common procedural errors in tooth prep

Question 1

2 common errors in occlusal reduction:

Answer 1

1. angle too high - ‘volcano’
2. angle too low - ‘table top’

Question 2

As the buccal cusp is convex, how can you overcome this when performing occlusal reduction?

Answer 2

Level off the buccal cusp.

Question 3

If placing the first plane at too steep an angle, what does this create?

Answer 3

An area of undercut.

Question 4

If the first plane is placed at an angle similar to the second plane, what does this create?

Answer 4

An excessive taper as unnecessary tooth tissue has been removed. This reduces retention form.

Question 5

How would you manage undercut on molar teeth?

Answer 5

By removing the tooth structure overlying the area of undercut.
(may lead to overpreparation)

Question 6

How would cases of severe undercut be managed?

Answer 6

Using composite to block off the undercut.

Question 7

What are the consequences of under preparation?

Answer 7

1. leads to a bulky crown
2. overhanging margin
3. plaque stagnation
4. gingival inflammation

Question 8

How would we check sufficient axial reduction for a shoulder margin (1.2mm in diameter)?

Answer 8

The shoulder bur should sit in the preparation as it has a 1.2mm diameter.

Question 9

How would we check sufficient axial reduction for a chamfer margin (0.5mm in diameter)?

Answer 9

1/2 of the chamfer bur should sit palatally as its diameter is 1mm.

Question 10

What type of preparation is required for an All Ceramic Crown?

Answer 10

1mm deep chamfer margin
(create by approaching laterally to prevent creating a lip)

Question 11

In terms of leaving restorative material when creating margins for deep marginal elevation, when can this only been done?

Answer 11

Only for onlays and composite being left.