Instruments and instrumentation

used in operative dentistry I

dr.Abdulaziz N Maher

General Classification of Instruments

The standardization of the design of cutting instruments by the manufacturer has been helpful to the practitioners.

All instruments are identified by a nomenclature and a number that describe the size, design and common clinical usages.

The general classification of instruments used in restorative dentistry according to their use includes;

1. instruments used for cutting tooth substance:

a. Hand cutting instruments;

chisels, hatchets, excavators, angle formers, marginal trimmers.

b. Rotary tools;

burs, different abrasives in the form of stones, discs.

2. Plastic filling instruments:

( used in manipulating, packing, condensation and carving plastic filling materials).

Mixing spatulas, Carvers, Burnishers, Hand and Mechanical condenser.

3. Finishing and polishing instruments:

(used to refine, smoothen, finish and polish all restorative materials).

a. Hand: polishing points, finishing strips.

b. Rotary: finishing burs, mounted stones and brushes, impregnated strips and rubber cups.

4. Instruments used for isolation of the working area:

Rubber dam equipments (punch, holder, clamps) saliva ejectors, cotton roll and roll holders, evacuating tips and equipments.

5. Miscellaneous instruments: (used mainly to diagnosis and assess carious lesion together with other variable purposes)

Mouth mirrors, Probes and Explorers, Tweezers.

Examination Kit or diagnostic kitExamination Kit or diagnostic kit

Moth mirrorProvide indirect vision .

Retract lips, cheeks and Tongue.

Reflect light into mouth.

ExplorerExamine tooth for decay, calculus, furcation and abnormalities.

Cotton forceps (Pliers)Grasp materials and/or transfer it into or out of oral cavity.

Periodontal probeMeasure depth of periodontal pockets .

Hand Instruments

I. definition: hand instruments were originally used to differentiate between hand cutting instruments and motorized hand-pieces used for cavity preparation.

II. Hand instruments are used for:

a. Examination and charting.

b. Removal of decay.

c. Refining preparations

d. Placement of filling materials.

e. Carving and finishing materials.

f. Burnishing metals.

III. Your operative instrument cassette (tray) must contain several types of instruments of that you will need in the course:

a. Instrument for examination.

b. Excavators for removing decay.

c. Cutting instruments for finishing walls.

d. Amalgam condensers for placement of silver alloy restorations.

e. Plastic filling instruments for placing pliable materials.

f. Burnishing instruments for adapting metal.

IV. Hand instruments are composed of three parts:

a. Hand or shaft: The part grasped in the operator’s hand, usually straight and without variations in size, it smooth knurled and / or serrated to allow for better instrument control.

b. Shank: It begin with the first twisted portion of the shaft and ends where the blade or nib begins. It may be straight, single, double or triple angled. It tapers smoothly from the shaft to the blade.

c. Blade or Nib: The working part of the instrument, begin at last angle, which terminates the shank.

V. Black’s Formula ( instrument formula ):

a. Three number formulas;

1. the first number indicated the width of the cutting of the blade in tenths of a millimeter.

2. the second number is indicated the length of the cutting blade in millimeter.

3. the third number is indicated the angle that the blade makes with the long axis of the handle in degree centigrade or hundredths of a circle.

b. four number formulas;

1. the first number indicated the width of the cutting of the blade in tenths of a millimeter.

2. the second number indicated the angle of cutting edge makes with the handle in degree centigrade.

3. the third number is indicated the length of the cutting blade in millimeter.

4. the fourth number is indicated the angle that the blade makes

with the long axis of the handle in degree centigrade or hundredths

of a circle.

VI. Instrument Sharpening :

For efficient use, hand-cutting instrument must be maintained in a sharpened state.

There are tow methods for sharpening hand instruments:

a. Mechanical sharpening

b. Hand sharpening

Mechanical sharpening; such as electric sharpeners are more efficient, but tend to wear the cutting blades through excessive sharpening. The same is true with mounted sharpening stones designed for dental hand-pieces and laboratory lathes.

Hand sharpening; is somewhat slower, but offers more control. In addition, hand sharpening can be done chair side as needed. This required sterilization of the stones after each clinical use. Most sharpening stones required the use of a lubricant for efficient use and maintenance.

Black's classification systems categorized instruments by :

(1) The purpose of use or Function (e.g., scaler, excavator), (2) The position or Manner of use (e.g., hand condenser), (3) The form of or Design of working end (e.g., spoon excavator, sickle scaler)(4) The angles or Shape of shank (e.g., mon-angle, bin-angle, contra-angle).

These names were combined to form the complete description of instrument (e.g., bin-angle spoon excavator).

VII. Instruments Nomenclature (Instrument Names): Black classified all instruments by name. In addition, for hand

cutting instruments, he developed numeric formula to characterize the dimensions and angles of working end.

VIII. Factors Affecting Working Efficiency of hand instruments:

1. contra-angling:

a. To facilitate access to different areas of teeth.

b. To get out of balance and rotate readily in the operator’s hand on application of force.

c. To prevent instrument imbalance or eccentricity.

d. To determines the inaccessibility cavity.

StraightMon-angled (one) Bin-angled (two) Triple-angled (three)Quadra-angled (four)

2. Beveling:

Hand cutting instruments, usually the blade is beveled on the right or left side, so it’s called right or left instruments, if beveled both side called bi-beveled.

These designs facilitate the development of more conservative preparations and allow use of the edge of the cutting blade in many situations.

If beveled is placed on the distal or mesial aspect of blade relative to the shaft, the instrument called a contra or reversely or directly beveled like a Curved (Wedelstaedt)

3. Direct and lateral cutting instruments.

4. Right and left cutting instruments.

5. Single ended or double ended.

6. Material and design;

a. stainless steel instruments incorporating carbon and chromium give improved corrosion resistance, brightness and hardness.(Material)

b. Thinner cross section of the cutting edge more concentrated the pressure (force) more efficient the instrument will be.(Design)

IX. Types of hand cutting instruments;a. Chisels : used primarily for cutting enamel

surface.b.Excavators: Used for removal of caries and

refinement of internal parts of preparation.

1.ChiselsIntended for cutting enamel.

Grouped as:

(a) Straight, Slightly curved, or Bin-angle

the bevel on only one side.

primary edge is perpendicular to axis of the handle.

may be slightly curved (Wedelstaedt design) or bin-angled .

(b) Enamel hatchets

Is a chisel similar in design to ordinary hatchet except blade is larger, heavier and beveled on one side.

Cutting edges in a plane that is parallel with the axis of the handle.

1.Chisels

Enamel Hatchet

Gingival margin trimmer

Gingival margin trimmer

1.chisels

Straight

Wedelstaedt

Bin-angle

1. Chisels(c) Gingival margin trimmersDesigned to produce proper bevel on gingival enamel margins of

proximo-occlusal preparations and rounding or beveling axiopulpal line angle of two-surface preparations.

Similar in design to the enamel hatchet, except the blade is curved.

Primary cutting edge is at an angle to axis of blade .

2.Excavators

Ordinary hatchet excavator :

Cutting edge of blade directed in the same plane as long axis of handle and is bi-beveled .

Used on anterior teeth for preparing retentive areas and sharpening internal line angles.

Hoe excavator :

Has the primary cutting edge of blade perpendicular to axis of handle . Used for planning tooth preparation walls and forming line angles. Commonly used in classes III and V preparations for restorations.

2.Excavators

hatchet

Hoe

Angle former

Spoons excavators

Binangle spoon

triple-angle spoon

spoon

2.Excavators

Angle former

Mon-angled and has primary cutting edge at angle (other than 90O) to blade.

Used primarily for :Sharpening line angles and creating retentive features in dentin in

preparation for restorations.

Placing bevel on enamel margins.

2.Excavators

Spoon excavators

Used for removing caries and carving amalgam or direct wax patterns.

Blades are slightly curved and cutting edges are either circular or clawlike.

Circular edge is known as a discoid, whereas the clawlike blade is termed cleoid .

Shanks may be bin-angled or triple-angled to facilitate accessibility.

Discoid-cleoid

used for carving occlusal anatomy in unset amalgam

restorations. It also may be used to trim or burnish inlay - onlay margins.

X. instruments grasps:a. For instrument to be used efficiently it must be handled

properly.

b. In patient mouth hands or fingers of the operator should be firmly braced against hard tissues ( teeth or jaws not cheek ).

c. Instrument movement are more controlled if the bracing point is as close to the actual operating site.

d. Maxillary teeth provide better support than mandibular ( no movable joint ).

e. To accomplish bracing one can use two hands than one.

Hand instrument techniques

4 Grasps used with hand instruments:

• (1) Pen grasp.

• (2) Inverted pen grasp .

• (3) Palm & Thumb grasp .

• (4) Modified Palm & Thumb grasp .

Pen Grasp

• Pads of thumb, index, and middle fingers contact instrument(shaft), while tip of ring finger and little finger is placed on a nearby tooth surface of the same arch as rest. Used when direct vision is possible.

Inverted Pen Grasp

• Hand is rotated so that Palm faces more toward operator .

• Used mostly for tooth preparations utilizing palatal approach on anterior teeth. That facing upwards (indirect vision) upper teeth.

Palm & Thumb Grasp • Handle is placed in the palm and grasped by all fingers, while thumb is

free of instrument and rest is provided by supporting tip of thumb on nearby tooth of same arch or on firm, stable structure.(direct vision)

• Used for cutting incisal retention for Class III preparation on incisors in labial, buccal and class I or II in occlusal surfaces) .

• Used when need more force

Modified Palm & Thumb Grasp

• Handle of instrument is held by all four fingers whose pads press handle against distal area of palm, as well as pad and first joint of thumb.

• Used in area of maxillary arch and is best adopted when the dentist is operating from near-chair position. (Used indirect vision)

• Hand is only half closed.• End of the thumb is used for rest.• Give greater freedom and ease movements.

X. Rest and Guard

Rest ;

1. Finger not used to grasp instrument support and stabilize the working hand.

2. Should always be on firm tissue of teeth.

3. Ideally rest on teeth adjacent to the one being operated.

4. In pen grasp rest is achieved by the 2 small finger.

5. In palm grasp rest is achieved by the thumb.

X. Rest and Guard

Guard ;

1. It is the finger position of the opposite hand to steady the operating area and to protect from injury in case of accidental slipping of instrument.

2. Usually guard position: the thumb on one side of the tooth under work and the first or second finger on the opposite side.

Thank you for your attention!