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Information about Lasers

Published on May 11, 2009

Author: saurabhchandra


Slide 1: Lasers in Endodontics & Conservative Dentistry Slide 3: L Light A Amplification by S Stimulated E Emission of R Radiation Slide 4: A laser is a device that transforms light of various frequencies into a chromatic radiation in the visible, infrared, and ultraviolet regions with all the waves in phase capable of mobilizing immense heat and power when focused at close range Historical Perspective… : Historical Perspective… Early 1900’s – Chinese & Egyptians (Phototherapy) 1960 – Theodore Maiman 1965 – Dr. Leon Goldman 1970’s – Nd:YAG 1982 - Pick, Frame & Pecaro 1987 – Meyer’s Portable Laser Slide 6: Stern & Sognnaes (1964) and Goldman et al (1964) were the first to investigate the potential uses of the ruby laser in dentistry They began their laser studies on hard dental tissues by investigating the possible use of a ruby laser to reduce subsurface demineralization The first laser use in endodontics was reported by Weichman & Johnson (1971) who attempted to seal the apical foramen in vitro by means of a high power-infrared (CO2) laser Fundamentals of Lasers : Fundamentals of Lasers Slide 8: Light beam is composed of packets of energy known as PHOTONS Ground State – Atoms are normal position Atoms are excited by an energy source and move to a higher energy As it reverts back to its ground state, energy is emitted – Spontaneous Emission Results without external interference and forms waves that are in phase Light : Light Amplification : Amplification Is a part of a process that occurs inside the laser An optical cavity is at the center of the laser device & the core is comprised of chemical elements, molecules or compounds – “Active Medium” Lasers are generically named for the material of the active medium Gas, Crystals or Semi-Conductors Slide 17: Gas – Co2 & Argon Solid state semi conductors : With metals like – Gallium, Aluminum, Indium, Arsenic With solid rods of garnet crystal growth with various combinations of Yytrium, Aluminum, Scandium, Gallium and then doped with elements of Chromium, Neodynium or Erbium. Slide 18: The crystal or gas is excited to emit photons of a characteristic wavelength These ware amplified and filtered to make a coherent beam The effect of this energy depends on whether or not the WL of the energy is absorbed by the surface or not Stimulated Emission : Stimulated Emission Quantum theory of Max Planck & Neils Bohr Smallest unit of energy It can be absorbed by electrons, cause brief excitation and then the quatum is released – Process called as Spontaneous Emission Radiation : Radiation Refers to light waves produced by the laser as electromagnetic energy EM Spectrum – entire range Wavelength’s Higher Photon energy can deeply penetrate biologic tissues and produce charged atoms and molecules Slide 22: All dental lasers have emission wave lengths of 0.5µm (500 nm) to 10.6µm (10,600 nm) Within the visible or invisible infrared non-ionizing EM range & emit thermal radiation The dividing line between ionizing and non-ionizing portion is on the junction of ultraviolet and visible violet light Slide 25: Active medium – Gas, liquid or solid Contained in glass or ceramic tubes Energy – Electric current Mirrors are added to each end to increase the back and forth movement of photons Thus increasing the stimulation of emission of radiation Laser Delivery Systems : Laser Delivery Systems Coherent, Collimated beam of laser light must be delivered to the target tissue Two delivery systems that are employed Hollow Waveguide or Tube Glass fiber optic cable Flexible Hollow Waveguide (Tube) : Flexible Hollow Waveguide (Tube) Has an interior finish mirror Laser energy is reflected along this tube and exits through a hand piece Strikes the tissue in a non-contact manner An accessory tip of sapphire or hollow metal can be connected Glass Fiber optic cable : Glass Fiber optic cable More flexible than waveguide Less weight and less resistance in movement Smaller diameter (200-600 µm) Glass component is encased in a resilient sheath Fragile & can’t be bent in sharp angles Used in contact and non-contact mode Fiber Optic : Fiber Optic Advantages : Advantages Thinner & flexible Higher carrying capacity Less energy degradation Low power consumption Non – inflammable Light weight Laser Emission Modes : Laser Emission Modes Dental lasers can emit light energy in 2 modalities Constant ON Pulsed ON/OFF In Constant or Continuous Wave, the beam is emitted at one power In Gated Pulse Mode, there are periodic alterations of laser energy (Blinking light) Slide 34: This is achieved by the opening and closing of a mechanical shutter in front of the beam path of a continuous wave emission All surgical lasers that operate in continuous wave have this gated pulse feature Third mode is termed Free running pulsed mode or True Pulsed In this large peak of energy of laser light is emitted for a very short time What does the Operator control? : What does the Operator control? Classifications: : Classifications: Lasers are named according to: Active medium Wavelength Delivery systems Emission modes Tissue absorption Clinical Application Classifications: : Classifications: Based on Active Medium Solid State Gas Semiconductors Excimer Dye Mode of action Contact mode (focused or defocused) - Ho:YAG ; Nd: YAG Non-contact mode (focused or defocused) - CO2 Slide 40: III. Based as application Soft tissue laser - Argon, Co2, diode; Nd:YAG. Hard tissue laser - Er : YAG Resin curing laser - Argon IV. Based on Level of energy emission: Soft lasers (Low level energy): He-Neon; Ga-Arsenide. Hard lasers (High level energy): Er:YAG laser ; Nd: YAG laser. Wavelength : Wavelength Argon : Argon Active medium is Argon gas Fiber optically delivered Continuous wave & Gated Pulsed modes Only laser whose light is in the visible spectrum 2 wavelengths are used: 488 nm (Blue) 514 nm (Blue-Green) Slide 45: 488 nm emission is used to activate camphoroquinone in composite resins The beam divergence of this blue light is used in non-contact mode, produces excessive amount of photons thus providing curing energy More strength in cured resin when compared to conventional blue light Shorter curing time Slide 46: 514 nm has its peak absorption in tissues containing Hb, Hemosiderin and Melanin Has excellent hemostatic capabilities Small diameter flexible glass fiber is used for delivery Used in contact mode Used in Surgical Endodontics Acute inflammatory Periodontal conditions and highly vascularized lesions such as Hemangioma Slide 47: Neither wavelength is absorbed by dental tissues or water Their poor absorption by enamel and dentin is an advantage when used for incising and sculpting gingival tissues Minimal interaction and no damage to tooth surface Both can be used for caries detection Argon laser light illuminates the tooth, the disease area appears dark orange-red colored Diode : Diode Is a solid active medium laser Manufactured from semiconductor crystals using combinations of Al, In, Ga and Ar Available wavelengths are 800 nm (Al) to 980 nm (In), placing them at the beginning of the infra red spectrum Fiber optic delivered Continuous wave or Gated Pulse modes Used in Contact mode Slide 49: Diode WL are highly absorbed by pigmented tissue and deeply penetrating, though hemostasis is not as rapid as with Argon laser Poorly absorbed by tooth tissues Soft tissue surgeries can be performed near tooth Causes a rapid increase in temperature thus, surgical site needs to be air or water cooled Diode is an excellent soft tissue surgical laser Small size & Portable Slide 50: Diagnodent (Kavo) is a visible red diode with a WL of 655 nm and 1 milliwatt power This red energy excites fluorescence from carious tooth structure, which is reflected back into a detector device in the unit This analyses and quantifies the degree of caries Neodynium:YAG (Nd:YAG) : Neodynium:YAG (Nd:YAG) Has a solid state active medium, which is a garnet crystal combined with rare earth elements Yytrium & Aluminum doped with Neodynium Wavelength is 1064 nm Operate in free running pulsed mode with short pulse durations Delivered via fiber optic cable Contact mode Slide 53: Laser light is highly absorbed by melanin Clinical applications include cutting and coagulating soft tissues Energy is slightly absorbed by dental hard tissues but there is little interaction between sound tooth structure following soft tissue surgery Pigmented surface carious lesions can be vaporized without removing the healthy surrounding enamel Holmium:YAG : Holmium:YAG Consists of a solid crystal of Yytrium, Aluminum Garnet sensitized with Chromium and doped with Holmium and Thulium ions Delivered via Fiber optic cable Free running pulsed mode Wavelength is 2100 nm Absorbed by water 1000 times more than Nd:YAG Slide 56: Using peak powers it can ablate hard calcified tissues As a soft tissue laser instrument it does not react with Hb or other tissue pigments Used more in TMJ disorders and Orthopedic cases The Erbium Family : The Erbium Family 2 distinct lasers Erbium Chromium: YSGG Erbium:YAG Er Cr:YSGG : Er Cr:YSGG Erbium Chromium:Yytrium Scandium Gallium Garnet Wavelength – 2780 nm Delivered via fiber optics Free running pulsed mode Fiber cable diameter is much larger and requires an air or water coolant Er:YAG : Er:YAG Erbium: Yytrium, Aluminum Garnet Wavelength is 2940 nm Delivered via hollow tube and fiber optic cable Free running pulsed mode Slide 60: These 2 WL’s have the highest absorption in water and have high affinity for hydroxyapatite The laser couples into hydroxyl radical in the apatite crystal and into water that is bound to the crystalline structures of tooth Caries removal and tooth preparation can be easily carried out The increased water content in carious lesions allows the laser to preferentially interact with diseased tissue Slide 62: This is the most efficient laser for drilling and cutting enamel as its energy is well absorbed by hydroxyapatite CO2 : CO2 Gas active medium laser Co2 pumped via electrical discharge current and is present in a sealed tube Wavelength is 10,600 nm Delivered via hollow tube or wave guide Continuous or Gated pulsed mode Slide 64: Well absorbed by all biological hard & soft tissues Can easily cut and coagulate soft tissue Has a shallow depth of penetration into tissue The laser energy is delivered by a hollow wave guide in a non contact fashion This WL has the highest absorption in hydroxyapatite of any dental laser Thus tooth must be protected during soft tissue application Slide 65: Its high thermal absorption makes the CO2 laser less suitable for cutting and drilling enamel & dentin as the damage to the dental pulp may occur (Ref: Seltzer & Bender, Quintessence 2002) Laser – Tissue Interaction : Laser – Tissue Interaction Laser light has four different interactions with the target tissue Amount of energy absorbed by the tissue depends on the tissue characteristics such as pigmentation and water content Slide 69: Dental structures have different amount of water content, Enamel being the least followed by Dentin, Bone, Calculus, Caries and Soft tissue Dental lasers have a Photothermal effect Slide 70: At low temperatures below 100°C, the thermal effects denature proteins and produce hemolysis They cause coagulation & shrinkage Above 400°C, carbonization of organic materials occurs with onset of some inorganic materials Between 400°C & 1200°C, inorganic constituents melt, re-crystallize or vaporize Slide 71: In general, shorter WL (500-1000 nm) are well absorbed in pigmented tissues and blood elements Longer WL are more interactive with water and Hydroxyapatite Co2 (10,600 nm) is well absorbed by water and has the highest affinity for Hydroxyapatite Lasers in Endodontics : Lasers in Endodontics Dental Hypersensitivity : Dental Hypersensitivity Characterized as short, sharp pain from exposed dentin that occurs in response to provoking stimuli such as cold, heat or chemicals Not ascribed to any other dental defect or pathology Can be attributed to non carious tooth loss (Wasting diseases) Slide 74: Various treatment modalities Blocking the dentinal fluid flow Application of various agents to exposed dentinal tubule Oxalate salts Isobutyl cyanoacrylate Fluoride releasing resins Reduce Neuronal Responsiveness 5% Potassium Nitrate & 10% Strontium Nitrate Laser as a treatment modality : Laser as a treatment modality Rationale for laser induced reduction in DH is based on 2 possible mechanisms 1st mechanism – implies direct effect of laser irradiation on the electric activity of nerve fibers within the dental pulp 2nd mechanism – modification of the tubular structure of dentin by melting and fusing of the hard tissue or smear layer and subsequent sealing of dentinal tubules Slide 76: Lasers for treatment of DH are divided into 2 groups: Slide 77: Low output lasers were used by Kimura et al for their anti-inflammatory effect Have an ability to stimulate the nerve cells Senda et al were the first to apply He-Ne lasers Used a low power output of 6 mW which does not affect the morphology of dentin and enamel It allows a small fraction of the energy to reach the pulp Slide 78: The mechanism of action is not clear but it was claimed that the helium – neon laser irradiation affects the electric activity (action potential) rather than A-d or C-fiber nociceptors Slide 79: Gallium-Aluminum-Arsenide diode have 3 WL (780, 830 & 900 nm) Matsumoto et al applied an output of 30 mW in a continuous wave for 0.5 – 3 mins The analgesic effect was due to a depressed nerve transmission caused by diode laser irradiation blocking the depolarization of C-fiber afferents Slide 80: In 1972, Kantola et al used a Co2 laser to create craters on dentin Microradiography and Electron probe analysis revealed higher levels of Ca & P in the fused or recrystallized dentin At a 1 year follow up, it was observed that in laser irradiated dentin, recrystallization had occurred and dentin had changed to look like the original Slide 81: (Ref: IEJ, 33, 173–185, 2000) Pulp Diagnosis : Pulp Diagnosis Laser Doppler flowmetry (LDF) was developed to assess blood flow in microvascular systems, e.g. in the retina, gut mesentery, renal cortex and skin (Morikawa et al. 1971, Riva et al. 1972) Slide 83: Helium – Neon and Diode laser at a low power of 1 or 2 mW Wavelength is 632.8 nm Laser beam is directed towards the tooth (to the blood vessels) Moving RBC causes the frequency of the laser beam to be Doppler shifted and some of the light be back scattered out of the tooth Slide 84: The reflected light is detected by the photocell on the tooth surface and its output proportional to the number and velocity of the blood cells Advantages over EPT: Can be used in traumatized teeth Does not rely on painful sensation to determine vitality Slide 86: (REF: Australian Dental Journal 2003;48:3.) Pulp Capping & Pulpotomy : Pulp Capping & Pulpotomy AAE defines Pulp capping as a procedure in which a dental material such as Calcium hydroxide or MTA is placed over a pulpal wound to encourage the formation of reparative dentin Pulpotomy is defined as the surgical removal of the coronal portion of the pulp by means of preserving the remaining radicular tissues Pulp Capping & Pulpotomy : Pulp Capping & Pulpotomy Melcer et al used Co2 lasers & demonstrated new mineralized dentin formation without cellular modifications in pulpal tissues Shoji et al used Co2 lasers in different WL and reported that no damage was detected in the radicular pulp. Charring, coagulation necrosis and degeneration of odontoblastic layer occurred, with no pulp damage Jukic et al used Co2 and Nd:YAG lasers on exposed pulp tissue and reported that a dentinal bridge was formed Slide 89: Moritz et al used Co2 laser for direct pulp capping The energy level of 1 W at 0.1 second exposure time with 1 second pulse intervals was applied to the exposed pulp Teeth were check for vitality after 6 and 12 months and 89.4% of the teeth retained their vitality Lasers can be used for direct or in direct pulp capping in cases of deep and hypersensitive cavities - Slide 90: Co2 and Nd:YAG lasers are well absorbed by the hydroxyapatite of enamel and dentin, causing tissue ablation, melting and re-solidification These lasers do not cause any thermal damage to the pulp tissue and do not increase the intra-pulpal temperature – if used at the correct power, duration of time and intensity Cleaning & Shaping of Root Canal System : Cleaning & Shaping of Root Canal System Various laser systems can deliver the energy into the root canal using a thin optical fiber Various systems that have been used are Nd:YAG Er,Cr:YSGG Argon Diode Er:YAG Slide 92: It has been demonstrated in many studies that the laser radiation has the ability to remove debris and smear layer from the root canals It also has the potential to kill the microorganisms Bergman et al suggested that lasers is not an alternative to the conventional cleaning & shaping, but can be used as an adjunct Limitations for use in Root Canals : Limitations for use in Root Canals Emission of laser energy from the tip of optical fiber or the laser when directed into the root canal is not uniform There may be thermal damage to the periapical tissues May be hazardous when the tooth apex is near vital structures such as mandibular nerve or mental foramen Slide 94: Stabholz et al developed a new endodontic tip that can be used with Er:YAG laser It is delivered via a hollow tube allows lateral emission of the irradiation (side-firing), rather than direct emission through a single opening The endodontic side firing spiral tip is designed to fit the shape and volume of the root canals prepared by NiTi rotary instruments Slide 95: The tip is sealed at its far end, preventing irradiation to the periapical tissues In a recent study, the efficacy in smear & debris removal of the side firing tip was compared to ProTaper The RCLase Side firing tip was used in extracted molars and the teeth were then split and examined longitudinally Efficient cleansing of the RC System is achieved Sterilization of root canals : Sterilization of root canals Numerous studies into the sterilization of root canals have been performed using CO2 (Zakariasen et al. 1986) and Nd:YAG lasers (Rooney et al. 1994, Ebihara et al. 1994, Fegan & Steiman 1995, Moshonov et al. 1995b, Goodis et al. 1995, Sekine et al.) The Nd:YAG laser is more popular, because a thin fibre-optic delivery system for entering narrow root canals is available with this device Slide 99: Many other lasers such as the XeCl laser emitting at 308 nm (Stabholz et al. 1993), the Er:YAG laser emitted at 2.64 mm (Gomi et al. 1997), a diode laser emitting at 810 nm (Moritz et al. 1997a), and the Nd:YAP laser emitting at 1.34 mm (Blum et al. 1997) have also been used All lasers have a bactericidal effect at high power that is dependent on each laser Slide 100: There appears to exist a potential for spreading bacterial contamination from the root canal to the patient and the dental team via the smoke produced by the laser, which can cause bacterial dissemination (Hardee et al. 1994) Thus, precautions such as a strong vacuum pump system must be taken to protect against spreading infections when using lasers in the root canal (McKinley & Ludlow 1994) Sterilization of root canals by lasers is problematical since thermal injury to periodontal tissues is possible Laser assisted Obturation : Aim of Obturation: Eliminate all avenues of leakage Seal the RC system from all ends Rationale in using lasers for obturation is that the irradiation can be used as a heat source for softening the GP Conditioning of the dentin walls can also be done Laser assisted Obturation Slide 102: The photo-polymerization of camphorquinone-activated resins for obturation is possible using an Ar laser emitting at 477 and 488 nm (Potts & Petrou 1990, 1991) The results indicate that an Ar laser coupled to an optical fiber could become a useful modality in endodontic therapy Studies have been performed using the obturation material AH-26 & AH Plus (Zaman et al. 1994) and composite resin (Anic et al. 1995) Slide 103: An SEM examination revealed that laterally compacted resin fillings showed fewer voids than those obtained by vertical compaction (Kitamura et al, 2005) Ar, CO2, and Nd:YAG lasers have been used to soften gutta-percha (Anic & Matsumoto 1995), and results indicate that the Ar laser can be used for this purpose to produce a good apical seal Slide 104: The clinical evidence from reported studies for the use of lasers in obturation is not sufficient It has not been determined if the use of laser as a heat source is safe for the surrounding structures of the tooth as well as for other teeth A suitable wavelength has not been ascertained Effect on the sealer per se has to be determined Retreatment : Retreatment Rationale for using lasers in retreatment is ascribed to the need to remove foreign material, GP etc by softening it by heat Farge et al used the Nd:YAP (1340 nm) Attempted to remove GP and ZOE sealer Silver cones and separated instruments They concluded that lasers alone cannot remove all the obturating materials from the RC Slide 106: Yu et al were able to remove the entire filling material in 70% cases, while broken files in only 55% of the cases using the Nd:YAG laser Removal of GP and files is always a challenge and lasers can only assist A clinical advantage is that toxic solvents like xylene can be avoided However the effects of the laser on the tissues and surrounding teeth remains to be studied Lasers in Endodontic Surgery : Lasers in Endodontic Surgery Weichman & Johnson attempted to seal the apical foramen of freshly extracted teeth in which the pulp had been removed Laser is used for the surgery, a bloodless surgical field should be easier to achieve due to the ability of the laser to vaporize tissue and coagulate and seal small blood vessels Slide 108: If the cut surface is irradiated, the surface is sterilized and sealed The potential of the Er:YAG laser to cut hard dental tissues without significant thermal or structural damage eliminates the need for mechanical drills Clinical investigations into laser use for apicectomy began with the CO2 laser (Miserendino 1988), which was successful Slide 109: The use of this laser seals the dentinal tubules in the apical portion of the root and sterilizes the surgical site On, extracted teeth (Stabholz et al. 1992 Arens et al. 1993, Wong et al. 1994), used the Nd:YAG laser and found that there was a reduction in the penetration of dye or bacteria within resected roots When the laser was used for resection itself, either in extracted human teeth in vitro (Maillet et al. 1996), found that tissue repairs was quicker when compared with those roots resected with a bur Advantages : Advantages Good hemostasis Improved visualization of surgical site Sterilization operative field Reduced permeability of root surface dentin Reduction in post operative pain Reduced risk of contamination of surgical site by eliminating use of air turbines Constraints : Constraints Time Consuming Increase temperature Cause irreversible pulpal damage Needs precise execution Increased cost of treatment Healing after Laser Surgery : Healing after Laser Surgery Reports suggest that laser created wounds heal more quickly and produce less scar tissue than conventional scalpel surgery. However, contrary evidence from studies in pigs, rats and dogs indicate that the healing of laser wounds is delayed More initial tissue damage may result, and that wounds have less tensile strength during the early phase of healing (Pick et al 1990) Slide 114: Abergel et al (1984) experimented with cultured human skin fibroblasts and showed that collagen production and DNA synthesis were delayed when the fibroblasts were exposed to Nd: YAG laser radiation Crespi et al evaluated the effects of CO2 laser treatment on fibroblast attachment to root surfaces and concluded that CO2 laser treatment in defocused, pulsed mode with a low power of 2W combined with mechanical instrumentation constitutes a useful tool to condition the root surface and increase fibroblast attachment to root surfaces (Ref: Journal of Periodontology) Other Endodontic uses : Other Endodontic uses CO2 and Nd:YAG lasers have been used for the attempted treatment of root fractures (Arakawa et al. 1996). However, regardless of the re-approximation technique, laser type, energy, and other parameters used, fusion of the fractured root halves was not achieved Lasers (Ar, CO2, Nd:YAG lasers) have been used successfully to sterilize dental instruments (Adrian & Gross 1979, Hooks et al. 1980, Powell & Whisenant 1991). Slide 116: Results indicated all three lasers (Ar, CO2, Nd:YAG lasers) are capable of sterilizing selected dental instruments; however, the argon laser was able to do so consistenly at the lowest energy level of 1 W for 2 min A pulsed dye laser emitted at 504 nm was used for the removal of a calcified attached denticle (Rocca et al. 1994) Lasers in Operative & Aesthetic Dentistry : Lasers in Operative & Aesthetic Dentistry Lasers have become a part of routine operative and aesthetic practice There are five lasers that are currently in the armamentarium Argon lasers : Argon lasers The wavelength is absorbed by Hb This attribute allows precision cutting, hemostasis & coagulation of vascular tissue Use of argon lasers have been used for curing composites (at low power achieving higher bond strength) Transillumination in diagnosis of tooth fractuures Plasma Arc Curing (PAC) : Plasma Arc Curing (PAC) PAC & Argon laser curing systems have rapid polymerization of composites However they increase heat generation and polymerization shrinkage stresses Studies have shown that they exhibit a narrow spectral output and do not coincide with the spectral requirements of all restorative resins Bleaching of stained teeth Co2 Lasers : Co2 Lasers Used for vaporizing, cutting and coagulation of soft tissue Used more for soft tissue procedures which include gingival re-modelling and shaping in aesthetic dentistry (Perio-Aesthetics) Diode Lasers : Diode Lasers 2 different WL are used Ga-Al-As Laser (800 nm) & In-Ga-As (980 nm) These are used in contact mode for cavity preparation, removal of bacterial contamination and coagulation of tissue Also used for Diagnosis Erbium Family : Erbium Family Er lasers are absorbed by Hydroxyapatite and water Allows to cut soft tissue, tooth structure and bone Er:YAG (2940 nm) cuts teeth easily & quickly Also used for removal of caries (excavation) Slide 124: Decay present on the facial of the maxillary left lateral incisor The Erbium laser used to remove the decay. No anesthesia was required After caries removal and preparation is complete Definitive direct bonded restoration after preparation with the Erbium laser Etching : Etching Laser etching has been evaluated as an alternative to acid etching of enamel and dentine. The Er:YAG laser produces micro-explosions during hard tissue ablation that result in microscopic and macroscopic irregularities These micro irregularities make the enamel surface micro retentive and may offer a mechanism of adhesion without acid-etching Slide 126: However, it has been shown that adhesion to dental hard tissues after Er: YAG laser etching is inferior to that obtained after conventional acid etching (Martinez-Insua et al., 2000) The weaker bond strength of the composite to laser-etched enamel and dentine to the presence of subsurface fissuring after laser radiation. This fissuring is not seen in conventional etched surfaces The subsurface fissuring contributed to the high prevalence of cohesive tooth fractures in bonding of both laser-etched enamel and dentine Caries prevention : Caries prevention Studies examined the possibility of using laser to prevent caries (Hossain et al., 2000; Apel et al., 2003) It is believed that laser irradiation of dental hard tissues modifies the calcium to phosphate ratio, reduces the carbonate to phosphorous ratio, and leads to the formation of more stable and less acid soluble compounds, reducing susceptibility to acid attack and caries Slide 128: Laboratory studies have indicated that enamel surfaces exposed to laser irradiation are more acid resistant than non-laser treated surfaces (Watanabe et al., 2001; Arimoto et al., 2001) The degree of protection against caries progression provided by the one-time initial laser treatment was reported to be comparable to daily fluoride treatment by a fluoride dentifrice (Featherstone, 2000) (Ref: Archives of Orofacial Sciences 2006; 1: 1-4) Laser Assisted Bleaching : Laser Assisted Bleaching Two laser-assisted whitening systems have been cleared by the FDA The laser is used to enhance the activation of bleaching material, which then whitens the teeth The argon laser wavelength of 488 nm for 30 seconds to accelerate the activity of the bleaching gel After the laser energy is applied, the gel is left in place for three minutes, then removed. This procedure is repeated four to six times Slide 130: Another system uses both the argon and CO2 lasers in the bleaching process The argon laser is used as previously described, then the CO2 laser is employed with another peroxide- based solution to promote penetration of the bleaching agent into the tooth to provide bleaching below the surface The entire clinical time for this system ranges from one hour to three hours Slide 131: Laser-assisted tooth bleaching, however, still poses a number of unanswered questions Because of continuing concerns and unknowns about laser interactions with hard tissue and the lack of controlled clinical studies, CO2 laser-assisted bleaching is not recommended (FDA) Based on previously accepted uses of argon lasers and associated temperature-rise studies, the use of the argon laser in place of a conventional curing light may be acceptable if the manufacturer’s suggested procedures are carefully followed (FDA) Dental Laser Safety : Dental Laser Safety Safety is an integral part of providing dental treatment with lasers 3 aspects to safety: Manufacturing process Proper operation of the device Personal protection Regulatory Agencies : Regulatory Agencies American National Standard Institute (ANSI) Food and Drug Administration (FDA) Center for devices and Radiological Health (CDRH) Occupational safety health administration (OSHA) Laser Classification : Laser Classification Fire & Explosion Hazards : Fire & Explosion Hazards Use only wet and fire retardant materials in operative field Use non combustible anesthetics Avoid alcohol based topical anesthetics Avoid alcohol moistened gauze or cotton Fire Extinguisher Stay informed Follow ANSI regulations Guidelines : Guidelines Mention outside Door Switch Fire hazards Eye Protection : Eye Protection In 1962, the awareness to eye protection began Eye is a critical target for laser injury Class III & IV lasers pose a threat to the eye Proper eye wear is a must Why the Eye ??? : Why the Eye ??? Cornea is made up of 90% Water Absorbs emissions from all lasers Cause Corneal Burns Holium and Erbium lasers affect the Aqueous and Vitreous Humor as well as the lens which lead to Aqueous Flare & Cataract formation Retinal damage occurs due to lasers with more depth if penetration and is absorbed into the pigments (Argon, Diode, He:Ne) Slide 139: The eye is 100,000 times more vulnerable to injury than the skin WL from 400-1400 Protective glasses must have an Optical Density of at least 4 For specific high WL lasers like Nd:YAG & Diodes, there are specific eye wear Eyewear is designed to have adequate protection for a wide range of WL’s Regardless of protection, NEVER look directly into the laser beam Sterilization & Infection Control : Sterilization & Infection Control Fiber optic cables & handpieces can be autoclaved in pouches Oil based aerosols must not be used The wires and protective casing / housing should be wiped clean and not autoclaved In Conclusion… : In Conclusion… Slide 142: Lasers – “New face of Dentistry” Diverse applications High Cost Treatment Planning Adverse Effects Worldwide laser sales by application : Worldwide laser sales by application ( Ref: Journal of Laser Application, Feb 2005) References : References Pathways of Pulp (9th Ed.) – S.Cohen Art & Science of Operative Dentistry – Sturdevant Textbook of Endodontics (6th Ed.)– Ingle DCNA – 2000, 2005 Journal of Endodontics International Endodontic Journal Journal of American Dental Association British Dental Journal

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