High speed technology / cosmetic dentistry training

Lasers And High Speed
Technology In
F.P.D
INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com

Lasers are devices which produce beams of very high
intensity light. A large number of current and potential
uses of lasers in dentistry have been identified that in
volve the treatment of soft tissues and the modification
of hard tooth structures, The word laser is an acronym
for "light amplification by stimulated emission of
radiation." A crystal or gas is excited to emit light pho
tons of a characteristic wavelength that are amplified
and filtered to make a coherent light beam. The effects
of the laser depend on the power of the beam and the
extent to which the beam is absorbed..

There are several types available based on
wavelengths. The lasers range from long
wavelengths (infrared), through visible wavelengths,
to short wavelengths (ultraviolet). Excimers are
special ultraviolet lasers. At the present time, CO2
and Nd: YAG (Neodymium: yttriumaluminum
garnet) lasers have shown the most promise. For
any application it is important to select the correct
wavelength for absorption of the energy and
prevention of sideeffects from heat generation

Scientific and commercial lasers produce highly col
limated beams, but such a beam is potentially
dangerous in clinical situations. The collimated beam
is directed via a flexible fiberoptic light pipe or mirror
train to the point of application where it is normally
focused by a lens to a focal area near the tip.
Once the beam is focused, the total energy it delivers
is a function of the intensity of the beam, the time of
exposure, and the area affected. These are used to
calculate the exposure dose (ED, Joules/cm2). ED =
(W) (t)/ (A) where W is the power (watts) emitted from
the light guide, t is the time (seconds) of the total
exposure, and A is the area (cm2) of the beam spot
on the substrate.

The effect of this energy depends on whether or not
the wavelength of the energy is absorbed by the
surface. The absorption wavelengths for various hard
and soft tissues are different. The best results are
obtained when the laser wavelength is matched to an
absorption band of the substrate. In some cases the
substrate must be coated with an absorbing dye to
facilitate beam interaction.
Interactions with the substrate can occur in
photothermal, photochemical, or other ways.www.indiandentalacademy.com

Generally dental lasers produce photothermal effects
with soft or hard tissue being ablated by the action. At
low temperatures, below 100° C, thermal effects
denature proteins, produce hemolysis, cause
coagulation, and cause shrinkage. Above 100° C,
water in soft or hard tissues boils, producing explosive
expansion. Above about 400° C, carbonization of
organic materials is completed with the onset of some
inorganic changes. As the temperature increases from
400° to 1400° C, inorganic constituents change in
chemistry, may melt and/or recrystallize, and may
vaporize. The actual temperatures depend on the initial
composition of the tissue involved. When the laser and
tissue are well matched, like the infrared lasers and
enamel, energy can be absorbed very rapidly. Even
low energy densities for short times can cause enamel
to melt and recrystallize.

Nd: Y AG laser units, each with a power
supply,
Laser probe and beam eminating
from probe tip
Control panel, foot controller,
fiber optic wave guide, and
probe

High energy densities and/or longer times produce
vaporization with drilling or cutting of the surface.
While infrared lasers produce their effects by heating
at the focal point, ultraviolet laser beams involve
photon energies coincident with bond energies of
cellular constituents and are capable of directly
disrupting the bonds that hold the molecules
together. For this reason, it is necessary to avoid
those wavelengths that are absorbed by proteins
such as DNA and RNA.
For dental applications, excessive heat must be
avoided to protect the dental pulp.www.indiandentalacademy.com

High surface temperatures for short periods of time
are acceptable as long as there is sufficient time or
path for heat dispersion. Lasers may be operated as
continuous wave (cw) or pulsed (p) lasers. To control
the beam energy it is common to pulse the beam.
Normally the pulse rate (20 to 1000 Hertz or cycles per
second) and pulse duration (1 to 50 microseconds) can
be selected by the operator. Pulsing occurs rapidly and
is not the same as the operator turning the beam on or
off. Local temperatures during lasing can reach many
hundreds of degrees C, but as long as the heat is
dissipated effectively, then pulpal temperatures will not
be affected. Clinical studies indicate that lasers can be
used without causing pulpal damage. Generally,
pulpal temperature increases of more than 4.50 to 5.50
C are considered damaging.www.indiandentalacademy.com

There are a number of lasers which are of practical
importance to medicine and dentistry. The ones of
most current interest to dentistry are Nd: YAG
(Neodymium: yttrium-aluminum-garnet, wavelength
= 1.064 µm), Er:Y AG (Er-bium: yttrium-aluminum-
garnet, wavelength = 2.94µm ), or CO2 (carbon
dioxide, maximum wavelength -10.6µm) . Argon,
helium-neon, Ho:Y AG, and excimer lasers are being
evaluated as well. More than one wave-length of
photon energy may be produced by a laser.

It is no longer appropriate to question "whether la-
sers will be used by dentistry" but "when they will
become commonplace." Current units are relatively
ex-pensive and must be used frequently in a dental
practice to justify the expense. At the moment, lasers
are used primarily for either soft tissue applications
or hard tissue surface modification They are not
used for cavity preparations because they are
inefficient and awkward for removing large amounts
of enamel or dentin, and that process would generate
in-tolerable amounts of heat. Therefore, lasers may
never replace a high-speed dental handpiece.www.indiandentalacademy.com

Lasers use in fixed partial prosthetics
Complete control of the oral environment at the
operative site is essential during restorative
procedures. This control extends beyond suppressing
saliva and blood to manage the gingiva surrounding
the teeth. Frequently , cases are encountered in
which the gingival tissues need to be altered because
of areas of inflammation , previous subgingival
restorations, or subgingival caries. The finish line may
need to be placed near the epithelial attachment
making it impossible to retract the gingiva without
stripping the attachment, bruising the periodontal
ligament, and creating uncontrolled bleeding.www.indiandentalacademy.com

Resulting in hemorrhage in the gingival sulcus
can make impression making impossible and
healing unpredictable
In these cases laser sulcular gingivoplasty can
be used to develop a new healthier gingival
sulcus to control hemorrhage and to remove just
enough epithelial attachment and periodontal
ligament to facilitate the placement of retraction
cord. Laser sulcular gingivoplasty improves
impression technique and minimizes gingival
recession.

Other uses of laser in dentistry
1. Caries removal
2. Cavity preparation
3. Surface modification
4. Bleaching
5. Calculus removal
6. Bone ablation and cartilage
reshaping
7. Analgesia
8. Composite curing
9. Alloy welding
10.Laser diagnostics like laser
fluorescence for detecting caries

Lasers are regulated by the Food and Drug
Administration (FDA) for safety and efficacy. They
have been approved for soft tissue surgery but not
for tooth prepa-ration. Other safety precautions are
prescribed. A door is required to close off the room
involving lasers and appropriate signs are needed to
indicate the presence of laser equipment. Eye
protection is required for the oper-ator, assistant,
and patient to protect against any inad-vertently
reflected laser light. The FDA will most likely expand
the number of sanctioned applications during the
next few years. www.indiandentalacademy.com

HIGH SPEED TECHNOLOGY IN FIXED
PARTIAL PROSTHETICS

Archeological evidence of dental treatment as early as
5000 BC, little is known about the equipment and
methods used then. Early drills powered by hand
.Much of the subsequent history leading to present
powered cutting equipment can be seen as a search
for improved sources of energy and means for holding
and controlling the cutting instrument. This has
culminated in the use of replaceable bladed or
abrasive instruments held in a rotary handpiece
usually powered by compressed air.

Early angle hand drill for indirect access cavities (circa 1850). The
bur is activated by squeezing spring-loaded handle.

A handpiece is a device for holding rotating instru
ments, transmitting power to them, and for positioning
them intraorally. Handpieces and associated cutting
and polishing instruments developed as two basic
types, straight and angle. Most of the development
of methods for preparing teeth has occurred within the
last 100 years and effective equipment for removal
(or preparation) of enamel has been available only
since 1947 when speeds of 10,000 rpm were first
used along with newly marketed carbide burs and
diamond instruments. Since 1953 continued
improvements in the design and materials of
construction for both handpieces and instruments
have resulted in equipment that is efficient as well as
sterilizeable, much to the credit of manufacturers and
the profession alike. Some of the more significant
developments of rotary dental equipment.

. Evolution of rotary equipments
Date Instrument Speed (rpm)
1728 Hand-rotated instruments 300
1871 Foot engine 700
1874 Electric engine 1000
1914 Dental unit 5000
1942 Diamond cutting instruments 5000
1946
Old units converted to increase
speed
10,000
1947 Tungsten carbide burs 12,000
1953 Ball bearings handpieces 25,000
1955 Water turbine angle handpiece 50,000
1955
Belt-driven angle handpiece (Page-
Chayes)
150,000
1957 Air turbine angle handpiece 250,000
1961 Air turbine straight handpiece 25,000
1962 Experimental air bearing handpiece 800,000
1994 Contemporary air turbine handpiece 300,000

One of the most significant advancements was the
introduction of the electric motor as a power source
in 1874. It was incorporated into a dental unit in
1914. The initial handpiece equipment and operating
speeds (maximum of 5000 rpm) remained virtually
unchanged until 1946. Steel burs that were used at
the time could not cut enamel effectively even when
applied with great force. With steel burs, increased
speed and power resulted only in increased heat and
instrument wear. Further progress was delayed until
the development of instruments that could cut
enamel. Diamond cutting instruments were
developed in Germany around 1935, but were scarce
in the United States until after World War II. In a 10
year period, starting in late 1946, cutting techniques
were revolutionizedwww.indiandentalacademy.com

Diamond instruments and tungsten carbide burs
capable of cutting enamel were produced
commercially. Both instruments performed best at
the highest speeds available and that prompted the
development of higher speed handpieces.
Obtaining speeds of 10,000 to 15,000 rpm was a
relatively simple matter of modifying existing
equipment by enlarging the drive pulleys on the
dental engine. By 1950, speeds of 60,000 rpm and
above had been attained by newly designed
equipment employing speedmultiplying internal
belt drives.

They were found to be more effective for cutting
tooth structure and for reducing perceived
vibration.
The major breakthrough in the development of
high speed rotary equipment came with the
introduction of contra-angled hand pieces with
internal turbine drives in the contraangle head.
Early units were waterdriven but subsequent units
were airdriven. Although most current air-turbine
hand pieces have freerunning speeds of
approximately 300,000 rpm.

PageChayes handpiece (circa 1955). The first driven angle
handpiece to operate successfully at speeds 0f 100,000 rpm.

The small size of the turbine in the head limits their
power output. The speed can drop to 200,000 rpm or
less with small lateral workloads during cutting, and
the handpiece may stall at moderate loads. This
tendency to stall under high loads is an excellent
safety feature for tooth preparation, since excessive
pressure cannot be applied. Airdriven handpieces
continue to be the most popular type of handpiece
equipment because of the overall simplicity of de
sign, ease of control, versatility, and patient accep
tance. The external appearance of current
handpieces is very similar to the earliest models

The low torque and power output of the contraangle
turbines made them unsuitable for some finishing
and polishing techniques where large heavy
instruments are needed. The application of the
turbine principle to the straight handpiece
eliminated the necessity of having an electric engine
as part of a standard dental unit. The design of the
straight handpiece turbine provided the desirable
high torque for lowspeed operation.

Rotary speed ranges
The rotational speed of an instrument is measured in
revolutions per minute (rpm). Three speed ranges are
generally recognized:
low or slow speeds (below 12,000 rpm),
medium or intermediate speeds (12,000 to 200,000
rpm), and
High or ultrahigh speeds (above 200,000 rpm).
The crucial factor for some purposes is the
surface speed of the instrument, the velocity at which
the edges of the cutting instrument pass across the
surface being cut. This is proportional to both the
rotational speed and the diameter of the instrument,
with large instruments having higher surface speeds atwww.indiandentalacademy.com

Although intact tooth structure can be removed by an
instrument rotating at low speeds, it is a traumatic experience
for both the patient and the dentist. Lowspeed cutting is
ineffective, time consuming, and requires a relatively heavy
force application. This results in heat production at the
operating site and produces vibrations of low frequency and
high amplitude. Heat and vibration are the main sources of
patient discomfort. At low speeds burs have a tendency to roll
out of the cavity preparation and mar the proximal margin or
tooth surface. In addition, carbide burs do not last long
because their brittle blades are easily broken at low speeds.
The low speed range is used for finishing and polishing
procedures. At low speeds, tactile sensation is better and
there is generally less chance for overheating cut surfaces. The
availability of a low speed option is a valuable adjunct for many
dental procedures.

At high speed, the surface speed needed for efficient
cutting can be attained with smaller and more
versatile cutting instruments. This speed is used for
tooth preparation and removing old restorations.
Other advantages are:
(I) diamond and carbide cutting instruments remove
tooth structure faster with less pressure, vibration,
and heat generation;
(II)the number of rotary cutting instruments needed is
reduced because smaller sizes are more universal in
application;
(3) The operator has better control and greater ease of
operation;

(4) instruments last longer;
(5) Patients are generally less apprehensive
because annoying vibrations and operating time
are decreased; and
(6) Several teeth in the same arch can and should
be treated at the same appointment.

Contrangle air turbine handpiece connected to airwater
supply line.

Variable control to regulate the speed makes the
handpiece more versatile. This allows the operator
to easily obtain .the optimal speed for the size and
type of rotating instrument at any stage of a specific
operation.
Increasing concern about patienttopatient transfer
of infectious agents has put emphasis on other
aspects of handpiece performance. Recent
advancements in both straight and angle
handpieces allow repeated sterilization.

Oral fluid contamination problems of rotary
equipment and especially the high speed
handpiece involve;
Contamination of handpiece external surfaces
and crevices
Turbine chamber contamination that enters the
mouth
Water spray retraction and aspiration of oral fluids
into the water lines, growth of environmental
aquatic bacteria in water lines.
Exposure of personnel to spatter and aerosols
generated by intraoral use of rotary equipment

Submersing high speed hand piece in a high level of
disinfectant is not an accepted method, through
scrubbing and applying best disinfectant (2%
glutaraldehyde) to inoculated surface reduces
bacteria on its surface is an acceptable method..
Following treatments oral bacteria have been readily
recovered form the water lines of dental units. The
minimal recommendation is to operate the
handpiece spray for 20 seconds between
appointments to help expel any aspirated infectious
microorganism.

However sterilization produces some damage to
many parts of the handpiece thus requiring more
frequent service and repair. Other improvements of
the angle handpiece include smaller head sizes,
more torque, lower noise levels, and better chucking
mechanisms.Since 1955 angle handpieces have had
an airwater spray feature to provide cooling,
cleansing, and improved visibility. Most modern
angled handpieces also include fiberoptic lighting of
the cutting site. .

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