Abstract
I
Periodontal disease was proven to be a local infectious disease in 1965 in a study of “Experimental gingivitis in humans” by Löe et al. 1 Periodontopathic bacteria were identified in 1977 by Socransky, 2 and the concept of “Red Complex” evolved from a deeper understanding of biofilm. A paradigm shift developed with regard to periodontal disease as a host–parasite interaction. It came to be understood that periodontal disease is the result of inflammatory and immunologic reactions to bacteria. During this period, the concepts involving “risk factors,” including environmental and genetic factors, were attracting attention. Furthermore, the concept of “Periodontal Medicine” was introduced, and the potential for bidirectional relationships between periodontal disease and the systemic diseases was explored and continues to be expanded today with better understanding.
For quite some time, many nations have been experiencing aging populations. The most notable of these is the “Super Aged Society” of Japan, the result of extended life expectancy and subreplacement fertility rates, where the population has been aging at the world's fastest rate for the past 50+ years. Japan is not alone in experiencing this super-aged phenomenon; the world is aging at an alarming rate with more countries becoming super-aged. It is not enough to simply live longer if the quality of life detracts from making life worth living. One of the critical contributors to quality of life in an aging society is a healthy life expectancy. From this perspective, it has never been more important to incorporate improved periodontal disease management to potentiate a healthy life expectancy. To that end, many advances in the management of periodontal disease, such as periodontal plastic surgery, regenerative surgery, cytokine therapy, implant therapy, and laser therapy, have significantly contributed to improvements in quality of life as we enjoy increased life expectancy.
A few years ago, the Nobel Prize in Physics was awarded to three Japanese researchers for their work in the development of the blue light-emitting diode (LED). This made it possible to combine the use of lasers and LED light in the medical and dental fields, allowing the development of novel therapies. The history of dental treatment is closely tied to the cutting efficiency of mechanical tools. The development of step-driven engines, electric engines, and air turbines led to increases in cutting efficiency. Because cutting produces friction, mechanical operations are accompanied by vibrations, shock, and heat generation. In dental treatment, this produces unpleasant vibrations, sound, pain, and bleeding. Patients would prefer gentler treatments. One solution is the application of light as a laser, which in addition to being free of the unpleasant effects of mechanical treatment, provides the added benefits of sterilization and detoxification via laser irradiation. Most diseases of the oral cavity are biofilm-associated infections. Lasers are extremely effective tools for use in treating these diseases. In addition, lasers are not associated with side effects, such as the development of drug-resistant bacterial infections that may occur subsequent to antibiotic chemotherapy.
When the beam of a high intensive laser irradiates a target area of biologic tissue, the light energy is focused very close to and immediately beneath the irradiated area. This is thought to have a biostimulatory effect. A photosensory receptor catches light energy at the cell surface. Laser energy captured by the receptor results in a signal being transmitted to the nucleus. The expression of cyclooxygenase-2 (COX-2) mRNA is stimulated in the nucleus, leading to the synthesis of COX-2 protein. COX-2 metabolizes the arachidonic acid present at the cell surface, producing a very small amount of prostaglandin E2 (PGE2). 3 This induces increased vascular endothelial growth factor and transforming growth factor-β expression, and, in conjunction, suppression of tumor necrosis factor-α resulting to promote wound healing. It is also thought that an irreducible minimum of PGE2 acts as a regenerative system and that the mechanism of biostimulation involves PGE2-mediated signaling. A previous report suggested that the mechanism of osteoblast proliferation involves the extracellular signal regulated kinase signaling pathway. Other researchers speculate that the biostimulation process involves mitochondria.
Periodontitis-affected root surfaces are hypermineralized and contaminated with cytotoxic and other biologically active substances. It is not possible to decontaminate and debride such surfaces completely by mechanical means alone because hand or ultrasonic scaling of the root surface always produces a smear layer after contact with the instruments used. The first aim of periodontal treatment is removal of inflammation-causing biofilm and calculus to control the progression of disease. Because a biofilm is an ecosystem involving quorum-sensing bacteria that form a strong glycocalyx and reside in the irregularly shaped periodontal pocket, attempted elimination of biofilm-associated organisms by antibacterial therapy alone is extremely ineffective. The most effective method is physical elimination. Conventional scaling and root planning involves the use of hand instruments (scalers and curettes) to remove bacteria. Unfortunately, it is difficult to completely remove the bacteria. In contrast, laser scaling enables complete removal of the biofilm. Effective sterilization is possible during calculus removal and debridement by targeting the laser beam to the periodontal pocket. This advantage makes laser treatment ideal for initial periodontal therapy. In a previous report, we detailed the results of the first clinical study of the use of Erbium: YAG (Er:YAG) lasers for scaling. 4 We found that most of the subgingival calculus could be removed using this type of laser, and we demonstrated that the periodontal pocket depth could be reduced significantly.
Gingival hyperplasia is a potential side effect of the antihypertensive agent Nifedipine®. The use of a laser to remove gingival hyperplasia is a practical way to address the patient's aesthetic concerns. In addition, laser gingivectomy and gingivoplasty have a good prognosis and low risk of recurrence.
Lasers also present opportunities during conventional periodontal surgical procedures. Flap elevation allows more direct access to the surgical field and root surfaces. The removal of calculus using a laser is thereby rendered more effective because the target can be more easily confirmed. Removal of diseased granulation tissue using conventional handheld instruments can be very difficult. The use of a laser for its removal is more effective, requires less intraoperative time, and is less stressful for the patient. In addition, irradiating the internal aspect of the flap with the laser provides lasting disinfection, thus promoting rapid healing. Lasers are also extremely effective for osseous surgery. Mechanical instruments are very ineffective and greatly stress patients. In contrast, lasers are ideal for osseous resection and osteoplasty due to the light contact pressure required. The advantages of laser osseous surgery are not offset by any significant harm to the patient.
The favorable performance of Er:YAG laser makes it an ideal choice for use in the treatment of both hard and soft periodontal tissues. For example, we examined the effectiveness of lasers in the semilunar coronally repositioned flap (SLCRF) procedure. The SLCRF procedure is useful for covering shallow, localized recession defects and lends itself to the use of a laser. Almost all cases were Miller class I or II. The defect coverage was 0–3.5 mm (average of 1.9 mm), and the mean percentage of root coverage after surgery was 76.0%. The prognosis after laser surgery was good. These results suggest that Er:YAG lasers are effective for use in SLCRF procedures.
The prevalence of peri-implantitis is increasing and poses problems, especially for aging populations. Unfortunately, suitable treatment methods have not yet been established because it is difficult to decontaminate the complex surface structure of dental implants. It would be practical if the use of a laser in nonsurgical treatment of peri-implantitis would have a disinfecting effect, but there are insufficient data to demonstrate such an effect. 5 Nonetheless, Er:YAG lasers can be used, with surgical access, to vaporize and remove biofilm and calculus associated with a dental implant. Other advantages of using Er:YAG lasers for peri-implantitis treatment include greater accessibility to areas that cannot be reached using conventional instruments and greater ease of removal of inflamed tissue on the implant surface.
The 21st century is said to be the age of the photo sciences. Lasers are artificially oscillated electromagnetic waves that are superior to natural light in several respects important to periodontal medicine. In this editorial, the novel possibilities for the use of lasers in periodontal treatment were discussed. I would be delighted if in reading this editorial the reader gains a deeper appreciation of the potential of “laser dentistry” to contribute to improved health and quality of life.