> It is a monochromatic optical laser that has a specific wavelength and its rays are parallel.... Lasers transmit focused energy to the tissue through the tip of an optical fiber.... Three types of lasers are used in dentistry: carbon dioxide laser, carbon dioxide laser, erbium laser, diode laser... Since 1970, the CO2 laser has been used as an effective tool in the removal of oral mucosal lesions. The advantages of laser therapy include selective removal of the epithelium, minimal damage to the surrounding healthy tissue, excellent wound healing, minimal scarring, good functional results, no damage to the dental pulp, increased antimicrobial properties by the patient, and increased better acceptance.. Sensitivity** Laser helps to treat increased pulp sensitivity with 2 mechanisms: One is the direct effect on the electrical activity of the nerve fibers inside the dental pulp, which causes depolarization of the c fiber and lack of pain transmission, and by melting the tubules and their recrystallization, it causes a change in the structure of the dentine tube and a decrease in the permeability of the dentine. For this purpose, Doppler laser flowmetry is used. Scattering in the beam and returning some of them.. The test is very useful because it does not depend on the patient's sense.. **3- Pulp coating** Calcium hydroxide in direct contact with the pulp creates a layer of necrosis, the dentin of the small area exposed to light is softened and hardened again with the laser and the exposed area is closed, then calcium hydroxide is placed on that area to cause tooth dentin without contact with the pulp... The laser itself also directly stimulates the formation of dentin and also sterilizes the exposed area... **4- Cleaning the root canal** The available materials for cleaning the inside of the canal have limited antibacterial effect.... The high-power laser beam has antibacterial properties and removes the smear layer caused by the mechanical cleaning of the canal wall, but it produces a lot of heat.... So if you can use a low-power laser, the energy required to destroy bacteria and the risk of damage to the PLD membrane is reduced.. **1- Detection (fluorescent laser) and caries removal**: When the laser light shines on the decayed areas of the tooth, the bacterial metabolite starts emitting fluorescent light at a certain wavelength.... In this way, the laser helps to detect the local lens on the tooth.... The heating of the water in the tissue causes the sudden expansion and explosion of the liquid and dislodges the parts and destroys the decayed areas.... **2- Reduction of recurring caries** By changing the structure of the enamel of the root and dentin, the laser reduces recurrent caries. **3- Treatment of restorative substances** Lasers, for example, argon laser for polymerization of materials that have an activator sensitive to laser light... **4- teeth whitening** Bleaching gel is placed on the teeth and is activated by laser light, which kills colored substances and whitens the teeth.. Laser is used in pre-prosthetic surgery, removal of benign and malignant lesions, and removal of vascular lesions, especially in patients with coagulation problems. All three have good results, but the advantages of laser include selective removal of defective tissue, minimal damage to surrounding healthy tissue, excellent wound healing with minimal scarring, good functional result, shorter operation time, reduction of bleeding, swelling and pain after surgery and no need for drug treatment.. Periodontal treatments ** **1- Detection of mass and bacteria** For this purpose, the fluorescent laser process is used.... In this way, by irradiating a laser beam with a certain wavelength, the bacteria emits fluorescent light from itself, and the reflection of this light helps to control scaling... **2- Destroying bacteria** By adding a colorant to the teeth, they attract decay and bacteria, and with laser radiation, the color produces oxygen free radicals and destroys the bacterial membrane and DNA, which is effective in destroying the bacteria in the biofilm and subgingival plaque that remains when antimicrobial agents are used. In general, the positive view of society towards laser and its application is of great value in using this method in modern treatments... The use of this technology reduces the fear and anxiety caused by the rotation of the devices, reduces the noise of the turbine, does not require anesthesia injection, reduces the working time and reduces the pain and bleeding, but what is important is to prepare along with the work experience.