Ceramics and Resins

Question 1

What are some properties of Sinfony re.:
Curing
Filler material + %
Resin matrix
Water uptake
Aesthetics
Wear resistance

Answer 1

• Light cured
• Mixture of aliphatic and cycloaliphatic monomers
• Micro-dispersed silica filler (50%w/w)
• Low water uptake (better durability)
• Excellent aesthetics
• Low wear resistance

Question 2

What are the indications and contraindications of Sinfony?

Answer 2

• Inlays/onlays
• Full coverage crown anteriorly
• Veneers
• CR fused to metal crowns
• Fibre reinforced bridges/retainers
• Implant borne prosthesis

Contraindications:

• Unsupported bridges
• Stress bearing areas (e.g. posterior region)
• Implant abutment or fixture interface

Question 3

How is Sinfony processed into a restoration?

Answer 3

1. Restoration constructed on die with layering technique (opaque, dentine, enamel composite)
2. Initial layers snap light cured using Visio-Alfa Unit
3. Final vacuum firing via Viso Beta Vario Unit + Light
4. Rocatec used to bond Sinfony to metal if necessary

Question 4

What are some advantages and disadvantages of indirect composites?

Answer 4

Adv:

• Superior aesthetics to alloy based
• Better durability/marginal stability than direct CR
• Less abrasive than ceramic
• Can be bonded to alloy subframes for RPD
• Easier chairside adjustemnt and polish compared to porcelain

Dis:

• Long term clinical performance unknown
• Loss of surface shine
• Marginal staining/plaque accumulation
• Higher immediate cost

Question 5

What effect does raising the silica content in silica based ceramics have? What is an example of a ceramic with high silica content?

Answer 5

• Increased asethetic properities (translucency, optical properties), but decreased physical properties (as causes ceramic to become more brittle as high crack propagation)
• Feldspathic has high silica content, thus must be backed by metal

Question 6

What effect does raising the filler content in silica based ceramics have?
What are some examples of filler reinforced ceramics?

Answer 6

• Increased physical properties (as fillers prevent crack propagation) but decreased aesthetic properties
• Leucite re-inforced ceramic
• Lithium disilicate ceramic

Question 7

T or F? Silica based ceramics can bond to tooth?

Answer 7

T

-Silica makes ceramic etchable, thus can be bonded to by resin cement

Question 8

What are some examples of non-silica based crowns? Can they bond to tooth structure?

Answer 8

• Zirconia, allumina
• Both classified as polycrystalline crowns
• Neither contain silica at all
• Can not be bonded to tooth structure as no silica makes it unetchable

Question 9

How do polycrystalline crowns deal prevent crack propagation?

Answer 9

-Boundaries between the crystals prevent cracks from propogating

Question 10

What are the aesthetic properties of zirconia?

Answer 10

• Not good: zirconia is opaque, generally used as substructure in place of metal as it provides better aesthetic properties in that sense
• Has shades but only one colour

Question 11

What are some advantages and disadvantages of dental ceramics?

Answer 11

ADv:

• Dimensionally stable
• Excellent aesthetics/colour matching, do not stain
• Excellent Biocompatibility
• High wear resistance

Limitations

• Can wear opposing tooth
• Complex fabrication technique
• High cost
• Low fracture resistance
• Poor stress absorption

Question 12

Why can zirconia not be used for veneers?

Answer 12

• Can not bond to tooth structure

- Poorer optical properties

Question 13

How should predominantly glass cermaics be treated prior to bonding?

Answer 13

• 10% HF acid for 1 minute
• Rinse and dry
• Apply silane for one minute
• Air dry

(Note: silane double bond bonds to resin; hydroxyl group bonds to ceramic)
(Note: you haven’t really done this because you generally use PBM’s, thus metal surface is being cemented to tooth. This method is used to directly bond ceramics to the tooth e.g. full contour zirconia crowns, PBZ’s)–>this is why silanation was not included in cement steps

Question 14

How should particle filled glass ceramics be treated prior to bonding?

Answer 14

Leucite:

• 5% HF for 1 minute
• Rinse and dry
• Silane for 1 minute
• Air dry

Lithium disilicate

• 5% HF acid for 20 seconds
• Rinse and dry
• Silane for 1 minute
• Air dry

(Note: you haven’t really done this because you generally use PBM’s, thus metal surface is being cemented to tooth. This method is used to directly bond ceramics to the tooth e.g. full contour zirconia crowns, PBZ’s)–>this is why silanation was not included in cement steps

Question 15

What is generally used to bond sinfony to tooth? What are the steps of doing so?

Answer 15

System: Rocatec system

Tooth preparation:

• Etch enamel and dentine
• Wash + dry
• Apply adhesive, 15 seconds light brushing
• Light cure for 20 seconds

Restoration surface preparation

1. Clean and dry surface
2. Sandblast Sinfony surface with 2.8bar pressure at 1cm for 15 seconds using Rocatec soft (used as Sinfony is highly susceptible to abrasion, for surfaces less susceptible use Rocatec Plus) at right angles
3. Apply silane primer and wait 5 minutes
4. Gently air dry, ensure nothing remains to be incorporated into the bonding layer which can weaken it
5. Apply resin cement to inlay/onlay surface as per manufacturer’s instruction and place into tooth
6. Wipe away excess cement and light cure 40 seconds per surface

Question 16

What is the mechanism of action of the system used to bond Sinfony to tooth?

Answer 16

• Rocatec particles consist of aluminium oxide coated with silicon dioxide (which is found in ceramic)
• When the particles impact the resin surface, the aluminium oxide particles rebound off, but the heat created causes some of the silicon dioxide coating to become impregnated into the resin surface (up to a depth of 15 micrometres)
• When silane is applied, the hydroxyl group bonds to the silicon dioxide left behind on the surface, while the carbon double bond bonds to the resin cement
• The resin cement is bonded to the tooth enamel via the classic etch, primer bond technique (although primer and bond are done with one step/Optibond acts as both primer and bond)

Notes for clarification:

• We do this process with Sinfony as despite the fact that it is resin it is completely set and thus stable. Consequently it will not react with anything, thus being unable to bond chemically with the resin cement (if it could still react it’d be taking up stain, etc.)
• Not used for ceramic as silanated ceramic can bond directly onto tooth

Question 17

What is the difference between Rocatec Plus and Rocatec soft?

Answer 17

Rocatec soft has smaller particles (30 micrometres) vs Rocatec Plus (110 micrometres)

Question 18

What is Optibond? How is it used?

Answer 18

-Primer and adhesive in one
-Apply to enamel and dentine
-Leave for 15 seconds
-Air dry 3 seconds
-Light cure 20 seconds
(Lecture 2 Aesthetic Bonded resins, module 3)

Question 19

Summary of information for preparation of crown restoration prior to cementation :

Gold
Sinfony 
Porcelain (feldspathic)
Zirconia
Alumina
PBM

Answer 19

• Gold and untreated indirect resins do not bond with tooth via the resin cement
• Sinfony (resin) can bond with tooth if treated by Rocatec system and silanated
• However would not do this for feldspathic/porcelain as can silane can bond it to the resin cement (via hydroxyl to porcelain and carbon double bonds to resin)–>porcelain is composed of silicate. Porcelain/ceramic is also etched so that both micromechanical and chemical adhesion is achieved
• This only applies if the ceramic is being bonded directly to tooth (e.g. feldspathic veneers), if PBM then the metal is being cemented to tooth
• Zirconia and alumina crowns also can not bond to tooth structure, as even though they are ceramics they don’t contain silicates, and thus can not be etched. As such they can also be treated with Rocatec to facilitate bonding
• Gold and PBM’s should be sandblasted before cementation to facilitate better adhesion

Question 20

What is the difference between feldspathic, porcelain, zirconia, alumina and ceramics

Answer 20

Feldspathic= porcelain which is not the same as (zirconia and alumina). However all are grouped under ceramics.

i.e: ceramics encompasses all the other terms/ all other terms are types of ceramics.

Feldspathic and porcelain are the same thing (important part to remember)

Zirconia and alumina are a different class of ceramic to porcelain/feldspathic as the former does not contain silica and are instead polycrystalline based

*Refer to next question if confusing and If still confused refer to lecture 1 Aesthetic resin bonded materials in FP first slide on page 3

Question 21

What types of ceramic are there?

Answer 21

Glass (contains silica):
-feldspathic/porcelain (contains high percentage of silica)

Reinforced glass

• Leucite reinforced (silica/feldspathic reinforced by leucite filler):
• Lithium Disilicate (Emax) (silica/feldspathic reinforced by filler):
• Glass infiltrated alumina

Glass free (polycrystalline based, contain no silica): 
Zirconium oxide (Emax)
Aluminia