Laser in dentistry

Introduction of laser in dentistry, in the 1960s, by Miaman, led to a continuous research in the various applications of lasers in dental practice. 

Lasers used in dental practice can be classified by various methods: According to the lasing medium used, such as, gas laser and solid laser; according to tissue applicability, hard tissue and soft tissue lasers; according to the range of wavelength , and of course the risk associated with laser application. 

The CO2 laser wavelength has a very high affinity for water, resulting in rapid soft tissue removal and hemostasis with a very shallow depth of penetration. Although it possesses the highest absorbance of any laser, disadvantages of the CO2 laser are its relative large size and high cost and hard tissue destructive interactions. 

The Nd: YAG wavelength is highly absorbed by the pigmented tissue, making it a very effective surgical laser for cutting and coagulating dental soft tissues, with good hemostasis. In addition to its surgical applications,there has been research on using this laser for nonsurgical sulcular debridement in periodontal disease control .

The erbium wavelengths have a high affinity for hydroxyapatite and the highest absorption of water in any dental laser wavelengths. Consequently, it is the laser of choice for treatment of dental hard tissues. In addition to hard tissue procedures, erbium lasers can also be used for soft tissue ablation, because the dental soft tissue also contains a high percentage of water.

Most type used in dentistry 

The active medium of the diode laser is a solid state semiconductor made of aluminum, gallium, arsenide, and occasionally indium, which produces low wavelengths . Specific procedures include aesthetic gingival re-contouring, soft tissue crown lengthening, exposure of soft tissue impacted teeth, removal of inflamed and hypertrophic tissue, frenectomies, and photostimulation of the apthous and herpetic lesions.

What's Mechanism of Laser Action in dentistry ? How Do Lasers Work ?

Laser light is a monochromatic light and consists of a single wavelength of light. It consists of three principal parts: An energy source, an active lasing medium, and two or more mirrors that form an optical cavity or resonator. For amplification to occur, energy is supplied to the All lasers work by delivering energy in the form of light. When used for surgical and dental procedures, the laser acts as a cutting instrument or a vaporizer of tissue that it comes in contact with. When used in teeth-whitening procedures, the laser acts as a heat source and enhances the effect of tooth-bleaching agents.

The light energy produced by a laser can have four different interactions with a target tissue:

Reflection, Transmission, Scattering, and Absorption  When a laser is absorbed, it elevates the temperature and produces photochemical effects depending on the water content of the tissues. When a temperature of 100°C is reached, vaporization of the water within the tissue occurs, a process called ablation. At temperatures below 100°C, but above approximately 60°C, proteins begin to denature, without vaporization of the underlying tissue. Conversely, at temperatures above 200°C, the tissue is dehydrated and then burned, resulting in an undesirable effect called carbonization.

At low doses, laser application stimulates proliferation, while at high doses it is suppressive. It affects fibroblast maturation and locomotion,and this in turn may contribute to the higher tensile strengths reported for healed wounds.Low-level laser treatment (LLLT) of gingival fibroblasts in the culture has been shown to induce transformation in myofibroblasts (useful in wound contraction) as early as 24 hours after laser treatment. LLLT affect positively on healing of lesions of recurrent aphthous stomatitis ,  dentinogenesis following pulpotomy, the healing of mucositis and oropharyngeal ulcerations in patients undergoing radiotherapy for head and neck cancer.

Photostimulation of aphthous ulcers and recurrent herpetic lesions, with low levels of laser energy can provide pain relief and accelerate healing. In the case of recurrent herpes simplex labialis lesions, photostimulation during the prodromal (tingling) stage seems to arrest the lesions before painful vesicles form, accelerate the overall healing time, and decrease the frequency of recurrence.

Low power laser energy is useful for photochemical activation of oxygen-releasing dyes, causing membrane and DNA damage to the microorganisms. The photoactivated dye (PAD) technique can be undertaken with a system using low power (100 milliwatts) visible red semiconductor diode lasers and tolonium chloride (toluidine blue) dye. The PAD technique has been shown to be effective in killing bacteria in complex biofilms, such as, subgingival plaque, which are typically resistant to the action of antimicrobial agents and can be made species-specific by tagging the dye with monoclonal antibodies. Photoactivated dye can be applied effectively for killing Gram-positive bacteria (including Methicillin-resistant Staphylococcus aureus (MRSA)), Gram-negative bacteria, fungi, and viruses. The major clinical applications of PAD include disinfection of root canals, periodontal pockets, deep carious lesions, and sites of peri-implantitis.

4) Photodynamic therapy for malignancies 

Photodynamic therapy (PDT), which has been employed in the treatment of malignancies of the oral mucosa, particularly multi-focal squamous cell carcinoma, acts on the same principle of PAD, and generates reactive oxygen species, which in turn, directly damages the cells and the associated blood vascular network, triggering both necrosis and apoptosis .

 conventional gingivectomy is associated with pain, discomfort, and bleeding ..

An impacted or partially erupted tooth can be exposed for bonding by conservative tissue removal, allowing for reasonable positioning of a bracket or button. It has the advantage of no bleeding, and an attachment can be placed immediately , and moreover, it is not painful at all.

Isolated areas of transient tissue hypertrophy can easily be excised with the diode laser without specialist referral  . 

1) Teeth whitening 

 Lasers are used to speed up in-office teeth whitening procedures. A peroxide bleaching solution, applied to the tooth surface, is ''activated" by laser energy, which speeds up of the whitening process.

The argon laser produces high intensity visible blue light (488 nm), which is able to initiate photopolymerization of light-cured dental restorative materials, which use camphoroquinone as the photoinitiator.[54] Argon laser radiation is also able to alter the surface chemistry of both enamel and root surface dentine,[55] which reduces the probability of recurrent caries. The bleaching effect relies on the specific absorption of a narrow spectral range of green light (510-540 nm) into the chelate compounds formed between the apatites, porphyrins, and tetracycline compounds.[56] Argon and Potassium Titanyl Phosphate (KTiOPO4, KTP) lasers can achieve a positive result in cases that are completely unresponsive to conventional photothermal ‘power’ bleaching. 

Enamel demineralization with white spot formation on the buccal surfaces of the teeth is a relatively common side effect from orthodontic treatment with fixed appliances.[57,58] There is evidence, however, which suggests that such small areas of superficial enamel demineralization may re-mineralize.[59] 

Rmoving caries in the enamel and dentine by ablation, without the detrimental effect of rise in temperature on the pulp,even without water-cooling, with low ‘fluences’ laser (LLLT), similar to air-rotor devices, except that the floor of the cavity is not as smooth.The Er: YAG laser is capable of removing cement, composite resin, and glass ionomer.

Laser etching has been evaluated as an alternative to acid etching of enamel and dentine. Enamel and dentine surfaces etched with (Er, Cr: YSGG) lasers show micro-irregularities and no smear layer.

Dentinal hypersensitivity is one of the most common complaints in clinical dental practice. Comparison of the desensitizing effects of an Er: YAG laser with those of a conventional desensitizing system on cervically exposed hypersensitive dentine[67] showed that desensitizing of hypersensitive dentine with an Er: YAG laser is effective, and maintenance of a positive result is more prolonged than with other agents. 

The laser scanner can be used as a soft tissue scanner and is a valuable tool for its ease of application and creation of 3D images of oral dental structures. There is no need of cast preparation as e-models are prepared from scanned impressions. 

 

Certain precautions should be taken to ensure their safety ,Firstly protective eyewear by anyone in the vicinity of the laser, while it is in use. This includes the doctor, chairside assistants, patient, and any observers such as family or friends. It is critical that all protective eyewear worn is wavelength-specific. Additionally, accidental exposure to the non-target tissue can be prevented through the use of warning signs posted outside the nominal hazard zone, limiting access to the surgical environment, minimizing the reflective surfaces, and ensuring that the laser is in good working order, with all manufacturer safeguards in place. With regard to prevention of possible exposure to infectious pathogens, high volume suction should be used to evacuate any vapor plume created during tissue ablation, and normal infection protocols should be followed. Each office should have a designated Laser Safety Officer to supervise the proper use of the laser, coordinate staff training, oversee the use of protective eyewear, and be familiar with the pertinent regulations.