The term “LASER” is an acronym for “Light Amplification by Stimulated Emission of Radiation”. A laser is an advanced-optical energy delivery system. It operates through an energy source, primarily electricity, and a gain medium that exists within lasers that enables the amplification of light. This process allows for enhancement or excitation of atoms, which may exist in liquid, gas, or solid form. Laser technology has revolutionized various fields of medicine and dentistry. By utilizing the principles of light absorption, emission, and interaction with biologic tissues, lasers offer a more minimally invasive approach to different dental therapies. This article explores the theoretic basis, properties, tissue interactions, and clinical applications of lasers in dentistry and provides evidence from current literature on its use.

The theoretic foundation of laser technology was first established by Albert Einstein in 1917, when he introduced the concepts of spontaneous and stimulated emission of radiation. Stimulated-emission occurred when he demonstrated that atoms, when excited, could release a burst of coherent light through a rapid chain reaction. The first functional laser was developed in 1960 by Theodore H. Maiman at Hughes Research Laboratories. Maiman’s laser utilized a high-voltage helical flashlamp encircling a small tubular synthetic ruby crystal, with its 2-end faces coated in silver. A small scratch was etched into the emitting face to facilitate light emission. His measurements of the spectral line width revealed pulses of deep red light, marking the birth of the ruby laser, humanity’s first artificial source of coherent light.

The history of lasers goes back to approximately, early 1900’s, when Albert Einstein proposed the concept behind this newer technology. While early developments in laser technology played a pivotal role in shaping contemporary clinical applications across various medical and dental disciplines, it is important to note that, within the scope of this review, no significant technological innovations or new laser device inventions have been identified beyond the year 1999. ^, A summary of the historic timeline is given in Fig. 1 .

Historical timeline of lasers.

The foundation of medical laser technology began with Max Planck’s discovery of energy quanta in 1900, later expanded by Albert Einstein’s principle of stimulated emission, which became fundamental to lasers. Theodore H. Maiman built the first functional laser in 1960 using a ruby crystal, leading to rapid medical applications, including CO ₂ lasers for tissue vaporization, neodymium-doped yttrium aluminum garnet (Nd:YAG) lasers for coagulation, and visible light lasers for hemostasis. Dr Leon Goldman pioneered laser use in medicine, successfully treating melanoma and performing the first tumor excision without hemorrhage. He also established the American Society for Laser Medicine and Surgery. The 1980s saw the introduction of compact lasers for surgery, including CO ₂ , argon, and Nd:YAG lasers, though early continuous-wave models risked excessive thermal damage. A breakthrough came, when the concept of selective photothermolysis was introduced, enabling precise, pigment-specific treatments. This led to the development of pulsed dye lasers for vascular lesions and Q-switched lasers for pigment removal. Scanning technology and fractional lasers improved precision and reduced recovery time. Dynamic thermal optimization further refined treatments by adjusting energy levels in real time. These innovations have enhanced treatment safety, efficiency, and clinical outcomes.

The primary elements of a laser are an energy source or pumping mechanism, an active medium, which is an optical cavity consisting of chemical compounds, and 2 or more mirrors that form an optical cavity or resonator. ^, When energy is pumped into the medium, the atoms excite to higher energy levels. When an excited atom spontaneously falls to a lower energy level, it emits a photon. When these excited atoms interact with photons, they emit more identical photons, which eventually lead to a chain reaction. The photons reflect and forth between the mirrors at the ends of the laser cavity, moving through the active medium numerous times and causing additional emissions on each pass. This amplifies the light while keeping its characteristics. One mirror is partially reflective so that some of the photons can exit as the laser beam. Since all of these photons are produced by stimulated emission, the light produced will have 2 principal characteristics: monochromatic and coherent. This cascade effect of stimulated-emissions makes it possible for lasers to generate their uniquely focused, intense beams of light. The laser transduces the electromagnetic energy into thermal energy when it interacts with tissue or materials, and the wavelength varies with design and clinical use.

In dental practice, lasers are broadly categorized according to several parameters, including their interaction with biologic tissues, emission wavelength, the nature of the lasing medium, and their intended clinical applications. The classification framework facilitates a clearer understanding of laser-tissue dynamics, guiding their appropriate use across a range of dental procedures. The selection of a specific laser type is determined by multiple factors, such as the procedural objective, the anatomic characteristics of the target tissue (e.g. soft or hard tissue), and the associated risk of unintended thermal effects on adjacent structures. Precise calibration of laser parameters is critical, as suboptimal dosing may result in insufficient therapeutic outcomes or, conversely, excessive energy delivery leading to undesirable tissue damage. ^, The types of lasers currently used in dentistry are summarized in Table 1 .

Lasers can additionally be classified.

• 1.

  By Wavelength : UV (140– 400 nm), Visible spectrum (400– 700 nm), Infrared (>700 nm).

• 2.

  By Lasing Medium : Gas (CO ₂ ), Solid-state (Nd:YAG, erbium-doped yttrium aluminum garnet laser [Er:YAG]), Semiconductor (Diode).

• 3.

  By Mode of Operation : Continuous wave versus pulsed-lasers.

• 4.

  By Risk Level : Classified from Class I (safe) to Class IV (high-risk of tissue damage). ^,

Lasers are envisioned to transform restorative dentistry by providing minimally invasive options to conventional methods, such as diagnostic and operative modalities. Lasers can transform restorative dentistry by providing more minimally invasive options to current caries lesion interventions. Lasers, when compared to handpieces, improve safety to soft tissues, enhance comfort by reducing the need for anesthetics, and therefore increase treatment acceptance. They have the potential of being used for caries prevention, caries diagnostics, caries removal, cavity preparation, and enhancement of bonding with restorative resin. ^,,,,

By melting and fusing the enamel surface, the laser can efficiently close micropores and reduce permeability. When it comes to preventing cavities, the combination of lasers and fluoride application can work synergistically. ^, CO ₂ and Er:YAG lasers have the ability to change the enamel structure. They increase the micro-hardness of demineralized enamel. They have been proposed to raise the calcium-to-phosphorus ratio and lower the carbonate concentration, making the enamel more resistant to acid.

Lasers target carious lesions by selective ablation of the carious tissues, which have more water content than sound dentin tissue. Ablation lasers including CO ₂ and erbium lasers are beneficial; in that, ablation is carried out without the noise and vibration that are the parts of conventional methods, such as handpiece techniques. However, it must be cautioned that lasers can create excessive heat, which may be potentially harmful to pulpal tissues, with the possibility of leading to irreversible pulpal damage. This thermal hazard can be prevented by using high-flow water spray systems to minimize rise in temperature. Ultra-short pulsed lasers have been reported to accurately cut hard tissues, such as tooth enamel and dentin, with lower temperature increase than standard lasers.

Lasers can be highly effective in etching tooth surfaces due to their precise ablation and surface treatment capabilities. The integration of Er:YAG laser etching with conventional acid etching has been shown to improve tooth-resin adhesion and bond strength compared to acid etching alone. The Er:YAG laser exposes dentinal tubules while minimizing smear layer formation during cavity preparation. This may increase dentin permeability compared to rotary instruments or manual excavation techniques. Such increased permeability could potentially influence the performance of bonded-dental restorations. The durability of the resin-dentine interface may be compromised by oral biofilms containing acid-producing bacteria, which can contribute to bonding failure. Antimicrobial PDT using photosensitizer-doped dentine adhesives has been investigated, demonstrating potential for improved bond strength and antimicrobial effectiveness. These approaches have been observed to potentially minimize the extent of restorative interventions, reduce bacterial load at the site, and consequently lower the risk of infection, and secondary caries formation.

The American Academy of Pediatric Dentistry recognizes the potential utility of lasers in pediatric dental care, especially for patients with special health care needs. Lasers provide selective and controlled-tissue interaction with reduced thermal trauma compared to electrosurgical devices, hemostasis without sutures, and support for improved healing with potentially less post-operative discomfort. Additionally, these devices may enable procedures to be performed with minimal or no local anesthesia due to their analgesic properties. Selective caries removal and vibration-free operation may also contribute to reduced anxiety in pediatric patients.

Microbial infection within the root canal system is recognized as the primary etiologic factor in endodontic and periapical pathologies. Endodontic therapy in dentistry aims to eliminate bacterial infection and cleanse the root canal system.

Laser therapy has been utilized to treat hypersensitivity since 1985. Low-power lasers, such as Gallium Aluminum Arsenide, and medium-power lasers, such as CO ₂ , Nd:YAG, Er:YAG, aid in management of sensitivity. Combining laser treatment with desensitizing medications may even be more effective at controlling hypersensitivity. Lasers may also be used to prevent sensitivity following teeth whitening, deep cleaning of the roots of teeth, and to shield cervical restorations from inducing sensitivity by sealing the dentinal tubules. ^, Of the various lasers employed, the Nd:YAG laser appears to be most effective in the treatment of dentin hypersensitivity. Lasers have been shown to be useful in reducing dentinal hypersensitivity following 3 mo of therapy.