posterior ceramic crown preparation

i sit more common to do monolithic or laminated crown

monolithic

flexural strength of lithium disilicate

500 MPa

flexural strength of zirconia

550-1200 MPa

which uses only bonding cement

• lithium disilicate

• zirconia

lithium disilicate

white uses luting/bonding cement

• lithium disilicate

• zirconia

zirconia

what is luting cematation

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

• replies on the mechanical retention and resistance form

what is bonding cementation

• chemical adhesion between the tooth the restoration

• improve retention of the restoration

what determines whether you want to use a luting vs bonding cementation

• type and quality of tooth structure

• anticipated location of the finish lines

• size of pre-existing restorations

tooth preparation dimensions of a monolithic lithium disilicate restoration

• funx cusp: 1.5 mm

• non-funx cusp: 1.5 mm

• funx cusp bevel: 1.5 mm

• central groove: 1.5 mm

• axial wall: 1-1.5 mm

• cervical finish line: 1 mm

axial wall heigh of anterior teeth and premolars for luting cement

> 3 mm

axial wall height of posterior teeth for luting cement

> 4 mm

full coverage posterior crown prep using adhesive cemen vs prep using conventional cement

“new” adhesive cementation preparation can have slightly more conservative reduction but still mosth require the same axial height

axial wall height required for bonding cement

minimum is 2 mm but the taller the better (>2 mm); can only do IF YOUR TECHNIQUE/TAPER AND PRESERVE AS MUCH ENAMEL AS POSSIBLE

2 types of finish line design

• chamfer

• rounded shoulder

which bur would you use for which finish line desig

• KR is more flat; cavosurface angle is 90 → rounded shoulder

• 6856: cavosurface angle is ~110mdegrees → chamfer

which finish line design requires less reduction given the same thickness of margin

chamfer

which finish line has a better internal adaptation

chamfer (but no affect on clinical success rate); p= 0.02

which finish line has better marginal adaptation

rounded shoulder (but no affect on clinical success rate); p< 0.01

which finish line do you have more conservative reductioin

chamfer

acceptabel finish lines

• heavy chamfer 1 mm

• modified shoulder 1 mm

unacceptable finish lines

• beveled shoulder

• chamfer .5

• feather

• shoulder 1 mm

• lipped

mean marginal gaps; excellent prep _________ fair prep __________ poor prep __________

• excellent prep: 38.5 microns

• fair prep: 58.3 microns

• poor prep: 90.1 microns

the preparation quality has a significant impact on __________ on CAD/CAM crowns

marginal gap

finish line requirements

• even finish line width

• distinct, smooth and continue

• >0.6 mm clearance w adjacents

what is 3Y-TZP and what are its properties

• yttria-stabalized tetragonal zirconia polycrystal

• first generation zirconia

• very opaque

• strongest material of all zirconia

clinical indications for 3Y-TZP

• crown copings

• bridge frameworks

• implant abutments

talk about the coefficient of thermal expansion under compression vs tension

good compression, poor tension

translucency parameters of enamel vs dentin vs 3Y-TZP

• enamel: 18.7 tp

• dentin: 16.4 to

• 3Y-TZP: < 11.2 tp (v opaque)

3Y-TZP → 5Y-TZP what happens to the properties (midterm q!!)

• phase of tetragonal dec and will transform to cubic phase to become more translucent

• trade off is dec strength

what is 5Y-TZP and what are its properties

• 5 ytrria-stabalized tetragonal zirconia polycrystal

• second generation (maybe third??)

• inc volume of yttrium

• inc the cubic phase > tetragonal

• more translucent →

• little less strength

clinical indications for 5Y-TZP

• monolithic veneers

• monolithic anterior crown

5Y-TZP has the same translucency and strength as what other material

lithium disilicate

between 5Y-TZP and lithium disilicate which has better bonding properties

lithium disilicate; bc can be etched → better bonding

properties of 4Y-TZP

• stronger than 3Y

• 700-800 MPa

• little more translucent than 3Y

• better for posterior crowns

• what is used more in labs now

clinical indication for 4Y-TZP

• monolithic crowns

• monolithic short-span bridges

how translucency and strength changes between 3Y- 4Y amd 5Y-TZP

inc translucency but dec strength

rank these origin sof fx from most common cause to least of fx of monolithic zirocnia

1. intaglio occlusal

2. cervical

3. non-fx

rank the amount of occlusal reduction required from least to most of 3Y- 4Y- and 5Y-TZP

3Y < 4Y < 5Y

(more translucent material → more occlusal reduction)

ideal vs reality of total occlusal convergence

• ideal: 6 degrees

• reality: 18-23 degrees

fx resistance of monolithic zirconia crowns w different total occlusal convergence of 10 vs 15 vs 30 degree

1. 15 degree

2. 10 degree

3. 30 degree

taper affects __________ and __________

retention and strength of retoration (more taper → less retention/strength)

what is the poisson effect

when you reduce enamel → your prep is getting more tapered → more dentin exposed → dentin is more flexible than enamel → occlusal force under no enamel and hard material over dentin → force will go to cervical area bc this is the weak point → cervical crack propagation

crack propagation in the cervical area is related to…

taper and margin thickness

for our prep in school what total oclcusal convergence are we aiming for

10-15 degrees

3Y-TZP finish line design

light chamfer .5 mm

4Y-TZP finish line design

.8 mm

5Y-TZP finish line design

heavy chamfer margin

how finish line design is different as you go from 3Y- 4Y- to 5Y-TZP

will inc

from them group, which group will cause more wear

• polished zirconia

• glazed zirconia

• polish/glazed zirconia

• feldspathic porcelain

• enamel

porcelain/PFM

how surface roughness affects tooth wear

the more rough → the more wear it will cause on the opposing tooth (smooth/polish rather than glazed)

zirconia crowns led to ___ (less/more) wear of antagonist enamel then metal ceramic crown, but _____ (less/more) than natural teeth

zirconia crowns led to less wear of antagonist enamel then metal ceramic crown, but more than natural teeth