Introduction

Laser is the acronym of ‘Light Amplification by Stimulated Emission of Radiation’. The first laser (ruby laser) was invented in 1960. Since then laser became one of the new effective technology in dental practice. It was first introduced as an alternative to the normal halogen curing light but now it has become the important instrument in many dental applications. This paper gives an insight on laser in dentistry.

Historical review

Past ten years was a perfect example for clinical application of lasers in dental practice and an international attention has been given by the organizations to this technology. Laser was considered as a complicated technology with limited use in clinical dentistry, but now there is an increasing awareness of the use of lasers in the modern dental practice, where they are used as an alternative to already existing approaches. Its advancement in the field of dentistry is playing a major role in patient care and wellbeing.

Theodore Maimam invented the first synthetic ruby laser in 1960. Ruby lasers need too much energy that will expose the pulp to thermal effects and cause collateral damage to adjacent hard and soft tissue due to scattered radiation. At Bell Telephone Laboratories, Kumar N Patel invented carbon dioxide laser in 1964 which was the first one that can be applied on hard tissue and soft tissue. Later in 1965 Goldman et al. exposed a vital tooth for the first time to laser energy, where there was no experience of pain and had only minor, superficial damage to the crown. In 1961 Weichman & Johnson, tried in vitro to seal the apical foramen using high power infrared (CO 2) laser. The effect of Er:YAG laser on dental hard tissues was described by Hibst and Paghdiwala, 1988. But for the use of cavity preparation laser obtained its approval from USFDA in 1997. First company to release Er:YAG lasers into the market was KaVo (Germany) in 1992. Second one to develop and release erbium laser hard tissue wavelength (Er:YSGG, 2.78 µm) was Biolase (USA). The emission wavelength of erbium family laser coincide exactly with absorption peak of water, due to which biological tissues, enamel and dentin experience strong absorption. That is the reason why these lasers are most popular soft and hard tissue lasers today.

Laser types and delivery systems

Lasers used in dentistry are named depending upon the physical structure of the laser (e.g., gas, liquid, solid state, or semiconductor diode), type of the medium that undergoes lasing (e.g., Erbium: Yttrium Aluminium Garnet (Er:YAG). A laser that delivers the laser energy efficiently to the target site is considered as an effective and useful laser. The available laser delivery systems are:

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.

The popular choice for most lasers are fiber optic delivery systems as they can distribute laser energy to most parts of the oral cavity even to the complex root canal system. Fiber optics delivers laser energy from the bare end of a plain tip in a forward direction with minimal divergence. Laser light is unique, monochromatic (light at one specific wavelength), directional (low divergence) and coherent (all waves are in a certain phase relationship to each other). Directional and monochromatic laser lights are delivered on to the target tissue as a continuous wave or in a gated-pulse mode or in a free running pulse mode. Beams are continuously emitted as long as the foot switch is pressed in continuous waves. The gated-pulse is an on and off laser and the duration of it is in microseconds, while in free running pulse mode large amount of laser energy is emitted for very short period of time.

 Common laser types used in dentistry

For detection of dental caries in pits and fissures, laser fluorescence offers greater sensitivity than conventional visual and tactile methods.

Lasers are divided into four groups:

• Class I (safe)
• Class II and IIIa (eye is protected with a blink reflex)
• Class IIIb (direct viewing is hazardous) and
• Class IV (laser power is above 0.5 Watts, and this laser is known to be extremely hazardous).

Most dental and medical lasers are class IV, and thus compliance with safety standards is necessary to protect the dentist, patient and support staff.

Uses of lasers in dentistry

Laser technology has developed so much that it is being used in almost all the branches of dentistry. Following are the applications of the lasers in dentistry:

1.Diagnosis:

• Detection of pulp vitality
• Doppler flowmetry
• Low level laser therapy (LLLT).
• Laser fluorescence- Detection of caries, bacteria and dysplastic changes in the diagnosis of cancer

2.Hard tissue applications:

• Caries removal and cavity preparation
• Re-contouring of bone (crown lengthening)
• Endodontics (root canal preparation, sterilization and Apicectomy.)
• Laser etching.
• Caries resistance

3.Soft tissue applications:

• Laser-assisted soft tissue curettage and peri-apical surgery.
• Bacterial decontamination.
• Gingivectomy and Gingivoplasty.
• Aesthetic contouring, Frenectomy
• Gingival retraction for impressions
• Implant exposure
• Biopsy incision and excision
• Treatment of aphthous ulcers and Oral lesion therapy
• Coagulation / Hemostasis
• Tissue fusion - replacing sutures
• Laser-assisted flap surgery
• Removal of granulation tissue
• Pulp capping, Pulpotomy and pulpectomy
• Operculectomy and Vestibuloplasty
• Incisions and draining of abscesses
• Removal of hyperplastic tissues and
• Fibroma

4.Laser-induced analgesia
5.Laser activation:

• Restorations (composite resin)
• Bleaching agents

6.Other:

• Removal of root canal filling material and fractured instrument
• Softening gutta-percha
• Removal of moisture/drying of canal.

Laser safety

Safety measures that are to be taken include using barriers in the operating field, general warning sign in the clinic and use of glasses to protect against reflected laser light or direct exposure that can occur accidentally. Eyewear selection should be based on the type of laser system that is being used. Adverse effects that can be caused are dependent on the wave length and absorption characteristics of the laser. Use of high volume suction is advised for removal of plume from tissue ablation. The laser should be stored as per manufacturer’s instruction and should be checked and serviced regularly. Apart from these general measures adequate precautions to prevent damage to soft and hard tissues, periodontal ligament are to be taken by the dentist. In Dental laser safety Zach and Cohen described that increase of intra-pulpal temperature to 5.5°C results in necrosis of the dental pulp in 15% and temperature increase up to 11- 17°C will lead to necrosis in 60 to 100% of cases. Supporting periodontal apparatus is sensitive to a temperature of 47°C and temperature of 60°C and above will cause bone necrosis by permanently stopping the blood flow. That is the reason it is advised to maintain the temperature below 5° C.

Conclusion

Since the last decade there is a noticeable advancement in laser technology. The establishment of lasers with emergence of lasers with different wavelengths and abilities is influencing the treatment planning and treatment options in dentistry by reducing the treatment time and relieving patients from needle prick, sharp instruments trauma.

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