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Ortho > 2, biology of ortho movement > Flashcards

2, biology of ortho movement Flashcards

1
Q

what are the injuries of tissues and their subsequent remodeling and repair?

A
  • resorption/apposition of bone
  • resorption of root surfaces
  • hyalinization of the PDL
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2
Q

under heavy forces what occurs in and around the tooth?

A
  • PDL compression on the pressure side with bone bending and transduction of a signal to cells: 1-2 seconds
  • the fluid is expressed from the PDL space and the tooth moves within the PDL
  • the blood vessels are occluded: 3-5 seconds
  • blood flow is cut off: minutes
  • cell death-hyalinization: hours
  • cell differentiation from bone marrow spaces: 3-5 days
  • undermining resorption and tooth movement: 7-14 days
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3
Q

how does the tooth move during the initial and secondary periods?

A

initially, the tooth will move a little bit, but then not really for a week or two. Then in the secondary period, there is pretty steady movement

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4
Q

lag phase

A

2-10 week, undermining resorption

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5
Q

progressive tooth movement

A

after lag phase, frontal resorption

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6
Q

Light forces

A
  • blood vessels partially compressed and PDL fibers are distorted: 3-5 s
  • blood flow is altered, oxygen tension is changing and release of PROSTAGLANDINS AND CYTOKINES: minutes
  • metabolic changes: chemical messenger to alter cell activity, enzyme levels change: hours
  • Increased cAMP levels, cellular differentiation starts: 4 h
  • tooth movement occurs with osteoblasts/clasts coupling: 2 days
  • frontal resorption
  • NO SIGNIFICANT hyalinization zone observable
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7
Q

what is the hyalinized zone?

A
  • it is a zone of “cellular necrosis” in the PDL that looses all organization or structure and looks like cartilage
  • under a light microscope, the hyalinizaed zone looks like ground glass
  • no tooth movement occurs until this zone has been remodeled
  • hyalinization is also observed during physiologic tooth migration
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8
Q

which cells are the first ones to invade the hyalinized PDL?

A

“pioneer cellls”

  • mononuclear cells with numerous processes and small inclusions
  • blood vessels are commonly the primary invading structures
  • the tissue that was away from the advancing edge of the hyalinization was typically invaded by larger mononuclear cells
  • CONCLUSION: hyalinized tissue is replaced by cellular and vascular invasion from surrounding undamaged PDL
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9
Q

what are the vascular changes on the pressure side?

A
  • at the ultrastructural level, 3 phases are seen (per rygh, 1972):
    1. intact blood vessels walls are filled with erythrocytes (30 minutes)
    2. Partial disintegradation of the blood vessels, degradation of the erythrocytes and formation of cryst-like structures (2h-48h)
    3. complete disintegration of blood vessels, amorphous necrotic cell remnants and degradation of crytal-like structures (1-7 days)
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10
Q

what hormones play a role?

the first messanger

A

PTH and calcitonin may play a role: both hormones are mediated by cyclic nucleotides and calcium
-prostaglandins(?), VIP, CGRP

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11
Q

what does physical distortion of the cellular membrane do?

A

-alters its polarity and increases permeability and activates membrane bound enzymes?

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12
Q

The second messanger

A

cAMP

  • Davidovitch and shanfel have reported that an increase in levels of cAMP is associated to tooth movement
  • increased levels of cGMP have also been reported
  • Somjen (1980) reported that the increase in cAMP coincides with the stretching of cells and is prostaglandin dependent
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13
Q

what i messanger is associated with cell stretching?

A

prostaglandins

-PGE2 levels increase on both tension and compression sides

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14
Q

what would injections of PGE2 do to the tooth/bone?

A

yamasaki showed that local injections of PGE2 may increase the rate of bone resorption (?) PGE2 may influence bone growth

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15
Q

which cytokines increase bone resporption?

A

iL 1 alpha and 1 beta

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16
Q

what does TNF alpha do?

A

induces increased IL production by monocytes, enhances PGE and collagenase production

17
Q

how many compartments does the PDL have during tooth movement?

A

4, from bone to cementum
-there is a net migration of cells from zone III to I (osteoblasts are observed at 21 h and bone formation starts as early as 42 h)

18
Q

what does bone bending do to deposition?

A

bone bending creates negative fields in the concave aspect of the bone surface and this leads to bone deposition

19
Q

what is the mechanism of action for bisphosphonates and its derivatives?

A

ex: fosamax (alendronate)
- inhibition of bone resorption via actions on osteoclasts and osteoclast precursor cells
- this decreases the rate of bone resorption

20
Q

in postmenopausla women, what considerations for ortho?

A
  • slower rate of tooth mevement bc bone is not as effectively resorbed and remodeled
  • perio concern?
  • retention phase is enhance bc of limited bone resorption
21
Q

what type of bisphosphonates are the most likely to accumulate in the alveolar bone?

A

nitrogen-containing bisphosphonates (alendronate)

22
Q

after third molars, which teeth are the most impacted?

A

maxillary canines

23
Q

% of maxillary canines impacted and where

A

85% of max impactacted canines are palatal and 15% are labial(crowding)
-85% of palatally displaced canines have adequate space to erupt, etiology related to size of max lateral incisors

24
Q

how can impacted canines be made to erupt spontaneously?

A

surgically uncover them

25
Q

what are different biological and etiological factors for root resorption?

A
  • individual susceptibility
  • genetics
  • chronological age
  • gender
  • systemic factors
  • bone density
26
Q

what are some of the systemic factors for root resorption?

A
  • hypothyroidism, hypopituitarism, hyperpituitarism

- hyperparathyroidism, hypopara.. and pagets disease(?)

27
Q

mechanical factors for root resorption

A
  • appliances
  • types of tooth movement
  • orthodontic force
  • treatment duration
28
Q

which roots have a higher incidence of resorption?

A

single-rooted teeth

29
Q

how does age affect root resorption?

A

-it doesn’t

30
Q

what direction of forces will increase the occurrence of root resorption?

A

intrustion, A_P

31
Q

Retention:

A
  • “secondary tooth movement”
  • PDL fibers will remodel for 15-232 days
  • the upper third of the PDL will remodel for a longer period of time (up to 232)
  • the apical third is more stable faster
  • free gingival and marginal fibers as well as transseptal fibers are very critical during retention

Ortho (6 decks)

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