Lecture 7 Flashcards
Ortho tx uses prolonged pressure applied to the tooth where resorption and deposition occur. This bony response is mediated by what?
the PDL
If the PDL is destroyed during ortho (or other tx), what happens?
ankylosis
Under normal circumstances what is the size of space the PDL occupies?
.5 mm
What 2 things remodel the collagen of the PDL?
fibroblasts and fibroclasts
T/F the PLD is highly vascular
False; though it does contain some blood vessels and cells
What kind of nerve endings are in the PDL?
myelinated and unmyelinated free nerve endings
*sense perception of pain and proprioception
T/F the PDL space is filled with fluid
True
*same fluid found in other vascular areas
When is PDL fluid expelled?
When pressure is maintained
*after 3-5 seconds tooth is compressed against PDL and bone
T/F resting pressures of lips, cheeks, and tongue are balanced
False;
Mand ant: greater tongue pressure
Max incisor: Lip pressure is greater
what is the threshold for ortho force?
5-10 grams/square cm
What is the lip bumper?
removable appliance used in kids to create and save space necessary to accommodate adult teeth without extraction.
Harnesses the natural forces of the muscles surrounding the lower teeth to broaden the length of the dental arch
*tongue pushes teeth forward and out
Can the PDL itself generate forces to move a tooth?
yes. Eruption
what two things can cause chemical messengers that lead to remodeling of alveolar bone and tooth movement to be released?
1-Mechanical Compression of tissues
2- changes in the blood flow
*cytokines and prostaglandins
When is blood flow increased in an area of the tooth?
spaces where there is tension
*decreased blood flow in areas of compression
Decreased blood flow to the PDL increases what chemical messengers?
prostaglandins and IL-1 beta
*cAMP is the 2nd messenger
Do prostaglandins releases in primary or secondary response to pressure?
primary
Do prostaglandins stimulate osteoclasts or osteoblasts?
both
what causes undermining resorption?
The PDL is compressed to the point where there is no blood flow . Osteoclasts in the adjacent marrow space will attack the underside of the lamina dura
what is the main drawback of undermined resorption?
tooth movement is delayed because osteoblasts and clasts are unable do differentiate without blood flow.
Where are the osteoclasts activated from during during frontal resorption
Local population of progenitor cells in the PDL
*2nd wave of clasts come from distant areas via blood flow
Which happens first, alveolar frontal resorption or tension remodeling?
frontal resorption
*recruit osteoblasts from PDL
Frontal resorption offers a _____ tooth movement, while undermining resorption has a ______ resulting in ______ movement
smooth, delay, jumpy
Not only is tooth movement more ________ when the PDL area avoids necrosis, but pain is ______.
efficient, lessened
what kind of resorption is the rate limiting step?
undermining resorption
*there will always be at least some undermining
Do self ligating brackets accelerate tooth movement?
no
When does most dental trauma occur?
ages 7-10
*anterior incisor region
T/F avulsed primary teeth should be replanted
False
How long after a permanent tooth is avulsed and replanted should revals happen?
2-3 years
*check for PA abscess, root resorption, ankylosis
What are some examples of appropriate transport media for an avulsed tooth?
- Hanks Balanced Salt Solution (HBSS)
- Milk
- Saline
- Saliva (cup, or keep in vestibule)
- water (last choice)
What do you do if a tooth has an extraoral dry time of less than 1 hour?
replant immediately
*regardless if it was stored in fluid
How do you manage tooth surfaces of a tooth that has been avulsed for less than 60 minutes?
- keep moist
- handle crown
- don’t remove native landmarks
- remove debris carefully
- rinse and replant
What do you soak a tooth in that has an extraoral dry time of more than 60 minutes?
dental fluoride solution for 20 minutes
How do you manage a socket of a tooth with an extraoral dry time of greater than 60 minutes?
- gently aspirate or irrigate
- don’t curettage, vent, or cut a flap
- use blunt instrument to reposition socket
- replant
