Ortho - Lecture 6: Biology & Biomechanics Flashcards
Center of mass/gravity; point of balance
Free body
The center of resistance for a tooth with PDL/bone surrounding it is ____________ of the root length (from CEJ to apex)
1/2 to 1/3
Point at which resistance to movement can be concentrated for mathematical analysis
Center of resistance
What do the following factors affect the location of?
Alveolar bone height
Size of tooth
Number of roots
Root length
Number of teeth
Center of resistance
All rigid body movements are ___________ or ___________, or a combination of the two
rotations; translations
Have magnitude, but no direction
Scalars
Examples are temp, mass, length, time-algebric addition
Scalars
Have magnitude and direction
Vectors
Examples are force, velocity, electric intensity field, acceleration
Vectors
T/F: A load applied to an object will tend to move it in the direction of the applied force
True
How is force measured in ortho?
Grams or ounces
Tendency of a force to rotate an object about an axis
Moment
2 equal and opposite forces whose lines of action do not coincide
Couple
Force through CR = ?
Translation
Force NOT through CR = ?
Translation + Rotation
Pure rotation around CR = ?
Couple
Mf means what
Moment caused by force
Mc means what
Moment caused by couple
Force equation
Mf = F x d
Ortho force NOT through CR causes…
Mf
Bracket/wire interface causes…
Mc (in opposite direction)
The point around which rotation occurs when an object is being moved; will vary depending on force/moment/couple being applied
Center of rotation
Connect the before and after positions of 2 points, it is the intersection of the perpendicular bisectors of the lines
Center of rotation
What is the bone-forming organ?
PDL
Which part of PDL?
Function = ligament attachment, resist movement
Collagenous fibers
Which part of PDL?
Function = build and remodel collagen
Cellular elements
Which part of PDL?
Function =
Tissue fluid
How many seconds of force cause the following to occur to the PDL?
Fluid incompressible, bone bends, piezoelectric signal
1 sec
How many seconds of force cause the following to occur to the PDL?
Fluid is expressed, tooth moves in PDL space
1-2 seconds
How many seconds of force cause the following to occur to the PDL?
Fluid is squeezed out, tissues compressed, pain if heavy pressure
3-5 seconds
What are the 3 parts of biological control of tooth movement?
Altered blood flow/strain
Chemical messengers
Cell activation
How much time of light force causes the following to occur to the PDL?
Blood flow altered, oxygen tension changes, prostaglandins/cytokines released
Minutes
How much time of light force causes the following to occur to the PDL?
Metabolic changes, chemical messengers affect cellular activity, enzyme levels change
Hours
How much time of light force causes the following to occur to the PDL?
Increased cAMP levels, PDL cell differentiation
~4 hours
How much time of light force causes the following to occur to the PDL?
Tooth movement begins as osteoclasts/blasts remodel bony socket
~2 days
How much time of heavy force causes the following to occur to the PDL?
Blood flow cut off to compressed PDL area
Minutes
How much time of heavy force causes the following to occur to the PDL?
Cell death in compressed area
Hours
How much time of heavy force causes the following to occur to the PDL?
Cell differentiation in adjacent marrow spaces, undermining resorption begins
3-5 days
How much time of heavy force causes the following to occur to the PDL?
Undermining resorption removes lamina dura adjacent to PDL, tooth movement occurs
7-14 days
What type of force causes the following? What is the resulting resorption?
Blood flow altered, but not stopped
Cell differentiation in PDL
Light force -> frontal resorption
What type of force causes the following? What is the resulting resorption?
Cell death in PDL
Must rely on bone marrow
Heavy force -> undermining resorption
What are the adverse biological effects of ortho force and tooth movement?
Pain
Root resorption
Bone loss
Mobility
Pulp
Pain is caused by inflammation at the _________ and ischemic areas in the _______
apex; PDL
Heavy or light force?
Pain develops immediately; PDL is crushed
Heavy
Heavy or light force?
Pt feels little or nothing immediately
Light
When is pain going to be the worst?
Initial activation
How long until pain appears?
Several hours
How will the pain feel?
Mild aching
What are teeth going to be sensitive to?
Pressure
How long will the soreness last?
2-4 days
When will teeth be sensitive again?
Reactivation
There is a great deal of ___________ variation when it comes to pain
individual
Does root resorption continue after braces?
No, if you stop the forces as soon as you notice resorption
What decreases as a result of ortho treatment? How much?
Alveolar crest height; 0.5mm
What determines alveolar bone position?
Tooth position
(exception: ortho during active perio)
Sometimes, an erupting tooth can bring alveolar bone with it. Describe the example given in class
Missing lateral incisor
Canine erupts mesially then moved back to its proper position, creating alveolar bone for the implant
Why is there an increase in mobility with ortho?
Bone remodeling (immature bone)
PDL reorganization (disorganized)
Widened PDL space
How does the pulp respond to force?
Initial inflammation
(no long-term signficance)
In what cases have there been reports of loss of tooth vitality during ortho tx?
History of previous trauma
Apex outside alveolar process
Is it contraindicated to move teeth treated by endo?
No, you can do that! Response of the PDL, not the pulp, is key element in ortho movement
