May 17, 2016 Flashcards by Tedman McMahon

How much total occlusal convergence do you need for retention and resistance form in the preparation?

6-8 degree, in both directions

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True or False? Resistance form and retention form can be completely separated from each other.

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How much should the margin be reduced?

0.5 mm

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How much should the non-functional cusp be reduced

1 mm

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How much should the functional cusp and functional cusp bevel be reduced?

1.5

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True or False? Buccal cusp is the functional cusp for #30.

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Explain the curvature of the CEJ

more gingival in the buccal and lingual areas

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Starting point for the finish line:

1 mm above the CEJ

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6 preparation steps for full coverage restoration:

occlusal 2. B and L 3 inter proximal 4 finalize the axial walls, 5 finish 6 evaluate

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What should follow the adjacent teeth after preparation?

central groove and tip of the B cusp

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What bur to use for cutting guiding grooves

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What do you use to cut the depth groove

depth cutting burs (WDL1.0)

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If you need a 1mm reduction, what size bur should you use for the guiding groove and why?

0.8, so that when you are finishing you do not over reduce

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Where do you place the guiding grooves?

no specific location

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What should you leave in tact when prepping the tooth and why?

marginal ridge, so you don’t cut the adjacent tooth

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Where does the functional cusp start?

5mm above the CEJ, marked on the buccal surface of tooth

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How many mm of axial wall height from the finish line do we want?

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Angulation for cutting reduction grooves:

45 degrees to long axis of tooth OR follow the non-functional cusp of adjacent tooth

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True or False? We should get the DMR and MMR’s for our preparation.

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What bur to use for cutting guiding grooves on axial wall:

6878K-016, Champfer bur

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6878K-016, Champfer bur has what degree of angulation?

6-8 degrees, exactly what we want for our prep

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How should the 6878K-016, Champfer bur be angled when prepping the tooth?

parallel to the long axis, it is already angled to the exact angle we want, 6-8 degrees

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Depth of the grooves should be:

1/2 of the 6878K-016, Champfer bur

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What will happen if you enter more than half of the chamfer bur?

creation of unsupported enamel, prone to chipping

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Bur to break contacts:

850

Bur to finalize the occlusal table and axial wall:

finishing bur

axial wall height:

4mm

General shape of #30

rectangular, squarish with a rounded line angle

finish line is located:

0.5 mm occlusal to CEJ

categories of the principles of tooth preparation:

biologic, mechanical, and esthetic

Mechanical considerations for tooth preparation:

retention, resistnace, preventing deformation of the restoration (by not reducing enough)

define retention:

prevents removal of the restoration along the path of insertion or long axis of the tooth preparation:

What is important for retention:

parallelism of the axial wall ? Same angle of opposing walls?

Why do we need resistance form?

prevents dislodging during tipping forces; apiece, oblique, or occlusal forces

Factor that influences the retention of the restoration:

geometry of the tooth preparation

3 factors in geometry of the preparation:

diameter, height, and taper of the preparation

2 teeth, different diameters, which has better retention form?

larger diameter

True or False? When the diameters of 2 prepped teeth are the same, the increase in retention is less marked with an increase in height.

How does the preparation of the axial wall influence retention?

retention increases as the axial walls approach parallelism ( does this meant that closer to 6 degrees is better than 8?)

What preparations use the TOC?

single tooth crowns or fixed dental prostheses

Maximum TOC should not exceed:

20 degrees

Factor that influences resistance:

geometry of the tooth

What decreases the resistnace of the restoration?

taper or diameter increases OR the height of the preparation is reduced

Does a short tooth preparation with large diameters have a lot or little resistance form?

very little ( shorter, less

How do you shape the tooth preparation?

follow the shape of the actual tooth

What margin design do we mainly use in indirect?

chamfer, shoulder, modified shoulder

When is the chamfer margin formed?

for complet cast restorations

A chamfer margin is formed as what?

the negative image of a round-ended tapered diamond

What degree taper do diamond bur have?

6-8 degrees?

What part of the bur forms the axial wall base?

the side of the chamfer bur

What part of the bur forms the margin?

tip of chamfer

What is the second plane of buccal axial wall?

buccal cusp bevel

How deep to cut with the chamfer bur?

Half of the bur

How should the bur be angled when reducing the buccal and lingual axial walls?

in line with the long axis of the tooth

Should we use short or long strokes?

long

How to angle the bur when reducing the axial wallls 1mm above the CEJ:

follow anatomy of tooth

When opening the proximal contact the cutting motion should be from:

gingival to oclusal

True or False? when opening the proximal contact you should tilt your bur, following the long axis of the tooth.

F. This would create undercut or high TOC

Where to place the margin:

0.5mm above the CEJ

Direction of the bur when placing the margin:

follow long axis

How to remove marginal unsupported enamel:

endcutting bur or hatchet, also creates continuous, smooth margin

Evaluate the preparation for:

undercut, sharp edges, continuous margin, occlusal and axial reduction, TOC

What should you follow when reducing the occlusal surface:

the reduction guides and the occlusal anatomy

First step in tooth preparation:

occlusal reduction

What cusps are prepared?

non-functional, functional, and functional cusp bevel

What does the functional cusp bevel follow?

the functional cusp bevel of the adjacent tooth

What 'form' is the 3.5-4mm axial wall height required for?

resistance form

Axial wall height on buccal surface of molar is from

end of second functional cusp bevel to (most gingival portion of functional cusp bevel) to finish line

Axial wall height on lingual surface of molar is from

occlusal, axial line angle to the finish line

Start from here when defining the occlusal table:

the gingival portion/ line of the functional cusp bevel, follow marginal ridge of the mesial and then cusp tissues of the lingual, distal margin ridge and connect

What is the margin?

the outermost portion of the finish line

2 reasons to use compare software

independent feedback and assessment

Click this for independent feedback:

slice plane

What are we comparing our preparation against the standard for?

surface differences (5), finish line width, axial wall height

Which should be loaded first, sample or master

master

Master is aka:

standard

Can Compare recognize zipped files?

What colors are the standard preparation and your preparation

standard: gray, yours: beige

Over reduced area will show up as this color:

gray

In which planes can slice mode slice the scan?

B-L, M-D, and horizontal

in which plane is it easiest to evaluate the axial wall reduction?

horizontal plane

What needs to be defined in Compare Software

Margin, axial base and occlusal

How do you zoom in and out?

middle wheel on mouse

How do you rotate around the scan?

hold right click down

Easier tool to define the axial base:

'Trace' tool

True or False? The functional cusp bevel is not part of the 'occlusal' when scanning.

F. it is part of it

What is the 'set occlusal angle' similar to?

path of insertion, place preparation at the center of the yellow cylinder

Compute the difference under tolerance of __ microns

350 (0.35mm)

What does it mean if the "% comparison" is 100%?

match 100% with standard

How is the 'Finish Line width" labeled in Compare Software?

'Shoulder Width'

What is the tolerance for the finish line width for the complete cast crown?

200 microns (from 0.5mm) (0.2mm)

Tolerance of the axial wall height:

500 microns (from 4mm) (0.5mm)

What is the finish line called in Compare Software?

margin

2 options for defining the finish line:

'Trace finish line' and 'wand finish line'

Placement of cursor when defining finish line:

inside the finish line

What does the positioning of the axial wall base depend upon?

type of bur used, define the most internal portion

'set occlusal angle' is aka:

define path of insertion, center the tooth in the yellow cylinder, if you are off slightly it is not an issue

Finish line is from here to here:

Axial wall base to the margin (check)