LASER AND ORTHODONTICS: THE MEETING POINT

BY: DR AGHIMIEN AO. Orthodontic unit, Dept. of preventive dentistry.

University Of Benin Dental SchoolNigeria

OUTLINEIntroduction/DefinitionHistorical Perspective Of LaserPhysics Of LaserBasic Component Of A Laser Machine Characteristics Of LaserClassification Of LaserTissue Interaction Of LaserSafety Precaution During Laser IrradiationApplication Of Laser In Orthodontics Direct Orthodontic Clinical Application Adjunctive Orthodontic Clinical Application Laboratory Orthodontic Laser ApplicationConclusionReferences

INTRODUCTION/DEFINITION

LASER is an acronym for “ light amplification by stimulated emission of radiation".

Its use has enabled orthodontist to address the challenges associated

with some of the conventional methods of orthodontic treatment.

These include direct chair side clinical orthodontic procedures,

adjunctive orthodontic and laboratory procedures.

HISTORICAL PERSPECTIVE OF LASER

• The theoretical basis of LASER was based on the theory of wavelength (Zur Theorie der Strahlung) postulated by Albert Einstein in 1917.

Schawlow and Town discovered LASER however, it was not until 1960 that Maiman of Hughes research laboratories built the first working LASER….Ruby Laser.Schawlow was Town’s brother in-law

Schawlow

In 1985, Paghidiwala, tested the erbium-doped solid state laser (Er:YAG) on dental hard tissue.

THE PHYSICS OF LASER

The term Laser is self explanatory. It describes the whole process of light generation. It involves transforming various forms of energy into a specialized form of ‘’optical’’ energy.Specialized materials are used to transform this various of energy.Though the initial energy are of low wavelength they are further amplified.

Basic component parts of LASER1. Active/gain/laser medium: Gas-argon, CO2

Liquid- Semi-conductor (diode)-Gallium, arsenide, aluminium, indium Solid-state (solid crystal or glass matrix)- Nd:YAG, Er:YAG

Stimulation of the laser medium causes one of its electrons to drop from a higher energy state (Q1) to a lower energy state (Q2), releasing light energy – a process referred to as stimulated emission of radiation.

The stimulated emission of photon by an excited atom, which triggers the release of a subsequent photon is responsible for the generation of coherant, monochromatic and collimated form of light or LASER.

2. Pump/energy source: F-A-C-E Flash light Arc light Chemical reaction Electrical discharge

The amplified light from the laser machine is what is referred to as the laser beam.

3. Optical resonator/cavity: Laser produced by the active medium is bounce back and forth through the laser cavity with two mirrors at both ends. The proximal mirror have some reflective property which allow some laser to escape to target tissue. 4. Delivery system: dependent on the wavelength of the laser. It could be quartz fiber-optic flexible hollow waveguide an articulated arm (incorporating mirrors) a hand-piece containing the laser unit

Characteristics of laser beam a. Monochromatic: one color of energy hence, a single wavelength b. Directional: collimation…..intensely focused energy beam which interacts with the target tissue. They do not diverge

c. Coherent: wavelength is of same size and shape

Classification of laser1) According to the mode of emission2) According to Power 3) According to the Emitting Material i.e. laser medium4) According to tissue acted upon5) According to clinical uses6) According to mode of transmission7) According to thermal interactions of tissue8) According to their harmful effect

1. Based on the mode of emission:a. fractionating- periodic alternations of the laser energy being on and

off, similar to a blinking light. b. Continuous wave- laser energy is emitted continuously as long as

the laser is activated—and produces constant tissue interaction c. Pulsed- Free-running pulse emission occurs with very short bursts of

laser energy due to a flash lamp pumping mechanism

2. According to Power a. High power: These lasers increase tissue kinetic energy and produce heat. As a result, they leave their therapeutic effects through thermal interactions. b. Medium power: These lasers leave their therapeutic effects without producing significant heat. c. Low power: These lasers have no thermal effect on tissues and produce a reaction in cells through light, called photo-biostimulation or photo-biochemical reaction. Output power of these lasers is less than 250 mW, e.g. diode laser.

3. Based on the Emitting Material a. Gas lasers—Argon, CO2 lasers b. Solid state lasers—Nd:YAG, Er:YAG, Ho: YAG c. Semiconductors—Diode lasers.

4. According to tissue acted upona. Soft tissue laser ( LLLT): low energy wavelength, cuts tissue by coagulation, vapourization and carbonizationSeal capillaries and nerve endingsResultant painless post-operative proceduresSoft tissue heal faster

b. Hard tissue laser: longer wavelength, cuts the tissue by ablation,Cut into bone and teethPrepare tooth surfaces before bondingrepair certain worn down dental restorations.

5. Classification of lasers based on their clinical usesLaser type Wavelength Main current clinical usesArgon 488, 514.5 nm Curing, soft tissue desensitizationDiode 800-830, Soft tissue, periodontics 950-1010 nm Nd: YAG 1064 nm Soft tissue, periodontics, desensitization, analgesia, tooth whitening, and endodonticsEr: YSGG 2.79 μm (2,790nm) Hard tissueEr: YAG 2.94 μm (2,940nm) Hard tissue

CO2 10.6 μm (10,600nm Soft tissue, desensitization

Key:Nd: YAG: Neodymium: yttrium-aluminium-garnet, Er: YSGG: Erbium doped yttrium scandium gallium garnet

6. According to mode of transmissiona. Glass fibre-optic system-CO2 Laserb. Mirror system: Nd: YAG, Argon, He-Ne laser, Diode lasers

7. Classification based on thermal interactions of tissueTemperature (°C) Tissue effectsa. 42-45 Hyperthermia (transient)b. >65 Desiccation, protein denaturation and coagulationc. 70-90 Tissue weldingd. >100 Vaporizatione. >200 Carbonization and charring

8. Based on harmful effect of laser Class I: Low powered lasers that are safe to view‑Class IIa: low powered visible lasers. ‑ Do not cause damage unless one looks directly along the beam for longer than 1,000 sClass IIb: Low powered visible lasers.‑ Dangerous when viewed along the beam for longer than 0.25 s

Class IIIa: These are medium powered lasers that are not dangerous ‑when viewed for less than0.25 s

Class IIIb: These are medium powered lasers that are dangerous when ‑viewed directly along the beam for any length of time

Class IV: These are dangerous high powered lasers that can cause ‑damage to the skin and eyes. Even the reflected or radiated beams are dangerous. Most of the lasers used for medical and dental purposes are in this category.

Wavelengths of dental laser

Tissue interaction of laser

Transmission and reflection have no effect on the target tissue.

There is undesirable transfer of energy to non-target tissue when scattering occurs.

Of great importance is the absorption

Laser require chromophore to absorb it. Intra-orally they include melanin, water and haemoglobin.

Precautions before and during irradiation:- a) Glasses for eye protection. b) Prevent inadvertent irradiation. c) Protect patients throat, oral tissues. d) Use wet gauze packs to avoid reflection from shinny metal surfaces. e) Ensure adequate high speed evacuation.

Laser selection in orthodonticsFactors that guide selection1. Procedure specificity2. Ease of operation3. Portability4. Cost

The most common lasers used in dentistry today are the CO2 laser, the Nd:YAG laser, the erbium lasers (Er:YAG and Er,Cr:YSGG). However, the large size and cost of CO2 and Nd:YAG laser makes it difficult to use in orthodontics.

Why orthodontist prefer the diode laserA. No risk of damage to adjacent tooth structureB. Excellent hemostasisC. Dry-field operationD. Light contact of the fiber tip with tissueE. Proprioceptive feedbackF. PortabilityIts wavelengths is easily absorbed by melanin (soft tissue pigmentation) and hemoglobin, and poorly absorbed by enamel and water.

Laser application in orthodonticsA. DIRECT CLINICAL APPLICATION1. Acceleration of tooth movement2. Bone remodeling, 3. Enamel etching prior to bonding4. Debonding of ceramic brackets 5. Pain reduction during orthodontic force application6. Prevention of enamel demineralization.

B. ADJUNCTIVE CLINICAL APPLICATION1. Gingivectomy2. Gingivoplasty3. Frenectomy4. Soft tissue exposure prior to traction

LASER ANALGESIA DURING ORTHODONTIC FORCE APPLICATION

Commonly used lasers are the low-level laser therapy (LLLT) GaAlAs diode laser, localised CO2 laser

Prevent temperature rise above 36.5°C in target tissue.

Has non thermal and bio-stimulatory effects.‑

Affect the synthesis, release and metabolism of serotonin acetylcholine centrally and prostaglandins and histamines peripherally.

NB: some studies in the literature have shown that LLLT offers no significant pain reduction after separation or placement of arch wires.

LASER ACCELERATED TOOTH MOVEMENT

Induction of the receptor activator of the nuclear factor kappa B ‑(RANK) and RANKL (Fujita et al., 2008).

Stimulating osteoclastic and osteoblastic cell proliferation and function

Commonly used laser is the GaAlAs diode laser

LASER-ASSISTED BONE REGENERATIONTwo principlesa. Cellular proliferationb. Cellular differentiation into committed precursors

This could possibly inhibits relapse and reduces the retention period by accelerating bone regeneration in the mid-palatal suture after RME.

LLLT has positive effects on wound healing through acceleration of bone regeneration and stimulation of trabecular osteoid tissue formation.

LASER ENAMEL ETCHING DURING BONDING PROCEDURES

Conventional MethodAcid-etching with 37%phosphoric acid leaves a rough micro-fissured surfaceShortcomings: a. Susceptibility of the enamel to long term acid attack in the futureb. High prevalence of white spot lesion among orthodontic patient. Poly-acrylic acid etching and sand blasting were also investigated to overcome these shortcomings.

Mechanism of laser-etching There is thermal induced changes of the enamel.

Resultant localised melting of the hydroxyl-apatite and ablation of enamel.

Laser etching produces a fractured, uneven surface and open dentin tubules, which is ideal for adhesion.

Advantages of laser etching Painless Nil vibration hence, no smear layer Acid resistant surface- by altering the Ca-PO3 ratio, reduces the

carbonate to phosphate ratio, reduces water and organic component ‑ ‑content thereby forming more stable and less acid soluble compounds. This reduce acid attack is very promising to the orthodontist.

Time saving: Nil water spraying, nil drying. Er-YAG, Nd:YAG, Cr:YSGG.NB: some researchers believe that Nd-YAG etching produce lower bond strength

Laser curing of light-cured materials

Conventional methods include the use of light emitting diode (LED), plasma arc, quartz-tungsten-halogen (QTH).SHORTCOMINGS:a. QTH light intensity depreciate overtime which becomes less optimal for

curingb. light produced by QTH devices has a wide wavelength range, including

both ultraviolet and visible lights necessitating the use of special filters to select blue light for emission.

c. Longer curing period of between 20-40 sec for QTH and LED however, with plasma arc this was reduced to about 2-4 sec but with resultant reduced bond strength.

Advantages of laser-assisted curingThe peak of argon laser emission (488nm) matches well with the photo-

initiator, camphorquinoneCuring is 4 times fasterPossible higher bond strengthLower pump chamber temperature increase with less thermal risk of pulp

damage.

NB: High cost of argon laser has made it impossible for routine usage. The portability and affordability has made diode lasers better choice.

Laser bonding to porcelain37% phosphoric acid not suitable for bonding to porcelain surface

Conventional 9.6% hydrofluoric acid when used stand the risk of damaging teeth and adjacent soft tissue.

However, with laser:No risk of potential gingival burnAcceptable bond strengthUpon bracket debonding no need to re-polish the porcelainShorter etching time.Nd:YAG can be used.

Laser-assisted acid resistance of enamel to prevent white spot lesion

Orthodontic patients on fixed therapy are faced with the risk of enamel decalcificationConventional preventive measures:Daily fluoride mouth rinse: Possible burn outUse of fluoride releasing composite resin conventional RMGic: these

adhesives result in lower bond strength.Casein phosphopeptide-amorphous calcium phosphate (CPP-ACP).

Mechanism of laser-assisted acid resistanceSurface meltingPartial fusion and recrystallization of enamel prism thereby sealin g

up the enamel surfacesChanges in enamel organic matrix

Resultant effects include:Decreased enamel demineralizationDecreased loss of tooth structure reduced threshold pH at which dissolution occurred by about a factor of five.

NB: The treatment is carried out the area susceptible to caries.

Laser-assisted ceramic bracket debondingComplications of conventional ceramic brackets debonding;From using debonding pliersEnamel fracture: because the debonding strength of ceramic bracket

is greater than that of enamel. Ceramic brackets also have low fracture toughness

Enamel cracksIngestion of brackets fragments: ceramic brackets are brittleDamaged to the eye: as the bracket fractures and scatters

From using ultrasonic and electro-thermal devicesDamage to pulp from the heat generated

Laser debondingCeramic brackets absorbs the wavelength thereby softening the resin.

Advantages:No enamel tear nil bracket failureNil painLess debonding forceLess chair side time

LASER MINOR SURGERIES

ADVANTAGES1. Coagulates blood vessels2. Seals lymphatic3. Sterilizes the wound during ablation, reducing the risk of blood-borne

transmission of disease 4. Maintains a clear and clean surgical field. 5. Topical anesthesia commonly used6. Less post-operation discomfort7. Minimal swelling8. Suturing not required9. Few analgesia required10. Less wound contraction, less scaring

DisadvantagesNot cost effectiveLess tactile strength especially for non-contact laser e.g. erbium laserTissue desiccationPoor wound healing

Adjunctive clinical applications1. Gingivectomy: Indicationsa. For Establishing Tooth Proportionality before Bracket Placementb. Crown lengtheningc. Crown height asymmetriesAdvantagesd. Because the soft-tissue laser seals the incision as it is made, brackets can be

placed immediately after the procedure, and healing of the tissue follows.e. Ideal bracket positioning is achieved

2. Gingivoplasty: to recontour the gingival when there is inflammation 3. Frenectomy: in managing mid-line diastema4. Fibrotomy (pericision): less invasive than the conventional circumferential supracrestal fibrotomy (CSF) hence, easily accepted by patients.5. Exposure of TAD’s6. Exposure of unerupted teeth

Laboratory proceduresLaser welding:Conventional methods include:Pressure weldingSpot weldingWith laser welding there is greater mechanical strength.

Others 1. Laser scanning: for soft-tissue scanning and a valuable tool with

ease of application and creation of 3D images. 2. Laser fluorescence: Laser light induced fluorescence can be used as

a diagnostic method for detection of enamel caries at an early stage. This is invaluable for detecting white spot lesions

In summary…laser in orthodontics

Conclusion The speculations, hypothesis and theories of yesterday for an excellent tomorrow is available today. If it must become our routine orthodontic tool for tomorrow we must be ready to accept and develop on the knowledge today.

References

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041014, 2014.