15 pptx - د. فاضل

Instruments in Operative Dentistry

1
معالجة نظري / ثالث اسنان كركوك
د.فاضل
2017/5/3
616

Outline:

Hand Instruments
Introduction
Classification
Materials
Application
Techniques
Sharpening

Powered cutting equipments
Rotary cutting instruments
Cutting Mechanism
Hazards

Introduction:

G.V. Black
Nomenclature & numbering of hand instruments
• Cutting instruments/ excavators
• Noncutting

Designs of some early hand instruments

1728 – Pierre Fauchard invented the bow drill
1891 – Edward C Acheson –produced carborundum tools
1935 – W H Drendes - Diamond cutting instruments
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Materials

Carbon Steel:
Harder than stainless steel
Maintained better sharpness
Corrode in moist conditions

Carbon steel

Stainless Steel

Preferred materials
Remains bright under most conditions
Loses keen edge during use much more quickly
Chromium: corrosion resistance
Carbon: hardness

Stainless Steel

Tungsten carbide

Inserts or blades to provide more durable cutting edges (brittle).

They may be soldered to steel handles

Some instruments are made with carbide to provide more durable cutting edges.

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Other alloys of nickel, cobalt, or chromium are used in the manufacture of hand instruments.

They are restricted to instruments other than those for cutting tooth structure

Hardening and Tempering Heat Treatments

Heat treatment Furnace

The hardening heat treatment hardens the alloy, but it also makes it brittle, especially when the carbon content is high.

Tempering heat treatment relieves strains and increases toughness.

Classification of Instruments:- by Sturdevant

Order

Purpose of the instrument
E.g. Excavator, scaler
Sub-order
Manner of use
E.g. Push, Pull
Class
Form of blade
E.g. Hatchet, Chisel
Angle
Number of angles in the shank: monoangle, biangle, triple-angle, quadrangle
E.g. Biangled hatchet excavator,

According to G. V. Black
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Classification of Instruments:- by Charbeneau

Cutting instruments
Hand- hoes, chiesel etc
Rotary- burs, discs etc
Condensing instruments
Pluggers
Plastic instruments
Carvers, Burnishers
Finishing and polishing instruments
Discs, Strips
Isolation instruments
Cotton roll, Rubber dam
Miscellaneous-
Mirrors, Explorers
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CLASSIFICATION BY MARZOUK

EXPLORING
INSTRUMENTS
REMOVAL OF
TOOTH STRUCTURE
RESTORATION
OF TEETH

To dry

To illuminate

Retraction

Probes

Separators

Mixing

Plastic

Condensing

Burnishing

Carvers

Files

Knives

Finishing
& polishing

Hand cutting

Rotary cutting
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Design

Blade

Working part of the instrument
Usually in the form of a bevel (acute angle) that cuts into the tooth structure.
On non cutting instruments e.g. condensers the part corresponding to the blade is called the nib or face.

Shank

Connect the handle to the working end of the instrument.

Normally smooth, round and tapered.

Mon-angle, bin-angle, triple angle
Balance is accomplished by designing the angle of the shank so that the cutting edge of the blade must not be off axis by more than 1-2 mm (Sturdevant’s)/2-3 mm (Summitt)

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Balance allows for the concentration of force onto the blade without causing rotation of the instrument.

Instruments with long blades may required two or three angles in the shank to bring the cutting edge near to the long axis of the handle
Such shanks are termed contra angled.

Handle/ Shaft

Serrated for better gripping and control of the instrument.

• Standard Stainless steel handle: Diameter 6.4 mm approx.

• Padded handles: Diameter 8mm approx.
• Larger diameter handles: 9.5 mm

Handles are in conjunction with the shank or it may be separable.

Separate type is known as cone-socket handle and allows for replacement of several working ends e.g. mirrors and condensers.

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cone-socket handle (mirror)

mirror
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Numeric formulas

Describing the dimensions and angle of the working end.

Three number formula

Four number formula:
Cutting edge is not perpendicular to the long axis of the blade.
Gingival marginal trimmer
Angle former

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Instrument shank and

blade design
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Bevels

Most hand cutting instruments have on the end of the blade a single bevel that forms the primary cutting edge.
Additional two secondary cutting edges that extend from the primary cutting edge for the length of the blade.
Allows cutting in 3 directions; facial and lingual walls of the proximal cavity

Bibeveled instrument have two bevels that form the cutting edge;

e.g. hatched excavator

Single beveled instrument such as spoon excavator and gingival margin trimmer are used with lateral cutting movement.

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Enamel hatchet also as a single beveled instrument used with direct cutting motion, a planning or lateral cutting designated for right (R) and left (L) to the instrument formula.

The cutting edge is perpendicular to the axis of the handle

e.g. binangle chisel.

Instrument with slight blade curvature e.g.Wedelstaedt chisel.

Removal of caries and refinement of the internal parts of the preparation.

Used primarily for cutting enamel.
Cutting instrument applications
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Excavators

• Ordinary Hatchets
• Hoes
• Angle formers
• Spoons
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Ordinary Hatchets

It has the cutting edge of the blade directed
In the same plane as that of the long axis of the handle and
Is bibeveled.

Used primarily on anterior teeth for

Preparing retentive areas and
Sharpening internal line angles, particularly in preparations for direct gold restorations .

Hoe excavators

Primary cutting edge of the blade perpendicular to the axis of the handle
Planing tooth preparation walls and forming line angles.
It is commonly used in Classes III and V preparations for direct gold restorations.

Hoes with longer and heavier blades, with the shanks contra-angled.

For use on enamel or posterior teeth.

The blade angle of the hoe: > 12.5 centigrades

The blade angle of chisel: ≤ 12.5 centigrades
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Angle former

It is mon-angled and has the primary cutting edge at an angle (other than 90 degrees) to the blade.

It is available in pairs (right and left )

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Used primarily for sharpening line and point angles and creating retentive features in dentin in preparation for gold restorations

Also may be used in placing a bevel on enamel margins

Spoon excavators
Its blades are slightly curved, the shanks may be bin-angled or triple-angled to facilitate accessibility.

The cutting edges are circular

The cutting edges are claw like.
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Left cutting and right cutting

Used mainly for removal of caries and refinement of internal opening in a cavity preparation
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bin-angled spoon

triple-angled spoon
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Cleoid spoon

Discoid spoon

Discoid is disc shaped, with cutting edge around the blade
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Chisels:

Straight, Monoangle, Biangle, Wedelstaedt chisels

Enamel Hatchets

Gingival Marginal Trimmers
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Straight Chisel
The straight chisel has a straight shank and blade, with the bevel on only one side.
Its primary edge is perpendicular to the axis of the handle.

(12-7-0)

The shank and blade of the chisel also may be slightly curved (Wedelstaedt design)

11½-15-3

Biangled chisel

Force used with chisels : straight thrust

The bin-angle and Wedelstaedt chisels:

Primary cutting edges in a plane perpendicular to the axis of the handle.

Distal bevel or a mesial (reverse) bevel.

Used for cleaving undermined enamel and for shaping walls.

Instrument with three cutting motion: vertical, right and left.

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The blade with a distal bevel is designed to plane a wall that faces the blade's inside surface

The blade with a mesial bevel is designed to plane a wall that faces the blade's outside surface

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Enamel Hatchet

It is a chisel similar in design to the ordinary hatchet excavator except that the blade is larger, heavier, and is beveled on only one side
Cutting enamel
Right or Left cutting ends of the double- ended hatchet.

10-7-14

Gingival margin trimmer

Blade is curved
Bevel for cutting edge: outside of the curve
Face of instrument: inside of the curve
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12½-100-7-14

12½-75-7-14
Mesial
Distal
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Cutting edge angle: 100 and 75 :
Inlay & Onlay preparations.

Cutting edge angle: 90 and 85 :

Amalgam preparations.
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Uses:

Beveling of the gingival margins of proximo-occlusal preparations.
Beveling of the axio-pulpal line angle
Performing a gingival lock (reverse bevel), placed on the gingival seat

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Usage of hand cutting instruments

Horizontal strokes:
Long axis of blade directed between 45 & 90 degree to the surface being planed or scraped
Vertical or chopping strokes:
Pulling stroke
Hoe: beveled end or distal bevel
Pushing stroke
Hoe: contrabeveled end or mesial bevel.
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The cutting edge of the hand instrument should always be kept sharp as

Dull instruments may cause:

1. Loss of control.
2. More pain.
3. Prolonged time for the operative procedure.
4. Reduce the quality and precision of tooth
preparation.
Sharpening
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sharpening equipment

Stationary sharpening stone e.g. Arkansas stone, silicon carbide.

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Mechanical sharpener; moves at low speed while the instrument is held at the opposite angle and supported by a rest i.e. easier and less time consuming.
E.g. Rx Honing Machine

Mechanical sharpener
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Principles of Sharpening

Sharpen instruments only after they have been cleaned & sterilized
Establish the proper bevel angle (usually 45 degree) and the desired angle of the cutting edge to the blade.
Use light stroke pressure
Use a rest or guide whenever possible.
Remove as little metal as possible

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Non cutting Instruments

Diagnostic instruments
Mirror
Probe or explorer
Twizzer
Plastic instruments
Amalgam instruments
Condensers
Burnisher
Carver
Amalgam carrier
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Mouth Mirror
Most common sizes used are the No. 4 (⅞ inch diameter) and No. 5. (15/16 inch diameter)
No. 2 (5/8 inch diameter): when working on posterior teeth with a rubber dam.
For clarity, reflective surface on the external surface of the glass: Front surface mirror.

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Uses for the mouth mirror. A, Indirect vision. B, Light reflection. C, Retraction. D, Tissue protection.

A
D
C
B
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Explorers
To feel tooth surface for irregularities
To determine the hardness of exposed dentin
• Shepherd’s hook: No. 23
• Cowhorn explorer: No. 2
• No. 17: back action

Tweezer/ cotton forceps:

Cotton forceps are used for picking up small items, cotton pellets

Plastic filling Instruments

To carry and shape tooth colored restorative material: Composite resin and glass ionomer
For placing of base and lining material
Hard plastic or metal.

Composite placement instrument

Designed specifically for the placement of composite restorative materials.
Anodized aluminum
Teflon
Titanium nitride layer on instruments

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A: ash49 B:ash6 C:dycal applicator D:cement spatula.

Amalgam Carriers
An instrument with a hollow cylinder that is filled with amalgam.
Sizes:
Mini: 1.5 mm diameter
Regular: 2.0 mm
Large: 2.5 mm
Jumbo: 3.0-3.5 mm

Amalgam Condensers

Various Amalgam condensers

Carvers

Hand instruments with a blade or nib used to contour the surface of filling material in their plastic state, waxes, models and patterns.
Hollenback carver (knifed edged- elongated- bibevelled)
Diamond (Frahm’s) carver : Bibevelled cutedge.
Ward’s ‘C’ carver
Discoid Cleoid
Interproximal carver

Burnishers

Burnishing of the amalgam on the margins of the cavity,
Shaping metal matrix band to have more desirable contours for restoration.
To bend cast gold restoration (inlay or onlay) near the margin of the prepared cavity to narrow the gap between gold and the tooth.
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Burnishers

Disposable brush

Used with etching and bonding procedures associated with composite resins.

Accessory Instruments

Scissors
Used for cutting dental dam material, retraction cord, and stainless steel crowns.
Crown and bridge scissors

Dappen Dish

Hold certain liquid dental materials during a procedure.

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Howe Pliers

Also referred to as 110 pliers. Useful for holding items, for carrying cotton products to and from the oral cavity, removing the matrix band, and placing and removing the wedge.

Guards

Interproximal wedges to protect soft tissues from contact with sharp rotary cutting instruments.

Preset restorative tray

There are four grasps used with the hand

instruments:

Modified pen.

Inverted pen.

Palm and thumb.

Modified palm and thumb.

Instrument grasp

Modified pen grasp

pen grasp

Modified pen grasp
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Inverted pen grasp

If the hand is rotated so that the palm faces more toward the operator.
Used in the lingual and labial surfaces of anterior teeth.

inverted pen grasp

Palm and thumb grasp

The handle of the instrument is placed on the palm of the hand and grasped by all the fingers while the thumb is free of the instrument and rest on the nearby tooth of the same arch.
Preparing incisal retention in a class III preparation on a maxillary incisor.

Palm and thumb grasp

The same as in palm and thumb grasp but the thumb is rested on the tooth being prepared.
Used in the upper arch.

Powered cutting equipments

Characteristics:

• Speed
• Surface feet per unit time of contact that the tool has with the work to be cut or revolutions per minute
• According to Marzouk:
• Ultra low speed: 300-3000 RPM
• Low speed: 3000-6000 RPM
• Medium High Speed 20,000-45,000 RPM
• High Speed 45,000-1,00,000 RPM
• Ultra High Speed > 1,00,000 RPM
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According to Charbenau:
• Conventional or low speed: below 10,000 RPM
• Increased or high speed: 10,000-1,50,000 RPM
• Ultraspeed: above 1,50,000 RPM
• According to Sturdevant:
• Low or slow speeds: below 12,000 RPM
• Medium/Intermediate speeds: 12,000 to 2,00,000 RPM
• High/ Ultrahigh speeds: above 2,00,000 RPM
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Pressure:

P=F/A
Low speed: 2-5 pounds of force
High speed: 1 pound of force
Ultra high speed: 1-4 ounces of force

Heat Production

Directly proportional to the Pressure, RPM, and area of tooth in contact
113˚ F : Pulpitis & pulp necrosis.
130˚ F : Permanent damage of pulps.

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Brown et al: Temperature of dentin at a distance of 0.5 mm from a high speed bur cutting dry to be 245˚F (118˚C).

Even in non vital teeth, dry cutting at high speed should be avoided, since the thermal stresses will cause microfractures in the enamel. This could contribute to marginal failure of the restoration.

Higher water velocity.

Clean head system

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Greater flow of water coolant is required to prevent clogging when diamonds are used under increased pressure.
42 psi is the optimal air pressure to achieve peak performance

Optic

Drive air
Spray water
Exhaust air
Spray air
Optic
Drive air
Spray water
Exhaust air
Spray air
6-pin
5-hole
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Vibration:

Equipment used & the speed of rotation

Excessive vibration: annoyance to the patient, operator fatigue and rapid wear of instruments.

Torque:

Ability of the hand piece to withstand lateral pressure on the revolving tool without decreasing its speed or reducing its cutting efficiency.
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Friction:

Occurs in the moving parts of the hand piece especially the turbine.

Friction is reduced by equipping the hand piece with ball bearings, needle bearings, glass and resin bearings.

Ceramic Ball Bearings:

40% lighter and 3 times harder than conventional bearings, they offer an extended turbine life, reduced operation noise, and less vibration.

Handpieces:

Two basic types of handpieces, the straight handpiece and contra angle handpiece.

The straight is used more frequently for laboratory work, while contra angle used in the oral cavity.

High speed techniques are generally preferred for cutting enamel and dentin.

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Penetration through enamel and extension of the cavities outline are more efficient at high speed.

Small diameter burs should be used in the high speed handpiece.

High speed generates considerable heat during cutting, even with small diameter burs and should be used with water coolant and high efficiency evacuation
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Design:

This model is the choice for limited access or when treating children.

Rear-facing exhaust vents direct air flow away from the surgical site for patient protection
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Commonly used couplings

Zero Suck Back Technology

Prevents the intake of aerosol and other particles when it is stopped.

Drive air flows into an Anti Suck Back Diffuser (ASBD) within the capsule.

Air in the ASBD is pressurized through centrifugal force created by the impeller rotation.
Through the centrifugal force and rotation of the impeller, air continues to flow into the ASBD and remains pressurized even after drive air is stopped.
The pressurized air in the ASBD is released to the outside at the bottom of the head
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Low-Speed Handpiece

Design
Straight in appearance.
Standard length and “short.”
Speed ranges from 10,000 to 30,000 rotations per minute (rpm).
Operates the rotary instrument in either a forward or backward movement.

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Uses of the low-speed handpiece

Intraoral
Removal of soft decay and fine finishing of a cavity preparation.
Finishing and polishing of restorations.
Coronal polishing and removal of stains.

Extraoral
Trimming and contouring temporary crowns.
Trimming and relining of removable partials and dentures.
Trimming and contouring of orthodontic appliances.

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Low-Speed Attachments

Straight attachment receives a long‑shank laboratory bur, the contra-angle attachment, and the prophy angle attachment.

Contra-angle attachment receives latch type rotary instruments and mandrel.

Prophylaxis Angle

Used during polishing procedures to hold the prophy cup and bristle brush.
Two types
Plastic disposable “prophy” angle
Metal “prophy” angle

High-Speed Handpiece

Design
One-piece unit with a slight curve in appearance.
Operates from air pressure.
Operates at speeds up to 450,000 rpm.
Maintains a water-coolant system.
Friction-grip locking system for rotary instruments.
Fiber-optic lighting.

Cellular Glass Optics

Uses of the high-speed handpiece

Removes decay.
Removes an old or faulty restoration.
Reduces the crown portion of the tooth for the preparation of a crown or bridge.
Prepares the outline and retention grooves for a new restoration.
Finishes or polishes a restoration.
Sections a tooth during a surgery.

Ultrasonic Handpiece

Design
Attached to the dental unit.
Powered by electricity.
Attachments are similar in appearance to scaling instruments.
Delivers a pulsating spray of water.

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Uses of the ultrasonic handpiece

Removes calculus.
Removes stain.
Removes bonding materials from a tooth surface after orthodontic appliances are removed.
Removes cement after orthodontic bands are removed.

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Laser Handpiece
Design

Uses a laser light beam instead of rotary instruments.

The laser is conducted through a fiber‑optic cable.
Resembles a standard handpiece.
Maintains a water-coolant system.
Maintains an air-coolant system
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Uses:

Cauterizes soft tissue.
Vaporizes decayed tooth structure.

Advantages:

Usually painless.
Patient usually does not require anesthesia.
Proceed with procedure faster.

Disadvantage:

Cannot be used on teeth with existing restorations.

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Air-Abrasion Handpiece

Design

Small version of a sandblaster.

Compressed air at pressure of 7 to 11 atm (40 to 140 psi)

Produces a high‑pressure delivery of aluminum oxide particles (of 20 to 50 pm) through a small probe.

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Uses:

Prepares teeth for sealants.

Removes external stains.

Class I through class VI preparations.

Endodontic access.

Crown margins.

Prepares a tooth surface for the cementation of a cast restoration, such as a crown or veneer.

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Disadvantages:

More effective on hard normal dentine than soft dentine affected dentine

When using composite, the air abrasion doesn’t provide the micromechanical roughness needs for retention thus needs acid-etchant.

Loss of tactile sensation.

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Possible iatrogenic damage especially on the cementum and root dentine.

Can induce asthma –> thus needs high volume suction

Can’t remove amalgam restoration.

Can’t perform massive reduction for crown.

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Laboratory Handpiece

Design

Operates at speeds up to 20,000 rpm.

Uses laboratory burs.

Provides greater torque than handpieces used intraorally.

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Rotary instruments

Cutting

Abrasive

Carbide burs

Made from
1- tungsten carbide
2- steel carbide

1- Diamond burs

2- Discs
3- Stones
4- Rubber wheels

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According to composition:

• Steel burs
• Tungsten Carbide burs
• According to mode of attachment to handpiece
• Latch type
• Friction grip type
• According to handpiece they are designed for;
• Clockwise
• Anticlockwise
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Rotary instruments consist of three parts :
1- shank
2- neck (shaft)
3- head

head

shaft
Shank
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Shank design

Long shank – used for straight hand piece (low speed)

Short latch shank – used for contra-angle (low speed)

Friction grip shank - used for high speed hand piece

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113

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Dental Burs

A group of instruments that can turn on an axis with different speed of rotation to perform different types of work.

The characteristics of this work are either cutting , abrasive, finishing or polishing.

Steel burs cut human dentin at low speeds, but dulls rapidly at higher speeds or when cutting enamel

Steel necks bends easily causing vibration

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Carbide burs
Burs possess blades that shear (cut) tooth structure.
They are used for making precise intracoronal preparation features such as placing groove, and boxes.
Used for smoothing surface in enamel and dentin
They are not used for bulk reduction because to producing undulations on the tooth surface

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Shapes:

Round Bur:
Initial entry into the tooth
Extension of the preparation
Retentive features and caries removal
Inverted cone bur
Undercuts in the tooth preparation
Pear shaped bur
Tooth preparation for amalgam, gold foil.
Straight fissure bur
Tooth preparation for amalgam
Tapered fissure bur
Tooth preparation for indirect restorations.
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Basic bur head shapes

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Coarse-cut

Regular –cut

Fine Cut

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Twelve-fluted carbide bur

Its used for highly smoothing of prepared surfaces of tooth

Because of its blades in a diagonal to the instrument shaft

Its have a torpedo shape

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Plain fissure bur

Its tapered and cylinder shape its used for placing groove and boxes and they also used for finishing of preparation.

Groove seating

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Bur numbering systems

In the united states the burs have been traditionally described in term of arbitrary i.e. numerical code
eg, 2 =1 mm diameter round bur,
34 = 0.8mm inverted,
57 = 1mm diameter straight fissure

Number 500 is added to indicate cross cutting

Number 900 is added to indicate end-cutting only

So no. 57 ,557 and 957 are all had the same head size

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Iso system(international standard organization)

FDI (Federation dentaire internationale)

Usually tend to use head shape name and size

(in tenth of a millimeter)

Eg. Round 010 = 1mm diameter

Straight fissure plain 010 = 1mm diameter

Inverted cone 008=0.8mm diameter

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Shapes & diameters of regular carbide burs used for tooth preparation

Round
Bur size: 1/16 1/8 ¼ ½ 1 2 3 4 5 6 7 8 9 11
Diameter: 0.30 0.40 .50 .60 .80 1.0 1.2 1.4 1.6 1.8 2.1 2.3 2.5 3.1
Inverted cone
Bur size: 33½ 34 35 36 37 39 40
Diameter (mm): .6 .8 1.0 1.2 1.4 1.8 2.1
Straight Fissure:
Bur size: 55½ 56 57 58 59 60
Diameter (mm): .60 .80 1.0 1.2 1.4 1.6
Straight fissure, round end:
Bur size: 1156 1157 1158
Diameter (mm): .80 1.0 1.2
Tapered fissure:
Bur size: 168 169 170 171
Diameter (mm): .80 .90 1.0 1.2
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Tapered fissure, rounded end
Bur size: 1169 1170 1171
Diameter (mm): .90 1.0 1.2
Pear:
Bur size: 329 330 331 332
Diameter (mm): .60 .80 1.0 1.2
Long inverted cone, rounded corners (amalgam preparation)
Bur size: 245 246
Diameter (mm): .80 1.2
End-cutting:
Bur size: 956 957
Diameter (mm): .80 1.0
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Bur head design:

The number of blades on a bur is always even

Number of blades on an excavating bur may vary from 6 to 8 t0 10.

Finishing bur: 12 to 40 blades

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Concentricity:

Measurement of the symmetry of the bur head.

Runout:

Test measuring the accuracy with which all blade tips pass through a single point when the instrument is rotated.

Average value of clinically acceptable run-out is about 0.023 mm

Is the primary cause of vibration

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Bur blade design

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Rake angle:

Angle that the face of the bur tooth makes with the radial line.

Radial rake angle: radial line & the tooth face coincide.

Negative rake angle: blade face is leading the radial line

• Increases the life expectancy of the bur & provides for the most effective performance in low and high speed ranges.

Positive rake angle:

Produce acute edge angle

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Edge angle:

In the range of 90˚ to provide strength to the blade & longevity of cutting efficiency of the bur.

Land: plane surface immediately following the cutting edge.

Flute/ Chip space:
Space between successive bur teeth or the blades of the bur.
Provides an exit for removal of the fractured matter and creates a clearance angle.

131

Clearance angle:

Angle between the back of the blade and the tooth surface.

If a land is present on the bur:
• Primary clearance angle: the angle the land will make with work.
• Secondary clearance angle: the angle between the back of the bur tooth and work.
• Radial clearance angle: is formed when the back surface of the bur tooth is curved.
Provides clearance between the work & the cutting edge to prevent the tooth back from rubbing on the work.
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Abrasive instruments

Head consists of small angular particles of hard substance embedded in a soft binder (ceramic, metal, shellac, rubber).
Diamond abrasives
Other abrasives –Silicon carbide (carborundum), aluminium oxide, garnet, quartz, pumice, cuttlebone.

Deposited by Electroplating, sintering or microbrazing.

133

Diamond stones

These are made from diamond chips bonded to blanks (heads). Diamonds used for grinding enamel and dentin surfaces
Diamond burs may divided according to :
1- coarseness ( medium grit - fine grit )
2- shape

Medium grit

Fine grit

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Diamond particle size:

1) Coarse: 125~150 um
2) Medium: 88~125 um
3) Fine: 60~74 um
4) Very fine: 38~44 um
Diamond instruments consists of three parts:
A metal blank,
The powdered diamond abrasive
A metallic bonding material that holds the diamond powder onto the blank
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Color coding:
Coarse: 120-150µ

Standard: 106-125µ

Fine: 53-63µ

Extra- fine: 20-30µ

TF: Taper flat end; TR: Taper round end; TC: Taper conical end; FO: Flame Ogival end; SF: Straight flat end; SO: Straight Ogival end; BR: Ball round; WR: wheel round edge;
Green
Blue
Red
Yellow

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Discs, Mandrel, Stones, and Wheels

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Moulded abrasive instrument –

Manufactured by pressing a uniform mixture of abrasive and matrix around roughened end of shank,
Points and stones; finishing & polishing

Coated abrasive instrument –

Disks that have a thin layer of abrasive cemented to a flexible backing.
surface contouring, finishing

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SmartPrep Instruments

• SmartPrep Instruments (Smart Bur, Polymer Bur)

• Medical polymer that has the ability to remove decayed dentine while keeping the healthy dentin.
• Its hardness is less than healthy dentine while harder than the carious dentin.
• Ability to self-limit(selectively)
It will only cut what is carious and if it’s in contact with healthy dentin the bur will only wear away (when extensive force isn’t used).

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Advantages:

Conservative
Minimal to none disease transfer (because its single use only).
No need for Local Anesthesia.
For Students to start with first clinical cases.
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Disadvantages:

Single-patient-use = Expensive.

Technique sensitive ( too much pressure and you will cut the healthy dentine)

The bur breaks down when it touches enamel.

It can sometimes leave large amounts of decayed tissue (use caries dye to locate the left amount.

Access should be done by a different type of bur that can penetrate the enamel.

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Cutting Mechanisms

Bladed Cutting:
Brittle fracture: crack production, by tensile loading.
High speed cutting, especially of enamel
Ductile fracture: plastic deformation, by shear.
Low speed cutting.

Abrasive Cutting:
Diamonds are most efficient when used to cut brittle materials, are superior to burs for removal of the dental enamel.
Burs are generally preferred for cutting ductile materials such as dentin.

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Cutting Recommendations

Use of contra-angled handpiece, air-water spray for cooling, high operating speed (above 200,000 rpm), light pressure.

Carbide burs are better for end- cutting, produce lower heat, and have more blade edges per diameter for cutting.

Diamonds are more effective than burs for both intracoronal & extracoronal tooth preparations, beveling enamel margins on tooth preparation, & enameloplasty.
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Chemo-Mechanical Caries Removal

Carisolv (Chemo‐mechanical caries removal )
Composition:
0.5% sodium hypochlorite and 0.1 M amino acids “Glutamine, leucine and lycine”
This is a technique used to remove caries and decay with minimal invasive techniques.
Hypochlorite: dissolves the decayed dentine
Amino acid: buffering solution to prevent damage to the healthy tissue.
[The amino acid and hypochlorite will react with the denatured Collagen Tissue of dentine (Infected dentine) making soft and easily removed with hand instruments.]
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Advantages:

Less anesthesia is used

Useful for children, dental‐phobic patients.
Useful for removing root or coronal caries in easily accessible areas.
Removes the smear layer and doesn’t affect the bond strength of the adhesive materials.
No histological effect on the pulp even with direct contact.

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Ozone treatment

Ozone gas has a high oxidation potential and is effective against bacteria, viruses, fungi, and protozoa.

Capacity to stimulate blood circulation, platelets, and immune response.

Ozone is used in dentistry in gaseous, ozonated water and as ozonated oils

Ozone has been proven to halt root caries and also reverse lesions (pit and fissure carious lesions) by allowing the natural remineralisation process to proceed.

Remineralised lesions are known to be more resistant to further dissolution than sound tooth surfaces.
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Disruption of the protected ecological niche of the micro-flora allows remineralisation from the saliva.

Intracanal irrigants in endodontic treatment.

Treatment of alveolitis, avascular osteonecrosis of the jaw, and herpes virus infection.

Inhibits plaque formation: periodontal surgical and maintenance phase.

Used in dental unit water line to disinfect water.

Advantage of ozone therapy is it is an atraumatic, biologically based treatment.

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O3 delivered from the HealOzone unit: (2100 ppm O3, 615 ml/min) through a hand piece with a silicone cup that sealed the tooth.

Once sealed, the device automatically delivered the O3 for the treatment group for 10 seconds followed by 10 seconds vacuum.

Recall:

After one and three months.

Prophylaxis of teeth
Re-examination using the DIAGNOdent® and ECM readings.
Ozone treatment repeat on each of these two recall visits.
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Hazards with cutting Instruments

Pulpal Precautions:

Mechanical vibration, heat, desiccation, loss of dentinal tubule fluid, and or transection of odontoblastic processes.

Pulpal sequelae (recovery or necrosis) take from 2 weeks to 6 months or longer, depending upon extent and degree of trauma.
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The remaining tissue is effective in protecting the pulp in proportion to the square of its thickness.

Steel burs produce more heat than carbide burs because of inefficient cutting.

Dull instruments will plug debris, do not cut efficiently and result in heat production.

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When used without coolants, diamond instruments generate more damaging heat than carbide burs.

Air alone as coolant: much lower heat capacity than water, desiccates dentin, damage odontoblasts.

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Soft tissue precautions:

Lips, tongue and cheeks of the patient.

Good access and visibility.

Isolation of the operating site: rubber dam, retraction type saliva ejector tip.

Wait for the instrument to stop or extremely careful while removing the handpiece from the mouth.

Large disc

Sudden reflex by the patients.

Hand excavators: soft caries removal in the deep preparation may lead to mechanical pulp exposure: round bur at low speed.

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Eye Precautions

Airborne particles, old restorations, tooth structure, bacteria, debris.
Strong high volume evacuation.

Ear Precautions:

Loud noise: mental and physical distress, increase accident proneness, reduce overall eficiency.
Noise level in excess of 75 db, 1000 to 8000 cps(frequency) may cause hearing damage.
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Inhalation Precautions

Amalgams or composites produce submicron particles and vapor.

Alveolar irritation and tissue reactions.

During cutting or polishing: thermal decomposition of polymeric restorative materials (sealants, acrylic resins, composites) : Monomers.

Mask : do not filter either mercury or monomer vapors
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Conclusion:

The removal and shaping of the tooth structure are essential aspects of restorative dentistry. Modern high speed instruments has eliminated the need of many hand instruments, but hand cutting instruments are still important for finishing many tooth preparations and thus they remain as an essential part of the armamentarium for quality restorative dentistry.
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References:

• Sturdevant’s Art & Science of Operative Dentistry :4th edition
• Fundamentals of Operative Dentistry; James B. Summitt; 3rd edition.
• Operative Dentistry of Modern Theory and Practice: M K Marzouk
• Black GV. A work on Operative Dentistry. Chicago: Medico-Dental Publishing, 1908
• Dental Hand Instruments, 2003: Elsevier Science (USA). ISBN 0-7216-9770-4
• Fundamentals of Tooth Preparation: Shillingburg
• Journal of Interdisciplinary Dentistry / Jul-Dec 2011 / Vol-1 / Issue-2
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