No other healthcare discipline would have benefited as much as dentistry has from the technology that surrounds light. Light cure technology revolutionized dentistry. It enabled the dentist to use photoactive materials in sealants, cement and composites, significantly increasing the scope of dental practice and reducing treatment time. It is impossible to imagine dentistry without light cure technology today. And once again, it is a light-based technology that’s propelling dentistry’s growth into the future. Just as the pen is mightier than the sword, light is lighter and sharper than a scalpel and soon there will come a time when it would be difficult to imagine dentistry without dental lasers.

LASERS are high-energy beams of light that can be aimed at specific targets and affect photochemical changes in soft tissues as well as hard tissues. This can be established in a dental clinic using fibreoptic cables with a cooling system, focusing lenses and other controls completing the apparatus.

Ever since Weichmann and Johnson first attempted to use a CO2 LASER to seal the apical foramen during a Root Canal procedure in 1971, its possible applications in dentistry have been studied continually by various physicists, scholars and doctors. Er:YAG laser was approved by the FDA in 1997 as the first dental hard tissue laser and in the decades that followed, there has been an explosion in the use of lasers for various dental procedures, a few of which have been reviewed here as follows.

Types of Dental Lasers

Applications of lasers in dentistry can be better understood by first knowing what all types of lasers can be applied in dentistry. There are 4 main types of Dental Lasers as listed below:

• Diode Lasers : These are the most frequently used lasers in dentistry due to their wide-reaching soft tissue applications. Its wavelengths range from 810nm to 980nm and all diode wavelengths are well absorbed by tissue pigment (melanin) and hemoglobin making it useful for almost all types of periodontal surgeries. Diode lasers aren’t effective against hard tissues due to poor absorption.
• Erbium Lasers : The Erbium family with its two distinct wavelengths (Er:YAG and Er, Cr:YSG) is also an important mainstay in the arsenal of the dentist who prefers lasers to carry out most procedures. This is because the Erbium wavelengths are easily absorbed by the hydroxyapatite crystals and water present in dental hard tissues, making it an effective tool to carry out hard tissue procedures like cavity preparation and caries removal along with soft tissue ablations.
• Neodymium Yttrium Aluminium Garnet Laser (Nd : YAG) : This wavelength is particularly useful for soft tissue cutting as well as coagulation making it a good tool to achieve hemostasis. Nd:YAG lasers have found implications in nonsurgical treatments of periodontitis including sulcular debridement and Laser Assisted New Attachment Procedure (LANAP).
• The CO2 Laser: With its shallow depth of penetration, the CO2 laser can be used for soft tissue removal and hemostasis as well, but it is relatively expensive, larger in size and has destructive hard tissue interactions. Hence, its use is limited.

  Applications of Dental Lasers

Soft tissue applications:- 

• Removing infected, inflamed or miscellaneous tissues: A diode laser is particularly useful in the removal or resection of targeted soft tissues with minimal damage to its surroundings and better postoperative healing. Frenectomies are routinely carried out using Diode Lasers. They also help treat gingival overgrowths and various other hypertrophic conditions. 
• Aesthetic Dentistry: Diode Lasers can be used for smile designing, gingival recontouring and crown lengthening, enabling one to achieve desirable results without the pain, discomfort and bleeding associated with conventional gingivectomies. The same principle allows diode lasers to be used to expose partially erupted or impacted teeth through conservative tissue removal. This is particularly useful during orthodontic procedures as the tooth that has been uncovered can be bonded immediately due to lack of bleeding.
• Treatment of postherpetic neuralgia and aphthous ulcers : Low levels of laser energy (HeNe), by virtue of photostimulation, provide pain relief and accelerated healing from these lesions. Photostimulation during the tingling phase of recurrent herpes simplex labialis lesions arrests the lesion before painful vesicles form.
• Disinfection and Root Canal Sterilisation: Low-power diode lasers and toluidine blue dye is an effective combination that can kill bacteria in complex biofilms (like subgingival plaque), root canals and periodontal pockets, keeping in mind that these are parts of the body beyond the reach of antibiotics. Tagging the dye with monoclonal antibodies can make this procedure species-specific. The dye gets activated by the laser, releasing oxygen molecules that cause membranous or DNA destruction in microbes.  
• Treating malignancies: The same principle (of Oxygen releasing dyes) works here too. Reactive oxygen molecules destroy tumor cells and their vasculature while simultaneously activating the host’s immunity to produce anti-cancer agents like macrophages, T-lymphocytes and TNF-alpha. Clinical studies have proven the effectiveness of this treatment modality against Squamous Cell Carcinoma of the Oral Cavity.

Hard Tissue applications :- 

Light cure technology was mentioned at the beginning of this article stressing its impact on dental practices. But did you know that, these light cure units are nothing but Argon lasers that employ high-intensity blue light to initiate photopolymerization of light-curable restorative materials? However, it was Erbium lasers that threw wide open the scope of lasers in dentistry by enabling its use in hard tissue procedures as well. Some prominent dental hard tissue applications of lasers include

• Bleaching (teeth whitening): It requires the specific absorption of a narrow spectral range of green light.
• Caries removal and cavity preparation: Various studies have recorded the use of Er:YAG lasers for caries removal using laser ablation without causing thermal changes or heat-associated damage to the pulp. The PAD (photoactivated dye) technique that employs lasers for disinfection has already been discussed above.
• Etching : Although slightly inferior to acid etching techniques with respect to adhesion, laser etching of enamel and dentin using Erbium lasers leaves no smear layer. 
• Dentinal hypersensitivity treatment: Er : YAG lasers are more effective on sensitive parts of the tooth (dentin exposed at the cervical portion) than conventional treatments used for hypersensitivity.

Miscellaneous uses of Lasers in Dentistry

Other uses of Dental Lasers include :- 

• Diagnostic applications: This includes laser fluorescence detection of dental caries (using Argon) and subgingival calculus (using Diode), using optical changes to detect fissure caries, laser doppler flowmetry to assess pulpal blood flow and using Helium-Neon Lasers to scan phosphor plate digital radiographs.
• Wound healing and pain relief : Low-level laser treatment (LLLT) of a healing wound has been shown to accelerate the healing process by causing the early appearance of myofibroblasts (cells that contract the wound) and the resultant wound has been shown to have a higher tensile strength. There are also studies that have shown that LLLT promotes healing and dentinogenesis following pulpotomy. 

In vivo studies have shown that LLLT on nerves supplying the oral cavity reduced the firing frequency of nociceptors (pain receptors), resulting in soothing analgesia. This implies that LLLT can be used to reduce post-surgical pain after periodontal procedures, root canal treatments and extractions. LLLT has also been known to stimulate nerve repair and regeneration following a neuronal injury and direct application of this technique has yielded positive results in promoting the regeneration of the Inferior Alveolar Nerve, damaged during surgical procedures.

So Why LASER? 

The advantages of shifting to more laser-centred practices in dentistry is easy to gauge. Patients becoming aware that a lot of their dental problems could be addressed without those scary sharp pointy instruments and high-speed drills parading around inside their mouths will cause an inevitable shift in preference towards the less intimidating laser-based dentistry, especially when they realize that laser procedures involve minimal bleeding with faster and better postoperative healing. This could be particularly appealing to medically compromised patients like diabetics, heart patients on blood thinners and the ones with bleeding or clotting disorders.

And with a growing versatility in the types of lasers being used, the scope of its application in dentistry is greater than ever. There are dentists now who exclusively practice noninvasive laser-based dentistry employing lasers in every possible procedure starting from routine cavity cutting to procedures that involve bone cutting, soft tissue ablations, management of lesions (like osmf, leukoplakia, lichen planus etc) and orofacial pain management. It goes without saying that they have undergone rigorous training for technique sensitivity and safety protocols, and treatments are carried out using protective eyewear at all times. They are the pioneers of the next big paradigm shift about to take place in the public perception of dentistry. Practitioners of laser dentistry continue to recommend to their peers that Diode Lasers at least, should be an unavoidable part of their dental set up because patients who are already wise to the concept will henceforth refuse to go under a knife if a beam of light could get the job done.