Materials for luting and Adhesion Flashcards
what are the objectives of cementation and luting?
- maintain restoration in place
- maintain integrity of remaining tooth structure
cementation retention is achieved by what four things?
friction
adhesive joint
the cement
the restoration
what two things does an effective interfacial seal depend on?
- ability of the cement to fill the irregularities between the tooth and the restoration
- resist the oral environment
the classification of luting agents is according to what?
the length of time that they are expected to stay in function and setting.
what is a provisional luting agent?
stays in mouth for a short period of time
low strength and easy handling, no irritation of pulp.
what are examples of provisional luting agents?
zinc oxide, non-eugenol cements and calcium hydroxide pastes
what is a definitive luting agent?
remain in function for the longest time possible, must have sufficient properties
luting agents of acid based rxn?
GI, RMG, zinc oxide-eugenol, zinc polycarboxylate, and zinc phosphate
luting agents of polymerization?
resin cements, compomers, self-adhesive cements
what are some materials that are capable of creating a chemical interaction with hydroxyapatite
zinc polycarboxylate (acid)
GI (acid)
RMG (acid)
self-adhesive resin cements (polymer)
what Buonocore find in 1955?
that acid etching of enamel increases the bond strength of resin to enamel
T/F almost half of all restorations placed n general dental practice are done to replace a defective or failed restoration?
true
what are the three major categories that restorations need to be replaced?
clinician factors
material properties
patient factors
what is the composition of dentin?
50% mineralized apatite crystals
20% water
30% organic matrix (collagen fibrils)
what happens to diameter and number of tubules near the pulp?
they increase
what are some characteristics of sclerotic and caries affected dentin?
hypermineralized
tubules occluded with CaPO4 crystals
Acid resistant
what happens to dentin collagen fibers if they become too dry?
they collapse
what is the overwet phenomenon?
when a primer is displaced over a water droplet to from a meniscus.
leads to bubbles of the primer
what does the smear layer composed of?
bacteria saliva blood cells denatured collagen *cannot be removed with rinsing 0.5 -2.0 microns thick
what is the hybrid layer?
the structure formed in hard dental tissues by demineralization of the surface and subsurface, followed by infiltration of monomers and subsequent polymerization.
what is a resin tag?
resin monomers that have infiltrated demineralized dentinal tubules. allows for max bonding
what are dentin primers made of?
hydrophilic monomer HEMA -water soluble solvent water acetone ethanol
what are dentin adhesives made of?
unfilled or lightly filled resin (Bis-GMA)
how many steps are in the 4th generation?
3
conditioner
primer
adheisive
what is the conditioner of the 4th generation?
phosphoric acid, removes smear layer
what is the primer solvent in the 4th generation?
acetone and ethanol
in the 5th generation what is the conditioner?
phosphoric acid only, removes smear layer
in the 5th generation, are the primer and adhesive combined?
yes, it is heat sensitive so it needs to be stored in a cool place
in the 6th generation what two steps are combined?
the conditioner and primer(called a self etching primer.
- this dissolves the smear layer
- *acid monomer with water
in the 6th generation is the adhesive combined with any other steps?
no, it is it’s own step
what is the purpose of the primer?
to create hydrophilic conditions, to allow adhesive to penetrate the tubules
what are the differences between the 4th and 5th generation adhesive systems?
-4th gen has primer and adhesive separately
has more steps and more predictable
-5th gen has primer and adhesive mixed together in one bottle
less predictable and more susceptible to differences in wetness.
self etching adhesives
-big difference in technique
-user friendly, no phosphoric acid
-acidic monomer dissolves smear layer and primes dentin simultaneously
-one or two step systems
6th gen
self-etch adhesives latest research with bonding?
higher bond strengths in deep dentin than 4th and 5th gen
- bonds well to cut enamel
- less pronounced resin tag formation, no real effect on bond strength
- two step are more predictable than one-step.
what is the 7th gen of adhesives?
all in one
dissolves smear layer, self etching primer and adhesive all in one bottle.
**NOT recommended.
what is always the solvent in 6th gen?
water
which generation is considered the gold standard?
5th generation
single bond plus (3M ESPE)
-ethanol/water; unfilled
what is a good 6th gen product?
Clearfil SE bond
-water, 10% filled; light cured
which generations are called “total etch or etch and rinse”?
4th and 5th because you have to rinse the phosphoric acid
which generation are called “ self etch”?
6th and 7th because the conditioner and primer are in one bottle.
in the 7th generation what is the make up of the all in one bottle?
ester monomers with grafted carboxylic or phosphate acid groups dissolved in water
T/F Most bonding agents are light-cured and contain an activator such as camphorquinone and an orgainc amine?
True
camphorquinone is light cured
orgainc amine chemical polymerization
in dual cured bonding agents a catalyst is added to promote self-curing along with a light curing chemical? T/F
true hence the dual
what are some additives put into bonding agents?
nanofiller
fluoride
antimicrobial ingredients
or densentitizers (gluteraldyhyde) carcinogenic
what is the most important mechanical property among in-vitro research?
bond strength
why is longevity of bond in general practice on 40% of that achieved in clinical trials?
they are set up in ideal situations
extensive controls for experiments
where are 95% of secondary caries associated with resin composites located?
interproximal areas
how can clinical performance be evaluated?
postoperative sensitivity
interfacial staining
secondary caries
retention or fracture followed for 18 months
how does bonding to enamel occur?
micromechanical retention after etching
-bonding penetrates the etched surface and becomes locked into place after polymerization occurs
superficial dentin hybrid layer is a form of?
intertubular resin infiltration(interaction with collagen)
deep dentin hybrid layers are mainly composed of?
resin tag formation
dentin bonding primers
hydrophilic components such as HEMA (wet dentin and penetrate its structure)
etching the dentin with phosphoric acid removes the mineral creating what?
microsporosites within the collagen network
after etching the dentin what is left?
50% unfilled space and about 20% remaining water
after acid is rinsed, what must be done cautiously?
drying so that the collagen doesn’t collapse
what does excess moisture tend to do in regards to primer and bonding?
dilute the primer and interfere with resin interpenetration
what is the hybrid layer?
the structure formed in hard dental tissues by demineralization of the surface and subsurface followed by infiltration of monomers and subsequent polymerization
what is one of the most challenging problems of adhesive/dentin bonds?
durability
what are the principles of adhesion?
protects the interface of restorations against penetration of bacteria and fluids that can cause recurrent or secondary caries
- reduces the need of retentive areas in preparation that would require removal of sound tooth structure
- sometimes strengthen the remaining tooth structure
aspects to create any adhesive joint
cleanliness of the surface (biofilm, debris, saliva)
smear layer
-these contaminants will reduce the surface energy of the bonding substrate and its wettability
