Instruments In Operative Dentistry Short Essays

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