Biology of Orthodontic Tooth Movement Flashcards
This is the soft tissue connecting teeth to the alveolar bone; approximately 0.5mm in width
PDL
What are the four things found trapped in the PDL
Many parallel collagenous fibers
cells; fibroblasts, osteoblasts, mesenchymal stem cells, and cells from the vascular structures
blood vessels and nerve endings
tissue fluids
The PDL is constantly doing these two things
adapting and remodeling
The PDL is adapted to resist these forces
short-duration forces; it acts like a “shock absorber”
Prolongued forces induce what to occur
remodeling of the PDL and adjacent bone
6hrs = movement
These two things are important in tooth movement
force magnitude and duration
The remodeling of the PDL is mainly conducted by what
fibroblasts
This is required for tooth movement beyond the PDL space
bone resorption
These are required for bone resorption
osetoclasts
These cells are not normally available in the PDL; must be recruited from the blood vessels or bone marrow
osteoclasts
This theory states that bony changes are caused by electrical signals
bioelectric theory
This theory states that bony changes are caused by chemical signals; this theory is accepted
pressure-tension theory
What are the three proponents of the pressure-tension theory
pressure and tension alter blood flow
formation and release of chemical messengers
chemical messenger change cell activities
What is the response to 1-2 seconds of sustained light pressure
tooth displacement within the PDL space
What is the response to 3-5 seconds of sustained light pressure
blood flow changes
What is the response to minutes of sustained light pressure
oxygen tension at compression side decreases leading to prostaglandins (PG-E) and cytokines (IL-1) release
What is the response to hours of sustained light pressure
chemical messengers cause metabolic change; second messengers such as cAMP release recruiting osteoclasts
They mature and are activated leading to frontal bone resorption
What is the response to 2 days of sustained light pressure
tooth movement beyond PDL space
What is the response to 1-2 seconds of sustained heavy pressure
tooth displacement within PDL space
What is the response to 3-5 seconds of sustained heavy pressure
blood vessels occluded on pressure side
What is the response to minutes of sustained heavy pressure
blood flow cut off to compressed PDL
What is the response to hours of sustained heavy pressure
cell death in compressed area
What is the response to 3-5 days of sustained heavy pressure
osteoclast recruitment from the bone marrow in the alveolar bone; maturation and activation leading to undermining bone resorption
What is the response of 7-14 days of sustained heavy pressure
tooth movement beyonds the PDL space
What is tooth movement pattern like under heavy forces
tooth moves quickly, then stops, then moves quickly due to undermining resorption
This type of force is required, while this other one is not
sustained force is required
continuous force is not absolutely required
What is the required time/day needed for efficient tooth movement
4-8hr/day
longer duration produces more efficient tooth movement
Force application pattern determines what
compression/tension regions
The compression area is larger during what than tipping
translation
with tipping, greater force is needed to produce the same pressure
Movement is slower in which type of people
adults
Children have these two characteristics that allow for faster movement
remaining alveolar growth
relatively less dense bone
Generally, tooth movement is faster in which arch
maxilla, because the bone density is lower
What are two drugs that may inhibit orthodontic tooth movement
prostaglandin inhibitors; NSAIDs, corticosteriods
bisphosphonates
This method to accelerate tooth movement involves making small indentations
local injury; regional acceleratory phenomenon (RAP)
This method to accelerate tooth movement involves “scoring” between the bony sockets
corticotomy assisted tooth movement (Wilckodontics)
What are three additional methods to accelerate tooth movement
vibration, phototherapy, ultrasound
This is resistance to unwanted tooth movement and resistance to the reaction force
anchorage
What is the goal of efficient orthodontics
maximizing tooth movement and minimizing unwanted “reactionary effects”
The amount of tooth movement increases with pressure only to what
a certain extent
What is reciprocal space closure
No anchorage is needed; both sides are working equally to move
What is maximum anchorage
when you don’t want to move the posteriors; anchor there
What is minimum anchorage
when you don’t want to move the anteriors; anchor there
This only allows bodily movement of the molars, which requires stronger pressure
stationary anchorage control
This is the use of temporary anchorage devices (TADs) to prevent unwanted tooth movement
skeletal anchorage
easy to remove because not osteointegrated
What happens to the pulp during orthodontic movement
pulpal reaction is minimal; loss of vitality may be due to previous trauma
This is a constant feature of orthodontic tooth movement; all patients exhibit some of this, 1-2% of them severe
root remodeling/resorption
Permanent loss of root surface occurs primarily where
at the apex
Which teeth are more prone to root resorption
incisors and second premolars
**What are four risk factors for excessive root resportion
abnormal root morphology; conical roots, pointed apices, dilaceration
prolonged treatment time, excessive and prolonged orthodontic forces
genetic predisposition
history of root resorption
What is the effect that orthodontics has on alveolar bone height
<0.5mm height reduction
This must be controlled before orthodontic movement
periodontal movement
