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Ortho > Biology And Biomechanics Of Tooth Movement > Flashcards

Biology And Biomechanics Of Tooth Movement Flashcards

1
Q

Another name for center of mass

A

Free bodies

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2
Q

Do teeth have center of mass?

A

No they center of resistance, they are not a free body because they are constrained by PDL and alveolar bone

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3
Q

Center of resistance

A

1/2 to 1/3rd from CEJ to apex in health

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4
Q

Free body

A

Center of mass/gravity = point of balance

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5
Q

Restrained body (tooth)

A

Center of resistance

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6
Q

Cres

A

Point at which resistance to movement can be concentrated for mathematical analysis

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7
Q

What happens when force is applied to the center of resistance?

A

Moves the tooth with no tipping

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8
Q

5 factors affecting the location of Cres

A

-Alveolar bone height
-Size of tooth
-# of roots
-root length
- # of teeth

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9
Q

Rigid body movements

A

Rotations, translations or combo of two

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10
Q

scalars

A

Magnitude and no direction
ex. Temperature, mass, length, time-algebric addition

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11
Q

Vectors

A

Magnitude and direction
Ex. Force, velocity, electric intensity field, acceleration

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12
Q

Force

A

-Load applied to an object that will tend to move it in the direction of the applied force
-unit = newton
-ortho = measured grams or ounces

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13
Q

Parallelogram law

A

Force 1 + force 2 = resultant force

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14
Q

Moment

A

Tendency of a force to rotate an object about an axis

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15
Q

Couple

A

-Two equal and opposite force whose lines of action do not coincide
-pure rotation around Cr

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16
Q

Mf = F x d

A

Moment caused by a force = force x distance

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17
Q

Force through Cr is?

A

Translation

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18
Q

For not through Cr is ?

A

Translation and rotation

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19
Q

What does ortho force cause not through Cr?

A

Mf

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20
Q

What does bracket/wiire interface cause?

A

Mc (moment caused by a couple)
In opposite direction

21
Q

Center of rotation (Crot)

A

-Point around which rotation occurs when an object is being moved
-point will vary depending on the force/moment/couple being applied
-connect the before and after positions of 2 points
-intersection of perpendicular bisectors of these lines

22
Q

Types of tooth movements

A

Tipping = 35-60g
Translation = 70-120 g
Rotation = 35-60g
Intrusion = 10-20g
Extrusion = 35-69 g

23
Q

Structure of PDL

A

Collagenous fibers
Cellular elements
Tissue fluid

24
Q

Cellular elements

A

Cells, blood vessels, nerves

25
Q

Cells

A

Mesenchymal cells
Fibroblasts
Osteoblasts

26
Q

PDL response to normal function <1 sec

A

Fluid incompressible, bone bends, piezoelectric signal

27
Q

PDL response to normal function 1-2 sec

A

Fluid expressed, tooth moves in PDL space

28
Q

PDL response to normal function 3-5 seconds

A

Fluid squeezed out, tissue compressed, pain if heavy pressure

29
Q

What does response of PDL depend on?

A
  • altered blood flow/ strain
    -chemical messengers
  • cell activation
30
Q

Two sides of tooth during ortho force

A

Tension side- osteoblast
Compression side - osteoclast

31
Q

Light force - frontal response minutes

A

Blood flow altered, oxygen tension changes, prostaglandins/cytokines released

32
Q

Light force - frontal response ~ 4 hours

A

increase cAMP levels, PDL cellular differentiation

33
Q

Light force - frontal response ~2 days

A

Tooth movement begins as osteoclasts/osteoblasts remodel bony socket

34
Q

Heavy force - undermining response/ PDL necrosis minutes

A

Blood flow cut off to compressed PDL area

35
Q

Heavy force - undermining response/ PDL necrosis hours

A

Cell death compressed area

36
Q

Heavy force - undermining response/ PDL necrosis 3-5 days

A

Cell death diff. In adjacent marrow space, undermining resorption begins

37
Q

Heavy force - undermining response/ PDL necrosis 7-14 days

A

Undermining resorption removes lamina dura adjacent to PDL, tooth movement occurs

38
Q

Light force vs Heavy force
How much movement ?
When do you see movement?
Which is better?

A

Both forces have thes ame amount of movement
Light force is within 3-5 days, heavy is within 7-9 days
Light force = consistent, heavy = dont see right away bc osteoclasts need to remove necrotic tissue
Light is better bc heavy is more painful

39
Q

Adverse response to ortho force

A

Pain
Remodeling
Mobility
Pulp

40
Q

What causes pain?

A

Inflammation at apex = increased tenderness to pressure
Ischemic areas in PDL= will undergo hyalinization

41
Q

Immediate pain response

A

Seconds to minutes
Heavy forces = pain develops almost immediately / PDL literally crushed
Lighter forces = patient feels little or nothing immediately

42
Q

Long term pain response

A

Hours to days
Time until pain appears = several hours
How it feels= mild aching sensation
teeth sensitive to = pressure
Soreness lasts = 2-4 days
Pain is worst = reactivation, initial activation

43
Q

Does root resorption continue after braces?

A

No

44
Q

Remodeling

A

Bone height = anticipated chances
Alveolar crest height decrease <0.5 mm
Tooth position determines alveolar bone position - teeth bring alveolar bone with them
Exception - tooth movement in presence of active periodontal disease

45
Q

Positive response to tooth movement

A

Remodeling
Erupting tooth brings alveolar bone with it
-missing max lateral incisor = permanent canine erupts mesial then moved back into its proper position (end of growth period)
-create alveolar bone for implant

46
Q

Why is there an increase in mobility

A

Bone remodeling = immature bone
PDL reorganization = disorganized
Widened PDL space

47
Q

Pulp response to force?

A

Modest and transient inflammation response with pulp - initial discomfort, no long term significance
Occasional reports of loss of tooth vitality = history of previous trauma, apex outside alveolar process

48
Q

Moving endo treated teeth

A

No contraindications, response of PDL, not pulp is key element in ortho movement

Ortho (19 decks)

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