CH 1 handbook

Question 1

what is a preparation

Answer 1

THe final shape (form of the tooth produced by instrumentation) to a restoration

Question 2

what is a complete veneer crown

Answer 2

An extracoronal preparation involving the entire clinical crown

Question 3

What is the Path of Withdrawal

Answer 3

The imaginary line along which a casting is moved when it is separated from its prep

Question 4

what should the path of withdrawal coinside with

Answer 4

with the tooth’s long axis

Question 5

what forms the tooths long axis

Answer 5

opposing axial surfaces in 3rd of the tooth

Question 6

what is an axial wall

Answer 6

The part of the crown preparation preparing in the long axis of the tooth

Question 7

what are the names for the axial walls

Answer 7

Buccal, lingual, mesial, or distag

Question 8

what is the Convergence angle

Answer 8

The angle or taper formed b diametrically opposed axial walls

Question 9

what is the chamfer

Answer 9

The cervical junction of the prepared axial wall and the unprepared portion of the strucutre

Question 10

where does the chamfer extend

Answer 10

Around the cervical portion of the tooth preparation

Question 11

what are the line angle

Answer 11

The lines formed by the junction of any two tooth surfaces

Question 12

what should the line angles be shaped like on a crown prep

Answer 12

Ground

Question 13

Where is the occlusoaxial line angle

Answer 13

The junction between the occlusal surface and an axial wall

Question 14

where is the cavo-surface line angle

Answer 14

The junction of the prepared and unprepared tooth strucutre

Question 15

what are depth orientation grooves

Answer 15

Placed on the surface of the tooth to provide a reference to determine when sufficient tooth strucutre has been reduced

Question 16

what is the functional cusp bevel

Answer 16

A wide bevel placed on the functional cusps

Question 17

what is the role of the functional cusp bevel

Answer 17

the thickness of the tooth strucutre removed when preparing this bevel ensure that correct contours of the final restoration can be re-established while providnig correct convergence and adequate thickness of retorative materials

Question 18

when is a crown prep seen as undercut

Answer 18

If a wax pattern cannot be withdrawn from its die without distorting

Question 19

what cuases a crown prep to be undercut

Answer 19

Depression in an axial wall (can be from a carious lesion)

Diametrically opposed axial wals that do not converge

Question 20

how to fix undercuts due to a depression in the axial

Answer 20

correct with base matterial

Question 21

how to fix undercuts due to divergent walls

Answer 21

further tooth reduction

Question 22

what is occlusal clearance

Answer 22

Distance between the occlusal surface of a prep and the occlusal surface of the opposing tooth

Question 23

How is occlusal clearance evaluated

Answer 23

During excusive jaw movements as wall as intercuspal position

Question 24

what is retention form

Answer 24

The characteristis of the tooth preparation which tends to resist the removal of a restoration allong the POW

Question 25

What is retention form

Answer 25

Prevents dislodgement of a seated restoration by forces directed in an apical or oblique direction
prevents dislodgement by occlusal forces

Question 26

advantages of CVC’s

Answer 26

High strength
Longevity
High restistance to displacement
Ability to modify axial contours and oclusion

Question 27

Disadvantages of CVCs

Answer 27

display metal
remove tooth substance
Vitality testing
Margin close to gingiva

Question 28

Indications for CVC

Answer 28

Extensive destruction by caries or trama
Endo treated teeth
Large existing restorations
Maximum retnetion needed (long span fixed partial denture abutment)
Recontouring of axial surfaces
Correction of malinclination
Correction of occlusal discrepancies
To provide contours suitable for a removal partial denture

Question 29

Contraindications for a CVC

Answer 29

when tooth can be adequately restored with a more conservative restoration

Question 30

why would exessive reduction of tooth will occure

Answer 30

If too much convergance
Prep does not follow the anatomy of the tooth
POW diverges from the long axis of the tooth
V. wide margin
Excessive Gingival extension of the preparation (no further cervication than retention form and restoration and defects dictate)

Question 31

where is a poteintial site of failure

Answer 31

the tooth restoration interface at the gingival margin

Question 32

why would a restoration fail at the gingival margin tooth restoration interface

Answer 32

Cement dissolution or roughness

Question 33

What would be a cause of inadequate marginal integrity

Answer 33

Chemfer is too narrow to provide sufficient bulk of restorative material without over contouring
The cavo surface line angle cannot be determined during laboratory procedures
Chamfer is rough or uneven
Prep is undercut causing distortion of the wax pattern

Question 34

Causes of Inadequate retention and resistance

Answer 34

Excessive convergence angle (greater than 10 degrees)
Inadequate height and surface area of the axial wals
Insufficient SA to resist tipping of restoration

Question 35

Recommended Bulk of prep

Answer 35

Functional cusp:1.5 (1.3-1.7)
central goove: 1mm (.8-1.2mm)
Non-functional cusp: 1mm (.8-1.2)
Chamber width: .5mm

Question 36

what is the occlusal convergence of the burs

Answer 36

3-4 degrees