LASERS IN

ENDODONTICS

DR. JAGADEESH KODITHYALA

2ND YEAR P.G STUDENT

GOVT.DENTAL COLLEGE AND HOSPITAL

Introduction

Laser is an acronym for Light Amplification by Stimulated Emission of Radiation

Laser is the brightest monochromatic light existing today

After invention of laser it has found wide spread application in various fields like communication, industry, defense, and medicine

Lasers are the single most important advancement in the field of Endodontics and they changed the ways in which many procedures can be done

HISTORY

Albert Einstein - Stimulated Emission -Quantum Theory of Radiation.

1954’s, Bell Labs’ Arthur L. Schawlow & Charles H. Townes - MASER (microwave amplification by stimulated emission of radiation), by means of ammonia gas and microwave radiation.

1958, Schawlow & Townes - extending the MASER principle to the optical portion of the electromagnetic field - LASER (Light Amplification by Stimulated Emission of Radiation) was invented

May 16, 1960 -Theodore Maiman’s ruby laser - first working laser in

history.

1960’s, Dr. Ali Javan - first gas laser with Helium Neon.

4 years later, 1964 - the CO2 laser was successfully shaped by

Kumar Patel

1971 Weichman and Johnson – introduced LASERS in Endodontics.

1990, FDA approved lasers usage in intraoral soft tissue surgery.

1986 Zakirasen et al - Sterilization of Root Canals.

1998 Mazeki et al – Root canal shaping with Er:YAG laser.

LASER PHYSICS

COMPONENTS OF A TYPICAL LASER

OPTICAL CAVITY

This is an internally polished tube occupying the centre of the device

Active medium

This consists of chemicals that fill the core of the optical cavity , when

stimulated the active medium emits laser light. The active medium

may be:

GAS - Argon, CO2

CRYSTAL – Solid rods of garnet crystals grown with various

combinations of yittrium, Aluminium,scandium and gallium

‘’doped’’ with chromium, neodymium or erbium.

Solid state semiconductor wafers

Multiple layers of metals like gallium, aluminium, indium, arsenide

LASERS GENERALLY NAMED AFTER THE ACTIVE MEDIUM

EXCITATION SOURCE

This surrounds the optical cavity and provides energy for exciting

the active medium.

This may be flash light, arc light or an electromagnetic coil.

Optical resonator

This consists of two parallel mirrors placed at each end of the optical cavity.

Laser light that is produced by the stimulated active medium is bounced back

and forth in the optical cavity by these mirrors which amplifies the light beam.

Cooling unit

Heat is generated as a by-product

To dissipate this heat, air or water – assisted coaxial

coolants are provided in the unit

Delivery system

The laser light may be delivered by a quartz fiberoptic,

a flexible hollow wave guide or a handpiece

Control panel

This provides control over the power output

Collimated

Coherant

Monochromatic

LIGHT

BASIC PRINCIPLES OF LASER

Amplification

Reflective Mirror

Partially transmissive mirror

Radiation

INTERNATIONAL ENDODONTIC JOURNAL,

33, 173–185, 2000

LASER EMISSION MODES

laser energy is emitted continuously as long as the laser is

activated

Some times these lasers have a mechanical shutter to produce a

gated or super pulsed energy.

Pulse durations can range from tenths of a second to several

hundred microseconds.

Eg: CO2, and diode lasers

Very short bursts of laser energy is emitted due to the flash lamp

pumping mechanism.

The pulse durations are hundreds of microsecond and there is

Relatively long interval between pulses

Eg: Nd:YAG, Er:YAG, Er,Cr:YSGG lasers

Types of lasers

Based on wave length

Emit visible light – 488 nm, 514 nm – argon laser

Diode laser – Al Ga As – 800 – 830 nm

Ga As - 904 nm

In Ga As – 980 nm

Nd:YAG-1064 nm

Near infrared

Er,Cr:YSGG – 2,780 nm

Er:YAG – 2,940 nm

CO2 – 10600 nm – Far infrared

Mid infrared

Based on the target tissue where they are

effective

Soft tissue lasers – diode, CO2, Argon, and Nd:YAG.

Hard tissue lasers – Er:YAG, Er,Cr:YSGG

According to ANSI and OHSA standards lasers are

classified as:

Class I

These are low powered lasers that are safe to use, e.g. Laser beam

pointer

Class II

Low powered visible lasers that are hazardous only when viewed

directly for longer than 1000 seconds,

e.g. He–Ne lasers.

Class IIb

Low powered visible lasers that are hazardous when viewed for

more than 0.25 seconds.

Class IIIa

Medium powered lasers that are normally hazardous if

viewed for less than 0.25 seconds without magnifying

optics.

Class IIIb

Medium powered lasers that can be hazardous if viewed

directly.

Class IV

These are high powered lasers (>0.5W) that produce

ocular skin and fire hazards.

Reflection results

in little or no absorption, so

that there is no thermal

effect on the tissue.

Transmission of light transfers

energy

through the tissue without any

interaction and thus

does not cause any effect or

injury.

When scattered, light travels

in

different directions and

energy is absorbed over a

greater surface area,

producing a less intense and

less precise thermal effect

when absorbed, light energy is

converted into thermal energy

The term focused and defocused

refers to the position of the focal

point in relation to the tissue

plane. The laser beam can be

focused through a lens to achieve

a converging beam, which

increases in intensity to form a

focal spot or hot spot, the most

intense part of the beam. Past the

focal spot, the beam diverges

and the power decreases

When working on tissue, the laser should always be used

either with the focal point positioned at the tissue

surface or above the tissue surface. The laser should

never be positioned with the focal spot deep or within

tissue as this can lead to deep thermal damage and

tissue effects.

Laser effect on tissues

The light energy from a laser can have four different interactions

with the target tissue.

• Photo chemical interaction.

• Photo thermal interaction

• Photo mechanical interaction

• Photo electrical interaction

certain wave lengths of laser are absorbed by naturally occurring chromophores and induce certain biochemical reactions

Bio-stimulation, - stimulatory effects of laser light on biochemical and molecular processes that induce healing and repair of tissues.

Photodynamic therapy- which is the therapeutic use of lasers to induces reactions and produce biochemically reactive form of oxygenThis oxygen disrupts the membrane of micro-organisms

Eg: tolonium chloride 635nm laser oxygen

Photo chemical interactions

Photo thermal interactions

Photo ablation-, or the removal of tissue by vaporization and superheating of tissue fluids

Coagulation and hemostasis.

Photopyrolysis or the burning away of tissues

Type of thermal reaction depends on the Spot size

Power density

Pulse duration

Pulse frequency

Optical properties and composition of irradiated tissue

Non thermal interactions produced by high energy short

pulsed laser light

•Photo-disruption – shock waves by laser –rupture the

intermolecular and atomic bonds

•Photo-disassociation - which is the breaking apart of

structures

•Photo-acoustic interactions- shock wave explode or

pulverize the tissue, produces a crater

Photo mechanical interaction

Photo plasmolysis, tissue is removed through the

formation of electrically charged ions and particles that

exist in a semi-gaseous, high-energy state.

Photo electrical interactions

Absorption and transmission – depends on wavelength of laser

Laser causes zones of carbonization, necrosis and induce cracks in the enamel

Steam pressure build up in the dental tissues and explosive expansion takes with in the surrounding hydroxyapatite

This process leads to surface holes or craters on the surface and hydroxyapatite has been vaporized

This thermo-mechanical effect is very efficient in removal of hydroxyapatite in hard tissues

Laser and hard tissue interactions

To prevent the pulpal damage by thermal effects of

laser air water spray is used It produces

Cooling effect on dental pulp

Wash away the debris

Keeping the area moist

Prevents drying of tissues

Advantages and Limitations

Advantages

Reduced need for anesthesia

Greater comfort during and after surgery.

Haemostasis and reduced risk of blood borne

pathogens

High patient acceptance

Reduced stress and fatigue for the practitioner and

staff.

Produce less collateral thermal damage than with an

electrocautery.

Limitations

All lasers require specialized training and attention to

safety precautions.

Slower than traditional methods.

No single laser can perform all desired dental

applications

LASER WAVE LENGTHS USED IN DENTISTRY

CO2 LASER:

-gas active medium laser

- hollow-tube like wave – guide

-continuous or gated pulse mode orpulsed mode

-Wavelength – 10,600 nm.

-Well absorbed by water

Rapid soft tissue remover and has a shallow depth of tissue penetration, which is important when treating mucosal lesions.

Beam can be focused to create a precised coagulation of small blood vessels

Principle: CO2 + energy CO+O ‾

Resulting molecule no longer able produce the CO2 laser. This degrading nature of CO2 brought several developments in the CO2 laser system

Especially useful for cutting dense fibrous tissue.

-Focused onto the surgical site in a non-contact fashion.

-Loss of tactile sensation is disadvantageous, but the tissue ablation can be precise with careful technique.

Laser systemsFlowing gas CO2 system

Sealed tube free space CO2 laser system

Radio frequency wave guide CO2 laser system

-Has a solid active medium, a crystal of yttrium – aluminium – garnet doped with neodymium.

-Wave length -1064nm

-Fiber optic delivered in a free running pulsed mode .

-Most often in contact with the tissue.

-First laser designed exclusively for dentistry.

-Highly absorbed by pigmented tissue and is about 10,000 times more absorbed by water than an argon laser.

-Common clinical applications are for cutting and coagulation of dental soft tissues with good hemostatic capability.

Nd:YAG

Er, Cr:YSGG and Er:YAG

Er,Cr:YSGG (2790 nm) has an active medium of a solid crystal

of yttrium – scandium-gallium-garnet that is doped with erbium

and chromium.

Er:YAG (2940 nm) has an active medium of a solid crystal of

yttrium-Al-Garnet that is doped with erbium.

-Both are delivered fiber optically in the free running pulsed

mode.

The fibers are air-cooled and have a larger diameter than the other lasers

mentioned, making the delivery system somewhat less flexible.

-They have the highest absorption in water of any dental wave length

and have a high affinity for hydroxyapatite .

-These lasers are ideal for caries removal, root canal preparation and

tooth preparation when used with a water spray.

ARGON LASER

- Argon lasers have an active medium of argon gas that is

fiberoptically delivered in continuous –wave and gated – pulse modes.

- Two emission wavelengths, and both are visible to the human eye

488nm (blue in color) and 514 nm (blue – green)

- Both wavelengths are not well absorbed in dental hard tissues and

are poorly absorbed in water.

- can be used as an aid in caries detection. The diseased, carious

area appears as dark orange-red color and is easily discernible from

the healthy structures.

Ho: YAG

Has solid active medium, a crystal of Y.A.G. doped with Holmium.

-Fiberoptically delivered in contact with the tissue in free-running pulsed mode.

-Wavelength – 2120 nm.

-Ho laser has little affinity for pigmented tissue; its hemostatic ability is decreased because of its lower absorbency into hemoglobin and other similar pigments.

-Absorbency by tooth structures is low.

-Frequently used for arthroscopy surgery on the TMJ .

Diode

-Have a solid active medium; it is a solid-state semi

conductor laser that uses some combination of Al,

gallium and arsenide to change electric energy into light

energy.

-Wave length range from 800-980nm

-Laser energy is delivered fiberoptically in

continuous-wave and gated – pulse mode; used in

contact with the tissue.

-Poorly absorbed by tooth structure so that soft

tissue surgery can be performed safely in close

proximity to enamel, dentine and cementum.

-An excellent soft tissue surgical laser indicated

for cutting and coagulating gingiva and

mucosa and for soft tissue curettage, or sulcular

debridement.

Clinical Applications Of Lasers In Endodontics

Heat test

Pulp vitality

Indirect pulp capping

Direct pulp capping

Vital pulp amputation

Access cavity preparation and orifice enlargement

International endodontic journal 2000

Pulpectomy

Root canal preparation with lasers

Debris removal at apical foramen

Sterilization and disinfection of infected root canals

Closure of apical foramen

Endosurgery

International endodontic journal 2000

Heat test

Instead of hot GP

Better pulpal response than hot GP

Pain response depends on

Enamel thickness

Dentin thickness

Pain threshold level

International endodontic journal 2000

Differential diagnosis -Between normal pulp, acute pulpitis, chronic pulpitis

Laser used - Nd:YAG at 2W, 20 pulses per sec (pps) at distance of 10mm from the tooth surface

Normal pulp- mild transient pain with in 20 to 30 sec and disappears in a couple of seconds after laser stimulation is stopped

Acute pulpitis – pain induced immediately and continuous more than 30sec

Chronic pulpitis – no pain or pain started after one min application and continuous more than 30sec

International endodontic journal 2000

LASER DOPPLER FLOWMETRY:

LDF was developed to assess blood flow in micro vasculature

Ex: in retina , gut mesentery , renal cortex & cortex.

He-Ne laser - 632.8 nm , which when scattered by moving red cells , under went a frequency shift according to the Doppler principle.

Advantages :

It reflects vascular rather than nervous

responsiveness

recent trauma or following orthognathic surgery

Limitations :

Difficult to obtain laser reflection from certain teeth.

Differences in sensor output and inadequate calibration by the manufacturer may dictate the use of multiple probes for accurate assessment.

Values may vary i.e sometimes may not be reliable indicator due to problems

a. changes in red cell flux in gingival tissueb. changes in ambient light intensityc. movement artifacts.

IN CASES OF DEEP AND HYPERSENSITIVE CAVITIES

A REDUCTION IN THE PERMEABILITY OF THE DENTIN- ACHIEVED

BY SEALING THE DENTINAL TUBULES

LASERS USED

Nd: YAG – 2W & 20 PPS for less than one sec with black ink

CO2 laser – with silver ammonium fluoride solution

NO POST OPERATIVE PAIN

Indirect Pulpcapping:

Bloodless field

Sterilization of the treated wound

According to Paschoud and Holz, 1988 laser treatment causes direct stimulation of dentin formation

Melcer also described successful pulp restoration after direct capping of inflamed pulps with laser irradiation

Direct Pulp Capping

INDICATIONS-

Pulp exposure less than 2mm

No infection in the pulp

PROCEDURE –

1 or 2 W laser energy after alternate irrigation with 5.25% NaOCl and 3% Hydroenperoxide

Exposure site closed with Calcium hydroxide paste

SUCCESS RATE 89% DUE TO

Control of hemorrhage

Sterilization

Carbonization

LASERS USED - ND: YAG, ARGON LASER, DIODE LASER, ER: YAG, CO2 LASER

Pulpotomy & Vital Pulp Amputation

One of the most anticipated laser treatment in Endodontics

Lasers used –CO2 laser 1 to 4 W Nd:YAG for 2sec,Ga-As laser

Carbanized layer that is formed on the surface must be removed with 3%hydrozen peroxide and 5.25% of NaOCl

Shoji et al 1985 -first laser pulpotomy using CO2 laser in dogs

No damage -radicular portions of irradiated pulpsWound healing better than controls.

Wildar- Smith et al 1997 and Dang et al 1998 found CO2 laser pulpotomy to be very successful -teeth with large exposure sites, subjected to bacterial contamination for several days.

Wound healing – one week

Dentine bridge- 4 to 12 weeks

Success rate – 50%

Pulpectomy and Root canal wall preparation

Various laser systems emit energy that can be delivered into the root canal system by a thin optical fiber

Straight and slightly curved canals

Laser with air water spay

Laser tips placed 1mm short of the apex

Apical region is shaped with files and reamers

The potential bactericidal effect of laser irradiation can be used effectively for additional cleaning of the root canal system following biomechanical instrumentation

Access cavity preparation

Er:YAG – 8Hz, 2W

Pulpectomy –

Nd:YAG for 2W at 20PPs for one sec, Multiple application with 5 sec interval

Cleaning and shaping

CO2 laser with Ag(NH3)2 F of 9.3 to 10.49μm- effectively seals dentinal tubules

Nd:YAG laser with black ink

Argon lasers

Er:YAG- most effective

KTP – Potassium titanyl phosphate 532nm removes smear layer and debris

Nd:YAG laser 532nm – nanosecond pulsed, frequency doubled

Xenon chloride (XeCl) laser – 308nm seal the exposed dentinal tubules

Ar-Fluoride excimer laser- 193nm removes peritubular dentine, melting and resolidification of dentinal tubules

Ho:YAG laser – 2.10μm – ablation of dentine and for cutting the dentin

Nd:YAP –(Nd: Yttrium Aluminum Perovskite) 1340nm – effective in root canal preparation and retreatment

Free electron laser (FEL) – 2-10 μm – hydroxyapetite crystals effected

Stabholz and Colleagues 2003 developed a new endodontic tip that

can be used with an Er:YAG laser system

The beam of Er:YAG laser is delivered through a hollow tube to allow

lateral emission of the irradiation (side-firing)

This new endodontic side firing spiral tube (RC Lase) was designed to fit the shape and volume of root canal prepared by Ni-Ti rotary instruments.

Emits radiation laterally to the walls of the root canal through a spiral split The tip is sealed at its far end

Limitations of lasers in cleaning and shaping

The laser energy from the tip is directed along the root canal and not necessarily laterally to the root canal wall.

Thermal damage to the periapical tissues

Sterilization of infected root canals

Effective tools for killing micro-organisms by its bactericidal effect

Disinfection depends on

Laser wavelength and energy characteristics

Lasers used

Pulsed Nd:YAG laser 2W, 20PPS with silver ammonium fluoride solution for 5 sec – 80 to 90% sterilizationArgon lasersDiode lasers- 810nmCO2 lasersEr:YAG laserNd:YAP laser 1.34μmXe-Cl lasers – 308 nm

Photo-activated disinfection

Less toxic and alternative to chemical disinfection

It is an combination of photosensitizing dye and a laser of specific wavelength

Kills high population of bacteria

It destroys collagen, and carious dentin

Two components

PAD solution: Tolonium ChlorideSave Dent Laser -635 nm

Mechanism of action:

Photosensitiser

Reactive Oxygen sp

Disrupts membrane

Advantages

Ease of use

Disinfection

Duration -1-2 min

Toxicity

Does not affect fibroblasts or Keratino cytes

Laser is safe

Obturation of root canals

Obturation with AH –plus and composite resin activated by Argon lasers

Laser initiates photo polymerization by activation of composite resin

Argon laser, CO2 laser, Nd:YAG- soften the guttapercha –vertical compaction

Argon lasers – good apical seal

Retrograde cavity preparation and prevention

of micro leakage

Retrograde cavity preparationEr:YAG laser – 8Hz & 2W

Prevention of micro leakageSealing of dentinal tubules Nd:YAG laser 1 or 2W under air water cooling in combination with silver ammonium solution CO2 laser

Endodontic Surgery

Miserendino 1985 suggested that the rationale for laser use in endodontic periapical surgery should include :

Improved haemostasis & concurrent visualization of the operative field

Potential sterilization of the contaminated root apex

Potential reduction of the permeability of the root surface dentin

A reduction in post operative pain

A reduced risk of surgical site contamination by eliminating the use of aerosol producing air turbine hand pieces for apicosectomy

Apicosectomy

Er:YAG laser – root resection

Er,Cr:YSGG laser

CO2 laser

Sterilization of endodontic instruments

Argon lasers

CO2 lasers

Nd:YAG lasers

Removal of calcified attached denticles

Pulsed dye lasers -504nm

CONCLUSION

A PROPER AND SUCCESSFUL USE OF LASERS IN

ENDODONTICS IS DEPENDS ON THE UNDERSTANDING OF

CHARACTERISTICS AND THEIR LIMITATIONS . LACK OF

UNDERSTANDING OFTEN LEADS TO THE MISUSE AND ABUSE

OF LASERS, CAUSING DETRIMENTAL RESULTS