Zirconia, Endo, Post & Core

Question 1

2024 Cesar Shang Recent Advances in Zirconia
1. What happens during zirconia sintering? What happens the longer you sinter?
2. What are some advantages of short sintering?
3. What are downsides?

Answer 1

1. Densification via reduction of the porosity and junction of the powder particles. Longer you sinter, the bigger the grain sizes.
2. One study found higher flexural strength (, shorter time
3. Reduced translucency due to isolated tiny pores (light scatter)

Question 2

What are heatless stones made out of?

Answer 2

Silicon carbide

Question 3

At what temps does zirconia exist in its different phases?

Answer 3

Below 1170˚C: Monoclinic
1170-2370˚C: Tetragonal
Above 2370˚C: Cubic

Question 4

How much vol % change when Zirconia changes phase from tetragonal to monoclinic?

Answer 4

5%

Question 5

Noble metals do not oxidize easily. What elements are added to alloys in order to facilitate the oxide layer formation for ceramic veneering?

What can cause some alloys to become green?

Answer 5

Easily oxidized elements, like indium and tin.

Green: Silver

Question 6

Per Sorensen and Engelman 1990, ferrule effect improve the structural integrity of the purples tooth by counteracting what three forces?

Answer 6

Counteracts

1. Functional lever forces
2. Wedging effect of tapered dowel
3. Lateral forces exerted during insertion of dowel

Question 7

What were Sorenson and Engelmann’s four conclusions?

Answer 7

1. 1 mm of coronal dentin above shoulder significanty increased the failure threshold
2. Coronal walls should be parallel for max resistance
3. Contrabevel design did not improve failure threshold
4. Axial width of tooth at crown margin didn’t improve fracture resistance

Question 8

Who originally published on the amalgam coronal-radicular technique?

Answer 8

Nayyar 1980

Question 9

What did Aquilano and Caplan find in regards to Endodontically treated teeth and survival rates?

Answer 9

Endodontically treated teeth not crowned after obturation were lost at a 6.0 times greater rate than teeth crowned after obturation

Question 10

Goodacre 1994 - Why no post in the anterior endo treated tooth?

Answer 10

We know that the purpose of posts is to retain the cores. The tooth had adequate tooth structure and ferrule to retain a crown if I just did a composite filling that I felt no need to prepare for a post. I thought that would further weaken the tooth and its longterm prognosis.

Sorenson and Martinoff 1985 - Posts decreased success of single crowns