Proffit

Question 1

Describe physiologic response of the PDL when a tooth undergoes heavy pressure for different time periods (just the seconds)

Answer 1

<1 second – PDL fluid incompresible, alveolar bone bends, piezoelectric signal generated

1-2 –PDL fluid expressed, tooth moves within PDL space

3-5 seconds – pdl fluid squeezed out, tissues compressed; immediate pain

Question 2

In orthodontic movement the goal is to produce tooth movement by ____ resorption and try to avoid _____ resorption

Answer 2

Frontal resorption; undermining resorption

Question 3

What is piezoelectric activity?

Answer 3

When crystalline materials deform due to an external force which then produces a flow of electric current as electrons are displaced from one crystal lattice to another.

Note– collagen crystals in the PDL can also be piezoelectric

Piezo electric signals have a quick decay rate and produce an equivalent signal in the opposite direction when force is released

Question 4

Does piezoelectric activity happen with orthodontics?

Answer 4

No! Does not occur with sustained forces

Question 5

What are the 3 stages of tooth movement?

Answer 5

1) Initial compression – alterations in blood flow associated with pressure in the PDL
2) Formation/release of chemical messengers
3) activation of osteoblasts and osteoclasts – resulting in alveolar bone remodeling

Question 6

What duration threshold is required for for orthodontic movement to occur?

Answer 6

4 hours! – this is what is needed to get increased levels of cAMP

Question 7

What is frontal resorption?

Answer 7

OSteoclasts appear within the compressed PDL and attack the lamina dura and remove bone

Osteoblasts form bone on the tension side and begin remodeling activity on the pressure side

*With heavy pressure when blood vessels are totally occluded a sterile necrosis occurs–> results in undermining resorption

Question 8

What is undermining resorption?

Answer 8

Due to forces that are too heavy and cause PDL to be avascular/necrose, osteoclasts attack bone immediately adjacent to the necrotic PDL – the attach is from the underside of the lamina dura so it is called UNDERMINING.

Takes up to 7-14 days for tooth movement undermining resorption

Only takes 2 days for tooth movement to start in frontal resorption

Goal is to avoid PDL necrosis!

Question 9

What is the simplest orthodontic movement? What force is needed for this movement

Answer 9

Tipping – should not exceed 50gm!!

Question 10

What is the optimum force for tipping?

Answer 10

35-60gm

Question 11

What is the optimum force for rotation?

Answer 11

Same as tipping , 35-60gm

Question 12

What is the optimum force for extrusion?

Answer 12

same as tipping 35-60gm

Question 13

What is the force required for translation?

Answer 13

70-120gm

Question 14

Notes for remembering forces of orthodontic movement:

Answer 14

It is very easy to be intrusive! only requires 10-20gm
Rotation, Extrusion, Tipping all the same – 35-60gm
Translation, moving locations is very hard - 70-120gm

Question 15

What is the force required for intrusion?

Answer 15

10-20gm

Question 16

Why are lighter forces required for intrusion?

Answer 16

Because the force is concentrated in a very small area at the `tooth apex

Question 17

What type of force produces the most efficient tooth movement?

Answer 17

Light continuous forces!!

Heavy continuous forces are bad
Heavy intermittent forces are less efficient than light continuous but are clinically acceptable.

Question 18

What drugs inhibit tooth movement?

Answer 18

Prostaglandin Inhibitors (NSAIDS, Steroids)
Bisphosphonates

Acetominophen is not a prostaglandin inhibitor!

Doxycycline has been shown to decrease osteoclast recruitment

Question 19

The anchorage value of a tooth (it’s resistance to movement) is a function of _______.

Answer 19

It’s root surface area or PDL area

Question 20

Few notes on Proffit

Answer 20

During and shortly after the movement teeth do have a wider PDL space and some degree of mobility.

Pain wise – if appropriate forces are used nothing should be felt immediately but may feel aching a few hours later. The aching can last 2-4 days. Should use tylenol to prevent any prostaglandin inhibition which could inhibit frontal resorption needed for tooth movement