Quiz 2/9 Try-In and Cementation Flashcards
tool to remove interim:
Bachhous forceps, hemostat
Try-IN procedure for cast metal resto
proximal contact, marginal integrity, stability, occlusion
Most common issue with proximal contact:
too tight
How to jude tightness of contacts:
compare to other teeth in mouth
TF? Pt response is sufficient to confirm a tight contact.
T
How to correct proximal contacts:
CCC - rubber wheel, porcelain: - cylindrical mounted stone
How to correct contact in a gold casting:
soldering
Clinically acceptable gap for marginal adaptation:
30um
How to assess marginal integrity:
sharp explorer - tooth to resto, open margin = 50um the tip of sharp explorer can be inserted bw the resto and tooth
Materials to test whether the casting binds the tooth surface:
disclosing wax, suspension of rouge in chloroform or ether (PIP), air abrasion to form a matte finish, powdered sprays, water soluble marking agents, elastomeric detection paste
most reliable fit checker:
elastomeric detection paste
Can instability produces by a small pos odue be corrected?
yes, trimming
How to fix instability due to distorted wax pattern:
repeat
Width of braze gap:
0.25mm
What shape should sectioned pieces have?
flat, parallel
Use this to conect the two sectioned pieces of bridge:
GC pattern resin
Name of procedure adhering part of bridge together:
indexing
How to check for stability of indexed assembly:
no rocking, satisfactory margin adaptation
Do this before sending to lab for soldering:
GC pattern Resin (not over margin!)
Look for these esthetic issues in a ceramic resto:
enamel cracks, stained crack lines, exposed occlusal dentin, incisal halo
Ideal luting agents:
long working time, adhere to both, good seal, non-irritatin, non-toxic, adequate strength, compressible to thin layers, low viscocity, low solubility, good working and setting characteristics, easily removed, F release
Types of luting agents:
zinc phosphate, zinc silicophosphate, zinc polycarboxylate, xinc oxide-eugenol w/ wo EBA, GI, adhesive resins, resin modified GI’s
Cement bonding agents:
non-adhesive, micro-mechanical, molecular
Zinc phosphate cement is made of:
ZnO powder and phosphoric acid
Adv’s of since phosphate cement:
good track record of success, high stability of specimens older than 40yo, adequate strength, reasonable working time, excess material easily removed
Disadv’s of zinc phosphate cement:
water sensitive during setting, microleakage, high solubility esp. in acidic env, pulp irritation, low initial pH, lack of antimicrobial action, brittleness, lack of adhesion
Zinc silicophosphate:
high compressive strength, moderate tensile strength, excessive film thickness 88um at the occlusal surface under an actual casting, acid pH - may harm pulp
Zinc Polycarboxylate cement:
Powder: zjnc oxide w 1% to 5% tin or Mg oxide, 10% to 40% Al oxide or other reinforcing filler, the acid 40% (high MW) polyacrylic acid or acrylic acid copolymer w other organic acids.
Zinc Polycarboxylate cement is good for cementing:
crowns and 3-unit bridges (3ub)
Adv of Zinc Polycarboxylate cement::
low adhesion to tooth, chelates w Ca, adhesion to some alloys, higher tensile strength compared to zinc phosphate cement (lower compressive strength), anticariogenic (less than GIC), biocompatible w pulp, rapid rise of cement pH toward neutrality, little post-op sensitivity, film thickness comparative to those of zinc phosphate cements, solubility in distilled water
Disadv to Zinc Polycarboxylate cement:
lower compressive strength that zinc phosphate cement
Which is more anticariogenic, Zinc polycarboxylates cement or GI?
GI
DIsadv to zinc polycarbocyalet cement:
thixotrpoic, (too thick, willnot low), short working time compareed to Zn/Po cement, difficult to lute long span bridges, residula cement more difficul tto remove, weaker that Zn/Po, plastic deformation, unsuitable to high load areas
Mix Zinc Polycarboxylate cement on:
glass slab, so it doesn’t lose water, don’t extrude early or it will lose water
To inc setting time of Zinc Polycarboxylate cement:
cool glass slab and stainless steel spatula
Zinc Polycarboxylate cement should not be disturbed in this stage::
rubbery, will pull from the margins
Composition of GI cement:
alumino-fluorosilicate glass + weak polyacrylic acids
Effect of early water exposure on GI cement:
sig recuctino in ultimate strength
Properties of GI cement
low cement film thicknesss (25-35um), doesn’t appear to more irritant to pulp
Adv’s of GI cement:
adheres to both enamel and dentin, low bond strength to teeth, biocompatible, no pulp protectin required, F release, anticariogenic, easy to mix, resistant to acid dissolution, set cement is translucent (good for using porcelain labial margin), mechanical props comparable w zinc phosphate cement (comparative compressive strength
GI disadv’s:
long term sensitivity if tooth over dired, highly susceptible to moisture contamination during setting, slow set, possible pulp irritation, variable adhesive characteristic, residual cement more difficult to remove
Hybrid ionomer cements:
resin modified polyalkenoate cement (resin + GI powder), combines strength and insolubility of resin w the F release of GI, recmmend use for all-metal or ceramo-meatl crowns and bridges, not posts (risk fo expansion induced root fracture), not recommneded for all-ceramic restos (delayed expansion, ceramic fracture), workign time lengthened by cooling liquid, mixing on cool slab or dec P/L ratio, inc temp - dec workign time., microetchingt o prepare internal metal surfaces for inc bonding, remove excess cement before final set, use desnsitizing liquid to red sensitivity wo major effect on bond to tooth
Composition of adhesive resin agents;
Bis-GMA resins and other methacrylates
adhesive resin agents can be categorized by:
chemical-, photo-, and dual cure
How does adhesive resin agents adhere to enamel and dentin?
micromechanical, penetration of hydorphilic monomers through collagen layer overlying partially demineralized apatiite o etched dentin
Function of conditioner of adhesive resin agents
remove smear layer, demineralize top 2-5um
Primer used for adhesive resin agents:
wetting agents such as HEMA applied, enables philic bond to dentin and phobic bond to ashesive
Adhesive cemetn that penetrates into tubules:
4-META
Provblem w adhesive resin agents:
polymerization shrinkage
Can cement change shade of veneer?
yes
These pastes can facilitate selecting the best cement shade:
colour matching try-in paste
Adv’s of adhesive resin agents:
high strength, low oral solubiility, high micromechanical bonding to prepped enamel, dentin, alloys and ceramic surfaces
Disadv’s of adhesive resin agents:
meticulous/ critical technique, difficult sealing and higher film thickness than most cements, possible leakage and pulp sensitivity, tought to remove excess cement
Provisional cement we use:
ZOE
Powder portion of ZOE:
sinc oxide
Liquid portion of ZOE:
eugenol
Film thickness needed for ZOE:
40um
TF? ZOE is highly anticariogenic.
F. slightly
ZOE, highly soluble?
yes, 1.5%
how to reinforce ZOE cements:
add EBA, aluminaum oxide and PMM
ZOE has this effect on pulp
Abtudent, good sealing ability and resistance to marginal penetration
Purpose of luting cement:
seal tooth-restoration interface space
What does the choice of definitive cement depend upon?
conventional casting resto ro adhesive restoration
TF? Both zinc phosphate and resin bond to tooth.
F. zinc phosphate does not
Longer working time, inc phosphate or resin bond
sinc phosphate
