BOARD REVIEW DH227
DENTAL MATERIALS
Lisa Mayo, RDH, BSDH
Concorde Career College
Terms
• Adhesion: the chemical attraction between unlike
•
•
•
•
•
•
molecules
Cohesion: the chemical attraction between like molecules
Coefficient of Thermal Expansion: an index which
indicates how one material reacts to temperature
extremes in relation to another
Compressive strength: the force at which a material
breaks under pressure
Creep: slow dimensional change caused by compression
Ductility: ability to undergo change of form without
breaking
Galvanism: electrical current generated by dissimilar
metals in an acidic environment
Terms
• Gelation: process of gelling (solidification by cold)
• Gram: volumetric weight of one cubic cm or mm of water (1cc
•
•
•
•
•
•
•
or 1mL)
Imbibition: absorption of a solvent by a gel
Malleability: a material’s capacity to be shaped by force or
pressure
Microleakage (percolation): passage of oral fluids/bacteria into
and out of tooth structure due to marginal gap or failure of
marginal (restorative) seal
Polymerization: the linking, branching, cross-linking of smaller
molecules
Proportional limit: the force at which a material cannot return to
its original shape
Synersis: contraction of a gel due to the loss of a solvent
Tensile strength: force needed to stretch a material to the point
of fracture
Terms
• Synergism: shrinkage
• Viscosity: resistance to flow, thick/viscous fluids: flow
poorly
• Contact Angle: wetting. Spreading of a drop on solid
surface, Low = good wetting (porcelain)
• Stress: applied load
• Thermal Expansion for teeth: 10ppm/C°
NBQ
What is the linear coefficient of thermal expansion for tooth
structure?
a. 5ppm/C
b. 10ppm/C
c. 15ppm/C
d. 20ppm/C
e. 60ppm/C
NBQ
What is the linear coefficient of thermal expansion for tooth
structure?
a. 5ppm/C
b. 10ppm/C
c. 15ppm/C
d. 20ppm/C
e. 60ppm/C
Terms
• Base: Ca-hydroxide, thicker then 0.5mm
• Liner: can be used as an adhesive, cement, base.
•
•
•
•
Thinner than 0.5mm
Lute: glue on, resins are the strongest, retain restoration
by interdigitation
BIS-GMA: matrix resins, sealants, monomer
MMA: liquid
PMMA: powder
Structures
• Reaction during use
• Physical: solidification by drying or cooling w/no
chemical rxn
• Chemical: solidification by creating new primary
bonds w/in composition
• Manipulation
• Mixing Variables
1. Manual mixing
2. Auto-mixing
Structures
Manipulation
• Stages of manipulation
1. Mixing Time
• Time elapsed from onset to completion of mixing
2.
Working Time
• Time elapsed from onset of mixing to onset of initial set time
3.
Initial Setting Time
• Time at which sufficient rxn has occurred to cause the
materials to be resistant to further manipulation
4.
Final Setting Time
• Time at which the material is practically set, as defined by its
resistance to indentation
NBQ
What is the definition of mixing time?
a. Time elapsed from the start of mixing until the end of
b.
c.
d.
e.
mixing
Time elapsed from the beginning of mixing until the
beginning of setting
Time elapsed from the beginning of the working
interval until the end of the setting interval
The working interval
The time required by the operator to handle and place
a dental material
NBQ
What is the definition of mixing time?
a. Time elapsed from the start of mixing until the end of
b.
c.
d.
e.
mixing
Time elapsed from the beginning of mixing until the
beginning of setting
Time elapsed from the beginning of the working
interval until the end of the setting interval
The working interval
The time required by the operator to handle and place
a dental material
Structures
Definitions of intervals
• Mixing interval
• Length of time of mixing stage
• Working interval
• Length of time of working stage
• Setting interval
• Length of time of setting stage
• All water-based materials lose their gloss at the time
of setting
NBQ
Which ONE of the following procedures does NOT involve
a loss of gloss during setting?
a. Pit and fissure sealants
b. Plaster
c. Glass ionomer cement
e. Alginate
NBQ
Which ONE of the following procedures does NOT involve
a loss of gloss during setting?
a. Pit and fissure sealants
b. Plaster
c. Glass ionomer cement
e. Alginate
Physical Properties
• Events that do NOT involve changes in composition or primary
bonds
• Thermal properties
• Rate of expansion or contraction
• When the thermal expansion of restorative materials do NOT
match the tooth structure = percolation of fluids occurs at the
margins during heating and cooling
• Thermal conductivity
• Insulators transmit heat poorly: cements, acrylic polymers,
porcelain, ceramic
• Conductors transmit heat easily: amalgam, cast gold
• To be effective insulator = 0.5mm thickness needed
Physical Properties
• Electrical properties
• Electrical conductivity
• Conductors transmit electrons easily: metals
• Semiconductors transmit electrons sometimes:
ceramics, composites
• Insulators transmit electrons poorly: ceramics,
polymers
NBQ
Which ONE of the following is a poor thermal insulator?
a. Dentin
b. Enamel
c. Gold alloy restorations
d. Glass ionomer cement
e. Ceramic inlays
NBQ
Which ONE of the following is a poor thermal insulator?
a. Dentin
b. Enamel
c. Gold alloy restorations
d. Glass ionomer cement
e. Ceramic inlays
Physical Properties
• Color Properties
• Perception: physiological response to physical stimulus
by the eye, which can distinguish 3 parameters
1. Dominant wavelength: blue, green, yellow, orange,
red
2. Luminance: lightness of color from black to white
3. Excitation purity: saturation of light
• Measurement: Munsell Color System, shade-guides
Physical Properties
• Color Properties
• Terms:
• Metamerism :colors that look the same under one
lighting system and different under another
• Fluorescence: emission of light by a material when a
beam of light is shined on it
• Opacity: degree of light absorption by a material
• Translucency: degree of internal light reflection
• Transparency: degree of light transmission through a
material
NBQ
Which of the following terms is not related to color?
a. Fluorescence
b. Luminance
c. Dominance
d. Translucency
e. Resilience
NBQ
Which of the following terms is not related to color?
a. Fluorescence
b. Luminance
c. Dominance
d. Translucency
e. Resilience
Chemical Properties
• Primary chemical bonds
• Types: metallic, ionic, covalent
• Secondary chemical bonds
• Hydrogen bonding: H is attracted to an electronegative element
• Water-based liquids
• Van der Waals forces: dispersion forces caused by fluctuating
dipoles
• Composites, acrylics
• Events related to changes: absorption, desorption, solubility,
disintegration
• Corrosion (next slide)
Chemical
2. Electrochemical
3. Corrosion potential
1.
Chemical Properties
• Corrosion
1. Chemical: products may be soluble or insoluble (forms layers or
tarnish)
2. Electrochemical
• Requires an anode, cathode, electrolyte, electrical circuit for
electron flow
• Galvanic corrosion: dissimilar materials in contact
• Local galvanic corrosion: dissimilar phases in the same metal in
contact
• Crevice corrosion: corrosion in the crack under plaque, between
a restoration and tooth structure, or in the scratch on the surface
of a restoration, where the metals may be the same but the
electrolytes are different locally
3. Corrosion potential
• Immune: does not corrode
• Active: corrodes readily
• Passive: corrosion produces protective film on material
NBQ
Which of the following is NOT associated with
electrochemical corrosion events?
a. Stress
b. Crevices
c. Plaque
d. Passivation
e. Metamerism
NBQ
Which of the following is NOT associated with
electrochemical corrosion events?
a. Stress
b. Crevices
c. Plaque
d. Passivation
e. Metamerism
Mechanical Properties
• Normalization of forces & deformation
• Stress: applied force per unit area
• Stress= force/area
• Strain: change in length per unit of length
because of force
• Resolution of forces
• Uniaxial forces: compression, tension, shear
• Complex forces: torsion, flexure,, diameter
tension or compression
Mechanical Properties
• Elastic behavior
• Elastic strain: initial response to stress
• Elastic modulus: represents the stiffness of the
material
• Elastic limit/Proportional limit: stress above
which the material no longer behaves totally
elastically
• Yield strength: stress that is an estimate of the
elastic limit at 0.002 permanent strain
• Cont’d next slide
Mechanical Properties
• Elastic behavior
• Hardness: value on a relative scale that estimates
the elastic limit in terms of a material’s resistance of
indentation
• Knoop, Diamond pyramid, Barcol, Shore A, Moh’s
hardness scale
• Values used to determine the ability of abrasives
to alter the substrates they contact
• Resilience: area under the stress, estimates the
total elastic energy that can be absorbed before the
onset of plastic deformation
NBQ
Which of the following statements is not true about the
Moh’s hardness scale?
a. Scale involved units 1-10
b. Diamond if the hardest reference value
c. Talc is the softest reference value
d. Enamel is 7-8 on the scale
e. Dentin is 3-4 on the scale
NBQ
Which of the following statements is not true about the
Moh’s hardness scale?
a. Scale involved units 1-10
b. Diamond if the hardest reference value
c. Talc is the softest reference value
d. Enamel is 7-8 on the scale
e. Dentin is 3-4 on the scale
Which one has higher Moh’s Rating?
Mechanical Properties
• Elastic & plastic behavior
• Beyond the stress limit of the elastic limit
• Ultimate strength: highest stress reached before
fracture
• Elongation: % change in length up to the point of
fracture
Mechanical Properties
• Elastic & plastic behavior
• Brittle materials: <10% elongation at fracture
• Ductile materials: >10% elongation at fracture
• Toughness: area under the stress-strain curve up to
the point of fracture
Mechanical Properties
• Time-dependent behavior
• Strain rate sensitivity: the faster a stress is applied, the
more likely a material is to store the energy elastically
and not plastically
• Creep: strain relaxation with time in response to a
constant stress, such as dental wax deforming because
of built-in stresses created during cooling
• Stress relaxation: with time in response to a constant
strain
• Fatigue: failure caused by cyclic loading
NBQ
What is the major component in most dental waxes?
a. Carnauba wax
b. Colorant
c. Paraffin
d. Rosin
e. Beeswax
NBQ
What is the major component in most dental waxes?
a. Carnauba wax
b. Colorant
c. Paraffin
d. Rosin
e. Beeswax
Handling Properties
• Base and filling
• High viscosity
• Set fast
• Cement
• Low initial viscosity
• Fluid
• Sufficient work time
• Temp and moisture effect
• Work time
• Set time
• Strength
Dental Hygiene
Amalgam
• An alloy of mercury (50%) with silver, copper, tin, zinc
• Silver, a base metal, is susceptible to corrosion
• Copper added to minimize corrosion (gamma II phase
eliminated)
• High CU cuts down on corrosion
• Advantages
• Durable
• Similar compressive strength to enamel
• Resistant to wear
• Relatively inexpensive
Amalgam
• Disadvantages
• Unattractive
• High thermal conductivity: like gold
• Dimensionally unstable: Creep
• Tarnish: from Sulfur
• Delayed expansion if contaminated by saliva
• Requires tooth support
• Fracturable by excessive occlusion
• Susceptible to galvanism when new
• May need base in deep preps
• Expansion: like impression material
• Brittle
Amalgams
• Avoid overhang formation by:
• Use a properly placed band or wedge
• Detect overhang with explorer
• Mixing can be an issue
• Undermix: crumbly
• Overmix: difficult to remove
Amalgam Polishing
• Polish and Finish
• Flash: polish
• Overcontoured: not polish
• Undercontoured: not polish
• Abrasion rate of dentin: 5-6x faster than abrasion rate enamel
• Steps
1.
2.
3.
Brownie
Greenie
Super-Greenie
• Steps
1.
2.
3.
4.
Pumise
Rinse
Tin-Oxide
Rinse
NBQ
Which of the following could be used as a final polish for
gold, ceramic, amalgam, or composite restorations in the
mouth?
a.
b.
c.
d.
Rouge
Pumice
Tin oxide
Prophy-jet
NBQ
Which of the following could be used as a final polish for
gold, ceramic, amalgam, or composite restorations in the
mouth?
a.
b.
c.
d.
Rouge
Pumice
Tin oxide
Prophy-jet
Amalgam Polishing
• Move from coarse to fine agents when polishing (bur,
pumice, tin oxide)
• Polishing can reduce rate of corrosion (less surface area)
• Final polish in the mouth is tin oxide
• Use light touch with water and short bursts to avoid
odontoblast damaging heat
NBQ
With time, dental materials wear. Amalgam fillings can lose
their marginal integrity to allow the penetration of fluid
between the restoration and tooth surface. This
phenomenon is called:
a. Imbibition
b. Syneresis
c. Percolation
d. Wetting
e. Creep
NBQ
With time, dental materials wear. Amalgam fillings can lose
their marginal integrity to allow the penetration of fluid
between the restoration and tooth surface. This
phenomenon is called:
a. Imbibition
b. Syneresis
c. Percolation
d. Wetting
e. Creep
NBQ
Which of the following phases in dental amalgam
restorations has the best mechanical properties and
highest corrosion resistance?
a. Ag-Sn
b. Cu-Sn
c. Sn-Hg
d. Ag-Hg
e. None of the above
NBQ
Which of the following phases in dental amalgam
restorations has the best mechanical properties and
highest corrosion resistance?
a. Ag-Sn
b. Cu-Sn
c. Sn-Hg
d. Ag-Hg
e. None of the above
NBQ
• Which of the following is the criterion for a failed high
copper dental amalgam restoration?
a. Accumulation of black or green tarnish on the
exposed surface
b. Marginal ditching along occlusal margins
c. Creep of the restoration out of the oral cavity
preparation in proximal areas
d. Wear facets along the occlusal contact areas
e. None of the above
NBQ
• Which of the following is the criterion for a failed high
copper dental amalgam restoration?
a. Accumulation of black or green tarnish on the
exposed surface
b. Marginal ditching along occlusal margins
c. Creep of the restoration out of the oral cavity
preparation in proximal areas
d. Wear facets along the occlusal contact areas
e. None of the above
NBQ
An improperly carved occlusal amalgam restoration may
result in:
a.
b.
c.
d.
Fracture of the filling or the tooth
Tenderness of the tooth to percussion
Tooth hypersensitivity to temperature changes
All the above
NBQ
An improperly carved occlusal amalgam restoration may
result in:
a.
b.
c.
d.
Fracture of the filling or the tooth
Tenderness of the tooth to percussion
Tooth hypersensitivity to temperature changes
All the above
Composites
• Mixture of 2 or more materials that has properties
superior to any single component
• Ceramic reinforcing filler particles in a monomer
matrix that is converted to a polymer on setting
• Composite resins are tooth-colored for ant or post
• Composed mainly of organic resin matrix and
inorganic fillers joined together by a silane coupling
agent
• Common filler particles: silicates, quartz, glass
• Barium or strontium usually added for radiopacity
• Also added are initiators and accelerators that cause
the material to set
• Pigments give the material color
Composites
• Resins
• Bis-GMA
• These resins are thick liquids made up of two or
more organic molecules
• To reduce viscosity and allow the loading of filler
particles, a low molecular weight monomer is added
• Flowable
• Low-viscosity, light-cured resins that are lightly filled
• Flow readily and can be delivered directly into the
preparation by small needles on syringes
Composite Selection
• Microfill or micro-hybrids
• Anterior Class III, IV, V restorations
• Micro-hybrids
• Class I, II, III, IV, V
Composite Reaction
• Free radical polymerization – monomers + initiators +
accelerators → polymer molecules
• Initiators: start polymerization by decomposing & reacting
w/monomer
• Benzoyl peroxide typically used in SC systems
• Camphorquinone typically used in VLC systems
• Accelerators: speed up initiator decomposition
• Different amines used for accelerating initiators in SC
and VLC systems
• Retarders or inhibitors: prevent premature polymerization
Composites
• Components
• Filler particles
• Colloidal silica, crystalline silica (quartz), silicate
glasses, various partial sizes
• Matrix
• Bis-GMA with lower-molecular-weight diluents that coreact during polymerization
• Ring-opening monomers
• Coupling agent
• Silane
• Chemically bonds the surface of the filler particles to
the polymer matrix
Composites
• Filler particles
• Added to the organic resins to make them stronger
• Control handling characteristics
• Help to reduce shrinkage
• Fillers used in composite resins are made up of inorganic
particles such as quartz, silica, and glass
• 3 Types
1. Macrofilled
2. Microfilled
3. Hybrid
• Coupling Agents
• Used to provide a stronger bond between the organic fillers
and the resin matrix
• Made of silane, which reacts with the surface of the inorganic
filler
Composites
• Handling characteristics, clinical application and classification
determined by filler particle size
1. Macrofill: 10-100 microns (marshmallows)
2. Midfill: 1-10 microns (jelly beans)
3. Minifill: 0.1-1 micron (red hots)
4. Microfill: 0.01-0.1 micron (nerds)
5. Nanofill: 0.001 micron (sugar)
6. Hybrid: blend of micro and midfill (0.6 micron avg, 3.5
microns largest particle size) (jelly bean and nerds)
7. Nano-filled micro-hybrid: blend of micro, midi, nanofill
particles (jelly bean, nerds, sugar)
Composite Key Points
• Microfills popular due to high polish-ability and ease of
•
•
•
•
•
•
handling, but require support
Hybrids popular due to combined strength and beauty
Nanofills increase surface area and, therefore, bond strength
• Nanofills increase polish-ability
Rubber dam isolates field and prevents salivary
contamination
Light cured (unmixed) composites less porous than self
cured (mixed)
Polish with tin oxide (or diamond polishing paste), not coarse
pumise
Detect overhang with an explorer
Composites
3 Types (see Dental Materials PPTs)
1.
2.
3.
Chemical cure
Light cure
Dual cure
Composite Finish & Polish Key Points
• Remove the oxygen-inhibited layer
• Use stones, carbide burrs, diamonds for gross reducation
• Use multi-fluted carbide burs or special diamonds for fine
•
•
•
•
reduction
Use aluminum oxide strips or discs for finishing or rubber
points, cups and discs
Use fine aluminum oxide or diamond finishing pastes
Microfill and nanofill composites develop smoothest finish
because of small size of filler particles
Keep in mind hat liquid polishes provide short-term
smooth surface coatings
NBQ
A benefit of light-cured composites over self-cured
composites is:
a.
b.
c.
d.
That they require no mixing
That they have reduced porosity
A&B
None of the above
NBQ
A benefit of light-cured composites over self-cured
composites is:
a.
b.
c.
d.
That they require no mixing
That they have reduced porosity
A&B
None of the above
NBQ
The material of choice for a Class VI restoration would be:
a. Amalgam
b. Composite
c. Glass ionomer
d. A cast metal restoration
NBQ
The material of choice for a Class VI restoration would be:
a. Amalgam
b. Composite
c. Glass ionomer
d. A cast metal restoration
NBQ
Seen in a radiograph, a composite restoration might
appear:
a. Radiopaque
b. Radiolucent
c. Less radiopaque than an alloy
d. All the above
NBQ
Seen in a radiograph, a composite restoration might
appear:
a. Radiopaque
b. Radiolucent
c. Less radiopaque than an alloy
d. All the above
NBQ
In dental composites, increasing the powder to liquid ratio
of components produces:
a. Lower strength
b. Higher modulus
c. Increased water absorption
d. Improved toughness
e. Increased solubility
NBQ
In dental composites, increasing the powder to liquid ratio
of components produces:
a. Lower strength
b. Higher modulus
c. Increased water absorption
d. Improved toughness
e. Increased solubility
Casting Alloys
• Inlay, onlay, crown, bridges
• Precious metals
• Au, Pt, Pd, Ag, Ir, Rh, Rd
• Noble or immune-corrosion-resistant element or alloy
• Base or active: corrosion-prone alloy
• Passive: corrosion-resistant because of surface oxide film
Casting Alloys
• Classification
1.
2.
3.
4.
5.
High-gold alloys
• Over 75%wt gold or other noble metal
Medium-gold alloys
• 25-75%wt gold or other noble metal
Low-gold alloys
• Under 25%wt gold or other noble metal
Titanium alloys
• 90-100% titanium: passive because of TiO2 oxide film
Gold-substitute alloys do NOT contain gold
• Palladium-silver alloys: passive because of mixed oxide film
• Cobalt-chromium or nickel-chromium alloys: passive
because of Cr2O3 oxide film
Porcelain
• Structure: ionic bonds, oxides, amorphous (gloss, mica)
or crystalline(Al-oxide, leucite)
• Mixture of
1.
2.
3.
Feldspar
Quartz
Kaolin Clay
• PFM: uses non-greening silvery alloy
• Properties
• Best esthetics of all
• Hard: good wear resistance
• Abrasive antagonist: wear of opposing teeth
• Insulator
• Chemically: biocompatible, stain resistant, non-bleachable
• Low contact angle
• Surface oxidized
NBQ
The difference between an inlay and an onlay is that:
a.
b.
c.
d.
There is no difference between an inlay and an onlay
An inlay is made of silver and an onlay is made of gold
An inlay should not exceed ½ the intercuspal distance, while an
onlay covers the cusps
An onlay should not exceed ½ the intercuspal distance while an
inlay covers the cusps
NBQ
The difference between an inlay and an onlay is that:
a.
b.
c.
d.
There is no difference between an inlay and an onlay
An inlay is made of silver and an onlay is made of gold
An inlay should not exceed ½ the intercuspal distance, while an
onlay covers the cusps
An onlay should not exceed ½ the intercuspal distance while an
inlay covers the cusps
Bonding Agents
• Dental resin (BIS-GMA or urethane dimethacrylate) which
establish micro-mechanical retention with enamel and dentin
by adapting t relief areas created by conditioning with 37%
phosphoric acid
• Steps:
• 15-20sec etch, rinse, dry, air-thin, polymerize
• Phosphoric acid application increases enamel and dentin surface area
• Polymerization typically activated by fiber-optic light
• Light-activated polymerization allows flexible working time
• Polymerization initiators typically benzoyl peroxide or a tertiary amine
• Bonding failures
• If contamination at any step of the process = re-etch
• Saliva, oils
NBQ
Which of the following procedures is standard for
conditioning tooth structure before bonding procedures for
composite restoration?
a. Phosphoric acid conditioning of enamel only
b. Phosphoric acid conditioning of dentin only
c. Phosphoric acid conditioning of enamel and
dentin
d. EDTA conditioning of enamel and dentin
e. Polyacrylic acid conditioning of enamel and
dentin
NBQ
Which of the following procedures is standard for
conditioning tooth structure before bonding procedures for
composite restoration?
a. Phosphoric acid conditioning of enamel only
b. Phosphoric acid conditioning of dentin only
c. Phosphoric acid conditioning of enamel and
dentin
d. EDTA conditioning of enamel and dentin
e. Polyacrylic acid conditioning of enamel and
dentin
NBQ
Strong bonding to dentin requires:
a. Extensive conditioning
b. Very dry dentin
c. Pre-application of Chlorhexidine
d. Scrubbing during conditioning
e. Hybrid layer formation
NBQ
Strong bonding to dentin requires:
a. Extensive conditioning
b. Very dry dentin
c. Pre-application of Chlorhexidine
d. Scrubbing during conditioning
e. Hybrid layer formation
Pit and Fissure Sealants
• Barrier to protect occlusal surface of teeth from bacterial
assault by sealing anatomically unprotected structure with
resin
• Steps
• Pumise, rinse, etch, rinse, dry, apply, polymerize
• Re-etch if enamel lacks “frosty” appearance
• Retention is mechanical; can check with explorer after
polymerization
• Greatest influence on retention is operator technique
• Proper tooth selection and preparation
• Proper isolation, etch, rinse, dry
• Proper placement
• Proper occlusion
Question
What is the #1 cause of sealant non-retention?
a.
b.
c.
d.
Saliva contamination
Etch was not thoroughly rinsed
Tooth was not dried long enough prior to sealant placement
Patient compliance
Answer
What is the #1 cause of sealant non-retention?
a.
b.
c.
d.
Saliva contamination
Etch was not thoroughly rinsed
Tooth was not dried long enough prior to sealant placement
Patient compliance
Sealant Structure
• Components
• Monomer: Bis-GMA
• Initiator
• Benzoyl peroxide: Self-Cured
• Camphorquinone: Light-Cured
• Accelerator: amine
Sealant Structure
• Opaque filler
• 1% titanium dioxide or other colorant
• Reinforcing filler
• Silicate glass if used at all, most time not needed
because wear resistance not required within
pits/fissures
• Fluoride
• May be added for slow release
• Reaction
• Free radical
Sealant Properties
• Physical: wetting
• Low-viscosity sealants wet acid-etched tooth structure the
best
• Mechanical
• Wear resistance should not be too great because seal
should be able to wear off the self-cleaning areas of tooth
• To prevent loss – protect seals during polishing with airabrasion
• Biological: no problems
• Clinical efficacy
• Effectiveness is 100% if retained
• Resist attacks from topical fluorides
Sealant
• Purpose of sealant
• Mechanical or Physical barrier to “seal off” the pit or fissure
• Prevent oral bacteria and their nutrients from collecting within
the pit or fissure to create the acid environment necessary
for the initiation of dental caries
• Fill the pit or fissure as deep as possible and provide tight
smooth margins at the junction with the enamel surface
• Material worn or cracked away on the surface around the pit
or fissure, the sealant in the depth of the micropore can
remain and provide continued protection while sealant
material is added for repair and to reseal the enamel/sealant
junction
Sealant
Purpose of acid etch
• Produce irregularities or micropores in the
enamel
• Allows the liquid resin to penetrate into the
micropores and create a bond or mechanical
locking
(Adapted with permission from Buonocore MG, Matsui A, Gwinnett AJ. Penetration of resin
dental materials into enamel surfaces with reference to bonding. Arch Oral Biol. 1968
Jan;13(1):61–70.)
A 7-year old patient with deep fissures on his 6-year molars
comes to you for sealants. The sealant system you use
requires the acid-etch technique. This technique:
a.
b.
c.
d.
e.
Conserves tooth structure
Reduces microleakage
Improves esthetics
Provides micro-mechanical retention
All of the above
A 7-year old patient with deep fissures on his 6-year molars
comes to you for sealants. The sealant system you use
requires the acid-etch technique. This technique:
a.
b.
c.
d.
e.
Conserves tooth structure
Reduces microleakage
Improves esthetics
Provides micro-mechanical retention
All of the above
Sealant Material Classification
• Majority made of Bis-GMA (bisphenol A-glycidyl
methylacrylate)
• Techniques of application vary slightly among available
products
• 5 types of sealants
1. Filled: increase bond strength and increase resistance
to abrasion and wear
• Fillers are glass or quartz particles
• Viscosity of material increased
• Flow into depth of a fissure varies
2. Unfilled: clear, do not contain particles
• Less resistant to abrasion & wear
• May require occlusal adjustment when placed
Sealant Material Classification
• 5 types of sealants
3. Fluoride-releasing filled: enhance caries
resistance
•Action: remin of incipient caries at base of pit
or fissure
4. Glass ionomer
•Salivary control not a critical factor
•Ideal for teeth when moisture control an issues
5. Calcium phosphate
•Promotes remin
Fluoride in Glass Ionomer: Mosby’s
Sealant Materials Classification
• Self-cured or autopolymerized
•
•
•
•
Preparation: the material is supplied in two parts
When the two are mixed they quickly polymerize (harden)
Advantages: no special equipment required
Disadvantages: mixing required; working time limited
because polymerization begins when the material is mixed
• Visible light-cured or photopolymerized
• Preparation: the material hardens when exposed to a
special curing light
• Advantages: no mixing required; increased working time
due to control over start of polymerization
• Disadvantages: extra costs and disinfection time required
for curing light, protective shields, and/or glasses
Question
• A patient receives 4 sealants at their 6 month recare
appointment. At the next recare appoint, the hygienist
notices only 2 of the 4 sealants are still in place. All of the
following errors may account for this retention problem
except one. Which one is the EXCEPTION?
a.
b.
c.
d.
e.
The etch was not thoroughly rinsed off the tooth prior to sealant
placement
A dry field was not maintained and the tooth surface was
contaminated by saliva after etching
The patient ate some candy after the placement of the sealants
The air supply to the A/W syringe was contaminated
The tooth was not thoroughly dried prior to placement of the
sealants
Answer
• A patient receives 4 sealants at their 6 month recare
appointment. At the next recare appoint, the hygienist
notices only 2 of the 4 sealants are still in place. All of the
following errors may account for this retention problem
except one. Which one is the EXCEPTION?
a.
b.
c.
d.
e.
The etch was not thoroughly rinsed off the tooth prior to sealant
placement
A dry field was not maintained and the tooth surface was
contaminated by saliva after etching
The patient ate some candy after the placement of the sealants
The air supply to the A/W syringe was contaminated
The tooth was not thoroughly dried prior to placement of the
sealants
Question: Match the Following
• Initiator
• Accelerator
• Monomer
a. Camphorquinone
b. Amine
c. Bis-GMA
Answer: Match the Following
• Initiator
• Accelerator
• Monomer
• A, B, C
a. Camphorquinone
b. Amine
c. Bis-GMA
Bonding Agents
• Conditioning agents: mineral (phosphoric acid), organic
acid, acrylic monomer acid
• Priming agent: resin and monomer in alcohol, acetone,
water
• Bonding agents: Bis-GMA or UDMA monomers
• Reaction
• Bonding occurs primarily by intimate micromechanical
retention, with the relief created by the conditioning step
• Chemical bonding possible but not recognized as
contributing significantly to the overall bond strength
• Insert Mosby’s page 490
Cement Liners
• Generally used to seal dentin or medicate the dental
pulp (seal/medicate)
• Includes:
1. Varnish: seal dentin tubules, replaced by bonding
agents
2. Calcium hydroxide: stimulates reparative dentin
formation
3. Zinc-Oxide/Eugenol: sooths pulp, oily
4. Resin-modified glass ionomer: seals dentin
tubules and releases fluoride
NBQ
Which of the following is the LEAST effective method of
sealing a cavity preparation?
a. Copalite
b. Dentin bonding system
c. amalgam bonding system
d. Glass ionomer liner
e. Bonded composite cement
NBQ
Which of the following is the LEAST effective method of
sealing a cavity preparation?
a. Copalite
b. Dentin bonding system
c. amalgam bonding system
d. Glass ionomer liner
e. Bonded composite cement
NBQ
Which one of the following cavity preparation liners
provides no practical thermal insulation for the pulp?
a. Glass ionomer liner
b. Zinc phosphate cement base
c. Polycarboxylate cement base
d. Calcium hydroxide liner
e. Dentin bonding systems
NBQ
Which one of the following cavity preparation liners
provides no practical thermal insulation for the pulp?
a. Glass ionomer liner
b. Zinc phosphate cement base
c. Polycarboxylate cement base
d. Calcium hydroxide liner
e. Dentin bonding systems
Cement Bases
• Used to provide thermal insulation or mechanical
protection for the dental pulp (insulate/protect)
• Included all cements, because cements are poor
thermal conductors, and have adequate
compressive strength
• Classifications
• Glass ionomer cement bases
• Resin-modified glass ionomer: light-curing
compositions
Cements
• Used to affix a restoration to tooth structure, or as a base
• Types:
Zinc phosphate cement
• Exothermic reaction on mixing: use cool glass slab
• Mechanical interlock between tooth and casting
2. Polycarboxylate cement
• High chemical affinity for enamel
• Powder mixed with polyacrylic acid
3. Glass ionomer cement
• Binds to dentin
• Releases fluoride
• Coefficient of thermal expansion approximates tooth
structure
• Can be used as a Class V restorative material
1.
Cements
• Used to affix a restoration to tooth structure, or as a base
• Types:
4.
5.
6.
Resin cement
• Tooth colored to affix esthetic restorations lie porc laminate veneers
and tooth colored inlays, onlay or crowns and clear ortho brackets
• Also used for luting etched metal retainers such as resin-bonded
bridges and prefab endodontic posts
Hybrid cement
• Resin-modified glass ionomer
• Seals dentin effectively to minimize sensitivity (unfilled resin/bonding
agents)
• Releases fluoride (glass ionomer)
Zinc-oxide/eugenol cement
• Commonly used for temporary cementation
• Mixed putty-like to cement a temporary aluminum shell crown
• Orange solvent typically used to clean ZOE-contaminated
instruments
MATERIAL
USES
Zinc-Phosphate
Cement
Ortho, final cementation
Zinc-Oxide Eugenol
IRM, bacteriostatic, olive of cloves
Endo, dressings, weakest base
Zinc-Polycarboxylate
Cement acid
Restorations, final cementation, strong
luting agent
Glass Ionomer
Release fluoride
Restorations, resin, final cementation
Adhere to tooth by chelation Ca by
ionized polyacrylate
Hybrid Glass Ionomer
Restorations, final cementation
Strongest base, luting agent
Ca-Hydroxide
Base, Liner
Secondary/reparative dentin, not 4
cement, use on anything
Cements
• Root canal sealers
• Cementing of silver cone or gutta-percha point
• Paste filling material
• Classification
• Zinc oxide-eugenol cement types
• Noneugenol cement types
• Therapeutic cement types
• Flowable cement types
Mosby
Cements
• Gingival tissue packs
• Provide temporary displacement of gingival tissues
• Slow setting zinc oxide-eugenol cement mixed with cotton twills for
texture & strength
• Surgical dressings
• Gingival covering after perio surgery
• Next slide
• Orthodontic cements
• Cementing of ortho bands
• Composite: luting cements, bonding agents
NBQ
The largest component of zinc phosphate, poylcarboxylate,
and ZOE dental cement is:
a. Water
b. Silica
c. Mineral acid
d. Eugenol
e. Zinc oxide
NBQ
The largest component of zinc phosphate, poylcarboxylate,
and ZOE dental cement is:
a. Water
b. Silica
c. Mineral acid
d. Eugenol
e. Zinc oxide
NBQ
Glass ionomer cement may chemically adhere to tooth
structure as a result of what cement?
a. Aluminum ions release from the particles of
cement powder
b. Chelation of calcium by ionized polyacrylate
groups
c. Electrostatic attraction to aluminosilicate powder
d. Hydration of the set of materials
e. Fluoride ion release
NBQ
Glass ionomer cement may chemically adhere to tooth
structure as a result of what cement?
a. Aluminum ions release from the particles of
cement powder
b. Chelation of calcium by ionized polyacrylate
groups
c. Electrostatic attraction to aluminosilicate powder
d. Hydration of the set of materials
e. Fluoride ion release
Types of Dressings
• 2 Groups
1. With eugenol
2. Without eugenol
• Today now classified as chemical-cured and
visible-light-cured materials
• Available as ready-mix, paste-paste, paste-gel
preps
Types of Dressings #1
• Zinc oxide with eugenol
• Ingredients
• Powder
• Zinc oxide, powdered rosin, and tannic acid
• Past: some formulas used asbestos fiber as a binder =
health hazard = no longer an acceptable ingredient of
dressings
• Liquid
• Eugenol, with oil (such as peanut or cottonseed)
• Thymol
• Examples: Wards Wondrpack and Kirkland Periodontal Pack
Chemical-Cured Dressing #2
• 2 Examples
• PerioCare Ingredients
• Paste-gel mix
• Paste: : zinc oxide, magnesium oxide, calcium hydroxide, and vegetable
oils
• Gel: resins, fatty acids, ethyl cellulose, lanolin, calcium hydroxide
• Coe-Pak
• Paste-paste mix
• Base: rosin, cellulose, natural gums and waxes, fatty acid, chlorothymol,
zinc acetate, alcohol
• Accelerator: zinc oxide, vegetable oil, chlorothymol, magnesium oxide,
silica, synthetic resin, and coumarin
• Available in hard & fast set
Chemical-Cured Dressing #2
• Advantages
• Consistency: Pliable, easy to place with light pressure
• Smooth surface: comfortable to patient; resists biofilm and
debris deposits
• Taste: acceptable
• Removal: easy, often comes off in one piece
Other Dressings #2
• Visible light-cured dressing
• Barricaid: syringe for direct application or mixing pad for
indirect
• Basic ingredients
• Gel ingredients include polyester urethane dimethacrylate
resin, silanated silica, visible light-cured photoinitiator and
accelerator, stabilizer, and colorant
• Advantages
• Color: more like gingiva than most other dressings
• Setting: does not begin until activated by the light-curing
unit. Exposure before placement should be limited as
daylight in a room may begin the activation process
• Removal: easy, often comes off in one piece
Ortho Removal / Polishing
• Tungsten carbide finishing bur
• Scale
• Aluminum oxide discs: polish
• Brownie
• Greenie
Implant Key Points
• Biocompatible titanium allow prosthesis used to replace
•
•
•
•
missing teeth
Prosthesis may be cylindrical, or have a blade shape
Can use electric tb & mouthrinse without damaging
implant
No metal instruments, air polisher ok
Leading cause of failure is mobility
• Lack of osseointegration or inadequate bone
• Contra-indications to implant placement
• Inadequate bone
• Uncontrolled periodontal disease, diabetes
• Smoking
• Infection
Material Types
• Metallic-titanium
• Uncoated or coated
• Stainless steel
• Chromium/cobalt
• Polymeric: PMMA
• Ceramic
• Hydroxyapatite, carbon, sapphire
Attachment Designs
• Bioactive surface retention by osseo-inetgration
• Integration of bone with implant
• Most favored type of attachment
• Nonactive porous surfaces for micro-mechanical retention by
•
•
•
•
osseo-integration
Nonactive, nonporous surface for ankylosis by osseointegration
Gross mechanical retention designs
• Threads, screws, channels, transverse holes
Fibro-integration by formulation of fibrous tissue capsule
Combo of above designs
Properties
• Physical
• Should have low thermal and electrical conductivity
• Chemical
• Should be resistant to electrochemical corrosion
• Do not expose surfaces to acids: APF fluorides
• Biologic
• Depends on osseo-integration and epithelial attachment
• Mechanical
• Should be abrasion resistant and have a high modulus
• Avoid scratching with metal hygiene instruments
Types
Endosseous implant
• Most widely used
• Placed into alveolar or basal bone or both
2. Subperiosteal implant
• Placed on the surface of bone beneath the periosteum
• Complete arch or unilateral
3. Trans-osteal implant
• Placed through the alveolar bone
1.
1. Endosseous
•
Placed fully within the bone to replace a single tooth or
provide support for the replacement of complete or partial
loss of teeth
• Successful tooth replacement = osseointegration
• Direct bone anchorage to an implant body
• Early forms (endosteal): blade or plate form
• Current forms (endosseous): “root form” or cylindrical;
can be threaded, smooth, perforated, or solid
• Plasma-sprayed titanium
1. Endosseous
•
Placement
• Immediately after extraction or after healing for a couple
months
• Implant is placed in bone and left covered by a
periodontal flap or healing cap for several months while
the implant bonds with the bone
• The abutment post is then exposed through the soft
tissue at a second-stage surgical procedure
• Placement of the crown or prosthesis follows
2. Subperiosteal
• Titanium or vitallium (cobalt-chromium-molybdenum)
• Process
• Surgical flap is used to reflect mucosal tissues and to expose the
underlying bone
• Impression is made of the bony ridge
• Metallic unit is cast
• Usually, four posts protrude into the oral cavity to hold the complete
denture
• Computer-assisted tomography design and manufacturing from which
approximate casts of the maxilla or mandible made
• Implant is designed on this replica
3. Trans-osteal
• Penetrates both cortical plates and passes through the full
thickness of the alveolar bone
• Also known as a mandibular staple implant or staple bone
implant
• Stainless steel, ceramic-coated materials, and titanium alloy
• Metal plate is fitted to the inferior border of the mandible
• 5-7 pins extending toward the occlusal surface
• 2 terminal pins protrude into the oral cavity to hold the overdenture
• Pins connected by a crossbar
• Uses: Atrophic edentulous mandible, Congenital or traumatic
deformity of the mandible
Impressions
• Alginate: low tear strength, casts, opposing arches,
shrink: pour up within 15min, cheap, condensation
• Silicone impression: polyvinyl, polyether
Impression Types
1.
2.
3.
4.
Rigid (inelastic)
• Plaster, Type I Gypsum (occlusal record)
• Compound (border mold custom tray)
• Zinc-oxide/eugenol (final impression, full denture)
Flexible (elastometric): general purpose (next slide)
1) Polysulfide elastomer
2) Silicone elastomer
3) Polyether elastomer
4) Polyvinyl siloxane
5) PE-VPS hybrid
Flexible hydrocolloid
1) Agar-Agar (Reversible hydrocolloid)
2) Alginate (Irreversible hydrocolloid)
Precision for PROS
1) Addition silicones: contain surfactants to make surface wetting
easier
2) Polyethers: more hydrophilic
Impressions
Flexible (elastometric)
• Polysulfide Rubber
Messy, smelly, must be poured same day
• Polyether Rubber
Relatively rigid, good tissue detail
Unstable n presence of moisture (will distort if
left wet)
• Silicone Rubber (condensation rxn silicone)
Putty-like, rarely used
• Vinylpolysiloxane (addition rxn silicone)
Tasteless, odorless
Stable, strong, accurate
Easily mexed
Capable of multiple pours
Impressions
Flexible Hydrocolloid
1) Reversible Hydrocolloid (AGAR)
• Undergoes a physical rxn only
• Sol-gel state is temperature dependent
• Solidification by cold called GELATION
• Popular for multiple preps but UNSTABLE
• Susceptible to IMBIBITION and SYNERESIS
2) Irreversible hydrocolloid (ALGINATE)
• Undergoes a CHEMICAL rxns
• Not temp dependent, but setting can be delayed by
cold water or accelerated by warm water
• Popular choice for study models but unstable
• Susceptible to IMBIBITION and SYNERESIS
• Aerate (fluff) to prevent setting/compaction of powder
NBQ
All of the following are flexible impression materials
EXCEPT:
a. Alginate
b. Polyether
c. Polyvinyl siloxane
d. Polysulfide
e. ZOE
NBQ
All of the following are flexible impression materials
EXCEPT:
a. Alginate
b. Polyether
c. Polyvinyl siloxane
d. Polysulfide
e. ZOE
NBQ
Which ONE of the following impression materials does not
set via a chemical reaction?
a. Agar-agar hydrocolloid
b. ZOE
c. Polysulfide
d. Polyether
e. Polyvinyl siloxane
NBQ
Which ONE of the following impression materials does not
set via a chemical reaction?
a. Agar-agar hydrocolloid
b. ZOE
c. Polysulfide
d. Polyether
e. Polyvinyl siloxane
NBQ
Which ONE of the following impression materials may be
machine mixed?
a. Alginate
b. ZOE
c. Polyether
d. Silicone
e. Polysulfide
NBQ
Which ONE of the following impression materials may be
machine mixed?
a. Alginate
b. ZOE
c. Polyether
d. Silicone
e. Polysulfide
Mosby
Impression Material
• Most contain fillers to control shrinkage and a matrix
• Physical rxn
• Cooling causes reversible hardening
• Chemical rxn
• Irreversible rxn during setting
• Mixing
• Bowl
• Thermoplastic materials not mixed
• Hand mix: paste-paste types on a pad
• Auto mix: paste-paste types through a nozzle on auto-mixing gun
• Machine: through a nozzle using small machine (Penta-mix 2)
Gypsum and Casts
• Undergoes expansion as it sets
• The more water needed = greater setting expansion
(dimensional change) and lower compressive strength of final
product
• Uses
• Investment of wax patters, models and impressions
• Ca-sulfate hemihydrate/dihydrate mineral
• Will expand when set
• Brittle
• Humidity, not temp affecting
• Gypsum materials
• Plaster: low viscosity, density
• Lab stone
• Die stone: high viscosity, density, strongest/hardest
Gypsum and Casts
• Properties
• Excellent thermal and electrical insulator
• Dense
• Excellent accuracy
• Plaster: 0.20%
• Stone: 0.10%
• Diestone: 0.05%
• High-expansion diestone: 0.20%
• Good reproduction of fine detail in hard/soft tissues
• Chemical: heating will reverse the reaction. Wet material during
grinding/cutting to prevent heating
• Poor resistance to abrasion (polymer can be added to improve
resistance)
Gypsum
• Gypsum grade / Quality of product determined by
refinement
• Plaster: Type II Gypsum (beta-Ca hemi-hydrate)
• Irregular, porous particle
• Undergoes high setting expansion and has low compressive strength
(requires lots water to reconstitute)
• Stone: Type III Gypsum (alpha-Ca sulfate hemi-hydrate)
• Less irregular, less porous particle
• Undergoes low setting expansion
• Higher compressive strength (requires less water to reconstitute)
• Diestone: Type IV Gypsum ( alpha-Ca sulfate hemi-hydrate)
• Contains additive to make more durable and wear resistant
• Also called improved stone
• Highest compressive strength
Gypsum
• Material selection dependent upon strength and
dimension accuracy desired:
• Ortho model = plaster (easy to pour)
• Study model = stone (more accurate and wear
resistant)
• Crown and bridge = die or model improved diestone
(accurate and most wear resistant)
NBQ
Gypsum powder that is to be reacted to form working casts
is composed primarily of:
a. Aluminosilicate glass
b. Calcium sulfate hemihydrate
c. Calcium carbonate
d. Sodium fluoride
e. Calcium phosphate
NBQ
Gypsum powder that is to be reacted to form working casts
is composed primarily of:
a. Aluminosilicate glass
b. Calcium sulfate hemihydrate
c. Calcium carbonate
d. Sodium fluoride
e. Calcium phosphate
NBQ
What is the major difference between plaster and stone
powder?
a. Degree of water hydration
b. Color
c. Different chemical reactions on setting
d. Different powder particle packing
e. Different setting times
NBQ
What is the major difference between plaster and stone
powder?
a. Degree of water hydration
b. Color
c. Different chemical reactions on setting
d. Different powder particle packing
e. Different setting times
Mosby
Gypsum Summary
• More water = greater expansion and less strength
• Plaster softer, less accurate and lower in compressive strength
•
•
•
•
than stone which is softer and less accurate and lower in
compressive strength than improved stone or diestone which is the
hardest, most accurate and has the highest compressive strength
of all
Modification of working time
1. Add potassium sulfate to accelerate set
2. Mix with arm water to accelerate set
3. Add borax to slow set
Water should be measured and gypsum should be weighed to mix
Air incorporated into the mix will result in surface voids
Model trimmed perpendicular to midline between centrals
Dentures
• Acrylic resins, prosthetic polymers
• Curing: powder(initiator) + liquid(inhibitor)
• Heat
• Cold
• Light
• Exothermic Rxn
• Properties
• Thermal contraction and expansion
• Low stiffness
• Low impact strength
• Insulator: not feel temp. food
• Water-absorption: no hot water to help keep from changing shape
• Abrade easily
Dentures
• Teeth: porcelain or acrylic resin
• Liners: for people with soft tissue irritation, adding
plasticizer
• Cleaners: Na-hypochlorite
• See HPDP lecture