Dental Cements Flashcards
Define “luting”
to glue
When using cements as luting agents, materials are cemented together mostly via _____ ____
mechanical bonding
Requirements of luting agents
- set in the mouth
- Biocompatible
- none soluble in oral fluids
Cements as luting agents provide ___ and ____
retention and sealing.
Purpose is to cement a restoration to the tooth. To reduce microleakage by filling in the gap between the restoration and the cavity wall
Format of luting agent cements
powder + liquid or paste
Physical properties of cement luting agents
good flow, SMALL AND LITTLE OR NO FILLER PARTICLE SIZE
What type of reaction cementra have typicaly been used to lute metal and ceramic crowns?
Acid-base reaction cements
Luting cements use the __ surface to ____ lock along the path of draw
Luting cements use the ROUGH surface to MECHANICALLY lock along the path of draw
Why is pulpal protection necessary?
Because when bacteria encounters the pulp, the immune system kicks in and sends more blood towards the affected area. However, since the pulp is contained within a strong chamber (enamel), there is no space for additional material/fluid. When inflammation occurs, pulpal tissue begins to die due to cramming.
In summary, when pulpal cells try to save themselves with inflammation response, they end up killing themselves.
Challenges surrounding the replacement of enamel or dentin
- chemical protection
- thermal and/or electrical protection
- mechanical protection
- pulpal medication
The flow of fluid is always from __ to ___ in the tooth
From PULP to CAVITY
Pressure within the pulp
Pressure is high (40 mmHg)
Why woud topical acid not go down into the pulp and cause damage?
Because the high pressure within the pulp (40mmHg) causes fluid to flow outwards towards the cavity. For this reason, fluid will not penetrate the pulp through the dentinal tubules
RDT stands for ___ ___ and requires additional protection when it is below ___
RDT stands for REMAINING DENTIN and it requires additional protection hen it is below 2mm
What causes sharp pain and sensitivity in the tooth?
fluid flow.
If something occurs to increase the fluid flow, osmoreceptors (due to osmotic pressure change) and mechanoreceptors (due to change in fluid pressure) send signals to the brain. IF TUBULES ARE BLOCKED, PAIN IS REDUCED
What effect does blocking dentinal tubules have on pain response?
reduced
Heat is added or extracted from the pulp by the _____ ____
microcirculation system
T/F: composites or glass ionomers are insulating materials
true
Chemical protection of the pulp comes from:
sealing the tubules
Biological protection of the pulp comes from:
pulpal medication
Role of sealers / varnishes/sealers
To form a coating on the tooth and seal all the cavity preparation.
ACT AS A BARRIER TO FLUID FLOW/LEAKAGE and protect pulp against TOXIC AGENTS in the filling materials
Role of bases
materials used to replace missing dentin and bulk build-up
Rank 3 basic cements from thinnest to thickest
varnish
T/F: cavity sealers provide thermal protection
false
should varnish be painted on dentin and enamel?
yes. Entire cavity wall including dentin and enamel
Varnish is ___ dissolved in ____
RESIN dissolved in SOLVENT
Under which restorative material can you NEVER use varnish? WHy?
Under adhesive/composites (prevents setting reaction) or glass ionomore (prevents F release).
varnishes create hydro____ thin films
HYDROPHOBIC
How are varnishes hardened?
By polymerization reaction by visible-light curing
Liners are placed between the ___ ___ and the ____
PULPAL WALL and the RESTORATION
___ have a therapeutic effect on the pulp
liners
bacteria typically live in ___(high or low?) pH
low
Format of liners
powder + liquid or paste
where are liners applied
Thin layer only on the dentin walls that face the pulp
Where can you NEVER place liners? why?
Never place liners on enamel because enamel is not alive. There are no particles to “take” the calcium
Liners have ___ strength and ___ solubility
LOW strength and HIGH solubility
Calcium hydrixide mix involves equal amounts of ___ and ___
CATALYST and BASE
How is calcium hydroxide cured?
silf-cures in 2-3 mins
Cover CaOH in ___
Glass ionomore
How is GI cured?
light cure for 20 sec
When should I use a base?
When RDT is less than 2mm
The base replaces lost ___
dentin
Purpose of bases:
Thermal, chemical and mechanical protection of the pulp. May
Amalgams placed over ___ stiffness bases fracture more than those placed over ___ stiffness bases
Amalgams placed over LOW stiffness bases fracture more than those placed over HIGH stiffness bases
ZOE, zinc phosphate, polycarboxylate and GI are examples of ___
bases
Purpose for temporary restorative materials
- provide short-term protection
- allow time for permanent restoration construction (eg. indirect restorations)
- allow time for pulp healing
- evaluation of pulp
- treatment plan
Direct vs indirect capping
Direct capping: when pulp is exposed and visible.
Indirect capping: when there is still a thin layer of intact dentin over the pulp (<0.5mm)
pH of CaOH
pH = 11, therefore kills bacteria. Also helps create tertiary dentin
CaOH disadvantage
- dissolves if leakage occurs
- weak and flexible
traditional cements setting reaction
basic powder + acidic liquid –> set cement (salt + unreacted powder)
Why do we want to maximize the amount of powder incorporated into the liquid?
because too much liquid = more matrix = lower mech properties
Is zinc oxide soluble or insoluble?
insoluble
Zinc oxide powder reacts with ____
acid
Main advantage of zinc oxide?
it has an antibacterial effect
Primary use of Zinc Phosphate Cements?
luting agent (cast restoration, ortho) -use when gluing any kind of metallic material to the tooth
Do not use zinc phosphate cements if dentin is less than ____. Why?
<1.0mm, because Zinc phosphate is acidic and can cause damage to pulp
What control rate of reaction in zinc ohsphate cements?
buffering salts.
Rate is also affected by temp and water content (accelerate by increasing water)
Zinc phosphate cement is mixed over a ____ area. Why?
wide area. To dissipate the heat of reaction
Why is the frozen slab technique used?
- to increase working time and setting time
- used when long working time is required
- more powder can be incorporated the colder it gets
Which cement requires that the powder be divided into 6 increments?
Zinc phosphate.
Start with 1/16, 1/16, 1/8, 1/4, 1/4, 1/4 added from smallest to largest and mixed for 15 s each.
Uses of polycarboxylate cement
primarily as a luting agent for cast restorations
The reaction of polycarboxylate cement includes…
crosslinking polyarylic acid polymer by Zn2+ ions (1 ion connects 2 chains) so the initial setting time is very short
polycarboxylate cement is mixed on what kind of surface?
on a paper pad. Mixed quickly
Polycarboxylate is reactive towards:
positive ions. Therefore it will chemically bind to a glass slab (use paper instead), tooth structure, or stainless steel spatula (use plastic instead)
define chelation
Bonding of ions and molecules to metal ions.
ZOE stands for:
Zinc oxide eugenol
Zinc oxide eugenol is mostly used for:
temporary filling material or temporary luting agent. Cavity base.
ZOE reaction
Zinc Oxide + Eugenol –> Zinc eugenolate + water
What can greatly accelerate the reaction of ZOE?
Humid environment (such as oral cavity) or mixing with trace amount of water
ZOE is typically mixed on what surface?
glass
What was the first tooth-colored filling material?
Silicate cement
glass is composed of ___
silica
In silicate cement, glass is mixed with ___ ___ and a matrix is formed
phorphoric acid
What do you call metals and metallic salt that will lower the melting point of glass? Give an example of one in dentistry
fluxes. Usually fluoride
The glass powder in silicate cement and glass ionomer cement is made from a glass fluxed with ___ and ____ ____
ALUMINA and SODIUM FLUORIDE
Main use of silicate cement in dentistry:
- cements
- tooth colored filling material
- was frequently used in patients with very high caries indices
- low-cost and anti-caries activity (due to anti-bacterial fluoride)
Describe in words the basic reaction that occurs during the mixing of silicate cement
When the silicate cement is mixed, the acid (phosphoric acid) dissolves part of the glass, releasing ions.
The set cement consists of glass particles and fluoride salts cemented together by the ALUMINUM PHOSPHATE MATRIX
Main advantages/disadvantages of silicate cement
ADVANTAGES:
-Cariostatic effect due to fluoride release
-initially good esthetics
DISADVANTAGES:
-brittle and has lack of wear resistance causing
-rougher surface
-stains over time
-souble
-low tensile strength
-poor biocompatibility due to high acidity
What has silicate cement been replaced by?
- glass ionomer (more aesthetic)
- resin composite material
polycarbooxylate cement provides adhesion to enamel due to _____
chelation
2 most important things about glass ionomer to remember:
- Provides FLUORODATION
2. Provides ADHESION to the tooth
GI uses
- permanent luting agent for cast restorations and ortho bands
- cavity base
- liner
- pit and fissure sealant
- endodontic sealant
- permanent restorative material for non-occluding surfaces
ISO ADA types of GI
Type I - luting
Type II - Restoration
Type III - liners/base
What type of acid prevents thickening of polyacrylic acid (PAA-used for GI) during storage?
itaconic acid
What does tartaric acid do?
controls the setting rate of GI
The powder/liquid GI system includes a ___ powder and an ____ ____ liquid
BASIC powder and an ORGANIC ACID liquid.
Powder: glass powder containing Ca, Al, SiO2 and fluoride.
Liquid: polyacrylic acid, itaconic acid, tartaric acid and water
Why does the glass ionomer need to be protected during the first 10 mins?
Because it can swell due to saliva imbibition or dry due to syneresis. For this reason, petroleum jelly can be applied until GI has set.
When the polyacrylic acid attacks the glass particle, a silica-based hydrogel is created which releases Al, Ca, and F ions. This is highly sensitive to water.
How do GIs reduce likelihood of recurrent decay around the margins?
through fluoride release
Can GI be used for children?
yes
What happens to the rate of fluoride release over time in GI?/
During the first hours, there is a strong release of fluoride (20ppm). After the first day, this reduces to a much slower rate (1-2ppm)
How is fluoride pushed back into cements?
by osmotic pressure. THerefore, once fluoride is released, it can be replenished (by brushing teeth with fluoride toothpaste or receiving topical fluoride at dentist)
Gi bonds ____ to the tooth structure
chemically
Main advantages of GI
- bonds chemically to tooth structure
- fluoride release
- coefficient of thermal expansion similar to tooth
Main disadvantage of GI
- low strength and wear resistance
- poor esthetic
- technique sensitive (ie. has to be protected gainst imbibition and syneresis)
- sensitive to water contamination during placement
What is RMGI? What are the advantages/disadvantages of this material?
RMGI = resin-modified glass ionomer (80% glass, 20% resin)
ADVANTAGES:
-light cured (longer working time)
-resin prevents syneresis and imbibition (no need for vaseline)
-different colours for more aesthetic
DISADVANTAGES:
-Releases less fluoride than traditional GI (polymer barrier protects GI from water, but also prevents fluoride from being released)
