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General

Authors: Dr. Arjun Jawahar Sharma, Dr. Richa Kumari, Dr.Manesh Lahori

Introduction

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

An amazing paradigm-shiftis occurring in dentistry with a technology breakthrough that gives dentists the capability to perform a wide range of hard-and-soft tissue procedures with improved patient outcomes, less trauma, reduced post-op complications and in most cases, with no need for injections. This new technology greatly expands the scope of procedures a dentist can offer their patients.

1,2

Dentists are now successfully integrating the Er,Cr:YSGG laser technology (Waterlase® MD laser, BIOLASE Technology, Inc.) into their practices with the broadest indications for use of any other laser in medicine or dentistry. Lasers have been used in almost every other medical field, but they are typically a single-wavelength laser the clinician purchased for a specific application. For example, an opthalmologist must purchase an excimer laser for refractive surgery, argon for retinal surgery, and a Q-switch Nd:YAG for capsulotomies. A dermotologist may purchase a Q-switched Ruby for tattoo removal, diode for hair removal, and an Er:YAG for skin resurfacing. Even with the need for multiple lasers, medical professionals recognize the lasers still provide excellent return on investment and superior clinical results for new, unique procedures specific to lasers.10 With dentistry in the high tech era, we are fortunate to have many technological innovations to enhance treatment, including intraoral video cameras, CAD-CAM units, RVGs and air-abrasive units. However, no instrument is more representative of the term high-tech than, the laser. Dental procedures performed today with the laser are so effective that they should set a new standard of care.Fortunately, for dentists, a single laser wavelength as emerged that allows them to practice dentistry across all oral tissue. While lasers have been involved in dentistry for more than 20 years, until recently, no single laser had been cleared for and is capable for use on all oral tissues, including hard tissue, soft tissue, endo, perio, and bone. That all changed with the introduction of the YSGG laser.

10

 

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

A Brief History of Lasers
  • Approximately, the history of lasers begins similarly to much of modern physics, with Einstein. In 1917, his paper in PhysikialischeZeil, “ZurQuanternTheorie der Strahlung”, was the first discussion of stimulated emission.
  • In 1954 Townes and Gordon built the first microwave laser or better known as ‘MASER’ which is the acronym for ‘Microwave Amplification by stimulated Emission of Radiation’
  • In 1958, Townes, working with Schawlow at Bell Laboratories, published the first theoretic calculations for a visible light maser – or what was then called a LASER.
  • In May 1960, Theodore Maimen at Hughes Aircraft company made the first laser. He used a ruby as the laser medium.
  • One of the first reports of laser light interacting with tissue was from Zaret; he measured the damage caused by lasers incident upon rabbit retina and iris.
  • The first gas laser was developed by Javan et al in 1961. This was the first continuous laser and used helium – neon.
  • The Nobel Prize for the development of the laser was awarded to Townes, Basor and Prokhovov in 1964.
  • The neodymium – doped (Nd): glass laser was developed in 1961 by Snitzer.
  • In 1964 Nd: YAG was developed by Geusic.
  • The CO2 laser was invented by Patel et al in 1965.
  • In 1968 Polanyi developed articulating arms to deliver CO2 laser to remote areas.
  • Polanyi in 1970 applied CO2 laser clinically.
  • In 1990 Ball suggested opthalmologic application of ruby laser.
Terminology and Concepts in Laser Dentistry

Before exploring the evolution of dental lasers, it is important to understand several terms and concepts when discussing laser dentistry. Lasers are usually named for the “active medium” that is charged with energy inside the laser unit to create laser light. For example, the YSGG laser receives its name from the elements that compose the crystal medium inside the laser system – yttrium, scandium, gallium and garnet, doped with erbium and chromium (Er,Cr:YSGG). When the crystal is pumped with energy, a specific, monochromatic wavelength of light is emitted from the crystal and transferred to the target tissue through a delivery system. In the case of the YSGG laser, the wavelength delivered from the laser through a fiber optic cable is 2,780 nanometers. Other lasers, such as the Nd:YAG lasers operate at 1,064 nanometers, CO2 lasers at 10,600 nanometers, Erbium:YAG at 2,940 nanometers, and so on (Fig. 2 – Electromagnetic Spectrum). Another key concept is that different laser wavelengths react with tissue in different ways. Depending on their “absorptioncoefficient,” laser light has properties that cause it to interact and absorb differently with target tissue. For example, the laser light from a diode laser is most effectively absorbed in pigmented tissues and melanin, which makes it an ideal tool for use in cutting and coagulating soft tissue. The YSGG laser is well absorbed in water and hydroxyapatite (Fig. 3 - Absorption Coefficient Table), which makes it an excellent tool for cutting enamel, dentin, bone, and soft tissue.10

 
Fig. 1.Electromagnetic Spectrum.Fig. 2.Absorption Coefficient Table.

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 it. The radiation emitted by lasers including both visible and invisible light is more generally termed as electromagnetic radiation. The concept of stimulated emission of light was first proposed in 1917 by Albert Einstein.

He described three processes:
  • Absorption
  • Spontaneous emission
  • Stimulated emission.

If a collection of atoms includes, more that are pumped into the excited state that remain in the resting state, a population inversion exists. This is necessary condition for lasing. Now, the spontaneous emission of a photon by one atom will stimulate the release of a second photon in a second atom, and these two photon will trigger the release of two more photons. These four than yield eight, eight yield sixteen and so on. In a small space at the speed of light, this photon chain reaction produces a brief intense flash of monochromatic and coherent light which is termed as ‘laser’.3,4

Laser Design

The laser consist of following components.

  1. A laser medium or active medium: This can be a solid, liquid or gas. This lasing medium determines the wavelength of the light emitted from the laser and the laser is named after the medium.
  2. Housing tube or optical cavity:
    • Made up of metal, ceramic or both.
    • This structure encapsulates the laser medium.
    • Consists of two mirrors, one fully reflective and the other partially transmittive, which are located at either end of the optical cavity.
  3. Some form of an external power source: This external power source excites or “pumps” the atom in the laser medium to their higher energy levels. A population inversion happens when there are more atoms in the excited state rather than a non-excited state. Atoms in the excited state spontaneously emit photons of light which bounce back and forth between the two mirrors in the laser tube, they strike other atoms, stimulating more spontaneous emission. Photons of energy of the same wavelength and frequency escape through the transmittive mirror as the laser beam. An extremely small intense beam of energy that has the ability to vaporize, coagulate, and cut can be obtained if a lens is placed in front of the beam. This lens concentrates the emitted energy and allows for focussing to a small spot size.5,6
Focussing

Lasers can be used in either a focussed mode or in a defocused mode. A focussed mode is when the laser beam hits the tissue at its focal points or smallest diameter. This diameter is dependent on the size of lens used. This mode can also be referred as cut mode. Eg.While performing biopsies. The other method is the defocused mode. By defocusing the laser beam or moving the focal spot away from the tissue plane, this beam size that hits the tissue has a greater diameter, thus causing a wider area of tissue to be vaporized. However, laser intensity / power density is reduced. This method is also known as ablation mode. Eg.In Frenectomies.In removal of inflammatory papillary hyperplasias.

Contact and Non contact modes

In contact mode, the fiber tip is placed in contact with the tissue. The charred tissue formed on the fiber tip or on the tissue outline increases the absorption of laser energy and resultant tissue effects. Char can be eliminated with a water spray and then slightly more energy will be required to provide time efficient results. Advantage is that there is control feed back for the operator. Non contact mode: Fiber tip is placed away from the target tissue. The clinician operates with visual control with the aid of an aiming beam or by observing the tissue effect being created.5,7,8

So generally laser can be classified as Laser Types:
  1. I. Based on wavelength. Soft lasers and and Hard lasers
  2. II. Based on the type of active / lasing medium used ArFexcimer, KrFexcimer,XeClexcimer,Argon ion ,KTP, Ruby ,Nd: YAG, HO: YAG,YSGG,Er: YAG,CO2.
The Dental Laser Revolution Begins

1. Soft Lasers: With a wave length around 632mm Soft lasers are lower power lasers. Eg: He Ne, Gallium arsenide laser. These are employed to relieve pain and promote healing eg. In Apthous ulcers.

2. Hard lasers: Lasers with well known laser systems for possible surgical application are called as hard lasers. Eg: CO2, Nd: YAG, Argon, Er:YAG etc.

CO2 Lasers

The CO2 laser first developed by Palet et al in 1964 is a gas laser and has a wavelength of 10,600 nanometers deep in the infrared range of the electromagnetic spectrum. CO2 lasers have an affinity for wet tissues regardless of tissue color.The laser energy weakens rapidly in most tissues because it is absorbed by water. Because of the water absorption, the CO2 laser generates a lot of heat, which readily carbonizes tissues. Since this carbonized or charred layer acts as a biological dressing, it should not be removed. They are highly absorbed in oral mucosa, which is more than 90% water, although their penetration depth is only about 0.2 to 0.1mm. There is no scattering, reflection, or transmission in oral mucosa. Hence, what you see is what you get. CO2 lasers reflect off mirrors, allowing access to difficult areas. Unfortunately, they also reflect off dental instruments, making accidental reflection to non-target tissue a concern. CO2 lasers cannot be delivered fiber optically Advances in articulated arms and hollow wave guide technologies, now provide easy access to all areas of the mouth.Regardless of the delivery method used, all CO2 lasers work in a non-contact mode. Of all the lasers for oral use, CO2 is the fastest in removing tissue.As CO2 lasers are invisible, an aiming helium – neon (He Ne) beam must be used in conjunction with this laser.

Nd: YAG Laser:

Here a crystal of Yttrium – aluminum – garnet is doped with neodymium. Nd: YAG laser, has wavelength of 1,064 nm (0.106 ) placing it in the near infrared range of the magnetic spectrum. It is not well absorbed by water but are attracted to pigmented tissue. Eg: hemoglobin and melanin. Therefore various degrees of optical scattering and penetration to the tissue, minimal absorption and no reflection.Nd: YAG lasers work either by a contact or non-contact mode. When working on tissue, however, the contact mode in highly recommended.TheNd: YAG wavelength is delivered fiber optically and many sizes of contact fibers are available. Carbonized tissue remains often build of on the tip of the contact fiber, creating a ‘hot tip’. This increased temperature enhances the effect of the Nd:YAG laser, and it is not necessary to rinse the build up away. Special tips, the coated sapphire tip, can be used to limit lateral thermal damage. A helium-neon-aiming beam is generally used with Nd: YAG wavelength.Penetration depth is ~ 2 to 4m, and can be varied by upto 0.5-4mm in oral tissues by various method. Most dental Nd: YAG lasers work in a pulsed mode. At higher powers and pulsing, a super heated gas called a plasma can form on the tissue surface. It is the plasma that can be responsible for the effects of either coagulation, vaporization or cutting. If not cooled (e.g. by running a water stream down the fiber) the plasma can cause damage to the surrounding tissues. The Nd:YAG beam is readily absorbed by amalgam, titanium and non-precious metals, requiring careful operation in the presence of these dental materials.

Argon Lasers

Argon lasers are those lasers in the blue-green visible spectrum.They operate at 488nm or 514.5nm, are gas like CO2 lasers and are easily delivered fiber optically like Nd:YAG. Argon lasers have an affinity for darker colored tissues and also a high affinity for hemoglobin, making them excellent coagulators. It is not absorbed well by hard tissue, and no particular care is needed to protect the teeth during surgery.In oral tissues there is no reflection, some absorption and some scattering and transmission.Argon lasers work both in the contact and non contactmodeLike, Nd: YAG lasers, at low powers argon lasers suffer from ‘dragability’ and need sweeping motion to avoid tissue from accumulating on the tip.Enhances are not needed with Argon lasers.Argon lasers also have the ability to cure composite resin, a feature shared by none of the other lasers.The blue wavelength of 488 nm is used mainly for composite curing, while the green wavelength of 510nm is mainly for soft tissue procedures and coagulation.

Ho: YAG laser [Holmium YAG lasers]

• Has a wavelength of 2,100 nm and is a crystalDelivered through a fiber optic carrier.A He-Ne laser is used as an aiming lightDragability is less compared to Nd: YAG and argon lasersLike Nd: YAG, can be used in both the contact and non-contact modes and are pulsed lasers.Ho: YAG laser has an affinity for white tissue and has ability to pass through water and acts as a good coagulator.

Evolving Technology

Following American Dental Laser, a number of other companies, including Luxar, HGM, Excel and BIOLASE offered Nd:YAG, CO2, and argon lasers for usein soft tissue. In 1988 in Europe and 1989 in the United States, BIOLASE filed patents for the novel use of lasers with water in dentistry. The company began development of a laser device exclusively for this purpose. In May 1997, Premier Laser obtained the first marketing clearance from the U.S. FDA to cut enamel and dentin in adults using an Er:YAG laser, a device readily available in dermatology and plastic surgery. Later, other companies, including OpusDent, Hoya ConBio, Kavo, Deka and Fotona adapted the Er:YAG technology as well, making additional strides for laser use in dentistry. In 1998, after more than ten years of research and investigation, BIOLASE obtained a marketing clearance for cutting hard tissue in adults using an all-new laser designed by the company exclusively for use in dentistry. This dentistry-only laser, known as the YSGG laser, was called the “Millennium” and it used a patented combination of YSGG laser energy, water and air to safely and effectively ablate enamel and dentin in adults. The YSGG laser was then cleared for use on patients of all ages, and the company began selling the laser worldwide. Researchers began working on soft tissue with the YSGG laser. With the water spray minimized or turned off, the laser could effectively cut and coagulate soft tissue with more control, and in many cases, much faster. By 2000, greatly expanded FDA clearances for soft tissue indications had been obtained by BIOLASE, and clinicians were able to work on all oral tissues. BIOLASE released a second YSGG laser, the “Waterlase,” in 2000, and theWaterlase MD in 2004 (Fig. 4), which included many new features never before used in laser dentistry. The company also obtained a series of ground-breaking clearances from the FDA for complete laser endodontics (2002), apicoectomy (2002), cutting and shaving oral osseous tissues (2003), as well as the most complete list of procedures related to periodontal therapy, including laser curettage and osseous crown lengthening (2004). Other laser companies have managed to obtain a few of these same clearances later. Research continues for future indications with an all-tissue laser, including crown and veneer preparations, orthodontic applications, advanced new implant therapies including sinus augmentation and bone grafting, gingival tissue resurfacing, and even low-level laser therapy applications using the YSGG laser.10

Clinical Applications and Descriptions

1. Cutting Hard Tissue(Enamel and Dentin) The YSGG laser was cleared for Class I, II, III, IV, and V cavity preps, asthe laser reacts at a cellular level and helps to prohibit the pain response (Tuner and Hodes, 2002), most hard tissue procedures can be completed without the aid of injected anesthetic. The YSGG laser also allows the precise treatment of pits and fissures on the occlusal surfaces of molars, which has aided in the growing discipline of “micro” and “minimally invasive” dentistry.

Fig.3 The high-speed drill leaves a smear layer of debris on the surface of the treated tooth. Fig.4 After treatment with the YSGG laser, there is no smear layer and the dentinal tubules are open, which improves bonding.
 

2. Root Canal With hard tissue and soft tissue procedures cleared by the FDA, research and development turned to other disciplines where lasers had already showed some potential for disinfection, sterilization, and other benefits. The YSGG laser was the first laser cleared for root canal, including tooth preparation to obtain access to the canal, root preparation, and canal enlargement and cleaning. The same benefits that are evident when cutting enamel and dentin were also available when the YSGG laser was used in the canal. The smear layer was eliminated and debris were dramatically reduced, and the dentinal tubules remained free and clear, which may aid in improved obturation and sealing of the canal.

Fig.5 The coronal third of a root canal after treatment with the Profile rotary system. (5000x mag) Fig. 6 The coronal third of a root canal after treatment with manual K files (5000x mag).

3. Soft Tissue Soon after obtaining the first hard-tissue clearances for the YSGG laser, BIOLASE obtained a collection of clearances related to soft tissue (July 2001), including sulcular debridement. The YSGG laser demonstrated the capability to atraumatically treat soft tissue with little to no bleeding, little edema, and positive post-operative results. The YSGG laser was the first hard-tissue laser cleared for soft tissue indications such as treatment of aphthous ulcers, herpetic lesions, and leukoplakia. In addition, the laser was cleared for oral surgical applications such as frenectomy, gingivectomy , fibroma removal, and bloodless troughing around a prep prior to taking an impression.

4. Bone Surgery and Osseous Crown Lengthening The YSGG laser was also the first cleared for bone, including cutting, shaving, contouring and resecting oral osseous tissues. The laser was later cleared for osteoplasty, ostectomy, and osseous recontouring to correct defects and create physiologic osseous contours necessary for ideal clinical results. In 2003, the YSGG laser was the first laser device cleared for osseous crown lengthening to achieve biologic width, which can be completed without laying a flap, suturing, or damage to the bone (Wang, 2002). The ease of use of the YSGG system provides the dentist with a strong ROI by performing most of their own osseous crown lengthening procedures, which is important in an era fueled by prime time “extreme” dental makeovers, and growing demand for aesthetic dentistry.

5. Apicoectomy& Endodontic Surgery Other advanced endodontic applications include the YSGG’s ground-breaking clearance for apicoectomy (2003), which, for the first time, allowed a clinician to use a single instrument for all major steps of an apicoectomy procedure, including flap preparation, cutting bone, amputating the root tip, removing pathological tissue and hyperplastic tissue from around the site, and preparing the site for retrofill amalgam or composite.

6. Periodontal Procedures The YSGG laser is the first and only laser cleared for the major indications in laser periodontal therapy. While other lasers such as the diode laser and Nd:YAG laser are cleared for soft tissue applications related to perio, none have been cleared for cutting oral osseous tissues, a core component of any periodontal program. The YSGG laser was recently cleared by the FDA for a wide array of indications related to periodontal health, including laser curettage, sulcular debridement, ostectomy, osteotomy, soft tissue flap elevation, removal of pathological tissues from bony sockets, and many other important clinical applications.8,9,10

Fig. 7 The coronal third of a canal treated with the YSGG laser. Note the absence of smear layer in the canal (5000x mag).

FDA-CLEARED INDICATIONS FOR USE FOR LASERS.

Hard Tissue:

  • Class I, II, III, IV and V cavity preparation
  • Caries removal
  • Hard tissue surface roughening and etching
  • Enameloplasty, excavation of pits and fissures for placement of sealants

 

Root Canal

  • Tooth preparation to obtain access to a root canal
  • Root canal preparation including enlargement
  • Root canal debridement and cleaning
  • Pulpotomy as an adjunct to root canal therapy

 

Endo Surgery

  • Flap preparation – incision of soft tissue to prepare a flap and expose the bone
  • Cutting bone to prepare a window access to the apex (apices) of the root(s)
  • Apicoectomy – amputation of the root end
  • Root end preparation for retrofill amalgam or composite
  • Removal of pathological tissues (i.e., cysts, neoplasm or abscess) and hyperplastic tissues (i.e., granulation tissue) from around the apex. ( Any tissue growth (i.e., cyst, neoplasm or other lesions) must be submitted to a qualified laboratory for histopathological evaluation)

 

Bone

  • Cutting, shaving, contouring and resection of oral osseous tissues
  • Osteoplasty and osseous recontouring (removal of bone to correct osseous defects and create physiologic osseous contours)
  • Ostectomy (resection of bone to restore bony architecture, resection of bone for grafting, etc.)
  • Osseous crown lengthening

 

Soft Tissue

  • Incision, excision, vaporization, ablation and coagulation of oral soft tissues, including: excisional and incisional biopsies
  • Exposure of unerupted teeth
  • Fibroma removal
  • Flap preparation – incision of soft tissue to prepare a flap and expose the bone
  • Frenectomy and frenotomy
  • Gingival troughing for crown impressions
  • Gingival troughing for crown impressions
  • Gingivectomy or gingivoplasty
  • Gingival incision and excision
  • Hemostasis
  • Implant recovery
  • Incision and drainage of abscesses
  • Leukoplakia
  • Operculectomy
  • Oral papillectomies
  • Pulpotomy
  • Pulp extirpation
  • Reduction of gingival hypertrophy
  • Soft tissue crown lengthening
  • Treatment of canker sores, herpetic and aphthous ulcers of the oral mucosa
  • Vestibuloplasty

 

Perio

  • Sulcular debridement (removal of diseased or inflamed soft tissue in the periodontal pocket to improve clinical indices including gingival index, gingival bleeding index, probe depth, attachment loss and tooth mobility)
  • Flap preparation -- incision of soft tissue to prepare a flap and expose unerupted teeth (hard and soft tissue impactions)
  • Full thickness flap
  • Partial thickness flap
  • Split thickness flap
  • Removal of granulation tissue from bony defects
  • Laser soft tissue curettage of the post-extraction tooth sockets and theperiapical area during apical surgery

 

Laser Hazards and Laser Safety:

The subject of dental laser safety is broad in scope, including not only an awareness of the potential risks and hazards related to how lasers are used, but also a recognition of existing standards of care and a thorough understanding of safety control measures. The types of hazards can be grouped as Ocular injury ,Tissuedamage,Respiratoryhazards,Fire and explosion, Electrical shock.

Summary

The benefits of a versatile instrument laser are clearly evident.The dramatic reduction of pain in most cases reduces the need for injected anesthesia and frees up chair time for a busy practice and can generate increased word-of-mouth referrals among your patients.According to various reports, 100 million patients fear a visit to the dentist because of fear of the drill and the needle. The ADA recently reported that at least 82% of patients think it “somewhat important, important, or very important,” that adental office have a dental laser, which allows a practice to offer a different type of dentistry. The laser dramatically reduces the need to apply a high-speed drill to the tooth surface for any reason; however, it has yet to completely replace the drill because a laser cannot effectively cut reflective surfaces such as metal and porcelain. Still, the fact that a single instrument can remove bulk amounts of enamel, dentin and decay, then cut soft tissue around the site, return to removing enamel, and then etch the surface in the time it typically takes for anesthetic to take effect – it hearkens to an exciting new era of efficient, minimally invasive laser dentistry.

References
  1. Aykol, G., Baser, U., Maden, L., Kazak, Z., Onan, U., Tanrikulu-Kucuk, S., ...Yalcin, F. (2011, March 2011). The Effect of Low-Level Laser Therapy as an Adjunct to Non-Surgical Periodontal Treatment. Journal of Periodontology, 82, 481-488.
  2. Blayden, J., & Mott, A. (2013). Soft-Tissue Lasers in Dental Hygiene. Ames, Iowa: Wiley-Blackwell.
  3. Christodoulides, N., Nikolidakis, D., Chondros, P., Becker, J., Schwarz, F., Rossler, R., &Sculean, A. (2008, September 2008). Photodynamic Therapy as an Adjunct to Non-Surgical Periodontal Treatment: A Randomized Clinical Trial. Journal of Periodontology, 79, 1638-1644.
  4. Blayden, J., & Mott, A. (2013). Soft-Tissue Lasers in Dental Hygiene. Ames, Iowa: Wiley-Blackwell.
  5. Christodoulides, N., Nikolidakis, D., Chondros, P., Becker, J., Schwarz, F., Rossler, R., &Sculean, A. (2008, September 2008). Photodynamic Therapy as an Adjunct to Non-Surgical Periodontal Treatment: A Randomized Clinical Trial. Journal of Periodontology, 79, 1638-1644.
  6. Qadri, T., Poddani, P., Javed, F., Turner, J., &Gustafsson, A. (2010, August 2010). A Short-Term Evaluation of Nd:YAG Laser as an Adjunct to Scaling and Root Planing in the Treatment of Periodontal Inflammation. Journal of Periodontology, 81, 1161-1166.
  7. Ustun, K., Erciyas, K., Sezer, U., Gundogar, H., Ustun, O., &Oztuzcu, S. (2014). Clinical and Biochemical Effects of an 810 nm Diode Laseras an Adjunct to Periodontal Therapy: A Randomized Split-Mouth Clinical Trial. Photomedicine and Laser Surgery, 32, 61-66.
  8. Qadri, T., Poddani, P., Javed, F., Turner, J., &Gustafsson, A. (2010, August 2010). A Short-Term Evaluation of Nd:YAG Laser as an Adjunct to Scaling and Root Planing in the Treatment of Periodontal Inflammation. Journal of Periodontology, 81, 1161-1166. Retrieved from http://www.joponline.org/doi/pdf/10.1902/jop.2010.090700
  9. Ustun, K., Erciyas, K., Sezer, U., Gundogar, H., Ustun, O., &Oztuzcu, S. (2014). Clinical and Biochemical Effects of an 810 nm Diode Laseras an Adjunct to Periodontal Therapy: A Randomized Split-Mouth Clinical Trial. Photomedicine and Laser Surgery, 32, 61-66.
  10. James Jesse, Sandip Desai, The Evolution ofLasers in DentistryRuby to YSGG.ADA CERP. 1-12.