Posterior Ceramic Crown Preparations

which dental ceramic has the lowest flexural strength

- glassy fieldspathic leucite

laminated ceramic restorations: anterior or posterior?

anterior

monolithic ceramic restorations: anterior or posteriors

posteriors

What is luting cementation? what does it rely on?

- little to no chemical adhesion between the tooth and the restoration

- rely on the mechanical retention and resistance form

what is bonding?

-chemical adhesion between the tooth and restoration

- improves retention of the restoration

what are things to consider when deciding between luting vs. bonding cementation

- type and quality of tooth structure

- anticipated location of the finish line

- size of pre-existing restorations

what type of cementation is used with lithium disilicate

bonding

what type of cementation is used with zirconia

- luting/bonding cement

what type of finish line requires less reduction given the same thickness of margin, chamfer or rounded shoulder?

chamfer

internal adaptation vs. marginal adaptation: Chamfer exhibited significantly better _________

internal adaptation

internal adaptation vs. marginal adaptation: Rounded shoulder exhibited significantly better __________

marginal adaptation

in dental ceramics, as strength goes up, translucency usually goes ____

down

Most modern dental ceramics are _______

crystal-based

common crystals of dental ceramics

-zirconia (strongest)

- lithium disilicate ( balance of strength and esthetics)

indications for lithium disilicate

-esthetic crowns (higher translucency)

-veneers

indications for zirconia

- posterior crowns

- bridges

what are laminated ceramics

- strong core (zirconia)

- porcelain layers on top

- risk of porcelain chipping

what are monolithic ceramics

- one solid material

- surface stained

- stronger/ fewer fractures

Tooth reduction for monolithic lithium disilicate

- occlusal: 1.5

- cusps: 1.5

- axial walls: 1-1.5

- finfish line: 1

axial wall height is good for ____

retention

axial wall height of anterior and premolars

> 3mm

axial wall height for posterior teeth

> 4mm

what type of ceramics can tolerate shorter axial walls

bonded ceramics (but 2 mm is still recommended)

what type of finish line is preferred for zirconia

chamfer

Key prep rules

- Smooth, continuous margins

- Even finish line width

- ≥0.6 mm clearance from adjacent teeth

Zirconia phases:

Monoclinic → weak

Tetragonal → strong (desired)

Cubic → translucent but weaker

Zirconia is doped with ______ to stabilize the tetragonal phase

yttria (Y₂O₃)

The preparation quality has a significant impact on _______ on CAD/CAM crowns

marginal gap

Clinical indications of 3y - TZP

- posterior crowns

- bridges

- implant abutments

3Y, 4Y, 5Y zirconia: highest strength

3y --> 4y --> 5Y

3Y, 4Y, 5Y zirconia: highest translucency

57 --> 4y --> 3y (lowest)

More yttria = ____ translucency = ____ strength

more

less

Clinical indications: 5y - tzp

- monolithic veneers

- monolithic anterior crowns

Clinical indications: 4y - tzp

- monolithic crowns

- monolithic short-span bridges

Occlusal reduction for zirconia

- 3Y zirconia:

- 4Y / 5Y zirconia:

Why?

- 3y : 1 mm

- 4y/5y: 1.5 mm

- Higher translucency zirconia fractures more easily

what is the ideal total occlusal convergence vs. reality

- ideal: 6 degrees (10-15)

- reality: 18-23

which type of zirconia can have a thinner finish line

- 3y (.5 mm) --> 5y (1.0 mm)

__________ is more wear friendly to opposing enamel than feldspathic porcelain

Polished zirconia

Zirconia crowns led to _____ wear of antagonist enamel than metal ceramic crown, but more than natural enamel

less