Operative Dentistry

Ceramics Important Notes

1. Composition of porcelain

2. Feldspar

• It is the primary constituent of porcelain
• When melted it forms a crystalline phase called leucite and a glass phase
• Leucite is the basic glass former

3. Bonding of porcelain to metal Occurs by:

• Chemical bonding
• Mechanical bonding

4. Indications of ceramics

• Aesthetics
• Large defects or previous restorations
• Wide Faciolingual defect

5. Contraindication of ceramics

• Heavy occlusal forces
• Inability to maintain a dry field
• Deep subgingival preparations

Ceramics Short Answers

Question 1. Aluminous Porcelain.

Answer:

Aluminous Porcelain:

• It is a ceramic consisting of a glass matrix phase and at least 35 alumina
• Introduced by Mclean and Hughes

Preparation:

The concentration of alumina crystals and glass powder are mixed, pre fritted at 1200°C
↓
Mixture is grounded
↓
Incorporated into the glass matrix

Advantages

• Increase strength, toughness, and elasticity

Example:

• Hi-Cream

Question 2. Castable Ceramic/Dicor.

Answer:

Castable Ceramic:

Composition:

• 55% – Tetrasilicic fluoride crystals
• 45% – Glass Ceramic

Advantages:

• Marginal fit
• High strength
• High surface hardness

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• Wear resistance

Ceramics Viva Voce

1. Components of CAD/CAM – scanning device, CAD- computer-aided design, CAM – computer-assisted manufacture
2. Occlusal reduction – 1.5-2 mm
3. Occlusal divergence – 6-8° per wall
4. Isthmus width – 1.5 mm
5. Axial depth of proximal box – 1.5 mm
6. Cavosurface angle – 90°
7. The gingival margin of the proximal box should be placed supragingival

Glass Ionomer Cement Long Essays

Question 1. Describe the merits and demerits of GIC. Write about its application.°

Answer:

Merits:

• Chemical bonding to tooth structure
• Bio-compatible
• Good marginal seal
• Anticarcinogenic
• Translucent
• Conservative
• Less technique sensitive

Demerits:

• Low fracture resistance
• Low wear resistance
• Opaque
• Require moisture control

Applications:

Isolate the tooth
↓
Tooth preparation
Conservative preparation
Minimal depth
No need for a retentive feature
↓
Conditioning of tooth with 20% polyacrylic acid
↓
Manipulation Of Cement:

Use of cool, dry glass slab/paper pad along with a plastic spatula

Dispense and divide the cement powder into 2 parts

Mix individuality for 20 sec.

Total mixing time 40-60 sec.
↓
Restoration:

Carrying cement with a cement carrier

Placement into the preparation
↓
Carving
↓
Surface protection by petroleum jelly
↓
Finishing and polishing after 24 hours

Glass Ionomer Cement Short Essays

Question 1. Clinical Indications and Contraindications for GIC.

Answer:

Clinical Indications and Contraindications for GIC:

Indications:

• Restoration of Class 3, 5, and small Class 1
• Noncarious lesions
• Root caries
• Deciduous teeth
• As luting
• As liner
• Preventive restoration
• Core build-up
• Splinting
• Endodontic failure

Contraindications:

• Stress bearing areas
• Xerostomia
• Mouth breathers
• Cuspal replacement
• Areas that require aesthetics

Question 2. Uses of Glass monomers and add a note on biocompatibility.

Answer:

Uses of Glass monomers:

1. As pit and fissure sealants

• Due to anticariogenicity and adhesive properties

2. As liners and Bases – Beneath composite and amalgam

3. As luting agents

• For cementation of crowns, bridges, veneers, and orthodontic bands

4. As orthodontic brackets adhesive

5. For restorations of class 3 and class 5 lesions

6. Fissure sealing

• Use of high-viscosity GIC

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7. Restoration of root caries

• Due to adhesion to dentin
• Anticariogenicity
• Ease of use

8. High caries Risk patients

• Because of their adhesion
• Abrasion resistance
• Anticariogenicity

9. Temporary restoration

10. Core build-up

11. ART (Atraumatic Restorative Treatment)

• Used in children with poor families
• Small to moderate pit and fissure caries

Biocompatibility:

• GIC is biocompatible due to
  • Polyacrylic acid is a weak acid
  • Dissociated hydrogen ions present in GIC bound to the polymer chains
  • The formation of long polymer chains prevents their penetration into dentinal tubules
  • Postoperative sensibility due to
    • Low viscosity
    • Low initial pH of the cement

Question 3. Bilayered restoration / Sandwich technique / Laminated technology.

Answer:

Bilayered restoration:

• 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.

Steps:

Isolate the tooth
↓
Tooth preparation
Butt joint
Bevelling 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

Advantages:

• Resistance to microleakage
• Esthetics
• Flouride release
• Less polymerization shrinkage
• Biocompatible

Disadvantages:

• Technique sensitive
• Time-consuming

Question 4. Cermet Cement.

Answer:

Cermet Cement:

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

Manufactured:

• Sinter compressed pellets made from fine metal powder and glass ionomers powder at 800oC
• Ground it into fine form
  ↓
• Addition of titanium dioxide

Advantages:

• Better abrasion resistance
• Higher flexure strength.

Disadvantages

• Poor aesthetics

Question 5. Resin-modified glass ionomer.

Answer:

Resin-modified glass ionomer:

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

Composition:

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

Advantages:

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

Disadvantages:

• Polymerization shrinkage
• Limited depth of cure.

Question 6. Type 2 GIC.

Answer:

• It is restorative glass ionomer cement
• It is further divided into

Type 2 – 1 – Restorative Esthetic:

• Used for esthetic purposes
• For classes 3, 5
• Tunnel Restoration
• The powder/liquid ratio is 3:1 or greater
• They can either be authored or resin-modified
• Has superior physical properties
• Good translucency

Type 2-2 – Restorative Reinforced Gic:

• These have metallic inclusion
• Have superior strength
• Lack esthetics

Uses:

• Core build-up
• Root caries
• Tunnel restorations
• Deciduous restorations
• Powder/liquid ratio – 3:1 or greater

Question 7. Advantages and disadvantages of Glass Ionomer cement.

Answer:

Advantages:

• Chemical bonding to tooth structure
• Bio-compatible
• Good marginal seal
• Anticarcinogenic
• Translucent
• Conservative
• Less technique sensitive

Disadvantages:

• Low fracture resistance
• Low wear resistance
• Opaque
• Require moisture control

Glass Ionomer Cement Short Answers

Question 1. Tunnel Preparation.

Answer:

Tunnel Preparation:

• Isolate the tooth
• Place wedge below proximal portion
• Penetrate occlusal surface – 2mm inside marginal ridge at 45° angulation
• Removal of caries
• Widen the preparation
• Placement of band
• Placement of restorative material and its condensation
• Removal of wedge and matrix
• Finishing and polishing

Question 2. Modifications of GIC.

Answer:

Modifications of GIC:

Fiber Reinforced Glasses:

• Alumina fibers, glass fiber, silica fiber, and carbon fiber added to cement
• Improves flexure strength
• Low abrasion resistance

Metal Reinforced GIC:

• A mixture of amalgam alloy to GIC powder
• Poor esthetics
• Poor abrasion resistance

Cermet Cement:

• Sintering metal and glass powders
• Improved abrasion resistance
• Higher flexural strength

Resin Modified Glass Ionomer:

• Incorporate the best properties of both glass ionomer Cement and composite resin
• Good adaptation
• Flouride release
• Improved aesthetics

Question 3. Composition of GIC.

Answer:

Composition of GIC:

Powder:

• Silica-41.9%
• Alumina-28.6%
• Aluminium fluoride-1.6%
• Calcium fluoride-15.7%
• Sodium fluoride- 9.3%
• Aluminum phosphate- 3.8%

Liquid:

• Polyacrylic acid with copolymers with itaconic acid, maleic acid, and tricarballylic acid
• Tartaric acid
• Water

Glass Ionomer Cement Viva Voce

1. Varnishes or sealers should not be used to coat dentin if GIC is to be used as a restorative material
2. GIC adhesion is achieved partly by mechanical adhesion and partly by chemical chelation
3. To increase mechanical strength, GIC used as restoration is mixed at a higher powder-liquid ratio
4. After 24 hours the pH of GIC is 5.3
5. To increase the pH of GIC, zinc oxide is incorporated into the powder
6. Glass ionomers bond best to enamel than dentin and cementum
7. GIC shows decreasing levels of fluoride release with time
8. Powder of GIC is referred to as “ion-leachable glass”

Cast Metal Restorations Important Notes

1. Pickling

• Pickling is the process of cleaning the gold casting with 50% warm HCl
• Used to remove surface oxides from casting
• It is not a routine procedure
• Used only when indicated

2. Casting defects

• Distortion
• Surface roughness and irregularities
• Discoloration
• Porosity
  • Solidification defects
  • Trapped gases
  • Residual air

3. Types of casting machines

• Centrifugal casting machine
  • Uses centrifugal force to accelerate the flow of molten metal into the mold space
• Air pressure casting machine
  • Compressed gas is used to force the molten alloy into the mold

4. Types of cast metal alloys

5. Types of die materials used

• Gypsum products
• Electroformed dies
• Epoxy resins
• Divestment

6. Properties of base metal alloys

• Low density
• Low percentage elongation
• High fusing temperature
• High hardness
• Tarnish and corrosion resistance

7. Retention forms in cast restorations

• Grooves
• Bevel
• Internal box
• External box
• Pins, slots, skirt, collar

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• Cusp capping
• Reciprocal retention

8. Onlay

• They are partly intracoronal and partly extra-coronal types of restoration
• It has cuspal protection
• It is mainly indicated when the width of the lesion exceeds one-third of the intercuspal distance
• Features of cavity preparation:
  • Capping of functional cusps
  • Cuspal reduction 1.5 mm
  • The bevel used is a hollow ground long bevel in the intracoronal portion and a counter bevel in the extra coronal portion
  • Table:
    • It is a transitional area between the intracoronal and extra-coronal portion
    • It should be flat
    • Relieved from opposing cusps by 1.5 mm
    • There should be 3 tables prepared for each cusp in different directions
    • It provides retention and resistance form
  • Shoeing of nonfunctional cusps
    • Provides retention and resistance form over the nonfunctional cusp

9. Composition of wax

10. Principles for correct spring

• Use of proper gauge of sprue
• Use of proper length of sprue
• Should be attached to the bulkiest portion of the wax pattern
• Attach it to the wax pattern with little heat to avoid distortion

11. Uses of casting ring liner

• Permits unrestricted expansion of the investment
• Acts as a cushion between rapidly cooling metal ring and the more slowly cooling investment during the casting and crystallization of gold

12. Objectives of burnout

• Complete removal of wax pattern
• Elimination of excess water from the investment
• Production of thermal expansion

Cast Metal Restorations Long Essays

Question 1. Classify casting defects describe mesioocclusal cavity preparation for gold inlay on a mandibular first molar.
(or)
Describe class 2 mesioocclusal cavity preparation for gold inlay on mandibular 1 molar tooth.

Answer:

Casting Defects:

• Distortion
• Surface roughness and irregularities
• Discoloration
• Porosity
  • Solidification defects
    • Localized shrinkage
    • Micro
  • Trapped gases
    • Pinhole
    • Gas inclusion
    • Subsurface
  • Residual air
    • Back pressure

Class 2 Inlay Cavity Preparation

1. Initial tooth preparation

Occlusal outline form:

• Anesthetize and isolate the tooth
• Penetrate the tooth with no.271 bur from the mesial surface
• Extend upto central fissure to uninvolved marginal ridge
• Maintain a uniform pulpal depth of 1.5mm
• Preserve distal marginal ridge
• Extend up to the smooth areas of the buccal and lingual slopes of the cusps of a tooth.

Proximal box preparation:

• Mesial ditch cut is given using the same bur
• Width of cut 0.8mm, 0.5 mm in dentin, and 0.3 mm in enamel
• Extend it faciolingually
• Extend gingivally
• Provide 0.5mm of clearance
• Break the contact using cuts over facial and lingual walls using No.271 bur

Resistance and Retention form:

• Flat pulpal floor
• Box-shaped preparation
• The extra thickness of gold
• Occlusal step
• Dovetail

2. Final preparation:

1. Removal of remaining caries, old restorative material

• Removal of soft caries and infected dentin with a spoon excavator

2. Pulp protection

• Use of pulp protective materials

3. Secondary resistance and retention forms

• Retention grooves were placed in the facial axial and in coaxial line angles using 169L carbide bur
• Bevels
• Gingival bevel 45° to the preparation
• Include one-half the width of the gingival wall
• Occlusal bevel At occlusal 1/3rd of adjacent occlusal wall
• Removes unsupported enamel

4. Inspecting, Cleaning, and Rinsing

• Clean the prepared tooth with air/water spray
• Dry it with a cotton pellet
• Inspect the angles and margins

Question 3. Define Inlay Describe the Indications, Contraindications, advantages, and disadvantages of cast gold restoration.
Answer:

Definition Of Inlay:

• An inlay is an indirect intracoronal restoration which is fabricated extra orally and cemented in the prepared tooth

Indications:

• Extensive proximal caries
• Patients with good oral hygiene and low caries index
• Postendodontic restoration
• Teeth with extensive restoration
• To maintain proper tooth contact and contour
• Presence of cast metal restoration
• Abutment teeth
• Teeth with heavy occlusal forces and attrition

Contraindications:

• Aesthetic consideration
• Patients with high caries index
• Young patients
• Periodontally weak teeth
• Extensive caries involving facial and lingual and multiple surfaces
• Low economic status
• Presence of dissimilar restoration
• Extensive occlusal wear facets

Advantages:

• Better reproduction of details
• Better wear resistant
• Biocompatible
• Strengthens remaining tooth structure
• Fewer chances of voids
• Easy to polish
• Less chair time

Disadvantages:

• Need of temporary restoration
• Expensive
• Technique sensitive
• Difficult to repair
• Weak tooth bonding
• Unesthetic

Question 4.  Give the difference in cavity preparation between amalgam and gold inlay.

Answer:

Differences in cavity preparation between amalgam and gold inlay:

Question 5 Define retention form. How it is achieved in cast restoration.

Answer:

Retention Form:

• It is that form of cavity that resists the displacement of restoration from tipping and lifting forces

Retention In Cast Restorations:

1. Grooves:

Resist lateral displacement of restoration

• Internal grooves
  • Indicated in a shallow and small cavity
  • Contraindicated in a deep cavity
• External grooves
  • Indicated in extra coronal preparation
  • Prevents dislocation
  • May be prepared in stepped form

2. Reverse Bevel:

• Indication Class 1, 2, 3 restoration
• Presence of sufficient gingival floor
• Placed over the gingival floor with an incline gingivally and axially

3. Internal Box:

• Indicated in the presence of sufficient dentin
• Contraindicated in class IV and V preparation
• Have vertical walls prepared in dentin
• Increases retention
• It should be 2 mm in dimension

4. External box:

• Box with an opening to the axial surface of the tooth
• The peripheral portion can be flared/beveled

5. Pins:

• Types of pins used Cemented, threaded, parallel, cast, and wrought

6. Slot:

• Indicated in the shallow cavity, restricted occlusal anatomy
• Have a depth of 23mm

7. Skirt:

• Indicated in missing wall

8. Collar:

• Depth 1.52mm, surface extension
• Indication Grossly carious teeth
• Short teeth

9. Cusp Capping:

• Provide sufficient height of cusp

10. Reciprocal Retention:

• Placement of retention made at every end of the preparation

Question 6. Discuss the causes of casting defects and their prevention.

Answer:

The causes of casting defects and their prevention:

• Casting defects can be prevented by following various steps systematically
• Types of casting defects along with their causes and prevention are as follows

Cast Metal Restorations Short Essays

Question 1. Bevel and flares.
or
Circumferential Tie.

Answer:

Circumferential Tie:

• It refers to the design of cavosurface margin of an inlay tooth preparation

Significance:

• The cavosurface margin is the weakest part of the restoration
• To strengthen it, it is designed by incorporating bevels and flares

1. Bevels:

• It is the inclination that one surface makes with another when not at right angles

Types:

• Partial Bevel
  • Involving less than 2/3rd of enamel
  • Use of type 1 casting alloys
• Short Bevel
  • Involves full thickness of enamel
  • Use of type 1 and 2 alloys
• Long Bevel
  • Involves full enamel and half dentin
  • Use in type 1, 2, and 2 alloys
• Full Bevel
  • Involves complete enamel and dentin
  • Hollow ground Bevel
  • Concave in shape
• Counter Bevel
  • In cases of cusp capping

1. Flares: They are concave/flat peripheral portions of the facial/lingual proximal walls

Question 2. Die materials.

Answer:

Die materials:

Properties:

• Compatible with impression materials
• Have smooth surface
• Have adequate strength
• Easy to fabricate
• Have contrasting color
• Reproduce accurate details

Materials:

Question 3. Direct Wax Pattern.

Answer:

Direct Wax Pattern:

• Prepared in the oral cavity
• Done using matrix band or without it

Technique:

Isolate the tooth
↓
Apply band and retainer
↓
Soften inlay wax
↓
Compress over the prepared tooth
↓
Hold it with finger pressure til it sets
↓
Burnish it
↓
Remove band and retainer
↓
Check for centric occlusion
↓
Check for high points
↓
Smoothen it
↓
Attach sprue former and reservoir
↓
Remove the wax pattern

Advantages:

• Fewer discrepancies
• Less laboratory work

Disadvantages:

• Require more skill
• Requires more chair side time

Question 4. Indirect Wax Pattern.

Answer:

Indirect Wax Pattern:

• Prepared outside the oral cavity
• Use of type 11 inlay wax

Steps:

Lubricate the die
↓
Adapt inlay wax over it
↓
Carve the wax
↓
Attach sprue former
↓
Remove the wax pattern

Advantages:

• Less chair time
• Finishing and polishing
• This can be done on a die

Disadvantages:

• More laboratory work
• Errors due to inadequate casting

Question 5. Sprue.

Answer:

Sprue:

• Provides a channel so that molten metal flows into mold space after the wax pattern has been eliminated.

Types:

• Wax
• Plastic
• Metal

Functions:

• Provides a channel for the flow of molten alloy
• Provides reservoir to compensate for shrinkage
• Provides a channel for wax elimination

Requirements:

• Diameter Greater than the thickest part of the wax pattern
• Attachment to the thickest part of the wax pattern
• Sprue length such that the end of the wax pattern is l/8th to l/4th inch away from the open end of the casting ring
• Direction 45 to the bulkiest portion of the wax
• ReservoirTo compensate shrinkage

Question 6. Casting machines.

Answer:

Casting machines:

Types:

1. Centrifugal Casting Machine:

• Cheapest
• Used for small casting
• Uses centrifugal force to accelerate the flow of mol¬ten metal into the mold space

Steps:

Heat the ring at 1200°F for 15 minutes
↓
Move the arm of casting machine 23 turns clockwise and
lock it
↓
Heat the gold alloy
↓
Place the ring in the casting machine
↓
Release the lock of the arm
↓
This forces molten gold into a mold
↓
Recover the ring from the casting machine and cool it
↓
Removes the casting and cleans it

2. Air pressure Casting machine:

• Compressed air/gases like carbon dioxide or nitrogen are used to force the molten alloy into the mold.

Question 7. CADCAM for Inlay.

Answer:

CADCAM for Inlay:

• CADCAM indicates Computer Aided Design Computer Aided Machine
• In it, the whole casting design is fabricated
• This design is fed up with the computer
• The whole design is scanned
• It is then fabricated into the final prosthesis
• The computer is connected to a machine that processes the prosthesis
• Thus, the machining process of the prosthesis according to the design fabricated by the computer

Question 8. Types of Cast Gold Alloys.

Answer:

Types of Cast Gold Alloys:

Type 1 Soft

• Used for fabrication of small inlays
• Low strength
• Easily burnished
• Gold content7583%

Type 2 Medium

• Used for fabrication of inlays and onlays subjected to moderate stresses
• Cannot be heat treated
• Gold content7075%

Type 3Hard

• Used for high-stresses
• High strength
• Can be heat-treated
• Gold content6570%

Type 4 Extra Hard:

• Used for crowns, bridges, and removable partial dentures
• Increased hardness
• Can be heat-treated
• Gold content 60%

Question 9. Indications and contraindications of Onlay

Answer:

Indications and contraindications of Onlay:

Only:

• It is a combination of intracoronal and extra-coronal cast restoration which covers one or more cusps

Indications:

• Extensive weakened tooth due to caries or large restoration
• As post-endodontic restoration
• Presence of other cast restorations in adjacent or opposing teeth
• When the mesiodistal diameter of the tooth needs to be extended
• To correct the occlusal plane
• As an abutment for RPD

Contraindications:

• Patients with high caries rate
• Young patients
• Short clinical crown height

Cast Metal Restorations Short Answers

Question 1. Reverse bevel.

Answer:

Reverse bevel:

• A reverse bevel is a bevel of generous width that is prepared on the facial margin of a reduced cusp with a flame-shaped, fine grit diamond instrument
• Its width should extend beyond any occlusal contact with opposing teeth
• It should be at an angle that results in a 30-degree marginal metal
• It should be wide enough so that the cave surface margin is beyond any contact with the opposing dentition

Question 2. Sprue former.

Answer:

Sprue former:

• A sprue former is made of wax, plastic, or metal
• Thickness is in proportion to the wax pattern

Functions

• To form a mount for the wax pattern
• To create a channel for the elimination of wax during burnout
• Forms channel for entry of metal which compensates for allo£ shrinkage during solidification

Question 3. Porosities in casting.

Answer:

Porosities in casting:

Types:

1. Caused by solidification shrinkage

• Localized shrinkage porosity
• Suck back porosity
• Microporosity

2. Caused by gas

• Pinhole porosity
• Gas inclusion
• Subsurface porosity

3. Caused by air entrapment:

• Back pressure porosity

Prevention

• Use of correct sprue thickness
• Correct placement of sprue
• Use of reservoir
• Use of adequate casting forces
• Use of porous investment and proper vents
• Place the pattern away from the end of the ring

Question 4. Inlay Taper.

Answer:

Inlay Taper:

• Ideally, a tooth preparation should have slight diverg¬ing walls from gingival to occlusal surface

Value:

• Optimal taper25° per wall
• For short longitudinal walls 2° taper
• For high longitudinal walls Increased but not more than 10°
• Preparation should never have one side with more taper than the other
• For shallow preparation Axis of the taper is parallel to the long axis of the tooth
• For class 5 Axis of the taper is perpendicular to the long axis of the tooth.

Question 5. Hot spot porosity.

Answer:

Hot spot porosity:

• It is localized shrinkage porosity
• Occurs due to shrinkage of molten alloy when alloy solidifies from a molten state
• Cause Sprue former directed at 90°
• Prevention Direct the sprue former at 45°

Question 6. Back pressure porosity.

Answer:

Back pressure porosity:

• This is caused by inadequate venting of the mold
• If the bulk of the investment is too great the escape of air becomes difficult causing increased pressure in the mold
• The gold will solidify before the mold is filled resulting in a porous casting with rounded short margins
• Avoided by
  • Using adequate casting forces
  • Use of investment of adequate porosity
  • Place the pattern not more than 68 mm from the end of the ring

Question 7. Subsurface porosity.

Answer:

Subsurface porosity:

• It is porosity caused by gas

Cause:

• Simultaneous nucleation of solid grains and gas bubbles

Prevention:

• Controlling the flow of molten alloy

Question 8. Electroformed dies.

Answer:

Electroformed dies:

Advantages:

• Dimensional accurate
• Hard, abrasion-resistant
• Imparts a smooth surface
• Cheap
• Better marginal definition
• Does not absorb oil or water
• Prevent cuspal wear

Disadvantages:

• Difficult to trim
• Silver bath health hazard
• Noncompatible with impression material
• Color contrast is not good
• or adaptation to wax
• The pattern tends to lift from margins

Question 9. Onlay.

Answer:

Only:

• It is a combination of intracoronal and extra-coronal cast restoration which covers one or more cusp

Tooth Preparation:

• Occlusal Outline form:
  • Isolate the tooth
  • Start preparation with 271 bur
  • Maintain a pulpal depth of 2 mm
  • Reduce the cusps
  • Occlusal divergence 3°-5°

Proximal Box Preparation:

• Extend the preparation both mesially and distally

Question 10. Inlay Wax.

Answer:

Inlay Wax:

Properties:

• Plasticity
• Solid below approximately 40°C

Types:

• Type 1
• Type 2

Composition:

• Paraffin wax- 40 60%
• Ceresin -10%
• Gum dammar- 1%
• Carnauba- 25%
• Coloring agents

Question 11. Localized shrinkage porosity

Answer:

Localized shrinkage porosity:

• Occurs when cooling is incorrect
• The sprue freezes before the rest of the casting
• It results in large irregular voids near the sprue casting interface

Prevention:

• Sprue former should be directed at 45 degrees
• Placement of reservoir

Cast Metal Restorations Viva Voce

1. Sprue former diameter is between 8018 gauge
2. Types of sprue former wax, metal, and resin
3. Occlusal bevel in inlay3045°
4. Gingival bevel in inlay 30°
5. The sprue is placed at a 45° angle to the wax pattern
6. Wax interocclusal records help check occlusal clearance
7. Binder present in investment provides strength
8. Casting ring liner helps in permitting the expansion of mold
9. Sprue should be positioned in the thickest portion of the wax pattern
10. There should be a minimum gap of 1/8 1/4th inch between the ends of the casting ring and wax pattern
11. Back pressure porosity is caused by the entrapped air in the mold that does not escape through the pores of the investment
12. Type 1 or type B wax is used for the direct technique of wax pattern construction
13. Type C is used for indirect technique

Isolation Operative Dentistry Important Notes

1. Components of rubber dam

• Rubber Dam Sheet
• Rubber dam clamp/ retainer
• Rubber dam frame
• Rubber dam punch
• Rubber dam retainer force
• Dental floss
• Template

Isolation Operative Dentistry Long Essays

Question 1. Enumerate various methods of Isolation. Describe in detail about rubber dam.

Answer:

Methods of Isolation:

• Direct method
  
  • Rubber dam Cotton rolls
  • Gauze piece Absorbent
  • wafers Suction devices
  • Gingival retraction cord
• Indirect Method
  • Local anesthesia Drugs
  • Anti sialogogues
  • Anti-anxiety
  • Muscle relaxants

Rubber Dam – By Dr. S.C. Barnum

Purpose:

• Control of moisture
• Retraction
• Protects soft tissues
• Improves quality of treatment

Contraindications:

• Asthmatic patients
• Allergy to latex
• Mouth breathers
• Extremely malpositioned tooth
• Third molar

Components:

1. Rubber Dam Sheet:

• Square sheets
• Size – 5″x 5” or 6″ x 6″

Thickness:

• Thin – 0.006″
• Medium – 0.008″
• Heavy -0.010″
• Extra heavy- 0.012″
• Special heavy – 0.014″

Color:

• Green/blue
• The dull side faces the operator

2. Rubber Dam Clamps/Retainers:

To secure the dam to the teeth

Parts:

• 2 jaws
• Bow – connecting jaws
• 4 prongs – 2 on each jaw

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• Rests on line angle

Types:

• Winged or wingless retainer
• Large, small, universal

3. Rubber Dam retainer forceps:

• Hold the retainer
• Facilitates its placement and removal

4. Rubber Dam frame:

• U shaped frame
• Types – metal or plastic
• Has minute projections on its outer surface to secure the dam

5. Rubber Dam punch:

• For making holes in the dam
• Depending on the applied tooth, the sizes of the holes vary

6. Rubber Dam Template:

• Used to transfer the markings to the sheet

7. Dental Floss:

• To prevent accidental aspiration of the clamp

 

 

Placement:

Comfortable position of the patient
↓
Selecting the appropriate clamp and sheet
↓
Punching a hole in the sheet
↓
Applying lubricant
↓
Holding clamp through forceps
↓
Placement of rubber dam

• The clamp is placed first and then the sheet is passed over it
• Placement of sheet and then securing it with clamp
• Both are placed together

Removal:

Removal of clamp
↓
Stretching of sheet
↓
Cut all interseptal rubbers
↓
Remove the remaining

Question 2. Discuss importance of isolation and various methodds used to achieve the same.

Answer:

Importance Of Isolation:

• Isolation helps for following

1. Moisture control

• It refers to excluding sulcular fluid, saliva, and gingival bleeding from the operating field

2. Retraction and access

• It provides maximal exposure of the operating site

3. Harm prevention

• Prevents harm to the patient during the operation
• Small instruments and restorative debris can be aspirated or swallowed
• Provides patient comfort and operator efficiency

Direct Method:

1. Cotton rolls:

• Moisture absorbent
• Provide minimal retraction

Types:

• Manual and prefabrication
• Stabilized by cotton roll holder

Site of placement:

• Maxillary anteriors – Either side of labial frenum
• Mandibular anterior
• Lingual sulcus
• On either side of labial frenum
• Maxillary posterior – Adjacent vestibules
• Mandibular posterior
• Buccally – vestibule
• Between tongue and teeth
• Moistened it before removal to avoid tearing off of gingiva

2. Gauze pieces:

• Size – 2″ x 2″

Uses:

• To isolate larger areas
• As throat screens

Advantages:

• Better tolerated
• More acceptable
• Less adhesion to dry tissues

3. Absorbent wafers:

• Made of cellulose
• Covers parotid ducts

4. Evacuators:

Type:

• High vacuum
• Low vacuum
• High vacuum
  • Removes debris from the working site
  • Removal of toxic material
  • Decreases treatment time
• Low volume [Saliva ejectors)
  • Used along with operative procedures

Types:

• Disposable plastic tips
• Autoclavable metallic tips

5. Gingival retraction cord:

• Inserted into gingival sulcus
• Retracts gingiva

Types:

• Braided and non-braided
• Plain and impregnated

Effects:

• Improved accessibility and visibility
• Protects gingival from abrasion
• Restricts placement of restoration into sulcus
• Everts gingival tissue

Indirect Method Of Isolation:

• It includes

1. Anaesthetic agents

2. Antisialogogues

• Chemical agent is administered orally 1-2 hours prior to the procedure

Effect:

• Causes temporary dry mouth by acting on sympathetic nervous system

Drug of choice:

• Atropine 0.1-1 mg

Contraindicated:

• Nursing mothers
• Patients with glaucoma

Advantage:

• Useful in hypersalivation

Disadvantages:

• Tachycardia
• Dilatation of pupils
• Urinary retention
• Sweat glands inhibition.

Isolation Operative Dentistry Short Essays

Question 1. Gingival Retraction/ Gingival tissue management.

Answer:

Gingival Retraction:

Methods:

1. Physicomechanical:

• Rubber dam
  • Heavy, extra heavy, and special heavy sheets provide adequate mechanical displacement of gingival tissue
• Wooden wedges – Used interdentally
• Gingival retraction cords
  • Displaces gingival laterally and apically

Placement:

• Anesthetize the area
• Select appropriate cord
• Pack the cord with cord tucking instrument, around the tooth
• Place it for 5 minutes
• Remove the cord after moistening it to avoid gingival abrasion
  • Rolled cotton twills
    • Laterally displaces gingival
    • Combined with ZOE

2. Chemical means:

Chemical used:

• Trichloroacetic acid
• Sulfuric acid

Advantage:

• Hemostatic

Disadvantage:

• Caustic
• Irritant

3. Chemico mechanical method:

Chemical used:

• Vasoconstrictors – Epinephrine
• Astringents – Tannic acid
• Tissue coagulant – Silver nitrate

4. Rotary curettage (Gingettage):

• Removes a minimal amount of gingival epithelium with the help of a high-speed handpiece and bur.

5. Electrosurgical method:

• Alternating electric current energy is used at a high frequency

Actions:

• Cutting
• Coagulation
• Fulguration
• Desiccation

Question 2. Advantages of Rubber Dam.

Answer:

Advantages of Rubber Dam:

• Maximizes access and visibility
• Protection of soft tissues
• Provides clean and dry field
• Avoids contamination
• Prevents aspiration of foreign bodies
• Improves efficiency
• Improves properties of dental material
• Protection of patient and dentist

Isolation Operative Dentistry Short Answers

Question 1. Gingival retraction cord.

Answer:

Gingival retraction cord:

• Inserted into the gingival sulcus
• Retracts gingiva

Types:

• Braided and non-braided
• Plain and impregnated

Effects:

• Improved accessibility and visibility
• Protects gingival from abrasion
• Restricts placement of restoration into the sulcus
• Everts gingival tissue

Question 2. Affected and infected Dentin.

Answer:

Affected and infected Dentin:

1. Infected Dentin

• Irreversible denatured collagen
• Infiltrated with bacteria
• Notremineralizable
• Should be removed
• Darker
• Softer
• Lacks sensation
• Indistinct cross bands
• Stained with:
  • 0. 2% propylene glycol
  • 10% acid red solution
  • 0. 5% basic Fuschia

2. Affected Dentin

• Reversible denatured collagen
• Not infiltrated
• Remineralize
• Left behind while the cavity
• preparation
• Lighter
• Harder
• It is sensitive
• Distinct cross bands
• Cannot be stained with any solution

Isolation Operative Dentistry Viva Voce

1. Thinner rubber dam can pass through contacts easily
2. A thicker rubber dam is more effective in retracting tissues and more resistant to tearing
3. The jaws of the retainer should not extend beyond the mesial and distal line angles of the tooth
4. The bow of the retainer should be tied with dental floss
5. The tip of the saliva ejector must be smooth and of non-irritating material
6. Gingival cord placement should not harm gingival tissue
7. Atropine used for isolation is contraindicated in nursing mothers and patients with glaucoma

Direct Filling Gold Short Essays

Question 1. DFG (Direct Filling Gold).
Answer:

DFG (Direct Filling Gold):

Definition:

• Direct gold is a gold restorative material that is manufactured for compaction directly into prepared cavities

Indications:

• Class 1 cavities Small carious lesions in pit and fissures of posterior teeth
• Class 5 carious lesions
• Class 3 cavities proximal surfaces of anterior teeth
• Class 2 restoration of small cavitated proximal surfaces of posterior teeth
• Class 6 Incisal edges or cusp tips
• A defective margin of cast metal restoration

Contraindications:

• Very large pulp chambers
• Severely periodontally weakened teeth with questionable prognosis
• In handicapped patients
• Root canal-filled teeth

Classification:

1. Foil:

• Sheet
  • Cohesive
  • Noncohesive
• Ropes
• Cylinders
• Laminated foil
• Platinized foil

2. Electrolytic precipitate:

• Mat gold
• Mat foil
• Gold calcium alloy

Question 2. Types of gold.

Answer:

Types of gold:

1. Gold Foil Oldest form:

Types:

1. Sheets size 10 x 10 cm

• Thickness 1.5 micron
• No.3 weighs 3 gm
• Too large for use in preparation

2. Gold foil cylinder

• Uses noncohesive gold
• Uses % and 1/8 of a sheet of gold

3. Gold pellets

• Are annealed before the formation
• Stored in a gold foil box along with a cotton dipped in 18% ammonia

4. Platinized gold foil

• Platinum content in foil is 15%
• Increased hardness

Read And Learn More: Operative Dentistry Short And Long Essay Question And Answers

• Used for restoration of cusp tips and incisal edges

5. Corrugated gold foil.

• Paper placed between foil gets burnt and charred

4. Laminated gold foil:

• More resistant to applied forces

2. Crystalline Gold

1. Mat gold

• Electrolytically precipitated type
• Used for building up of internal restoration

2. Mat foil

• No need to veneer the restoration

3. Electralloy

Increased hardness and strength of gold by adding minute quantities as Calcium

Improved handling properties

4. Powdered Gold

• Size 15 microns
• Difficult to handle
• Does not require very sharp line angles and point angles.

Question 3. Mat Gold.

Answer:

• Electrolytically precipitated

Preparation:

• Sinter pure gold in the oven
• Heat slightly below its melting point

Result:

• Spongy, loosely arranged crystalline structure
  • Available in form of strips
  • Can be used plain/sandwiched in gold foil
• Use: Building up of internal restoration
• Advantage: Easily compacted
• Adapted well

Question 4. Condensation of DFG.

Answer:

Condensation of DFG:

Aims:

• Formation of cohesive mass
• Adaptation to the preparation margins
• Prevent voids formation
• Increases strength and hardness of restoration

Technique:

• Place the gold piece in the corner of the preparation
• Start malleting in the center of the mass
• Condense at 45o to walls and floor for maximum adaptation
• Next condense at 90° to the previous layer to prevent displacement of already condensed pieces
• Each time the condenser should overlap the half of previous step for reducing voids formation
• This is called stepping

Question 5. Annealing/Degassing.

Answer:

Annealing:

• It involves the removal of the volatile protective coating present on a pure gold surface
• Used for noncohesive gold, as a layer of ammonia is present over it to prevent the formation of the oxide layer and contaminate gold

Methods:

1. Using alcohol Flame:

• Bulk method:
  • Place mass of gold in mica tray and heat over flame up to 650700°C
  • Less time required
  • Risk of overheating
• In the piece method;
  • Hold small pieces over a blue flame of alcohol and heat until the gold becomes dull red
  • Less wastage
  • Time consuming

2. Electric Annealer:

• Gold is heated for 10 minutes at 850°F
• Then cooled for placing in the prepared tooth

Direct Filling Gold Short Answers

Question 1. Preparation of Pure gold foil.

Answer:

Preparation of Pure gold foil:

• Gold foil are cut into sheets
• These sheets are separated by papers
• These are heated together
• 20 such papers are consist in the book
• These sheets are cut into different sizes and are available in different weight

Question 2. Properties of DFG (Direct Filling Gold)

Answer:

Properties of DFG (Direct Filling Gold):

• It is soft, malleable, and ductile
• It does not get oxidized
• It is yellowish, metallic in color
• It get fuses at 1063oC and boils at 2200oC
• The density of gold is 1919.3 g/cm2
• Its hardness is 25 BHN
• Its coefficient of thermal expansion is 14.4 x 106/oC which is more than that of a tooth
• It is the noblest of all metals
• It has high thermal conductivity
• It can be cold welded
• It results in good marginal integrity

Question 3. Electrically.

Answer:

Electrically:

• The newest form of DFG

Preparation:

• Electrolyte it along with the addition of minute quantities of calcium
• The resultant crystalline structure is sandwiched between two gold foils

Advantages:

• Improved handling properties
• Produces the hardest surface
• Increased strength and hardness

Question 4. Gold Foil.

Answer:

Gold Foil:

Types:

1. Sheets size 10 x 10 cm

• Thickness 1.5 micron
• No.3 weighs 3 gm
• Too large for use in preparation

2. Gold foil cylinder

• Uses noncohesive gold
• Uses % and 1/8 of a sheet of gold

3. Gold pellets

• Are annealed before the formation
• Stored in a gold foil box along with a cotton dipped in 18% ammonia

4. Platinized gold foil

• Platinum content in foil is 15%
• Increased hardness
• Used for restoration of cusp tips and incisal edges

5. Corrugated gold foil

• Paper placed between foil gets burnt and charred

6. Laminated gold foil

• More resistant to applied forces

Direct Filling Gold Viva Voce

1. All types of DFG except non corrosive gold require degassing before use
2. Underheating fails to render the gold surface pure
3. Overheating makes the gold more brittle
4. Poor resistance form can result in tooth fracture
5. Improper retention form results in loose restoration
6. Forces of condensation should be at 45° to the cavity walls and floors
7. Forces of condensation must be at 90° to previously condensed gold

Pin Retained Restoration Important Notes

1. Types of pin-retained restorations

2.  Failures of pin retained restorations

• If the failure is within the restoration, the restoration can fracture
• If the failure is at the interface between the pin and the restorative material, the pin can pull out the restorative material
• If the failure is within the pin, the pin can fracture when stressed beyond its ultimate tensile strength
• If the failure is at the interface between the pin and the dentin the pin can pull out the dentin
• Within the dentin, the dentin can fracture

Pin Retained Restoration Short Essays

Question 1. Pin retained restoration.

Answer:

Pin retained restoration:

Definition:

Any restoration that requires the placement of pin/pins in the dentin to provide sufficient retention and resistance from the restoration

Advantages:

• Conserves tooth structure
• Increases resistance and retention
• Economic
• Requires fewer recall visits

Disadvantages:

• Dentin fracture
• Decreased strength of amalgam
• Perforation
• Microleakage

Indications:

• Grossly carious teeth
• Full coverage restoration
• Extended preparation

Contraindications:

• Occlusal problems
• Aesthetic problems

Pins:

• Types- Cemented pin
• Self threaded
• Friction locked pin

Sizes:

• Minuta-0.015″
• Minikin – 0.019″

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• Minim – 0.024”
• Regular-0.031″

Design:

• Standard
• Self shearing
• Two in one
• Link series
• Link plus series

Question 2. Self-threaded pin./Self-threading pin.

Answer:

Self-threaded pin:

• Introduced by Going in 1966
• Size – 0.0015″ – 0.004” larger than pin holes
• Retention – By threads of pins
• The material used – Stainless steel, Titanium

Indications:

• Vital teeth
• Presence of sufficient dentin

Advantages:

• Ease of retention
• Superior retention
• No need for cement media

Disadvantages:

• Pulpal stress
• Dentinal crazing
• Microleakage
• Loosening of pins

Question 3. TMS (Thread mate System).

Answer:

TMS (Thread mate System):

Advantages:

• Variety of design
• Variety of pin sizes
• Good retention
• Color coding
• Gold plated
• Reduced corrosion

Pin Sizes

• Minute-0.015″
• Minikin – 0.019″
• Minim – 0.024”
• Regular-0.031″

Pin Design:

• Standard – 7 mm long, flat head
• Self-shearing – On reaching the bottom of the pinhole, the head separates automatically
• Two in one
• Two pins join each other at a joint
• When the peripheral pin shears off the other pin can be reused for another pin channels
• Link series
• Latch head
• Self shearing type
• Link plus series
  • Sharp threads
  • Tapered tip
  • Shoulder stop

Pin Retained Restoration Short Answers

Question 1. Self-shearing pins.
(or)
Pins in restorative dentistry.
(or)
Types of pins in amalgam restoration.

Answer:

Pins in restorative dentistry:

1. Direct Pins:

2. Indirect Pins:

• Smaller than pin holes
  • Cast gold pins
  • Wrought precious metal pins

Pin Retained Restoration Viva Voce

1. The self-threaded pin is the most retentive
2. Cemented pins are the least retentive pins
3. Pulpal stress is maximal with self-threading pin and least with cemented pin
4. Threaded Mate System (TMS} is the most widely used self-threading pins
5. TMS pins exhibit less microleakage than other pins

Amalgam Important Notes

1. Types of corrosion

2. Creep values

3. Mercury toxicity

• The maximum level of occupational exposure considered safe is 50 pg of mercury/m3 of air
• Mercury vapors may be released from the Ag-Hg phase which is melted during the polishing and amalgam removal process
• Rubber dam, high volume evacuation, and water cooling unit are used during the removal of amalgam
• Masks can’t filter mercury vapors
• Mercury toxicity results in acrodynia or Pink’s disease
• It is characterized by pinkish discoloration of the skin, profuse salivation, ulceration of the mucosa, and premature shedding of teeth
• Mercury has an average half-life of 55 days for transport through the body to the point of excretion
• Spent capsules and mercury-contaminated cotton rolls or napkins should be stored in tightly capped pressure containers

4. Forms of mercury

• Elemental mercury – vapor is inhaled and absorbed through the lungs at 80% efficiency
• Inorganic mercury – exists mainly as sulfide and is absorbed easily by GIT

Read And Learn More: Operative Dentistry Short And Long Essay Question And Answers

• Organic mercury in the form of methylmercury mercury – mainly carried through food

5. Failures of amalgam restorations

• Bulk fractures of restorations
• Corrosion
• Excessive marginal fractures
• Sensitivity or pain
• Secondary caries
• Fracture of tooth structure

Amalgam Long Essays

Question 1. Classify silver alloys. Give the role of each ingredient of silver alloy. Add a note on zinc al¬loys
(or)
Classify amalgam alloys, write the role of each ingredient, and add a note on gamma 2 phase

Answer:

Amalgam:

Dental amalgam is an alloy of mercury, silver, copper, and tin which may also contain palladium, zinc, and other elements to improve handling characteristics and clinical performance

Classification:

1. Based on copper content

• Low copper alloys- contain less than 6% copper
• High copper alloys- contain between 13-30% cop-per

2. Based on zinc content

• Zinc containing alloys
• Zinc free alloys

3. Based on the shape of the alloy particle

• Lathe cut alloys
• Spherical alloys

4. Based on the number of alloyed metals

• Binary alloys
• Tertiary alloys
• Quaternary alloys

5. Based on the size of the alloy

• Microcut
• Macrocut

Composition:

Mercury:

• It is added to the alloy

Platinum:

• Hardens the alloy
• Increases resistance to corrosion

Palladium:

• Hardens and whitens the alloy

Indium:

• Reduces mercury vapor and improves wetting

Zinc Free Alloys:

• Contains less than 0.01% zinc
• It avoids the delayed expansion of the amalgam which occurs in zinc-containing alloys
• This results in the prevention of dimensional change in the restoration
• Prevents micro-leakage and secondary caries formation

Gamma 2 Phase:

• Gamma 2 phase is Sn and Hg (Sn8Hg)
• Weakest component
• Hardness is 10% that of Gammal
• Least stable in a corrosive environment;

Question 2. Discuss in detail the manipulation of silver amalgam. Add a note on high copper amalgam.

Answer:

Manipulation Of Amalgam

1. Selection of materials:

• Alloy selection:
  • For restorative purposes- high resistance amalgam is selected
  • For strength- High copper alloys are selected
  • If moisture control is difficult- non-zinc-containing alloys are selected
• Mercury-.attoy ratio:
  • To achieve smooth and plastic amalgam an amount of mercury in excess is desirable
  • But because of the harmful effects of excess mercury, it is necessary to reduce the amount of mercury
  • One of the methods for it is to reduce the original mercury/alloy ratio
  • This is called the Eames technique
  • Sufficient mercury must be present in the mix and it should be as low enough so that mercury content is acceptable during condensation
  • Ratio is 1:1

2. Trituration:

• Objective:
  • To wet all the surfaces of the alloy particles with mercury
  • The film should be rubbed off to obtain a clean surface of alloy for mercury
• Manual mixing:
  • A glass mortar with a roughened inner surface and a pestle with a round end is used for mixing
  • It depends on
    • Number of rotations
    • Speed of rotations
    • Pressure placed on pestle
    • Mechanical mixing

Alloy and mercury are dispensed into the capsule
↓
The capsule is secured in the machine
↓
The machine is turned on
↓
The automatic timer is set
↓
Trituration is accompalished

3. Mulling:

• It is continuation of trituration
• It causes the mix to cohere so that it can be readily removed from the capsule
• Achieved by vigorously rubbing between first finger and thumb for 2-5 sec

4. Condensation:

• Amalgam is placed in a prepared cavity and condensed using suitable condensers
• Aims
  • To compact alloy into a prepared cavity
  • To remove any excess mercury in each increment
  • Reduces voids

5. Carving and finishing:

• Carved to reproduce proper tooth anatomy
• Smoothen through burnishing with a ball bur¬nisher
• Final smoothening can be achieved by rubbing with a moist cotton pellet
• Polishing minimizes corrosion and prevents adherence to plaque
• It is delayed for 24 hours
• Wet polishing is desirable

High Copper Alloys:

• Contains 13-30%, weight copper
• They are preferred because of
  • Improved properties
  • Resistance to corrosion
  • Better marginal integrity
  • Improved performance in clinical trials

Types:

1. Admixed alloys

• Regular type
• Unicomposition alloy

2. Single-composition alloy

Composition

Setting Reaction:

1. Admixed alloy:

Components are mixed
↓
Mercury begins to dissolve the outer portion
of the particle
↓
Silver enters mercury and forms the yx phase
↓
Tin dissolved in mercury reacts with copper
and forms Cu₆ Sn₈

2. Single composition:

Each particle contains Ag3 Sn, AgSn, and Cu3 Sn
↓
Silver and tin dissolve in mercury form the Yj phase
↓
Later a layer of Cu6 Sn8 is formed at the surface of the alloy
particles

Advantages:

• Sets fasts
• Low residual mercury
• Faster finishing
• High strength
• Low condensation pressure

Disadvantages:

• Less working time
• Condensation pressure is not sufficient

Question 3. Define class 2 cavity and enumerate various retention, resistance, and convenience forms in class 2 restoration.
(or)
Define retention form. discuss various methods of retention form in cavity preparation

Answer:

Class 2 Cavity:

• Preparation involving the proximal surface of posterior teeth is termed class 2

Retention

1. Primary retention form:

• It is the shape or form of the conventional prepara¬tion that prevents displacement or removal of the restoration by tipping or lifting forces for non-bonded restorations
  • Primary retention form for amalgam restora¬tion
    • Occlusal convergence is provided
  • Primary retention form for composite restora¬tion
    • Composite restorations are retained by micro¬mechanical bond
    • Bonding is increased by bevel and flare in enamel
  • Primary retention form for cast metal restoration
• Obtained by
  • Parallel vertical walls
  • The small angle of divergence
  • Occlusal dovetail

2. Secondary retention forms:

• Grooves and coves
  • At axiofacial and axiolingual line angles
  • For cast restoration
• Slots
  • In occlusal box, buccoaxial, linguoaxial and gin-gival walls
  • For amalgam and cast restoration
• Locks
  • In the proximal/occlusal box
  • For amalgam
• Pins – For amalgam, composite, and cast restoration
• Skirts
  • On all four sides of the preparation
  • For cast restoration
  • Amalgampins – For amalgam restoration

Resistance Form:

• It may be defined as the shape and placement of the preparation walls that best enable the remaining tooth structure and the restoration to withstand, without fracture, masticatory forces delivered principally along the long axis of the tooth

Features:

• Relatively horizontal floors
• Box-like shape
• Inclusion of weakened tooth structure
• Prevention of cusps and marginal ridges
• Rounded internal line angles
• The adequate thickness of restorative material
• Reduction of cusps for capping, when indicated

Convenience Form:

• It is the shape or form of the preparation that provides for adequate observation, accessibility, and ease of op¬eration in preparing and restoring the tooth
• It is obtained by
  • Occlusal divergence of vertical walls
  • Extending proximal preparation beyond proximal contacts.

Question 4. Discuss tooth preparation of maxillary first mo¬lar for class 2 mesioocclusal amalgam restoration.

Answer:

Tooth preparation of maxillary first mo¬lar for class 2 mesioocclusal amalgam restora¬tion:

Steps

1. Outline form:

• It means placing the preparation margins in the positions they will occupy in the final preparation except for finishing enamel walls and margins
• Using high-speed bur with air-water spray enter the pit on the occlusal surface area to the mesial surface
• Maintain an initial depth of 1.5-2 mm
• Extend upto central fissure
• Maintain uniformity of pulpal floor
• Enameloplasty is done if required
• Maintain width of the cavity to l/4th of the intercuspal distance
• Occlusal convergence is made
• Widen preparation faciolingually
• Proximal cutting upto 0.5-0.6 mm depth
• Make cavosurface angle of 90°
• Ideal clearance 0.3-0.5mm
• Preservation of marginal ridge
• The reverse curve in the case of broader contacts

2. Primary resistance form:

• It may be defined as the shape and placement of the preparation walls that best enable the remaining tooth structure and the restoration to with¬stand, without fracture, masticatory forces delivered principally along the long axis of the tooth

Features:

• Box-shaped preparation
• Flat pulpal floor
• Inclusion of all weakened structure
• Cavosurface angle of 90o
• Rounded internal line and point angles
• Cusp. Capping
• Minimal width of preparation

3, Primary retention form:

• It is the shape or form of the conventional preparation that prevents displacement or removal of the restoration by tipping or lifting forces for non-bonded restorations
• It is achieved by
  • Occlusal convergence
  • Dovetail

4. Convenience form:

• It is the form and shape of the cavity that enables ease of accessibility, visibility, and ease of operation.

5. Final Tooth Preparation:

• Inspect the preparation
• Removal of debris, old restorative material
• Removal of soft caries with a spoon excavator

6. Secondary retention and resistance form:

• Retention grooves and locks in the proximal box
• Slots in the gingival floor

7. Pulp Protection:

• Use of pulp protective materials.

8. Finishing of External walls:

• Removal of all unsupported enamel
• Bevelling of the enamel of the gingival wall with GMT

Question 5. Principles of cavity preparation and describe secondary retention form in class 2 for amalgam restoration.

Answer:

Principles Of Cavity Preparation:

1. Initial Steps:

1. Outline form:

• Placing the preparation margins to the place they will occupy in the final tooth preparation

Factors:

• Extension of all carious lesions
• Caries index
• Old restorative material
• Initial depth 0.2-0.8 mm
• Esthetics

Features:

• Preserve cuspal strength
• Preserve marginal ridge
• Minimize extension
• Maintain initial depth to 0.2-0.8 mm
• Enameloplasty wherever required

2. Primary Resistance Form:

• “It is that shape and form of the cavity which enables both tooth and restoration to withstand without fracture the stresses of masticatory forces delivered principally along the long axis of the tooth”

Features:

• Box-shaped preparation
• Flat pulpal floor
• The adequate thickness of restorative material
• Preservation of marginal ridge
• Inclusion of weakened tooth structure
• Rounded internal line angles
• Cusp capping

3. Primary Retention Form:

• It is the form and shape of the cavity that resists the displacement of restoration from lifting and tipping forces

Features:

• Occlusal convergence
• Dovetail

4. Convenience Form:

• It is the form and shape of the cavity that enables ease of accessibility, visibility, and ease of operation

Features:

• Adequate extension
• Cavosurface margin
• Proximal clearance

Question 6. Discuss causes of failure of amalgam restora¬tion and how you manage them clinically.

Answer:

1. Poor case selection:

• Teeth with extensive caries
• Presence of para-functional habits
• Heavy masticatory form

Management:

• Proper case selection should be done
• Patient’s esthetic concerns, economic status, medical condition, and age should be taken into consideration
• Patients at high risk for dental caries may require an initial treatment plan to limit disease progression until caries risk factors are reduced or eliminated

2. Defective tooth preparation:

• Inadequate occlusal extension
  • Increased risk of secondary caries
• Under the extension of the proximal box
  • Not upto embrasure
  • Interferes with self-cleaning action
• Over-extended tooth preparation
  • Tooth fracture
  • Need of cusp, capping
• Depth of preparation
  • Shallow cavity – Inadequate thickness of restorative material
  • Deep cavity – Pulpal damage

Management:

• Minimal occlusal thickness for resistance to fracture should be 1.5 mm
• Restrict the buccolingual extension of the external walls to allow strong cusp and ridge areas to remain with sufficient dentin support
• In case of extensive tooth preparation, cusp cap-ping is done
• A pulpal depth of approximately 1.5-2 mm and usually a maximum depth into the dentin of 0.2 mm is maintained

3. Defective amalgam manipulation:

• Incorrect mercury alloy ratio
  • More the mercury, the less the strength
• Trituration
  • Overtriturated – shiny wet and soft
  • Under triturated – dry mix
• Improper condensation
• Faulty finishing and polishing
  • Excessive heat production during polishing causes pulpal trauma
  • Heavy pressure during polishing -overhangs

Management:

• Use proper mercury: alloy ratio as 1:1
• Use of proper triturated amalgam
• Amalgam should be adapted to all the walls
• Condensation done in small increments
• Use of coolant along with finishing and polishing of restoration

4. Defective matrix adaptation:

Management:

• The matrix should be properly contoured
• Use of wedge
• Stabilization of wedge
• Avoid premature removal of matrix band to prevent fracture of restoration

5. Post-operative failures:

• Postoperative pain – due to
  • High points
  • Zinc containing alloys
  • Dissimilar restoration
  • Thermal changes

Management:

• Use of zinc-free alloys to prevent delayed expansion
• Occlusal correction to reduce high points
• Avoid the use of dissimilar restoration to prevent galvanism

Amalgam Short Essays

Question 1. Control of pain during cavity preparation.

Answer:

• The administration of local anesthesia to all tissues in the operating site is recommended in certain patients to eliminate pain and reduce salivation associated with tooth preparation and restoration

Factors Affecting It

1. Patient factors:

• Cardiovascular system
  • Before administration of a drug, the condition of the cardiovascular system must be assessed
• Central nervous and respiratory systems
  • The central nervous system is affected by an overdose of injected anesthetic drugs
• Allergy
  • It is an absolute contraindication for administration of local anesthetic

Advantages:

• Patient cooperation
• Salivation control
• Hemostasis
• Operator efficiency

Technique:

• Before needle entry, the mucosa at the injection site should be wiped free of debris and saliva with sterile gauze
• After this, a lidocaine topical anesthetic ointment is applied for a minimum of 1-2 minutes to the selected entry site
• Lidocaine 2% with 1:100,000 epinephrine is commonly used in operative dentistry
• 1 ml provides infiltration anesthesia for 40-60 minutes for anterior teeth
• Painless injection is achieved by a combination of the following
  • Use of topical anesthetic
  • Use of sharp needle
  • Slow deposition rate

Question 2. Mercuroscopic expansion.

Answer:

Mercuroscopic expansion:

• Mercuroscopic expansion is proposed by Jorgensen
• It occurs due to electrochemical corrosion
• During this corrosion mercury from tin-mercury reacts with silver-tin particles and produces expansion
• Corrosion is due to the oxidation of the tin-mercury phase of amalgam leading to the formation of oxides and oxychlorides in tin
• The oxide precipitates as crystals and tends to fill up the spaces occupied by the original tin-mercury phase
• It can occur anywhere on or within a set amalgam
• This leads to extrusion at margins which has a greater prevalence of marginal fracture associated with occlusal amalgam
• Such expansion is known as macroscopic expansion

Question 3. Burnishing.

Answer:

Burnishing:

• Done after condensation
• To make the surface shiny
• Amalgam is overfilled and burnished immediately

Types:

1. Pre-carve burnishing

• Reduce mercuric content
• Creates gross anatomy
• Done with a large burnisher

2. Post-carve burnishing

• Done after completion of the carving
• Done with a small-size burnisher
• To remove traces of carving

Question 4. Trituration and condensation of Amalgam.

Answer:

Trituration and condensation of Amalgam:

Trituration:

It is the process of removal of the oxide layer from the alloy particles to coat each particle with mercury, resulting in a homogenous mass

Method:

1. Manual
2. Mechanical

Objectives:

• Result in workable mass
• Removal of the oxide layer
• Dissolution of alloy into mercury
• Reduces y1 and y2

Types:

• Normal – Homogenous mass
• Overtriturated – warm, shiny wet, and soft
• Under triturated – Dry, weak

Condensation:

• Types of Condensers
  • Triangular
  • Round
  • Elliptical
  • Trapezoidal
  • Rectangular
• Rules:
  • Done in increments
  • Condense laterally and apically
  • Have a constant supply of amalgam
  • Apply adequate force
  • Depends on the type of alloy
    • Lathe cut alloy – Small condenser
    • Blended alloy-Small condenser
    • Spherical alloy-Large condenser

Question 5. Various cavity designs for Class 2.

Answer:

Various cavity designs for Class 2:

Question 6. Tarnish and Corrosion.

Answer:

Tarnish and Corrosion:

Question 7. Finishing and Polishing of Amalgam.

Answer:

Finishing and Polishing of Amalgam:

• Involves the removal of marginal irregularities, obtaining proper contours, and smoothening the restoration
• Polishing creates a smooth, shiny luster on the surface of the amalgam

Time:

• After 24 hours of restoration
• Premature – Interferes with a crystalline structure

Advantages:

• Marginal adaptation
• Reduce tarnish and corrosion
• Plaque resistance
• Prevent recurrent caries
• Prevent occlusal problems
• Maintain periodontal health

Steps:

• Evaluate marginal integrity by explorer
• Evaluate occlusal pattern
• Smoother margins by round bur
• Eliminate scratches by large round finishing bur
• Smoothen occlusal surface by side of burs
• Smoothen margins by finishing the strip
• Smoothen facial and lingual surfaces with a finishing disk
• Rinse and clean out debris
• Evaluate all margins and surfaces

Question 8. Mercury Hygiene.

Answer:

Mercury Hygiene:

• Follow aseptic technique
• Knowledge about mercury disposal and storage
• Use of proper ventilation
• Checking mercury levels periodically
• Avoid carpet/floor covering
• Storage of mercury in a closed container in an isolated area
• Use of pre-capsulated alloy
• Use of amalgamator
• Polishing, along with coolant
• Avoid direct contact with skin
• Use of evacuators
• Disposal in a closed plastic container
• Clean spilled mercury
• Remove protective clothing before leaving the operating area

Question 9. Differences between amalgam and inlay cavity

Answer:

Differences between amalgam and inlay cavity

Question 10. Resistance form in cavity preparation

Answer:

Resistance form in cavity preparation:

It may be defined as the shape and placement of the preparation walls that best enable the remaining tooth structure and the restoration to withstand, without fracture, masticatory forces delivered principally along the long axis of the tooth

Features:

• Relatively horizontal floors
• Box-like shape
• Inclusion of weakened tooth structure
• Prevention of cusps and marginal ridges
• Rounded internal line angles
• The adequate thickness of restorative material
• Reduction of cusps for capping, when indicated

Amalgam Short Answers

Question 1. High copper alloy.

Answer:

High copper alloy:

• Contains more than 6% copper

Types:

• Admixed
• Single composition

Advantages:

• Elimination of weakest 72-phase
• Improved mechanical properties
• Corrosion resistance
• Better marginal integrity

Question 2. Reverse Curve.

Answer:

Reverse Curve:

• Used in proximal preparation for class II amalgam restoration
• Indicated for broader contacts

Features:

• Curving proximal walls inwards towards the contact area

Importance:

• Useful as if excessive flare is given it results in weakening of tooth structure and fracture of restoration

Advantages:

• Conserves tooth structure
• Preserves marginal ridge
• Increases resistance for tooth and restoration

Question 3. Convenience form.

Answer:

Convenience form:

It is the form and shape of the cavity that enables ease of accessibility, visibility, and ease of operation

Features:

• Adequate extension
• Cavosurface margin
• Proximal clearance

Question 4. Retention locks.

Answer:

Retention locks:

• It is a secondary retentive form for class 2 cavity preparation
• Used for amalgam restoration
• Placed in the proximal or occlusal box
• Prepared where sufficient vertical tooth preparation permits

Question 5. Cavosurface angle /Butt joint.

Answer:

Cavosurface angle:

• It is an angle formed between the preparation wall and the external tooth surface

Factors Effecting:

• Location of tooth
• Type of restorative material
• The direction of enamel rods

Value:

• 90° for amalgam
• 110o-120o for cast

Significance:

• If increased results in restoration fracture
• If decreased results in tooth fracture

Question 6. Delayed expansion.

Answer:

Delayed expansion:

• If zinc-containing amalgam is contaminated by moisture during trituration or condensation a large expansion can take place
• It usually starts after 3-5 days and continues upto months reaching 400 pm
• This is called “delayed expansion”
• H₂O + Zn → ZnO + H₂ [gas]
• Effects of Liberated H₂ Gas

Produce internal stresses
↓
Expansion of mass
↓
Increased creep
Increased microleakage
Pitted surface and corrosion
↓
Dental pain
Recurrence of caries
Fracture of restoration

Question 7. Axio-pulpal line angle.

Answer:

Axio-pulpal line angle:

Line angle:

• Junction of two surfaces

Axio-pulpal line angle:

• The junction between the axial wall and pulpal floor

Significance:

• In amalgam restoration, there needs to be a curved axio-pulpal line angle
• Straight axio-pulpal line angle results in increased stress concentration over it leading to fracture

Question 8. Enameloplasty.

Answer:

Enameloplasty:

• It is the cauterization of the enamel surface

Reason:

• In the case of a deep pit and fissure, the bristles of the toothbrush are unable to reach those areas
• By cauterization/enameloplasty these areas are converted to self-cleansable areas

Features:

• Fissure present <l/3rd of enamel thickness
• Covering only a superficial portion of the enamel

Question 9. Bonded Amalgam restoration.

Answer:

Bonded Amalgam restoration:

Mechanism:

Resin liner mixes with amalgam
↓
Forms micromechanical union
↓
Increases retention
↓
The liner acts between hydrophobic amalgam and hydro–Philip’sp tooth

Indications:

• Weak preparation
• Extensive caries
• Deep bite
• Core foundation

Advantages:

• Dentin sealing
• Increased resistance
• Increased retention
• Conserve tooth structure
• Improved marginal seal
• Cost-effective

Question 10. Mulling.

Answer:

Mulling:

• Continuation of trituration
• Coat all alloy particles with mercury

Methods:

• Manually squeezing amalgam in chamois skin
• Mechanical – By increased trituration for 1-2 sec.

Question 11. Amalgampins.

Answer:

Amalgampins:

• Vertical posts of amalgam in dentin

Dimensions:

• Depth on the gingival floor – 1-2 mm
• Width – 0.5 -1 mm

Advantages: Increases resistance and retention

Question 12. Disposal of scrap amalgam.

Answer:

Disposal of scrap amalgam:

• Store all scrap amalgam in a tightly closed container either dry or under a radiographic fixer solution
• Amalgam scrap should not be stored in water
• If the scrap is stored dry, mercury vapor can escape into room air when the container is opened
• If the scrap is stored under a radiographic fixer solution, special disposal of the fixer may be necessary
• Dispose of mercury-contaminated items in sealed bags according to applicable regulations
• Do not dispose of mercury-contaminated items in regulated waste containers or bags or along with waste that will be incinerated
• Clean up spilled mercury properly using trap bottles, tape, or freshly mixed amalgam to pick up droplets and commercial cleanup kits
• Do not use a household cleaner

Question 13. Mercury hygiene

Answer:

Mercury hygiene:

• Follow aseptic technique
• Knowledge about mercury disposal and storage
• Use of proper ventilation
• Checking mercury levels periodically
• Avoid carpet/floor covering
• Storage of mercury in a closed container in isolated areas of pre-capsulated alloy
• Use of amalgamator
• Polishing, along with coolant
• Avoid direct contact with skin
• Use of evacuators
• Disposal in a closed plastic container
• Clean spilled mercury
• Remove protective clothing before leaving the operating area

Amalgam Viva Voce

1. Increasing copper content greater than 12% by weight in amalgam alloy suppresses the formation of more corrosive gamma-2 phase
2. High copper amalgamate is more corrosion-resistant than low copper amalgam
3. Mercury: alloy ratio in Eames technique is 1:1
4. Use of zinc-containing alloys results in delayed expansion
5. Tin-mercury gamma-2 phase is the weakest in dental amalgam
6. The threshold limit value for exposure to mercury va¬pour for a 40-hour work week is 50pg/m³

Fundamentals Of Cavity Preparation Important Notes

1. Angles in the cavity

2. Walls in cavity preparation

3. Steps in cavity preparation

• Initial cavity preparation
  • Outline form
  • Primary Retention form
  • Secondary Resistance form
  • Convenience form
• Final cavity preparation
  • Removal of carious dentin
  • Pulp protection
  • Secondary retentive and resistance forms
  • Finishing of external walls
  • Cleaning, inspecting, and conditioning

4. Resistance features

• Relatively flat floor
• Box shape

Read And Learn More: Operative Dentistry Short And Long Essay Question And Answers

• Preservation of cusps and marginal ridges
• Rounded internal and external line angles
• Cusp capping when indicated

5. Primary retentive forms

6. Secondary retentive and resistance form

• Locks, pins, slots, steps and amalgam pins in amalgam provide secondary resistance and retentive forms
• Grooves, groove extensions, beveled enamel margins, and luting cement provide secondary retentive and resistance forms in cast metal restorations

7. Purpose of bevelling

• Produces stronger enamel wall
• Permits marginal seal in slightly undersized casting
• Provides marginal metal that is more easily burnished and adapted
• Assists in sealing gingival margins of castings that fail to seat by a very slight amount

Fundamentals Of Cavity Preparation Long Essays

Question 1. Enumerate steps in cavity preparation. Explain the outline form, retention form, and resistance form.

Answer:

Steps In Cavity Preparation:

• Initial cavity preparation
• Outline form
• Primary Retention form
• Secondary Resistance form
• Convenience form
• Final cavity preparation
• Removal of carious dentin
• Pulp protection
• Secondary retentive and resistance forms
• Finishing of external walls
• Cleaning, inspecting, and conditioning

Outline Form:

• Placing the preparation margins to the place they will occupy in the final tooth preparation

Factors:

• Extension of all carious lesions
• Caries index
• Old restorative material
• Initial depth 0.2-0.8 mm
• Aesthetics

Features:

• Preserve cuspal strength
• Preserve marginal ridge
• Minimize extension
• Maintain initial depth to 0.2-0.8 mm
• Enameloplasty wherever required

Retention Form

• It is the form and shape of the cavity that resists the displacement of restoration from lifting and tipping forces

Features:

• Occlusal convergence
• Dovetail

Resistance Form

• “It is that shape and form of the cavity which enables both tooth and restoration to withstand without fracture the stresses of masticatory forces delivered principally along the long axis of the tooth”

Features:

• Box-shaped preparation
• Flat pulpal floor
• The adequate thickness of restorative material
• Preservation of marginal ridge
• Inclusion of weakened tooth structure
• Rounded internal line angles
• Cusp capping

Fundamentals Of Cavity Preparation Short Essays

Question 1. G.V. Black’s classification of cavity preparation.

Answer:

G.V. Black’s classification of cavity preparation:

Fundamentals Of Cavity Preparation Short Answers

Question 1. Reverse bevel.

Answer:

Reverse bevel:

• A reverse bevel is a bevel of generous width that is prepared on the facio margin of a reduced cusp with a flame-shaped, fine grit diamond instrument
• Its width should extend beyond any occlusal contact with opposing teeth
• It should be at an angle that results in a 30-degree marginal metal
• It should be wide enough so that the cave surface margin is beyond any contact with the opposing dentition

Question 2. Reverse curve.

Answer:

Reverse curve:

• Used in proximal preparation for class II amalgam restoration
• Indicated for broader contacts

Features:

• Curving proximal walls inwards towards the contact area

Importance:

• Useful as if excessive flare is given it results in weakening of tooth structure and fracture of restoration

Advantages:

• Conserves tooth structure
• Preserves marginal ridge
• Increases resistance for tooth and restoration

Fundamentals Of Cavity Preparation Viva Voce

1. GV Black simply classified cavities as one class of pit and fissure and four classes of smooth surface caries
2. Cavities that occur exclusively in posterior teeth are class 2 cavities
3. Cavities that occur both in anterior and posterior teeth are class 1 and 6
4. A cavity preparation that includes both internal and external cavity walls is termed intracoronal preparation
5. Enameloplasty is indicated when the fissure depth is not more than 1 /3rd the thickness of the enamel
6. The class 5 cavity preparation is convex mesiodistally
7. Cavities of the cusp tips of posterior teeth are class 6 cavities
8. The axial wall is the base of class 3 preparation.

Pulp Protection Important Notes

1. Methods of pulp protection

2. Effect of remaining dentinal thickness on pulp

3. Classification of pulp protective agents

• Cavity sealers
  • Varnishes
  • Resin bonding agents
• Cavity liners
  • Calcium hydroxide
  • GIC
• Cavity bases
  • Zinc phosphate
  • Zinc polycarboxylate
  • GIC

4. MTA (Mineral trioxide aggregate)

• It was developed by Torabinejad et al in 1993
• Used as a direct pulp capping agent
• Composed of tricalcium silicate, dicalcium silicate and traces of magnesium oxide, sodium sulphate and potas¬sium sulphate
• Bismuth oxide is added for radiopacity

Pulp Protection Short Essays

Question 1. Management of shallow and deep carious.

Answer:

Management of shallow and deep carious:

1. Shallow Caries:

Excavation of caries
↓
Application of liner over the axial and pulpal wall
↓
Placement of base
↓
Permanent restoration

2. Deep Caries:

Indirect Pulp Capping:

Direct Pulp Capping:

Question 2. Methods of protecting the pulp.

Answer:

Methods of protecting the pulp:

Depends on the use of restorative material and the depth of the cavity

Question 3. Zinc Phosphate.

Answer:

Zinc Phosphate:

High strength base

Composition

• Powder 
  • Zinc oxide – 90.2%
  • Magnesium oxide – 8.2% Water – 36%
  • Other oxides – 0.2%
  • Silica – 1.4%
• Liquid
  • Phosphoric acid – 38.5%
  • Aluminium phosphate – 16.2%
  • Aluminium – 2.5%
  • Zinc – 7.1%

Manipulation:

• Powder/liquid ratio – 1.4 g/0.5 ml
• Dispense on a cool dry glass slab
• Mix using a stainless steel cement spatula in a circular motion
• Mixing time: Each increment – 15-20 sec, total – 1 min.

Uses:

• Luting cement, bases
• Intermediate restorations, root canal restorations

Read And Learn More: Operative Dentistry Short And Long Essay Question And Answers

Question 4. Cement Bases.

Answer:

Cement Bases:

A layer of cement placed beneath permanent restoration

Types:

1. High strength – Thermal protection
2. Low strength – Chemical protection

Properties:

• Thermal fracture or distortion

Examples:

• Zinc phosphate
• GIC
• Calcium hydroxide

Pulp Protection Short Answers

Question 1. Varnish.
(or)
Give composition and objectives of varnishes.

Answer:

Varnish:

• It is an organic copal or resin gum suspended in solutions of ether or chloroform

Composition

• Solid- Copal resin
• Solvent- Ether, acetone, alcohol

Action:

• On application, it evaporates leaving behind a protective Film

Advantages:

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

Indications:

• Pulpal protection
• Sealing of dentinal tubules
• Reduces microleakage
• Protects tooth from chemical irritants

Contraindications:

• Under composite resin
• UnderGIC

Question 3. Liners.

Answer:

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

Indications:

• Pulpal protection
• Formation of reparative dentin

Materials Used:

• ZOE
• Calcium hydroxide
• Flowable composites
• GIC

Pulp Protection Viva Voce

1. GV Black simply classified cavities as one class of pit and fissure and four classes of smooth surface caries
2. Cavities that occur exclusively in posterior teeth are class 2 cavities
3. Cavities that occur both in anterior and posterior teeth are class 1 and 6
4. A cavity preparation which includes both internal and external cavity walls is termed intracoronal preparation
5. Enameloplasty is indicated when fissure depth is not more than l/3rd the thickness of enamel
6. The class 5 cavity preparation is convex mesiodistally
7. Cavities of the cusp tips of posterior teeth are class 6 cavities
8. The axial wall is the base of class 3 preparation.

Matricing Important Notes

1. Matrices

Matricing Short Essays

Question 1. Define matrix. Discuss different types of matrices
(or)
Define Matrix. Describe matrices used for class 2 restoration.
(or)
Matrices used in operative dentistry

Answer:

Matrix Definition:

• It is a device that is applied to a prepared tooth before the insertion of the restorative material to assist in the development of the appropriate axial tooth contours and to confine the restorative material excess

Types Of Matrices:

1. Based on the mode of retention

• With retainer- Tofflemire matrix
• Without retainer- Automattrix

2. Based on the type of band

• Metallic nontransparent matrices
• Non-metallic transparent matrices

3. Based on the type of cavity

• Matrix for class 1 cavity
  • Double band tofflemeir
• Matrices for class 2 cavity preparation
  • Single banded tofflemeir matrix
  • Rigid material supported sectional matrix
  • Ivory no. 8
  • Ivory no 6
  • Copper band matrix
• Matrices for class 3 cavities
  • Mylar strip matrix
  • S-shaped matrix
• Matrices for class 4 cavities
  • Custom lingual matrix
  • Mylar strip matrix
• Matrices for class 5 cavities
  • Window matrix
  • Cervical matrix

Matrices For Class 2 Restoration:

1. Ivory Matrix No. 1:

• For unilateral class 2

Parts:

• Claw
• Arms – 2 semicircle arms with pointed projections
• Tightening screw
• Band has a slightly projected part in the middle that is placed gingivally

Placement:

• Select and place the band
• Place the retainer
• Tighten the screw

2. Ivory Matrix No. 8:

• Band thin sheet of metal
• Circumference of it adjusted by screw

Read And Learn More: Operative Dentistry Short And Long Essay Question And Answers

• Used in unilateral/bilateral cases

3. Tofflemire Universal Matrix Band Retainer:

• Used in all types of tooth preparations

Parts:

• Head
• Slot
• Knurled nuts – Large and small

Placement:

• Open large Knurled nut
• Open a small knurled nut in the opposite direction
• Secure both ends of the band
• Place the band into a diagonal slot
• Tighten small knurled nut
• Place the retainer around the tooth
• Tighten large knurled nut

4. Compound Supported Matrix:

• Place the band around the tooth
• Secure it by sealing with an impression compound

5. Auto-Matrix:

• Preformed bands are available
• Adapt the matrix around the tooth
• Tighten the band with a locking device

6. T-shaped matrix:

• Made of brass, copper, or stainless steel
• The long arm of T surrounds the tooth and overlaps the short arm

Question 2. Matrix Band and Retainer.

Answer:

Matrix Band and Retainer:

Retainer:

• Holds the band in position and shape

Band:

• A piece of metal/polymeric material used to give support and form to the restoration while insertion and setting

Materials:

• Stainless steel
• Polyacetate
• Cellulose acetate
• Cellulose nitrate

Dimensions:

• Width –¼ %” to 3/8″ for permanent
  • 1/8” to 5/16″ for deciduous
• Thickness – 0.0015″ to 0.002″

Functions:

• Confines the restoration
• Provide good contour
• Provide surface texture
• Prevent overhanging

Requirement:

• Rigid
• Adaptability
• Easy to use
• Easy to removal
• Non-irritant
• Sterilizable
• Inexpensive

Question 3. Non-metallic matrix.
(or)
Matrices for tooth-colored materials

Answer:

Non-metallic matrix:

• Used for tooth-colored restoration

Types:

1. Celluloid strips – For silicate cement
2. Cellphone strips – For resins
3. Mylar strips – For composite and silicate

Technique:

• Obtain the desired length of the matrix
• Burnish it over the tooth
• Placement of wedge
• Restoring the tooth
• Hold the matrix till the initial setting

Indications:

• Class 3 and Class 4 restoration

Advantage:

• Simple to Use
• Economic

Disadvantage:

• Lack of stability

Matricing Short Answers

Question 1. Functions of the matrix.

Answer:

Functions of the matrix:

• Functions Of Matrix Are
• Rigidity
• Establishment of proper anatomic contour
• Restoration of correct proximal contact relation
• Prevention of gingival excess
• Convenient application
• Ease of removal

Question 2. Automatic.

Answer:

Automatic:

• Bands are performed and disposable
• Height of band-3/16″-5/16″
• The thickness of band – 0.038-0.05 mm

Steps:

Adapt matrix around the tooth
↓
Tighten the band with a locking device
↓
Restore the tooth
↓
Cut the band with a plier

Indications:

• Tilted and partially erupted teeth
• Complex amalgam restoration

Advantages:

• Simple
• Convenient
• Good visibility

Disadvantage:

• Expensive

Question 3. S-shaped matrix.

Answer:

S-shaped matrix:

Indications:

• Restoring the distal part of the canine and premolar
• Class 2 slot restoration

Advantages:

• Good contour

Disadvantage:

• Cumbersome

Technique:

• Twist the band in S shape
• Place interproximal over facial
• The surface of the tooth and the lingual surface of the bicuspid

Question 4. Copper Band.

Answer:

Copper Band:

Application:

Select an appropriate copper band that surrounds the tooth
circumferentially 1-2 mm beyond the preparation margins
↓
Mount it over the softened stick of compound
↓
Fill it with restoration
↓
Place it over the tooth

Indication – Class 5 preparation

Advantage – Simple, Good contour

Question 5. Sectional matrix system.

Answer:

Sectional matrix system

• It consists of dead soft metal matrices available in various shapes, thicknesses, and sizes
• They are selected according to the tooth to be restored

Indications:

• For small to moderate class 2 cavities involving one or both proximal surfaces in posterior teeth
• For both amalgam and composite restorations

Advantages:

• Easy to use
• Good visibility
• Contact dimensions are adequate
• Gingival adaptation of restoration is good

Disadvantages:

• Expensive
• Matrix bands may become dented easily

Matricing Viva Voce

1. Matrix system consists of a matrix band, retainer, and wedges
2. The thickness of a matrix band is 0.002 inches
3. Matrix retainers are gadgets used to retain the matrix bands in position
4. Tofflemire matrix band retainer is ideal to use when MOD preparation is done
5. Automatrix is a retainer less matrix system with 4 types of bands used to fit all teeth
6. Ideally the matrix band should be positioned 1mm apical to the gingival margin and 1-2 mm above the adjacent marginal ridge
7. Tofflemire matrix is the universal matrix
8. Compound-supported matrix is also called custom- made matrix or anatomical matrix
9. T band matrix is performed T-shaped matrix without a retainer