Operative Instruments

Instruments in Operative Dentistry

Dr. Ashok AyerAssistant ProfessorDepartment of Conservative Dentistry and EndodonticsCollege of Dental SurgeryB. P. Koirala Institute of Health Sciences, Dharan, Nepal

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 instrumentsCutting instruments/ excavatorsNoncutting

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

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.

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 FurnaceThe 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

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

CLASSIFICATION BY MARZOUK

EXPLORING INSTRUMENTSREMOVAL OF TOOTH STRUCTURERESTORATION OF TEETHTo dryTo illuminateRetractionProbesSeparators

MixingPlasticCondensingBurnishing CarversFilesKnivesFinishing & polishing

Hand cuttingRotary cutting

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.

ShankConnect the handle to the working end of the instrument.

Normally smooth, round and tapered.Mon-angle, bin-angle, triple angleBalance 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 (Sturdevants)/2-3 mm (Summitt)

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 handleSuch 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 mmMore ergonomicLess likely to develop carpal tunnel syndromeOccupy more space in instrument tray

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.

cone-socket handle (mirror)

mirror

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

Instrument shank and blade design 85

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.

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

27written and designed by - Ahmed Maky

ExcavatorsOrdinary HatchetsHoesAngle formersSpoons

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

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 )

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 excavatorsIts 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.

Left cutting and right cutting Used mainly for removal of caries and refinement of internal opening in a cavity preparation

bin-angled spoon triple-angled spoon

38written and designed by - Ahmed Maky

Cleoid spoon

39written and designed by - Ahmed Maky

Discoid spoon Discoid is disc shaped, with cutting edge around the blade

40written and designed by - Ahmed Maky

Chisels: Straight, Monoangle, Biangle, Wedelstaedt chisels

Enamel Hatchets

Gingival Marginal Trimmers

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)

11-15-3

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.

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

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

12-100-7-1412-75-7-14MesialDistal

Cutting edge angle: 100 and 75 : Inlay & Onlay preparations.

Cutting edge angle: 90 and 85 : Amalgam preparations.

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

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.

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

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

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

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

Non cutting InstrumentsDiagnostic instrumentsMirrorProbe or explorerTwizzerPlastic instrumentsAmalgam instrumentsCondensersBurnisherCarverAmalgam carrier

Mouth MirrorMost common sizes used are the No. 4 ( 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.

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

ADCB

5858What are the indirect areas of a patients mouth for the right-handed operator? Light reflection/reflective illumination: directs additional light into areas of the mouth. Retraction: helps maintain a clear field and protects the soft tissues from injury caused by the dental bur or hand instruments. What is another function of the dental mirror?

ExplorersTo feel tooth surface for irregularitiesTo determine the hardness of exposed dentinShepherds hook: No. 23Cowhorn explorer: No. 2No. 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

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

Amalgam CarriersAn instrument with a hollow cylinder that is filled with amalgam.Sizes:Mini: 1.5 mm diameterRegular: 2.0 mmLarge: 2.5 mmJumbo: 3.0-3.5 mm

Amalgam Condensers

Various Amalgam condensers

CarversHand 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 (Frahms) carver : Bibevelled cutedge.Wards C carverDiscoid CleoidInterproximal carver

BurnishersBurnishing 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.

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.

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 handinstruments:

Modified pen.

Inverted pen.

Palm and thumb.

Modified palm and thumb.

Instrument grasp

Modified pen grasp

pen graspModified pen grasp

Inverted pen graspIf 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 graspThe 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 graspThe 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:

SpeedSurface feet per unit time of contact that the tool has with the work to be cut or revolutions per minuteAccording to Marzouk:Ultra low speed:300-3000 RPMLow speed:3000-6000 RPMMedium High Speed20,000-45,000 RPMHigh Speed45,000-1,00,000 RPMUltra High Speed> 1,00,000 RPM

According to Charbenau:Conventional or low speed: below 10,000 RPMIncreased or high speed: 10,000-1,50,000 RPMUltraspeed: above 1,50,000 RPM

According to Sturdevant:Low or slow speeds: below 12,000 RPMMedium/Intermediate speeds: 12,000 to 2,00,000 RPMHigh/ Ultrahigh speeds: above 2,00,000 RPM

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.

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

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

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

OpticDrive airSpray waterExhaust airSpray airOpticDrive airSpray waterExhaust airSpray air6-pin5-hole

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.

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.

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

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

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

Low-Speed Handpiece

DesignStraight 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.

Uses of the low-speed handpiece IntraoralRemoval of soft decay and fine finishing of a cavity preparation.Finishing and polishing of restorations.Coronal polishing and removal of stains.

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

Low-Speed Attachments

Straight attachment receives a longshank 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 typesPlastic disposable prophy angleMetal prophy angle

High-Speed Handpiece

DesignOne-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

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

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.

Laser Handpiece

Design

Uses a laser light beam instead of rotary instruments.The laser is conducted through a fiberoptic cable. Resembles a standard handpiece.Maintains a water-coolant system.Maintains an air-coolant system

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.

Air-Abrasion Handpiece

Design

Small version of a sandblaster.

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

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

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.

Disadvantages:

More effective on hard normal dentine than soft dentine affected dentine

When using composite, the air abrasion doesnt provide the micromechanical roughness needs for retention thus needs acid-etchant.

Loss of tactile sensation.

Possible iatrogenic damage especially on the cementum and root dentine.

Can induce asthma > thus needs high volume suction

Cant remove amalgam restoration.

Cant perform massive reduction for crown.

Laboratory Handpiece Design

Operates at speeds up to 20,000 rpm.

Uses laboratory burs.

Provides greater torque than handpieces used intraorally.

Rotary instruments

Cutting

Abrasive

Carbide burs

Made from 1- tungsten carbide 2- steel carbide

1- Diamond burs2- Discs3- Stones4- Rubber wheels

According to composition:Steel bursTungsten Carbide burs

According to mode of attachment to handpieceLatch typeFriction grip type

According to handpiece they are designed for;ClockwiseAnticlockwise

Rotary instruments consist of three parts :1- shank 2- neck (shaft) 3- head

headshaftShank

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

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

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

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.

Basic bur head shapes

Regular cut

Fine Cut

Coarse-cut

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 Twelve-fluted carbide bur

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

Groove seating

Bur numbering systems

In the united states the burs have been traditionally described in term of arbitrary i.e. numerical codeeg, 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

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

Shapes & diameters of regular carbide burs used for tooth preparation Round Bur size: 1/16 1/8 1 2 3 4 5 6 7 8 9 11Diameter: 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 coneBur size: 33 34 35 36 37 39 40Diameter (mm): .6 .8 1.0 1.2 1.4 1.8 2.1 Straight Fissure:Bur size: 55 56 57 58 59 60Diameter (mm): .60 .80 1.0 1.2 1.4 1.6Straight fissure, round end:Bur size:115611571158Diameter (mm):.801.01.2Tapered fissure:Bur size:168169170171Diameter (mm):.80.901.01.2

Tapered fissure, rounded endBur size: 116911701171Diameter (mm):.901.01.2 Pear:Bur size:329330331332Diameter (mm):.60.801.01.2 Long inverted cone, rounded corners (amalgam preparation)Bur size:245246Diameter (mm):.801.2 End-cutting:Bur size:956957Diameter (mm):.801.0

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

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

Bur blade design

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 lineIncreases 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

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.

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.

Abrasive instrumentsHead consists of small angular particles ofhard substance embedded in a soft binder (ceramic, metal, shellac, rubber).Diamond abrasivesOther abrasives Silicon carbide (carborundum), aluminium oxide, garnet, quartz, pumice, cuttlebone.

Deposited by Electroplating, sintering or microbrazing.

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- shapeDiamond stones

Medium grit

Fine grit

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

Color coding:Coarse: 120-150

Standard: 106-125

Fine: 53-63

Extra- fine: 20-30

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;GreenBlueRedYellow

Discs, Mandrel, Stones, and Wheels

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

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 its in contact with healthy dentin the bur will only wear away (when extensive force isnt used).

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.

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.

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.

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.

Chemo-Mechanical Caries Removal

Carisolv (Chemomechanical 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 dentineAmino 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.]

Advantages:

Less anesthesia is usedUseful for children, dentalphobic patients.Useful for removing root or coronal caries in easily accessible areas.Removes the smear layer and doesnt affect the bond strength of the adhesive materials.No histological effect on the pulp even with direct contact.

Ozone treatmentOzone 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.

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.

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.

Hazards with cutting InstrumentsPulpal 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.

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.

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.

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.

Eye PrecautionsAirborne 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.

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

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.

References:Sturdevants Art & Science of Operative Dentistry :4th editionFundamentals of Operative Dentistry; James B. Summitt; 3rd edition.Operative Dentistry of Modern Theory and Practice: M K MarzoukBlack GV. A work on Operative Dentistry. Chicago: Medico-Dental Publishing, 1908Dental 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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