GITAM DENTAL COLLEGE & HOSPITAL

DEPARTMENT OF ORAL & MAXILLOFACIAL SURGERY

SEMINAR ON LASERS IN ORAL &

MAXILLOFACIAL SURGERY

Presented By: Dr. Sambhav K Vora

II. MDS

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CONTENTS-

1. Introduction

2. History of lasers

3. Laser physics

4. Laser design

5. Focusing

6. Laser types- Carbon-di-oxide laser Nd:YAG laser Argon laser Er:YAG laser Ho:YAG laser

7. Interactions with biologic tissues

8. Laser effect on dental tissues

9. Lasers in Preneoplasia of oral cavity

10. Lasers for soft tissue excision

11. Skin resurfacing in the aesthetic zone

12. Resection of the cancer

13. Laser assisted uvulopalatoplasty

14. Lasers in laryngeal surgery

15. Laser hazards & safety

16. Conclusion

17. References

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Introduction

Laser is an acronym, which stands for light amplification by stimulated emission of radiation. Several decades ago, the laser was a death ray, the ultimate weapon of destruction, something you would only find in a science fiction story. Then lasers were developed and actually used, among other places, in light shows. The beam sparkled, it showed pure, vibrant and intense colors. Today the laser is used in the scanners at the grocery store, in compact disc players, and as a pointer for lecturer and above all in medical and dental field. The image of the laser has changed significantly over the past several years.

With dentistry in the high tech era, we are fortunate to have many technological innovations to enhance treatment, including intraoral video cameras, CAD-CAM units, RVGs and air-abrasive units. However, no instrument is more representative of the term high-tech than, the laser. Dental procedures performed today with the laser are so effective that they should set a new standard of care.

This presentation intends to discuss the role of lasers in dentistry.

History of Lasers

Approximately, the history of lasers begins similarly to much of modern physics, with Einstein. In 1917, his paper in Physikialische Zeil, “Zur Quantern Theorie der Strahlung”, was the first discussion of stimulated emission.

In 1954 Townes and Gordon built the first microwave laser or better known as ‘MASER’ which is the acronym for ‘Microwave Amplification by stimulated Emission of Radiation’

In 1958, Townes, working with Schawlow at Bell Laboratories, published the first theoretic calculations for a visible light maser – or what was then called a LASER.

In May 1960, Theodore Maimen at Hughes Aircraft company made the first laser. He used a ruby as the laser medium.

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One of the first reports of laser light interacting with tissue was from Zaret; he measured the damage caused by lasers incident upon rabbit retina and iris.

The first gas laser was developed by Javan et al in 1961. This was the first continuous laser and used helium – neon.

The Nobel Prize for the development of the laser was awarded to Townes, Basor and Prokhovov in 1964.

The neodymium – doped (Nd): glass laser was developed in 1961 by Snitzer.

In 1964 Nd: YAG was developed by Geusic.

The CO2 laser was invented by Patel et al in 1965.

In 1968 Polanyi developed articulating arms to deliver CO2 laser to remote areas.

Polanyi in 1970 applied CO2 laser clinically.

In 1990 Ball suggested opthalmologic application of ruby laser.

Laser Physics2

Laser is a device that converts electrical or chemical energy into light energy.

In contrast to ordinary light that is emitted spontaneously by excited atoms or molecules, the light emitted by laser occurs when an atom or molecule retains excess energy until it is stimulated to emit it. The radiation emitted by lasers including both visible and invisible light is more generally termed as electromagnetic radiation. The concept of stimulated emission of light was first proposed in 1917 by Albert Einstein.

He described three processes:

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1. Absorption2. Spontaneous emission3. Stimulated emission.

Einstein considered the model of a basic atom to describe the production of laser. An atom consists of centrally placed nucleus which contains +vely charged particles known as protons, around which the negatively charged particles. i.e. electrons are revolving.

When an atom is struck by a photon, there is an energy transfer causing increase in energy of the atom. This process is termed as absorption. The photon then ceases to exist, and an electron within the atom pumps to a higher energy level. This atom is thus pumped up to an excited state from the ground state.

In the excited state, the atom is unstable and will soon spontaneously decay back to the ground state, releasing the stored energy in the form of an emitted photon. This process is called spontaneous emission.

If an atom in the excited state is struck by a photon of identical energy as the photon to be emitted, the emission could be stimulated to occur earlier than would occur spontaneously. This stimulated interaction causes two photons that are identical in frequency and wavelength to leave the atom. This is a process of stimulated emission.

If a collection of atoms includes, more that are pumped into the excited state that remain in the resting state, a population inversion exists. This is necessary condition for lasing. Now, the spontaneous emission of a photon by one atom will stimulate the release of a second photon in a second atom, and these two photon will trigger the release of two more photons. These four than yield eight, eight yield sixteen and so on. In a small space at the speed of light, this photon chain reaction produces a brief intense flash of monochromatic and coherent light which is termed as ‘laser’.

Properties of Laser11

1. Coherent: Coherence of light means that all waves are in certain phase relationship to each other both in space and time

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2. Mono- chromatic: Characterized by radiation in which all waves are of same frequency and wavelength.

3. Collimated: That means all the emitted waves are parallel and the beam divergence is very low. This property is important for good transmission through delivery systems.

4. Excellent concentration of energy: When a calcified tissue for eg. dentin is exposed to the laser of high energy density, the beam is concentrated at a particular point without damaging the adjacent tissues even though a lot of temperature is produced ie 800-900oC.

5. Zero entropy.

Laser Design

The laser consists of following components.

1. A laser medium or active medium: This can be a solid, liquid or gas. This lasing medium determines the wavelength of the light emitted from the laser and the laser is named after the medium.

2. Housing tube or optical cavity:

Made up of metal, ceramic or both.

This structure encapsulates the laser medium.

Consists of two mirrors, one fully reflective and the other partially transmittive, which are located at either end of the optical cavity.

3. Some form of an external power source: This external power source excites or “pumps” the atom in the laser medium to their higher energy levels. A population inversion happens when there are more atoms in the excited state rather than a non-excited state. Atoms in the excited state spontaneously emit photons of light which bounce back and forth between the two mirrors in the laser tube, they strike other atoms, stimulating more

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spontaneous emission. Photons of energy of the same wavelength and frequency escape through the transmittive mirror as the laser beam. An extremely small intense beam of energy that has the ability to vaporize, coagulate, and cut can be obtained if a lens is placed in front of the beam. This lens concentrates the emitted energy and allows for focussing to a small spot size.

Laser Light Delivery

Light can be delivered by a numbered of different mechanisms. Several years ago a hand held laser meant holding a larger, several hundred pound laser usually the size of desk above a patient. Although the idea was comical at the time, it is becoming more feasible as laser technology is producing smaller and lighter weight lasers. In the more future it is probable that hand held lasers will be used routinely in dentistry.

1. Articulated arms

Laser light can be delivered by articulated arms, which are very simple but elegant. Mirrors are placed at 45o angles to tubes carrying the laser light. The tubes can rotate about the normal axis of the mirrors. This results in a tremendous amount of flexibility in the arm and in delivery of the laser light. This is typically used with CO2 laser. The arm does have some disadvantages that include the arm counter weight and the limited ability to move in straight line.

2. Optical Fiber

Laser light can be delivered by an optical fiber, which is frequently used with near infrared and visible lasers. The light is trapped in the glass and propagates down through the fiber in a process called total internal reflection.

Optical fibers can be very small. They can be either tenths of micros or greater than hundreds of microns in diameter. Advantages of optical fiber is that they provide easy access and transmit high intensities of light with almost no loss but have two disadvantages, one the beam is no longer collimated and coherent when emitted from the fiber which limits the focal spot size and second disadvantage is that the light is no longer coherent.

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Patient to laser

Another method of delivering laser light to the patient is actually to bring the patient up to the laser. Eg: Slit lamp used in the ophthalmologist gist has been doing this for quite some time. The ophthalmic laser microscope is simply a slit lamp with a laser built into it. The doctor simply images what he wants on the cornea or retina and then pushes the foot pedal to deliver laser beam to the target.

Once the laser is produced, its output power may be delivered in the following modes.

1. Continuous wave: When laser machine is set in a continuous wave mode the amplitude of the output beam is expressed in terms of watts. In this mode the laser emits radiation continuously at a constant power levels of 10 to 100 w. Eg: CO2 laser

2. Gated: The output of a continuous wave can be interrupted by a shutter that “chops” the beam into trains of short pulses. The speed of the shutter is 100 to 500ms.

3. Pulsed: Lasers can be gated or pulsed electronically. This type of gating permits the duration of the pulses to be compressed producing a corresponding increase in peak power, that is much higher than in commonly available continuous wave mode.

4. Super pulsed: The duration of pulse is one hundredth of microseconds.

5. Ultra pulsed: This mode produces an output pulse of high peak power that is maintained for a longer time and delivers more energy.

6. Q-scotched: Even shorter and more intense pulse can be obtained with this mode.

Focussing

Lasers can be used in either a focussed mode or in a defocused mode.

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A focussed mode is when the laser beam hits the tissue at its focal points or smallest diameter. This diameter is dependent on the size of lens used. This mode can also be referred as cut mode. Eg. While performing biopsies.

The other method is the defocused mode. By defocusing the laser beam or moving the focal spot away from the tissue plane, this beam size that hits the tissue has a greater diameter, thus causing a wider area of tissue to be vaporized. However, laser intensity / power density is reduced. This method is also known as ablation mode. Eg. In Frenectomies. In removal of inflammatory papillary hyperplasias.

Contact and Non contact modes

In contact mode, the fiber tip is placed in contact with the tissue. The charred tissue formed on the fiber tip or on the tissue outline increases the absorption of laser energy and resultant tissue effects. Char can be eliminated with a water spray and then slightly more energy will be required to provide time efficient results. Advantage is that there is control feed back for the operator.

Non contact mode: Fiber tip is placed away from the target tissue. The clinician operates with visual control with the aid of an aiming beam or by observing the tissue effect being created.

So generally laser can be classified as

Dental Lasers

Those work in

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both

Solely in the non Contact & focussed Non contact contact mode

& defocused

Eg: CO2 Eg: Agon, HO : YAG, Nd:YAG

Laser Types

I. Based on wavelength.

1. Soft lasers2. Hard lasers

II. Based on the type of active / lasing medium used

1. ArF excimer2. KrF excimer3. XeCl excimer4. Argon ion5. KTP6. Ruby7. Nd: YAG8. HO: YAG9. YSGG10. Er: YAG11. CO2

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I.

1. Soft Lasers: With a wave length around 632mm Soft lasers are lower power lasers.

Eg: He Ne, Gallium arsenide laser.

These are employed to relieve pain and promote healing eg. In Apthous ulcers.

2. Hard lasers: Lasers with well known laser systems for possible surgical application are called as hard lasers.

Eg: CO2, Nd: YAG, Argon, Er:YAG etc.

CO2 Lasers5

The CO2 laser first developed by Patel et al in 1964 is a gas laser and has a wavelength of 10,600 nanometers or 10.6 deep in the infrared range of the electromagnetic spectrum.

CO2 lasers have an affinity for wet tissues regardless of tissue color.

The laser energy weakens rapidly in most tissues because it is absorbed by water. Because of the water absorption, the CO2 laser generates a lot of heat, which readily carbonizes tissues. Since this carbonized or charred layer acts as a biological dressing, it should not be removed.

They are highly absorbed in oral mucosa, which is more than 90% water, although their penetration depth is only about 0.2 to 1mm. There is no scattering, reflection, or transmission in oral mucosa. Hence, what you see is what you get.

CO2 lasers reflect off mirrors, allowing access to difficult areas. Unfortunately, they also reflect off dental instruments, making accidental reflection to non-target tissue a concern.

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CO2 lasers cannot be delivered fiber optically Advances in articulated arms and hollow wave guide technologies, now provide easy access to all areas of the mouth.

Regardless of the delivery method used, all CO2 lasers work in a non-contact mode.

Of all the lasers for oral use, CO2 13is the fastest in removing tissue.

As CO2 lasers are invisible, an aiming helium – neon (He Ne) beam must be used in conjunction with this laser.

Nd: YAG Laser: Here a crystal of Yttrium – aluminum – garnet is doped with neodymium. Nd: YAG laser, has wavelength of 1,064 nm (0.106 ) placing it in the near infrared range of the magnetic spectrum.

It is not well absorbed by water but are attracted to pigmented tissue. Eg: hemoglobin and melanin. Therefore various degrees of optical scattering and penetration to the tissue, minimal absorption and no reflection.

Nd: YAG lasers work either by a contact or non-contact mode. When working on tissue, however, the contact mode in highly recommended.

The Nd: YAG wavelength is delivered fiber optically and many sizes of contact fibers are available. Carbonized tissue remains often build of on the tip of the contact fiber, creating a ‘hot tip’. This increased temperature enhances the effect of the Nd:YAG laser, and it is not necessary to rinse the build up away. Special tips, the coated sapphire tip, can be used to limit lateral thermal damage. A helium-neon-aiming beam is generally used with Nd: YAG wavelength.

Penetration depth is ~ 2 to 4m, and can be varied by upto 0.5-4mm in oral tissues by various methods.

A black enhancer can be used to speed the action.

Most dental Nd: YAG lasers work in a pulsed mode. At higher powers and pulsing, a super heated gas called a plasma can form on the tissue surface.

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It is the plasma that can be responsible for the effects of either coagulation, vaporization or cutting. If not cooled (e.g. by running a water stream down the fiber) the plasma can cause damage to the surrounding tissues.

Suffer from dragability

The Nd:YAG beam is readily absorbed by amalgam, titanium and non-precious metals, requiring careful operation in the presence of these dental materials.

Argon Lasers

Argon lasers are those lasers in the blue-green visible spectrum.

They operate at 488nm or 514.5nm, are gas like CO2 lasers and are easily delivered fiber optically like Nd:YAG.

Argon lasers have an affinity for darker colored tissues and also a high affinity for hemoglobin, making them excellent coagulators. It is not absorbed well by hard tissue, and no particular care is needed to protect the teeth during surgery.

In oral tissues there is no reflection, some absorption and some scattering and transmission.

Argon laser: end point is "whitening" of lesion.

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Argon lasers work both in the contact and non contact mode

Like, Nd: YAG lasers, at low powers argon lasers suffer from ‘dragability’ and need sweeping motion to avoid tissue from accumulating on the tip.

Enhances are not needed with Argon lasers.

Argon lasers also have the ability to cure composite resin, a feature shared by none of the other lasers.

The blue wavelength of 488 nm is used mainly for composite curing, while the green wavelength of 510nm is mainly for soft tissue procedures and coagulation.

Er: YAG laser

Have a wavelength of 2.94 m.

A number of researchers have demonstrated the Er: YAG lasers ability to cut, or ablate, dental hard tissue effectively and efficiently. The Er: YAG laser is absorbed by water and hydroxyapatite, which particularly accounts for its efficiency in cutting enamel and dentin.

Pulpal response to cavity preparation with an Er: YAG laser was minimal, reversible and comparable with pulpal response created by a high-speed drill.

Ho: YAG laser [Holmium YAG lasers]

Has a wavelength of 2,100 nm and is a crystal

Delivered through a fiber optic carrier.

A He-Ne laser is used as an aiming light

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Dragability is less compared to Nd: YAG and argon lasers

Like Nd: YAG, can be used in both the contact and non-contact modes and are pulsed lasers.

Ho: YAG laser has an affinity for white tissue and has ability to pass through water and acts as a good coagulator.

Laser interaction with biologic tissues

Light can interact with tissues in four different mechanisms

1. Reflected 2. Scattered3. Absorbed4. Transmitted

Reflection: Reflected light bounces off the tissue surface and is directed outward. Energy dissipates after reflection, so that there is little danger of damage to other parts of mouth and it limits the amount of energy that enters the tissue.

Scattering: occurs when the light energy bounces from molecule to molecule within the tissue. It distributes the energy over a larger volume of tissue, dissipating the thermal effects.

Absorption: occurs after a characteristic amount of scattering and is responsible for the thermal effects within the tissue. It converts light energy to heat energy The absorption properties of tissue and cells depends on the type and amount of absorbing pigments or chromophores. Eg. Hemoglobin, water, Melanin, Cytochromes etc.

Transmission: Light can also travel beyond a given tissue boundary. This is called transmission. Transmission irradiates the surrounding tissue and must be quantified. Its effects should be considered before laser treatment can be justified.

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Tissue effects on laser irradiation

When radiant energy is absorbed by tissue 4 basic types of interactions occurs.

Laser effects on Dental Hard Tissues

The absorption and transmission of laser light in human teeth is mainly dependent on the wavelength of the laser light.

For eg. – Ultraviolet laser light is well absorbed by teeth.

In water and in hydroxyapatite, there is a very low absorption at a wavelength of 2m in comparison to high absorption of laser energy at 3m and 10m.

The laser effects can be grouped as:

1. Thermal effects:

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The best known laser effect in dentistry is the thermal vaporization of tissue by absorbing laser light i.e. the laser energy is converted into thermal energy or heat that destroys the tissues.

From 45o – 60 o denaturation occurs >60 o coagulation and necrosisAt 100 o C water inside tissue vaporizes>300 o C carbonization and later hydrolysis with

vaporization of bulky tissues.

2. Mechanical effects:

High energetic and short pulsed laser light can lead to a fast heating of the dental tissues in a very small area. The energy dissipates explosively in a volume expansion that may be accompanied by fast shock waves. These shock waves lead to mechanical damage of the irradiated tissue.

3. Chemical effects:

Here molecules can be associated directly with laser light of high photon energies.

Histologic Results:

With continuous wave and pulsed CO2 lasers.

When continuous wave and pulsed CO2 lasers were used, structural changes and damage in dental hard tissue were reported. Microcracks and zones of necrosis and carbonization are unavoidable. Because of drying effects, the microhardnes of dentin increases. The crystalline structure of hydroxyapatite changes and a transformation of apatite to tricalcium phosphate takes place.

Nd: YAG Lasers:

The Nd: YAG laser shows low absorption in water as well as in hydroxyapatite. Therefore the laser power diffuses deeply through the enamel and dentin and finally heats the pulp. In dentin, at the laser impact, zones of

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debris and carbonization are surrounded by an area of necrosis can be seen. Microcracks appear when energies above a threshold of 100mj / pulse are used. But the appearance and the extent of the side effects are not predictable.

Er: YAG Laser:

In dentin, shallow cavities were surrounded by a zone of necrosis of 1-3m thickness when water-cooling systems were used. In deeper cavities areas of carbonization and microcracks were observed. Ablating enamel always cracked and deep zones of debris appeared.

Excimer Lasers:

No pathologic changes in the tissue layers adjacent to the dissected areas were found after the ablation.

The ablation effects of dental hard tissues are predictable. Compared to conventional diamond and burs, however, the effectiveness is low. Thermal side effects increase as photon energies of excimer lasers decrease.

Laser Effects on Dental Pulp:

Recent histologic evidence suggests that a normal odontoblasts layer, stroma and viable epithelial root sheath can be retained following laser radiation provided damage threshold energy densities are not exceeded. If pulp temperatures are raised beyond the 5°C level, research has shown that the odontoblasts layer may not be present. Characteristics of the dentinogenesis process related to root development, predentin and reparative dentin formation, dentinal bridge presence, typically reflect the overall trauma that has been induced in the odontoblasts.

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Application of Lasers in Dentistry:

Application Possible Laser Types

Basic research

Laser tissue interaction

Technical development of applications

of lasers in dentistry

All types

All types

Measurement and diagnosis

Holography

Laser Doppler fowmetry

Spectroscopy (caries diagnosis)

He Ne, diodes

He Ne, diodes

Various types

Oral and Maxillofacial Surgery

Cutting and Coagulation

Photodynamic therapy

CO2, Nd: YAG, Ar, dye

Dye, Au-Cu vapour

Conservative dentistry

Preventive dentistry (fissure sealing)

Caries treatment

Composite resin light Curing

Tooth surface conditioning

CO2, Nd:YAG, ruby

CO2, Nd:YAG, Er: YAG, Excimer

Ar, dye, HeCd

Excimer, CO2, Nd:YAG, Er:YAG

Endodontics

Root canal treatment

Apicoectomy

Nd: YAG, CO2, Excimer

CO2, Nd:YAG

Periodontics

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Laser sealing of affected root surfaces

Excision of gingival soft tissues

CO2, excimer

CO2

Analgesic effect and bio-stimulation

Stimulation of wound healing

Low power laser radiation with analgesic

Effects

He Ne, diodes

Nd: YAG

Other applications:

Laser processing of dental materials

Welding of dental alloys

Cobalt – chrome – molybdinum Nickel – chrome – aluminum Silver PalladiumTitanium alloys

Welding of ceramic materials

Still under investigation

Advantages of laser welding:

1. High bond strength and corrosion resistance since laser welding is a form of sweating that does not use solders of different materials.

2. Reduced oxidation when argon gas is used for welding.

3. Decreased thermal influence and greater precision in processing than with soldering or other techniques.

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Lasers in Surgical Systems:

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Lasers are an alternative to conventional surgical systems. Stated best by Apfelberg in 1987, lasers are a “new and different scalpel” (optical knife, light scalpel).

Advantages:

Easy access to the anatomic site

Possess inherent hemostatic properties.

Capable of ablation of lesions in proximity to normal structures, with minimal damage to normal structures.

Reduced pain during surgical procedures and less post operative pain.

Enhanced healing

Bactericidal and virucidal effects of laser result in decreased rates of wound infection.

Certain proven uses for dental soft tissue procedures using lasers are:

1. Frenectomy

Maxillary midlineLingual (Tongue tie)

2. Incisional and exasional biopsies.3. Removal of benign lesions

FibrousPapillousPyogenic granulomaLichen PlanusErosive lichen planusNicotinic stomatitesVerruca vulgarisInflammatory papillary hyperplasia

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Epuli

4. Gingivoplasty5. Soft tissue tuberosity reduction.6. Soft tissue distal wedge procedure.7. Gingivectomy

A. Removal of hyperplasias1. Dilantin etc2. Idopathic

B. Crown trough.

8. Aphthous ulcer

9. Operculectomy

10. Removal of hyperkeratotic lesions

11. Removal of malignant lesions

12. Soft tissue crown lengthening

13. Coagulation.A. Graft donor sites.B. Seepage around crown preparation.

14. Vestibuloplasty

15. Removal of granulation tissue – periodontal clean out

16. Removal of vascular lesionsA. Hemangioms

B. Pyogenic granuloma

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17. Removal of lesion in patients with hemorrhagic disorders.A. Hemophelia etc.

18. Implants – Stage II – at the time of recovery.

A. Soft tissue removal

Lasers in Preneoplasia of the oral cavity-

Successful treatment of superficial mucosal disease of the oral cavity mandates selective ablation of the abnormal epithelium including the parabasal layer attached to the basement membrane. The carbon dioxide laser does not impart magical properties to the tissues, but it does provide a selective therapeutic advantage for the treatment of intramucosal Preneoplasia by avoiding damage to subjacent tissue, thereby eliminating scar formation and the creation of oral deformities. Preneoplastic lesions of the oral mucosa include leukoplakia6, erythroplakia, and oral submucous fibrosis, with 85% of the preneoplasias being accounted for by leukoplakia.

SURGICAL TREATMENT: C 0 2 LASER12

Conventional surgical treatment, which consists of excision with a scalpel, is successful and adequate for limited local disease. The literature reports control rates of around 90 % .Failure becomes likely when this local treatment is applied to extensive disease. Because the multicentric nature of precancer (the condemned mucosa concept) manifests itself as multifocal disease by occurring at multiple sites in the oral cavity and oropharynx, a more global treatment concept than local excision is required. Failure rates following local surgical excision are as high as 33%.4 Muliicentricity demands excision of topographically large areas of mucosa. However, the denudation of large areas of oral mucosa results in scarring and wound contraction as well as postoperative pain, edema, and nutritional depletion. Despite the greatest care, the minimum thickness of tissue removed with a scalpel results in exposure and removal of the submucosa. Both scarring and incomplete epithelial regeneration occur. The traditional solution to this problem is to replace the mucosa with a split-thickness skin graft. This, however, is an unsatisfactory solution because skin dews not function as well as mucosa. The graft ultimately contracts as time passes, and the grafted skin covers remaining elements of regenerated mucosa that may be unstable. Lastly, even for local

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treatment, site-specific consequences may dictate against locally invasive surgery that induces scarring. For example, removal of the thinnest layer of mucosa over the opening of Wharton's or Stensen's duct may cause scarring, glandular obstruction, and infection. Excision of large lesions at the oral commissure causes deformity of the oral stoma. The advantage of replacing traditional excisional techniques with C 0 2 laser photoablation is that the laser permits removal of the damaged epithelium with as little as 0.1 to 0.2 mm of reversible thermal injury to the submucosa. Precise control of thermal damage makes it possible to remove even the epithelium directly over the salivary ductorifices without inducing sialodochitis and glandular obstruction. Extensive areas of mucosa may be ablated without skin grafting because epithelium isregenerated from normal tissue at the wound periphery in no more than 5 weeks for lesions as large as 40 cm2 . After healing, the mucosa al risk is still observable by direct visual inspection during recall examination. Of equal importance, there is little postoperative swelling and patients may take oral fluids immediately after surgery. These patients may be operated upon as outpatients, and there is usually no bleeding or swelling. Pain, which is highly variable, is easily managed with oral analgesics, rarely lasts more than a few days, and only occasionally shows a secondary increase in intensity on days 3 to 5, which then abruptly terminates.

SURGICAL TECHNIQUE-The oral mucosa is assessed and the requisite biopsies are obtained in the manner previously described. At the time of laser surgery, the vital staining is repeated. Local anesthesia is used unless the patient receives a general anesthetic. No pre- or perioperative antibiotics are given and no antiseptic

preparation solution is used for the mouth. The face is protected with wet surgical drapes and the eyes are covered. If endotracheal intubation is utilized, the hypopharynx is packed with a wet gauze. After identifying the extent of the pathology, the laser is set at an average power of 20 to 30 W for pulsed modes, and 15 to 20 W for CW mode. The spot size will vary between 2 and 3

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mm in diameter. The clinical end point for ablation of the mucosa is to cause a "rapid bubbling of the epithelium which is opalescent in color and is accompanied by a crackling noise."2 1 The lesion is outlined with a suitable margin of several millimeters and then parallel lines of application of the laser are placed within the marginal outline This is called rastering. After completion of this first layer of lasing, there should be almost no carbonization. If the wound appears blackened, there has been excessive heat conduction because of prolonged contact between the laser beam and the tissue as a result of excessively slow hand speed in moving the handpiece or microscope joystick-directed laser beam across the lesion. The more heat conducted, the greater the desiccation occurring at surgery. A moist gauze is now used to wipe away the treated area of mucosa. This allows one to assess the depth of penetration of the laser. A pale pink base that does not bleed indicatesremoval of the epithelium at the level of the basement membrane . If there are scattered droplets of blood, then the superficial aspect of the submucosal plane has been breached. If the depth of penetration is too superficial, a second raster is applied to reach the required depth, which results in removal of the entire thickness of the epithelium. In areas of thick hyperplasia as for nicotine stomatitis or fibroepithelial hyperplasia ofthe palate ,several layers of rastering may be required. The submucosal layer is identified both by the appearance of blood vessels and by the appearance of tissue of granular appearance and yellow color. At the conclusion of surgery the abnormal (issue has been removed and there should be no bleeding except where it was necessary to extend tissue removal into the submucosa. as may be required in this case of papillary hyperplasia of the palate where four rasters are needed for complete tissue removal. The fibrin coagulum that formed within the first 24 hours is still present at one week. Complete mucosal reepithelialization and healing has occurred within 5 weeks

Lasers for soft tissue excision-

FIBROEPITHELIAL POLYP-

The polyp arising from the dorsal midline of the anterior tongue was both interfering with suckling and causing consternation for the parents and the

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pediatrician. At approximately 7 weeks of age the patient was brought to the operating room where, using general anesthesia delivered by an oral endotracheal tube and without supplemental local anesthesia, the polypwas bloodlessly removed in one minute of operating time. Laser parameters were handheld CO: rapid superpulsed laser at 50 pps. evaporative spot si/.e of 0.3 mm, average power output of 10 W

EAR TAG-

Skin tags occasionally occur in newborns as well as adults. In this illustrative case a consultation was received from the newborn nursery to remove an ear tag. Otologic and auditory examinations were normal. The baby was brought to the laser lab where he was first fed. Then, after falling asleep the base of the lesion was inliltrated with 0.25 mL of 2% lidocaine. The lesion was then removed with the superpulsed CO, laser at 6 W average output power, 0.3-mm spot size using a handpiece at 118 pps. The operation required less than a minute and there was no blood loss

EXPOSURE OF IMPACTED TEETH-

Although exposure of impacted teeth (soft tissue impaction) is easily accomplished in the dental operatory using local anesthesia and a loop cautery, there is less swelling, less postoperative pain, and less chance of thermal injury to the exposed tooth if the free beam C 0 2 or the contact heodymium:yttrium-aluminum-garnet (Nd:YAG) laser is used.The C 0 2 laser may be used at PD of approximately 10,000 W/cm2 at 50 PPS, 10 W average output power and 0.3 mm spot size to incise around the impacted crown of the tooth. As dissection proceeds, the mucosal flap is elevated. Mucosa well healed at 3 weeks. Bonded bracket ready to be used to start tooth movement. with tissue forceps until the underlying crown is identified. At this point, the handpiece is moved away from the tissue to

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diminish PD, thereby permitting dissection of the mucosa away from the crown without marring.Ihe enamel surface from inadvertent laser strikesat high PD. Alternatively, the Nd.YAG laser in contact mode using a shortscalpel tip at 5 to 10 W average output power is used to excise the gingival cuff. Rapid identification of the crown permits the operator to avoid inadvertently damaging it by excessive heating from the scalpel tip.There is no bleeding.

HEMANGIOMAS AND VASCULARMALFORMATIONS-Hemangiomas in the oral cavity are most effectively treated with the argon laser by direct application after compressing the lesion with a glass slide or for

larger lesions by intralesional introduction of the liber. Large,higher-flow lesions are occasionally treated with the Nd:YAG laser. However, small, localized, low-flow lesions may be excised with the C 0 2 laser. A small vascular malformation of the labial sulcus was excised with the C 0 2 laser.

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GINGIVAL HYPERTROPHY-Key elements of laser technique for gingivoplasty include the use of a superpulsed CO: laser with the handpiece at a PD of 500 to 625 W/cm2 by varying the spot size between 2.0 and 2.5 mm at 58 pps 600 mJ/pulse at an average power output of 25 W. A matrix band is secured around the cervical margin of the tooth below the free margin of the gingiva to protect the enamel and cementum from injury by the laser beam. Gingiva removed by each raster is wiped away to remove the carbonization prior to applying additional rasters with the laser.

FACIAL NEVI-Vaporization technique with rapid super pulsed (RSP) C 0 2 laser was chosen to reduce scarring. Laser parameters: RSP C 0 2 laser (110 mJ/pulse) at 108 pps using the microscopic and microslad system. The laser spot size was 2.0mm at an output power of 15 W and a PD of approximately 450 W/cm2 . The target site was anesthetized by infiltration of 1% lidocaine local anesthetic. No skin preparation was performed . Two raster’s were administered under 10X magnification and the surface of the target tissue was debrided with a wet gauze sponge after the first and second raster. One year later there was only a faint depression at the treatment site and there was no change in skin color.

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SKIN RESURFACING IN AESTHETIC SURGERY-Skin wrinkles, or rhylidcs from excessive sun exposure, particularly those occurring on and around the lips and eyes, may be reduced by treatment with the COs laser using an automated scanner such as the SilkTouch flash-scanner.The wrinkle is treated by ablating the area adjacent to the deepest point of the wrinkle fold with the laser set at 7 W average output power in the pulsed mode at 0.2-s cycles. This permits assessment of the laser effect after completion of a single cycle (one complete revolution of the flash scanner within its target circle). As always, the target tissue is removed with a saline moistened gauzesponge. Pending the area to be treated,a second and third pass may be necessary to penetrate into or through the papillary dermis. Alternatively, a Computer Pattern Generator (Coherent Lasers) can be used with an ultrapulseC 0 2 laser at 175 to 300 mJ/pulse and an average power of between 60 and 100 W. Benign cutaneous growths and atrophic scars and pits can be treated similarly. Postoperative results are consistently good. C02 lasers resurfacingwith Coherent Ultrapulse 5000C CPG scanner at 225 ml, 60W. with one pass at moderate density over lower lid and 2-3 passes over lateral and infraorbital/malar areas.

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EPULIS FISSURATUM-Epulis fissuratum, which consists of hyperplastic mucogingival folds from fibroepithelial proliferation secondary to ill-fitting dentures, prevents proper denture seating on a stable base. It responds well to laser excision with minimal postoperative discomfort and swelling. In this case, a defo cused beam at 5 to 10 W CW is used to aid hemostasis and promote a dry field. Alternatively, a pulsed waveform at 20 W, PRR = 50-200 pps at 2.0 to 3.0-mm spot size may be used. The existing denture is relined with soft dentureliner. The wound re-epithelializes in about 3 weeks with little loss or no loss of sulcus depth

Lasers in resection of the cancers-

Transoral resection of stages I and II oral cancer is a well-accepted treatment method in oncologic surgery. The specific surgical technique is less important than is the sound application of oncologic principles to achieve adequate resection of the tumor. The gold standard for outcome is

the result achieved by scalpel resection. Any other technique such as electrosurgery, cryosurgery, or laser surgery must produce comparable or improved cure rates. Cure rates achievable with the surgical laser match those

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attributed to scalpel or electrosurgery, and also provide the significant advantages of better hemostasis, less postoperative edema, shorter hospital stay, diminished infection rates, and elimination of the need for split-thickness skin grafting. Inaddition, in theory, because of the laser's ability to seal small blood vessels and lymphatics, there is a reduced likelihood of inducing tumor microemboli during surgical extirpation of the tumor, which in turn reduces the chances of"seeding" the surgical site or the vascular or the lymphatic system. Compared with patients having stages I and II oral cavity tumors that were treated by conventional surgery using transoral resection technique, the laser-treated cases did not show increased local recurrence or regional metastases.

The most important negative aspect to consider in evaluating laser surgery is whether the laser beam itself might have any tumor-promoting effects that might enhance recurrence or spread to loco-regional or distant sites. Becausethe beam is applied only to clinically normal tissue at the resection margin and not on the tumor itself, any enhancement of spread would be expected to be a consequence of direct handling of the neoplastic tissue by retraction instruments. This being the case, one would not expect to find a diminished control rate with laser use and, in fact, the literature does not support such a negative outcome in surgical laser treatment of human oral malignancies

Laser assisted uvulopalatoplasty-The laser-assisted uvulopalatoplasty (LAUP) is a surgical technique designed to correct breathing abnormalities during sleep that result in snoring or mild to moderate obstructive sleep apnea syndrome. This is a short operation performed in the office using local anesthesia and a surgical laser. The objective is to reduce pharyngeal airway obstruction by reducing tissue volume in the uvula, the velum, and the superior part of the posterior pharyngeal pillars.contraindications to LAUP are severe maeroglossia and morbid obesity with hypopharyngeal obstruction at the tongue base. In the rare condition of floppy epiglottis, LAUP is also not of benefit.The C 0 2 laser or contact neodymium:yttrium- aluminum-garnet (Nd:YAG) laser is preferred to the use of the Nd:YAG fiber-delivered laser in this procedure because of the low volume of absorption of the C 0 2 laser beam or contact Nd:YAG in tissue. This property prevents excessive thermal necrosis of the target tissue. The YAG laser also does not have a backstop, although this problem is eliminated for contact YAG lasers. An additional advantage of the C 0 2 laser is its use as a "no-touch" technique, thereby eliminating contact

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with the palate and pharyngeal walls. This property reduces gagging, especially for the hypersensitive individual whose gagging occurs on a psychological basis despite having adequate anesthesia at the surgical site.

LAUP is performed with a free-beam CO, laser with a backstop. Beam guidance is provided by a coaxial helium neon (HeNe) laser. Standard C O : laser safety precautions have to be followed. The output power is set at 20 to 30 W average power in a pulsed mode, depending on the thickness of tissue that is to be incised. A specific snoring handpiece is used with a variable spot size of 0.6 to 3.51 mm at a focal length of 300 mm. This handpiece has a focus-defocus ring: focus to cut. and defocus to coagulate

This procedure can be done in Single stage procedure Multiple stage procedure

Lasers in laryngeal surgery-Laryngeal papillomas are cauliflower-like lesions caused by infection with the human papilloma virus (HPV). This lesion is the most common benign neoplasmof the larynx. During infancy or adulthood its presenting symptoms are hoarseness or airway obstruction. The natural history of this disease is one of multiple recurrences, especially with the juvenile onset type co laser vaporization of these lesions, although the accepted procedure

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of choice today, is thought to be only palliative in most cases. Multiple recurrences are thought to be caused by persistent growth of HPV in subclinically infected normal-appearing tissue bordering the area of treatment. The goal of laser vaporization is to eradicate this lesion and establish an adequate airway and functional voice without causing submucosal damage that may result in vocal fold scarring and fibrosis. Simultaneous removal of papillomas from both sides of the anterior or posterior commissure should be avoided, as this maneuver always results in commissure web formation. Typical co laser settings for such a procedure includes using a 025mm spot size at a working distance of 400 mm, 2- to 3-W power & 0.5 to 1.0 second pulse duration.

LARYNGEAL AND SUBGLOTTIC HEMANGIOMAS

Hemangiomas are uncommon neoplasms that may occur anywhere in the larynx and histologically are capillary, cavernous, or mixed capillary/cavernous lesions. They may present in a pediatric or adult form; the pediatric form is predominantly capillary in nature and the adult form more often mixed or cavernous. The pediatric hemangioma characteristically presents shortly after birth, has a proliferative phase that may last up to 1 year followed by an involutional phase occurring from 1 to 7 years of age. These lesions often occur subglottically and may progress in size, resulting in airway obstruction.co laser treatment may be used safely to remove these lesions while simultaneously maintaining a patent airway and thereby avoiding need for a tracheotomy.'' With the use of a subglottoscope and a laser with increased pulse duration settings to allow for more thermal diffusion and better coagulation of small vessels, capillary hemangiomas may be effectively treated. These lesions can be managed using a laser with a 0.25-mm spotsize at a 400-mm focal distance, 2- to 3-W power, and 0.5- to 1.0-second pulse durations. Cavernous lesions often present bleeding problems during removal that are not effectively controlled using the co laser, thereby requiring the useof other forms of therapy.

Reinke's Edema And Vocal Fold Polyps, Granuloma, & Malignant Neoplasms are the conditions which also can be treated by laser therapy.

Laser-Assisted Temporomandibular Joint Surgery-Advances in arthroscopic instrumentation and technique for small joint surgery have recently found application in surgery for the temporomandibular joint (TMJ). Coupled with the advent of high-resolution magnetic resonanceimaging (MRI) the accuracy of diagnosis of TMJ disorders has been greatly enhanced. Arthroscopy of the TMJ has consequently progressed from an instrument of diagnosis to one of treatment. As its usefulness for the treatment of internal derangements, particularly nonreducing disk displacement (closed

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lock), has become generally accepted, the search for improved instrumentation has resulted in the development of various laser systems for TMJ surgeryThe Ho:YAG laser4 configured for arthroscopic surgery consists of a free-beam laser with a sterile fiber-optic delivery system and the appropriately adapted arthroscope and video system. Because the Ho:YAG emission is highly absorbed by water with an average depth of absorption of 0.3 mm. It removes tissue precisely. Because the target tissueitself has a high water content and the laser operates within SSSSa fluid medium, there is very little unwanted thermal damage lateral to the vaporization crater. Nevertheless, even with minimal unwanted heat effects the actual thermal injury may vary from 0.1 to 1.0 mm depending on tissue type and the exposure parameters of the individual laser. Tarro" measured tissue necrosis with Ho:YAG and found it to be 0.4 to 0.6 mm, whereas electrocautery produced necrosis of 0.7 to 1.8 mm. In addition to the thermal effects the short pulse width of 350 ps associated with high fluence rates may also induce photomechanical and photoacoustic effects that also contribute to tissue ablation.Commercially available low output Ho:YAG lasers8 are quite adaptable for TMJ arthroscopic surgery. Several fiber delivery methods are available. The specific styles and specifications vary among manufacturers. It is rare to require an output power in excess of 10 W or a post-repetition rate (PRR) exceeding 10 Hz to resect fibrocartilage or recontour bone. Lower settings are suggested for making releasing incisions.

Biostimulation and Photodynamic Therapy:

Photodynamic therapy is an experimental cancer treatment that is based on a cytotoxic photochemical reaction. This reaction requires molecular oxygen, the photoactive drug dihematoporphyrin ether, a hematophorphyrin derivative and intense light, which is typically delivered by a laser. Dihematoporphyrin which is relatively retained in malignant tissue after several days, is given intravenously to a patient. Laser light at a wavelength corresponding to the absorption peak of the drug is used to activate the drug to an excited state. The drug then reacts with molecular oxygen to produce singlet oxygen, a highly reactive free radical which ultimately leads to tissue necrosis.

Laser Hazards and Laser Safety:

The subject of dental laser safety is broad in scope, including not only an awareness of the potential risks and hazards related to how lasers are used, but also a recognition of existing standards of care and a thorough understanding of safety control measures.

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Laser Hazard Class for according to ANSI and OSHA Standards:

Class I - Low powered lasers that are safe to view

Class IIa - Low powered visible lasers that are hazards only when viewed directly for longer than 1000 sec.

Class II - Low powered visible lasers that are hazardous when viewed for longer than 0.25 sec.

Class IIIa - Medium powered lasers or systems that are normally not hazardous if viewed for less than 0.25 sec without magnifying optics.

Class IIIb - Medium powered lasers (0.5w max) that can be hazardous if viewed directly.

Class IV - High powered lasers (>0.5W) that produce ocular, skin and fire hazards.

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The types of hazards can be grouped as follows: 1. Ocular injury 2. Tissue damage3. Respiratory hazards4. Fire and explosion5. Electrical shock

1. Ocular Injury:

Potential injury to the eye can occur either by direct emission from the laser or by reflection from a specular (mirror like) surface or high polished, convex curvatured instruments. Damage can manifested as injury to sclera, cornea, retina and aqueous humor and also as cataract formation. The use of carbonized and non-reflective instruments has been recommended.

2. Tissue Hazards:

Laser induced damage to skin and others non target tissues can result from the thermal interaction of radiant energy with tissue proteins. Temperature elevation of 21°C above normal body temp (37°C) can produce cell destruction by denaturation of cellular enzymes and structural proteins. Tissue damage can also occur due to cumulative effects of radiant exposure. Although there have been no reports of laser induced caroinogenesis to date, the potential for mutagenic changes, possibly by the direct alteration of cellular DNA through breathing of molecular bonds, has been questioned.

The terms photodisruption and photoplasmolysis have been applied to describe these type of tissue damage.

3. Respiratory:

Another class of hazards involves the potential inhalation of airborne biohazardous materials that may be released as a result of the surgical application of lasers. Toxic gases and chemical used in lasers are also responsible to some extent.

During ablation or incision of oral soft tissue, cellular products are vaporized due to the rapid heating of the liquid component in the tissue. In the

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process, extremely small fragments of carbonized, partially carbonized, and relatively intact tissue elements are violently projected into the area, creating airborne contaminants that are observed clinically as smoke or what is commonly called the ‘laser plume’. Standard surgical masks are able to filter out particles down to 5m in size. Particle from laser plume however may be as small as 0.3m in diameters. Therefore, evacuation of laser plume is always indicated.

4. Fire and Explosion

Flammable solids, liquids and gases used within the clinical setting can be easily ignited if exposed to the laser beam. The use of flame-resistant materials and other precautions therefore is recommended.

Flammable materials found in dental treatment areas.

Solids Liquids Gases

ClothingPaper productsPlastics

Waxes and resins

Ethanol

AcetoneMethylmethacrylateSolvents

OxygenNitrous oxideGeneral anestheticsAromatic vapors

5. Electrical Hazards:

These can be:

- Electrical shock hazards

- Electrical fire or explosion hazards

Summary of laser safely control measures recommended by ANSI

Engineering controls:- Protective housing- Interlocks- Beam enclosures- Shutters- Service panels- Equipment tables

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- Warning systems- Key switch

Administrative controls:- Laser safety officer- Standard operating procedures- Output limitations- Training and education- Medical surveillance

Personal protective equipment:- Eye wear- Clothing - Screens and curtains

Special controls:- Fire and explosion- Repair and maintenance

Conclusion:

Laser has become a ray of hope in dentistry. When used efficaciously and ethically, lasers are an exceptional modality of treatment for many clinical conditions that dentists treat on daily basis. But laser has never been the “magic wand” that many people have hoped for. It has got its own limitations. However, the futures of maxillofacial surgery with the laser is bright with some of the newest ongoing researches.

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REFERENCES-

1. Chrysikopoulos, Laser assisted oral & maxillofacial surgery for the patients on the anticoagulant therapy in daily practice, J Oral Laser applications 6(2006) no 2.2. Dent Clin North Am 2000 oct; 44(4): 851-73

3.Desiate A, Cantore S, Tullo D, Profeta G, Grassi Fr, Ballini A. 980 nm diode lasers in oral and facial practice: current state of the science and art, .Int J Med Sci 2009; 6:358-364.

4. Hendler BH. Ciatcno J. Mooar P. et al. Holmiuin:YAG laser arthroscopy of the temporomandibular joint. J Oral Maxillofac Surg 1992:50:931-934.

5. J.Canzona, Carbon-di-oxide laser in oral & maxillofacial surgery JOMS.vol 47, issue 8, pg 52-54.

6.J   Ishii  K   Fujita , T   Komori , Laser surgery as a treatment for oral leukoplakia. Oral oncology,Volume 39, Issue 8, Pages 759-769 (December 2003)7. Junnosuke Ishii, Kunio Fujita, Sachiko Munemoto, Takahide Komori. Journal of Clinical Laser Medicine & Surgery. February 2004, 22(1): 27-33

8. Koslin MG. Martin JC. The use of the holmium laser for temporomandibularjoint arthroscopic surgery. J Oral Maxillofac Surg 1993:51:122-123

9. Laser artifacts & diagnostic biopsy . Oral Surg Oral med Oral path Oral radiol & Endond vol 83,issue6,pg 639-640.

10. Lewis clayman, Paul Kuo, Text book on Lasers in maxillofacial surgery & dentistry.

11. Oral & Maxillofacial surgery clinics vol.16, issue 2, May 2004, pg no 143-308

12. Roodenburg JL. Panders AK. Vermey A. Carbon dioxide laser surgery of oral leukoplakia. Oral Surg Oral Med Oral Pathol 1991:71:670-674.

13. Shinichi Takeuchi, Effect of the carbon-di-oxide laser vapourisation on oral precancerous lesions-promptional effects for malignant transformation. Asian J Oral Maxillofac Surg 2005;17:217-222

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