Thursday, March 4, 2010

Lasers in Dentistry

“When will we have one laser that will be the best to do everything?”

Believe it or not, the answer to the question is quite simple: never! A more scientific way to answer the question is when the laws of physics change! ... which is still never. Despite what we as clinicians hear from salespeople, the laws of physics do not change from one company or product to the next. It is our responsibility as health–care providers to understand the scientific principles of every procedure we perform and the devices we use.

Unfortunately, the first place many dentists look for knowledge and advice should be the last, namely the salesperson. Their primary objective and responsibility is to sell us their products, not to educate or advise us on the laws of physics or how to provide quality health care. The proper place to gain knowledge and learn the science of health care is in scientific literature and academic environments, such as the ALD or AGD. The primary goal of these organizations is to be the profession’s source for information and education on the true science and clinical applications in a noncommercial, unbiased manner. This is especially true when it comes to properly understanding use of light–based technologies, particularly lasers in dentistry.

The promotion, popularity, and successful outcomes of laser treatment in other areas of health care, such as ophthalmology, plastic surgery, and dermatology, have made patients more inquisitive about the use of lasers in dentistry. This desire facilitates the investigation and use of lasers in all aspects of dentistry by patients and clinicians alike.

Almost everyone believes that laser therapy should reduce the concerns and improve outcomes over conventional dental treatment. This especially holds true for periodontal and soft tissue therapy, which covers the full range of applications from preventive to the most advanced surgical procedures as shown in Table 1. Look at Table 2 for some considerations when selecting a laser.

The mechanism of laser surgery works like this: As the laser precisely cuts or “vaporizes” soft tissue, which is called ablation, it coagulates the tissue. This controlled coagulation increases hemostasis and is almost bloodless in many cases. This hemostatic control combines with the bactericidal effect of the laser energy at the surgical site, reduces the discomfort during treatment, and minimizes the risk of infections and the need for antibiotics and sutures.

It also minimizes the inflammatory response, allowing faster and improved healing with less postoperative discomfort. This control also means that when the correct laser with the proper parameters is used for the appropriate procedure, it is often faster and more efficient.

The ability to control hemostasis allows the routine performance of both hard tissue procedures such as subgingival Class V restorations and digital impressions to be completed in the same appointment, which includes the needed gingival recontouring or troughing and the definitive restoration. The ability to combine procedures makes it more convenient for patients because fewer appointments are required and the practice’s efficiency and profitability are increased.

It is commonly known that if oral cancer is diagnosed and treated in its earliest stages, the success rate is higher. When the proper laser and techniques are used to control the collateral thermal damage, there is minimal heat artifact in the biopsy specimen. This enables the general practitioner to quickly and easily perform a biopsy with a laser when first deemed appropriate, causing minimal bleeding and discomfort to the patient during the procedure and postoperatively. Hopefully early detection will become more common.

When evaluating which laser is best for your practice, the most important considerations are: who is going to use it, what procedures it is going to perform, why it is going to be beneficial, where it is going to be placed, and how the device–specific training is going to be done.

This simple who, what, why, where, when, and how philosophy may seem very elementary, but it is all too often overlooked when a practice incorporates new technology. In laser dentistry, this also translates into investigating the science of laser physics, the ergonomics and portability of the device, the type of training included, the cost, and the dependability of the manufacturer.

How the laser interacts with tissue is strictly dependent on the laser physics. The science does not change from device to device, but the individual properties of each device do. Today, almost all dental lasers have the ability to perform soft tissue procedures with varying efficiency, depending on the wavelength of the laser energy and the ability to control that energy’s interaction with the tissue.

The benefit of laser use for soft tissue treatment and management is that the treatments are often less invasive, more precise, and very conservative, preserving the healthy tissue while treating the diseased site. These benefits greatly reduce discomfort during treatment and minimize the need for local anesthesia for many procedures.

The tissue reacts predictably with less shrinkage and with minimal inflammatory response, reducing the postoperative discomfort that has been attributed to many of these therapies. Basically, it is “what you see is what you get” treatment in the majority of cases. Soft tissue laser treatment can reduce the need for outside referrals and additional appointments, thus increasing comfort and convenience for patients and still providing state–of–the–art clinical care with minimally invasive procedures.

The ability of laser light energy to ablate (vaporize or cut) tissue is dependent on how well the energy is absorbed by that tissue, the amount of energy or power (watts), and the amount of time the energy is being emitted into the tissue. The key to achieving the maximum efficiency for this tissue interaction is to match these variables with the chromophores (absorbers of light) present in the tissue with a laser that emits the proper wavelength.

The chromophores found in oral soft tissue are water, hemoglobin, oxyhemoglobin, and melanin. With oral soft tissue being comprised of approximately 70% water, it is the primary chromophore that the laser should be targeting. A study by Cecchetti et al., demonstrated that when comparing light energies in the near infrared range, the 980 nm (nanometer) wavelength used by a few diode lasers is absorbed more than 10 times greater than the 810 nm wavelength that is used by most diode lasers, and three times more than the 1,064 nm of the Nd:YAG lasers. Mid infrared range erbium lasers with 2,790 nm to 2,940 nm wavelengths and 10,600 nm, and the far infrared CO2 lasers have significantly higher absorption in water than those in the near infrared range.

To compensate for the lack of light energy absorption of the 810 nm class of lasers, the fiber tip is initiated by blocking the light energy with the ink of an articulating paper or the carbon of a cork. This fiber tip essentially becomes a hot glass rod that vaporizes the tissue by conduction heat transferred by direct contact of the fiber with tissue.

The free running 1,064 nm Nd:YAG laser compensates for its lack of absorption by using an extremely high peak power of as much as 1,000 watts of power for a very short interval, so the average power can be the same as the diodes of only 1 to 3 watts.

The 980 nm class lasers take advantage of the tissue’s 70% water content, which allows the high absorption of its radiant light energy into the tissue to significantly enhance the laser’s ablating (vaporizing/cutting) efficiency. Additionally, the 980 nm wavelength allows for water irrigation to be used while ablating, enabling convection cooling to the surrounding tissue to control collateral thermal damage.

Also, the fact that the fiber does not need to be initiated enables the absorption of its radiant light energy in the tissue’s other chromophores of hemoglobin, oxyhemoglobin, and melanin even though the percentage of these is greatly less than water.

The fiber tip of 980 nm class laser can also be initiated and the laser can then perform in the same manner of direct contact conductive heat transfer as the 810 nm class lasers; however, this will negate the real benefit of the 980 nm radiant energy absorption and cooling of the surrounding tissue with water irrigation. By having the ability to use either radiant or conductive energy transfer and convection cooling possibly makes the 980 nm class of lasers the ideal wavelength for soft tissue ablation.

Controlling the amount of energy in each pulse of the laser light and the amount of time that it interacts with the tissue also has a significant impact on the laser’s efficiency. There is a linear relationship between the energy in a pulse of light energy and its ablation efficiency.

Increasing the laser power lowers the ablation threshold and accelerates the ablation process. This increased efficiency causes a decrease in the side effect of collateral thermal damage. Thus, the higher the peak power of a laser, the more efficiently it can ablate the target tissue. However, proper control of this energy is required to achieve the optimal outcome.

Controlling the laser energy effects on the remaining surrounding tissue is imperative. The goal in some situations may be to obtain hemostasis, and in others it might be to achieve the proper contour or emergence profile of the gingiva.

Often this is accomplished by managing the length of time the tissue is energized with laser energy relative to the amount of time it is allowed to relax, enabling the surrounding tissue to cool before the next pulse. The more a laser can control its pulse width and emission/duty cycle, the more effective the laser will be in successfully managing the outcome of the remaining surrounding tissue.

Using the high peak power with microsecond pulse features on the simple–to–use but more sophisticated lasers allows specific microscopic tissue to be precisely removed with each pulse. It also allows thermal recovery (thermal relaxation) between each pulse, therefore minimizing any collateral tissue damage and postoperative discomfort.

With a high powered 980 nm diode laser (greater than 6 watts), this precision can be further enhanced by using water irrigation for convention cooling, allowing the clinician to precisely control his or her clinical options and modes of treatment. This is especially important for procedures such as biopsies and sulcular debridement (sometimes referred to as sulcular decontamination).

Laser sulcular debridement as an adjunct therapy to conventional root planing and scaling is one of the most beneficial treatments in laser therapy. The purpose is to remove the diseased epithelium of the periodontal pocket, leaving the healthy tissue intact. The bactericidal effect of the laser energy is also used in this procedure to reduce or eliminate the bacteria of the periodontal pocket as much as possible and to form a stable clot.

The goal of this treatment is to reestablish the attachment to the tooth and reduce the pocket depth without losing any additional height of the gingival crest (recession). The goal of all laser treatment is to use the least amount of average laser energy necessary to achieve the desired response.

The use of minimally invasive soft tissue laser therapy is rapidly becoming part of the standard of care for initial to advanced periodontal therapy and various other soft tissue procedures. There are increasingly significant differences being introduced in dental lasers and it is important to understand the value of these enhancements.

It is the responsibility of all clinicians to become knowledgeable about the science of laser physics and to select the best devices for their practices. It is imperative that each practitioner become properly trained specifically on the lasers they are using to offer the best patient care possible.


LASERS AND GUM DISEASE

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