Principles of Tooth Prep

Question 1

What are the 5 principles of tooth prep and restoration design?

Answer 1

1) Preservation of tooth structure
2) Retention and resistance form
3) Structural durability of the restoration
4) Marginal integrity
5) Preservation of the periodontium

Question 2

•Trauma from tooth preparation•Decreased thickness of dentin protection•Remaining dentin thickness (between prepared walls and pulp) key to its protective nature→Hypersensitivity→Pulpal inflammation and necrosis

Answer 2

•Pulpal Insult

Question 3

•A guide as to how much tooth structure can be removed w/o harming the pulp•Pulp + 1mm minimum surrounding dentin•Retentive features cut no deeper than 1.5mm (axial) -2mm (central fossa)

Answer 3

•Vital core

Question 4

: reinforcement and protection of remaining tooth structure

Answer 4

•Cuspal Coverage

Question 5

•Preserves the basic primary axial and occlusal tooth anatomy within the preparation.•Maximal thickness of residual tooth structure surrounding the pulp is retained.

Answer 5

•Morphologic reduction:

Question 6

•Preparations must be designed to resist dislodging forces.

Answer 6

Resistance and retention form

Question 7

•The ______ form of the preparation is the most important of the factors under operator control which will determine if a restoration will remain cemented in place.

Answer 7

geometric

Question 8

Prevents removal along path of insertion•Occurs with sticky foods •(least common problem)•Provided for by: •Two opposing vertical surfaces with minimal convergence

Answer 8

Retention form

Question 9

_______ hold through the mechanical interlocking of projections of cement into irregularities of the surfaces being joined.Weakest -tension Strongest –compression

Answer 9

Dental Cements

Question 10

•Prevents restoration dislodgement by apical or oblique forces.•Occlusal forces•Resistance to lateral forces, and not retention along the path of placement, is the greatest determining factor in a crown’s resistance to dislodgement.

Answer 10

Resistance form

Question 11

• Resistance form is built into a preparation by forming walls to block anticipated movement due to:
• Leverage
• Rotation around a vertical or horizontal axis

Answer 11

Resistance form

Question 12

What are the 5 factors affecting resistance form?

Answer 12

1. Total Occlusal Convergence ( Taper)
2. Preparation Wall Length(OC or IC Dimension)
3. Tooth Width (FL Dimension) -(Ratio of wall length : tooth width)
4. Geometric Form (Limited Path of Insertion)i. Grooves, boxes, vertical planes, pinsa. (Supplemental / internal prep features)ii. Morphologic reduction / pyramidal shape of prep
5. Surface Area

Question 13

:relationship of one wall of a preparation to the long axis of the preparation

Answer 13

Inclination

Question 14

:the relationship of taper between two opposing walls of a preparation.

Answer 14

Angle of convergence or total occlusal convergence

Question 15

What is the ideal TOC?

Answer 15

6 degrees

Question 16

At what TOC is there maximum retention?

Answer 16

5 degrees

Question 17

•For every 5 degree increase in the total convergence angle, the retention and resistance form may decrease up to _____%.

Answer 17

50%

Question 18

•Molar tooth preps have ______ TOC than premolars and anterior preps.

Answer 18

greater

Question 19

Mandibular tooth preps have ______ TOC than max tooth preps

Answer 19

greater

Question 20

posterior preparations generally require _____ TOC than anterior preparations.

Answer 20

less

Question 21

What is the clinically acceptable TOC?

Answer 21

10-20 degrees

Question 22

The greater the height of a prep the _____ the retention of the prep

Answer 22

Greater

Question 23

Wall length (height of the preparation) should be _____ than the tipping arc of displacement, to prevent displacement of the restoration.

Answer 23

greater

Question 24

T/F: The preparation with longer walls (a) interferes with the tipping displacement of the restoration better than the short preparation (b).”

Answer 24

True

Question 25

For every 1 mm increase in preparation length, the retention and resistance form increases up to____.

Answer 25

10%

Question 26

The shorter the preparation the ____ the taper must be.

Answer 26

less

Question 27

The longer the preparation, the ______ the taper maybe.

Answer 27

greater

Question 28

A narrow (smaller diameter) tooth can have _____ resistance than a wider (larger diameter) tooth with same wall length

Answer 28

greater

Question 29

For adequate R&R form, the height:baseratio should be greater than ______ for all teeth

Answer 29

0.4

Question 30

What is the minimum height for incisors and premolars?

Answer 30

3 mm

Question 31

What is the minimum height for molars?

Answer 31

4 mm

Question 32

What are 3 examples of 2o Auxiliary Retentive Features limits the paths of withdrawal to ONE

Answer 32

Boxes, grooves, and pin holes

Question 33

________ preparations have increased resistance form (morphologic reduction).•Preserve facio-proximal and linguo-proximal corners (line angles)

Answer 33

Pyramidal

Question 34

The ______ the surface area, the greater the retention

Answer 34

greater

Question 35

T/F; Reducing the TOC from 20°to 8°in the cervical 2 mm of the axial walls significantly increased the resistance form.

Answer 35

True

Question 36

• Casting must be rigid enough not to flex.
• Sufficient tooth structure must be removed to create space for an adequate bulk of restorative material without over-contouring the restoration.

Answer 36

Structural durability of the restoration

Question 37

What are the 3 prep features that contribute to structurability?

Answer 37

1. Occlusal / Incisal Reduction
2. Functional Cusp Bevel
3. Axial Reduction

Question 38

_________ provides:
•Adequate occlusal/incisal clearance without excessive removal of tooth structure.
•Uniform restoration thickness
•Parallels the major planes of the tooth (not flat)

Answer 38

•Morphologic Occlusal Reduction

Question 39

__________ Reduction:
•Allows for adequate thickness of restorative material
•without undue sacrifice of tooth structure
•without over-convergence

Answer 39

•Morphologic Functional Cusp Bevel

Question 40

_______: creates space for an adequate bulk of metal within the normal axial contours of the tooth.

Answer 40

Axial Reduction

Question 41

Requirements for successful restoration margins:

1. Fit as closely as possible to minimize cement film width (25μ)
2. Sufficient strength to withstand forces of mastication (geometry of prep)
3. Located where dentist can finish and inspect, and patient can clean

Answer 41

Marginal integrity

Question 42

•The margin should fit as closely as possible to minimize cement film width_____ μ

Answer 42

(25 μ)