Instruments - OPD Lab

HANDLE OR SHAFT

• Part grasped in the operator’s hand.

• Usually straight.

• It is smooth, knurled, and/or serrated for better instrument control

SHANK

• Connects the handle to the blade or nib.

• Smooth, round, tapered, and contrangled.

• Have one or more bends to avoid the tendency to twist in use where force is applied.

Shank Angles

• Straight

• Mon-angle (one)

• Bin-angle (two)

• Triple-angle (three)

• Contra-angled

BLADE OR NIB

• The working part of the instrument, begins at the last angle.

CUTTING: Blade

NON-CUTTING: Nib

The end of the Nib, or working surface, is known as FACE

• Function

• Manner of Use

• Design of the Working End

• Shape of shank

BLACK’S CLASSIFICATION SYSTEM BY INSTRUMENT NAME

categorized instruments by:

3-number code: WLA

1. Width of the blade (tenths of an MM)

2. Length of the blade (MM)

3. Blade Angle (relative to the long axis of the handle in clockwise centigrade or hundredths of a circle)

What’s the instrument formula? - 3-number code:

4-number code: WCLA

1. Width of the blade (in tenths of a mm)

2. Cutting edge angle (degrees centigrade) Instrument is positioned so that this number always exceeds 50.

3. Length of the blade (in mm)

4. Blade Angle (relative to the long axis of the handle in clockwise centigrade or hundredths of a circle) Instrument is positioned such that this number is always 50 or less.

360

The centigrade angle is expressed as a percent of _____ degrees

e.g. 85 = 85% x 360 degrees = 306 degrees

e.g. 14 = 14% x 360 degrees = 50.4 degrees

Explain how to solve for the angle

Interpret:

e.g. 85 = ?

e.g. 14 = ?

PRIMARY CUTTING EDGE

BEVELS

Single bevel on the end of the blade

SECONDARY CUTTING EDGES

BEVELS

Two additional BEVELS extending from the primary edge.

• spoon excavator

• gingival margin trimmers

• enamel hatchets

What are single-beveled instruments?

• If bevel is on the right - RIGHT INSTRUMENT - moved from right to left

• If bevel is on the left - LEFT INSTRUMENT - moved from left to right

RIGHT and LEFT BEVELS

(Single-beveled instruments: spoon excavator, gingival margin trimmers, enamel

hatchets)

• Chisels

• Hoes

MESIAL and DISTAL BEVELS - EXAMPLES

DISTAL BEVEL

If primary bevel is not visible - ?

MESIAL or REVERSE BEVEL

If primary bevel is seen - ?

Excavators

• For removal of carious tissue, refinement of the internal aspects of the preparation

• Establishment of correct anatomical restoration

• Ordinary Hatchets

• Hoes

• Angle Formers

• Spoons

Examples of Excavators

Excavators - ORDINARY HATCHETS

• Primarily on anterior teeth for preparing retentive areas

• Sharpening internal line angles, particularly for direct gold restorations.

Excavators - HOES

• For planing tooth preparation walls and for forming line angles.

• Commonly used in Class III and V preparations to ensure removal of unsupported enamel

Excavators - ANGLE FORMERS

• For sharpening line angles and creating retentive features in dentin in preparation for gold restorations.

• Also used when placing a bevel on enamel margins.

Excavators - SPOON EXCAVATORS

For removing soft carious tissue and carving amalgam or direct wax patterns

CHISELS

Intended primarily for cutting enamel

• Straight, slightly curved or bin-angle

• Enamel hatchets

• Gingival margin trimmers

KINDS OF CHISELS

CHISELS - STRAIGHT, SLIGHTLY CURVED, OR BIN-ANGLE

• Force used is essentially a straight thrust or a pushing motion.

• For bin-angle and Wedelstaedt (slightly curved) chisels.

• Blades w/ distal bevel used to plane a wall that faces the blade’s inside surface.

• Blades w/ mesial bevel used to plane a wall that faces the blade’s outside surface.

CHISELS - STRAIGHT, SLIGHTLY CURVED, OR BIN-ANGLE

CHISELS - ENAMEL HATCHET

Used for cutting enamel and comes as right or left types for use on opposite sides of the preparation.

CHISELS - GINGIVAL MARGIN TRIMMER

Used to eliminate unsupported enamel on gingival walls of proximal preparations.

• Knife

• File

• Discoid-cleoid

OTHER CUTTING INSTRUMENTS - Used for trimming restorative material rather than cutting tooth structure

OTHER CUTTING INSTRUMENTS - KNIVES

• Finishing knives, amalgam knives, or gold knives

• Used for trimming excess restorative material on the gingival, facial, or lingual margins of a proximal restoration.

• Trimming and contouring the surface of a Class V restoration

OTHER CUTTING INSTRUMENTS - FILES

• May also be used to trim excess restorative material and are particularly useful at gingival margins

• Push/pull instrument

OTHER CUTTING INSTRUMENTS - DISCO-CLEOID

1. MODIFIED PEN GRASP

2. INVERTED PEN GRASP

3. PALM-AND-THUMB GRASP

4. MODIFIED PALM-AND-THUMB GRASP

What are the instrument grasp techniques?

MODIFIED PEN GRASP

• Permits the greatest control of the instrument

• The tip of the ring finger is placed on a nearby tooth surface of the same arch as a rest.

INVERTED PEN GRASP

Used mostly for tooth preparations employing the lingual approach on anterior teeth

PALM-AND-THUMB GRASP

Rest is provided by supporting the tip of the thumb on a nearby tooth of the same arch or on a firm, stable structure.

MODIFIED PALM-AND-THUMB GRASP

Usually employed in the area of the maxillary arch and is best adopted when the dentist is operating from a rear-chair position.

RESTS

To steady the hand during operating procedures.

GUARDS

Hand instruments or other items used to protect soft tissue from contact with sharp cutting or abrasive instruments

DENTAL HANDPIECE

Powered rotary cutting instrument

Air-driven and electric motor-driven

2 technologies of dental handpiece:

Low or slow speed

< 12,000 rpm

Medium / intermediate speed

12,000–200,000 rpm

High / ultrahigh speed

200,000 rpm

40,000 rpm

Electric handpiece motors operate up to

• Quieter than air-driven handpieces

• Cut with high torque

• Offer absolute control over rotary instrument revolutions per minute (rpm)

• Offer a single motor with multiple attachments (straight or contra-angle type)

ADVANTAGES OF ELECTRIC HANDPIECES

LOW-SPEED CUTTING

• ineffective, time consuming, and requires a relatively heavy force application

• Heat and vibration are the main sources of patient discomfort

  • For cleaning teeth, caries excavation, and finishing and polishing procedures.

HEAT AND VIBRATION

• are the main sources of patient discomfort

  • For cleaning teeth, caries excavation, and finishing and polishing procedures.

• Diamond and carbide cutting instruments remove tooth structure faster and with less pressure, vibration, and heat generation

• Types of rotary cutting instruments needed is reduced because smaller sizes are more universal

• Better control and greater ease of operation

• Instruments last longer

• Patients less apprehensive

• Increased operation efficiency

ADVANTAGES OF HIGH RPM

LASER EQUIPMENT

• A crystal or gas is excited to emit photons of a characteristic wavelength that are amplified and filtered to make a coherent light beam.

AIR-ABRASIVE CUTTING

• Not generally accepted for tooth preparation

• Only helpful for stain removal, debriding pits and fissures before sealing, and micromechanical roughening of surfaces to be bonded.

Shank, Neck, and Head

Parts of a dental bur/instrument

Shank –

the part that fits into the handpiece

Neck –

connects the head to the shank

Head –

the working part of the instrument

• Head size

• Head shape

• Bladed/abrasive (dental burs and diamond abrasive instruments)

HEAD DESIGN CLASSIFICATIONS:

BURS

All rotary cutting instruments with bladed cutting heads

• Used for:
  → Tooth preparation
  → Finishing metal restorations
  → Surgical removal of bone

ROUND BUR

INVERTED CONE

PEAR-SHAPED

STRAIGHT FISSURE

TAPERED FISSURE

ROUND BUR

Used for initial entry into the tooth, extension of preparation, preparation of retention features, and caries removal.

INVERTED CONE BUR

Used to provide undercuts in tooth preparations.

PEAR-SHAPED BUR

Used for tooth preparations for amalgam.

STRAIGHT FISSURE BUR

Advocated by some dentists for amalgam tooth preparation.

TAPERED FISSURE BUR

Used for tooth preparations for indirect restorations where freedom from undercuts is essential.

FLUTES

Depressed areas located between the blades of a bur.

Number of Bur Blades

Always even in number.

Excavating (Cutting) Bur Blades

Usually 6, 8, or 10 blades.

Ranges from 12 to 40 blades.

Finishing Bur Blades

The bur head should be as symmetrical as possible.

Bur Head Symmetry

Bur Head Characteristics

Measured using concentricity and runout.

CONCENTRICITY

A direct measurement of the symmetry of the bur head itself.

Concentricity Significance

Indicates whether one blade is longer or shorter than the others and is a static measurement.

RUNOUT

A dynamic test measuring the accuracy with which the center of rotation passes through the center of the bur head. The more significant term clinically and the primary cause of vibration during cutting.