Lecture 7 Flashcards
In a typical force-deflection curve the stiffness of a material is given by what part of the curve?
-Slope of the linear portion (steeper the slope the stiffer the material)
What is the range in the force deflection curve?
-It is the distance along the X-axis where permanent deformation occurs (usually taken as the yield point)
What is the strength of a wire?
-Stiffness times the range
What is the proportional limit in a force-deflection curve?
-The force placed on the wire creates a proportional deflection in the wire ( graph remains linear)
What is the spring back in a force deflection curve?
-The position the wire will return to after it has been deflected.
What affects the major characteristics of a wire?
- The length
- The shape
- The cross section area
Forces that are maintained between activations are known as what type of forces?
-Continuous forces
Forces that drop to zero between activations are known as what type of forces?
-Interrupted forces
What is an example of an arch wire that gives continuous forces?
-Nickel titanium
What is an example of an arch wire that has interrupted forces?
-Stainless steel
What type of forces fall to zero when a removable appliance is taken out?
-Intermittent forces
What are the optimal intrusive forces?
10-20 grams
What are the optimal extrusive forces?
-35-60 grams
What type of orthodontic arch wire is strong, stiff, formable, and has been used routinely for many years?
-Stainless steel
What type of orthodontic arch wire is softer than stainless steel making it more formable, and then the wire can be heat treated to make it harder before it is inserted into the orthodontic appliance is what type?
-Chromium alloys (Elgiloy)
What are two great characteristics of nickel titanium alloys?
- Ability to apply light force over a large range of activations
- Its shape memory and super elasticity
What is the weakness of nickel titanium wires?
- Have poor formability
What is beta titanium?
-Combination of strength of springiness as well as good formability ( between stainless steel and nickel titanium wires)
T/F Orthodontic appliances should be reactivated more frequently than at 3 week intervals
False
-Should not
How many days does it take for undermining resorption to occur?
-7-14 days
How longer does it take for the PDL regeneration and repair to occur after the tooth has moved?
-7-14 days
What happens if you activate an appliance too frequently?
-You can damage the tooth and inhibit the repair process
T/F Orthodontic appliance increases the amount of gingival inflammation
True
What is the average amount of bone loss from orthodontic treatment?
-.5 mm or less and it rarely exceeds 1 mm
T/F In the absence of pathologic factors, a tooth that erupts too much simply caries alveolar bone with it
True
T/F When a tooth is intruded or extruded the alveolar bone moves with the tooth
True
T/F Unless a tooth erupts into an area of the dental arch, the alveolar bone will not form there
True
T/F Radiographically it can not be observed that the PDL space widens during orthodontic tooth movement.
False
- It can be observed
THe combination of a wider ligament space and a somewhat disorganized ligament means what will be observed in every patient?
-That there will be some increase in mobility
The heavier the force the grater the undermining resorption should be expected and the _________ that will develop,
-Greater the mobility
How long does pain typically last when an orthodontic appliance is placed on the teeth?
-2-4 days
During tooth movement what do clast cells attack?
- Cementum
- Bone
T/F Root remodeling and bone remodeling is a constant feature of orthodontic tooth movement
True
Under normal circumstances permanent loss of root structure would only occur why?
-If the repair phase was not able to replace the initially resorbed cementum
Shortening of the roots or root resorption occurs when cavities coalesce at the apex so that what occurs?
-Peninsulas of root structure are cut off as islands
T/F Shortening of the root doesn’t occur during orthodontic treatment
False
-It can occur
T/F Roots become shorter and thinner during orthodontic treatment
False
-They dont get thinner just shorter
What is a category 1 root resorption?
-No change in root length
What is a category 2 root resorption?
-Slight blunting
What is category 3 root resorption?
-Moderate resorption up to 1/4 of root length
What is a category 4 root resorption?
-Sever resorption greater than 1/4 of root length
What is camouflage orthodontic treatment?
-Moving the teeth into less than ideal positions to compensate for skeletal abnormalities
Severe resorption of a localized area typically involve what teeth?
-Maxillary incisors
T/F Severe root resorption can occur from parafunctional habits such as tongue thrusting and clenching or grinding.
True
What gene has been linked to external apical root resorption?
-Interleukin 1B gene
