Surface Finishing of Unused Rotary Endodontic Instruments: A SEM Study
Rotary instruments in prosthodontics
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Transcript of Rotary instruments in prosthodontics
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