Biology And Biomechanics Of Tooth Movement

Question 1

Another name for center of mass

Answer 1

Free bodies

Question 2

Do teeth have center of mass?

Answer 2

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

Question 3

Center of resistance

Answer 3

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

Question 4

Free body

Answer 4

Center of mass/gravity = point of balance

Question 5

Restrained body (tooth)

Answer 5

Center of resistance

Question 6

Cres

Answer 6

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

Question 7

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

Answer 7

Moves the tooth with no tipping

Question 8

5 factors affecting the location of Cres

Answer 8

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

Question 9

Rigid body movements

Answer 9

Rotations, translations or combo of two

Question 10

scalars

Answer 10

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

Question 11

Vectors

Answer 11

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

Question 12

Force

Answer 12

-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

Question 13

Parallelogram law

Answer 13

Force 1 + force 2 = resultant force

Question 14

Moment

Answer 14

Tendency of a force to rotate an object about an axis

Question 15

Couple

Answer 15

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

Question 16

Mf = F x d

Answer 16

Moment caused by a force = force x distance

Question 17

Force through Cr is?

Answer 17

Translation

Question 18

For not through Cr is ?

Answer 18

Translation and rotation

Question 19

What does ortho force cause not through Cr?

Answer 19

Mf

Question 20

What does bracket/wiire interface cause?

Answer 20

Mc (moment caused by a couple)
In opposite direction

Question 21

Center of rotation (Crot)

Answer 21

-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

Question 22

Types of tooth movements

Answer 22

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

Question 23

Structure of PDL

Answer 23

Collagenous fibers
Cellular elements
Tissue fluid

Question 24

Cellular elements

Answer 24

Cells, blood vessels, nerves

Question 25

Cells

Answer 25

Mesenchymal cells Fibroblasts Osteoblasts

Question 26

PDL response to normal function <1 sec

Answer 26

Fluid incompressible, bone bends, piezoelectric signal

Question 27

PDL response to normal function 1-2 sec

Answer 27

Fluid expressed, tooth moves in PDL space

Question 28

PDL response to normal function 3-5 seconds

Answer 28

Fluid squeezed out, tissue compressed, pain if heavy pressure

Question 29

What does response of PDL depend on?

Answer 29

- altered blood flow/ strain -chemical messengers - cell activation

Question 30

Two sides of tooth during ortho force

Answer 30

Tension side- osteoblast Compression side - osteoclast

Question 31

Light force - frontal response minutes

Answer 31

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

Question 32

Light force - frontal response ~ 4 hours

Answer 32

increase cAMP levels, PDL cellular differentiation

Question 33

Light force - frontal response ~2 days

Answer 33

Tooth movement begins as osteoclasts/osteoblasts remodel bony socket

Question 34

Heavy force - undermining response/ PDL necrosis minutes

Answer 34

Blood flow cut off to compressed PDL area

Question 35

Heavy force - undermining response/ PDL necrosis hours

Answer 35

Cell death compressed area

Question 36

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

Answer 36

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

Question 37

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

Answer 37

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

Question 38

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

Answer 38

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

Question 39

Adverse response to ortho force

Answer 39

Pain Remodeling Mobility Pulp

Question 40

What causes pain?

Answer 40

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

Question 41

Immediate pain response

Answer 41

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

Question 42

Long term pain response

Answer 42

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

Question 43

Does root resorption continue after braces?

Answer 43

No

Question 44

Remodeling

Answer 44

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

Question 45

Positive response to tooth movement

Answer 45

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

Question 46

Why is there an increase in mobility

Answer 46

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

Question 47

Pulp response to force?

Answer 47

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

Question 48

Moving endo treated teeth

Answer 48

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