This document discusses rotary instruments used in dentistry, including their types, functions, and proper use and maintenance. It describes air-driven high-speed handpieces and lower-speed electric handpieces, along with the burs, stones, discs and other attachments used with each. Precautions for minimizing heat, pressure and trauma to patients during procedures are also outlined.

1. Armamentarium - II
Dr. Habiba Mumtaz
Lecturer
Department of Operative Dentistry

2. ROATARY INSRUMENTS
 These are small and held in a handpiece e.g. burs,
stones, discs
 The instrument is rotated in the handpiece from an
external source, either compressed air or directly by an
electric motor
 Two main broad types of equipment used covering two
speed ranges
1) The airotor
2) Low-speed handpieces

3. The airotor (air turbine)
 Gives the highest speeds but with less torque
than low-speed handpieces
 Speed ranges from 250 000-500 000 rev/minute
 High speeds are achieved by a small air-driven
rotor or turbine mounted in bearings in the head
of a contra-angle handpiece
 Shank of the bur is inserted into the rotor of the
handpiece and revolves with it
 Handpiece contains a system which directs
water spray at the cutting head of the bur
 Often contains a fibre-optic light
 Rotates only clockwise

4. Low-speed handpieces
 They are either:-
 Contra-angle—used exclusively in the
mouth
 Straight—used for trimming temporary
crowns or for other procedures carried
out outside the mouth
 Unlike the airotor, speed is less
(operating over different ranges ) but
torque is greater
 Most are equipped with use of a water
spray incase of higher speed ranges

5.  Drive for low-speed handpieces comes from a
small electric motor attached to the handpiece
 Speed controlled by, foot control, OR control on
the electric motor, OR on the dental unit
 Alternatively, Air motor, less expensive, is
directly attached to the end of the handpiece
 Unlike the airotor, Low-speed handpieces can
be rotated clockwise AND anti-clockwise

6. Maintaining and sterilizing handpieces
 They are all autoclavable and
should be done so in between
patients
 Lubricated before and after
autoclave
 Lubricant is delivered from an
aerosol using an adapter
 OR by an air-driven cleaning
and lubricating machine

7. Burs and stones
 Rotary cutting instruments are retained
in the handpiece by :-
 Friction—in the older type of airotors
 A latch grip–in the contra-angle low
speed handpieces
 A quick release clamping chuck—in
the straight handpiece and now in most
contra-angle, low speed handpieces
and airotors
 Cutting end of the instrument consists
of either a set of blades of tungsten
carbides, or steel or abrasive material,
ranging in hardness from diamond to
sand

8. Airotor burs They have friction grip shanks
 Cutting end is of a hard material like diamond or
tungsten carbide due to use of high speed
 They are used to cut sound enamel and dentine
and to remove existing restorations
 Not used to remove caries
 For enamel cutting—best to use diamond and
some tungsten carbide burs
 For ceramic materials—best cut with diamond
burs
 All other restorations—best cut with tungsten
carbide
 Metal restorations—cut by special tungsten
carbide burs (Beaver burs)
 Diamond instruments cut metal very slowly and
ordinary tungsten carbide burs tend to break

9. Low-speed burs
 Large selection of burs available in a range
of sizes, numbered according to the
diameter of the cutting tip
 Steel burs—not expensive but have a short
working life as they are rapidly blunted by
enamel and rust if not dried after
autoclaving
 Tungsten carbide—more commonly used
now as they run more smoothly than steel
and can be autoclaved
 Round burs used to remove soft carious
dentine at slow speed
 Steel burs—does not cut sound dentine or
enamel very quickly at slow speed allowing
the clinician to feel his way around the
carious lesion

10. Stones-shaping instruments
 Made of abrasives such as carborundum
(green ) and alundum (white or pink )
 Moulded into a range of shapes and
fixed directly to a bur shank
Uses:-
 1) final stages of tooth preparation for
smoothing the surfaces
 2)shaping, smoothing and finishing cast
metal and porcelain restorations out of
the mouth
 For this, they are used at medium speed
in the straight handpiece

11. Finishing instruments
1) Burs and points
 Made of steel—for
amalgam
 Made of very fine
diamond particles
and or multifluted
tungsten carbide—
for composite

12. 2)Discs
 Rigid and flexible discs available with
abrasive materials of different degrees
of coarseness applied to one or both
surfaces
 Some discs also cut at their edges
 All discs are either mounted on
mandrels of screw design or snap-on
mandrels
 Rigid discs in a straight handpiece are
used for cutting and trimming, posts and
temporary crowns outside the mouth
 Flexible single-sided discs commonly
used for finishing composite and other
restorations

13. 3) Abrasive strips
 Used to finish restorations and are hand held
flexible strips with abrasive on one side
 Metal strips—used to remove over hanging
amalgam ledges on old restorations
 However, these are not very effective and
harmful to the gingival papilla
 Plastic strips– used to finish composite
restorations on the approximal surfaces of teeth

14. Maintaining and sterilizing burs and
stones
 All burs and stones should be autoclaved
 Re-usable Steel burs are dried quickly after
autoclaving or they will corrode
 Flexible discs and strips are disposable
 Tungsten carbide burs and diamond burs should
be assessed regularly and discarded if they
become blunt, worn out, break or are bent

15. Tooth preparation with rotary instruments
Speed, torque and ‘feel’
 Torque is the “turning moment” of the instrument
 High-torque system—pressure applied to the surface by means of the bur
with only minimal slowing of the drive
 However, heat, vibration and increased amount of material is removed
 High speed—low torque
 Enamel, porcelain and metal—cut at high speed with low torque
 Carious dentine or other softer material—cut at low speed with higher torque
 High speed—cutting has to be controlled visually as there is very little “feel”
and difficulty with water spray
 Low speed—much easier to feel the cutting process

16. Heat generation and dissipation
 Heat is generated in proportion to the work done
 Potentially damaging to the vital pulp
 High speed cutting always produces sufficient heat and
use of cooling water spray is required
 Prolonged slow-speed cutting may also produce heat
 Advised to wash and dry the cavity at frequent intervals
to improve visibility and cooling of the tooth

17. Effects on the patient
 Tooth preparation with rotary instruments has the
potential of producing
 pain
 pressure
 vibration
 trauma and
 long term-effects on the pulp

18.  The longer time of cutting and the higher the local temperature
produced, the greater is the threat of thermal trauma
 Steel burs produce more heat then carbide burs due to inefficient
cutting
 Burs and diamonds when plugged with debris or if are dull do not
cut efficiently resulting in increased heat production
 Diamond instruments generate more damaging heat than carbide
burs when used without coolants
 Hence, instrument coolants like air or air-water spray are most
commonly used
 Provided that cooling is adequate, superficial enamel cutting may
not be painful…however, cutting dentine in a vital tooth may be
painful and local analgesics may be used
 Vibration which may be produced in a rotary instrument and cause
discomfort in a patient is produced less if the bur is gripped more
firmly in the hand piece OR an electric motor drive is used instead of
an air motor

19.  Pressure needs to be controlled as there is greater pressure in a
low speed and higher torque as compared with high speed and low
pressure
 Proper examination of the tooth and pre-operative radiographic
assessment will cause accidental and unexpected exposure of the
pulp due to careless cutting
 Damage to sound adjacent teeth is common when preparing
approximal surfaces
 Damage to adjacent gingival margin is also very common
 Particles of old restoration, tooth structure, bacteria and other debris
are discharged at high speed s from the patients mouth which may
cause eye damage

20. Precautions
All this can be avoided by:-
 Choosing proper size and shape of bur
 Use of rubber dam for isolation
 Use of gingival retraction cord
 Use of protective eye glasses

21. Finishing and polishing
 For surface finish, straight burs provide a smoother finish than
cross-cue designs
 Tungsten carbide burs provide a smoother finish than either steel or
diamond burs
 Margins and surfaces of restorations should be smooth and
polished
 This minimizes plaque retention
 All materials should be shaped when they are unset so minimal
shaping is required with abrasive or finishing instruments
 For increased shaping, coarser instrument used first and finest at
the end of the procedure

22. Auxiliary instruments and equipment
Fibre-optic lights
 Fibre-optic lighting system provides good
illumination during cavity preparation
 Present at the tip of the handpiece and available
with airotors and low-speed handpieces
 Also available are independent fibre-optic lights
and those built in some mouth mirrors

23. Light used for Polymerization
of certain materials
 May restorative materials now
polymerized using intense visible
light
 Light is transmitted down a flexible
light guide which is either a fibre-
optic gel or cable
 Light can also be contained in a
hand held equipment connected to
an electrical supply
 Disadvantages:- light of such
intensity may damage the retina,
hence must never be shone directly
in anyone’s eye
 Therefore, protective screens or
spectacles are used

24. Ultrasonic scalers
 The working tip vibrates at ultrasonic frequency under voluminous
water sprays
 They provide a quick and efficient way of removing calculus
 Also used in endodontics
 And for loosening crowns or posts
Electrosurgical equipment
 They remove hyperplastic gingival tissue
 Gain access to cavity margins
 Expose the margins of a tooth fractured below gingival level