Operative, 11/29/11

Front 1

Dimensionally stable impression means?

Back 1

Once its removed from the mouth it should not lose its shape. Final impression materials include PVS, but this is not dimensionally stable. You must pour this up in 30 min.
-advantage of a dimensionally stable material is that it doens't need to be puored up immeidately.

Polyethers are also very dimensionally stable. What happens if there's a bubble on the margin? Impression is not good for pouring up the model.

Front 2

What do you look for in the internal surface of the impression?

Back 2

1. read the margins and a little bit of impression material beyond the margin. easily readable finish line.
-helps you identify it easier
-gives lab technician an idea of the confluence beyond the finish line.
-if there's a buble on the margin, you hsould start over again.

Front 3

Tissue management

Back 3

aka tissue retraction or sulcular enlargement.
-at times you need to go subgingival and get the tissue out of the way.

Front 4

Retraction...

Back 4

1. Can cut the gingiva cut of the way or get it to shrink. Scalpel blade, laser, or burning it away (electrosurge). Can reversibly shrink the gingiva.

As tissue shrinks, it does so in 3 directions.
1. vertical displacement (shrinkage apically)
2. lateral displacement (away from the tooth)
3. fully recoverable - esp important in the aesthetic zone. must go back to its original position.
4. hemostasis
Number 1 culprit of getting a poor impression is bleeding.

Front 5

How do you remove the tissue?

Back 5

1. scalpel
2. electrosurgery
3. laser ablation - hard to get it backto what it originaly looked like.
4. rotary curettage
5. retraction cord ** more commonly used.
6. retraction putties**

Front 6

Electrosurgery

Back 6

Can do sig damage if not used carefully. Require a lot of owrk on your part to make sure you do it properly.

Front 7

Retraction cords

Back 7

also requires practice.
-simple cotton cord that is impregnated with dried vascoconstrictor and is reconstituted when it becomes wet (placed into a living sulcus).
-if done properly, it iwll fully recover.

Front 8

Types of cords

Back 8

1. untreated (why?): if you want to treat it chair side
2. treated chair side -
3. epinephrine treated
4. aluminum sulfate treated
#3 and 4 works almost exactly the same. epi cord can be a problem with certain pts. Most of us don't use epi, we use aluminum sulfate that is safer to use.
5. different diameters
6. braided or twisted - braided stays in sulcus better than the twisted ones.

Front 9

Cord packer

Back 9

Use one with a relatively smooth end. Keeps the cord in place a little bit better. They also have the serrated ends, both work and you'll just need practice with each one.

Front 10

Does packing cord regardless of the state of pulp require anesthesia?

Back 10

Yes, usually anesthetize it wherever you need it both B and L to the tooth you are working on.

Front 11

Where must you be most careful when packing the cord?

Back 11

Interproximally is often where tissue is most inflamed. Typically done on second appt.
Tease it interproximally. Push the instrument a little back towards where you place it.

Front 12

Techniques used in the cord system?

Back 12

1. no cord (very subgingival)
2. one cord , left in place.
3. one cord, removed
4. two cords, one stays

#2 and 3 are the poorest options. #2 will allow you to place cord in sulcus but the free gingiva that's left still flaps over.
#3 - removed just before you take final impression. little bit of bleeding sticsk to cord and pulling it out will encourage more bleeding.

#4 - most often used. two cords i. first is small cord and second slightly wider diamter cord is placed on top of that. just before the impression, the superficial cord is removed. second cord on tip of the first, the larger superficial cord is removed.

Front 13

First cord?

Back 13

For a crown, goes 360 degrees around tooth with nothing sticking out.
-small and treated (epi???)
- when?
- no tail - nothing is sticking out. its completely buried.
-time and dryness (cotton roll) - best tissue shrinkage takes 7 to 8 min to occur. can't place a rubber dam when you use a retraction cord. want a little bit of moisture but not a ton.

Front 14

Second cord?

Back 14

larger diamter and place it with a tail. tail small piece of cord that extends into the facial, but not lingual. This is only a few mm long.
Pulls it out easily when you have a tail. This one doesn't get buried.

Front 15

Tray syringe technique

Back 15

Most popular (heavy body + light body technique).
-low viscosity material is injected into retracted shrunken sulcus. Low viscosity material is syringed around the tooth. Heavy material pushes the low viscosity material into the mouth. Tray pushes medium body that pushes the light body to get very good adaptation.

Front 16

Impression tray options

Back 16

1. custom tray (triad) - only use a teaspoon of impression material.
2. stock tray - acceptable most of the time.
3. full arch
4. quadrant
5. 2/3 trays
6. triple trays

Front 17

Where should crown and bridge tray extend?

Back 17

Only a few mm beyond the crest of the gingiva but not way into the sulcus. Buccal and lingual parts should go slightly beyond.

Front 18

Quandrant trays vs. 2/3s tray vs. full arch?

Back 18

Central incisor to the most distal tooth.
Value of full arch tray: stays in place much better. 4 points of contact for full arch. Model is easier to articulate. Because of that, full arch impression is a good idea.
bad reasons for full arch: more uncomfortable for pts, difficult to remove. Also, more expensive.
Quadrant - not as expensive, easy to remove fro mouth
bad: not as easy to articulate by lab technician, not as stable.

2/3s tray: starts as full arch and chop off posterior teeth on one side. All of posterior on one side and both canines. Becaomes a 3 legged chair, and easy for lab to articulate. Lab can check incisal guidance on both sides.

Front 19

Perforations?

Back 19

Locks the impression material in the tray when its removed from the mouth.
-allows mechnical lock of tray impression material. Works in conjunction with tray adhesion + macromechanical retention.
-more perforations you have, the less compression you have.
-holes make impressio material dribble down pts throat
+way to solve this is to take masking tape and put it on outside of impression tray. Has enough holes on inside to hold mechanical locks.

if tray is uncomfrtable for pt
-pts will squirm when material sets. theres possibility of tray moving in pts mouth. can't remove it too early or else it'll be distored and you'll have to start over again.

Front 20

Adhesives

Back 20

Specific for each impresion material. Adhesion and perforation works together to minimize separation of set material and the tray.

Polyether - most adhesive after it dries for 90 sec. that's the min amt of time required. for some types, its longer.