Lasers in periodontics

Abstract

Laser is one of the most captivating technologies in dental practice since Theodore Maiman in 1960 invented the ruby laser. Lasers in dentistry have revolutionized several areas of treatment in the last three and a half decades of the 20^th century. Introduced as an alternative to mechanical cutting device, laser has now become an instrument of choice in many dental applications. Evidence suggests its use in initial periodontal therapy, surgery, and more recently, its utility in salvaging implant opens up a wide range of applications. More research with better designs are a necessity before lasers can become a part of dental armamentarium. This paper gives an insight to laser in periodontics.

In the past 100 years, there has been extensive development of the mechanical cutting devices used in dentistry. However, while considerable progress has been made in this area of mechanical cutting, dental patients are still afraid of the noise and vibration produced by the mechanical action of the air turbine or ultrasonic scalers. From the end of the 20th century until now, there has been a continuous upsurge in the development of laser-based dental devices based on photomechanical interactions. Laser is the acronym of the words “Light Amplification by Stimulated Emission of Radiation.”[1] The pathogenesis of periodontal disease and the methods of treating it have undergone radical changes in the past 30 years. The current model for periodontal disease includes microbial components, host inflammatory responses, and host risk factors that contribute to the advancement of this disease. Soft tissue lasers are a good choice for bacterial reduction and coagulation in the treatment sequence. These properties of the soft tissue lasers make them an excellent choice to use in a periodontally involved sulcus that has dark inflamed tissue and pigmented bacteria.

Presently, various laser systems have been used in dentistry. This paper reviews on different lasers, their applications, and advantage in periodontics.

Historical Background

• 1917, Stimulated emission: Albert Einstein

• 1959, Principle of MASER: Schalow and Townes

• 1960, Synthetic ruby laser: Theodore Maimam[2]

• 1961, The first gas laser and first continuously operating laser: Javan et al.

• 1964, Treatment of caries: Goldman

• 1968, CO₂ laser: Patel et al.

• 1971, Tissue reactions to laser light and wound healing: Hall and Jako et al.

• 1974, Nd:YAG laser: Geusic et al.

• 1977, Ar laser: Kiefhaber

• 1988, Er:YAG laser: Hibst and Paghdiwala

• 1989, Nd:YAG laser, soft tissue surgery: Midda et al.

Theory

The light energy can induce energy transition in atoms, causing the atoms to move from their current state (EO) to the excited state / activated stage by the absorption of a quantum of energy.[3] This is called “stimulated absorption.” Because the lowest energy state is the most stable, the excited atom tends to return to normal by spontaneously emitting a quantum of energy called “spontaneous emission.” This conversion to low energy state can be achieved by stimulating the activated medium further by a quantum of light at the same transition frequency. This is called “stimulated emission.”[4] During this process, it releases a photon of the same size as of the released atom, which hits against the adjacent activated atom setting off a chain reaction of releasing photons.

Properties

Laser light is unique in that it is monochromatic (light of one specific wavelength), directional (low divergence), and coherent (all waves are in a certain phase relationship to each other). These highly directional and monochromatic laser lights can be delivered onto target tissue as a continuous wave, gated-pulse mode, or free running pulse mode.[5]

1. Continuous waves: The beam is emitted at one power level continuously as long as the foot switch is pressed.

2. Gated-pulse mode: The laser is in an on and off mode at periods. The duration of the on and off timer is in microseconds.

3. Free running pulse mode: Very large laser energy is emitted for an extremely short span in microseconds, followed by a relatively long time at which the laser is off.

Laser Device Components

All laser devices have the basic following components:[5]

1. A laser medium, which can be a solid, liquid, or gas.

2. An optical cavity or laser tube having two mirrors, one fully reflective and the other one partially transmissive, which are located at either end of the optical cavity.

3. An external mechanical, chemical, or optical power source which excites or “pumps” the atoms in the laser medium to higher energy levels [Figures 1 and 2].

Figure 1.

Laser device components

Figure 2.

Laser tissue interactions

Laser Delivery

The existing range of laser delivery systems includes the following:

1. Articulated arms (with mirrors at joints) – for UV, visible, and infrared lasers

2. Hollow waveguides (flexible tube with reflecting internal surfaces) – for middle and far infrared lasers

3. Fiber optics – for visible and near infrared lasers (5)

Laser Tissue Interaction

Laser interaction mechanism

Two types are:[5] 1) wavelength-dependent and 2) wavelength-independent mechanisms [Table 1].

Table 1.

Classifications of laser systems[3]

• Photothermal interaction

• Photodynamic therapy

• Biostimulation

• Photoablation therapy

The action of lasers on dental hard and soft tissue as well as bacteria depends on the absorption of laser by tissue chromphore (water, apatite minerals, and various pigmented substances) within the target tissue. The following are the possible mechanisms of laser action:

1. Photothermal ablation: This occurs with high-powered lasers, when used to vaporize or coagulate tissue through absorption in a major tissue component.

2. Photomechanical ablation: Disruption of tissue due to a range of phenomena, including shock wave formation, cavitations, etc.

3. Photochemical effects: Using light sensitive substances to treat conditions such as cancer.

Clinical Applications of Lasers in Periodontal Treatment: Initial Periodontal Therapy Scaling and Root Planing

Soft tissue lasers are a good choice in bacterial reduction and coagulation. The erbium group of lasers has shown significant bactericidal effect against Porphyromonas gingivalis and Actinobacillus actinomycetemcomitans.[6] Reduction of interleukins and pocket depth was noted with laser therapy.

Laser-assisted new attachment procedure (LANAP)

Initial reports suggest that LANAP can be associated with cementum-mediated new connective tissue attachment and apparent periodontal regeneration of diseased root surface in humans.

Surgical procedures

Many studies showed an increased coagulation and a relatively dry surgical field and better visualization.[7] Laser increases tissue surface sterilization which reduces bacteremia, and decreases swelling, edema, and scarring. Laser is effectively used to perform gingivectomies and gingivoplasties. Gingival depigmentation using laser ablation has been recognized as an effective, pleasant, and a reliable technique. Finkbeiner in 1994 suggested the usefulness of argon laser in soft tissue welding and soldering compared to conventional tissue closure method. At present, lasers are employed for frenectomy, free gingival graft procedures, crown lengthening, operculectomy, and many more.[8]

Laser and implants

Gingival enlargement is relatively common around implants when they are loaded with removable prosthesis. Lasers can be used for the hyperplasia removal as well as in the treatment for peri-implantitis. Er:YAG laser, due to its bactericidal and decontamination effect, can be used in the maintenance of implants. It has high bactericidal effect without heat generation around implants.[9]

Effects of Lasers on Periodontal Therapy

Pain relief

• Laser therapy blocks the pain signals transmitted from injured parts of the body to the brain. This decreases nerve sensitivity and significantly reduces the perception of pain.

• Increases the production and release of endorphins and enkephalins which are natural pain-relieving chemicals within our bodies.[10]

Inflammation reduction

• Laser therapy causes the smaller arteries and lymph vessels of the body to increase in size – a mechanism called vasodilatation.

• This increased vasodilatation more effectively allows the following:

  • Inflammation, swelling, and edema to be cleared away from injury sites.
  • Promotes lymphatic drainage which also aids in this vital healing process.

Accelerated tissue repair and cell growth

• Photons of light emitted by therapeutic lasers penetrate deeply into the tissues of the body to stimulate the production centers of individual cells.

• This stimulation increases the energy available to these cells, causing them to absorb nutrients and expel waste products more rapidly.[11]

Wound healing

Improved blood flow

• Laser therapy significantly increases the formation of new capillaries (tiny blood vessels) within damaged tissues.

Reduced formation of scar tissue

• Laser therapy reduces the formation of scar tissue (fibrous tissue) following tissue damage related to cuts, burns, and surgery.

• Laser therapy is able to reduce this formation by speeding up the healing process, improving the blood flow to the injured area, and more effectively carrying away waste products.

• Faster healing always leads to less scar tissue formation.[12]

Advantages of Laser

• Relatively bloodless surgical and post-surgical course

• The ability to coagulate, vaporize, or cut tissue

• Sterilization of wound tissue

• Minimal swelling and scarring

• No requirement of sutures

• Little mechanical trauma

• Reduced surgical time

• Decreased post-surgical pain

• High patient acceptance[1]

Laser Safety

General safety requirements include laser warning sign outside the clinic, use of barriers within the operatory, and the use of eyewear to protect against reflected laser light or accidental direct exposure. High volume suction must be used to evacuate the plume from tissue ablation. Several authors have studied the thermal effect of lasers on the periodontal ligament and surrounding bone.[10] Hence, periodontal tissues are not damaged if the temperature increase is kept below 5°C. A threshold temperature increase of 7°C is commonly considered as the highest thermal change, which is biologically acceptable to avoid periodontal damage.[13,14]

Recent Advances

• Waterlase system is a revolutionary dental device that uses laser energized water to cut or ablate soft and hard tissue.

• Periowave™, a photodynamic disinfection system, utilizes nontoxic dye (photosensitizer) in combination with low-intensity lasers enabling singlet oxygen molecules to destroy bacteria (Thomas, 2006).[15]

Conclusion

With conventional mechanical instruments, complete access and disinfection may not be achieved during the treatment of periodontal pockets. Lasers have the potential advantages of bactericidal effect, detoxification effect, and removal of the epithelium lining and granulation tissue, which are desirable properties for the treatment of periodontal pockets. Thus, laser systems, applying the ablation effect of light energy which is completely different from conventional mechanical debridement, may emerge as a new technical modality for periodontal therapy in the near future.[1–3]