Fall Lecture: Foundation with Direct Restorative Flashcards
Core build up material is aka:
foundation material
When to use core or foundation
caries, fracture, loss of filling, creation of access cavity for RCT
Core replaces:
pulp, lost tooth
Survivability of individual tooth, mostly dependent on:
amt of coronal and radicular tooth
When to asses sound structure and type of restoration:
before tx planning
ferrule:
band of circ material encircling cervical area of tooth restored w crown OR supragingival tooth structure remaining
Effective ferrule ht:
1.5-2mm, uniformly and circ around tooth
ideal core material:
stable in wet env, ease of use, rapid, hard set, high compressive, tensile stength, modulus of elasticity and fracture toughness, inert (no corrosion), cariostatic props, biocompatible, cheap, should not contract/expand too much
modulus of elasticity is related to:
rigidity
materials for foundation or core:
silver amalgam, composite resin, GI, and RMGI
Different ways composite resin can be cured:
chem, photo, dual
Indications for silver amalgam:
replacement of existing restos, large Class I, II, V, core build up, caries prone pts
Advantages of silver amalgam as core;
spherical high copper amals, have high 1h compressive strength (1 appt.), superior dimensional stability, minimal leakage, self sealing bc of percolation, less sensitive to moisture contamination, color contract for crown margin placement, MOE 3X higher than comp resin, great retention w amalcore, pins, posts, no expansion, slight contraction, no microleakage
Amalgam with high 1-h compressive strength:
spherical high copper amalgam
The lack of moisture contamination with amalgam is good for:
subgingival lesions, bleeding
Which is more rigid, amalgam or resin?
amalgam
MOE for amalgam is __ times higher than resin.
3
Disadvantages to silver amalgam as core:
low early strength, 15-20m setting bf crown prep, not good for esthetic zones bc of corrosion and discoloration, (EXCELLENT FOR POSTERIOR TEETH), pins can introduce stress and crazing of dentin
Amalgam sets by:
crystalization
Initial setting time of amalgam:
15-20m
3 types of dental amalgam alloys:
conventional lathe cut, spherical and admix
Best alloy type for core build up:
spherical, less time to set than the other 2, prep can be done in 20m, req less mercury bc there is less surface area, lower mercury/ alloy ratio, better props, less expansion, doesn’t stress crown
Spherical amalgam:
easily condensed, readily carved, high initial/final strength, difficult to achieve proximal contact
Why not to use spherical allow for Class 2 resto?
hard to make interproximal contact
1h compressive strength, highest to lowest:
valiant, tytin (both spherical), dispersalloy, velvaloy, phasealloy
24h compressive strength, highest to lowest:
valiant, tytin, phasealloy, dispersalloy, velvalloy
TF? Spherical alloy has both higher 1h and 24h compressive strength.
T
Amalcore:
coronal-radicular resto, uses pulp chamber and the coronal 2-3mm of each canal for retention of core material, post only if pulp chamber depth is not insufficient
how to overcome the fact that amalgam does not bind to prep wall?
bonding systems
Bonded amalgam technique:
dentin bonding system w viscous resin liner that physically mixes with amalgam, forms micromechanical union, increase retention to tooth
Dual cure adhesive can:
create locking w dentinal tubule by creating resin tag and hybrid layer, bonds w amalgam, retention with tooth surface is much higher
conventional amalgam:
no micromechanical chemical locking w tooth
Cx in for bonded amalgam restoration:
when remaining tooth structure is not enough, extensively carious post teeth where it acts as a cost effective alternative, deep bite where short clinical crown is present
Adv of bonded am resto:
adequate dentinal sealing, conserv tooth prep, elimination of use of retention pin, inc res and ret form, red microl, dec post-op sensitivity, imp marginal sealing, red 2’ caries, single appt, but reduced bond strength over years, more $
Dental amal is hydroph___
obic
Hydrophilic end:
dentinal tube, hybrid layer
Higher efficacy, filler or unfilled?
fillled
Resin tags enter:
dentinal tubules
Type of resin to use for bonded am resto
self or chem bonding system
Fxn of circumferential slots:
increase retention of complex amal restos
segmental cicm slot: are aka:
cleats
Amalgapins:
retention tech, circular channels, vertically into dentin, depth: 1.5-3mmm, diameter: 1mm, never done in enamel
Burs that can be used to amagains:
1156, 1157, 330, 56
TF? Resistance to displacement provided by amalgapin is similar to that provided by self threaded pins.
T
Down side of threaded pins:
sig amt of dentinal crazing or fracture
This end of the adhesive bonds with the tooth structure:
hydrophilic end bonds w the hybrid layer, phobic bonds with the amalagam
When to condense the amalgam for a bonded amal resto:
while the resin is in viscous liquid form
This increases the retention of the bonded amal resto:
fingerlike resin tags incorporated with amal and dentinal tubules
Does bonded amal resto inc or dec post op sensitivity?
dec, but more expensive
Which type of curing system to use with bonded amal resto:
self curing or chem activated, bc light can’t get there
Is bonding a satisfactory method of retaining amal restos replacing cusps compared to pin-retained amal restos?
yes (current research)
Bur to make circ slots:
33 1/2 inverted cone bur
The resistance to displacement provided by amalgapins is similar to that provided by:
self threaded pins
Benefit of amalgapin over self threaded:
eliminates the risk of dentinal crazing caused by threaded pins
Define crazing:
fracture
cemented stainless steel pins:
extensively damaged tooth for complex amal, not going into pulp chamber
Negative to cemented stainless steel pins:
vertical root fracture or dentinal crazing
Do amalgam cores expand causing tooth frature?
no, many have net contraction
net contraction of many modern high copper amalgams is due to:
low mercury alloy ratio, smaller mercury/alloy ratio, use of mechanical amalgamator (removes excess mercury from the field)
The more mercury removed from the field,
the more contraction of the amalgam
contraction or expansion: spherical, admixed, fine lather cut
spherical: slight contraction, admixed: slight expansion, fine lather cut: significant contraction
Do amal and resin based composite resto cause cusp fracture?
no sig dif
Core build up material for esthetic zone:
composite resin
Adv of composite resin as core build up:
high compressive strength, bind to tooth when used with an adhesive, ease of use, light cure, dual cure and self cure formulations, available as tooth colored for use in esthetic zone and also as color contrasting material for use with metallic or opaque ceramic crowns, fracture toughness is similar to amalgam
Disadv to composite resin as core:
polymerization shrinkage and stress at the adhesive interface, dimensional expansion in wet env (water sorption can prevent proper fit of crown), long term water sorption by core can cause loss of material bc of this solubility, lower fatigue resistancethan amalgam, resin bond may weaken w time and fxn
How to eliminate the shrinkage gap due to polymerization shrinkage of resin:
use incremental tech
List the composite resins that are best for core build up
light cure resins: Clear Fill Photo core, Encore SuperCure, Rebilda LC, Bis-Core, CoreReestore
List the composite resins not to use for core bc of shrinkage:
Ti-Core, Core Paste, Core-Flo
Light cure rc are not
sensitive to dentin bonding agents
Adv of Gi or RBGI as core build up:
bonds to tooth, ease of manip, corrosion resistance, biocompatability, fluoride release, just “initial burst’ in 24h only, then decreases thereafter
Disad of GI or RMGI as core build up:
brittle, very low compressive and tensile strength high water solubility, dimensional instability (polymerization and volumetric shrinkage), not good for core build up
When to use GI or RBGI for core build up:
only as ‘block out’ material but not as extensive cores
Best choice for core build up on posterior teeth:
spherical silver amal
Core material to use in esthetic zone:
light cure resin composite
Care to use when making a composite resin core build up:
isolation, incremental addition and proper adhesive use
TF? GI’s are good for extensive core build up materials.
F
When to use bonded amal resto:
extensively carious pos teeth , very little remaining tooth, deep bite with short clinical crowns, core of foundation build up,
Bonding system used for bonded amal restos:
4 META (4-methacryloyloxyethy trimellitate anhydride) (amalgabond +, fine metacrylic powder as filler, other has liner)
Adv of light cure comp resin for core:
not sensitive to any dentinal bonding system, not as much shrinkage as self curing
TF? Circumferential slots give you as much retention as a pin.
F
