Flashcards in Midterm Deck (57):
What kind of bonding chemical bonding occurs between porcelain and zirconia?
Porcelain does however form chemical bonds with metals via the metal oxide layer
What kind of functional group is used in bonding chemistry for most dentistry?
What is the “mon” of all the “mer”s?
___ monomers connects the polymer to something different.
___ monomers, like bis-gma is what forms the polymer
In functional monomers one end is the methacrylate unit and the other performs a specific function (which joins organic to the inorganic). What does phosphate group bind to? What does silane bond to?
The ____ group is the basis for acidic monomers and self-etch adhesives
MDP is an ____. It bonds to ___
Two viscous cross linking monomers are ___ and ___. A cross-linking monomer to reduce viscosity is ____
What causes initiation in a self initiating monomer?
Tertiary amine in a base paste
BPO chemical initiation in a catalyst paste
Combination of the two pastes produces free radicals that attack the carbon double bonds
What are found in photo initiated monomers?
Camphorquinone or other photo-initiator absorbs blue light, then reacts with amine activator to form free radicals
These free radicals then attack carbon double bonds
Inhibitors such as ___ and ___ are found in the catalyst paste of self-cure resins to prevent spontaneous polymerization and provide working time
(Oxygen is also a powerful inhibitor as it reacts with the radicals to form peroxyl formulations)
The tertiary amine eliminates the need for ___ to initiate free radical formation in self cure resins
Where does the free radical come from in self cure resins?
What are some other photoinitiators that are like camphorquinone?
What kind of cure are adhesive cements, self adhesive cements, and esthetic cements?
Adhesive = self cure
Self adhesive = dual cure
Esthetic resin cement = either self or dual cure
True or false.. base paste can be used alone in a dual cure composite
Base paste can be used alone in light-cure mode or mixed with catalyst paste for dual cure mode
Incompatibility between bonding agents and dual cure composite resin formulations primarily occurs with ____ due to ____
Self etch adhesives
Can also occur with two-step etch and rinse adhesives when acidic amonomers are present in the un-polymerized oxygen inhibited layer
This can cause a problem with build-ups
The mechanism of failure of self etch adhesives and dual cure composite resin is due to two things which are...
1. Neutralization of the tertiary amine co-initiators by acidic monomers (pH <3)
2. H2O contamination of the adhesive/composite interface
Describe the H2O contamination mechanism of bonding agents with dual cure composites
During the time it takes for a complete cure in the deeper layers of the material, moisture from the dentin is osmotically pulled across the semi-permeable adhesive layer and into the uncurled composite resin at the interface.
How long should you acid etch for lithium disilicate, leucite ceramic, felspathic ceramic, and zirconia?
Lithium disilicate - 20s with 5% HF
Leucite ceramic - 60s with 5% HF
Feldspathic ceramic - 120 s with 9% HF
Zirconia - do not etch! Sand blast intaglio surface (AKA microetch)
Silane comes in two forms: ___ and ___ (acid activated)
Silane bonds to ___
Glassy ceramics (AKA vitreous ceramics)
When should you bond zirconia?
Resistance and retention form in inadequate
Restorative material is thin
The restoration is a FPD
Do not allow the indirect restoration to be disturbed during clean-up for full time of resin cement set. The only exception to theis is with ___
Adhesive resin cements
What are two ways to bond to zirconia?
APC protocol with MDP
What is tribochemical?
Related to lubrication by chemical means
Caused by rubbing together mechanically
Describe tribochemical silica coating
Air abrasion with silicon coated aluminum oxide particles
Leaves the SiO2 coating in zirconia so that it is receptive to silane treatment
Describe the APC protocol of bonding to zirconia
A - air partial abrasion
P - primer application
C - cement with dual cure or self cure composite resin cement
What are the two best types of cements to use for the APC protocol of zirconia bonding?
Adhesive or self-adhesive
True or false... esthetic resin cements are best to be used with vitreous ceramics instead of crystalline
True or false... self-adhesive resin cements are the least retentive of all resin cements and you should keep dentin moist during cementation
True or false... it is acceptable to use RMGI such as relyX luting plus to bond zirconia
Why should you place the MDP bond to zirconia before it is moved to the mouth?
Phospholipids in the saliva will bind to the zirconia and take up the places where MDP would bind to
True or false... silane is not as stable in the presence of an acidic phosphate monomer
Which type of zirconia bonding has poor late bond strength if subjected to hydrolysis however bonding is a more simple process
True or false... moist dentin bonding will help the strength of the bond. When did this idea occur?
Fourth generation (where bond strength peaked
What are MMPs?
Endogenous in dentin and throughout the body
Play an important role in tissue remodeling
Break down collagen and weakening of dentin bond
MMPs can be inhibited by....
(Apply CHX or BAC directly to dentin prior to bonding or incorporate into bonding agents)
True or false... phosphoric acid effectively cleans the contaminated surface of lithium disilicate and leucite glass
How do you decontaminate zirconia?
Apply primer and wait 5 minutes BEFORE TRYING IN RESTORATION
Phosphoric acid can only be to clean the zirconia once it has already been primed with MDP
What is ivoclean?
It can be used to decontaminate any ceramic surface in preparation for bonding
What is the facial reduction for veneers?
0.5mm - 0.7mm
Increase slightly towards incisal
What is the incisal reduction for maxillary or posterior?
How many cavosurface margins with enamel are needed for posterior veneers? What about anterior?
2 (at least opposing enamel mesial and distal)
Can veneers be placed over existing restorations?
Yes, if existing restorations are in excellent condition, small in size, not discolored
What is the purpose of the chamfer in the posterior veneer prep?
Gives more bulk of material near the cusp tip
Why are minor shade changes not an indication for veneers?
Because you can bleach teeth to achieve minor shade changes
What may happen in a no prep veneer?
It thickens the tooth which causes the lip to move the tooth back which then may lead to distalizing the condyle and impinge upon the retrodiscal tissue causing TMD issues
What thickeners of veneer is necessary per 1 shade change?
Although you want the margin to be 0.5 supragingival preclinically, where do you want it clinically?
Why should you prescribe chlorhexidine to pts with veneer temps?
They cant floss in those areas
What is the minimum occlusal clearance for ceramic prosthetics?
True or false... if a ceramic onlay goes subgingival you shouldn’t do an ceramic onlay because it requires a rubber dam and excellent moisture control for bonding
Why do temporaries for all ceramic onlays have to to be compatible with bis-gma?
Becuase it secured to the tooth with flowable and bonding agent
True or false... a ceramic onlay is bonded not cemented
True. A full coverage (either milled or pressed) may be bonded or cemented
When should you etch bond the temporary?
Only if there is little to no mechanical retention/resistance. If its necessary only spot etch a small area buccal and lingual