Basics of Tooth Preparation

Question 1

When preparing a tooth, you must balance what three qualities?

Answer 1

1. Biologic
2. Mechanical
3. Esthetic

Question 2

Why is the amount of reduction an esthetic consideration for metal-ceramic crowns?

Answer 2

If there is an insufficient reduction, there will be a reduced porcelain thickness that leads to gray, unappealing color change

Question 3

What are “biologic considerations” during tooth preparation?

Answer 3

1. Prevention of damage (adjacent tooth, pulp, soft tissue)
2. Conservation of tooth structure (follow anatomy)
3. Marginal Integrity

Question 4

To protect the pulp, use _____ or ______ as a _______.

Answer 4

Air or Water

Coolant

Question 5

Conservation of tooth structure can be achieved by following the anatomy of the tooth, by maintaining the biological width, and by selecting the appropriate ________.

Answer 5

Margin Design

Question 6

Whenever possible, the margin of the preparation should be ______.

Answer 6

Supragingival

Question 7

What are two methods that may be used to check for proper margin adaptation?

Answer 7

1. Pig-Tail Explorer (intra oral)

2. Radiograph Evaluation (extra oral)

Question 8

Of the three designs for axial walls, which two are inappropriate for crown preparation?

Answer 8

Parallel and Divergent

want CONvergent

Question 9

Why are parallel wells inappropriate for crown preparation?

Answer 9

Parallel walls create friction that makes seating the crown nearly impossible

Question 10

The total convergence angle of a crown prep should be ____ degrees.

Answer 10

6 (each side with a 3 degree taper)

Question 11

Which bur should be used during the occlusal reduction?

Answer 11

242.6M

Question 12

Which bur should be used when creating axial walls for an MCC prep?

Answer 12

The shoulder (facially) should be created with a 702.8 bur
The chamfer (lingually) should be created by a 242.6 bur

Question 13

Molars and premolars have different POWs. When choosing a POW with which to relate the bridge, the molar is preferred over the premolar. Why?

Answer 13

The premolar POW will cause the bridge too look very buccally oriented.
The molar POW will cause the premolar to be slightly over-reduced at the HOC….this is the lesser of two evils

Question 14

True or False: The first planes of the abutment teeth should be parallel to each other and to the long axis of the molar.

Answer 14

True

Question 15

For good esthetics, what should the occlusal reduction measure on the facial cusp of an MCC prep?

Answer 15

1.5 mm

Question 16

For an MCC prep, how wide is the shoulder?

Answer 16

1.2 mm (use 702 bur)

Question 17

During placement of axial guide grooves for an MCC prep, the finish line is originally placed 0.75mm supragingival. What is the final location of the shoulder and what is its angulation? What tool is used during this step?

Answer 17

120 degrees
0.5mm
Hatchet

Question 18

What is the problem with a flat occlusal surface?

Under-reduction or Over-reduction

Answer 18

Under-reduction: insufficient space for materials

Over-reduction: Pulp exposure or poor resistance form

Question 19

For an MCC prep, the finish line design is a _______ with a width of _______ and at a ______ degree angle.

Answer 19

Shoulder
1.2-1.5mm
120

Question 20

True or False: As long as the abutments have common/parallel paths of withdrawal, the bridge will seat properly.

Answer 20

FALSE: The surrounding teeth need to also be considered. The common angulation may not coincide with teeth surrounding the abutments.

Question 21

The quality of a preparation that prevents the restoration from being dislodged by forces parallel to the POW is known as _______ form.

Answer 21

Retention

Question 22

Which mechanical quality is influenced by degree of taper?

Answer 22

Retention form (best retention if 3-5 degrees)

Question 23

What is resistance form?

Answer 23

Quality of the preparation that will resist lateral forces which tend to displace the restoration in an oblique direction

Question 24

Which mechanical quality protects a restoration from dis-lodgement during occlusal movements/forces?

Answer 24

Resistance Form

Question 25

Why is a “rough finish line” considered unacceptable?

Answer 25

Causes potential marginal leakage

Question 26

At contact points, metal is the material of choice unless ______ is a concern due to visibility.

Answer 26

Esthetics

Question 27

Which are more visible: mandibular or maxillary posterior teeth?

Answer 27

Maxillary are more visible

Question 28

If contacts are visible upon smiling, the shoulder should be extended how far beyond the point of contact?

Answer 28

1 mm lingual to the contact

Question 29

True or False: With supragingival margins, impressions are more easily made with less potential for soft tissue damage.

Answer 29

True

Question 30

Spragingival margins allow margins to be more easily _____ and _______.

Answer 30

Finished

Cleansed

Question 31

“Root sensitivity” would be an indication for what type of margin?

Answer 31

Subgingival

Question 32

Presence of caries, presence of cervical lesions, or need for additional retention are all indications for _______ margins.

Answer 32

SUBgingival

Question 33

Amelogenesis imperfecta would require that the margins be _______ to add additional support and increase esthetics.

Answer 33

subgingival

Question 34

What type of margin would be indicated by a “gummy smile”?

Answer 34

Subgingival margin due to high smile line