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
instruments
 1800’s (300-1000 rpm)
 Foot engine
 Hand rotated drills
 Electric 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

 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:
 Cleaning
 Occasional caries excavation
 Finishing and polishing procedure
 Advantages:
 High tactile sense
 Less chances of overheating cut surfaces

 Disadvantages:
 Less effective
 Time consuming
 More heat and vibrations
 More run-out of burs
 Carbide burs break at low speed
 Attachments:
 Straight-long shank laboratory burs
 Prophylaxis angle
 Angle –latch –type rotary burs
 Mandrels

High speed:
 Uses:
 Removal of decay
 Removal of old restorations
 Tooth preparations
 Finishing and polishing

 Advantages :
 Faster with less pressure,vibration and heat
production
 Greater control and ease of operation for operator
 More longetivity of burs
 Less comprehension by the patients
 Several tooth can be prepared at 1 apointment

Electric handpiece:
 Components:
 A controller
 An electric motor
 Attachments : 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

 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 Control
 Uses 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 attached
 Use bags with 1 paper side to absorb excess
moisture
 Do not leave overnight or store in autoclave
 Before removing flush water for 30 seconds
 Do not use any chemical solution for cleaning
 Lubricate the handpiece
 Run the handpiece for 20 seconds after oiling
 Alcohol can be used to wipe excess oil form the
fiber optics

Common design characteristics
 Each instrument consist of 3 parts:

Shank:
 Fits into the handpiece
 Controls the alignment and concentricity of the
instrument
 Acc to ADA no.23:
 a. straight handpiece
 b. latch-angle handpiece
 c. 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 burs
 The term ‘bur’ is applied to all rotary cutting
instruments that have bladed cutting heads
 Can be used for:
 Finishing metal restorations
 Bone cutting
 Tooth preparation
 Cavity preparation

Classification of burs
 Steel burs:
 Earliest burs made
 Perform well while cutting dentine at low speed
 Dull rapidly while cutting enamel
 Mainly used for finishing purpose now

 Carbide burs:
 Introduced in 1947
 Heads of carbide cemented on steel shanks
 Particle of tungsten carbide embedded in matrix
of cobalt or nickel
 Attached to steel necks by brazing or welding

 They are stiffer and stronger than steel
 They breaks on a sudden blow or shock unlike
steel burs which bend
 Perform 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 systems
 In united states:
 Arbitrary numerical code is given for head size
and shape:
 Example:
 57=1mm diameter straight fissure
 34=0.8mm diameter inverted cone
 2=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

Bur shapes:
 Round :
 Spherical
 Initial entry
 Caries removal
 Preparation of retentive features
 Inverted cone:
 Rapidly tapered cone with apex towards the
shank
 For undercuts in tooth preparations

 Pear –shaped bur:
 Slightly tapered cone with apex towards shank
 The edges are curved or rounded
 Class1 preparations for amalgams and gold
 Straight fissure bur:
 Elongated cylinder
 Retentive grooves
 Tooth preparation

 Tapered fissure bur:
 Slightly tapered bur
 Small end of cone away from shank
 Used for :
 Occlusal guiding grooves
 Additional retentive features in complete and
partial cast crowns
 Finishing
 Proximal boxes,bevels,occlusal reduction in class
II inlays and MODs

Head design features:
 Spiral angle:
 Less on high speed burs
 Larger spiral angle smoother preparation
 Smaller spiral angle more efficient cutting
 Crosscuts:
 Notches along the blades
 Increase cutting at low and medium speeds
 Produces rougher surface at high speeds

 Blade number:
 Number of blades is always even
 Areas between the blade is called flutes
 Excavating bur:6 to 8-10 blades
 Finishing burs:12 to 40 blades

 Blade design:
 blade/cutting edge: part that contacts the
horizontal line of work/tooth
 Two sides of blade:
 Rake face
 Clearance 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 face
 Provides a stop and prevents edge digging in
tooth structure
 Provides 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 blade
Positive 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 blank
 Powdered 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 :
 Diag7-39
 Table 7-7

According to their shapes and
sizes they can be classified as:
Flat end tapered diamond cylinder:
 used for :
Bulk axial
Occlusal 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 bur
 Used 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

Other rotary instruments:
 Laboratory burs:
 They have longer shank and bigger heads
 Used in slow speed handpiece
 Most commonly used burs :acrylic burs
 Used for cutting and polishing of acrylic

 Mandrels:
 Rods of various lengths used in low speed
handpiece
 Abrasives can be permanently attached or
separate
 Shanks: latch; friction grip; straight
 Attachments: 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 disc
 Double sided
 Green-gray or dark colors
 Fast cutting of metal castings, cast gold, porcelains,
acrylics, and tooth structure.

 3.diamond disc:
 Diamond particles bonded to metal structure
 Used 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 speeds
 White stones have finer grit than green

 Rubber wheels and discs:
 The matrix can be phenolic resins or rubber
 Abrasive can be sintered or resin bonded
 Softer and less wear-resistant
 Used 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

 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 sterilize
 Expose bur to chemical disinfection or cold
sterilization
 Surface 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 head
 Used for coronal flaring of post space
 Available in set of 6 (0.5-1.5mm)
 Number is indicated by number of rings on the
shank
 Speed 750-1500rpm
 Flexogates –gates made with NiTi and non-
cutting tips

Peeso reamers:
 Long ,sharp flutes connected to thick shaft
 Used for gutta-percha removal in post space
preparation
 Safe ended
 Tip diameter 0.7-1.7mm
 Caution:
 Do not follow root curvature ,can cause lateral
perforation and iatrogenic errors

 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 kit
2. Implant motor(physiodispensor)
3. Rotary reduction handpiece
4. Basic oral surgery instruments
5. 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 indicators
 Accurate 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 implant
 Used 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
former
 Hand driven /rotary handpiece driven

2.Implant motor:
(physiodispensor)
 Surgical motor for implant insertion
 Features:
 A. torque control:
Should have torque from 0-50 N (recommended 25
-35N)
 B.speed control:
While using a 20:1 reduction handpiece
20 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 preparation
 20:1 reduction handpiece for osteotomy
preparation
 E.programmes:programmes for particular implant
procedure

 F.forward and reverse function:
 Helps in taking drills/implants out
 Removing 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 retractors
 Diagnostic instruments
 Bone measuring calliper
 Bone rongeur
 Periosteal elevators
 B.P handles and blades
 Needle holders,scissors,artery forceps etc

5.sterilization:
 A.ultrasonic cleaner:
 To remove blood clots/debries before autoclaving
 B.fumigator:
 Implant chamber should be fumigated with
formalin
 C.autoclave:
 With dry cycles to sterilize implant kit and
instruments

Rotary instruments in prosthodontics