of what area?
The PDL space
When the blood flow through the partially compressed PDL decreases the chemical environment produces what?
- Increases in Prostaglandin E,
- Increase in IL-1 Beta
- Increase in cAMP
Is a prostaglandin release a primary or secondary response to pressure?
-Primary
T/F Prostaglandins stimulate both osteoclastic and osteoblastic activity
True
cAMP levels typically increase after how many hours of sustained pressure?
-4-6 hrs
If a removable appliance is worn less that how many hows per day it will not have any orthodontic effects?
Less than 6 hrs
What are the two thresholds for tooth movement?
- 5-10 grams/square cm of force
- 4-6 hrs of sustained pressure
If you have to much force and continuous pressure what happens to the blood vessels at the PDL?
-The blood vessels are totally occluded and a sterile necrosis of PDL tissue ensues
T/F When the PDL is compressed to the point that blood flow is totally cut off, differentiation of osteoclasts within the PDL space is no longer possible
True
After a delay of several days, osteoclasts within the adjacent marrow spaces attack the underside of the lamina dura in a process called what?
-Undermining resorption
During undermining resorption what causes tooth movement to be delayed?
- Delay in the stimulation of differentiation of the cells
- Delayed due to the thickness of bone that must be removed from the underside
Osteoclasts are activated from what during light pressure of tooth movement?
-Local population of progenitor cells int he PDL
With frontal resorption a steady attack on the outer surface of the lamina dura results in what>
-Smooth continuous tooth movement
With undermining resorption there is a delay in movement until what?
-The bone adjacent to the tooth can be removed
T/F Even with light forces in clinical orthodontics, small avascular areas are likely to develop in the PDL even with the lightest of wires
True
Most dental trauma occurs at what age and what area?
-7-10 in the anterior incisor region
T/F Avulsed primary teeth should be replanted
False
-Should not
Avulsed permanent teeth require follow up evaluations for a minimum of how many years to determine the outcome of therapy
2-3 yrs
If extraoral dry time is less than one hour with or without storage in a phsyiological media what should you do with the tooth?
-Replant immediately
If the extraoral dry time is greater than 60 minutes what should you do?
-Soak tooth in an accepted dental fluoride solution for 20 min, rinse with saline and replant
How far should the splint extend distally?
-at least two non involved teeth
What should home care during splinting teeth encompass?
- No biting on splinted teeth
- Soft diet
What is a load applied to an object that will tend to move it to a different position in space known as?
-Force
What is a point at which resistance to movement can be concentrated for mathematical analysis known as?
-Center of resistance
T/F For an object in free space, the center of resistance is the same as the center of mass
True
What is the measure of the tendency of a force to rotate an object around some force?
-Moment
A moment is generated how?
-By a force acting at a distance to the center of resistance
What are two forces equal in magnitude and opposite in direction known as?
-Couple
What will a couple produce?
-Pure rotation, spinning the object around its center of resistance
What is the point around which rotation actually occurs when an object is being moved known as?
-Center of rotation
The application of what to the crown of a tooth is the mechanism by which bodily movement of a tooth can be produced?
-Couple and Force
The center of resistance for any tooth is at approximately ______ of the distance between the apex of the tooth and the crest of the alveolar bone.
six-tenths
