Exam 2 - Biological Response to Force Flashcards
movement of the teeth from alveolar bone modification
orthodontics
modification of facial growth
dentofacial orthopedics
What are the biological structures for modifications in dentofacial orthopedics?
maxilla - suture
mandible - secondary cartilage
What is tooth movement based on?
the principle that pressure applied to a tooth is transmitted through the PDL to surrounding bone which remodels in such a manner that the socket migrates, carrying the tooth with it
What are the components of the tooth-bone attachment/PDL?
- collagenous fibers: sling-like shock absorber
- cellular elements
- vascular
- neural
- mesenchymal - tissue fluids
How thick is the PDL?
.5 mm thick
What is the sling-like shock absorber of the PDL?
collagenous fibers
What are the mesenchymal cells and their progeny?
connective tissue cells
- fibroblasts & fibroclasts (collagen and matrix materials)
bone cells
- osteoblasts & osteoclasts (remodelling of alveolar socket)
*blast = build
* clast = chew or breakdown
What is the range of masticatory lodges?
2-50 kg
2 = soft food
50 = hard food
Describe the events that happen at <1, 1-2 and 3-5 seconds with regards to the PDL
What are the gram forces during active stabilization/resting pressures? Are these forces in equilibrium?
not in equilibrium
What two things are required for tooth movement?
- stimulus
- biologic electricity theory
- pressure: tension theory - cell differentiation
- osteoclasts
- osteoblasts
What is biological electricity?
an electrical signal which can be described by the piezoeletric effect
*once off the force is the same but reverse
What are three characteristics of the piezoelectric effect?
- small charge differences
- quick decay
- opposite streaming with release of force
What is the pressure-tension theory?
a chemical signal
pressure side = compression
tension side = expansion
This theory is a chemical signal
pressure-tension theory
This theory is an electrical signal
Biological electricity
What things will happen from the pressure-tension theory?
- alteration in blood flow from pressure in the PDL
- formation and release of chemical messengers
- activation of cells
What is the physiological response to sustained light pressure on the PRESSURE side?
- 3-5 seconds
- alteration in blood flow - minutes
- 02 levels change
- increase in prostaglandins and cytokines - hours
- histologic changes in PDL cells - 2 days
- osteoclasts/blasts begin “frontal resoprtion”
What is the physiological response to sustained heavy pressure on the PRESSURE side?
- minutes
- blood flow stops - hours
- cell death from compression - days
- osteoclasts/osteoblasts begin remodeling adjacent marrow spaces - weeks
- “undermining resorption”
- removes dead bone
Describe this image of the physiologic response to sustained heavy pressure
PDL necrosis
Describe this picture of the physiological response to light force
frontal resorption is in response to
light force
undermining resorption is in response to
heavy force
What is better at controlling the positional movement of bone, heavy or light force?
heavy force because you can put the tooth where it needs to go
Describe the tooth movement (mm) vs. time (days) for frontal and undermining resorption
FRONTAL
- light wire
- continuous tooth movement
UNDERMINING RESPORPTION
- heavy wire
- force dissipates to 0 and the tooth will move, after the tooth moves the bracket will have to be moved for this to happen again so the patient will have to come in
What occurs during tooth tipping (biomechanics)?
- only 1/2 PDL loaded
- forces must be light ~ 50 gm
Where is the center of resistance during the tipping movement?
apical 1/3
What happens during tooth translation?
- crown and root move concurrently
- whole PDL loaded
- more force required ~ 70-120 gm
What is a force couple? When is it used?
placing a bracket wire
- 2 forces equal in magnitude but opposite in direction
- allows a moment vector of force in any direction
How many forces are required for tooth translation?
2
1. a moment force
2. a force couple
What occurs during tooth intrusion?
- only apex PDL loaded
- forces must be very light
- ~ 10-20 gm
What is the threshold that must be met for the force (hrs/day) to get the effect you want?
need a minimum threshold met of 6 hours
What are the three force decays?
- continuous force
- interrupted force
- intermittent force: patient puts it in and takes it out
Will an increase in pressure always can an increase in tooth movement?
No. There is an optimal force in which an increase in pressure will cause no more increase in tooth movement past this optimal force.
What occurs during simple space closure?
distribution of force over equal PDL areas results in reciprocal tooth movement
Is there reciprocal tooth movement during tipping and translation?
there is NOT reciprocal tooth movement so need to do a two stage space closure to fix the teeth (pull the anterior mandibular teeth posterior)
Which tooth has the largest anchorage (hardest tooth to move)?
maxillary first molar
Which tooth has the lowest anchorage (easiest tooth to move)?
mandibular central incisor
What occurs during two stage space closure?
- canine retraction
- using elastics to move canine into 1st premolar position
- omega loop on 2nd molar which causes mandibular anterior teeth to join the anchorage to help move the canines into place - incisor retraction
**6 teeth anchoring posteriorly = 1st and second molar, 2nd premolar
What is the result of excessive force on the PDL?
root resorption
Does resorption occur during most treatments? How?
Yes. moderate resorption during most treatments
generalized osteoclastic activity which shortens roots
Does resorption occur during most treatments? How?
Yes. moderate resorption during most treatments
generalized osteoclastic activity which shortens roots
a fibrous union between two or more bones
suture
As an individual matures, what happens to the development of the palatal suture?
suture becomes more tortuous (curving like a river)
What is use to treat a cross bite malocclusion? How long does it take?
- rapid palatal expansion
- 60 days
When is headgear used?
sutural compression to treat class II malocclusions when maxilla is large
Extraoral force via headgear is an example of what kind of force?
intermittent force
Is the mandibular condyle different than cartilagenous growth plates of long bones?
Yes. it has secondary cartilage which is able to be modified by changes in surrounding tissues
What does the shape of the mandibular condyles look like?
“like” a long bone with the epiphysis removed
In what direction does the condyle grow?
backwards, away from the ramus
What kind of growth increases ramus height?
condylar growth
Describe condyle growth. What does condyle growth cause?
- may grow forward or backward relative to the ramus
- mandibular growth rotations
Forward growth rotation of condyle causes
class II deep bite
Backward growth rotation of condyle causes
class II open bite
What do functional appliances do? What is an example
- apply force to teeth, mandibular condyle & sutures
- dentofacial orthopedic treatment: bionator appliance worn over 16 hours/day
What does a bionator appliance require?
bite construction from forward posture of mandible
What is an extraoral force to the mandible
What happens to growth potential as you age?
decreases with age
