BOARD REVIEW DH227DENTAL MATERIALSLisa 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

mixing

b. Time elapsed from the beginning of mixing until the beginning of setting

c. Time elapsed from the beginning of the working interval until the end of the setting interval

d. The working interval

e. 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

mixing

b. Time elapsed from the beginning of mixing until the beginning of setting

c. Time elapsed from the beginning of the working interval until the end of the setting interval

d. The working interval

e. 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)1. Chemical

2. Electrochemical

3. Corrosion potential

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

• Steps1. Brownie

2. Greenie

3. Super-Greenie

• Steps1. Pumise

2. Rinse

3. Tin-Oxide

4. Rinse

NBQ

Which of the following could be used as a final polish for gold, ceramic, amalgam, or composite restorations in the mouth?

a. Rouge

b. Pumice

c. Tin oxide

d. 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. Rouge

b. Pumice

c. Tin oxide

d. 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. Fracture of the filling or the tooth

b. Tenderness of the tooth to percussion

c. Tooth hypersensitivity to temperature changes

d. All the above

NBQ

An improperly carved occlusal amalgam restoration may result in:

a. Fracture of the filling or the tooth

b. Tenderness of the tooth to percussion

c. Tooth hypersensitivity to temperature changes

d. 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 co-

react 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. Macrofilled2. Microfilled3. 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

Composites3 Types (see Dental Materials PPTs)

1. Chemical cure2. Light cure3. 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. That they require no mixing

b. That they have reduced porosity

c. A&B

d. None of the above

NBQ

A benefit of light-cured composites over self-cured composites is:

a. That they require no mixing

b. That they have reduced porosity

c. A&B

d. 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. High-gold alloys• Over 75%wt gold or other noble metal

2. Medium-gold alloys• 25-75%wt gold or other noble metal

3. Low-gold alloys• Under 25%wt gold or other noble metal

4. Titanium alloys

• 90-100% titanium: passive because of TiO2 oxide film

5. 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. Feldspar

2. Quartz

3. 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. There is no difference between an inlay and an onlay

b. An inlay is made of silver and an onlay is made of gold

c. An inlay should not exceed ½ the intercuspal distance, while an onlay covers the cusps

d. 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. There is no difference between an inlay and an onlay

b. An inlay is made of silver and an onlay is made of gold

c. An inlay should not exceed ½ the intercuspal distance, while an onlay covers the cusps

d. 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. Saliva contamination

b. Etch was not thoroughly rinsed

c. Tooth was not dried long enough prior to sealant placement

d. Patient compliance

Answer

What is the #1 cause of sealant non-retention?a. Saliva contamination

b. Etch was not thoroughly rinsed

c. Tooth was not dried long enough prior to sealant placement

d. 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 air-

abrasion• 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. Conserves tooth structure

b. Reduces microleakage

c. Improves esthetics

d. Provides micro-mechanical retention

e. 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. Conserves tooth structure

b. Reduces microleakage

c. Improves esthetics

d. Provides micro-mechanical retention

e. 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. The etch was not thoroughly rinsed off the tooth prior to sealant

placement

b. A dry field was not maintained and the tooth surface was contaminated by saliva after etching

c. The patient ate some candy after the placement of the sealants

d. The air supply to the A/W syringe was contaminated

e. 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. The etch was not thoroughly rinsed off the tooth prior to sealant

placement

b. A dry field was not maintained and the tooth surface was contaminated by saliva after etching

c. The patient ate some candy after the placement of the sealants

d. The air supply to the A/W syringe was contaminated

e. The tooth was not thoroughly dried prior to placement of the sealants

Question: Match the Following• Initiator a. Camphorquinone• Accelerator b. Amine• Monomer c. Bis-GMA

Answer: Match the Following• Initiator a. Camphorquinone• Accelerator b. Amine• Monomer c. Bis-GMA

• A, B, C

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:

1. 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

Cements• Used to affix a restoration to tooth structure, or as a base• Types:

4. 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

5. Hybrid cement• Resin-modified glass ionomer• Seals dentin effectively to minimize sensitivity (unfilled resin/bonding

agents)• Releases fluoride (glass ionomer)

6. 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 CementOrtho, final cementation

Zinc-Oxide Eugenol IRM, bacteriostatic, olive of clovesEndo, dressings, weakest base

Zinc-Polycarboxylate Cement acidRestorations, final cementation, strong luting agent

Glass Ionomer Release fluorideRestorations, resin, final cementationAdhere to tooth by chelation Ca by ionized polyacrylate

Hybrid Glass Ionomer Restorations, final cementationStrongest base, luting agent

Ca-Hydroxide Base, LinerSecondary/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 osseo-integration

• 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

1. 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. 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

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Impressions• Alginate: low tear strength, casts, opposing arches,

shrink: pour up within 15min, cheap, condensation• Silicone impression: polyvinyl, polyether

Impression Types1. Rigid (inelastic)

• Plaster, Type I Gypsum (occlusal record)• Compound (border mold custom tray)• Zinc-oxide/eugenol (final impression, full denture)

2. Flexible (elastometric): general purpose (next slide)

1) Polysulfide elastomer

2) Silicone elastomer

3) Polyether elastomer

4) Polyvinyl siloxane

5) PE-VPS hybrid

3. Flexible hydrocolloid

1) Agar-Agar (Reversible hydrocolloid)

2) Alginate (Irreversible hydrocolloid)

4. 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 detailUnstable n presence of moisture (will distort if

left wet)• Silicone Rubber (condensation rxn silicone)

Putty-like, rarely used• Vinylpolysiloxane (addition rxn silicone)

Tasteless, odorlessStable, strong, accurateEasily mexedCapable of multiple pours

ImpressionsFlexible 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