Submitted by:Dr.Pallavi Chavan

Iyr PG

Rotary instruments in Prosthodontics

Introduction

The removal and shaping of tooth structure is an essential part of restorative and prosthetic dentistry

Initially this was a difficult process accomplished entirely by the use of hand instruments.

The introduction of rotary equipments, is one of the truly major advances in dentistry.

Evolution of rotary cutting instruments1800’s (300-1000 rpm)Foot engine Hand rotated drillsElectric engine

Straight hand drill for direct access

Angle hand drill for indirect access

Foot engine

1900’s (5000-300000 rpm) Dental unit

Diamond cutting instruments

Tungsten carbide burs

Ball bearing handpiece

Water turbine handpiece

Belt driven handpiece

Air turbine straight and angled handpiece

a.Belt driven straight handpiece.b.gear-driven straight c.gear-driven angle handpiece

Page-chayes handpiece

Dental Handpiece

Definition:

A handpiece is a device for holding rotating instruments ,transmitting power to them, and for positioning them intraorally

Handpiece

Speed

Low speed

High speed

Straight

Angle

Air driven

Electric handpiece

Hybrid air electric

Rotary speed ranges

Low speed :below 12000 rpm

Mediun /intermediate: 12000 to 200000 rpm

High speeds:above 200000 rpm

Low speed :Uses:CleaningOccasional caries excavationFinishing and polishing procedure

Advantages:High tactile senseLess chances of overheating cut surfaces

Disadvantages:Less effective Time consumingMore heat and vibrations More run-out of bursCarbide burs break at low speed

Attachments:Straight-long shank laboratory bursProphylaxis angleAngle –latch –type rotary burs Mandrels

High speed:

Uses:Removal of decayRemoval of old restorationsTooth preparationsFinishing and polishing

Advantages :Faster with less pressure,vibration and heat

productionGreater control and ease of operation for

operatorMore longetivity of bursLess comprehension by the patientsSeveral tooth can be prepared at 1

apointment

Electric handpiece:Components:A controller An electric motorAttachments : that connect to the motor

and accept burs/diamonds and other cutting instruments.

Speed:They spin at speeds ranging from 1500 rpm to 40,000 rpm.

Two types:brush motors :This is typically a brief and straightforward

in-office procedure. require an annual brush change.brushless motors. :operate without brushes, this eliminates

the need for brush changes and allows the entire motor to be sterilized

Electric handpiece:

Advantages Disadvantages

More power and torque than air turbine

Heavier than air turbine

Better bur concentricity Expensive

Less vibrations and noise Learning curve required

Broad controllable speed range

Larger attachment head

Forward/reverse action

With proper attachments can be used for several purpose

Produces smoother surface

Air turbine handpiece:They employ compressed air to drive the turbines inside.

The movement of the turbines creates the rotary action at the end of the handpiece. 

Head: The head, or working end, of the high-speed handpiece is

where the burs and other cutting or polishing attachments are connected.

Chuck: The chuck is the part of the head that holds the burs and

other high-speed handpiece attachments.

Shank: The shank, or handle, is located between the head

and the connection end of the high-speed handpiece. The shank is often contra-angled (at an angle with) the head.

Connection End The connection end of the high speed handpiece is

attached to the shank on one end and to flexible hoses and cords on the other. These hoses and cords enclose the wires from the power source

Advantages Disadvantages

Excellent torque Noisy

Low maintenance Need air compression unit

Stall under pressure-safety feature

Easy to control and versatile

Hybrid air-electric handpiece(ATC):ATC refers to Adaptive Torque ControlUses a sensor in the air tubing to regulate a

valve which regulates the air pressure running through the turbine

Advantages:Power of electric handpiece but weight of

air turbine

Disadvantage:Compatible only with ATC units

Recent advances in air –driven handpiece:Head size and angulation:3 head sizes :miniature;mid –size;full-size

Handpiece angle:A typical handpiece angle is 22.5o

Newer design include angles with increase posterior visibility and patient comfort

Sound level: A normal high-speed handpiece can make noise

upto 71-92db Newer handpiece with sound levels in range of 58 to

71 db have become available

Ergonomics: Flared body shape towards the end of handpiece

Autoclavability: Materials like titanium are used for outer shell/body

to protect the external finish of the handpiece

Turbine design: Improvements in impeller design help in maintaining

constant speed and avoid stalling under load

New sensors tell the handpiece electronic “brain” when to increase power to maintain speed under load

Anti-suck technology: Manufacturers built this system in order to prevent

blood and aerosols from entering the water line.

Water delivery: Multi-port spray emanating water from the face of

handpiece which causes equal distribution of coolant

Cellular optics:One solid glass rod instead of optic fibres Improves operator visibilty with 25%Handpiece with LED’s which are more

brighter

Sterilization and care of handpiece

Do not exceed 275 0F /1350 C while autoclaving

Do not autoclave with bur attachedUse bags with 1 paper side to absorb

excess moistureDo not leave overnight or store in

autoclaveBefore removing flush water for 30 seconds Do not use any chemical solution for

cleaning Lubricate the handpieceRun the handpiece for 20 seconds after

oilingAlcohol can be used to wipe excess oil form

the fiber optics

Rotary cutting instruments

Common design characteristics Each instrument consist of 3 parts:

Shank:

Fits into the handpieceControls the alignment and concentricity of

the instrumentAcc to ADA no.23:a. straight handpieceb. latch-angle handpiecec. friction-grip handpiece type

Slow and medium speeds

High speeds

Neck :Connects head to shank

Transmits rotational and translation forces to the head

A neck to small will result in a weak instrument

A neck to large will hamper the visibility and restrict access for coolants

Head:Working part of the instrument Varies in size ,shape , materials

used ,according to intended use

Dental bursThe term ‘bur’ is applied to all rotary

cutting instruments that have bladed cutting heads

Can be used for: Finishing metal restorationsBone cuttingTooth preparationCavity preparation

Classification of bursSteel burs:Earliest burs madePerform well while cutting dentine at low

speedDull rapidly while cutting enamelMainly used for finishing purpose now

Carbide burs: Introduced in 1947Heads of carbide cemented on steel shanksParticle of tungsten carbide embedded in

matrix of cobalt or nickelAttached to steel necks by brazing or

welding

They are stiffer and stronger than steelThey breaks on a sudden blow or shock

unlike steel burs which bendPerform best at high speeds for tooth

preparation

Mechanism of action of burs:Cuts by “cutting operation”Regularly arranged blades remove small

shaving of the substrate as the bur rotates

Regular pattern of tooth removal by blades

Bur numbering systemsIn united states:Arbitrary numerical code is given for head

size and shape:Example:57=1mm diameter straight fissure34=0.8mm diameter inverted cone2=1mm diameter round bur

According to FDI and ISO:The bur name include separate designation

for shape(name) and size (number)and giving the head diameter in 10th of mm

Example :round010 straight fissure

plain 010 Inverted cone 080

Table 7-5

Bur shapes:Round :Spherical Initial entry Caries removal Preparation of retentive features

Inverted cone:Rapidly tapered cone with apex towards the

shankFor undercuts in tooth preparations

Pear –shaped bur:Slightly tapered cone with apex towards

shankThe edges are curved or roundedClass1 preparations for amalgams and gold

Straight fissure bur:Elongated cylinderRetentive groovesTooth preparation

Tapered fissure bur:Slightly tapered burSmall end of cone away from shank Used for :Occlusal guiding grooves Additional retentive features in complete

and partial cast crownsFinishing Proximal boxes,bevels,occlusal reduction in

class II inlays and MODs

Head design features:Spiral angle:Less on high speed bursLarger spiral angle smoother preparationSmaller spiral angle more efficient cutting

Crosscuts:Notches along the blades Increase cutting at low and medium speedsProduces rougher surface at high speeds

Blade number:Number of blades is always evenAreas between the blade is called flutesExcavating bur:6 to 8-10 bladesFinishing burs:12 to 40 blades

Blade design:

blade/cutting edge: part that contacts the horizontal line of work/tooth

Two sides of blade:Rake faceClearance face

Rake angle: angle between the radial line and the rake face

Negative rake angle: when the rake face is ahead of the radial line

Zero rake angle: when the radial line and the rake face coincide

Positive rake angle: when the rake face is behind the radial line

Clearance angle:The angle between the clearance face and

the tooth surface It eliminates the friction of clearance faceProvides a stop and prevents edge digging

in tooth structureProvides clearance space to wash out chips

ahead of the following face

Land: the plane surface immediately following the cutting edge

primary clearance angle: angle between the land and tooth

Secondary clearance angle: angle between clearance face and work

Edge angle :angle between two faces of the edge

Greater the edge angle stronger is the bladePositive rake angle:

1. Thinner and sharper teeth

2. More temperature rise

3. Less life

4. Used for cutting soft & weak materials.

5. Possesses greater efficiency

6. Has lesser edge strength.

Negative rake angle:

1. Broader teeth

2. Less temperature rise

3. More life

4. For hard brittle materials.

5. Possesses lesser efficiency

6. Has greater edge strength

Concentricity: Direct measurement of symmetry of bur head Indication whether one blade is shorter than the other

Run-out: Measures whether the centre of rotation passes

through the centre of rotation of the head Primary cause of vibration during cutting Run-out occurs when the -bur head is off the centre - bur neck is bent - bur isn’t held straight in

handpiece

Diamond abrasive instruments:Abrasive instruments are based on small,

angular particles of hard substance held in matrix of softer material

Cutting occurs at large number of points where theses hard particles abrade rather than along continuous blade edges

Mechanism of abrasion:It works by grinding operation

When cutting a ductile material like dentine

When cutting brittle material

Parts:Metal blankPowdered diamond abrasive Metallic bonding material

The diamonds are attached to blank by electroplating a layer of metal over diamond particles

Classification:According to head shape and size :Diag7-39Table 7-7

According to their shapes and sizes they can be classified as:Flat end tapered diamond cylinder: used for :Bulk axialOcclusal reduction Shoulder finish line in tooth preparation

Straight cylinder diamond with a tapered point:

Used for chamfer placement Also called Tinker diamond creates a chamfer with greater control

than the round-end tapered diamond. It is usually indicated for molars.

Round-ended tapered diamond cylinders:

used for :Axial and occlusal reduction and developing chamfer margins.

Less than half the diameter of the tip is used for chamfer margins.

Round diamonds: Used for:Depth grooves before reduction. To establish rest seats Reduce lingual surfaces of anterior

teeth.They vary in size and are measured to

determine the cut depth. They are numbered from ¼, ½, 1, 2 to

10.

Round diamond wheels (donut): Used for: Gross reduction Anterior teeth lingual reductions.

Thin tapered diamond cones (needle):used for: proximal cutting to isolate teeth from adjacent

teeth.

They tend to lose their sharpness sooner than coarse diamonds and are replaced frequently.

Tapered oblong diamond (flame): used for: bevel placement.

Football-shaped burUsed for: Occlusal reduction Reduction of palatal fossa of anterior

teeth

Barrel shaped bur:Used for:Occlusal reduction of posteriors

Depth marking burs:Used for:Marking depth grooves before tooth

preparation

End cutting burs: They are cylindrical in shape with just the

end carrying abrasive particles Used for: extending preparations apically

without axial reduction. They are numbered from 900 to 904

According to particle size of diamond abrasives:Particle

size(µm)

Super coarse -coarse

142

Coarse –regular 122

Coarse-regular 86

Fine 60

Fine 52

Fine-superfine-coarse-finishing

40

Superfine-medium-finishing

14

Ultrafine-fine finishing

8

Milling pastes 6

Polishing pastes 2-5

Particle size(µm)

Coarse 125-150

Medium 88-125

Fine 60-74

Finishing 10-38

Color coding:

Burs we use:Mani system

Other rotary instruments:Laboratory burs:They have longer shank and bigger headsUsed in slow speed handpieceMost commonly used burs :acrylic bursUsed for cutting and polishing of acrylic

Mandrels:Rods of various lengths used in low speed

handpieceAbrasives can be permanently attached or

separateShanks: latch; friction grip; straightAttachments: snap-on;screw;pin-design

Attachments:1.sandpaper discs: Used to polish and finish restorations Abrasives like garnet, sand,emery and cuttlefish are

used

2.carborandum disc:Also called separating disc or Jo-dandy discDouble sided Green-gray or dark colorsFast cutting of metal castings, cast gold,

porcelains, acrylics, and tooth structure.

3.diamond disc:Diamond particles bonded to metal

structureUsed to trim porcelain

Stones:Used for cutting,polishing

metal ,amalgam ,gold,porcelain restorations in laboratory

The abrasive material include garnet,aluminium oxide,silicon carbide

Used at slow speedsWhite stones have finer grit than green

Rubber wheels and discs:The matrix can be phenolic resins or rubberAbrasive can be sintered or resin bondedSofter and less wear-resistantUsed for finishing and polishing for metal

restorations Conforms to the surfaces like grooves and

cusps

Robinson’s brushes: Robinson brushes (stiff, medium, soft)

are used with pumice or tripoli. Slow speed with pressure produces

greater cutting potential; high speed with light pressure produces

a high-lustre finish

Chamois wheels : Chamois wheel are used only with dental

rouge and give a luster to the casting and dentures

Sterilization of dental burs

Cleaning After each use, clean the diamond bur by running

it against a wet diamond cleaning stone. Manual Cleaning: Presoak in cleaner to loosen

debris (5 min.). Brush away remaining debris. Rinse (2 min.), dry with absorbent towel.

Ultrasonic Cleaning: Burs may be ultrasonically cleaned after inserting them in bur holders (or blocks) to prevent damage. A cycle of 10 minutes is recommended, using a enzymatic cleaner, followed by a cold water rinse (2 min.)

Autoclave:A wrapped bur should be steam sterilized

at 132 oC for a minimum of 10 minutes or at 121oC for a minimum of 50 minutes.

An unwrapped bur should be steam sterilized at 132o C for a minimum of 8 minutes or at 121oC for a minimum of 30 minutes.

Do not exceed 135oC

Never Dry heat sterilizeExpose bur to chemical disinfection or cold

sterilizationSurface wipes Hand soap or detergents Surface sprays Sterilization bags containing disinfectants

Rotary instruments in endodontically treated tooth

Gates –glidden burs:Long thin shaft ending in a flame shaped

headUsed for coronal flaring of post spaceAvailable in set of 6 (0.5-1.5mm)Number is indicated by number of rings on

the shankSpeed 750-1500rpmFlexogates –gates made with NiTi and non-

cutting tips

Peeso reamers:Long ,sharp flutes connected to thick shaftUsed for gutta-percha removal in post

space preparationSafe endedTip diameter 0.7-1.7mmCaution:Do not follow root curvature ,can cause

lateral perforation and iatrogenic errors

Rotary in implant

Many inventories are used for surgical and prosthodontic phase of implant

Although most implant systems present approximately similar surgical and prosthetic components,most of them remain system specific

Implant motor which is not system specific is required for osteotomy and other procedures

Inventories used to practise basic implant procedure:

1. Dental implant surgical kit2. Implant motor(physiodispensor)3. Rotary reduction handpiece4. Basic oral surgery instruments5. Cleaning and sterilization instruments

1.Dental implant surgical kit:• Large carbide bur:

• Remove bony irregularities before osteotomy

:• Small round carbide

burs• Mark implant site• To make entry through

cortex

• Pilot drill:• 1st drill;to make entry• Should be used till full depth of implant size• Generally 2 mm

• Width increasing /widening drills

• Sequentially increase in diameter to widen osteotomy

• Have depth markings

:Parallel /depth guide/force indicatorsAccurate measure of depth in radiograph

after pilot drill (depth guide)To visualize parallelism during multiple

implants(parallel guide)To visualize direction of occlusal force in

future (force indicators)To access precise spacing in multiple

implants (spacing guide)

Drill stoppers:To prevent over-drilling

Bone tap/thread former:Used with non-cutting/non self-tapping

implants (to reduce pressure necrosis of bone){eg:mastero implant from bio-horizon}

Used at 20 -40 rpm

Countersink drill:After sequential drilling before implant

insertion To widen crestal bone to submerge wider

platform of implantUsed at 1500-2000rpm

Drill extender:Fitted to any drill to extend its length Implant depth probe:For depth evaluation of prepared

osteotomy Tactile examination of bone and sinus

membrane or any perforations

Implant insertion tool/driver: To drive implant during its insertion Rotary handpiece driven or hand ratchet

driven

Ratchet: A.ratchet wrench:Ratchet without torque measurement b.Torque ratchet:Torque level can be adjusted (0-45N) to check

primary stability

Screw driver/Hex driver:To drive connection screw,cover

screw,gingival formerHand driven /rotary handpiece driven

2.Implant motor: (physiodispensor)Surgical motor for implant insertionFeatures: A. torque control: Should have torque from 0-50 N (recommended 25 -

35N) B.speed control:While using a 20:1 reduction handpiece20 rpm (implant insertion)2500 rpm(drilling hard bone)(normal 800-1200 rpm) C.saline irrigation control:Controlled saline flow to reduce heat production

D.hand-piece selection:1:1 handpiece for osteoplasty.bone

harvesting,sinus window preparation20:1 reduction handpiece for osteotomy

preparation

E.programmes:programmes for particular implant procedure

F.forward and reverse function:Helps in taking drills/implants outRemoving cover screw,gingival former

G.foot control:Foot control with forward/reverse speed

funtions

H.autoclavable implant motor cord:To maintain surgical aspesis

Rotary handpiece:A.1:1 straight or contra-angle handpiece: Used for osteoplasty,autogeneous bone

harvesting,sinus window preparation

B.20:1 reduction handpiece: Used for osteotomy,bone tapping,implant

insertion Other 16:1 30:1 reduction handpieces

C.newer fiberoptic handpiece:Better visibility

4.Basic oral surgery instruments:Lips /cheek retractorsDiagnostic instrumentsBone measuring calliper Bone rongeur Periosteal elevatorsB.P handles and bladesNeedle holders,scissors,artery forceps etc

5.sterilization:A.ultrasonic cleaner: To remove blood clots/debries before

autoclavingB.fumigator: Implant chamber should be fumigated with

formalinC.autoclave:With dry cycles to sterilize implant kit and

instruments

References:Sturdevants’s art and science of operative dentistry 4th editionPhillips’s science of dental materials11th editionClinical implantology :ajay vikram singh Grossman’s Endodontic Practice 12th editionPrashtanth katta Shridhar et al Handpieces in dentistry-

Review ;Journel of dental science and research:5(1);1-9Sharon Crane Siegel Dental Burs-What Bur for Which

Application? A Survey of Dental Schools J Prosthod 1999;8:258-26

Sangamshewar ,Durga Hugaret al Decontamination Methods Used for Dental Burs – A Comparative Study J Clin Diagn Res. 2014 Jun; 8(6)

Alessandro Geminiani et al Influence of oscillating and rotary cutting instruments with electric and turbine handpieces on tooth preparation surfaces JPD 112(1) ;51-58