4th class Flashcards
Orthodontic treatment is based on the principle that if ________ is
applied to a tooth, tooth movement will occur as the bone around the tooth
remodels.
prolonged pressure
Orthodontic treatment is based on the principle that if prolonged pressure is
applied to a tooth, tooth movement will occur as the bone around the tooth
_______.
remodels
Tooth movement is primarily a ________ phenomenon because
the bony response is mediated by the periodontal ligament.
periodontal ligament
PDL occupies a space approximately ___ mm in width around all parts of the root.
0.5 mm
_____ consists of:
• A network of parallel collagenous fibers.
• Inserting into cementum of the root surface on one side and into a relatively dense bony plate, the lamina dura, on the other side.
• Cellular elements.
• Including mesenchymal cells of various types along with vascular and neural elements.
• Tissue fluids.
PDL
Two possible control elements, ______ and ______ in the
PDL that affects blood flow, are contrasted in the two major theories of
orthodontic tooth movement.
biologic electricity and pressure-tension
The ______ theory relates tooth movement at least in part to changes in
bone metabolism controlled by biologic electricity that are produced by light
pressure against the teeth.
bioelectric
The _______ theory relates tooth movement to cellular changes
produced by chemical messengers by alterations in blood flow through the
PDL.
pressure–tension
Pressure and tension within the PDL, by reducing (pressure) or increasing
(tension) the ______ of blood vessels in the ligament space, could certainly
alter blood flow.
diameter
The pressure–tension theory (classic theory), relies on ______ rather than electric signals as the stimulus for cellular differentiation and ultimately tooth movement.
chemical
_________ are important in the cascade of events that lead to remodeling of alveolar bone and tooth movement.
Chemical messengers
Both _______ of tissues and _________ can cause chemical messenger release resulting in orthodontic movement.
mechanical compression; changes in blood flow
On the _____ side of tooth that is moving, the chemical mediators will stimulate osteoclasts to resorb bone
Pressure side
On the _____ side of tooth that is moving, the chemical mediators will stimulate osteoblasts to build bone to occupy the space made by the movement
Tension side
Whta are the 2 types of mediators used in orthodontic movement?
Cytokines and Prostaglandins
______ appears to be the
mechanoreceptor in PDL cells, and its compression is at least
part of the reason that PgE2 is released.
Focal Adhesion Kinase (FAK)
_____ and ______ levels increase within
the PDL within a short time after the application of pressure.
Prostaglandin and Interleukin-1 Beta
Two types of drugs are known to depress the
response to orthodontic force and may influence
current treatment:
Corticosteroids / NSAIDs
Bisphosphonates
What is the most important chemical mediator in orthodontic tooth movement?
PGE2
Most over-the-counter analgesics are _____ and therefore are prostaglandin inhibitors.
NSAIDs
The major exception of NSAIDs which do not inhibit PGE2 is _______ , which acts centrally rather than peripherally.
Acetaminophen (Tylenol)
•They act as specific inhibitors of osteoclast-mediated
bone resorption.
•As the result, the bone remodeling necessary for tooth
movement is slower in patients on this medication.
Bisphosphonates
For a tooth to move, osteoclasts must be formed so
that they can remove bone from the area adjacent to
the _______ part of the PDL.
compressed
Osteoblasts also are needed to form new bone on the
______ side and remodel resorbed areas on the
pressure side.
tension
_____ forces are compatible with survival of cells within the
PDL and a remodeling of the tooth socket by a relatively
painless “frontal resorption” of the tooth socket.
Lighter
Lighter forces are compatible with survival of cells within the
PDL and a remodeling of the tooth socket by a relatively
painless _____ resorption of the tooth socket.
“frontal resorption”
_____ forces lead to rapidly developing pain, necrosis of
cellular elements within the PDL, and the phenomenon of
“undermining resorption” of alveolar bone near the affected
tooth.
•Heavy
•Heavy forces lead to rapidly developing pain, necrosis of
cellular elements within the PDL, and the phenomenon of
_____ resorption of alveolar bone near the affected
tooth.
“undermining resorption”
•When ___ but prolonged force is applied to a tooth:
•PDL partially compressed.
•Blood flow decreases.
•Within a few hours, mediators release.
•Changes in the chemical environment produce cellular
differentiation and activity.
•The tooth moves in its socket
light forces
_____ forces
•If the sustained force against the tooth is great enough to
totally occlude blood vessels and cut off the blood supply to
an area within the PDL.
•Cells within the compressed area of the PDL being
stimulated to develop into a sterile necrosis forms within the
compressed area.
•Because of its histologic appearance as the cells disappear, an
avascular area in the PDL traditionally has been referred to as
hyalinized.
•After a delay of several days, cellular elements begin to
invade the necrotic (hyalinized) area.
•Osteoclasts appear within the adjacent bone marrow spaces
and begin an attack on the underside of the bone
immediately adjacent to the necrotic PDL area.
•When hyalinization and undermining resorption occur, an
inevitable delay in tooth movement results
Heavy forces
If there is an avascular area in the PDL that has been cut off from blood supply and necroses, it is called _____
Hyalinized
