Operative Dentistry

Separation Important Notes

1. Types of separators

• Two types
  • Slow separation
    • The teeth are separated by inserting certain materials between them
  • Rapid separation
    • It is achieved by the wedge principle and traction principle

2. Wedges

Separation Short Essays

Question 1. Separation of teeth / Tooth Separators / Indication of Separators.

Answer:

Separation of teeth / Tooth Separators / Indication of Separators:

Definition:

It is the process of separating the involved teeth slightly away from each other or bringing them closer to each other and/or changing their spatial position in one/more dimension

Purpose:

• Diagnosing the proximal caries
• Accessibility to proximal area
• Polishing of proximal restoration
• Matrix placement
• Removal of foreign bodies
• Repositioning shifted teeth

Methods:

1. Slow/Delayed Separation:

• Rubber ring/band
  • Orthodontic purpose
  • Needs 2-3 days to 1 week
• Rubber dam sheet
  • Heavy/extra-heavy type used
  • Needs 1-24 hours/more
• Ligature wire
  • Separation in 2-3 days
• Oversized temporary crowns
• Fixed orthodontic appliances

2. Rapid/Immediate Separation:

• Traction principle:
  • Ferrier double bow
  • Has 2 bows, each bow engages the proximal tact area of the tooth

• • Use – Tooth preparation
  • Finishing and polishing
• Wedge principle:
  • Elliot separator
  • Wedges

Question 2. Wedges and Wedging methods.

Answer:

Wedges:

• Devices for rapid tooth separation

Functions:

• Rapid tooth separation
• Prevent overhanging restoration
• Stabilizes matrix band
• Gingival retraction
• Adapt/contour restoration in cervical areas

Types:

1. Wooden Wedges:

• Easily trimmed
• Shapes:
  • Triangular
  • Round

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

2. Plastic Wedges:

• Light transmitting wedge
• Used for composite restoration
• Size: Length of wedge 1-1.2 cm

Wedging Techniques:

1. Double Wedging:

• Two wedges are used
• One inserted from the buccal embrasure
• Other from the lingual embrasure

2. Wedge Wedging:

• Two wedges are used:
  • One inserted from the lingual embrasure
  • Another Inserted between the first wedge and matrix band
• Indication 
  • The mesial aspect of maxillary first premolar due to the presence of flutes

3. Piggyback Wedging:

• Two wedges are used:
  • A larger one inserted from the lingual embrasure
  • Smaller one is placed over it
  • Use – Gingival recession

Separation Short Answers

Question 1. Elliot Separator.

Answer:

Elliot Separator:

• Synonym: Crab-claw separator

Parts:

• Bow
• Two holding jaws
• Tightening screw

Placement:

• Place the jaws gingival to the contact area
• Tighten the screw in a clockwise direction

Precaution:

• Avoid tooth separation beyond the thickness of PDL i.e. 0. 2-0.5mm

Uses:

• Diagnosis of proximal areas
• Polishing of proximal restoration

Separation Viva Voce

1. Wedges are third component of the matrix system
2. Wedges must be triangular or trapezoidal in cross-section
3. The gingival aspect of the wedge may be lightly moistened with lubricant to facilitate its placement
4. The tightness of the wedge is tested by pressing the tip of an explorer firmly at several points along the middle two-thirds of the gingival margins
5. A triangular wedge is used for preparations with mar-gins deep in the gingival sulcus
6. A round wedge is used for preparations with margins coronal to the gingival sulcus
7. The wedge is kept as short as possible

Sterilisation And Infection Control Important Notes

1. Critical items

• Includes instruments that contact tissues or penetrate tissues
• Usually, there are disposable or single-use items
• Example: scalpels, blades, endodontic files, syringes, etc

2. Semi-critical items

• Items that are handled by gloved hands coated with blood and saliva or that may touch mucosa
• These can be either disposable or they can be cleared, sterilized or disinfected
• Example:  air water syringe tip, suction tips, prophy angle, handpiece

3. Noncritical items

• These are environmental surfaces such as chairs, benches, floors, walls, and supporting equipment
• They are not ordinarily touched during treatment
• These surfaces can be cleaned, disinfected, and covered

Sterilisation And Infection Control Long Essays

Question 1. Discuss various methods of sterilization.

Answer:

Various methods of sterilization:

Sterilization:

It is defined as the process by which an article, surface, or medium is freed of all living organisms either in a vegetative/spore state. Its method is.

Steps:

1. Presoaking:

• Prevent drying of blood, saliva, and debris
• Facilitate cleaning

2. Cleaning:

• Remove blood and saliva

Types:

1. Manual – Use of nylon brushes + detergents
2. Ultrasonic – Provide fast and thorough cleaning
3. Enzyme cleaning – Has specific catalytic behavior

3. Packaging:

• Protects instruments from contamination after sterilization and before use

Materials:

1. Self-sealing
2. Paper plastic
3. Peel pouches

• Sterilization
• Monitoring of sterilization
• Handling of processed instruments

Sterilization of Different Instruments:

Question 2. Infection Control.

Answer:

Methods:

Immunization: Vaccination recommended for Hepatitis B for all dental personnel

Personal Barrier

1 Handwashing:

2. Gloves:

• Protects against contamination
• Changed between patients and for the same patient if it is worn/torn

Types:

1. Surgical
2. Latex
3. Vinyl
4. Double gloves for HBV and HIV [Hepatitis B Virus and Human Immunodeficiency Virus]

1. Face masks:

• Protects from inhalation of aerosols
• Prevents spatter from patient’s mouth
• Prevents splashes of contaminated solution
• Changed once per hour/between patients/whenever it becomes moist

2. Protective clothing:

• Reusable/disposable gowns with long sleeves, high neck, and long knee length

3. Eyewear:

• Prevention against Hepatitis B
• Prevent bacterial/viral contact

Surgical Asepsis:

• Preparation of surgical site
• Draping the patient

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

• Isolation

Surface Asepsis:

• Sterilization of instruments
• Use of disposable instruments
• Wrapping with aluminum foil or applying disinfectant to things that are often touched during treatment such as dental light, chair

Disposable of waste:

• Methods:
  • Incineration
  • Burial in a landfill
  • Discharge of liquid to a sewer
  • Sterilization

Sterilization And Infection Control Short Essays

Question 1. Hot Air Oven.

Answer:

Hot Air Oven:

Component:

1. Chamber with double wall

• Inner-copper plate
• Outer – Asbestos

2. Adjustable holes – Monitor time and temperature

3. Thermostat – Regulate temperature

Time And Temperature:

• 160°C – 1 hour
• 180°C – Vz hour

Instruments That Can Be Sterilized:

• Glassware, forceps, scissors, scalpels, swabs

Precautions:

• Fitted for even distribution of air
• Not overloaded
• Arranged to allow free circulation
• Cooled for 2 hours before opening the door.

Question 2. Autoclave.

Answer:

Autoclave:

Principle:

• Water boils when its vapor pressure equals that of the surrounding atmosphere
• Steam is produced
• It condenses to water as it contacts the surface and transfers its latent heat to it.

Time And Temperature:

• 121°C – 15 minutes at 15 lbs pressure
• 136°C – 3 minutes at 30 lbs pressure

Articles That Can Be Sterilized

• Culture media, saline, syringes, needles, dressings, gloves, aprons, gowns

Advantages:

• Rapid
• Effective
• Good penetration

Question 3. Glass bead sterilization.

Answer:

Glass bead sterilization:

• A rapid method of sterilization
• Salt used: 1% sodium silico-aluminate, sodium carbonate, or magnesium carbonate
• Salt is replaced by glass beads provided the beads are smaller than 1 mm in diameter as larger beads enable to transfer of heat to the endodontic instrument
• Time: 5-15 seconds, Temperature – 437 – 465°F

Disadvantage:

• The handle portion is not sterilized

Advantages:

• Economic
• Salt does not clog the root canal

Sterilisation And Infection Control Short Answers

Question 1. Autoclave

Answer:

Autoclave:

Autoclave is the process of sterilization by saturated steam under high pressure above 100 degrees C temperature

Sterilization Conditions:

Uses:

• Articles sterilised in autoclave are:
• Culture media
• Rubber articles like tubes, gloves, etc
• Syringes and surgical instruments
• OT gowns, dressing materials
• Endodontic instruments
• Hand instruments

Question 2. Contour.

Answer:

Contour:

• Buccal and lingual surfaces of teeth possess some degree of convexity
• Facilitate seepage of food
• Present over cervical third on facial surfaces of all the teeth, lingual surfaces of incisors, and canines.
• Middle third – On lingual surfaces of posteriors

Significance:

1. Normal contour

• Shunt food toward the buccal vestibule
• Stimulate intervening tissues

2. Over contour

• Plaque accumulation
• Interferes with self-cleaning action

3. Under contour

• Opening of embrasure
• Affect the gingival

Question 3. Contacts.

Answer:

Contacts:

Significance:

• Broad contact faciolingually
  • Prevents seepage of food
• Broad contact occlusogingivally
  • Sticky food is held
  • Irritates gingiva
• Contact located apically
  • Packing of sticky food
  • Impinges tissue
• Contact located initially
  
• • Predisposes to proximal caries
  • Prevents food being pushed into embrasures
• Contact located buccally
• Loose contact
  • Food lodgement
  • Gingival problems
  • Caries

Question 5. Embrasures.

Answer:

Embrasures:

• V-shaped spaces originating at the proximal contact area between adjacent teeth
• Types – Facial, lingual, incisal/occlusal and gingival

Functions:

• Serve as spillways for the escape of food
• Prevents forcing the food into the contact area

Sterilisation And Infection Control Viva Voce

1. Disinfectants containing 70-90% ethyl alcohol are considered the most effective disinfectants on cleaned surfaces
2. Sterilants used for high-level disinfection of items for reuse are glutaraldehydes at 2-3 % concentrations
3. Sterilization must be tested routinely
4. Autoclave is done at 121°C temperature for 15 min at 15 lb pressure
5. Chemiclave is done at 131°C for 30 min at 20 lb pres-sure
6. Too little contour may result in trauma to the attachment apparatus
7. Improper contact can result in food impaction between teeth
8. When embrasures are decreased in size, additional stress is created on teeth
9. Lingual embrasures are usually larger than facial embrasures

Dental Caries

Question 1. Zinc polycarboxylate cement.
Answer:

Composition:

1. Powder:

• Zinc oxide Basic ingredient
• Magnesium oxide
  • Modifier
  • Aids in sintering
• Bismuth and aluminum oxide occur in small amounts
• Stannous fluoride
  • Increase strength
  • Modifies setting time
  • Imparts anti-cariogenic properties

2. Liquid:

• Polyacrylic acid
• The copolymer of acrylic acid with other unsaturated carboxylic acids

Properties:

1. Physical properties:

2. Biocompatibility:

• Mild pulpal response

3. Adhesion:

• Excellent adhesion
• Polyacrylic acid reacts with calcium ions via car¬boxyl groups on the surface of enamel and dentin
• The bond strength of enamel is greater

4. Optical properties:

• It is very opaque

5. Thermal properties:

• It is a thermal insulator

Uses:

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

Question 2. Define and classify caries. Add a note on the diagnosis of caries.

Answer:

Caries Definition:

• Dental caries is defined as a multifactorial, transmissible, infectious oral disease caused primarily by the complex interaction of cariogenic oral flora with fermentable dietary carbohydrates on the tooth surface over time

Caries Classification:

1. According to location

• Primary caries
  • Pit and fissure caries
  • Smooth surface caries
  • Root caries
• Secondary caries

2. According to the direction

• Forward caries
• Backward caries

3. According to the extent

• Incipient caries
• Cavitated caries

4. According to rate

• Acute caries
• Chronic caries

5. According to a histological depth of penetration

• Enamel caries
• Dentinal caries

Diagnosis Of Caries

1. Visual Tactile Examination:

• Visual method:
  • Cavitation
  • Opacification
  • Discoloration
  • Surface roughness
• Tactile method:
  • Softness of enamel
  • Catch obtained by an explorer
• Illumination:
  • UV light creates decreased fluorescent in carious lesions as compared to healthy tissue
  • Cavitation produces echoes of higher amplitude

2. Caries detecting dyes:

• Dyes for enamel caries:
  • Procion Staining is irreversible
  • Reacts with nitrogen and hydroxyl groups
  • Calcein Bounds with calcium
  • Zyglo ZL22 Visible by UV illumination
• Dyes for dentin caries:
  • Infected and affected dentin layers are present
  • Basic Fuschia in propylene glycol stains only the infected dentin
• Radiographic methods:
  • Requires 50% tooth destruction
  • Seen as a radiolucent lesion

Caries Types

1. Conventional:

• IOPA
• Bitewing For proximal caries
• Occlusal
• Xeroradiography
• Edge enhancement

2. Advanced:

• Digital radiography
• Subtraction radiography
• RVG

3. Electrical Conductance:

• Electrical conductivity is directly proportional to the amount of demineralization

4. Lasers:

Question 3. Methods of Diagnosis of proximal caries.

Answer:

1. Bitewing Radiograph:

• It includes occlusal surfaces of both arches in the same radiograph
• It must be differentiated from cervical bum out
• It describes the extent of the carious lesion
  • 0 Normal
  • 1 – Only enamel is involved
  • 2-  Caries extends upto DEJ/Dentinoenamel junction
  • 3 – Caries involve the whole of the enamel and the outer half of the dentin
  • 4 – Caries involve complete enamel and dentin

2. – Separation of Teeth:

• With the help of separators, teeth are moved apart and viewed for carious lesions

3. Dental Floss:

• Dental floss is used through the proximal surface
• Fraying of it indicates the presence of a lesion

4. Transillumination:

• It is based on the refractory index between the carious and sound tooth
• Carious tooth appears as a dark shadow when compared to normal tooth

Question 4. Pit and fissure Caries.

Answer:

• The shape of pit and fissure make it more susceptible to caries

Pit and fissure Caries Features:

• Initial Brown/Black in color
• Catch with an explorer
• DecalciFication of enamel
• Enamel involvement in the direction of the rod
• Shape Triangular, base towards DE
• Progress to the involvement of dentinal tubules
• Result in cavitation
• Undermining of enamel

Question 5. Root Caries/Cemental Caries.

Answer:

• It is a soft, progressive lesion that is found anywhere on the root surface that has lost its connective tissue attachment and is exposed to the environment

Root Caries Features:

• Periodontal attachment loss
• Soft, irregular lesion
• Round or oval in shape
• Irregular outline
• Common in males
• Common in mandibular molars

Etiology:

• Streptococcus mutants
• Lactobacillus
• Actinobacillus

Root Caries Prevention:

• Plaque removal
• Diet modification
• Use of topical fluoride
• Soft tissue management
• Use of xylitol-containing chewing gum

Question 6. Roles of fluoride in caries prevention

Answer:

1. Increased enamel resistance/ reduction in enamel solubility

• Dental caries involves the dissolution of enamel by acid formation
• This dissolution is inhibited by fluoride as the fluoride forms fluorapatite which reduces enamel solubility
• Fluoride reduces enamel solubility also by promoting the precipitation of hydroxyapatite and phosphate mineral
• Fluoride inhibits demineralization by
• Reducing bacterial acid production
• Reducing equilibrium solubility of apatite
• By fluoridation of apatite crystal

2. Increased rate of post-eruptive maturation

• Newly erupted teeth have hypomineralised areas and the enamel surface is also prone to dental caries
• Fluoride increases the rate of mineralization of these areas
• Organic material is also deposited over the enamel surface which increases its resistance to dental caries

3. Remineralization of incipient lesions

• Fluoride enhances remineralization by the deposition of minerals into the damaged areas
• This reduces enamel solubility through the growth of crystals which are more resistant to acid
• Fluoride enhances remineralization from calcium phosphate solution by the formation of calcium fluoride which prevents hydroxyapatite crystal growth

4. Interference with microorganisms

In two ways

• In high-concentration bacteriocidal
  • By reducing plaque
• In low-concentration bacteriostatic
  • Inhibits enzymes responsible for acid metabolism

5. Modification in tooth morphology

• If fluoride is ingested during tooth development it results in the formation of
• More caries-resistant tooth
• A tooth with smaller and shallow fissures
• Smaller diameter and cusp depth
• All these make them more self-cleansing

Question 7. Zones of enamel caries

Answer:

1. Zone 1 Translucent zone

• It is the deepest zone
• It is slightly more porous
• Contains 1% by volume
• Pores are larger than usual pores seen in normal enamel
• Dissolution of mineral occurs at the junction of prismatic and interprismatic enamel

2. Zone 2 Dark zone

• Located superficial to the translucent zone
• Excessive demineralization of enamel occurs
• It is narrow in rapidly advancing caries and wide in slowly advancing caries
• Contains 24% pore volume
• Pores are smaller than that of the translucent zone
• There is some degree of remineralization

3. Zone 3 body of the lesion

• Present between dark zone and surface zone
• Represents the area of greatest demineralization
• Pore volume is between 525%
• Contains larger apatite crystals
• Reprecipitation of minerals occurs
• Dissolution of minerals occurs
• Lost minerals are replaced by unbound water and organic matters

4. Zone 4 Surface zone

• It remains unaffected
• It is 40 pm thick
• Surface remineralization occurs due to the active precipitation of mineral ions

Question 8. Zones of dentinal caries.

Answer:

• Zone 1: Normal dentin
  • Zone of fatty degeneration of odontoblast
  • Represents thinner most layer of carious dentin
  • No crystals are present in the lumen of tubules
  • No bacteria present in tubules
  • Intertubular dentin has normal collagen

Zone 2: Subtransparent dentin

• • Zone of dentinal sclerosis characterized by deposition of calcium salts in dentinal tubules
  • The superficial layer shows areas of demineralization and damage of odontoblastic processes
  • It is capable of remineralization
  • No bacteria is present in tubules

Zone 3: Transparent dentin

• Zone of decalcification of dentin, a narrow zone preceding bacterial invasion
• It is softer than normal dentin
• Large crystals are present within the lumen of dentinal tubules
• No bacteria is present in tubules
• It is capable of self-repair and remineralization

Zone 4: Turbid dentin

• Zone of bacteria] invasion of decalcified but intact dentin
• Widening and distortion of dentinal tubules
• Cannot undergo self-repair or remineralization
• Must be removed before restorative treatment

Zone 5: Infected dentin

• Zone of decomposed dentin
• It is the outermost zone of carious dentin
• Characterized by complete destruction of dentinal tubules
• Areas of decomposition of dentin occur along the direction of dentinal tubules called liquefaction foci of Miller
• Transverse clefts are seen due to the decomposition of dentin
• Bacteria invade and destroy peri and intertubular dentin

Instruments Important Notes

1. Classification of instruments

• According to Marzouck:
  • Exploring Instruments
  • Tweezer
  • Retractor
  • Probe/Explorer
• An instrument for tooth structure removal
  • Excavators
  • Chisels
• Restoring instruments
  • Spatulas
  • Burnishers
  • Condensers
  • Carvers
• Finishing and polishing instruments
  • Stones
  • Brushes

2. Types of grasps:

• Modified pen
• Inverted pen
• Palm and thumb
• Modified palm and thumb

3. Materials used for sharpening stones:

4. Speed ranges:

5. Common shank design

• Straight
• Latch type
• Friction grip

6. Different instruments

Chisels:

• Has a straight shank and bevel on one side only
• Used with both pull and push motion
• Used to cleave or split undermined enamel
• Used to flatten pulpal floors

Enamel hatchet:

• The cutting edge is parallel with the long axis of the handle and beveled on one side

Enamel hatchet Uses:

• • To split undermined enamel
  • For placing grooves

Gingival marginal trimmer:

• • It is an enamel hatchet with a curved blade
  • It is 4 figure formula instrument
  • Has cutting edge at an angle more than 90° to the axis of the blade

Gingival marginal trimmer Uses:

• • For bevelling gingival margin
  • For bevelling axiopulpal line angle

Hatchet:

• It has the cutting edge of the blade directed in the same plane as that of the long axis of the handle
• It is beveled

Hatchet Uses:

• For preparing retentive areas in anterior teeth
• For sharpening internal line angles for DFG

Hoe:

• The cutting edge is perpendicular to the long axis

Hoe Uses:

• To give form to the internal parts of the cavity used on the enamel of posterior teeth

Angle former:

• It is a combination of GMT and chisels

Angle former Use:

• For sharpening line angles or obtaining retention in dentin

Spoon excavator:

• The cutting edge is either claw-like or circular
• The circular is known as discoid
• Claw-like is known as cloud

Spoon excavator Uses:

• For removing caries
• For carving amalgam

Knives:

• Used for trimming excess filling material

Files:

• Used to excess filling material, especially on gingival margins

7. Types of burs:

Instruments Viva Voce

1. When the second number in the instrument formula is 90100, the pair is used on the distal gingival margin
2. When the second number is 7585 it is used in the mesial margin
3. 100 and 75 pairs are used for inlayonlay preparation
4. 90 and 85 pairs are used for amalgam preparations
5. The modified pen grasp and inverted pen grasp are used universally
6. The modified palm and thumb grasp is usually employed in the area of the maxillary arch
7. Low speed is used for caries excavation, finishing, and polishing procedures
8. High speed is used for efficient cutting and removing old restorations
9. The neck of the instrument tapers from the shank diameter to a smaller size immediately adjacent to the head
10. The neck transmits rotational and translational forces to the head
11. Carbide burs normally have blades with slight negative rake angles

Instruments Short Answers

Question 1. Slow speed.

Answer:

Range:

• 5002500 rpm

Bur Used:

• Steel bur

Uses:

• Polishing
• Finishing
• Drilling holes
• Implants
• Excavation of caries

Advantages:

• Good tactile sense

Disadvantages:

• Inefficient
• Operator fatigue
• Patient discomfort

Question 2. 245 bur.

Answer:

• It is nonstandard carbide bur
• Designed to combine rounded corners with flat ends
• ADA size number 330L
• ISO size number 008
• Head diameter 0.80 mm
• Head length 3 mm
• Shape pear, elongated

Question 3. Enamel Hatchet.

Answer:

• Paired instrument
• Blade angle 4590°
• Bevel Unibevel/Bibeveled

Use:

• Unibevelled instrument
• Cleaving of enamel
• Planning of dentinal walls

1. Bibevelled:

• Use in a chopping motion
• Refine line and point angle

Question 4. AngleFormer.

Answer:

• Type of excavator, mono-angled instrument
• Cutting edge angle 8085°
• Paired instrument
• Blade Beveled on sides as well as at the end
• Manner of using Push or pull motion
• Use Establish retention form in DFG restoration
• Planning the gingival cavosurface margin

Question 5. High Speed.

Answer:

• Speed 20,000 1,20,000 RPM
• Burs used diamond burs with lubricant

Uses:

• Tooth preparation
• Refining tooth preparation
• Refining occlusion

Advantages:

• Fine tactile sense
• Minimum over cutting

Disadvantages:

• Heat production
• Not fit for larger preparation
• Operator fatigue

Question 6. Dental Bur.

Answer:

Definition:

It is defined as a rotary cutting instrument with cutting heads of various shapes and two or more sharp-edged blades, used as a rotary grinder

Classification:

1. According to their mode of attachment to handpiece

• Latch type
• Friction grip type

2. According to their composition

• Stainless steel
• Tungsten carbide
• Combination

3. According to their motion

• Right bur Revolves clockwise
• Left bur Revolves anticlockwise

4. According to the length of their head

• Long
• Short
• Regular

5. According to their use

• Cutting burs
• For finishing and polishing

6. According to their shapes

• Round
• Pear shaped
• Inverted cone
• Wheel shaped
• Tapering fissure
• Straight fissure

Question 7. Grasps are used with Hand Instruments.

Answer:

1. Modified Pen Grasp:

• Middle finger pad placed over shank
• Index finger Bend over middle phalanges and placed over the middle finger
• Thumb Placed on the opposite side of the instrument

Advantages:

• Creates tripod effect
• Enhances instrument control stabilizers instru¬ment

Uses:

• Commonly used in mandibular teeth

2. Inverted Pen Grasp:

• Similar to a modified pen grasp
• Palm faces toward the operator

Uses:

• Lingual surface of maxillary anterior
• Occlusal surface of maxillary posteriors

3. Palm and thumb grasp:

• The shaft placed on the palm of the hand and grasped by four fingers
• The thumb is free to control movements

Use:

• Holding handpiece
• Cutting incisal retention for Class 3

4. Modified Palm and Thumb Grasp:

• Provides more control to avoid slipping of instrument
• Used for maxillary anterior

Question 8. Speed in operative Density

Answer:

Question 9. Rake angle.

Answer:

• It is the angle between the rake face and the radial line
  • Positive Rake Angle Radial line is ahead of rake face
  • Negative Rake Angle Rake face is ahead of radial line
  • Zero Rake Angle Rake face and radial line coincide

Question 10. Wedel Staedt Chisel.

Answer:

• Have slightly curved shanks
• Used on anterior teeth
• It is a single plane, unibevel instrument
• Used for cleaving undermined enamel

Question 11. Balancing of Hand Instrument.

Answer:

• Balancing is achieved by providing angles in the shank of the instrument so that the cutting edge is within 23 mm of the long axis of the instrument
• It provides better access
• It is also called contra angling

Question 12. Spoon Excavator.

Answer:

• It is a modified hatchet
• Double ended instrument
• BladeSpoon, claw or disk-shaped
• Use Removal of caries and debris
• Manner of use Scooping motion

Question 13. Advantages and Disadvantages of Burs.

Answer:

Advantages:

• Precise
• Easy to control
• Tactile perception
• Removal of debris

Disadvantages:

• Pain
• Vibration
• Noise production
• Pulpal damage
• Over cutting

Instruments Short Essays

Question 1. Classify hand-cutting instruments.

Answer:

According To Gv Black:

1. Cutting Instruments.

• Hand
• Hatchet
• Chisel
• Hoe

2. Condensing Instruments Pluggers.

3. Plastic Instruments.

• Plastic filling instrument
• Cement carriers
• Carvers

4. Finishing and Polishing Instruments.

• Orangewood sticks
• Polishing points

5. Isolation Instruments

• Saliva ejector, evacuating tips.

6. Miscellaneous

• Mouth mirror, probe.

Question 2. Hand-cutting instruments.

Answer:

1. Excavators:

Excavators Types:

• Hatches:
  • The cutting edge of the blade is directed in the same plane as that of the long axis of the handle
  • It is beveled
    • Uses:
      • Used in anterior teeth for preparing retentive areas
      • Sharpening of line angles
      • In preparation for a direct gold restoration
• Hoes:
  • The cutting edge of the blade is perpendicular to the axis of the handle
    • Uses:
      • Planing tooth preparation walls
      • For forming line angles
• Angleformers:
  • Monoangled instrument
  • The cutting edge is at 90 degrees to the bladder
    • Uses:
      • Sharpening line angles
      • Creates retentive features in dentin in gold restoration preparation
• Spoon excavator:
  • Blades are slightly curved and cutting edges are either circular or clawlike
    • Uses:
      • To remove caries
      • Carves amalgam or direct wax pattern

2. Chisels:

• Used for cutting enamel
• Grouped into

1. Straight, slightly curved or bangle chisels:

• It has a straight shank and blade with a bevel on only one side
• The edge is perpendicular to the axis of the handle

2. Enamel hatchet:

• Paired instrument
• Blade angle 4590°
• Bevel Unibevel/Bibeveled

Enamel hatchet Use:

• Unibevelled instrument:
  • Cleaving of enamel
  • Planning of dentinal walls
• Beveled:
  • Use in a chopping motion
  • Refine line and point angle

3. Gingival margin trimmer:

• It is a modified hatchet with opposite curva¬ture and bevels
• Paired instrument Distal and mesial
• Instrument formula 7585 Mesial GMT, 95100 Distal GMT

Gingival margin trimmer Use:

• Planning of gingival cavosurface margin
• Removal of unsupported enamel
• Bevel axiopupal line angle in Class 2

Question 3. Bur design.

Answer:

• The design of the bur includes the following

1. Blade or cutting edge:

• It is in contact with the horizontal line or face

2. Tooth face:

• The sides of the tooth head of the cutting edge in the direc¬tion of the rotation is the tooth face

3. Back of the tooth:

• The opposite of the bur tooth is the back of the tooth

4. Rake angle:

• It is the angle between the rake face and the radial line
  • Positive Rake Angle Radial line is ahead of the rake face
  • Negative Rake Angle Rake face is ahead of the radial line
  • Zero Rake Angle Rake face and radial line coincide

5. Clearance angle:

• It is the angle between the back of the tooth and the work
• Mostly it is straight and clearly defined

6. Tooth angle:

• It is the measurement between the face and the back

7. Flute or chip space:

• It is the space between successive teeth
• The number of teeth in a bur is 6 or 8

Question 4. Instrument Nomenclature.

Answer:

• Order Purpose of instrument Example: Excavator
• Suborder Manner of use Example: Push or pull
• Class Form of working end Example: Hatchet, chisel
• Subclass shape of the shank Example: Monoangle

Question 5. Instrument Formula.

Answer:

Unit-1:

• Blade width
• Represents the width of the blade in tenths of a millimeter

Unit-2:

• Blade length
• Expressed in millimeter

Unit-3:

• Blade angle
• The angle formed between the blade and the long axis of the instrument
• Expressed in 100th of a circle

Unit-4:

• Cutting edge angle
• The angle formed between the cutting edge and the long axis of the handle

Question 6. Chisels.

Answer:

Chisels Types:

1. Straight chisels:

• Straight blade in line with handle and shank
• Cutting edge on one side

2. Monoangle chisels:

• Blade angle to the shaft
• Maybe medially or distally

3. Biangle chisel:

• Two angles between the shaft and blade
• Unibevelledmedially or distally

4. Triangle chisel:

• 3 angles in the shank
• Used for flattening the pulpal floor

Question 7. Excavators.

Answer:

• Used for removal of caries
• Refining internal line angles

Excavators Types:

1. Hatchet:

• The blade of the hatchet is perpendicular to the shaft
• The cutting edge is parallel to the shaft
• Paired i.e. right and left
• Used for delicate cutting

2. Hoe excavators:

• Single planed instrument
• Unibevelled
• Used with a push motion
• Used for cutting axial walls

3. Spoon excavators:

• Paired instruments
• Double planed instruments
• Used for removal of the decayed dentin

4. Cleoid excavator:

• Blade resembles a claw
• Used for amalgam carving, excavating decay in difficult areas