Periodontal Response to Ortho Tx Flashcards
why can we move teeth with orthodontic appliances
because the teeth are not bonded to bone but rather held in position by the PDL
what forms the PDL
- mesenchymal cells
- fibrobasts
- osteoblasts
- cementoblasts
- blood vessels
- nerve endings
what do fibroblasts do
- important role in response to mechanical loading due to occlusal forces
- the architect, builder ,and caretaker of the PDL
describe the PDL
- high rate of turnover of tissue within the PDL
- collagen synthesis reported highest in PDL tissue than any other CT in the body
- constant thickness at 0.18 to 0.25mm
what are the PDL functions
- supportive: attach teeth to the alveolar bone with the prinicipal fibers
- shock absorber: fluid displacement: light to moderate forces. principle fibers: heavier forces
- remodeling: tissue formation, tissue resorption, compensate for tooth wear and attrition
- sensory
what does tissue formation in the PDL
mesenchymal cells will differentiate into osteblasts, cementoblasts, and fibroblasts
what does tissue resorption in the PDL
same cells will transform into osteoclasts and cementoclasts
the nerve endings in the PDL provide:
- pain
- pressure
- spatial control of the lower dentition in relation to the upper - rest position
- TMJ location
- mastication
what do perioodntal ligament fluids do
shock absorbing effecti
if a tooth is subjected to large force for more than 1 second:
there is expression of fluid and the tooth moves within the alveolus
- the principal fibers take over
if a tooth is subjected to a large force for more than 3-5 seconds:
there is compression of the PDL by the root against the alveolar bone and pain
what other forces will also express tissue fluids
light and continuous
the PDL is essential for:
tooth movement and adjustment to the occlusal changes
in tooth migration or eruption there is a:
- resorptive bone wall
- depository bone wall
what happens in tooth migration
- constant mesial shift caused by the wear of contact points
- adjustment to occlusal wear
describe the resorptive bone wall
- alveolar bone resorption on tooth moving side
- osteoclasts in scattered lacunae on the alveolar bone wall
describe the resorptive bone wall
- resorption stops when the tooth is in occlusal or neuro muscular balance
- osteoblasts form new bone where new fibrils will attach
what happens in the reconstruction of the PDLq
- fiber attachment is re-established
- appears that same undifferentiated mesenchymal cells can become osteoblasts or osteoclasts
what happens in the depository bone wall
- mainly apposition of bone and rearrangement of PDL fibers
- the PDL will maintain its normal width of 0.25mm- key to bone remodeling
- thickness proportional to cellular activity
what is the goal of orthodontic tooth movement
- goal is to use the physiologic capabilities of the PDL to achieve desirable orthodontic movements
a force is placed on the tooth resulting in:
mechanical pressure or tension
the PDL will respond to force by:
bone resorption and remodeling of the periodontium
what happens in primary bone resorption
- mimics the physiologic bone remodeling process
- resorption of the alveolar bone wall on the pressure side
- bone formation by the PDL on the tension side
- light forces are needed to achieve this goal
what is happening on the pressure side
- reduction of blood flow in the pressure side
- direct resorption of alveolar bone wall by osteoclasts coming from the PDL
- may begin 12 hours after force application but usually at about 40 hours
