LASERS IN ORTHODONTICS

LASERS IN ORTHODONTICSJERUN JOSE

CONTENTS INTRODUCTIONDISCOVERY OF LASERSLASER PHYSICSCOMPONENTS OF LASERPROPERTIES OF LASERCLASSIFICATION OF LASERSLASER TISSUE INTERACTION AND BIOLOGICAL EFFECTSLASERS USED IN DENTISTRYUSES OF LASERS IN ORTHODONTICSREFERENCE

INTRODUCTION

Light has been used as a therapeutic agent for many centuries. Natural light was used for medical treatment in ancient Egypt and Greece. Later Roman and Arab physicians introduced light therapy into general medical use

Light is a form of electromagnetic energy that exists as a particle, and travels in waves, at a constant velocity The basic unit of this radiant energy is called a photon

The wave of photons travels at the speed of light can be defined by two basic properties First is amplitude, which is defined the vertical height of the wave oscillation from the zero axis to its peak. The second property of a wave is wavelength, which is the horizontal distance between any two corresponding points on the wave.

This correlates to the amount of energy in the wave: the larger the amplitude, the greater the amount of energy that can do useful work A joule is a unit of energy

As waves travel, they oscillate several times per second, termed frequency. Frequency is inversely proportional to wavelength: the shorter the wavelength, the higher the frequency and vice versa.

The newer treatment procedures are conservative, painless and are more reliable and they contribute towards better esthetics. The development of LASER (light amplification by the stimulated emission of radiation) in dentistry has allowed the dental professionals to provide comfort and better treatment for the patient

A laser is a device that emits light (electromagnetic radiation) through a process of optical amplification based on the stimulated emission of photons

Discovery of laserIn 1704, Newton characterised light as a stream of particlesThe Youngs interference experiment in 1803 and the discovery of the polarity of light convinced other scientists of that time that light was emitted in the form of waves

The concept of electromagnetic radiation, of which light is an example, had been described in mathematical form by Maxwell, in 1880Maxwells electromagnetic (EM) theory explained light as rapid vibrations of electromagnetic fields due to the oscillation of charged particles

The electromagnetic spectrum is a comparative arrangement of electromagnetic energy (photonic quanta) relative to wavelength, spanning ultra-short gamma and X-radiation, through visible light, to ultra-long micro- and radio-waves

Maxwells electromagnetic theory, the energy intensity of electromagnetic emissions with a given frequency is proportional to the square of this frequency At the turn of the 20th century, the black body radiation phenomenon challenged the waveform light theory

According to Planck,radiation such as light, is emitted, transmitted and absorbed in discrete energy packets or quanta, determined by the frequency of the radiation and the value of Plancks constant

In explaining the photoelectric effect, Einstein assumed that a photon could penetrate matter, where it would collide with an atom. Since all atoms have electrons, an electron would be ejected from the atom by the energy of the photon, with great velocity.

Einstein explained about laser light in 1917 in his Zur Theorie der Strahlung(Theory of Wavelength), that when there exists the population inversion between the upper and lower energy levels among the atom systems, it was possible to realise amplified stimulated radiation.

Stimulated electromagnetic radiation emission has the same frequency (wavelength) and phase (coherence) as the incident radiation

MASERIn 1953, Charles Townes, experimenting with microwaves, produced a device whereby this radiation could be amplified by passing it through ammonia gasThis was the first MASER (microwave amplification by the stimulated emission of radiation) and was developed as an aid to communication systems and time-keeping (the atomic clock)

LASERTheodore Maiman in 1960 invented the first laser at the Hughes Air Craft Company,USA using a lasing medium of ruby that was stimulated using high energy flashes of intense light.

In 1964, Ralph Stern and Reidar Sognnaes used the ruby laser to vaporise enamel and dentine. In 1969 Leon Goldman used the laser clinically on enamel and dentine.

Laser physics

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 itThe radiation emitted by lasers including both visible and invisible Iight 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 processes1. Absorption2. Spontaneous emission3. Stimulated emission

Einstein considered the model of a basic atom to describe the production of laserAn atom consists of centrally placed nucleus which contains positively 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 then 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'

Components of laserActive mediumPumping mechanismOptical resonatorDelivery systemCooling systemControl panel

Active medium. This material may be a solid, liquid or gas.Lasing medium determines the wavelength of the light emitted from the laser and the laser is named after the medium.

The first dental laser used a crystal of neodymium-doped yttrium aluminium garnet (Nd:YAG) as its active medium.

The active medium is positioned within the laser cavity, an Internally-polished tube, with mirrors co-axially positioned at each end and surrounded by the external energising input, or pumping mechanism

2. Pumping mechanismThis represents a man-made source of primary energy that excites the active medium. This is usually a light source, either a flashlight or arc-light, but can be a diode laser unit or a electromagnetic coil

Energy from this primary source is absorbed by the active medium, resulting in the production of laser light. This process is very inefficient, with only some 3-10% of incident energy resulting in laser light, the rest being converted to heat energy.

3. Optical resonator Laser light produced by the stimulated active medium is bounced back and forth through the axis of the laser cavity, using two mirrors placed at either end, thus amplifying the power. The distal mirror is totally reflective and the proximal mirror Is partly transmissive, so that at a given energy density, laser light will escape to be transmitted to the target tissue

4.Delivery systemLaser energy should be delivered to the surgical site by various means that should be ergonomic and preciseDependant upon the emitted wavelength, the delivery system may be a quartz fibre-optic, a flexible hollow waveguide, an articulated arm (incorporating mirrors), or a hand-piece containing the laser unit (at present only for low-powered lasers).

Shorter wavelength instruments, such as KTP, diode, and Nd:YAG lasers, have small, flexible fiberoptic systems with bare glass fibers that deliver the laser energy to the target tissue. Erbium and CO2 devices are constructed with more rigid glass fibers, semiflexible hollow waveguides, or articulated arms

All the invisible dental lasers are equipped with a separate aiming beam, which can either be laser or conventional light. The aiming beam is delivered coaxially along the fiber or waveguide and shows the operator the exact spot where the laser energy will be focused.

Dental lasers can be used either in contact mode or non contact modeIn 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 modeFiber 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.

There are two basic modes of wavelength emission for dental lasers, based on the excitation source.Continuous modePulsating mode

1.Continuous modeContinuous wave emission means that laser energy is emitted continuously as long as the laser is activatedand produces constant tissue interaction.CO2 and diode lasers operate in this manner

These lasers are sometimes equipped with a mechanical shutter with a time circuit or a digital mechanism to produce gated or superpulsed energy. Pulse durations can range from tenths of a second to several hundred microseconds.

2.pulsating modeFreerunning pulse emission occurs with very short bursts of laser energy due to a flashlamp pumping mechanism. The usual pulse durations are in the low hundreds of microseconds, and there is a relatively long interval between pulses. Nd:YAG, Er:YAG, and Er,Cr:YSGG devices operate as freerunning pulsed lasers.

5. Cooling systemHeat production is a by product of laser light propagation.

It increases with the power output of the laser and hence, with heavy-duty tissue cutting lasers, the cooling system represents the bulkiest component. Co-axial coolant systems may be air- or water-assisted.

Erbium lasers employ a water spray for cooling hard tissues

6.control panelThis allows variation in power output with time, above that defined by the pumping mechanism frequency. Other facilities may allow wavelength change (multi-laser instruments)

PROPERTIES OF LASER LIGHTThere are several important properties of laser light that distinguish it from the normal light

MonochromatismLasers emit light that is monochromatic or specifically have a single wave length from UV to infrared. i.e. lasers express one color.

Lasers of varying types emit an individual wave length or specified wavelengths This property is important for the high spectra power density of the laser beam

Collimation or (Directionality)The laser beam, as it exits from the laser device, has very little divergence. They do not diverge and travel parallel to each other. The beam which is emitted has constant size and shape.

Most of the gas or solid-state laser emit laser beam with a divergence angle of approximately a milli radian. This explains why laser light is extraordinarily hazardous.

By not diverging over distance, laser light maintains brightness, so that it is still concentrated enough to be dangerous. But this property is important for good transmission through delivery system

CoherencyThe laser light waves produced are physically identical. i.e. they have identical amplitude and frequency. There are two types of coherence of laser light, longitudinal and transverse.

The longitudinal type of coherence represents time coherence along the longitudinal beam, whereas transverse coherence or spectral coherence refers to coherence across the beam.

Coherence causes the collimation of a laser beam over extremely large distances and allows the beam to accept extremely fine focusing Any given laser beam can be focused only to a diameter equal to the wavelength of the specific laser

BrightnessThis property arises from the parallelism or collimation of the laser light as it moves through space maintaining its concentration. The high brightness factor translates to high concentrations of energy when the laser is focused on a small spot

The focusing of the brightness of the laser beam is what the clinicians depends on to elevate the temperature of tissues or to cut or to vaporize the tissues

Difference between ordinary light and laser light

Classification of Lasers1.BASED ON ACTIVE MEDIUM :Solid state- Nd: YAG Liquid state-diode laser Gas state- CO2

2.DEPENDING ON WAVE LENGTHHard lasers- comes in infrared Spectrum (> 700 nm) Eg: CO2; Nd: YAG; Argon laserSoft Lasers - Comes in UV (140-400nm) & visible light (400-700) spectrum Eg: HeNe, diode laser

3.BASED ON SAFETY PROCEDUREClass 1: safe under all conditions (fully enclosed system) - Eg: Nd: YAG laser. Laser used in dental laboratory.Class 2: Output is 1 mw- visible low power laser- Visible red aiming beam of a surgical laser.Class 3A: Visible laser above 1 milli watt- No dental examples

Class 3B: Upper continuous power output limit is 0.5 w- Low power diode laser used for biostimulation. Direct viewing is hazardous to the eye.

Class 4: Output excess of class 3B & are used for cutting & drilling- All lasers used for oral surgery, whitening and cavity preparation. Direct or indirect viewing is hazardous to the eyes

LASER- TISSUE INTERACTION AND BIOLOGICAL EFFECTS

Once a laser beam is produced it is aimed at tissue to perform a specific task. As the energy reaches the biological interface, one of four interactions will occurAbsorptionReflection TransmissionScattering

Absorption Specific molecules in the tissue known as chromophores absorb laser light energy The light energy is then converted into other forms of energy to perform work.Main chromophores seen in oral tissues are hemoglobin, melanin,pigmented proteins,hydroxyapatite,and water

Absorption is the most important interaction. Each wavelength has specific chromophores that absorb their energy.

Near infrared lasers like diodes and Nd:YAGs are mostly absorbed by pigments such as hemoglobin and melanin. Erbium and CO2 lasers are predominantly absorbed by waterwith erbium wavelengths also exhibiting some hydroxyapatite absorption.

The shorter, near infrared wavelengths of diodes and Nd:YAG lasers penetrate tissue more deeply than the longer, mid infrared wavelengths of the Erbium and CO2 lasers

Thermal relaxationThermal relaxation is the term applied to the ability to control a progressively increasing heat loading of target tissue.Thermal relaxation rates are proportional to the area of tissue exposed and inversely proportional to the absorption coefficient of the tissue

Factors that influence absorption and thermal relaxation are1.Exposure time and Laser emission modeThermal relaxation will occur least with continuous wave emission and maximally in free-running pulsed delivery2. Laser incident power (Joules per second)

3.Laser power density (Watts per square centimetre): for any chosen level of incident power, the smaller the beam diameter, the greater concentration of heat effects4. Beam movement: relative to tissue site; rapid laser beam movement will reduce heat build-up and aid thermal relaxation

4. Endogenous coolant: blood flow.5.Exogenous coolant: water, air, pre-cooling of tissue6.Incident angle of laser beamMaximum control of laser tissue interaction can be achieved if the incident laser beam is perpendicular to the tissue surface

Reducing the incident angle towards the refractive angle of the tissue surface will increase the potential for true light reflection with an associated reduction in tissue change

Reflection Density of the medium , or angle of incidence being less than the refractive angle , results in total reflection of the beam.In true reflection ,the incident and emergence angles will be the same .If the medium interface is rough or non homologous , some scatter may occur

Transmission In transmision beam enters the medium , but there is no interaction between the incident beam and the tissue.The beam will emerge distally , unchanged or partially refracted.

Scattering Once the laser energy enters the target tissue it will scatter in various directions. This phenomenon is usually not helpful, but can help with certain wavelengths biostimulative properties.

There are five important types of biological effects that can occur once the laser photons enter the tissue: They are fluorescence photothermalphotodisruptive photochemical photobiomodulation

Fluorescence The amount of fluorescence is related to the size of the lesion, and this information is useful in diagnosing and managing early carious lesions.

Photothermal effects occur when the chromophores absorb the laser energy and heat is generated. This heat is used to perform work such as incising tissue or coagulating blood.

Photothermal interactions predominate when most soft tissue procedures are performed with dental lasers. Heat is generated during these procedures and great care must be taken to avoid thermal damage to the tissue

Photodisruptive or photoacousticHard tissues are removed through a process known as photodisruptive ablation. Short-pulsed bursts of laser light with extremely high power interact with water in the tissue and from the handpiece causing rapid thermal expansion of the water molecules

This causes a thermo-mechanical acoustic shock wave that is capable of disrupting enamel and bony matrices quite efficiently. The pulsed Erbium laser ablation mechanism of biological tissues is still not completely understood but erbium lasers high ablation efficiency seems to result from these micro-explosions of overheated tissue water in which their laser energy is predominantly absorbed.

Thus tooth and bone are not vaporized but pulverized instead through the photomechanical ablation process. This shock wave creates the distinct popping sound heard during erbium laser use.

Photochemical reactions occur when photon energy causes a chemical reaction. These reactions are implicated in some of the beneficial effects found in biostimulation

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Photobiomodulation or Biostimulation refers to lasers ability to speed healing, increase circulation, reduce edema, and minimize pain. Many studies have exhibited effects such as increased collagen synthesis, fibroblast proliferation, increased osteogenesis, enhanced leukocyte phagocytosis

The exact mechanism of these effects is not clear, but it is theorized they occur mostly through photochemical and photobiological interactions within the cellular matrix and mitochondria. Biostimulation is used dentally to reduce postoperative discomfort and to treat recurrent herpes and aphthous stomatitis

When a laser heats oral tissues, certain reversible or irreversible changes can occurHyperthermia below 50 degrees C Coagulation and Protein Denaturation 60+ degrees C Vaporization 100+degrees C Carbonization - 200+ degrees C

Irreversible effects such as denaturation and carbonization result in thermal damage that causes inflammation, pain, and edema.

Immediate post operative view of an excisional procedure using a diode laser.

Immediate post operative views of excisional procedures using Erbium and Carbon Dioxide lasers.

LASERS IN ORTHODONTICS- PART 2 Jerun jose2nd year pgDepartment of orthodontics

CONTENTSLASER EFFECTS ON DENTAL HARD AND SOFT TISSUESLASERS USED IN DENTISTRYUSES OF LASERS IN ORTHODONTICSLASER SAFETY IN DENTAL PRACTICECONCLUSIONREFERENCE

Laser Effects on Dental Hard TissuesThermal EffectHere thermal vaporization of tissue by absorbing infrared laser light occurThe laser energy is converted into thermal energy or heat which destroys the tissues.

The laser beam couples to the tissue surface, and this absorption leads to a heating with denaturation at about 45C to 60C. Above 60C coagulation and necrosis can be observed accompanied by a desiccation of the tissue. At 100C the water inside the tissue vaporizes

Carbonization and later pyrolysis with vaporization of the bulky tissue terminate the thermal laser tissue interaction. The laser light will be absorbed and converted to thermal energy by stimulating the lattice vibrations of the tissue molecules.

This leads to a heating of the surrounding tissues to a boiling of water followed by carbonization and tissue removalDamage to the adjacent tissue is manifested by massive zones of carbonization, necrosis and cracks.

Mechanical EffectHigh 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 waves can lead to very high pressures so that adjacent tissue will be destroyed or damaged. To avoid micro cracks in dental tissues, the maximum laser energy density of all laser systems must be kept below a certain threshold.

Chemical EffectThe basis of the photochemical effect is the absorption of laser light without any thermal effect which leads to an alteration in the chemical and physical properties of the irradiated tissues

Normal enamelLased enamel

Thermomechanical EffectDue to the good absorption of laser in water as well as in hydroxyapatite, the laser radiation leads to fast heating of water inside. In the mineralized matrix there is an explosive volume expansion

In dentin, no cracks are seen, but more thermal damage like carbonization and necrosis are found. In enamel, cracks are always found

Morphological analysis of Er:YAG laser treated enamelEnamel. 100 mj. 10 Hz. With water cooling. Honey-comb appearance can be seen but not throughout the surface due to non-homogenous application of the laserEnamel. 100 mj. 10 Hz. With water cooling. Honey-comb appearance can be seen on the surface similar to acid etching.

Enamel. 100 mj. 10 Hz. With water cooling. Higher magnification of the surface No signs of thermal damage. Honey-comb appearance.Enamel. 250 mj. 10 Hz. With water cooling.Serrated surface with honey-comb appearance.

Enamel. 500 mj. 10 Hz. With water cooling. Interprismatic matrix has been removed.some melting points due to repeated shots at the same point seenEnamel. 600 mj. 10 Hz. Without water cooling. Layered enamel surface due to dehydration of enamel during laser application

Enamel. 750 mj. 10 Hz. Without water cooling. Enamel. 800 mj. 5 Hz Without water cooling. Melted and resolidified enamel. This texture is highly acid resistant.

Enamel. 1000 mj. 10 Hz. Without water cooling. Rose-bud like appearance. over destruction of enamel with high energy intensity. Enamel lost its integrity in layers around the lased point.Enamel. 1000 mj. 10 Hz. Without water cooling. Overdestructed and layered surface as a result of excessively heated enamel.

Effects on dentin Dentin. 250 mj. 10 Hz. Without water cooling. Swollen dentin orificesDentin. 250 mj. 10 Hz. With water cooling. Partially open dentinal tubules with crater formations

Dentin. 500 mj. 10 Hz. Without water cooling. Pop-corn like appearance.Thermal destruction of dentinDentin. 500 mj. 5 Hz. With water cooling. Dehydartion resulted in cracking

Ablation Threshold of Er:YAG and Er:YSGG Laser Radiation in Enamel and dentin

Laser Effect on Dental PulpVital dental pulp is acutely sensitive to thermal changeThe pulp tissue response to lasers is evaluated in three formsHistologic analysisRadiographic analysisLaser Doppler flow meter measurement

Use of a continuous wave apparatus has been shown to generate significant thermal tissue damage in the oral cavity Pulpal tissue cannot survive in an environment of elevated temperatures for long periods when tooth structure is irradiated with lasers

Rise of 6C results in irreversible pulpitisRise of 11C results in necrosis of pulp

Pulsing which has been used during soft tissue laser ablation has an effective mechanism for reducing the extent of collateral tissue damageThe use of a combination of air and water spray before, during or immediately after laser irradiation to enamel and dentin may be a more effective method for temperature control and reduction of heat transfer to the pulp

Air-water cooling is used with laser systems such as CO2, holmium and erbium.This can provide adequate heat protection to the pulp equivalent to that of the common dental drill

Uncontrolled laser irradiation of oral structures can cause pulpal inflammation with any type of laserThe undesirable side effects of laser vary primarily with power and energy density and secondarily with the type of laser used

If pulp temperature is raised beyond 5C level, the odontoblastic layer may not be present.Odontoblastic alignment may be disrupted, displaying vertical and layering type of structure. The threshold response for pulp reaction appears to lie at energy density less than 60 J/cm

LASERS USED IN DENTISTRY

The dental lasers in common use today are Erbium, Neodynium, Diode, and CO2. Each type of laser has specific biological effects and procedures associated with them.

Erbium Lasers

Erbium lasers are built with two different crystals, the Er:YAG (Erbium yttrium aluminum garnet crystal) and Er,Cr:YSGG (Erbium chromium sensitized yttrium scandium gallium garnet crystal).

They do have different wavelengths, Er:YAG has 2940 nm and Er,Cr:YSGG has 2780 nm. There is a significant water absorption difference between these two wavelengths. Er:YAG wavelength is at the peak of water absorption in the infrared spectrum whereas the Er,Cr:YSGG exhibits less absorption

The Er,Cr:YSGG has also been shown to have significantly deeper thermal penetration in tooth structure

The erbium lasers are hard and soft tissue capable Their primary chromophore is water, but hydroxyapatite absorption occurs to a lesser degree

Photothermal interactions predominate in soft tissue procedures and photodisruptive in hard tissue procedures. Thermal relaxation is excellent and very little collateral thermal damage occurs in tissues

Bone cutting with erbium lasers results in minimal thermal and mechanical trauma to adjacent tissues. Atraumatic effect and excellent healing response Very short laser pulses of 50 to 100 microseconds are typically used for hard tissue procedures.

SOFT TISSUE LASER The main parameters that differ from hard tissue uses are much longer pulse durations (300-1000 microseconds) and less or no water spray.There will be thermal relaxation and minimal heat penetration into underlying tissues

Nd:YAG LasersNd:YAG lasers were the first types of true pulsed lasers to be marketed exclusively for dental use in 1990. They are a near infrared wavelength of 1064 nm. This wavelength is absorbed by pigment in the tissue, primarily hemoglobin and melanin

Photothermal interaction predominates and the laser energy here can penetrate deeply into tissues. Contact and noncontact mode are both utilized depending on the procedure being performed.

Nd:YAG also have excellent biostimulative properties. Nd:YAG lasers have the unique capacity to stimulate fibrin formation. This effect is maximized when the pulse duration is set at 650 microseconds

These lasers are primarily used for periodontal treatments. Their proclivity for pigmented tissue allows for effective debridement and disinfection of periodontal pockets.

Bacterial decontamination in tissues treated with Nd:YAG laser energy also contributes to resolution of periodontal infectionNd:YAG lasers can also be used for multiple soft tissue procedures such as gingivectomy, frenectomy, impression troughing and biopsy

Diode LasersDiode lasers are becoming quite popular due to their compact size and relatively affordable pricing. A specialized semiconductor that produces monochromatic light when stimulated electrically is common to all diode lasers

A simple laser pointer is an example of a diode laser. Diode lasers can be used in both contact and non-contact mode and can function with continuous wave or gated pulse modes

They are not capable of free running pulsed mode.Diode lasers are invisible near infrared wavelengths and current machines range from 805 1064 nm. One exception is the Diagnodent caries diagnostic laser which uses a visible red wavelength of 655 nm

Diode lasers are used for soft tissue only. The chromophores are pigments such as hemoglobin and melanin. Photothermal interactions predominate

They are quite effective for gingivectomy, biopsy,, and frenectomy, photobiomodulation

CO2 LasersThe CO2 laser is a gas-active medium laser Incorporates a sealed tube containing a gaseous mixture with CO2 molecules pumped via electrical discharge current.

The light energy, whose wavelength is 10,600 nm, is placed at the end of the mid-infrared invisible nonionizing portion of the spectrum, and it is delivered through a hollow tube-like waveguide in continuous or gated pulsed mode

This wavelength is well absorbed by water, second only to the erbium family. It can easily cut and coagulate soft tissue, and it has a shallow depth of penetration into tissue, which is important when treating mucosal lesions,.

In addition, it is useful in vapourizing dense fibrous tissue. There is rapid tissue interaction

The CO2 laser cannot be delivered in a conventional optic fiber.The laser energy is conducted through the waveguide and is focused onto the surgical site in a noncontact fashion

The loss of tactile sensation could pose a disadvantage for the surgeon, but the tissue ablation can be precise with careful technique. Large lesions can be treated using a simple back and forth motion

The noncontact mode thus has an advantage when treating movable oral structures, such as the tongue and floor of the mouth.This wavelength has the highest absorption in hydroxyapatite of any dental laser, about 1000 times greater than erbium

Therefore, tooth structure adjacent to a soft-tissue surgical site must be shielded from the incident laser beamusually a metal instrument placed in the sulcus provides the protection

A portable hand-held CO2 laser system

The continuous wave emission and delivery system technology of CO2 devices limit hard-tissue applications because carbonization and crazing of tooth structure can occur due to the long pulse duration and low peak powers

Uses of Lasers in orthodontics1.Laser etching 2.Bonding3.Debonding of ceramic brackets4.Bracket mesh designing5.Efficacy of low level laser therapy in reducing orthodontic post adjustment pain

6.Lasers in holography7.Laser spectroscopy8.3D laser scanning9.Laser microwelding10.Effect of laser for demineralisation resistence

11.Soft tissue lasers12.Mangement of impacted teeth13.Laser orthopedics14.Effect of low level laser in accelerated tooth movement

Laser Etching in Orthodontics

Argon laser Krypton flouride excimer laser

PrincipleSplits the bond of organic and inorganic substances on the surface.Explosive vapourization of water modifies the smooth surface of enamel

Due to the extremely short pulse length of some nanoseconds and sudden removal,there is no efficient heat conductance through the hard substance so no harmful increase in the temperature of the pulp.

Etched enamel by Er;YAG laserEtched by Malic acid

BondingArgon laser is commonly used as light curing adhesives.The procedure for light curing is almost same as conventional light curing

The enamel surface was etched with 37% phosphoric acid for 15 secondsThe surface was treated with MegabondAdhesive precoated brackets were placed on enamel surfaceMark Kurchak,Bernadette Desantos,John Powers,David Turner JCO 1997

Laser tip was held 0.5mm from the bracket and the light curing wand was kept touching the bracket.No enamel damage caused by argon lasers at energy levels of 1.6 to 6 watts

ResultThe study demonstrates that 10 seconds of curing with argon laser produces bond strength comparable to those achieved with 20 to 40 seconds of curing with a conventional high intensity light.The time savings involved in bonding a full arch is significant with the help of Laser.

Laser Debonding of Ceramic Orthodontic bracketsLaser light has been shown to degrade resins by thermal softening or photo ablation.Both polycrystalline alumina and single crystal alumina (saphire) ceramic orthodontic brackets were bonded to the labial surface of lower deciduous teeth with regular acid etch technique.

Robert M Tocchio,Peter T Williams,Franz J Mayer,Kenneth G Standing) AJO 1993

The brackets were debonded by irradiating the labial surfaces of the brackets with laser light at wavelengths of,1060nm. Debonding times were measured and the surfaces created by debonding were examined with both light and scanning electron microscopy to determine the extent of bracket and enamel damage

ResultsNo enamel, bracket damage in any sample.The debonding of polycrystalline brackets is caused by thermal softening of the bonding resin resulting from heating of the bracket. The hot bracket then slides off the tooth

Ideal debonding time 0.5 seconds shows no pulp reaction, No enamel tear outs and catastrophic bracket failures were observed.Lasers used are Nd:YAG laser and carbon dioxide laser.

Newer Bracket SystemsNewer brackets with laser reinforced structured bases enable the force to be applied even closer to the crown.The base of brackets guarantees an excellent bond during the entire treatment period

Laser markings help in easy identification of brackets.Compared with conventional markings,laser markings cannot be abraded and does not contain harmful colouring agents

Accelerated Tooth movementMethod of increasing tooth movement are ,Injection of ProstaglandinsActive form of vitamin D3OsteocalcinRelaxin Side effects are local pain and discomfort

Electric stimulation ,corticotomy and resonance vibrationRequires complex apparatus

Low level laser therapy(LLLT)Fujita et al. (2008) and Yamaguchi et al. (2007) reported that LLLT stimulated the velocity of tooth movement via RANK and c-Fms gene expressions in vitroThis was confirmed by Yamaguchi et al. (2010) which showed that LLLT accelerates the process of bone remodeling by stimulating MMP-9, cathepsin K, and integrin subunits.

Study conducted by Gauri Doshi-Mehta and Wasundhara in 2012 at Nagpur showed 56%increase in rate of tooth movement in first 3 months and later 30%

Gauri Doshi,Wasundhara,AJODO 2012

Reducing orthodontic post adjustment pain

Methods TENSLow level laser therapyVibratory stimulation

Low level laser therapyLLLT has been shown to produce analgesic effects Here the energy output is low enough so as not to cause a rise in the temperature of the treated tissue above 36.5 degrees centigrade

Biostimulatory effects of LLLT have been attributed to its anti inflammatory and neuronal effects.Harris proposed that LLLT has benign stimulatory influence on depressed neurons and lymphocytes

Stabilization of membrane potential and release of neuro transmitters.Laser unit used was Galium diode laser

Laser HolographyHans Rydin and Bielkhagen(1982) developed a new method for comparing the tooth positions on the dental casts at different stages.Holograms of the casts were prepared using Helium Neon laser

Burstone C.J.,T.W.Every and R.J.Pryputneiwiz (1982)based on pulsed laser hologram inferometry studied the dynamics of incisor extrusion

ProcedureThe output from the laser is split into two parts by beam splitter.One part was expanded by a beam expander and is used to illuminate the object.The scattered wave from the object is called object wave.

The second part was expanded by a beam expander,reflected by a mirror and a wave called reference wave is formed which forms the hologram

Laser spectroscopyUsed in the field of dentistry for the purpose of analyzing the surface structures of dental materialsUsed for evaluating the surface roughness of orthodontic wires, brackets, comparison of materials, surface changes of orthodontic materials

3D LASER SCANNINGObtains 3D surfaces by gathering measurements made by smoothly sweeping a handheld laser scanning wand over an object Similar to spray painting

The object's image instantly appears on computer screen Finished scan is processed to combine any overlapping sweeps Significantly reducing the time to develop surface models

The scanner works by casting a fan of laser light over the object, while the camera on the wand views the laser to record a cross-sectional profile of the object. The software is used to determine the position and orientation of the wand enabling the computer to reconstruct the full three-dimensional surface of the object.

LASER MICRO WELDINGLaser welding produces deep penetrationwelds with minimum heat effective zones.Laser welding has the advantage of welding dissimilar metals while producing very low heat

The process is a non-contact one that directs laser outputs of 2-10 kW into a very small areaThe laser beam makes a 'keyhole and the liquid steel solidifies behind the traversing beam, leaving a very narrow weld and heat affected zone

The weld is approximately 1 mm wide and the surrounding material is not distortedBecause the weld bead is small, there is usually no need for finishing or re-working and this reduces costs.

ORTHOPHASEROrthophaser Unit is bigger than the conventional spot welder It provides highly superior result

Almost all metals including the most recent and popular titanium can be welded. The unit consists of working microscope with integrated eye protections, flexible hand piece with a locking mechanism for the hand piece and a compact control with preprogrammed parametersThe gas used in this is Argon

EFFECT OF LASERS FOR DEMINERLIZATION RESISTANCEExposure of enamel to laser irradiation imparts some degree of protection against demineralization under acid attackUsing quantitative microradiography, argon laser irradiation of enamel reduces the amount of demineralization by 30- 50%.

Fox et al found that, in addition to decreasing enamel demineralization and loss of tooth structure, laser treatment can reduce the threshold pH at which dissolution occurs by about a factor of five.

In sound enamel, calcium, phosphorus and fluoride ions diffuse into the acid solutions and are released into the oral environmentWith lased enamel, the microspaces created by laser irradiation,trap the released ions and act as sites for mineral reprecipitation within the enamel structure.

Lloyd Noel, Joe Rebellato, Rose D. SheatsAngle Orthod 2003;73:24925810 sec lased enamel5 sec lased enamelControl group

Thus, lased enamel has an increased affinity for calcium, phosphate and fluoride ionsThis will prevent demineralization

SOFT TISSUE LASERSSoft tissue laser is an effective tool to help manage treatment and enhance our aesthetic outcomesThe soft-tissue laser can significantly reduce treatment time by creating access for brackets/bands, improving bracket placement by improving tooth proportionality, and helping manage oral hygiene through removal of pseudopockets

Gingival aesthetics can be enhanced through shaping and contouring the gingival tissue during treatment

MANAGEMENT OF IMPACTED TEETHCommonly, cuspids are the last teeth bonded due to slow eruption, delayed passive eruption, or impaction. This will take long treatment time. It is a functional issue if the cuspids cannot be bracketed ideally

Archwire bends are required if the bracket cannot be placed ideally, resulting in increased chair time and difficulty in finishing treatment.The posterior occlusion is often hindered by delayed passive eruption of the second premolars

The diode laser can be used to assist the clinician in avoiding these situations by going directly to attachment, bracket, or band placement

LASER-ORTHOPEDICS Lasers can be applied to manipulation facial growthStudy by Mostafa Abathi and Maryam in rabbits showed irradiation TMJ by LLL during mandibular advancement increases bone formation in condylar region Abathi etal.Head and face medicine 2012

They irradiated TMJ by 630 nm KIO3 laser for 3 weeksFound that increase in bone formation in condylar region, while no increase in cartilage thickness and fibrous tissue

Laser Safety in Dental Practice

Tissue hazardsLaser induced damage to the skin and other non target tissue can result from thermal interaction of radiant energy with tissue proteinsTemperature elevations of 21 degrees centigrade above the normal body temperature can produce cell destruction by denaturation of cellular enzymes and structural proteins

Histologically thermal coagulation necrosis is produced.

Char layer is formed char layer is a strong absorbent of different wavelengths of laser light and the extent of collateral damage increases with this layer.Mechanical removal of char layer is essential

Environmental hazardsPotential inhalation of airborne hazardous materials that may be released as a result of laser therapy.Some lasers contain inert gases (argon, krypton or xenon) mixed with toxic gases such as fluorine or hydrogen chloride as the active medium

Inhalation of toxic material in the form of aerosols has been found potentially damaging to the respiratory system.Standard surgical masks and surgical smoke evacuation equipment is used in the theatre

Greatest producers of smoke carbon dioxide and Nd:YAG laser

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

Electrical hazardsElectrical hazards of lasers can be grouped as electrical shock hazards,electric fire hazards or explosion hazards.Insulated circuitry,shielding,grounding and housing of high voltage electrical components provide protection under most circumstances from electrical injury

Personal Protective Equipment

Eye protectionlasers can cause occular damage by either direct viewing or reflection of the beam.Adequate eye protection must be worn by the operator as well as the patient.

They are available in the form of safety goggles or screening devices.Laser protective eyewear filters are specified according to their optical density which takes into account the wavelength,power and diameter of the beam

Laser filtration masks Prevents air borne contamination

Foot pedal control switch with protective hood Prevents accidental depression by surgical staff.

conclusionWith technology and science reaching new heights it is needless to say that lasers would soon become a necessity in every field of science .Orthodontics has also been captured into this magical spell of laser which would enable us to reach new goals

REFERENCES

Lasers in DentistryFrom Fundamentals toClinical Procedures By:Dr. Donald J. Coluzzi Basic Laser Principles , MELLESGRIOT The Use of Lasers in Dentistry A Clinical Reference Guide for the Diode 810 nm & Er:Yag Introduction history of lasers,laser production,s.parker ,practice 1

5. Introduction history of lasers,laser production,s.parker ,practice 2 6.Versatality of an 810 nm Diode laser in dentistry; An over view.Samo piranat,Journal of laser and health academy.vol.20077. Lloyd Noel, DMD, MSa; Joe Rebellato, DDSb; Rose D. Sheats, DMD, MPHcAngle Orthod 2003;73:249258

8. Hu Longa; Ujjwal Pyakurela; Yan Wangb; Lina Liaoa; Yang Zhoua; Wenli LaicAngle Orthodontist, Vol 83, No 1, 20139.Elaut j,Weharbein Eur journal of orthodontics 26(2004)10. C. Apel, J. Meister1,, R.S. Ioana Lasers Med Sci 2002, 17:246252

11. David M. Sarver and Mark YanoskyAm J Orthod Dentofacial Orthop 2005;127:262-412. Jasmina Primoz; Giuseppe Perinettib,Angle Orthodontist, Vol 82, No 4, 201213. Y. Mahesh Kumara; N.S. RavindranbAngle Orthodontist, Vol 79, No 2, 2009