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Orthodontics > Periodontal Responses to Orthodontic Treatment > Flashcards

Periodontal Responses to Orthodontic Treatment Flashcards

1
Q

Why can we move teeth with
orthodontic appliances?

A
  • Because the teeth are not bonded to bone but
    rather “held” in position by the periodontal
    ligament.
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2
Q

Periodontal ligament
(6)

A
  • Mesenchysmal cells
  • Fibroblasts (main cell type)
  • Osteoblasts
  • Cementoblasts
  • Blood vessels
  • Nerve endings
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3
Q

Fibroblasts
(2)

A
  • Important role in response to mechanical loading due to
    occlusal forces
  • The architect, builder and caretaker of the PDL. (McCulloch
    1966)
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4
Q

Periodontal ligament (PDL)
(3)

A
  • High rate of turnover of tissue within the PDL
  • Collagen synthesis reported highest in PDL tissue
    than any other connective tissue in body
  • Constant thickness at 0.18 to 0.25 mm
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5
Q

Periodontal ligament functions
(2)

A
  1. Supportive: Attach teeth to the alveolar bone with the
    principal fibers
  2. Shock absorber
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6
Q
  1. Shock absorber
    (2)
A

– Fluid displacement: light to moderate forces
– Principal fibers: heavier forces

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7
Q

PDL function
3. Remodeling:
– Tissue formation:
– Tissue resorption:
– Compensate for

A

Mesenchysmal cells will differentiate into osteoblasts, cementoblasts, fibroblasts (signaling factors)
Same cells will transform into osteoclasts, cementoclasts
tooth wear and attrition

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8
Q

PDL function
4. Sensory:
– Nerve ending to provide
(5)

A
  • Pain
  • Pressure
  • Spatial control of the lower dentition in relation to the upper (rest position)
  • Tmj location
  • Mastication
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9
Q

PDL Fluids
* Shock absorbing effect
(3)

A
  • If a tooth is subjected to large force for >1 second, there is expression
    of fluid and the tooth moves within 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
  • Light and continuous forces will also express tissue fluids
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9
Q

The — is essential
for tooth movement
and adjustment to
the occlusal changes

A

PDL

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10
Q

Tooth migration or eruption
(2)

A

–Resorptive bone wall
–Depository bone wall

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11
Q

Tooth migration
1. Constant — shift caused by the wear of
contact points (depends on the occlusion)
2. Adjustment to — wear ( teeth stay in
contact)

A

mesial
occlusal

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12
Q

Resorptive Bone Wall
(2)

A
  • Alveolar bone resorption on
    tooth-moving side
  • Osteoclasts in scattered
    lacunae on the alveolar bone
    wall
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13
Q

Resorption stops when the tooth is
in

A

occlusal or neuro muscular
balance

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14
Q

Osteoblasts form new bone where new — will attach.

A

fibrils

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15
Q

Reconstruction of PDL
* — attachment is re-
established
*Appears that same
undifferentiated mesenchymal cells
can become osteoclasts or
osteoblasts

A

Fiber

16
Q

Depository Bone Wall
* Mainly
* The PDL will maintain its normal
width of
*Thickness proportional to

A

apposition of bone and rearrangement of PDL fibers
0.25mm (key to bone remodeling.
cellular activity

17
Q

ORTHODONTIC MOVEMENT
Goal is to

A

use the physiologic
capabilities of the PDL to achieve
desirable orthodontic movements

18
Q

A force is placed on the tooth
resulting in

A

mechanical pressure or
tension.

19
Q

The PDL will respond by bone

A

resorption and remodeling of the
periodontium

20
Q

Primary bone resorption
* Mimics the
* Resorption
* Bone formation
* — forces are needed to achieve this goal

A

physiologic bone remodeling process
of the alveolar bone wall on the pressure side
by the PDL on the tension side
Light

21
Q

Pressure Side
*
*— resorption of alveolar bone wall by
osteoclasts coming form the PDL
* may begin

A

reduction of blood flow in the “pressure side”
direct
12 hours after force application, but usually at about 40 hours

22
Q

Pressure Side
* in contrast to physiologic tooth
movement, there is

A

complete breakdown
of old fibers and fiber bundles with
formation of new fiber elements

23
Q

Tension Side
(4)

A
  • cellular activity increases after 30-40
    hours of applying orthodontic force
  • new mineralized layer close to alveolar
    bone wall
  • after some time, osteoid produced by
    osteoblasts will cover this area
  • mineralization of osteoid
24
Q

The goal of the PDL response is to

A

maintain a constant width
(0.18-0.25mm)

25
Q
  • Response is related to the amount of — that is applied
    on the alveolar wall.
  • As the — increases, there is a dramatic — in
    blood flow in the PDL on the pressure side
A

pressure
pressure, reduction

26
Q

“Excessive orthodontic force”

A

Instead of primary bone resorption,
hyalinization of the PDL occurs

27
Q

The most frequent
“complication” in orthodontic
movement

A

Hyalinization

  • Force dependent
  • Forces of high magnitude press
    the root against the alveolar
    bone wall occluding the blood
    vessels
28
Q

Hyalinization
PDL responds with

A

local
degeneration and sterile necrosis
instead of the desired
proliferation and differentiation
of cells

29
Q

Hyalinized Zone
* occurs in about
* bone resorption is
* tooth will not move until

A

1-2 days
indirect or undermining because there are no living cells in hyalinized area
hyalinized zone has been cleaned up and adjacent alveolar bone wall is resorbed

30
Q

Repair
* Osteoclasts from
* Osteoclasts from
* Elimination of debris by
* Reorganization of the —

A

surrounding PDL
adjacent marrow spaces
scavenger cells and phagocytosis
PDL

31
Q

Factors Influencing Orthodontic Tooth
Movement
(3)

A
  • Character of bone (cancellous or cortical)
  • Force application
  • Applied force and time
32
Q

Character of Bone
(3)

A
  • Spongy, cancellous bone has the
    best characteristics for tooth
    movement
    *“Old” bone is more difficult to
    resorb than “young” bone
  • Dense cortical bone is much
    harder to resorb.
33
Q

Deleterious Effects of Orthodontic
Force
(2)

A
  • Root resorption
  • Long-term periodontal health
    specially in adults
34
Q
  • — bone resorption is the method of choice for tooth
    movement
A

Primary

35
Q
  • Impossible to achieve consistently with
A

fixed orthodontics

36
Q
  • Use the — force as possible
A

smallest

37
Q
  • Hyalinization may promote
A

root resorption (severity of the
cellular response?)

37
Q
  • Hyalinization may promote
A

root resorption (severity of the
cellular response?)

Orthodontics (9 decks)

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