Reader's Forum

Dear RDH:

I was very pleased to read the recent article written by Lisa Dowst-Mayo in RDH magazine (June 2008). I truly believe the article was very much needed to clarify a lot of misconceptions and to shed some light on some of the most recent advances on the use of dental lasers. I also applaud the preparation of the user-friendly glossary presented as an appendix to the article.

I have been using lasers for several years, and my personal experience extends from the CO₂ laser to Nd:YAG, and to the diode laser. In reading Dowst-Mayo's article, I would like to add some additional information about the field of lasers.

I would like to focus attention first on the periodontal applications of lasers. In the article by Dowst-Mayo, it is quoted that the LANAP laser is unique in its application since it can regenerate periodontal tissues without much pocket shrinkage. While I would note that LANAP is a procedure and not truly a laser type, also the CO₂ laser has been used for periodontal regeneration. The CO₂ laser was used by Dr. Crespi and his group for periodontal regeneration and periodontal instrumentation both in vitro and in vivo with data from human and animal studies.

His overall findings indicate that the CO₂ instrumentation promoted fibroblast attachment on extracted teeth, promoted periodontal regeneration in animals, and promoted bone formation in humans, with gain of clinical attachment level.1,2,3,4

One additional observation that I would like to add to Dowst-Mayo's extensive review is the data on the use of the laser to suppress growth of periodontal pathogens. In her review, she quotes a study done at UCSF where the diode laser has “only effect” on P. gingivalis.5

The above mentioned study “only” looked at P. gingivalis as tested microorganisms grown in vitro in a pure culture environment. However, an in vivo study done on animals by Fontana et al.6 shows that the use of an 810 nm diode laser was able to reduce bacteria such as Prevotella species, Streptococcus beta-hemolitico, Fusobacterium species, and Pseudomonas species from periodontal pockets.

A human clinical study was conducted by Haraszthy et al. indicating that the use of an 810 nm diode laser was able to reduce the colony-forming units of Actinobacillus actinomycetemcomitans after mechanical and laser instrumentation of pockets deeper than 5 mm.7

As we all know, this bacteria does penetrate the soft tissue facing the periodontal pockets and its mechanical eradication is at time difficult, requiring the use of systemic antibiotics.

Dowst-Mayo also states, “It emits a red beam of light and vaporizes decayed tooth structures…” The red light is the aiming beam, still a laser beam as well, but it works as a laser pointer, has no mechanical effect on the tissue. Furthermore, hard tissue is ablated by the laser, the organic component is eliminated, and the dentin or enamel gains a glassy, vitrified, dome-shaped characteristic appearance.

I also wonder what the author means by stating that the light (the laser), if reflected will create little or no damage. Unfortunately, if a laser beam is reflected by a mirror surface, it may induce problems far away from the operating field, such as the operator's or the assistant's eyes, and that is the reason why proper protective eyewear, corresponding to the specific wavelength use, is a must to wear — for the operator, the assistant, and the patient as well.

In this regard, I would stress the importance of being aware of the kind of tissue and the kind of laser and their general interaction. The article focuses on some aspects of this very critical issue. Each laser has a different wavelength, and within the same wavelength different power levels can be used, and within the power levels, different modes can be used — continuous or pulsed. Within the pulsed mode, different duty cycles are available; that is, within the actual time of a pulse, only a portion of that pulse is active emission of laser.

Considering all the above parameters, especially when dealing with soft tissue and also in the endodontic space of non-endodontically treated teeth, the water content, which means the amount of inflamed tissue, the type of tissue (fibrotic vs inflamed), and the relative amount of pigmentation (hemoglobin) will dictate the effect of the lasers.

The article by Dowst-Mayo also reports an FDA report dated 1995. While that report is still valid in regard to the four types of lasers approved, since that date other reports have been published by the FDA in regard to other types of lasers, such as diode laser (see one example of approval dated 2003 at http://www.fda.gov/cdrh/pdf3/k031819.pdf).

One additional observation about the article is the comment on the rise of temperature when using the Er:YAG laser. An in vitro study conducted by Park et al.8 has clearly indicated that the intrapulpal temperature following Er:YAG laser irradiation rises, therefore, the authors suggest the use of water spray in combination with the laser. The study was conducted with the teeth at room temperature and the actual rise of temperature on the opposite site of the laser was statistically significant.

The same authors commented in their article that “while the temperature on the irradiated pulpal wall remained constant with no significant rise during simultaneous application of the water spray with the laser beam, it increased gradually for a few seconds after ceasing the water spray and laser irradiation, leading to maximum temperature. …the cooling effect of water suppressed the temperature rise at first, but that, with time, thermal accumulation by laser energy on the ablated site exceeded the cooling effect of water.”

While the data is quite interesting, it should be considered that the study was conducted in vitro, on extracted teeth, maintained at room temperature, and using an Er:YAG at 300 mj/pulse and 20HZ, with a water flow rate of 1.6 mL/min. for 3 sec.

One last comment is in regard to the temperature rise when the diode laser is used. It is common practice to clean constantly the laser tip when it is used after mechanical scaling/root planing. The laser tip delivers heat. It is important to note that this type of laser works on contact, when used for this kind of application. The laser tip ablates soft tissue, and the tip collects black charred tissue at the very end. This charred tissue collects heat, and therefore needs to be removed during the procedure, as typically recommended by the manufacturers.

Recent in vitro studies presented at the AADR in Dallas in March 2008 have shown that when the diode laser is used at power parameters ranging between 0.8 and 1.0 watts, the temperature rises approximately 5.0 C. The study was done on layers of soft tissue kept at 36.5 C.9

In conclusion, while being personally grateful to Lisa Dowst-Mayo for her very interesting, detailed, and needed article to help consumers and dental professionals better appreciate the use of lasers and why more and more clinicians are interested to laser dentistry, I believe the laser users and potential buyers would benefit from reading the proper literature, contact laser manufacturers, and attend laser organizations such as recommended by Lisa Dowst-Mayo for a more comprehensive understating of the biological effects of lasers, and the different characteristics of each laser.

In regard to the use of lasers for dental hygienists, I would strongly encourage professionals to 1) contact their state dental boards (as each state regulates RDH practice issues) or their association, the ADHA. To the best of my knowledge, the latter does not currently provide this type of information; however, professionals can periodically consult their Web site (http://www.adha.org/governmental_affairs/practice_issues.htm) for updates.

I would like to conclude this letter by thanking again Ms. Dowst-Mayo. It is through people like her — informed and enthusiastic about the use of lasers — that the dental community becomes aware and informed of the possibilities of lasers in dentistry.

Sebastiano Andreana, DDS, MS
Loma Linda, California

References

Crespi R, Covani U, Andreana S, Grossi SG, Genco RJ. CO₂ laser therapy in periodontal disease. J Periodontol 64:1103.
Crespi R, Covani U, Andreana S. Bone formation after CO₂ laser periodontal therapy. Radiological findings after 2 years follow-up. Abs 4th International Congress of International Society for Lasers in Dentistry. Singapore, Aug.
Crespi R, Barone A, Covani U, Ciaglia RN, Romanos GE. Effects of CO₂ laser treatment on fibroblast attachment to root surfaces. A scanning electron microscopy analysis. J Periodontal 2002; 73 (11): 1308-1312.
Crespi R, Covani U, Margarone J, Andreana S. Periodontal tissue regeneration after laser therapy. Lasers in Surgery and Medicine. 1997: 21; 4: 395-402.
Harris DM, Yessik M. Therapeutic ratio quantifies laser antisepsis: ablation of Porphyromonas gingivalis with dental lasers. Lasers in Surg Med 2004; 35: 206-213.
Fontana CR, Kurachi C, Mendonca CR, Bagnato VS. Microbial reduction in periodontal pockets under exposition of a medium power diode laser: an experimental study in rats. Lasers in Surg Med 2004; 35: 263-268.
Haraszthy VI, Zambon MM, Ciancio SG, Zambon JJ. Microbiological effects of diode laser treatment of periodontal pockets. J Dent Res 2006; 85 Spec Issue A, Abs 1163.
Park NS, Kim KS, Kim ME, Kim YS, Ahn SW. Changes in intrapulpal temperature after Er:YAG laser irradiation. Photomedicine Laser Surg 2007; 25(3): 229-232.
Beneduce C, Angelova D, Angelov N, Andreana S. Thermal propagation of 810nm diode laser in porcine dermal tissues. J Dent Res 2008; 87 (A): # 950.

Dear RDH:

I want to start out by saying that I love your magazine! I am writing in response to a Readers' Forum letter in your October 2008 issue. The letter was written by Sue Morrison from Chicago. I have one word to describe my response to her letter: “Ouch!”

I understand her response and empathize with both authors. I did get the feeling, however, that the supervised neglect article was more venting than anything else. We've all worked for doctors who looked more at the bottom line than we would like; however, the verbal spanking Sue gave was, while accurate, a tad harsh.

Kate Kline, RDH
Fairfax, Virginia

Dear RDH:

I have been practicing dental hygiene for most of the 43 years since I graduated from the University of Minnesota in 1965. It has been quite a ride! Along the way, I have had some wonderful opportunities, including a number of years of administration in both a group and solo practices, and being one of the charter members of the RDH Editorial Board when the magazine first came to fruition in the early 1980s.

I am retiring at the end of the month. Before I do that, I want to compliment Mark Hartley and the current editorial board for continuing to improve RDH so that it has become a staple in the continuing learning process of so many hygienists. Dental hygiene has been a blessing for me in more ways than I can count. I am proud of the professsion and I think hygienists will continue to lead the way in the area of prevention — but now with a “whole body” emphasis rather than the neck-up approach we learned so many years ago. Keep up the good work!

Sue O'Brien, RDH
Arden Hills, Minnesota

Editor's Note

We, of course, would like to extend our best wishes to Ms. O'Brien for her retirement. Attached to her letter that appears in this month's Readers' Forum was her version of “All I really need to know I learned in kindergarten.” Ms. O'Brien titled her version “Everything I need to know about life I learned from my patients.”

It reads:

A true affection for someone can be established in little more than an hour every six months.
People's ability to withstand nagging is endless.
People are kind, even if you cause them discomfort. They don't bite. Goodness abounds.
Life is good; difficult things happen but people are amazingly resilient.
The tooth fairy does exist in the form of good parents willing to sacrifice energy and resources for the sake of their children's health.
Learning is a lifelong process and the best of it happens when listening to each other with the ear and the heart.
People can change. Even us “old dogs” can learn new tricks.
A grouchy patient isn't a grouch at heart; he is usually fearful. He'll smile when he goes out the door.
People are courageous; some things are hard but they do them anyway.
A spoonful of sugar makes the medicine go down. But be sure to brush afterward!