Dental Materials

• Structure of Matter and Principles Question and Answers
• Physical Properties of Dental Materials Question and Answers
• Mechanical Properties Question and Answers
• Dental Polymers Question and Answers
• Equilibrium Phases in Cast Alloys Question and Answers
• Biocompatibility of Dental Materials Question and Answers
• Impression Materials Question and Answers
• Elastic Impression Materials Question and Answers
• Rigid Impression Materials Question and Answers
• Gypsum Products Question and Answers
• Dental Waxes Question and Answers

• Casting Investments and Procedures Question and Answers
• Finishing and Polishing Materials Question and Answers
• Bonding Question and Answers
• Restorative Resins Question and Answers
• Dental Cements Question and Answers
• Dental Amalgam Question and Answers
• Direct Filling Gold Question and Answers
• Dental Ceramics Question and Answers
• Denture Base Resins Question and Answers
• Wrought Alloys Question and Answers
• Soldering and Welding Question and Answers
• Dental Implants Question and Answers

Bonding Important Notes

1. Enamel Bonding

• Acid etching is done which results in the formation of resin tags
• Etchant used are
  • Phosphoric acid – commonly 37% (37-50%)
  • Maleic acid
  • Citric acid
  • Oxalic acid
• Concentration greater than 50% results in the formation of monocalcium phosphate monohydrate which prevents further dissolution
• Concentration below 30% results in dicalcium phosphate dehydration that cannot be easily removed
• The length of application of etchant is 15 sec

2. Dentin Bonding Steps

• Step 1 – etching or conditioning
  • Conditioners are agents which aid in the removal or modification of the smear layer
  • Example: EDTA, 10% phosphoric acid, citric acid, maleic acid
• Step 2 – application of primer
  • Primers are monomers that are applied over the etched or conditioned surface for easy flow of bonding agents
  • Example: HEMA, HEMA -2 dissolved in acetone or alcohol
• Step 3 – application of dentin bonding agents

Read And Learn More: Dental Materials Question and Answers

3. Dentin Bonding Agents

They are unfilled resins that help in the formation and stabilization of the hybrid layer

Bonding Short Essays

Question 1. Mechanism of etching in acid etch technique
Answer:

Mechanism Of Etching In Acid Etch Technique

• It creates microporosities by discrete etching of the enamel by selective dissolution of enamel rod centers or peripheries or both
• Etching increases the surface area
• Etched enamel has a high-risk surface energy allowing the resin to wet the tooth surface better
• It penetrates microporosities
• When polymerized it forms resin tags which form a mechanical bond to the enamel

Question 2. Pit And fissure sealants
Answer:

Pit And Fissure Sealants

Pit and fissure sealants are fluid materials that are applied in pits and fissures on the occlusal surfaces of molar and premolar teeth

Dynamics Of Machinery 3-1 Mechanical Engineering R16 Jntuk Exam Point Of View Preparation Notes

Pit And Fissure Sealants Classification:

1. Based On Polymerization

• Self-activation
• Light activation

2. Resin Systems

• BIS-GMA
• Urethane acrylate

3. Clear Or Tinted

Pit And Fissure Sealants Ideal Properties

• Easily flowable into the deep pit and fissures.
• Should result in prolonged adhesion to enamel
• Must have cariostatic properties
• Must be non-irritant
• Should have wear resistance property

Pit And Fissure Sealant Indications:

• Children of less than 4 years of age
• Newly erupted teeth
• Stained pits and fissures

Pit And Fissure Sealant Contraindications:

• Low caries risk patients
• Wide pit and fissures
• Partially erupted teeth

Pit And Fissure Sealants Method Of Application:

• Clean the tooth surface
• Wash and dry the selected teeth
• Etch the tooth with 37% phosphoric acid for 15 sec.
• Wash off with water for 30 sec
• Air-dry it to obtain a frosted appearance
• Re-etch if required
• Apply the sealant
• Cure it

Pit And Fissure Sealants Materials Used:

• Resin- BIS-GMA
• Urethane acrylate
• Fuji 7 GIC
• Teethmate- fluoride-releasing sealant
• 3M concise- light cure white sealant
• Amorphous calcium phosphate-releasing sealant
• Enamel LOC
• Embrace, wet bond

Question 3. Acid etch technique
Answer:

Acid Etch Technique

• It is the process of increasing the surface reactivity by demineralizing the superficial calcium layer and thus creating enamel tags
• These tags help in micro-mechanical bonding between the tooth and restorative resin

Acid Etch Technique Mechanism:

• Cleanses debris
• Increases enamel surface area
• Produces micropores for mechanical interlocking
• Exposes more reactive surface layer

Acid Etch Technique Factors Effecting It:

• Form of acid-gel
• The concentration of acid- 37% phosphoric acid
• Time-15-20 sec
• Chemical nature of enamel
• Type of dentition

Acid Etch Technique:

• Oral prophylaxis
• Isolate the tooth
• Application of etchant for 15 seconds
• Rinse thoroughly for 5-10 seconds
• Dry it which results in a frosty, white appearance
• Apply enamel bonding
• Agents

Question 4. Dentin bonding agents
Answer:

Dentin Bonding Agents

• Dentin bonding agents have both hydrophilic and hydrophobic ends
• The hydrophilic end displaces dentinal fluid while the hydrophobic end bonds to the composite resin

Bonding Short Question And Answers

Question 1. Pit and fissure sealants
Answer:

Pit And Fissure Sealants

Pit and fissure sealants are fluid materials that are applied in pits and fissures on the occlusal surfaces of molar and premolar teeth

Pit And Fissure Sealants Classification:

1. Based On Polymerization

• Self-activation
• Light activation

2. Resin Systems

• BIS-GMA
• Urethane acrylate

3. Clear or tinted

Pit And Fissure Sealants Method Of Application:

• Clean the tooth surface
• Wash and dry the selected teeth
• Etch the tooth with 37% phosphoric acid for 15 sec
• Wash off with water for 30 sec
• Air-dry it to obtain a frosted appearance
• Re-etch if required
• Apply the sealant
• Cure it

Question 2. Sandwich technique
Answer:

Sandwich Technique

• Developed by Mclean et al in 1985
• Refers to a laminated restoration using glass ionomer to replace dentin and composite to replace enamel
• Composite bonds micromechanically to set GIC and chemically to the HEMA

Sandwich Technique:

• Isolate the tooth
• Tooth preparation
• Butt joint
• Beveling of enamel margin
• Pulp protection using calcium hydroxide
• Tooth conditioning using polyacrylic acid
• Placement of GIC
• Etching of GIC surface
• Coating with a dentin bonding agent
• Placement of composite and curing
• Finishing and polishing

Sandwich Technique Indications:

• Lesions where one or more margins are in dentin, for Example., cervical lesions.
• Class 1 composite restorations.

Question 3. Acid etch technique
Answer:

Acid Etch Technique:

• Oral prophylaxis
• Isolate the tooth
• Application of etchant for 15 seconds
• Rinse thoroughly for 5-10 seconds
• Dry it which results in a frosty, white appearance
• Apply enamel bonding agents

Restorative Resins Important Notes

1. Definition Of Composites

Composites a compounds composed of at least two different materials with properties that are superior or intermediate to those of an individual component.

2. Composition Of Composites

3. Classification Of Composites

• According to the particle size
  • Traditional composite – 8-12 pm
  • Small-sized composite – 1-5 pm
  • Microfilled composite – 0.4-0.9pm
  • Hybrid composite – 0.6-1 pm
• According to filler particles
  • Megafilled
  • Macrofilled
  • Midfilled a Minifilled
  • Microfilled e Nanofilled
• According to the polymerization method
  • Self-curing
  • Ultraviolet light curing
  • Visible light curing
  • Dual curing

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4. Chemically Activated Composites

• Supplied in two pastes
• Base – contains initiator benzoyl peroxide
• Accelerator – contains tertiary amine as an activator
• Manipulated by mixing in proper proportions on a mixing pad with an agate spatula
• The cavity is slightly overfilled
• Shrinkage occurs towards the center of the material

5. Light-Activated Composites

• Contains single paste
• Initiator – Camphoroquinone
• Activator – ‘diethyl-amino-ethyl-methacrylate
• They are activated to the light of wavelength 400-500 nm
• Ultraviolet light is not indicated
• Source of light – tungsten halogen bulb
• The tip should be kept as close as possible
• Cured in increments
• Exposure time – 40-60 sec
• Shrinkage occurs towards the light source.

Restorative Resins Long Essays

Question 1. Classify composite resin restorative materials. Describe its composition, properties, and uses of it.
Answer:

Composite Resin:

A solid formed from two or more distinct phases that have been combined to produce properties superior to or intermediate to those of the individual constituents is described as a dental composite

Composite Resin Classification:

• According To The Particle Size
  • Traditional composite- 8-12 μm
  • Small-sized composite-1-5 μm
  • Microfilled composite- 0.4-.0.9 μm
  • Hybrid composite- 0.6-1 μm
• According To Filler Particles
  • Mega filled
  • Macrofilled
  • Midfilled
  • Minifilled
  • Microfilled
  • Nanofilled
• According To The Polymerization Method
  • Self-curing
  • Ultraviolet light curing
  • Visible light curing
  • Dual curing

Composite Resin Composition:

Composite Resin Properties:

Composite Resin Uses:

• Restoration of classes 1, 2, 3, 4, 5, 6
• Discolored tooth
• Midline Diastema Cases
• Veneers And Laminates
• Bonding Of Orthodontic appliances
• Restorations of non-carious lesions
• Core foundation
• As indirect restoration
• For periodontal splinting

Question 2. Discuss the advantages and disadvantages of light cure composite resins.
Answer:

Light Cure Composites:

• They are of two types
  • Visible light composite resin
  • UV light composite resin

Light Cure Composites Advantages:

• Easy manipulation
• No mixing required
• Infinite working time
• Short controlled setting time
• The amount of finish and polish required is much less
• Less waste of material

Light Cure Composites Advantages of Visible Light Over UV Light:

• Can be cured to a greater depth
• Elimination of health hazard
• No warm-up time required
• No decrease in the intensity of the light source
• To maintain adhesion to cavity walls in a deep cavity incremental technique can be used

Light Cure Composites Disadvantages:

Question 3. What are anterior restorative materials? Discuss in detail composite resins.
Answer:

Anterior Restorative Materials:

• Silicate cement
• Glass ionomer cement
• Acrylic resin
• Composite resin
• Porcelain
• Composites

Question 4. write details about the various components of composite resins. Add a note on the posterior composite.
Answer:

Posterior Composites Indications:

• Small, incipient lesion
• Possible to control moisture
• As core foundation
• Patient with low caries index

Posterior Composites Contraindications:

• Difficult to control moisture
• Extensive lesion
• High occlusal stresses
• Presence of parafunctional habits
• Patients with high caries index and poor oral hygiene

Posterior Composites Advantages:

• Esthetic
• Conservative
• Micromechanical bonding
• Economical compared to indirect restoration
• Absence of galvanism

Posterior Composites Disadvantages:

• Polymerization shrinkage
• Technique sensitive
• Time-consuming
• Expensive compared to amalgam

Posterior Composites Procedure:

• Tooth preparation
  • Use small round bur initially
  • Extend preparation using fissure bur
  • Maintain minimal depth
  • Faciolingual dimension 1/4th of the intercuspal distance
  • No need for retentive features
  • Converge occlusal walls
  • Round line angles
  • Bevelling of enamel margins
• Matrix placement
• Etching of the preparation with 37% phosphoric acid
• Application of primer and adhesive
• Pulp protection
• Use of calcium hydroxide as base
• GIC as liner
• Composite placement
• Done in increments with subsequent curing it
• Finishing and polishing

Restorative Resins Short Essays

Question 1. Hybrid Composites
Answer:

Hybrid Composites

• Hybrid composites are developed to have better surface smoothness and esthetic characteristics
• It contains two kinds of filler particles

Hybrid Composites Filler Type

• Heavy metal glasses
• Average particle size- 0.4-1 μm
• Colloidal silica
• Size- 0.04 μm

Hybrid Composites Properties:

Question 2. Fillers and their role in composite resins
Answer:

Fillers And Their Role In Composite Resins

• Fillers are added to the resin matrix to improve its properties
• Composites are classified on the basis of the average size of major filler component

Composite Resins Functions:

• Increases hardness
• Increases strength
• Decreases wear
• Reduces polymerization shrinkage
• Reduces thermal expansion and contraction
• Increases viscosity
• Decreases water sorption, softening, staining
• Increases radiopacity
• Decreases curing shrinkage

Composite Resins Factors Affecting Filler Selection:

• Amount of Filler added
• Size of particle
• Shape of Filler
• Index of refraction
• Radiopacity
• Hardness

Composite Resins Types:

• Quartz Filler
• Glasses or ceramics containing heavy metals
• Boron silicates
• Lithium aluminum silicates
• Ytterbium trifluoride
• Colloidal silica

Question. 3. Classification and uses of composite resins
Answer:

Composite Resins Classification

• According To The Particle Size
  • Traditional composite- 8-12 μm
  • Small-sized composite-1-5 μm
  • Microfilled composite- 0.4-.0.9 μm
  • Hybrid composite- 0.6-1 μm
• According To Filler Particles
  • Mega filled
  • Macrofilled
  • Midfilled
  • Minifilled
  • Microfilled
  • Nanofilled
• According To The Polymerization Method
  • Self-curing Ultraviolet light curing
  • Visible light curing
  • Dual curing
• Composite Resins Use:

• Restoration of Class 1,2 3, 4, 5, 6
• Discolored tooth
• Midline diastema cases
• Veneers and laminates
• Bonding of orthodontic appliances
• Restoration of non-carious lesions
• Core foundation
• As indirect restoration
• For periodontal splinting

Question 4. Dual cured composites
Answer:

Dual Cured Composites

• Dual cure resins combine chemical curing and visible light curing components in the same resin
• So-called dual cure resins

Dual Cured Composites Composition:

• Supplied in two pastes system
• One contains benzoyl peroxide and the other contains an aromatic tertiary amine

Dual Cured Composites Action:

• When two pastes are mixed and then exposed to light, light curing is promoted by the amine or chloroquine combination
• Chemical curing occurs by amine/ benzoyl peroxide combination

Dual Cured Composites Advantages:

Can be used for cementing crowns or bulk restorations where there is limited light penetration

Dual Cured Composites Disadvantages:

• Air inhibition
• Porosity

Question 5. Microfilled composites
Answer:

Microfilled Composites

Microfilled composites were developed to overcome the surface roughening and translucency of traditional Composites.

Microfilled composites Properties:

Microfilled Composites Clinical Considerations:

• Mechanical properties are inferior to another type of composite
• Esthetic is better than other composites
• Thus it is for anterior teeth in non-stress-bearing areas because decreased physical properties do not create a problem here
• In stress-bearing areas, they have a potential for fracture
• Sometimes chipping occurs at the margins

Question 6. Contents and their role in composite resins
Answer:

Contents And Their Role In Composite Resins

Question 7. Light cure composites.
Answer:

Light Cure Composites Are

• There are two types of light cure composites
• Visible light composite resin
• UV light composite resin

Light Cure Composites Advantages:

• Easy manipulation
• No mixing required
• Infinite working time
• Short controlled setting time
• The amount of finish and polish required is much less
• Less waste of material

Light Cure Composites Light Sources:

• Light emitting diodes
• Quartz tungsten halogen lamps
• Plasma arc curing lamps
• Argon laser lamps

Restorative Resins Short Question And Answers

Question 1. Composite resin
Answer:

Composite Resin

A solid formed from two or more distinct phases that have been combined to produce properties superior to or intermediate to those of the individual constituents is described as a dental composite

Composite Resin Uses:

• Restoration of Class 1,2 3, 4, 5, 6
• Discolored tooth
• Midline diastema cases
• Veneers and laminates
• Bonding of orthodontic appliances
• Restoration of non-carious lesions
• Core foundation
• As indirect restoration
• For periodontal splinting

Question 2. Filler in composite resin
Answer:

Filler in composite Resin

• Fillers are added to the resin matrix to improve its properties
• Composites are classified on the basis of the average size of major filler component

Filler In Composite Resin Functions:

• Increases hardness
• Increases strength
• Decreases wear
• Reduces polymerization shrinkage
• Reduces thermal expansion and contraction
• Increases viscosity
• Decreases water sorption, softening, staining
• Increases radiopacity
• Decreases curing shrinkage

Question 3. Visual light cure composite
Answer:

Visual Light Cure Composite

Wavelength used- 460-470 nm

Visual Light Cure Composite Mechanism:

• On activation, the photoinitiator combines with an amine accelerator
• Release of free radicals
• Polymerization

Visual Light Cure Composite Photoinitiator Used

The photoinitiator used is camphor quinone

Visual Light Cure Composite Advantages:

Improved color stability

Question 4. Photoinitiators
Answer:

Photoinitiators

• Camphoroquinone is a commonly used photoinitiators
• It absorbs blue light with a wavelength between 400-500 nm
• Exposure to light in the blue region produces an excited state of the photoinitiator
• It interacts with the amine to form free radicals that initiate addition polymerization
• Only small quantities of camphor quinone are required
• A number of amine initiators are suitable for interaction with camphor quinone such as dimethylamino-ethyl methacrylate

Question 5. Coupling agents in composite resins
Answer:

Coupling Agents In Composite Resins

• The coupling agent bonds the filler particles to the resin matrix
• The most commonly used coupling agent is organosilanes
• In the presence of water, the methoxy group of it forms an ionic bond with the filler particle
• On the other end, the methacrylate group forms a covalent bond with resin when it is polymerized

Coupling Agents Functions:

• Transfers stress to filler particles
• Improves physical and mechanical properties
• Inhibits leaching by preventing water from penetrating along the filler resin interface

Question 6. Composition of composite resin
Answer:

Composition Of Composite Resin

Question 7. Light-activated composites
Answer:

Light-Activated Composites

• There are two types of light-activated composites
• They are
• Visible light-activated composites
• UV light-activated composites

Light-Activated Composites Advantages:

• Easy manipulation
• No mixing required
• Infinite working time
• Short controlled setting time
• The amount of finish and polish required is very less
• Less waste of material

Light-Activated Composites Light Sources:

• Light emitting diodes
• Quartz tungsten halogen lamps
• Plasma arc curing lamps
• Argon laser lamps

Question 8. Microfilled vs conventional composite resins
Answer:

Microfilled vs Conventional Composite Resins

Question 9. Bis-GMA
Answer:

Bis-GMA

• It was developed by RL Bowen in early 1960
• It is a high molecular weight monomer formed by a reaction between a molecule of ethylene glycol of bisphenol A and glycidyl methacrylate

Bis-GMA Functions:

• Reduces polymerization shrinkage
• Increasesstrengthandrigidity
• Increases viscosity

Bis-GMA Limitations:

• High viscosity
• Difficulty in synthesizing a pure composition
• Strong air inhibition to polymerization
• High water sorption because of diluents used
• Polymerization shrinkage
• It does not adhere to tooth structure

Wrought Alloys Important Notes

1. Stainless Steel.

• Austenitic stainless steel
• Use – To make orthodontic archwires

Stainless Steel Properties:

• Adequate strength
• Adequate spring back
• Resilience
• Formability
• Biocompatible
• Economical

2. Alloys And Their Constituents

• Elgiloy-cobalt-chromium-nickel
• Beta titanium – titanium – molybdenum – aluminum
• Nitinol-nickel-titanium
• Titanium alloys – titanium – aluminum – vanadium

Wrought Alloys Short Essays

Question 1. Ni-Ti orthodontic wire.
Answer:

Ni-Ti orthodontic wire

• Synonym – Nitinol (Nickel Titanium Naval Ordinance Laboratory)
• Inventor – William R. Buchler
• Introduced by – Andersen in 1971

Nickel Titanium Alloy Properties:

• Super elasticity
• Shape memory
• High spring back
• High working range
• Low stiffness

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Ni-Ti orthodontic wire Advantages or Nickel Titanium Alloy Properties:

Produce low and more constant force on teeth

Ni-Ti orthodontic wire Disadvantages or Nickel Titanium Alloy Properties:

• Cannot be bent
• Cannot be soldered or welded

Question 2. Types of Stainless Steel.
Answer:

Types of Stainless Steel

• Types of stainless steel are
• Ferritic stainless steel
• Austenitic stainless steel
• Martensitic stainless steel

Sensitization Of Stainless Steel

Wrought Alloys Short Question And Answers

Question 1. Stages of annealing heat treatment.
Answer:

Stages Of Annealing Heat Treatment

Question 2. Zones of flame.
Answer:

Zones Of Flame

Question 3. Sensitization of 18-8 stainless steel.
Answer:

Sensitization Of 18-8 Stainless Steel

• At 400-900°C, stainless steel resists corrosion and tarnish
• At lower temperatures, carbon reacts with the surface granules and forms chromium iron carbide causing tarnish and corrosion
• This can be prevented by decreasing carbon content or by cold working of stainless steel.

Soldering And Welding Important Notes

1. Soldering And Welding Soldering

Soldering And Welding Soldering is a process of joining metals by the use of a filler metal that has a lower fusion temperature than that of the metals being joined.

Soldering Types:

• Investment soldering
• Freehand soldering

2. Soldering And Welding Welding

Involves the joining of two metals without introducing a third metal

3. Soldering And Welding Flux and antireflux

• Flux – means flow
• Important for good solder joint

Flux And Antireflux Uses:

• Removal of oxide coating of solder
• Dissolves impurities
• Prevents oxidation
• Reduces melting point

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Flux And Antireflux Composition:

• Borax glass – 55%
• Boric acid – 35%
• Silica -10%
• Antiflux – Confines flow of molten solder
• Example. Lead pencil markings
• Graphite lines
• Iron rouge

Soldering And Welding Short Essays

Question 1. Soldering and Welding.
Answer:

Soldering – It is a process of joining metals by the use of a filler metal that has a lower fusion temperature than that of the metals being joined.

Soldering And Welding Types:

1. Investment Soldering:

• Indication – Presence of large contact area between metals
• In need of precision
• Procedure – By embedding metals in investment

2. Freehand sSoldering:

• Indication – Common orthodontic procedures
• Procedures – Soldering by holding metals precisely

Soldering And Welding Steps:

• Clean the surfaces
• Assemble the parts Select the proper solder and flux
• Select proper joint
• Flux application
• Application of solder
• Quenching
• Welding – involves the joining of two metals without introducing a third metal
• Procedure:
• • Selection of electrode
  • Placement of metals between 2 electrodes
  • Maintain pressure on it
  • Switch on electrode
  • Keep it for sometime

Soldering And Welding Short Question And Answers

Question 1. Soldering flux.
Answer:

Soldering Flux

• Flux – means flow
• Important for good solder joint

Soldering Flux Uses:

• Removal of oxide coating of solder
• Dissolves impurities
• Prevents oxidation
• Reduces melting point

Soldering Flux Composition:

• Borax glass – 55%
• Boric acid-35%
• Silica -10%

Question 2. Requirements of dental solder.
Answer:

Requirements Of Dental Solder

• It should melt at a temperature below the solidus temperature of the parent metal
• When melted it should be wet and flow freely over the parent metal
• Its color should match that of the metal being joined
• It should be resistant to tarnish and corrosion
• It should resist pitting during heating and application

Direct Filling Gold Important Notes

1. Direct Filling Gold Gold foil

• It is manufactured by beating pure gold into thin sheets
• Size: 4*4 inches
• Surface impurities and foil treated with ammonia make the gold foil noncohesive
• It is used for the external surface veneering of the restoration

2. Direct Filling Gold Mat gold

• It is used as a bulk filler
• Available as strips or cakes

3. Direct Filling Gold Mat foil

• Mat gold wrapped in gold foil
• Used for veneering the external surface of the restoration

4. Direct Filling Gold Electroalloy

• Electrolytic precipitates alloyed with 0.1% calcium
• Calcium increases strength and hardness

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5. Direct Filling Gold Powdered gold

It is chemically precipitated gold powder with an average particle size of 15 pm

6. Direct Filling Gold Condensation

• It is a process of cold working
• It increases hardness, strength
• Results in fibrous grain structure
• The force of condensation is inversely proportional to the square of the diameter of the nib
• Forces of condensation must be
• 45° to the cavity walls and floor
• 90° to the previous increment
• Steeping is the process of condensation where each condenser overlaps the previous compaction

Direct Filling Gold Long Essays

Question 1. In what forms is gold used in dentistry? Describe in detail the various types of direct-filling gold available. Briefly mention the degassing technique.
Answer:

Various Types of Direct Filling Gold Available are

• Foil
• Sheet
• Cohesive
• Noncohesive a Ropes
• Cylinders
• Laminated foil
• Platinized foil
• Electrolytic precipitate
• Mat gold
• Mat foil
• Gold-calcium alloy – Granulated or powdered gold

Degassing:

Degassing Synonyms: Desorbing, annealing

Degassing Description:

• Except noncohesive golds, the direct filling gold is available 1 cohesive forms
• During storage and packaging, they are exposed to gases from the atmosphere
• Adsorbed gases prevent gold from fusing
• Thus it is necessary to heat the foil or pellet immediately before it is carried into a prepared cavity
• This process is called annealing, degassing, or desorbing
• It can be done by one of the two methods
• In bulk on a tray by gas flame or electricity
• Piece by piece in a well-adjusted alcohol flame
• Electric annealing
  • Annealer is maintained at a temperature between 340° C and 370°C
  • The time required varies from 5-20 min
  • Problems associated with it are
  • Adhesion of pellets
  • Air currents that affect heating uniformity
  • Heating an excessive amount of gold
  • Excessive sintering
  • Greater exposure to contamination
  • Size selection is limited
• Flame desorption

• Fuel for the flame may be alcohol or gas but alcohol is preferred
• Degassing Advantages:
  • Selection of piece of appropriate size
  • Desorption of only those pieces used
  • Reduced exposure to contamination
  • Less danger of overwintering
• Underheating leads to
  • Does not adequately remove impurities
  • Incomplete cohesion
  • The remaining impurities and carbon are deposited by the flam

• • Causes pitting and flaking of the surface
• Overheating leads to
  • Excessive sintering
  • Contamination from the tray, instrument, or flame
  • Incomplete cohesion
  • Embrittleness of the portion being heated
  • Poor compaction

Question 2. Explain Direct-filling gold’s physical properties, manipulation, and advantages.
Answer:

Direct Filling Gold’s Physical Properties:

• Direct Filling Gold is the noblest of all dental metals
• Direct Filling Gold’s rarely tarnish or corrode
• Direct Filling Gold’s is inactive chemically
• Direct Filling Gold’s is not affected by air, heat, moisture, or most solvent
• Direct Filling Gold’s is the most ductile and malleable
• Strength
• Greater strength is in the most dense area and the weakest part is the porous area
• Hardness
• Pure gold is extremely soft but after cold working its hardness increases
• Density-19.3 g/cm³
• Biocompatibility
• The pulpal response is minimal if compacted well

Direct Filling Gold’s Manipulation:

• Direct Filling Gold’s involves three processes
• Desorbing
• With the exception of noncohesive golds, the direct filling gold is available 1 cohesive forms
• During storage and packaging, they are exposed to gases from the atmosphere
• Adsorbed gases prevent gold from fusing
• Thus it is necessary to heat the foil or pellet immediately before it is carried into a prepared cavity
• This process is called annealing, degassing, or desorbing
• It can be done by one of the two methods
• In bulk on a tray by gas flame or electricity
• Piece by piece in a well-adjusted alcohol flame
• Compaction

• Finishing
• A small amount of excess material is provided to ensure proper contour
• Excess material is trimmed away with sharp gold knives and files
• The surface is burnished with a ball burnisher to strain and harden the surface
• The final polish is achieved with Soflex disks

Direct Filling Gold’s Advantages:

• Direct Filling Gold’s is the noblest of all dental metals
• Direct Filling Gold’s rarely tarnish or corrode
• Direct Filling Gold’s is the most ductile and malleable
• Direct Filling Gold’s is biocompatible

Direct Filling Gold Short Essays

Question 1. Cohesive and noncohesive gold
Answer:

Cohesive Gold:

• For cold welding, gold should have a clean surface free from impurities
• Gold attracts gases to its surface and any adsorbed gas film prevents the intimate atomic contact required for cold welding
• This prevents the cohesion of individual increments of gold during their compaction
• Therefore manufacturers supply the foil essentially free of surface contaminants
• This type of gold is called cohesive gold

Non Cohesive Gold

• Most gold sheets are provided with absorbed protective gas film such as ammonia
• This substance minimizes the adsorption of other less volatile substances
• It prevents premature cohesion of sheets or segments of sheets that may come into contact
• The ammonia-treated foil is called noncohesive foil
• This volatile film is readily removed by heating to restore cohesive character
• Other agents used are
• Iron salts
• Acidic gas
• Use:
• To build up the bulk of the direct gold restoration

Question 2. Types of gold alloy
Answer:

Types Of Gold Alloy

• Various Types of Direct Filling Gold Available are
• Foil
• Sheet
• Cohesive
• Non-cohesive
• Ropes
• Cylinders
• Laminated foil
• Platinized foil
• Electrolytic precipitate
• Mat gold
• Mat foil
• Gold-calcium alloy
• Granulated or powdered gold

Question 3. Mat gold
Answer:

Mat gold

• Mat gold is an electrolytically precipitated crystalline form that is sandwiched between sheets of gold foil and formed into strips which can be cut by the dentist into the desired size
• This form is often preferred for its ease in building up the internal bulk of the restoration because it can be more easily compacted within and adapted to the retentive portions of the prepared cavity
• Because it is loosely packed, it is friable and contains numerous void spaces between particles
• Therefore it is generally not recommended for the external surface of the restoration
• The loosely packed crystalline form of the mat powder with its large surface area does not permit easy welding into a solid mass
• Therefore there is a greater tendency for voids that may be seen as pits to form if mat gold is used on the surface of the restoration

Direct Filling Gold Short Question And Answers

Question 1. Cohesive and noncohesive gold
Answer:

Cohesive And Noncohesive Gold

• Manufacturers supply the foil essentially free of surface contaminants
• This type of gold is called cohesive gold
• Most gold sheets are provided with absorbed protective gas film such as ammonia
• This substance minimizes the adsorption of other less volatile substances
• It prevents premature cohesion of sheets or segments of sheets that may come into contact
• This ammonia-treated foil is called noncohesive foil

Question 2. Gold foil
Answer:

Gold Foil

Gold Foil is the oldest of all products

Gold Foil Manufacturer:

A cast ingot of 15 mm thickness is beaten to a submit- microscopic thickness of 15-25 pm

Gold Foil Supplied As:

• Sheets
• Pellets
• Cylinders
• Ropes
• Partially condensed
• Laminates

Gold Foil Numbering:

It reflects the weight of the standard sheet as well as the thickness

Gold foil Uses:

• A number of sheets are placed over one another to form laminated gold foil
• No.3 is used in the electrolytic and powder products

Question 3. Degassing
Answer.

Degassing

• With the exception of noncohesive golds, the direct filling gold is available 1 cohesive forms
• During storage and packaging, they are exposed to gases from the atmosphere
• Adsorbed gases prevent gold from fusing
• Thus it is necessary to heat the foil or pellet immediately before it is carried into a prepared cavity
• This process is called annealing, degassing, or desorbing
• It can be done by one of the two methods
• In bulk on a tray by gas flame or electricity
• Piece by piece in a well-adjusted alcohol flame

Question 4. Mat gold, electrolytic gold
Answer:

Mat gold, electrolytic gold

• Mat gold, electrolytic gold is a form of direct-filling gold formed by electrolytic precipitation
• Mat gold, electrolytic gold is crystalline
• Mat gold, electrolytic gold is formed in strips
• These strips are cut by the dentist into the desired size
• Mat gold is preferred because it is easy to build up the internal bulk of the restoration

Question 5. Karat and fineness
Answer:

Karat And Fineness

• The purity of gold is expressed in carats often abbreviated as ct or K
• Pure gold has a purity of 24 carats
• An alternative method of expressing purity is fineness
• This expresses the purity in parts per 1000
• Relationship between gold content carat and fineness

• Gold is too soft to be used for jewelry
• So it may be alloyed with other metals such as silver, copper, zinc, or silicon
• This produces purities of less than 24 carats

Denture Base Resins Important Notes

1. Composition Of Heat-Activated Resin

2. Heat Cure And Self-Cure Resins

3. Porosity

• Internal porosity
• Occurs in central thick areas of the denture if the resin is heated above the boiling point of the monomer
• External porosity
• Occurs due to inadequate pressure, application, and improper mixing of monomer and polymer

Read And Learn More: Dental Materials Question and Answers

4. Stages In The Mixing of Heat Cure Resin

• Wet sandy stage
• Sticky stage
• Dough stage
• Rubbery stage
• Stiff stage

5. Tissue Conditioners

• They are highly plasticized acrylic resins used as temporary soft liners to condition the inflamed and distorted tissues caused by ill-fitting dentures
• It contains polymer powder and a liquid containing aromatic ester in ethanol

Denture Base Resins Long Essays

Question 1. What are denture base rosins? Describe the properties and manipulation technique of heat-cure acrylic resin.
Answer:

Denture Base Resin Properties:

• Monomer
  • Clear, transparent, volatile liquid
  • Sweetish odor
  • Melting point–48° C
  • Boiling point-iOO°C
  • Density -0.945 gm/ml at 20° C
  • The heat of polymerization is 12.9 Kcal/mol
  • Volume shrinkage-21%
• Polymer
• Tasteless, odorless
• Aesthetic acceptable
• Density-1.19 m/cm3
• Strength-low
• Compressive strength -75 MPa
• Tension strength -52 MPa
• Impact strength – increases by plasticizer
• Hardness -18-20 KHN
• Modulus of elasticity -2400 MPa
• Well-processed acrylic has good dimensional stability
• It shrinks due to
• Thermal shrinkage
• Polymerization shrinkage
• Water sorption-0.6 mg/cm2
• Insoluble in water and oral fluids
• Thermal properties -Softenat 125 C
• Poor conductor of heat and electricity
• High coefficient of thermal expansion
• Has good color stability
• Biocompatible
• Adhesion to metal and porcelain is poor
• Adhesion to denture teeth is good
• Shelf life varies

Denture Base Resin Manipulation Techniques:

• Compression molding technique
  • Commonly used technique
  • Steps
  • Preparation of wax pattern
  • Preparation of split mold
  • Application of separating media
  • Mixing of powder and liquid
  • Parking Curing Cooling Deflasklng
  • finishing and polishing
• Injection molding technique
  • Mold space Is filled by injecting Resin under pressure
  • A sprue hole and vent are formed in the mold
  • Soft resin Is forced into the mold space through Injector
  • It Is kept under pressure until it hardens
• Fluid resin technique
  • Resin is mixed to form a thin dough
  • This can be poured into the mold space
  • Kept In a pressure chamber for 30-60 min
  • Light cure denture base technique
  • Visible light of 468 nm is used as an activator and a complete denture is cured in a light chamber for .10 min

Question 2. Write in detail about the composition and the properties of denture base resin and add a note on light-activated denture base resins
Answer:

Denture Base Resin Powder:

Denture Base Resin Liquid:

Light Activated Denture Base Resin:

• Consist of
• A urethane methacrylate matrix
• Microfine silica fillers
• Camphoroquinone amine photoinitiator system
• N.N. Dimethyl paratoludineacceleritor

Denture Base Resin Technique:

Denture Base Resin Disadvantages:

• Complicated
• Expensive
• No improvement in properties

Question 3. What are soft liners? Write composition, properties, and uses of tissue conditioners
Answer:

Soft Liners Types:

• Temporary soft liners
• Permanent soft liners
• Plasticized acrylic resin
• Vinyl resin
• Silicone rubber

Soft Liners Purpose:

• To protect soft tissues by acting as a cushion
• Used when irritation of the mucosa occurs
• Used in areas of severe undercut and congenital or acquired defects of the palate

Soft Liners Tissue Conditioner:

Tissue conditioners are materials whose useful function is very short

Soft Liners Composition:

• Powder-poly ethyl methacrylate and its copolymers
• Liquid-aromatic ester in ethanol or alcohol of high molecular weight

Soft Liners Properties:

• Viscous properties
• Allow excellent adaptation to the irritated denture-bearing mucosa
• Elastic behavior
• Cushions the tissues from the forces of mastication and bruxism

Soft Liners Uses:

• Reclining of ill-fitting dentures
• As an impression material

Question 4. Classify denture base resins. Write the composition and action of each constituent of heat cure acrylic. Add a note on porosity and its causes in dental acrylic resins.
Answer:

Denture Base Resins Classification:

• Temporary
• Shellac base plate
• Base plate wax
• Permanent
• Light cure resin
• Pour type resins
• Injection molded resins

Denture base resins porosity:

Denture Base Resins Short Essays

Question 1. Resilient denture liners
Answer:

Resilient Denture Liners

• A denture recliner is a polymeric material placed on the tissue-contacting surface of a denture base to absorb some of the energy produced by masticatory impact
• Act as a shock absorber between the occlusal surfaces of a denture and the underlying oral tissues

Resilient Denture Liners Types:

• Hardliners
  • The materials used are either cold cure or heat cure acrylic with a composition similar to denture base resin
  • They should chemically bond to the old denture base
  • Retain dimensional stability
  • Cold-cure acrylic is preferred
• Soft Resilient Liners
  • They are of two types
  • Permanent -Temporary
  • Purpose
  • To protect soft tissues by acting as a cushion
  • Used when irritation of the mucosa occurs
  • Used in areas of severe undercut and congenital or acquired defects of the palate
  • Short-term resilient liner or tissue conditioner

Question 2. Tissue conditioners
Answer:

Tissue Conditioners

• Tissue conditioners are chemically activated polymeric materials that tend to degrade more rapidly than heat-activated resin
• Supplied as powder of polymethylmethacrylate or its higher copolymers
• Liquid has plasticizers like aromatic esters such as butyl phthalate, butyl glycolate in alcohol or ethanol
• They can be formed directly in the patient’s mouth

Tissue Conditioners Disadvantages:

• Poor mechanical bonding
• Dimensionally unstable
• No permanent resilience
• Difficult to polish

Question 3. Separating media
Answer:

Separating Media Uses

• To prevent water from the mold from entering the acrylic resin
• To prevent monomers from penetrating into the mold
• Helps in the easy retrieval of dentures from the mold

Separating Media Types:

• Tinfoil
• Cellulose
• Solution of alginate compound
• Calcium oleate
• Soft soaps
• Sodium silicate
• Starches

Separating M

edia Applications:

• Applied using a brush, coating only the plaster surfaces and not acrylic teeth
• One or two coats may be applied

Question 4. Curing
Answer:

Curing

• It is the heating process employed to control the initial propagation of polymerization in the denture mold
• The selection of the curing cycle depends on the thickness of the resin
• Curing cycles are
• Heating the flask in water at 60-70T. for 9 hours
• Heating the flask at 65T, for 90 min
• Removing the flask from the water bath, bench cooling it for 30 min and pacing it in cold tap water for 13 min is satisfactory

Question 5. Requirements Of Denture Base Materials
Answer:

Requirements of Denture Base Materials

• Should be tasteless, odorless, non-toxic and non-irritant
• Be esthetic
• Be dimensional stable
• Have enough strength, resilience, and abrasion resistance
• Be insoluble and impermeable to oral fluids
• Have low specific gravity
• Tolerate temperature well
• Be easy to fabricate and repair
• Have good thermal conductivity
• Be radiopaque
• When used as filling material it should
• Bond chemically to the tooth
• Have a coefficient of thermal expansion matching that of tooth structure
• Be economical

Question 6. Curing Cycles Of Heat Cure Acrylic Resin
Answer:

Curing Cycles Of Heat Cure Acrylic Resin

• The curing cycle is the heating process used to control the initial propagation of polymerization in the denture mold
• It is selected according to the thickness of the resin

Curing Cycles Of Heat Cure Acrylic Resin Types:

• Long curing cycle
• The flask is heated in water at 60*70’1C for 9 hours
• Short curing cycle
• The flask is heated at 65°C for 90 min
• Then boil for 1 hour for adequate polymerization of the thinner portions

Denture Base Resins Short Question And Answers

Question 1. Condensation polymerization
Answer:

Condensation Polymerization

• Condensation polymerization is of two types
• Those in which polymerization is accompanied by repeated elimination of small molecules with the formation of by-products such as water, halogen, acids, etc
• Those in which function groups are repeated in polymer chains. Example. polyurethane

Question 2. Chemical stages in polymerization
Answer:

Chemical Stages In Polymerization

• Induction
• Propagation
• Termination
• Chain transfer

Question 3. Cold cure acrylic
(or)
Autopolymerizing resin
Answer:

Autopolymerizing Resin

• The chemically activated acrylic resin polymerizes at room temperature
• They are known as self-curing cured or auto-polymerizing resins
• The chemical initiator benzoyl peroxide is activated by another chemical dimethyl para toluidine which is present in the monomer

Question 4. Light-activated denture base resin
Answer:

Light-Activated Denture Base Resin consists of:

• A urethane dimethacrylate matrix
• Microftne silica fillers
• Carnphoroquinone amine photoinitiator system
• N.N. Dimethyl paratoludtne accelerator

Light-Activated Denture Base Resin Disadvantages:

• Complicated
• Expensive
• No improvement in properties

Question 5. Denture cleansers
Answer:

Denture Cleansers

Dentures are cleaned by either immersion in the agent or by brushing with the cleanser

Denture Cleansers Types:

• Household cleanser
• Bleaches
• Vinegar
• Dentrifices
• Mild detergents

Denture Cleansers Composition:

• Alkaline compounds
• Detergents
• Flavoring agents
• Sodium perborate

Question 6. Tissue conditioners
Answer:

Tissue Conditioners

• Tissue conditioners are chemically activated polymeric materials that tend to degrade more rapidly than heat-activated resin
• Supplied as powder of polymethylmethacrylate or its higher copolymers
• Liquid has plasticizers like aromatic esters such as butyl phthalate, butyl glycolate in alcohol or ethanol
• They can be formed directly in the patient’s mouth

Tissue Conditioners Disadvantages:

• Poor mechanical bonding
• Dimensionally unstable
• No permanent resilience
• Difficult to polish

Question 7. Denture recliners
Answer:

Denture Recliners

• A denture recliner is a polymeric material placed on the tissue-contacting surface of a denture base to absorb some of the energy produced by masticatory impact
• Act as a shock absorber between the occlusal surfaces of a denture and the underlying oral tissues

Denture Recliners Types:

• Hard-liners
• Soft resilient liners
• Short-term resilient liner or tissue conditioner

Question 8. Purpose of soft liners
Answer:

Purpose Of Soft Liners

• To protect soft tissues by acting as a cushion
• Used when irritation of the mucosa occurs
• Used in areas of severe undercut and congenital or acquired defects of the palate

Question 9. Crazing in acrylic resin
Answer:

Crazing In Acrylic Resin

• Crazing is the formation of surface cracks on the denture base resin
• It can be microscopic or macroscopic in size

Crazing In Acrylic Resin Causes:

• Mechanical stresses
• Attack by a solvent
• Incorporation of water

Crazing In Acrylic Resin Prevention:

• Using cross-linked acrylics
• Tin foil separating media
• Metal molds

Question 10. Physical stages in the mixing of heat cure acrylic resins
Answer:

Physical Stages In The Mixing Of Heat Cure Acrylic Resins

• Wet sandy stage
• Sticky stage
• Dough stage
• Rubbery stage
• Stiff stage

Question 11. Functions of separating medium.
Answer:

Functions Of Separating Medium

• To achieve a clean surface for new dentures
• Prevent direct contact between denture base and model
• Prevent entry of water from mold Into resin
• Prevent penetration of monomer into the model
• Help in easy retrieval of dentures from mold

Dental Ceramics Important Notes

1. Dental Ceramics

• It is a compound of metallic and nonmetallic compounds
• They are most suitable as tooth-colored restorative materials
• They have high compressive strength and low tensile strength
• It is insoluble and impermeable to oral fluids
• Bonding of porcelain to metal occurs by both chemical and mechanical bonding

2. Dental Ceramics Classification

3. Dental Ceramics Composition

4. Dental Ceramics Metallic oxides

They are added to obtain various shades

5. Dental Ceramics Feldspar

• They act as basic glass former, flux, matrix, and surface glaze
• It undergoes incongruent melting at 1150-1530°C
• It forms leucite crystals

Read And Learn More: Dental Materials Question and Answers

6. Dental Ceramics Glazing

• It is a process that gives a smooth and glossy surface, enhances esthetics, and helps in hygiene
• Glazed porcelain is stronger than unglazed porcelain
• The self-glaze is more permanent than the applied glaze

7. Dental Ceramics CAD-CAM

• Computer-Aided Design and Computer Aided Machining
• It is used to prepare metal and ceramic inlays and crowns without the need for impression and casting procedure

8. Dental Ceramics Stages of firing

Dental Ceramics Long Essays

Question 1. Classify dental casting alloys. Describe mechanical properties and add a note on dental ceramics
Answer:

Classification of Dental Casting Alloys:

• According to use
  • Alloys for all metal and resin veneer restoration
  • Alloys for metal-ceramic restoration
  • Alloys for removable dentures
• According to the yield strength and percent elongation
  • Type 1- soft
  • Type 2- medium
  • Type 3- hard
  • Type 4- extra hard
• According to nobility
  • High noble metal alloys
  • Noble metal alloys
  • Predominantly base metal alloys
  • Base metal
• According to the major elements
  • Gold alloys
  • Silver alloys
  • Palladium alloys
  • Nickel alloys

• • Cobalt alloys
  • Titanium alloys
• According to the three major elements
  • Gold-palladium-silver
  • Palladium-silver-tin
  • Nickel-chromium-molybdenum
• According to the number of alloys present
  • Binary
  • Tertiary
  • Quaternary

Dental Ceramics:

It is an inorganic compound with nonmetallic properties typically consisting of oxygen and one or more metallic or semi-metallic elements that are formulated to produce the whole or part of ceramic-based dental prosthesis

Dental Ceramics Classification:

• According to the firing temperature
  • High fusing
  • Medium fusing
  • Low fusing
  • Ultra-low fusing
• According to the type
  • Feldspathic porcelains
  • Leucite-reinforced glass ceramics
  • Alumina reinforced porcelain
  • Zirconia reinforced ceramics
• According to the function of the restoration
  • Core ceramics
  • Opaque ceramic
  • Veneering ceramic
• According to microstructure
  • Glass-ceramic
  • Crystalline ceramic
  • Crystal containing ceramic
• According to the fabrication process
  • Condensable ceramics
  • Heat pressed ceramic
  • Castable ceramic
  • Machinable ceramics

Dental Ceramics Composition:

Dental Ceramics Properties:

• Strength
• Glazed porcelain is stronger than ground porcelain
• Compressive strength- 331 MPa
• Low tensile, shear, and flexure strength
• Modulus of elasticity- 69 GPa
• Surface hardness- 460 KHN
• Wear resistance
• More resistant to wear
• Thermal properties
• Low thermal conductivity
• Coefficient of thermal expansion- 6.4-7.8 * 10 6/ °C
• Specific gravity
• 2.242
• Dimensional stability
• It is dimensionally stable after firing.
• Chemical stability
• Insoluble and impermeable to oral fluids
• Esthetics properties
• Excellent esthetics
• Biocompatibility
• Biocompatible with the oral tissues

Dental Ceramics Uses:

• Single unit crown
• Porcelain jacket crown
• Metal ceramic crown
• Castable glass ceramic crown
• Porcelain veneer for crowns and bridges
• Artificial teeth
• Inlays and Onlays
• Ceramic brackets used in orthodontic
• Implants, bioglasses

Question 2. Classify dental porcelains. Describe the methods of condensation and firing procedures
Answer:

Dental porcelains Classification:

• According to the type
  • Feldspathic porcelains
  • Leucite-reinforced glass ceramics
  • Alumina reinforced porcelain
  • Zirconia reinforced ceramics

Dental porcelains Condensation:

The process of packing the powder particles together and removing the excess water is called condensation

Condensation Purpose:

• Packs the particles together
• Minimizes porosity
• Improves strength
• Reduces firing shrinkage
• Removes excess water

Condensation Methods:

• Vibration
• Mild vibration by tapping or running serrated instrument
• The ultrasonic vibrator is also present
• Vibration brings out excess water to the surface which is blotted using absorbent paper
• Spatulation
• A small spatula is used to apply and smooth wet porcelain
• Dry powder
• It is placed on the opposite side of a wet increment

Dental porcelains Firing:

• The process of sintering and fusing the particles of the condensed mass is known as firing
• It is done in a porcelain furnace

Firing Method:

Firing Stages:

Question 3. What are metal-ceramic restorations? What are the ideal requirements for metal-ceramic restorations? Mention its composition.
Answer:

Metal Ceramic Restoration:

Metal ceramic restorations are those alloys that are compatible with porcelain and capable of bonding to it

Metal Ceramic Restoration Ideal Requirements:

• Its melting temperature should be higher than porcelain firing temperatures
• It should be able to resist creep
• Its coefficient of thermal expansion should be compatible with that of porcelain
• It should have a high stiffness
• It should not stain or discolor porcelain

Metal Ceramic Restoration Composition:

Dental Ceramics Short Essays

Question 1. Requirements of metal-ceramic alloys
Answer:

Requirements of metal-ceramic alloys

• Its melting temperature should be higher than porcelain firing temperatures
• It should be able to resist creep
• Its coefficient of thermal expansion should be compatible With that of porcelain
• It should have a high stiffness
• It should not stain or discolor porcelain

Question 2. Aluminous porcelain and its advantages
Answer:

Aluminous porcelain 

• Aluminous porcelain was developed by McLean in 1965
• It contains increased alumina content compared to conventional porcelain

Aluminous porcelain Use:

• Used in the construction of the core layer of the porcelain jacket crown
• Conventional body and enamel porcelain are then condensed over it

Aluminous porcelain Advantages:

• More esthetic
• Strength is twice that of conventional porcelain
• Less expensive
• Requires less removal of tooth structure

Question 3. Chrome-cobalt alloy
Answer:

Chrome-cobalt alloy

• They possess high strength
• Have excellent corrosion resistance
• They are bright luster, hard, strong alloy

Chrome-cobalt alloy Application:

• Denture base
• Cast removable partial denture
• Crown and fixed partial dentures
• Bar connectors

Chrome-cobalt alloy Composition:

Question 4. Drawbacks and benefits of metal Ceramics
Answer:

Metal Ceramics Drawbacks:

• Less flexibility
• High modulus of elasticity
• Low tensile strength
• Sufficient bulk of metal is required
• The shape of the crown out in line with the anatomic form of adjacent teeth

Metal Ceramics Benefits:

• Permanent esthetic quality
• Good resistance to fracture
• No wear occurs by abrasion
• No staining
• Less tooth preparation required

Question 5. Dicor
Answer:

Dicor

• Dicor is the first commercially available castable ceramic material for dental use
• It was developed by Dentsply International
• It is a castable glass that is formed into an inlay, facial veneer, or full crown restoration by a lost wax casting process similar to that employed for metals
• It is not used nowadays because of
• Very low tensile strength
• Tends to fracture easily
• More amount of tooth preparation is required

Question 6. Methods of strengthening Dental porcelain.
Answer:

1. Development of residual compressive stress

• Ion exchange or chemical tempering
• Involves the exchange of larger potassium ions for the smaller sodium ions
• Thermal tempering
• Involves cooling the surface while it is hot and in a molten state
• Thermal compatibility
• The coefficient of thermal contraction of metal is slightly larger than porcelain e This mismatch increases the strength of porcelain

2. Disruption of crack propagation

• Dispersion of crystalline phase
• Transformation toughening with partially stabilized zirconia

Dental Ceramics Short Question And Answers

Question 1. Aluminous porcelain
Answer:

Aluminous porcelain

• Aluminous porcelain was developed by McLean in 1965
• It contains increased alumina content compared to conventional porcelain

Aluminous porcelain Use:

• Used in the construction of the core layer of the porcelain jacket crown
• Conventional body and enamel porcelain are then condensed over it

Question 2. Condensation and firing of porcelain
Answer:

Porcelain Condensation:

The process of packing the powder particles together and removing the excess water is called condensation

Condensation Purpose:

• Packs the particles together
• Minimizes porosity
• Improves strength
• Reduces firing shrinkage
• Removes excess water

Porcelain Firing

• The process of sintering and fusing the particles of the condensed mass is known as firing
• It is done in a porcelain furnace

Question 3. Ceramic crown
Answer:

Ceramic crown Advantages:

• Superior esthetics
• Excellent translucency
• Requires slightly more preparation of the facial surface
• The appearance can be influenced and modified by selecting different colors of luting agents

Ceramic crown Disadvantages:

• Reduced strength
• Difficult to maintain a well-finished margin
• Cannot be used on extensively damaged teeth
• Need large connectors
• This leads to the impingement of the interdental papilla
• Wear of opposing teeth

Question 4. Glazing
Answer:

Glazing Uses:

• To obtain a smooth glossy surface
• To enhance aesthetics
• To reduce crack propagation
• The strength of glazed porcelain is much more than unglazed porcelain

Glazing Types:

• Overglaze
  • Glaze powder is mixed with a special liquid
  • The firing temperature is low
  • Chemical durability is low o Has high flux content
  • Contains more glass modifiers
  • Imparts glossy surface
• Self glaze
  • Restoration is subjected to a controlled heating
  • All the constituents are completely melted to form a single-phase glass
  • Has a high fusion temperature

Glazing Objectives:

• Enhances aesthetics
• Enhances hygiene
• Improves strength
• Reduces wear of opposing teeth

Question 5. Castable ceramics
(or)
Advantages of castable ceramics
Answer:

Castable ceramics

• Ease of fabrication
• Improved esthetics
• Minimal processing shrinkage
• Good marginal fit
• Moderately high flexural strength
• Low thermal expansion
• Minimal abrasiveness

Question 6. Role of feldspar in porcelain
Answer:

Role of feldspar in porcelain

• It acts as a flux, matrix, and surface glaze
• When it is mixed with metal oxides and fried at high temperatures it can form a glass phase that is able to soften and flow slightly
• During firing feldspar fuses and acts as a matrix and binds silica and kaolin

Question 7. Types of glazes
Answer:

Types of glazes

• Overglaze
• Glaze powder is mixed with a special liquid
• The firing temperature is low
• Chemical durability is low e Has high flux content
• Contains more glass modifiers o Imparts glossy surface
• Self glaze
• Restoration is subjected to a controlled heating
• All the constituents are completely melted to form a single-phase glass
• Has a high fusion temperature

Question 8. Uses of glazing
Answer:

Uses of glazing

• To obtain a smooth glossy surface
• To enhance aesthetics.
• To reduce crack propagation
• The strength of glazed porcelain is much more than unglazed porcelain

Question 9. Porcelain condensation techniques.
Answer:

Porcelain condensation techniques

• Vibration
• Mild vibration by tapping or running serrated instrument
• An ultrasonic vibrator is also present
• Vibration brings out excess water to the surface which is blotted using absorbent paper
• Spatulation
• A small spatula is used to apply and smooth wet porcelain
• Dry powder
• It is placed on the opposite side of a wet increment

Question 10. Classification of dental casting alloys.
Answer:

1. Dental casting alloys According to use

• Alloys for all metal and resin veneer restoration
• Alloys for metal-ceramic restoration
• Alloys for removable dentures

2. Dental casting alloys According to the yield strength and percent elongation

• Type 1 – soft
• Type 2 – medium
• Type 3 – hard
• Type 4 – extra hard

3. Dental casting alloys According to the nobility

• High noble metal alloys
• Noble metal alloys
• Predominantly base metal alloys
• Base metal

4. Dental casting alloys According to the major elements

• Gold alloys
• Silver alloys
• Palladium alloys
• Nickel alloys
• Cobalt alloys
• Titanium alloys

5. Dental casting alloys According to the three major elements

• Gold-palladium-silver
• Palladium-silver-tin
• Nickel-chromium-molybdenum

6. Dental casting alloys According to the number of alloys present

• Binary
• Tertiary
• Quaternary

Dental Cements Important Notes

1. Classification Of Blocks Of Cement

• According To A Setting Reaction
  • Acid-base reaction
  • Polymerizing cement – resin cement
  • Dual-core cement a Tri cure cement
• Based On Application
  • Type 1 – luting types of cement
  • Type 1 – fine grain for cementation
  • Type 2 – medium grain for bases, orthodontic purposes
  • Type 2 – restorative application
  • Type 3 – liner or bases
• Based on function

2. Silicate

Silicate Composition

• Silicate Properties
  • Compressive strength – 180 Mpa
  • Setting time – 3-8 min o Hardness – 70 KHN
  • Severe irritant to pulp
  • It has high solubility to oral fluids
  • It has anti-cariogenic property
  • The refractive index is similar to enamel and dentin
  • Contra indicated in mouth breathers
  • Finishing and polishing should be delayed to several days
  • The surface is protected by a coating of varnish

3.

4. Zinc Phosphate Cement

Zinc Phosphate Cement Composition

• Zinc Phosphate Cement Setting Reaction
  • Phosphoric acid reacts with zinc oxide forming zinc phosphate
  • Aluminum on liquid forms complexes with phosphoric acid to form zinc alumina phosphate gel
  • Prolonged speculation retards the setting reaction
  • Adding powder in increments increases the setting and mixing time
  • Cooling the mixing slab increases the setting time

5. Zinc Polycarboxylate Cement

Zinc Polycarboxylate Cement Composition

Zinc Polycarboxylate Cement Properties

• Less irritant to pulp
• the pH of the liquid is 1.7
• Cement bonds chemically to the tooth structure due to the chelation of the carboxyl group with calcium on the tooth
• It is a good thermal insulator so can be used as bases

6. Zinc Oxide Eugenol Cement

Zinc Oxide Eugenol Cement Classification

• Type 1 – for temporary restoration
• Type 2 – for permanent restoration
• Type 3 – temporary filling and bases
• Type 4 – cavity liners

Zinc Oxide Eugenol Cement Composition

Zinc Oxide Eugenol Cement Properties

• Solubility is highest
• Least irritant
• It has a soothing effect on pulp
• Modified ZOE cement
• EBZ alumina modified
• Polymer-reinforced ZOE cement
• Types of cement containing vanillate esters

7. Calcium Hydroxide Cement

• It is weak cement
• Uses
• For direct and indirect pulp capping
• In apexification
• In Pulpotomy
• As a root canal sealer
• As root canal disinfectant
• As cavity liner and base

Calcium Hydroxide Cement Properties

• Solubility in water is high
• Alkaline in nature
• pH is 11
• It is an antibacterial agent

8. Varnish

Cavity varnish is a solution of one or more resins which when applied onto the cavity walls evaporates leaving a thin resin film that serves as a barrier between the restoration and the dentinal tubules

Varnish Composition

Natural gum such as copal, rosin, or synthetic rosin dissolved in organic solvents such as alcohol, acetone, or ether

Varnish Applications

• In amalgam restoration
• Prevents discoloration by preventing the penetration of silver Ions into the dentin
• Decreases marginal leakage
• As surface coating over GIC cement, silicate
• Over metallic restoration to prevent galvanic shock

Varnish Contraindications

• Composite resins
• GIC and polycarboxylate restoration

Varnish Properties

• Possesses neither mechanical strength nor provides thermal Insulator
• Insoluble in oral fluids

9. Liner

• A cavity liner is like cavity varnish to provide a barrier against the passage of irritants from cement and to reduce the sensitivity of freshly cut dentin
• They are volatile or aqueous suspensions of zinc oxide or calcium hydroxide that can be applied to the cavity surface
• They neither possess strength nor a thermal insulator
• Calcium hydroxide or GIC liner should be used under composite restoration
• Calcium hydroxide stimulates reparative dentin formation
• ZOE has an obtundent effect on pulp

10. Bases

• It is a thicker layer of cement placed under restoration to
• Encourage recovery of injured pulp
• Protect the pulp from thermal, chemical, and galvanic insult
• Serve as a substitute for dentin that has been destroyed by caries or cavity preparation

Bases Types

• Low strength bases – ZOE, calcium hydroxide
• High-strength bases – zinc phosphate, GIC, polycarboxylate

Bases Properties

• Should have a minimal thickness of 0.75 mm
• Must have sufficient strength to withstand forces of condensation and masticatory stresses
• Does not prevent microleakage and acid penetration
• With zinc phosphate as a base, a sealant is placed first followed by a base
• With calcium hydroxide, ZOE, GIC, or polycarboxylate, the base is placed first followed by a sealant

11. Fluoride-Releasing Cement

• Fluoride-releasing cements are silicate, GIC, silicophosphate, and polycarboxylate
• Fluoride has anti-cariogenic properties
• It inhibits demineralization and enhances remineralization of carious enamel
• GIC has the highest fluoride release property

12. Factors Affecting The Setting Time Of Cement

• Cooling of mixing slab
• Decreased powder-liquid ratio
• Prolonged mixing time
• Loss of water from the liquid

Dental Cement Long Essays

Question 1. Describe the composition, properties, and manipulation of glass ionomer cement.
Answer:

Glass Ionomer Cement:

Glass ionomer cement is colored cardiogenic restorative material

Glass Ionomer Cement Composition:

• Glass Ionomer Cement Powder
• It is an acid-soluble calcium fluoro aluminosilicate glass

Glass Ionomer Cement Liquid

Glass Ionomer Cement Properties:

• Physical properties

• Biological Properties Or Anti-Cariogenic Properties
  • Glass ionomer cement releases fluoride in comparable amounts
  • Carried out for an extended period
  • This is taken up by enamel
  • Thus inhibits caries
  • Moreover, they have the potential to reduce the infiltration of oral fluids at the cement tooth interface
  • Thus preventing secondary caries
• Biocompatibility
  • It is biocompatible
  • Has a mild pulpal response
  • Adhesion
  • It adheres well to enamel and dentin
  • Esthetics
  • Inferior to silicates and composites
  • Lacks translucency

Glass Ionomer Cement Manipulation:

• Tooth Surface Preparation
  • Pumice slurry is used to remove the smear layer
  • Conditioning is done
  • Etching with 37% phosphoric acid for 10-20 sec
  • Rinsing with water for 20-30 sec
  • The next surface is dried but not desiccated
• Preparation Of Material
  • Powder-liquid ratio recommended by the manufacturer is followed
  • Powder and liquid are dispensed over a paper pad just before mixing
  • The powder is divided into 2 or more increments
  • The powder is incorporated rapidly into the liquid using a stiff plastic spatula
  • Subsequent increments are incorporated and mixed using a folding technique
  • Mixing time-45 sec
• Placement Of Material
  • The cavity should be slightly overfilled
  • The surface should be covered with a plastic matrix to protect the setting cement from losing or gaining water during the initial set
  • The matrix is left in place for at least 5 min
  • Upon removal of the matrix, the surface is again protected with
  • Special varnish
  • Unfilled light-cured resin bonding agent
  • Petroleum jelly
  • Finishing of restoration
  • Should be delayed for 24 hours

Question 2. Classify dental cement. Write the composition, properties, and uses of polycarboxylate cements.
Answer:

Dental Cement Classification:

• According To The Setting Reaction
  • Acid-base reaction cement
  • Formulated as powder and liquid
  • Polymerizing cement
  • Sets by polymerizing reaction
  • Example. Resin cement
  • Dual-core cement
  • Set by acid-base reaction and by light-activated or chemically activated polymerization mechanism
  • Tri cure cement
  • Utilizes all three mechanisms for hardening
• Based On Application
  • Type 1- luting cement
  • Type 1- fine grain for cementation
  • Type 2- medium grain for bases, orthodontic purpose
  • Type 2- restorative application
  • Type 3- liner or base application
• Based On Functions

Zinc Polycarboxylate Cement:

Zinc Polycarboxylate Cement Composition:

• Zinc Polycarboxylate Cement Powder
  • Zinc oxide- the basic ingredient
  • Magnesium oxide
  • Modifier
  • Aids in sintering
  • Bismuth and aluminum oxide- occur in small amounts
  • Stannous fluoride
  • Increases strength
  • Modifies setting time
  • Imparts anti-cariogenic properties
• Zinc Polycarboxylate Cement Liquid
  • Polyacrylic acid
  • The copolymer of acrylic acid with other unsaturated carboxylic acids

Zinc Polycarboxylate Cemen Properties: Physical properties

• Zinc Polycarboxylate Cement Biocompatibility
  • Mild pulpal response
  • Adhesion
  • Excellent adhesion
  • Polyacrylic acid is believed to react with calcium ions via carboxyl groups on the surface of enamel and dentin
  • The bond strength of enamel is greater
  • Optical properties
  • It is very opaque
  • Thermal properties
  • It is a thermal insulator

Zinc Polycarboxylate Cement Uses:

• Cementation of restoration
• As bases and liners
• As intermediate restoration
• Luting of permanent restoration
• In orthodontics- the cementation of bands
• In endodontics- as root canal filling material

Question 3. Mention the types of glass ionomer cement. Add a note on the mechanism of adhesion of glass ionomer to the tooth.
Answer:

Types of Glass Ionomer Cement:

• Type 1- for luting
• Type 2- for restoration
• Type 3- as liner and bases

Glass Ionomer Cement Mechanism of Adhesion:

• The exact mechanism has not yet been identified
• Glass ionomer bonds chemically
• It primarily involves the chelation of carboxyl groups of the polyacids with the calcium in the apatite of enamel and dentin
• The bond strength of enamel is higher than that of dentin because
• Greater inorganic content of enamel
• Greater homogeneity

Question 4. Give the biological properties of glass ionomer. Add a note on the recent modifications of GIC.
Answer:

Glass Ionomer Cement:

Glass Ionomer Cement Biological Properties:

• Glass ionomer cement releases fluoride in comparable amounts
• Carried out for an extended period
• This is taken up by enamel
• Thus inhibits caries
• Moreover, they have the potential to reduce the infiltration of oral fluids at the cement tooth interface
• Thus preventing secondary caries

Recent Modification of GIC:

• Introduced to improve
• Strength
• Fracture toughness
• Resistance to wear
• They are

1. Metal-modified GIC

• Metal-modified GIC Types
  • Silver alloy admixed
  • Spherical amalgam alloy powder is mixed with type 2 GIC powder
  • Cermet
  • Silver particles are bonded to glass particles
• Metal-modified GIC Uses
  • Restoration of small class 1 cavity
  • For the core build-up of grossly destructed teeth

2. Resin-modified GIC

• Resin-modified GIC Types
  • Resin-modified glass ionomer cement
  • Compomers or polyacid modified composites
• Resin-modified GIC Uses
  • Restoration of class 1,3 or 5 cavities
  • As bases and liners
  • As adhesives for orthodontic brackets
  • Cementation of crowns and FPDs
  • Repair of damaged amalgam cores or cusps
  • Retrograde root filling
• Resin-modified GIC Composition
  • Powder
  • Fluorosilicate glass
  • Initiator
  • Liquid
  • 15-25% resin component (HEMA)
  • Polyacrylic acid
  • Water

Question 5. State the ideal requisites of luting cement. Give the composition, chemistry of setting, and properties of glass ionomer cement.
Answer:

Ideal Requisites Of Luting Cement:

1. Ideal Requisites Of Luting Cement Biological

• Should be nontoxic
• Should be non carcinogenic
• Should not cause any systemic reaction
• Should be cariostatic

2. Ideal Requisites Of Luting Cement Chemical

• Should be chemically inert
• Should have negligible solubility to oral fluids
• Should bond chemically to enamel and dentin
• pH should be neutral

3. Ideal Requisites Of Luting Cement Rheological

• Should have low film thickness to enable easy flow
• Should have longer mixing and working time
• Should have a shorter setting time

4. IIdeal Requisites Of Luting Cement Mechanical

• Should have high compressive strength, tensile strength, and modulus of elasticity
• Should exhibit minimum dimensional changes

5. Ideal Requisites Of Luting Cement Thermal

• Should be a good thermal insulator
• The coefficient of thermal expansion should be similar to the tooth

6. Ideal Requisites Of Luting Cement Optical

• Should not alter the color of the tooth or prosthesis
• Should have adequate radio parity

7. Ideal Requisites Of Luting Cement Miscellaneous

• Should be easy to manipulate
• Inexpensive
• Should have a longer shelf life

Glass Ionomer Cement Composition:

• Powder:
• It is an acid-soluble calcium fluoro aluminosilicate glass

Chemistry Of Setting

1. Chemistry Of Setting Leaching Of Ions

• When GIC powder and liquid are mixed, the acid attacks the glass particles
• This causes the leaching of calcium, aluminum, sodium, and fluoride ions over the surface

2. Chemistry Of Setting Hydration

• Water slowly hydrates the matrix
• This adds to the strength of the cement

3. Chemistry Of Setting Silica gel sheath

• • The unreacted glass particles are sheathed by a silica gel
  • This is formed by the leached ions
• Biological Properties Or Anti-Cariogenic Property
  • Glass ionomer cement releases fluoride in comparable amounts
  • Carried out for an extended period
  • This is taken up by enamel
  • Thus inhibits caries
  • Moreover, they have the potential to reduce the infiltration of oral fluids at the cement tooth interface
  • This prevents secondary caries
  • Biocompatibility
  • It is biocompatible
  • Has a mild pulpal response
  • Adhesion
  • It adheres well to enamel and dentin
  • Esthetics
  • Inferior to silicates and composites
  • Lacks translucency

Question 6. Classify Dental cements based on their uses and describe the composition, setting reaction, and properties of Zinc Phosphate Cement.
Answer:

Classification Of Dental Cement:

Dental Cement Based IOn Their Uses:

• Type 1 – Luting cement
• Type 1 – fine grain for cementation
• Type 2 – medium grain for bases, orthodontic purposes
• Type 2 – restorative application
• Type 3 – liner or base application

Zinc Phosphate Powder:

Zinc Phosphate Liquid:

Zinc Phosphate Setting Reaction:

• When the powder is mixed with liquid
• Phosphoric acid attacks the surface of particles and releases zinc ions
• Aluminum combines with phosphoric acid and zinc ions
• Results in the formation of zinc aluminophosphate gel
• The reaction is exothermic

Zinc Phosphate Properties:

Dental Cements Short Essays

Question 1. Calcium hydroxide
Answer:

Calcium Hydroxide

Calcium Hydroxide is a relatively weak cement

Calcium Hydroxide Uses:

• For direct pulp capping
• For indirect pulp capping
• As low-strength bases
• In apexification

Calcium Hydroxide Composition:

Calcium Hydroxide Base Paste

Calcium Hydroxide Catalyst Paste

Calcium Hydroxide Properties:

• Mechanical properties
• Compressive strength-10-27 Mpa
• Tensile strength-1 Mpa
• Modulus of elasticity-0.37%
• Thermal properties
• Provide thermal insulation in thick layers
• Solubility
• Solubility is high- 0.4-7.8%
• Biological properties
• It is alkaline in nature
• Adhesion
• Does not adhere in the presence of blood, water, or saliva

Question 2. Liners And Bases
Answer:

Liners And Bases

• Liners are fluid materials that adapt more readily to all aspects of a tooth
• Creates uniform even surface
• Aids in the adaptation of materials such as amalgam
• Has poor strength so cannot be used alone

Liners And Bases Indications:

• Pulpal protection- Provide a barrier against the passage of irritants from cement
• Formation of reparative dentin- reduces the sensitivity of freshly cut dentin

Liners And Bases Materials Used:

• ZOE
• Calcium hydroxide
• Flowable composites
• GIC

Liners And Bases Bases:

• A base is a layer of cement placed beneath a permanent restoration to encourage recovery of injured pulp
• It is applied in much thicker layers

Liners And bases Functions:

• Protects the pulp against thermal injury, galvanic shock, chemical irritation
• Withstand condensation forces during placement of a restoration
• Resist fracture under any masticatory stresses induced on the restorations
• Serve as a substitute for protective dentin

Liners And Bases Types:

• High strength bases
• Zinc phosphate,
• Zinc Polycarboxylate
• GIC,
• Reinforced ZOE
• Low strength bases
• Calcium hydroxide
• ZOE

Liners and Bases Properties:

• Provide thermal protection to pulp
• Serve s barrier against penetration of irritants
• Have a beneficial effect on pulp
• Have sufficient strength

Question 3. Cavity varnish
Answer:

Cavity Varnish

Cavity Varnish is a solution of one or more resins which when applied onto the surface, evaporates leaving a thin resin film

Cavity Varnish Composition:

Natural gum such as copal, rosin, or synthetic resin dissolved in an organic solvent like alcohol, acetone, or ether

Cavity Varnish Manipulation:

• Applied using a brush or small pellet
• Several thin layers are applied
• Each layer is allowed to dry before applying next
• On drying it produces small pinholes which get filled by the next layer

Cavity Varnish Advantages:

• Improves the sealing ability of amalgam
• Reduces post-operative sensitivity
• Prevents discoloration of tooth

Cavity Varnish Indications:

• Reduces pulpal irritation
• Reduces infiltration of irritating fluids through marginal areas
• Prevents penetration of corrosion products of amalgam into dentinal tubules
• Reduces tooth discoloration
• Used as a surface coating over certain restorations to protect from dehydration
• Protect against galvanic shock when applied over metallic restorations
• Fluoride-containing vanishes releases Fluoride

Cavity Varnish Contraindications:

• Under composite resin
• Under GIC

Question 4. Resin-modified glass ionomer
Answer:

Resin-Modified Glass Ionomer

• Introduced as Vitreband (3M)
• Incorporate the best properties of both GIC and composite resin

Resin-Modified Glass Ionomer Composition:

• Powder
• Fluorosilicate glass
• Initiator
• Liquid
• 15-25% resin component (HEMA)
• Polyacrylic acid
• Water

Resin-Modified Glass Ionomer Advantages:

• Long working time
• Good adaptation
• Chemical adhesion
• Fluoride release
• Improved aesthetics
• Good strength

Resin-Modified Glass Ionomer Disadvantages:

• Polymerization shrinkage
• Limited depth of cure

Question 5. Uses of glass ionomer cement
Answer:

Glass Ionomer Cement Uses:

• As pit and fissure sealant
• Due to anticariogenicity and adhesive properties
• As liner and bases
• Beneath composite and amalgam
• As luting agents
• For cementation of crowns, bridges, veneers, and orthodontic bands
• As orthodontic bracket adhesive
• For restoration of class 3 and class 5 lesions
• Fissure sealing
• Restoration of root caries
• High caries risk patients
• Temporary restoration
• Core build-up
• Atraumatic restorative treatment

Question 6. Recent advances in glass ionomers
Answer:

1. Glass ionomers Metal-modified GIC

• Metal-modified GIC Types
  • Silver alloy admixed
  • Spherical amalgam alloy powder is mixed with type IIGIC powder
  • Cermet
  • Silver particles are bonded to glass particles
• Metal-modified GIC Uses
• Restoration of small class 1 cavity
• For the core build-up of grossly destructed teeth

2. Glass ionomers Resin-modified GIC

• Resin-modified GIC Types
  • Resin-modified glass ionomer cement
  • Compomers or polyacid modified composites
• Resin-modified GIC Uses
  • Restoration of class 1,3 or 5 cavities
  • As bases and liners
  • As adhesives for orthodontic brackets
  • Cementation of crowns and FPDs
  • Repair of damaged amalgam cores or cusps
  • Retrograde root filling

Resin-modified GIC Composition:

• Powder
• Fluorosilicate glass
• Initiator
• Liquid
• 15-25% resin component (HEMA)
• Polyacrylic acid
• Water

Question 7. Classification of glass ionomers
Answer:

Glass ionomers Classification:

1. Type 1- for luting
2. Type 2- for restoration
3. Type 3- as liner and bases

Question 8. Luting cement
Answer:

Luting implies the use of a moldable substance to seal a space or to cement two components together

Luting cement The cement used is:

• Zinc phosphate
• Zinc oxide eugenol
• Zinc polycarboxylate
• Glass ionomer cement
• Resin modified GIC
• Compomer
• Resin cement

Luting Cement Factor Affecting its Selection:

• Working time
• Setting time
• Consistency
• Ease of removal of excess material

Question 9. Root canal sealants
Answer:

Root Canal Sealants Requirements:

• Should be tacky
• Should create a hermetic seal
• Should be radiopaque
• Should be miscible
• Should be bacteriostatic
• Should set slowly
• Should be insoluble in oral fluids
• Should not shrink
• Should not stain

Root Canal Sealants Functions:

• Antimicrobial agent
• Lubricant
• Binding agent
• Fills die space between material and canal walls
• As obturating material
• Give radiopacity

Root Canal Sealants Classification:

• Eugenol
• Silver containing
• Kerr sealer
• Silver free
• Grossman’s sealer
• Medicated
• Iodoform
• Non-eugenol
• Hydron
• Glass ionomer
• Diaket

Question 10. Glass cermets
Answer:

Glass Cermets

• Introduced by McLean and Gasser
• It is a fusion of glass ionomer to powder like silver or gold

Glass Cermets Manufacture:

Glass Cermets Advantages:

• Better abrasion resistance
• Higher flexure strength

Glass Cermets Disadvantage

Poor esthetics

Question 11. Gutta-percha
Answer:

Gutta-percha

Gutta-percha is an endodontic filling material

Gutta-percha Composition:

Gutta-percha Forms:

• Alpha
• Beta
• Amorphous

Gutta-percha Advantages:

• Compatibility
• Inertness
• Dimensional stable
• Tissue tolerance
• Radiopacity
• Plasticity
• Dissolve in some solvent

Gutta-percha Disadvantages:

• Lack of rigidity
• Lack of adhesiveness
• Easily displaced

Question 12. Zinc phosphate cement
Answer:

Zinc Phosphate Cement

Zinc phosphate is the oldest of the luting cement

Zinc Phosphate Cement Manipulation:

• A cool mixing slab should be employed to prolong working and setting time
• The powder is divided into increments
• The liquid is dispensed just before mixing
• Mixing is initiated by the addition of a small amount of powder with brisk speculation
• Each increment is mixed for 15-20 sec
• A large area of the slab is used to dissipate exothermic heat
• Completion of mixing usually requires approximately 1.5-2 min

Dental Cement Short Question And Answers

Question 1. Manipulation of zinc phosphate cement
Answer:

Manipulation Of Zinc Phosphate Cement

• A cool mixing slab should be employed to prolong working and setting time
• The powder is divided into increments
• The liquid is dispensed just before mixing
• Mixing is initiated by the addition of a small amount of powder with brisk speculation
• Each increment is mixed for 15-20 sec
• A large area of the slab is used to dissipate exothermic heat
• Completion of mixing usually requires approximately 1.5-2 min

Question 2. Polycarboxylate cement
Answer:

Polycarboxylate Cement Composition

• Polycarboxylate Cement Powder
  • Zinc oxide- the basic ingredient
  • Magnesium oxide
  • Modifier
  • Aids in sintering
  • Bismuth and aluminum oxide- occur in small amounts
  • Stannous fluoride
  • Increases strength
  • Modifies setting time
  • Imparts anti-cariogenic properties
• Polycarboxylate Cement Liquid
  • Polyacrylic acid
  • The copolymer of acrylic acid with other unsaturated carboxylic acids

Polycarboxylate Cement Uses:

• Cementation of restoration
• As bases and liners
• As intermediate restoration
• Luting of permanent restoration
• In orthodontics- the cementation of bands
• In endodontics- as root canal filling material

Question 3. Uses Of Glass Ionomer Cement
Answer:

Uses Of Glass Ionomer Cement

• As pit and fissure sealant
• Due to anticariogenicity and adhesive properties
• As liner and bases
• Beneath composite and amalgam
• As luting agents
• For cementation of crowns, bridges, veneers, and orthodontic bands
• As orthodontic bracket adhesive
• For restoration of class 3 and class 5 lesions
• Fissure sealing
• Restoration of root caries
• High caries risk patients
• Temporary restoration
• Core build-up
• Atraumatic restorative treatment

Question 4. Pulp protective cement
Answer:

Pulp Protective Cement

• Pulp protective cement is
• Cavity varnish
• Cavity liners
• Bases

Question 5. Metal modified GIC
Answer:

• Metal-modified GIC Types:
  • Silver alloy admixed
  • Spherical amalgam alloy powder is mixed with type 2 GIC powder
  • Cermet
  • Silver particles are bonded to glass particles
• Metal-modified GIC Uses:
  • Restoration of small class 1 cavity
  • For the core build-up of grossly destructed teeth

Question 6. Cavity varnish
Answer:

Cavity varnish

It is a solution of one or more resins which when applied onto the surface, evaporates leaving a thin resin film

Cavity varnish Composition:

Natural gum such as copal, rosin, or synthetic resin dissolved in an organic solvent like alcohol, acetone, or ether

Cavity varnish Indications:

• Reduces pulpal irritation
• Reduces infiltration of irritating fluids through marginal areas
• Prevents penetration of corrosion products of amalgam into dentinal tubules
• Reduces tooth discoloration
• Used as a surface coating over certain restorations to protect from dehydratio
• Protect against galvanic shock when applied over metallic restorations
• Fluoride-containing vanishes releases Fluoride

Question 7. Cavity liners
Answer:

Cavity liners

• Liners are fluid materials that adapt more readily to all aspects of a tooth
• Creates uniform even surface
• Aids in the adaptation of materials such as amalgam
• Has poor strength so cannot be used alone

Cavity liners Indications:

• Pulpal protection- Provide a barrier against the passage of irritants from cement
• Formation of reparative dentin- reduces the sensitivity of freshly cut dentin

Cavity liners Materials Used:

• ZOE
• Calcium hydroxide
• Flowable composites
• GIC

Question 8. Uses of Polycarboxylate
Answer:

Uses of Polycarboxylate

• Cementation of restoration
• As bases and liners
• As intermediate restoration
• Luting of permanent restoration
• In orthodontics- the cementation of bands
• In endodontics- as root canal filling material

Question 9 Uses of calcium hydroxide
Answer:

Uses Of Calcium Hydroxide

• For direct pulp capping
• For indirect pulp capping
• As low-strength bases
• In apexification

Question 10. Intermediate restorative materials
Answer:

Intermediate Restorative Materials Objectives:

• Maintain esthetics
• Act as a space maintainer
• Allow functioning
• Determine occlusion
• Establish phonetics
• Seal and insulate the prepared tooth
• Prevent passive eruption of the tooth
• Prevent pathologic migration

Intermediate Restorative Materials Requirements:

• Good marginal adaptation
• Optimal strength
• Plaque resistant surface
• Economical
• Easy to manipulate
• Dimensionally stable

Intermediate Restorative Materials Purpose:

• Pulp protection
• Act as a sedative
• Soft tissue protection
• Protect weakened tooth protection
• Maintain the esthetics

Intermediate Restorative Materials Used:

• For intra-coronal preparation
  • Guttapercha
  • Zinc oxide eugenol
  • Zinc phosphate
  • Zinc polycarboxylate
  • Glass ionomer
  • Calcium hydroxide
• For extra coronal
  • Polycarbonate crown
  • Aluminum cylinder
  • Stainless steel crown
  • Celluloid crown
  • Indirect acrylic restoration

Question 11. Biological property of silicate cement
Answer:

Biological Property Of Silicate Cement

• The incidence of secondary caries with silicates is less
• Proximal caries occurrence is less
• The anti-cariogenic property is due to the presence of 15% fluoride in the cement
• Fluoride release is slow and occurs throughout the life of the restoration
• Thus it was used as an anti-cariogenic agent before GIC

Question 12. Advantages and disadvantages of zinc Polycarboxylate cement.
Answer:

Zinc Polycarboxylate Cement Advantages:

• Comparatively less pulpal irritant
• Chemical bond to the tooth

Zinc Polycarboxylate Cement Disadvantages:

Limited fluoride released when compared to GIC

Equilibrium Phases In Cast Alloys Important Notes

1. Equilibrium Phases In Cast Alloys Eutectic Alloys

• It is an alloy for which the component metals have limited solid solubility
• They Examplehibit complete liquid solubility
• Example: silver-copper alloys

2. Equilibrium Phases In Cast Alloys Solute

• It is the substance that is dissolved in a solution
• It is mainly solid

3. Equilibrium Phases In Cast Alloys Solvent

• It is the liquid in which solute is dissolved to form a solution
• It is mainly liquid

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Chloramphenicol Short Question And Answers

Question 1. Eutectic alloys.
Answer:

Eutectic Alloys

• A eutectic alloy is an alloy for which the component metals have limited solubility.
• Silver and copper eutectic alloy is used in dentistry
• In this alloy, the temperature at which the eutectic composition melts is lower than the fusion temperature of silver or copper
• The eutectic liquid composition freezes at a constant temperature
• Such alloys are used when a lower fusion temperature is required.

Question 2. Solid solutions.
Answer:

Solid Solutions

• A solid solution is a solid crystalline phase containing two or more elements at least one of which is a metal, that is intimately combined at the atomic level
• In it, the atoms of two metals are located in the same crystal structure
• Its structure may appear to be entirely homogeneous
• Example: Silver answer palladium
• When the solution of molten silver and palladium is frozen, a solid solution is formed
• The silver atoms enter into the crystal structure of palladium and form a single solid phase.

Question 3. Quenching.
Answer:

Quenching

• Quenching is the rapid cooling of a metal object from high temperature by immersing it in oil or water
• Quenching maintains the mechanical properties of metal which can be lost by slow cooling
• The slower the quench rate, the longer the thermodynamic forces have a chance to alter the microstructure
• Quenching is most commonly performed to harden steel.

Question 4. Solute and solvent.
Answer:

Solute And Solvent

Solute And Solvent Example:

• When sugar is dissolved in water, sugar is the solute, and water is the solvent
• In palladium-silver alloy
• Both metals are completely soluble
• In it, the solvent is the metal whose atoms occupy the majority