Flashcards in Midterm Review Deck (90):
why is it that the cavosurface angle is left at close to 90* with ceramic restorations?
most ceramics don't have a high tensile strength
if you're looking for the ultimate in esthetics, is partial coverage or full coverage better?
what's the advantage of milling green or presintered blocks of ceramic?
it's easier on the tooling
why is zirconia usually milled in the green or presintered state?
because it is such a hard material, but it is softer when it is green/presintered
once you've bonded your ceramic restoration to the tooth, is the whole thing stronger?
yes, everything is much stronger
what is the one advantage of tribochemical coating over APC protocol?
it maintains its bond strength better over time
keeping dentin moist was decided upon during which generation bonding system?
what is the #1 reason for early retirement in dentists?
work related musculoskeletal disorders
is it desirable to bond glassy ceramics (silica based ceramics)?
yes, because it strengthens it, and it is retrievable (but this is not true of crystalline ceramics)
why do you want contrasting color for buildup material?
it is easier to see the margins
what is the rationale for breaking contact with porcelain veneer preps?
facilitates the lab's ability to read it, reproduce it, and it makes it easier on cleanup
in the esthetic zone, should you have margins at the interproximal contacts of porcelain veneer preps?
no; you need to break contact
what is the perfect way to cut up silicone putty reduction guides?
trick question! there is no perfect way
what are silicone putty reduction guides used for?
to facilitate reading reductions
is it always necessary to cut silicone reduction guides into thirds?
no, you may want to cut more or less, or at different angles, but cutting it into thirds is usually sufficient
what is the bond of the adhesive chemistry to the tooth?
is there any reason to photocure a dual cure material?
yes, it enhances polymerization
what is the chemical that forms the bond with glassy ceramics?
what forms does silane come in?
hydrolyzed and prehydrolyzed
what are the advantages and disadvantages of prehydrolyzed silane?
-advantages: only one step, it is easier and more direct
-disadvantages: doesn't have a very long shelf life
intentional complete removal of the smear layer became popular with what generation bonding system? what was the norm before that?
-before that, partial removal of the smear layer was the norm, but it was realized that removing the entire smear layer and covering it with resin was better
what can occupy bonding sites of zirconia?
-phosphoric acids in saliva
-phosphate on MDP
functional monomers have a ___ structure on only one end of the molecule; the ___ end performs a specific "function"
functional monomers have a functional end that contains what possible groups? what does each group bond with?
-phosphate group to bond with metallic oxides
-silane or Si containing group to bond with glassy ceramics
the functional groups of functional monomers bond the ___ to the ___, forming a link between dissimilar materials
organic to the inorganic
the functional groups of functional monomers form links between dissimilar materials. what are 3 examples?
-bis-GMA resin to glassy ceramic
-bis-GMA resin to crystalline ceramic
-bis-GMA resin to base metal
functional monomers with phosphate groups are the basis for ___ and ___
acidic monomers and self-etch adhesives
cross-linking monomers have a ___ structure on BOTH ends of the molecule
cross-linking monomers are the building blocks for ___
are cross-linking monomers or functional monomers more symmetrical?
the structure of cross-linking monomers can influence the ___ of the unpolymerized monomer, and the ___ of the polymerized resin
-viscosity of the unpolymerized monomer
-physical properties of the polymerized resin
which 2 cross-linking monomers are viscous?
bis-GMA and UDMA (urethane dimethacrylate)
which cross-linking monomer is used to reduce viscosity?
TEGDMA (triethylene glycol dimethacrylate)
which resin types are best to use with vitreous ceramics? why?
esthetic resin cement and adhesive resin cements because they are the most retentive (adhesive is the MOST retentive)
what are 3 important considerations when using self-adhesive resin cements?
-least retentive of all resin cements
-keep dentin moist during cementation
-do final light cure of all marginal areas
all resin cements (esthetic, adhesive, and self-adhesive) provide mroe retention than ___ cements
RMGI (relyx luting plus and fujiCEM)
which resin cement provides the ultimate bond strength?
which resin cement offers "simplicity powered by performance"?
which resin cements do not require a separate primer to bond to tooth structure?
self-adhesive resin cements
what is the APC protocol?
1. A- Air particle abrasion
2. P- zirconia Primer application
3. C- Cement with either dual-cure or self-cure composite resin cement (best is adhesive or self-adhesive)
what are the two steps to bonding zirconia?
1. tribochemical coating
2. APC protocol with MDP
what does tribochemical refer to?
1. relating to lubrication by chemical means
2. caused by rubbing together mechanically
what is tribochemical silica coating?
1. tribochemical assisted bonding
2. air abrasion with silicon coated aluminum oxide particles
whether luting or bonding, why is it important to not allow the indirect restoration to be disturbed during clean-up for the full set time of the resin cement? what is the exception?
-because micromovement of the indirect restoration while the cement is setting will significantly reduce bond strength
-the exception to this is with adhesive resin cements like C&B metabond
T or F:
if you decide to bond zirconia, it is not necessary to keep within the same manufacturers materials as long as you follow the manufacturers instructions
-you should always follow manufacturers instructions, and it is best to keep within the same manufacturer's materials to ensure compatibility with adhesive and cement
what are 3 of the only reasons you should consider bonding zirconia?
1. resistance and retention form is inadequate
2. restorative material is thin
3. the restoration is a fixed partial denture
what is one major issue with bonding zirconia?
-retrievability is very difficult
-you can fracture teeth by prying apart sectioned halves of the bonded crowns (dentin bond strengths are now approaching the internal strength of dentin)
is zirconica crystalline or glassy/vitreous?
T or F:
there is no clear evidence of chemical bonding between porcelain and zirconia
porcelains form ___ bonds with metals via the ___ layer
-metal oxide layer
due to the chemical bond formed between metal and porcelain, which types of crowns have lower failure rates?
PFM crowns and FPDs have lower failure rates than PFZ crowns and FPDs
describe self (chemical) initition
-tertiary amine in the base paste
-BPO chemical initiator in a catalyst paste
-combination of the two pastes produces free radicals that attack the carbon double bonds
describe photo initiation
-camphorquinone or other photo-initiator absorbs blue light, then reacts with amine activator to form free radicals
-these free radicals then attack the carbon double-bonds
what provides working time in self-cure resins?
-inhibitors such as butylated hydroxytoluene (BHT) and monomethyl ether of hydroquinone (MEHQ) prevent spontaneous polymerization and provide working time
-oxygen is also a powerful inhibitor as it reacts with the radicals to form peroxyl formulations (O2 + free radical)
in self-cure resins, the ___ eliminates the need for heat to initiate free radical formation
incompatibility between bonding agents and dual cure composite resin formulations primarily occurs with ___ due to ___
self-etch adhesives due to acidic monomers (pH < 3)
how do you prep the intaglio surface of lithium disilicate (e max)?
20 second etch with 5% HF
how do you prep the intaglio surface of leucite ceramics?
60 second etch with 5% HF
how do you prep the intaglio surface of feldspathic ceramic?
120 second etch with 9% HF
how do you prep the intaglio surface of zirconia?
-DO NOT ETCH...I'm looking at you, Taylor
-sandblast intaglio surface with 30-50 um alumina particles for 10 seconds at 30 psi
what are the indications for porcelain veneers?
-minor and moderate morphological changes
-moderate shade changes
-posterior tooth should be in relatively good condition
-should be considered with doing anterior veneers
-mandibular anterior veneers are an excellent choice for damaged teeth with an intact lingual surface
-adding incisal length for mandibular incisors
for porcelain veneers, what is the minimum number of cavosurface margins that MUST contain enamel?
3 cavosurface margins with enamel
what are contraindications for porcelain veneers?
-insufficient tooth structure
-insufficient enamel for bonding
-poor oral hygiene
-uncontrolled parafunctional habits
can posterior veneers be placed over existing restorations?
-yes (class I or class II), as long as existing restorations are in excellent condition, small in size, and not discolored
-class II would need 3+ enamel surfaces
why do you make two putty matrices for porcelain veneers?
one is for the reduction guide and one is for the temporary matrix
what is the uniform facial reduction of porcelain veneer preparations?
T or F:
when preparing posterior teeth for porcelain veneers, you should NOT prepare beyond the occluso-buccal line angles
T or F:
in both anterior and posterior porcelain veneer preparations, it is important to just barely break contact interproximally on all teeth surfaces with the exception of the distal contact of the most posterior tooth included in the preparation
-contacts should only be broken (SLIGHTLY) on anterior teeth (no contact broken between the canine and 1st premolar)
-contacts should not be broken interproximally between any posterior teeth
what does a facial chamfered margin design allow for in posterior porcelain veneer preparations?
allows for more bulk of material and a stronger veneer
why are veneers not indicated for minor shade changes?
because you can typically take care of that with bleaching
what are some appropriate applications of veneers as a treatment modality?
-intrinsic enamel discolorations
-minor tooth malposition
what is the ABSOLUTE minimum number of enamel surfaces needed for porcelain veneer preparations?
-ideally, you should have at least three surfaces
for anterior porcelain veneer preparations, what is a major advantage of the lingual chamfer margin?
you get a more secure seat
what is the porpoise of a lingual veneer?
to restore anterior guidance; it is more durable than a direct composite
what are the advantages of no-prep veneers?
-no preparation time
-usually more than adequate amount of enamel for bonding
what are the disadvantages of no-prep veneers?
-no definite fit position for the veneer
-can be bulky and difficult to clean at the gingival margin
-can be over-contoured toward the labial portion
-can make patient's lip feel tight
-can enlarge teeth
-can retrude or distalize mandible and create TMJ problems (mo material, mo problems)
how many mm of restorative material (aka veneer thickness) is required for 1, 2, and 3 shade changes?
*this is a rough guideline only*
-1 shade change = 0.2-0.3mm
-2 shade changes = 0.4-0.6mm
-3 shade changes = 0.7-0.9mm
what type of material do you not want to use for veneers?
can anterior veneers be placed over existing restorations?
-yes (class III, IV, and V) if they are in excellent condition, small in size, and not discolored
-if the class IV is too big, you'll want to do a full coverage crown instead
what is the incisal reduction for a lingual chamfered margin design for anterior veneer preps?
1.5-2.0mm (according to lecture slide) or 2.0-2.5mm (according to grading sheet)
which cement is usually chemical (self) cure, has limited shades, bonds to many surfaces, provides the strongest bond of all the cements, and is good under metal or other opaque material?
which cement provides a good, intermediate bond strength, and does not require etching, conditioning, or priming?
what is self-adhesive cement not recommended for?
veneers or feldspathic porcelain bonding
most self-adhesive cements bond better to ___ than ___
dentin than enamel
which cement must be used with a separate bonding agent, tooth enamel must be etched with phosphoric acid in preparation for bonding, and can be light-cured or dual-cured?
why should you use light-activation whenever possible with esthetic cements, even if they are dual cure?
dual-cure cements typically have increased flexural strength and bond strength when activated with a light
esthetic cements provide a very strong bond, especially to ___
proximal finish lines of porcelain veneer preps should be ___; all internal line angles should be ___
using the temporary technique we utilized in lab, why should you prescribe a chlorhexidine rinse for your patient? how long should the patient be on this prescription?
because the patient will not be able to floss during this period; the patient should be using the rinse for the duration of the temporary phase