Day 3 lecture 1

Question 1

Axial wall

Answer 1

Concave/convex according to shape of original tooth.

Question 2

Depth

Answer 2

1- Total depth of the cavity preparation 2- Maintain uniform depth in dentin 3- 0.5mm into dentin

Question 3

Enamel rods anatomy

Answer 3

Head, tail, interrod enamel

Question 4

Amalgam margin

Answer 4

Amalgam carved too deep results in acute angles a and b and stress concentrations within the amalgam, potential for fracture.

Amalgam carved with appropriate anatomy, results in an amalgam margin close to 90, although the enamel cavosurface margin is obtuse.

Question 5

oblique ridge

Answer 5

maxillary molars

Question 6

Mandibular first premolar

Answer 6

DO NOT extend into transverse ridge of mandibular 1st premolar unless it is undermined by caries (class 1)

Question 7

Conservation of tooth structure

Answer 7

Cavity outline should extend around the cusps (conservative approach)
• Shape: Flowing curves around triangular ridges
• Isthmus Width: should not exceed 1/3 intercuspal distance

-preferable 1/4 intercupal distance.

Question 8

Long axis

Answer 8

midline axis of tooth

Question 9

Central pit

Answer 9

Bottom of cusp valley

Question 10

Peripheral 1/3

Answer 10

enamel rods pointed away from long axis

Question 11

Middle 1/3

Answer 11

enamel rods pointed parallel to long axis

Question 12

Central 1/3

Answer 12

Enamel rods pointed toward long axis.

Question 13

Outline form

Answer 13

• Include all major pits and fissures
• Placing the margins (cavosurface margin) on sound strong tooth structure
• Extend around the cusp for conservation of tooth structure
• Minimal extension of the buccal and lingual walls….minimal extension into triangular ridges (from the central groove to the cusp tip)
• Minimal extension into the marginal ridges (include the mesial and distal pits and partially include the fossa groove)
• Depth of the cavity preparation should be 0.2- 0.5 mm into dentin/1.5- 2.0mm on ivorine teeth

Question 14

Class 1 buccal and occlusal wall

Answer 14

The 2 opposing walls converge occlusally
• This occlusal convergence of the 2 opposing
walls provide the primary retention form
• The walls take the shape of the 330 bur
• Keep the bur angulation with the long axis of the tooth
• Don’t overconverge by tilting the bur … undermined enamel.

Question 15

Class 1 other walls

Answer 15

Walls diverge around the remaining developmental (primary) grooves if any:
•
To follow the direction of the enamel prisms. Enamel prisms tend to diverge further from central groove

Question 16

Buccolingual extension

Answer 16

Minimal extension of the buccal and lingual walls … minimal extension
from the central groove to the cusp tip (conservation of triagular ridges)
• Isthmus B-L dimension should not exceed 1/3 intercuspal distance
• Isthmus area is usually narrower than at the dovetail

Question 17

Class 1 mesial and distal walls

Answer 17

Diverge the mesial and distal walls slightly toward the occlusal to follow the direction of the enamel rods without involving the marginal ridge (Conserve the marginal ridge)

Question 18

Class 1 Mesiodistal extension

Answer 18

1.6 mm of tooth structure should be left between cavosurface margin and the proximal contact area (conservation of marginal ridge)
• If cavosurface margin is past the crest of the marginal ridge then you are too far extended

Question 19

Class 1 pulpal floor

Answer 19

• Flat and Smooth
• Perpendicular to the long axis of the tooth
Smooth: no irregularities, minimizes stress concentrations
Flat: don’t slope pulpal floor except for man 1st premolar
You want forces to be perpendicular

Question 20

Pulpal Depth

Answer 20

Adequate depth: resistance form
• Clinical depth is 0.2-0.5 mm beyond dentinoenamel junction (DEJ) • Typodont
From cavosurface margin to the pulpal floor = 1.5mm at the fossa 1.75-2.0mm at the ridges

Question 21

Class 1 cavosurface margin

Answer 21

Flowing smooth curves. 90/100 degrees

Not sharp …no irregularities

Question 22

Axial walls class V

Answer 22

Convex - follows external surface of tooth, uniform dentinal depth (0.5mm). This depth protects the pulp chamber sufficiently. If you are not convex, you increase axial depth, getting too close to the pulp.

Question 23

Base material

Answer 23

Replaces dentin- used to protect pulp following depper preps.

Question 24

Why class Vs are only 1 mm deep

Answer 24

not an occlusal surface - not a constant, direct force. 1 mm amalgam prep is sufficient due to this.

Question 25

Retention grooves

Answer 25

Class V does not have built in retention, so we put in retention grooves.

Question 26

Simple, compound, complex

Answer 26

1 surface, 2 surfaces, many surfaces.

Question 27

Perio probe

Answer 27

Must not be used in preps against the walls - this is wall length not axial length.

Question 28

Occlusal enamel rods

Answer 28

Tapered way too much if 90 degree margin with enamel is met. Instead you go about half way between the 90 deg. cut and a perpendicular cut. If you do this, you can still get 80-90 degree amalgam margin (not great, but not terrible). If amalgam has too acute of angles at the margin, you will have too much force on the edges.

Question 29

Undermined enamel

Answer 29

Underlying enamel does not have dentin at the root

Question 30

Intercuspal distance

Answer 30

Distance between cusp tips of buccal and labial. Buccal lingual width should not exceed 1/3 of this distance (preferably 1/4 of distance).

Question 31

Ball gage, condensor

Answer 31

1 mm smallest end - can be used to measure isthmus area.

Question 32

Marginal ridge

Answer 32

Cannot approach crest during prep. Keep 1.6 mm from mesial cavosurface margin to marginal ridge contact point (2x diameter 248, 330 burs). This is resistance form.

Question 33

Class I sloped pulpal floor

Answer 33

Mandibular 1rst premolar.

Question 34

Pulpal depth

Answer 34

1.5 mm at pit areas. Much more at triangular pit areas (2-2.25 mm).

Question 35

Grooves

Answer 35

Go 1/3rd to 1/2 length of your grooves. Drill from pit to pit (look for the big fossa). 1 mm in width (use smallest condenser when restoring, it has to fit).

Question 36

Entry w/330 bur

Answer 36

Distal to mesial - enter along long axis of tooth, depth is 1.3 mm.