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Previous What's New Articles
- April 2008 - Exercise, Nutrition, Dental Health
- September 2006 - Osteonecrosis
- August 2006 - Lasers in Dentistry
- July 2005 - Decay Prevention with Xylitol
- June 2005 - Periodontal Disease
Lasers in Dentistry
What is a laser?
The term laser is actually an acronym for Light Amplification by Stimulated Emission of Radiation. A laser is simply a type of light that has specific properties that enable it to perform work.
All light is a form of energy that travels in a wave and exists as a particle called a photon. Photon waves have three properties. One is amplitude, which is a vertical measure of the height of the wave and describes the energy of the wave. Another property is the length of the wave, which determines the color of the light, and a third is the velocity, or speed of the light.
Whereas everyday light sources such as light bulbs display a variability of amplitude and wavelength and scatter light in many directions, a laser light is very specific. It has an unvarying wave height, a single wave length of one color, and a focused beam. These properties allow the laser to utilize its concentrated light energy to provide heat, which is able to perform work such as cutting tooth or soft tissue.
A laser is able to deliver precise light because of how it is constructed. A laser contains a core of a gas or solid, surrounded by a pumping mechanism that supplies the initial light (photon) energy. Once this energy is initiated, the photons resonate and reflect in the core chamber to a specific vertical height designated by the chamber. The photons proceed down the length of the chamber, emitting the specific wavelength of light needed for the procedure at hand.
A laser light is a form of electromagnetic radiation just like all other sources of light. It is important to realize that this is different from ionizing radiation, which can cause mutations in DNA. Patients should know that lasers are not like x-rays.
How do lasers work in dentistry?
Because lasers are so precise in what they can do, there are several unique types of lasers used in dentistry for varied purposes in hard or soft tissue. They are designed with different wavelengths that have different absorption capabilities that recognize and interact with different types of human tissue. For example, short wave lasers, such as the diode and Nd:YAG, have a high affinity for tissue pigments such as hemoglobin and melanin and are used for soft tissue surgery. Longer wave lasers such as the Er:YAG (erbium) lasers are used for teeth and bone because they have an affinity for water and can recognize the decayed part of the tooth because of differences in water content between solid and decayed tooth structure.
The laser emits light energy either in continuous or pulsed states. Most dental lasers involve pulsed energy release. The pulse, or burst, of light, delivers the laser’s heat energy quickly (each pulse lasts only a few ten thousandths of a second) and then allows the tissue time to cool before initiating another blast. This heat energy pulse works by either boiling away water within and between the cells, or by causing micro expansion of hard tissue, resulting in a tiny explosion that removes the unwanted tissue. The procedure consists of a series of “pops” that work to remove decay or cut away or shape tissue or tooth structure.
How are lasers better than other dental tools?
Dental lasers are very precise cutting instruments, and because they are so specific for tissue type with such a focused beam, they do not affect surrounding tissue. For example, they are very efficient at removing decay and keeping a filling small because they are selective for the higher water content of decayed tissue, leaving the healthy tooth structure alone.
Lasers also work better than a scalpel for surgery because they can cut soft tissue and seal it at the same time, much like how heat can seal the end of a rope. This results in almost bloodless surgery.
There is also no vibration with a laser. This property makes a laser very steady it is less likely to cause micro cracks that can occur with a drill.
The laser also kills bacteria, greatly reducing the amount of bacteria in the area being worked on. This is particularly beneficial when the tooth being worked on involves a deep cavity or an exposed pulp that can become infected if bacteria levels are not reduced.
What about safety?
For many people, their only exposure to the idea of a laser comes from science fiction movies that talk about “photon energy” and then show a light saber destroying the side of a spaceship. This is not what dental lasers do. Each laser is designed for specific tissue and for specific levels of penetration.
A laser used to remove decay has a hard time cutting through healthy enamel because of its low water content.
A soft tissue laser works on pigment and will not harm surrounding bone or tooth at the settings used for soft tissue. The NdYAG soft tissue laser travels right through healthy soft tissue to diseased tissue. Since diseased soft tissue has a higher hemoglobin content and melanin from the bacteria, the laser light is absorbed by the tissue without affecting the healthy tissue.
The laser does emit a high heat, but it is dispersed so rapidly that the heat is not retained by the tooth or soft tissue. Studies have shown that a drill actually heats up the tooth more than a laser does.
Of course, the dentist must always take care to use the proper laser at the proper settings for each different use, but this is no different than how a dentist uses other dental tools. It is also important for the dental professionals and patients alike to use safety glasses while the laser is being used since laser light could potentially cause eye damage.
Laser Certification of Dentists
At our office, all dentists who are using the lasers have been certified by the Academy of Laser Dentistry. This is an organization dedicated to providing education about lasers and testing dentists to insure that standards of care are met. The group is composed of researchers, academic professionals, and practicing dentists, and the instructors of this prganization have no affiliations to any manufacturers. Laser cerification is voluntary at this time, but at this office we believe that it is important to obtain infomration and education from objective sources, so we have made certification a requirement for laser use in our practice.
What are the specific types of lasers?
Neodymium:YAG (NdYAG) This is a deep pentration laser designed for soft tissue use. The emission wave length is 1064 nm in the near infrared spectrum. It works by selective absorption of dark color such as melanin or hemoglobin. It ablates by photo thermal, or heat burning. It provides good hemstasis.
Erbium YAG (ErYAG) Thislaser has a wavellength of 2940 nm and lies near the boundary of the near infrared and mid-infrared invisibleportion of the spectrum. Its energy output is up to 400mJ. The light of this laser is highly absorbed by water. It has a minimal temperature rise in use, which makes it safe for use on hard tissue for removing tooth decay without cracking or melting the tooth.
Diode Laser This laser has a laser beam wavelength of 810 nm in the near infrared invisible spectrum. It operates either as a continuous wave or gated pulsed. It is a soft tissue laser and has specialized applications for various surgeries. When used with the continuous wave operation, it can trigger nerve response so local anesthesia may need to be used for some uses of this laser.
Diagnodent Laser This laser has a laser wavelength of 655 nm in the redspectrum. It is a continuos wave laser that excites molecules in tooth decay. Iit picks up reflectd light and sends a signal to the laser to indicate decay. It works by detecting the difference in fluorescence between health tooth and decayed tooth.
Why doesn’t a laser hurt?
It is not completely known why the laser doesn’t hurt, but some of the reasons involve how fast the laser works, how it cuts, how it seals, and its actions on nerves.
Rapid, repetitive action fails to trigger nerve response
- quick explanation - A laser works with heat energy that vaporizes specific diseased tissue. This happens fast, and occurs through repeated pulses; it has been theorized that these repetitive rapid actions do not trigger a nerve response and hence do not trigger pain.
- more complete explanation - While each individual pulse action of a laser may be too fast to trigger a nerve response, repetitive pulses could provide a cumulative effect to cause a nerve to be stimulated. The key for a laser to avoid causing a nerve response (and pain) is the rest time between pulses. It needs to be long enough so that the additional pulses are not additive to the previous pulses. In most cases, this is how the laser works. However, there is variation among patients in their reaction, and there is variation for dental procedures in the timing of pulses, so this explanation for the reason that lasers do not cause pain is not the entire answer.
Precise nature of laser reduces effect on surrounding tissue
- quick explanation -The preciseness of the laser allows it to target the diseased tissue alone. Decayed tooth areas do not contain nerves, whereas healthy tooth areas surrounding them do. When a dentist uses a drill, surrounding areas are going to be affected and nerves triggered. With lasers, being able to avoid the enervated areas can reduce or eliminate pain.
- More complete explanation – This holds true more for dental decay than for soft tissue surgery. Also, access to decay may involve penetration through some healthy dentin (particularly for cavities between teeth), so many cavities can not be repaired simply by removing decayed tissue without nerves. However, avoiding enrevated areas can reduce or eliminate pain for many cavities, particularly if accessis through the chewing surface.
The sealing nature of laser on soft tissue reduces inflammation response
For soft tissue use, the additional laser benefit of sealing tissue as it cuts results in much less inflammation and tissue damage and less postoperative pain. Because the laser cuts so precisely the damage from an incision does not stimulate the mediators of inflammation so there is less inflammation at the surgical site, resulting in less pain and more rapid healing than traditional surgicaltechniques.
Analgesic action of lasers – possibly nerve calming
Finally, there is some indication that lasers may have an analgesic, or calming, effect, on nerves. Research is ongoing in this area to determine if lasers can actually be used to prevent pain during surgery. It is believed that anti inflammatory action on the nerve cell membrane could work similar to a local anesthetic.
What dental procedures can lasers perform?
Fillings – Lasers can remove decay in most cases. Prepping the filling is generally accomplished without any need for a shot. However, lasers can not remove old silver filling material because the heat of the laser would vaporize the mercury in the fillings. Lasers may be difficult to use for some large fillings, and removing some specific type of composite filling material can be slow.
Periodontal disease surgery – Lasers are wonderful for soft tissue periodontal surgery. Laser surgery can often take the place of traditional scapel surgery. Laser periodontal surgery is used to remove diseased soft tissue and is generally bloodless and painless, with no need for anesthesia. The laser also reduces periodontal infection with this procedure by killing the periodontal bacteria causing the disease.
Dental lasers can also be used for more involved gingival flap surgery. With this type of surgery, anesthesia will most likely be necessary, but post operative healing is still reduced comparedto traditional surgery.
Diagnostics-finding decay – The Diagnodent laser is used for finding hidden decay in teeth. As mentioned earlier, it works by detecting the difference in fluorescence between healthy and decayed tissue To get an idea of what the laser detects, one can think about the Smithsonian’s display of “glow in the dark” rocks. Decayed tooth also “glows” and when detected, the Diagnodent emits a beeping sound. Diagnodent can not detect all decay because it only has a depth penetration of 2 millimeters. X-ray examination must still be used for decay hidden deep under existing fillings or deep between teeth. However, this laser is wonderful for finding early decay that can not be detected through other means,orfor determining beginning decay around the edge of an existing filling. When used within its depth parameters, the Diagnodent is 92% accurate, a higher rate than for a dental explorer.
Oral surgery – The laser is the tool of choice for many oral surgery procedures. Although not all surgeries can be accomplished without any anesthesia, the laser does speed up healing time immensely, providing minimal trauma to the area. Procedures such as eliminating tongue ties, uncovering implants, crown lengthening, or removing cysts and tumors can all be performed by a laser.
Adjunct use in crowns – A crown preparation involves removing the outer layer of the tooth, carving it down to accept the fabricated crown. Since portions of this tooth being prepped are healthy, the laser will not be an efficient cutting tool. However, the laser can be used to form the channel required to take an impression for the crown. This procedure replaces the procedure of temporarily packing the gum tissue with a cord. Patients who have had this procedure performed have commented that it is much more comfortable than the traditional crown prep procedure, with a lot less discomfort after the procedure.
Root canal access – The laser can be used to gain access for root canals. The laser does not allow the dentist to completely clean out the pulp, but it can help sensitive patients get through the beginning part of the procedure. We have had patients whose infections caused sensitivity so bad that they could not be touched with traditional dental instruments or even a finger, yet they were able to tolerate access with the laser. The laser can also be used after cleaning out the roots to help sterilize them before filling.
Limitations of lasers
Sometimes it is easy to think of a laser as a magic wand because it can do so much so well. However, as described in previous sections, it does have its limitations, and patients can not expect that it can totally replace other dental tools. Removal of old amalgam filling material, preparation of some large fillings or crowns, and completing root canals can not be accomplished with a laser. There are limitations to the diagnostic capabilities of the Diagnodent laser. Overall, however, the different lasers that we have incorporated into our practice have provided patients with state of the art dental care that has made coming to the dentist a lot more pleasant.