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Journal of | 2012 Vol. 20, No. 2 O SITI Parker etal. 2007;15(2):78-86 2007;15(2):78-86 J LaserDent Joel M.White,DDS,MS;HarveyA.Wigdor,MS Peter Rechmann,Prof.Dr.med.dent.;MichaelD.Swick,DMD; John D.B.Featherstone,MSc,PhD;GiuseppeIaria,DMD,GabiKesler,DMD; Steven P.A.Parker,BDS,LDS,MFGDP(CommitteeChair);ArunA.Darbar,BDS; Adopted March 2007 Position Paper: andResearch Science Committee, Academy ofLaser Dentistry Ablation of Intraoral Hard Tissues The Use of Laser Energy for Therapeutic O statement of scientific rationale. rationale. scientific of statement abrief with together in this publication istissues summarized hard of ablation the for in dentistry of use present The details.supporting for text the of to body paper, the then the and of key points the that highlights summary to bulleted initially the isreader referred The applications. other to describe suchpapers other several require will It improves. and changes astechnology updated and revised be will document The available. currently lasers utilizing to hard relevant tissues of dentistry, ablation the of aspects covers It document. historical as adetailed or review literature in March 2007. asacomprehensive is designed not paper The Directors of Board ALD bythe approved was paper position (ALD). This Dentistry Laser of Academy the of Committee Research and Science bythe developed in dentistry, lasers of uses various on papers position of series of a first is the This SYN EDIT N PAPERN OPSIS O R’S NO TE S U Continuous wave (CW) (CW CO (CW laser dioxide carbon wave (CW) • Continuous YAG (Nd:YAG,• Neodymium nm) 1064 necessary it is efficient, and effective • To therapeutically be light is to laser matched incident the of wavelength the • When • Water is naturally present among the crystals in enamel, in enamel, crystals the • Water among present is naturally nmby 2,800 at around is asmall there absorption • In addition, these for absorption in waterprimary is the absorption • The Er,Cr:YSGG• Both Er:YAG and are absorbed wavelengths laser YAG • Erbium Chromium (Er:YAG, nm) Erbium, and 2940 because of its very low absorption in hard tissues. in hard tissues. absorption low very its of because dentist restorative the to marginal benefit only of toshown be Nd:YAG the of significance clinical was wavelength laser the usage, effective and safe some have indicated studies tissues. excessheat into of surrounding the by conduction damage unwanted collateral causing thermal without change, tissue time to effect over energy sufficient lightto of deliver ablation. or and/ tissue change to causes heat which primarily is converted light energy band(s) tissue component, atarget of absorption 10,600 nm) 10,600 ascending water composition. water composition. ascending and tissue have, density carious relatively, mineral descending and cementum, bone, dentin, Enamel, pore. available every into tissue, the deep filling bone and cementum, dentin, water effects. bythe outweighed this is far but tissues, the of mineral hydroxyapatite (carbonated) the of group hydroxyl the nm. 3,000 around water band to broad due arelatively wavelengths two Er,Cr:YSGG. in water the than absorbed well in water, Er:YAG the with strongly more somewhat being preparation. in cavity use safe offer water. wavelengths primarily These tissue components, hard bytarget Er,Cr:YSGG are well absorbed wavelengths laser (Er,Cr:YSGG,YSGG 2780 nm) structure. bone and within heat buildup damaging and cracking, charring, of reports with enamel, with interactions poor showed laser MMARY . The commonly available continuous wave CO available commonly . The

. The pulsed Er:YAG pulsed . The and . While published published . While 2 , 2

POSITION PAPER

• For both Er:YAG and Er,Cr:YSGG laser wavelengths, the laser INTRODUCTION energy is absorbed primarily by the water and is rapidly Laser light is unique in being emitted as a monochromatic, converted to heat, which causes superheating of the coherent, and collimated beam of non-ionizing electromagnetic subsurface water, resulting in a disruptive expansion in (EM) energy which, for current dental purposes, spans the visible the tissue. and infrared regions of the EM spectrum. Through a correct • The currently marketed mid-infrared (IR) laser wavelength matching of incident laser wavelength with a target tissue element, lasers (around 3,000 nm) are free-running pulsed lasers. light energy is converted primarily to heat, which causes tissue If the correct energy is used, application results in safe change or ablation. pulpal temperature rises of less than 5°C. • Laser irradiation of enamel and dentin by Er:YAG or Er,Cr:YSGG For the present document the use of laser light for intra- lasers produces a “super-rough,” micro-cavitated surface. oral hard tissue ablation will be the treatment that is primarily discussed. Other uses and mechanisms are known, but these are • Studies have identified the fragility of laser-irradiated not the topic of the present paper. enamel, relative to the stability of the post-restoration margins. A combined approach of laser-irradiation In order for any laser-tissue interaction to be therapeutically and acid-etch techniques, to overcome such potential effective and efficient, it is necessary to deliver light energy of problems, is suggested. Regardless, there is the need to sufficient value over time to effect tissue change, without causing remove grossly overhanging and unsupported enamel to unwanted collateral thermal damage by conduction of excess heat provide a stable post-restoration margin. into the surrounding tissues. • The rate (speed) of ablation of dental hard tissue is a consequence of the amount of incident laser energy delivered to the tissue as well as the effects of wavelength, pulse LASER ENERGY AND DENTAL duration, pulse shape, repetition rate, power density, the HARD TISSUES thermal relaxation time of the tissue, and delivery mode. Healthy oral hard tissues include enamel, primary and secondary • Fluoridation of the tissue, incident angle of the delivery tip dentin, cementum and alveolar bone. For the purposes of the relative to the tooth, and presence of ablation products will application of laser energy in restorative dental procedures, affect the speed of ablation. demineralized and carious hard tissue must also be considered. • The ablation threshold of human enamel has been In addition to the prime interaction of laser energy with these reported to be in the range of 12-20 Joules/cm2, and for tissues, there also exists a need to establish a rate of interaction that dentin 8-14 Joules/cm2 for the Er:YAG and Er,Cr:YSGG laser is commensurate with a time frame that allows such interaction wavelengths, respectively. to be clinically acceptable, by limiting the time for conduction of • Ablation of bone. The development of Er:YAG and Er,Cr:YSGG excess energy to occur, while at the same time being fast enough lasers has enabled bone ablation to be carried out with to be clinically acceptable. minimal adjacent damage, and the use of erbium lasers in Early investigations into the use of lasers for the ablation or dento-alveolar surgery represents a less-traumatic experience modification of dental hard tissue were carried out using a ruby for the patient. laser (red, visible, 694.3 nm), a carbon dioxide continuous-wave • As with tooth tissue ablation, bone tissue cutting is a laser (infrared, 10.6 µm), and subsequently the neodymium:YAG thermally induced explosive process and it is essential to laser (infrared, 1064 nm). maintain a coaxial water spray to prevent heat damage, which delays healing. • Bone composition is very similar to dentin from the perspective of laser-tissue interactions. In maxillary alveolar bone, the speed of laser cutting is comparable with that of a bur, and slightly slower in the mandible. • Future developments and applications. Several exciting new possibilities for the use of lasers on hard tissues are likely to become available to the practicing dentist in the near future. Two such examples are: • Selective ablation of calculus by wavelengths in the ultraviolet/blue region will offer less invasive dentistry. • Low microsecond-pulsed carbon dioxide lasers with a 9.3- or 9.6-µm wavelength have great potential for efficient and effective ablation of sound and pathological hard tissues, as well as modification of the mineral to increase resistance to caries attack. Journal of Laser Dentistry | 2012 Vol. 20,No. 2 Parker et al. 47 48 P

Journal of Laser Dentistry | 2012 Vol. 20, No. 2 O SITI to investigate its utility for hard tissue for use. utility to investigate its were done USA in the investigations numerous and dentistry laser because of its very low absorption in sound enamel or dentin. or enamel in sound absorption low very its of because dentist, restorative the to marginal benefit only of toshown be was this of wavelength significance clinical the usage, effective and safe some to establish were published studies While pulp. dental vital the on effects possible the and wavelength, this laser of effect tissue, antibacterial the diseased (pigmented) of ablation the structure. bone and tooth within heat buildup damaging and cracking charring, of reports with interactions, nm), gave this laser poor but (10,600 dioxide carbon wavelength, laser available commonly Nd:YAG dentin. and in enamel of absorption low to very due the enamel, dental of resistance acid the increase effectively to wavelength this for first applied be must material (e.g., ink) black is realized that absorbing an commonly not reconstitution of melted mineral in enamel. mineral melted of reconstitution Nd:YAG to low-power exposure following resulting the and energy enamel in acid-resistance beneficial the of reports published expected to become a clinical reality in the near future. future. near in the reality aclinical to become expected wavelength. The successful use of pulsed CO pulsed of use successful The wavelength. of composite mineral structures. mineral composite of melting and cracking as such effects, side unwanted heating cause Nd:YAG drew conclusions that the studies several could wavelength Furthermore, to surface. the is applied apigment or is pigmented ablated be to region the unless ablation for needed are fluences appeared to offer safe use in cavity preparation. cavity in safe use to offer appeared and hard tissue elements bytarget are well absorbed wavelengths erbium:YAG nm) chromium:YSGG (2940 erbium, and (2780 nm) laser The were levels used. energy right the if injury collateral thermal or pulpal cause ratesnot that did ablation significant clinically offered and tissue to elements, target were complementary that wavelengths laser in addressing arealwas achievement mid-1990s. the nm) during (around lasers 3,000 This wavelength mid-infrared free-running, of marketing and development the to Thisled hard tissues. dental of ablation effective for Er:YAG the potential of the illustrated wavelength) (2.94-µm wave CO wave continuous- The to needs. the tailored better be can pulses the of density energy the and pulses, tissue to between the cool for time is there where mode pulsed than rather mode continuous-wave the with deposited rapidly heat was Excess water component. in the and mineral the in both this wavelength of absorption hard to combined tissue due in the the deposition energy high water, cooling no continuous in very resulted wave with which Parker etal. O The Nd:YAG laser was the first to be marketed for soft tissue Nd:YAG The soft for marketed be to first the was laser Other early studies on enamel ablation used the other other the used ablation enamel on studies early Other The work of workers such as Keller and Hibst, and suchasKeller workers of work The N PAPERN 2 13-14 13-14 laser use resulted in reports of poor clinical benefit of thisof benefit clinical poor of in resulted reports use laser The available carbon dioxide lasers at that time were at that time lasers dioxide carbon available The 1-9 1-9 Conversely, some workers 1-9 1-9 10-12 10-12 Investigations included included Investigations 2 lasers for ablation is ablation for lasers 15-17 15-17 However, is what 29 29 among others, others, among 9 High High the use of these laser wavelengths. laser these of use the misdirects and wavelengths at these to application due laser occurs ablation how of mechanism the misleads usit in understanding but is this incorrect, only Not wavelengths. these absorbs strongly mineral that dental statements erroneous the have perpetuated hardon tissues effects laser about many publications Unfortunately lower “speed” of cutting, when compared to drill. the compared when cutting, of “speed” lower the to be appear would drawback tissue.only dental the Generally, on used when wavelengths laser mid-infrared of selectivity and rise, thermal low to precision, the attesting papers of number the significant in determining effective treatment outcomes: treatment effective determining in significant be will factors following the setting clinical agiven within and years, 10 past the during progressed has procedures dental restorative of the tissues, the of mineral hydroxyapatite (carbonated) the of group hydroxyl the during preparation. cavity tissue surrounding healthy of removal unnecessary and cracking, rise, tissue temperature pulpal and to rise surface gives drilling that high-speed have shown studies several when even plausible, accepted as are often speed and use of “gold Ease standard.” the as is drill seen rotary high-speed the dentistry, in restorative a laser to may any wish but to clinician who use incongruous, mayIt seem ascending water composition. ascending and tissue have, density carious relatively,and mineral descending below, Figure 1). (see and surface cementum bone, dentin, Enamel, the water below the of superheating in water and this absorption to due is is that it primarily wavelengths bythese tissue ablation hard key to understanding The mineral. lost water the that replaces of quantity is tissue higher even an there In carious pore. available into tissue, the deep every filling bone and cementum, dentin, in enamel, crystals the among is present water thatThis is naturally nm. 3,000 around water band to broad due arelatively wavelengths two these for absorption in waterprimary is the absorption The Nd:YAG the with greater that seen than magnitude wavelength. of orders Er,Cr:YSGG. isin water the several than absorption This water, Er:YAG the absorbed with strongly more somewhat being Er,Cr:YSGGBoth Er:YAG and well in are absorbed wavelengths laser a) Target chromophores MID-INFRARED LASERS MID-INFRARED ABLATI • Power values. • Power values. “cutting” of • Speed restoration and design to cavity action laser of • Relationship effects thermal • General continuous wave, or chopped) (pulsed • Pulse duration • Emission mode interaction of • Mechanism • Target chromophores Notwithstanding, the use of Er:YAG of use the Er,Cr:YSGGNotwithstanding, and in lasers In addition, there is a small absorption at around 2,800 nmby 2,800 at around is asmall there absorption In addition, 9, 51 retention O 28-32 28-32 N O but this is far outweighed by the water effects. water effects. bythe outweighed this is far but F HARD DENTALF HARD TISS 18-21 18-21 26-27 26-27 Such incongruity is compounded by is compounded incongruity Such

22-25 22-25 U ES BYES

POSITION PAPER

Figure 1. Schematic absorption curve of dental enamel (carbonated hydroxyapatite (HA) plus water) and emission wavelengths of the Er,Cr:YSGG, Er:YAG, and CO2 lasers. Carbonated HA exhibits a small peak at approximately 7,000 nm, coincident 2- with carbonate (CO3) ion absorption. The solid line presents the absorption bands for dental enamel with the tissue components labeled. The dashed line represents the absorption bands for water. The major broad enamel absorption band that spans the 3.0-µm (3,000-nm) region is due to the water content of the tissue, not the hydroxyapatite mineral. (Reprinted with permission from Parker SPA. The use of lasers in bone surgery. J Laser Dent 2007;15(1):9-13). © 2007 Academy of Laser Dentistry. All rights reserved. Unauthorized use prohibited.

b) Mechanism of interaction d) General thermal effects When incident laser energy directed onto hard dental tissue is The vital dental pulp is acutely sensitive to thermal change. Studies absorbed by the prime chromophores, either water or carbonated have established that rotary instrumentation can cause conductive hydroxyapatite, one of two effects occur. For both Er:YAG and thermal rise in excess of 20ºC above 37.4ºC.40-41 With regard to laser Er,Cr:YSGG wavelengths this energy is absorbed primarily by irradiation of dental tissue, the explosive defragmentation resulting the water and is rapidly converted to heat, which causes super- from water-assisted mid-infrared laser wavelengths allows much of heating and a phase transfer in the subsurface water, resulting in a the heat to escape from the cavity carried in the ablated particles, disruptive expansion in the tissue. Through this mechanism, whole resulting in pulpal thermal rises of less than 5ºC.42-44 The affinity tissue fragments are ejected and a hole is cut in the tooth, with little of mid-infrared laser wavelengths with water allows the main or no alteration to the mineral itself. absorption to take place in demineralized tissue richer in organic If laser light is effectively absorbed by the mineral, the crystals material and with a higher percentage of water, thus protecting the themselves may be heated above their melting point and some sound underlying tissue with a reduced penetration of the beam. disruption of the crystal structure occurs with subsequent re- Contrary to this, the accumulation of ablation debris within a deep solidification in a different form, or direct ablation of the mineral, cavity can lead to “super-heating” which can lead to conductive 45-46 but there is also conductive heat transfer to interstitial free heat damage. water.33-37 Relatively high fluences are needed at these wavelengths for this to occur. c) Emission mode and pulse duration The emission mode of currently marketed mid-infrared wavelength lasers is defined as free-running pulsed. Currently commercially available lasers emit a pulse train of 50-250 microsecond pulses on average which, when delivered in rates of 3-50 Hz (pulses per second) values, represent duty cycle values of approximately 80%. While pulse durations are close to the thermal relaxation times of enamel and dentin, it is evident that there exists a need to examine further ultrashort pulse durations – and associated high peak power values – in an attempt to create sufficient ablative force without inducing collateral thermal damage.38-39 Journal of Laser Dentistry | 2012 Vol. 20, No. 2

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Journal of Laser Dentistry | 2012 Vol. 20, No. 2 O SITI Parker etal. O to the pulp. to pulp. the damage irreversible possible the and required, be that would input total large energy very the required, to time due the deprecated, is to be restorations indirect full-coverage of preparation in the alone Conversely, lasers of use may bring. the techniques laser that benefits is materials, acceptance there the of indirect or direct using either veneers, single-surface of to preparation the regard With crowns. full-veneer of provision in the current lasers “pure” dentistry. laser of ideology the above care patient places consideration Such margin. post-restoration astable provide or preparation cavity bur, expedite to in order either arotary with enamel unsupported and to overhanging remove grossly need may well remain the spray. water acoaxial of bymeans removal their or products, ablation of buildup the and power incident much of too effects at the looked therefore,have Studies, is avoided. heat to rise be damaging of possibility the if front, thermal the precede always should front ablation that the is It important front. athermal and front ablation –an interaction of wave fronts two of existence the concept of char. or ablation, of products to pulp) to also of the accumulation and prevent the conduction heat tissue (and in the undesirable heat buildup of possibility the tissue, mode. emission and the of time relaxation thermal density, rate, the power repetition pulse shape, pulse duration, wavelength, of effects well asthe to tissue as the delivered energy laser incident of amount the of hard tissue is dental aconsequence of ablation of rate (speed) The parameters tolaser related as “cutting” of Speed f) to overcome potential such problems. techniques acid-etch and laser-irradiation of approach combined a have Studies proposed margins. post-restoration the of stability relative enamel, the to of laser-irradiated fragility the identified has Asuccession resin. studies composite retention of of ideal to that may predispose surface “super-rough,” micro-cavitated byEr:YAG dentin and enamel of Er,Cr:YSGG or in a results lasers irradiation Laser etch resin composite retention restoratives. of acid- of development the with toward intervention minimal amove represents “G.V. classical the model, with variance Black” at design, cavity restorative conservative of emergence The retention restoration and design tocavity action laser of e) Relationship minimized. is transfer heat and efficient, is more rise, ablation values power peak duration, pulse the that byreducing shown been has It energy. laser the of pulse duration the of reducing effect the to determine out carried have been heat conversion, studies and levels power such with Coexistent enamel. of threshold ablation relative to the Hibst, and byKeller that postulated in excessof far delivery to power led has instruments rotary of those with Furthermore, mention should be made as to the suitability of of asto suitability the made be should mention Furthermore, Mid-infrared ablation of dental hard tissue has given rise to hard rise the tissue given has dental of ablation Mid-infrared N PAPERN 55 55 It is also evident that the desire to match cutting speeds speeds to desire that match the isIt evident also cutting 56-59 56-59 53-54 In addition, it is necessary to avoid is it necessary In addition, 47-52 47-52 Irrespective, there there Irrespective, reported to be in the range of 12-20 of range in the to be reported J/cm been has enamel human of threshold ablation anecdote. The the of danger the least not factors, bymany conflicting compromised hard tissue is dental of laser-assisted for ablation value power frame. time acceptable an within used to be lasers allow can gross caries in removing curettes sharp of use the In addition, drill. aslow-speed against matched when indentin, speed comparable and in enamel, slower 80% claims of to rise given has instrument, rotary to ahigh-speed compared structure. to in order prisms access inter-prismatic, the higher-water content enamel the of to axis the parallel tip delivery the addressing of effectiveness the have shown reports Several ablation. of speed the all affect will products ablation of presence and tooth, relative to tip the delivery the of tissue, angle the incident of occur within differing delivery systems. systems. delivery differing within occur air, of water,parameters that may losses size, any spot and power operating differing the protocols laser, agiven in mind for bearing treatment laser in establishing guidelines manufacturer’s the clinician to the follow for prudent seem would It reports. anecdotal of aplethora to be seem does there necessary, power of levels minimal that have determined studies those from Apart damage. adjacent tissue causing rates without ablation acceptable clinically energy, time, laser minimal a within achieve sufficient to of 150-250 delivery is concern the mJ/pulse. paramount is of What this may to equate mode, emission approximately pulsed running afree- of use size, the spot with delivery laser average an For induced explosive process process explosive induced bur. surgical slow-speed the of to intense the vibration compared when patient the for experience traumatic aless represents surgery in dentoalveolar lasers erbium of use the and damage, adjacent minimal with out carried to be ablation bone enabled Er:YAG of development The Er,Cr:YSGG and has wavelengths apicoectomy. and lengthening, crown clinical pockets, infrabony and surgery periodontal extraction, surgical include bone of ablation or cutting that may involve the procedures Clinical g) Bone ablation cm good ablation rates. rates. ablation good 3.5-7.0range to effect appear water spray maximal with Watts) 10-20 mJ, 350-500 of parameters (averagespatter. Hz Laser power blood minimize and debris of effect “stall-out” to the reduce avoided be parameters that power excessive important considered It is bone. of cortical density greater the mineral reflecting mandible, in the slower slightly and abur that of with comparable protein content is similar, water asiscontent. the is similar, mineral The the laser-tissue of interactions. perspective the similar to from dentin is very composition Bone healing. delay would to which water spray prevent heat damage coaxial 2 The debate over what constitutes a “recommended” a“recommended” overconstitutes what debate The alaser, with tissue when rate ablation of the Generally, suchasfluoridation factors other to above, the In addition As with tooth tissue ablation, tissue cutting is a thermally is athermally tissue cutting tissue tooth ablation, with As In maxillary alveolar bone, the speed of laser cutting is cutting laser of speed the bone, alveolar In maxillary for the Er:YAG the for Er,Cr:YSGG and respectively. wavelengths, laser 60-61 60-61 and it is essential to is it essential a maintain and 2 , and for dentin, 8-14 dentin, for , and J/ POSITION PAPER

Studies into the healing of laser-ablated bone support REFERENCES the contention that the reduction in effects such as physical trauma, tissue heating, and bacterial contamination may lead to 1. Bassi G, Chawla S, Patel M. The Nd:YAG laser in caries removal. Br Dent J 1994;177(7):248-250. uncomplicated healing processes, when compared to conventional use of a surgical bur.62-64 The microanalysis of the surface of bone 2. Harris DM, White JM, Goodis H, Arcoria CJ, Simon J, Carpenter that has been ablated using lasers shows little evidence of thermal WM, Fried D, Burkart J, Yessik M, Myers T. Selective ablation of damage, and any char layer appears to be restricted to a minimal surface enamel caries with a pulsed Nd:YAG dental laser. Lasers Surg Med 2002;30(5):342-350. zone of 20-30 µm in depth.65-66 3. Birardi V, Bossi L, Dinoi C. Use of the Nd:YAG laser in the treatment of Early Childhood Caries. Eur J Paediatr Dent FUTURE DEVELOPMENTS 2004;5(2):98-101. There are several exciting new possibilities for the use of lasers on 4. Cox CJ, Pearson GJ, Palmer G. Preliminary in vitro investigation hard tissues that are likely to become available to the practicing of the effects of pulsed Nd:YAG laser radiation on enamel and dentist in the near future. A couple of examples are presented dentine. Biomaterials 1994;15(14):1145-1151. here. In each area years of research have set the stage for the 5. Yamada MK, Watari F. Imaging and non-contact profile development of commercially viable lasers. analysis of Nd:YAG laser-irradiated teeth by scanning electron microscopy and confocal laser scanning microscopy. Dent Selective ablation of calculus by wavelengths in the ultraviolet/ Mater J 2003;22(4):556-568. blue region is one example.67-68 Ablation of carious enamel, dentin, and cementum, as well as bone may be more efficiently done with 6. Srimaneepong V, Palamara JE, Wilson PR. Pulpal space pressure and temperature changes from Nd:YAG laser irradiation of wavelengths not currently available commercially. The strongest dentin. J Dent 2002;30(7-8):291-296. absorption bands for the carbonated hydroxyapatite mineral of teeth and bone are in the 9.3 - 10.6-µm wavelength region, with 7. McDonald A, Claffey N, Pearson G, Blau W, Setchell D. The 9.6 µm being the strongest. Pulsed carbon dioxide lasers have effect of Nd:YAG pulse duration on dentine crater depth. J Dent 2001;29(1):43-53. great potential for ablation and modification of mineral to increase caries resistance. Recent studies have shown that by matching 8. Goodis HE, White JM, Marshall GW Jr, Yee K, Fuller N, Gee L, the pulse duration to the thermal relaxation time of the tissue and Marshall SJ. Effects of Nd: and Ho:yttrium-aluminium-garnet optimizing the fluence per pulse, very efficient ablation of enamel, lasers on human dentine fluid flow and dental pulp-chamber temperature in vitro. Arch Oral Biol 1997;42(12):845-854. dentin, and carious tissue can be achieved with little peripheral damage.69-70 Low microsecond pulse-duration lasers (e.g., 5-10 µs) 9. Seka W, Fried D, Featherstone JDB, Borzillary SF. Light of 9.3- or 9.6-µm wavelength have great potential. Furthermore deposition in dental hard tissue and simulated thermal laboratory studies have shown that similar irradiation conditions, response. J Dent Res 1995;74(4):1086-1092. but at lower fluences, can beneficially alter the mineral of enamel 10. Harazaki M, Hayakawa K, Fukui T, Isshiki Y, Powell LG. The to make it more resistant to acid and consequently to inhibit caries Nd-YAG laser is useful in prevention of dental caries during progression.31, 71-72 Clinical studies will be needed to confirm the orthodontic treatment. Bull Tokyo Dent Coll 2001;42(2):79-86. viability of this methodology in the mouth. It will be possible to 11. Hossain M, Nakamura Y, Kimura Y, Yamada Y, Kawanaka T, produce lasers that can ablate dental hard tissues and bone, while Matsumoto K. Effect of pulsed Nd:YAG laser irradiation on acid at the same time inhibiting subsequent caries progression, and demineralization of enamel and dentin. J Clin Laser Med Surg keeping peripheral damage to a minimum. 2001;19(2):105-108. 12. Kwon YH, Kwon OW, Kim HI, Kim KH. Nd:YAG and acid resistance of enamel. Dent Mater J 2003;22(3):404-411. SAFETY CONSIDERATIONS 13. Lan WH, Chen KW, Jeng JH, Lin CP, Lin SK. A comparison of the All laser-tissue interaction using surgical lasers carries general and morphological changes after Nd-YAG and CO2 laser irradiation specific safety concerns. With regard to the statutory instruments of dentin surfaces. J Endod 2000;26(8):450-453. ANSI 136.1 (2007) and IEC 60825-1/A2:2001, suitable precautions to 14. Yamada MK, Uo M, Ohkawa S, Akasaka T, Watari F. Three- protect intraoral nontarget tissue and patients’ and operator’s eyes dimensional topographic scanning electron microscope and 73-74 and skin should be employed. Raman spectroscopic analyses of the irradiation effect on teeth by Nd:YAG, Er:YAG, and CO2 lasers. J Biomed Mater Res B Appl Biomater 2004;71(1):7-15. 15. Pelagalli J, Gimbel CB, Hansen RT, Swett A, Winn DW 2nd. Investigational study of the use of Er:YAG laser versus for caries removal and cavity preparation – Phase I. J Clin Laser Med Surg 1997;15(3):109-115. Journal of Laser Dentistry | 2012 Vol. 20, No. 2

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