The word LASER is an acronym for Light Amplification by Stimulated Emission of Radiation. The original theory of laser light was postulated by Albert Einstein in 1916. Theodor Mainman produced the first working laser, a ruby laser in 1960. Dr Terry Myers introduced the Nd: YAG laser to dentistry in 1989.
HOW LASER LIGHT IS CREATED
Power is applied to a medium or a laser diode and laser light is produced which is passed through a partial reflective mirror.
Laser light is monochromatic (one wavelength) and is coherent (in order or in synchronicity). Each laser has an individual wavelength, unlike a light bulb or sunlight which has multiple wavelengths. It is this single wavelength which allows us to produce lasers which each have different treatment abilities based on their unique wavelengths.
LASERS IN DENTISTRY
There are three categories of lasers used in dentistry:
1. Soft tissue lasers: These lasers include the Nd: YAG, Argon, Diode and CO2 lasers. Each have different strengths and weaknesses, but all can perform numerous soft tissue procedures such as gingivectomy, gingivoplasty, crown and bridge troughing, sulcular debridement, frenectomies, and haemostasis. One unique feature of lasers compared to other modalities is their ability to kill bacteria and prevent their regrowth for up to three months. Furthermore, because of the way in which lasers interact with the tissues, there is less post-op swelling and pain.
2. Hard tissue lasers: The lasers in this group are ER: YAG and Er: YAGYSGG. These lasers can be used for cavity preparation (remove enamel, dentin and caries, but not amalgam), often without anaesthesia. They are also excellent for bone removal. These lasers can be used for some surgical procedures but because they do not have the ability to induce haemostasis, they are more limited than the soft tissue lasers.
3. Low level lasers: This is the third category of lasers, but unlike the two previous lasers, they have no ability to cut tissue, only to affect tissues on the cellular level. There are two wavelength ranges used; the HeNe (630-650 nm) and the Diode (790-850nm). The HeNe lasers are excellent for surface wounds but have very limited penetration. The Diode lasers are good for surface wounds, but penetrate 2-3cm and so are more effective for deep areas inside the bones, muscles and joints. This wavelength has the most applications in dentistry.
MECHANISM OF ACTION
Laboratory-based experiments on a variety of cell types in vitro have demonstrated primary and secondary responses produced when these cells are irradiated with photons. The responses include the following:
Primary responses:
* The photons are absorbed by cytochromes
* Singlet oxygen molecules (free radicals) are generated, affecting ATP synthesis (thus increasing the energy available to the cells)
* Nitric oxide is produced
* Reversible increase in cell membrane permeability to calcium and other ions occurs, triggering changes in cell activity, i.e. secondary responses
Secondary responses:
* DNA & RNA synthesis
* Cell proliferation
* Growth factor release
* Collagen synthesis by fibroblasts
* Changes in nerve conduction, neurotransmitter release, etc.
Clinical effects of treatment
The effects of lasers on tissue are commonly referred to as biostimulation, and include the following:
* Stimulates production of ATP (this is the fuel and energy store for the cells)
* Increased collagen synthesis in fibroblasts
* Increased formation of capillaries by the release of growth factors
* Increased activity of leucocytes
* Transformation of fibroblasts to myofibroblasts
* Stimulation of osteoblasts
* Stimulation of odontoblasts
* Increased lymphatic flow which leads to a reduction in edema
* Reduction of immune response (reduction in the release of histamine, bradykinins, substance P and acetylcholine)
* Reduction of depolarization of afferent C fibres (the fibres which carry pulpal pain)
* Stimulates nerve regeneration
* Stimulation of production of -endorphins (the bodies own pain-killer)
WHERE TO APPLY
With any wound the laser should be applied at the site of the wound. In teeth, the laser should be applied to the sore area but also should be applied at the apex according to the diagram below.
The ideal time to treat any injury with LLLT is at the time of injury. Laser therapy reduces the inflammatory response while still allowing for the production of essential growth factors. However, the benefits will be the greatest if the laser is applied shortly after time of injury.
ACUTE VS. CHRONIC PAIN:
* In acute pain, treatment is applied more frequently than in chronic pain
* In acute pain, the dosage can be much higher than in chronic conditions
* Acute conditions are often treated 3 to 4 times for one week
* Chronic conditions are often treated twice weekly for the first two weeks and then once a week after that
* In chronic conditions the patient may even experience a slight increase in pain the day after the first treatment and they may experience a malaise. This is largely caused by the increase in lymph flow and circulation which “empties the inflammatory products into the general circulations”
CLINICAL DENTAL APPLICATIONS
1. POST SURGICAL
Effects of using the laser:
* Reduction of post-op pain and reduced need for analgesics
* Decreased bleeding in the first half hour followed by increased circulation resulting in faster healing
* Reduced post-op edema
* Better bone formation
* Less likely to get a dry socket
2. ENDODONTICS
Effects of using the laser:
* Reduction of post-op pain and inflammation and reduced need for post-op analgesics
* Diagnosis of irreversible pulpitis: Apply laser at apex of tooth according to Figure 3. If the patient experiences pain the laser is removed and left off. It is then reapplied; if severe pain returns immediately then you are dealing with an irreversible pulpitis. If there is no pain when the laser is applied continue to desensitize as described below
* Treatment of dentin hypersensitivity
* Reduction in pulp hyperemia
3. SOFT TISSUE LESIONS
Effects of using the laser:
* Reduction in pain
* Prevention
* Faster healing
* Decreased rate of recurrence
Procedures and dosage:
* Herpetic lesion, Apthous Ulcers and Denture Sores: In very light contact or just away. It can be repeated once or twice more every other day. If a lesion can be caught at the prodromal stage one, application is using sufficient to prevent appearance of the lesion. The laser also reduces the chance of recurrence in the treated area.
* Angular Chelitis: In each comer of the mouth. The cause of the lesion must be found to prevent recurrence
* Bruising after Injection: At site of bruising
4. IMPLANTS
Effects of using the laser:
* Reduction of pain after
surgery
* Faster integration
5. DRY SOCKET
Effects of using the laser:
* Pain relief
* Faster healing
6. SINUSITIS
Effects of using the laser:
* The laser can help to drain the sinus and reduce the pain of sinusitis.
7. RESTORATIVE PROCEDURES
Effects of using the laser:
* Analgesia for small tooth preparations and crown cementations reducing use of local anesthetic in these cases Reduction of post-op sensitivity
* Faster uptake and elimination of anesthesia
* Production of secondary dentin in deep restorative situations
8. CARPAL TUNNEL SYNDROME
The laser has proven a conservative alternative to the treatment of this ailment which is becoming much more common in dentistry. The laser is applied between the spinous processes of C5 and T1 and then at the wrist. The dentist should work in consultation with a physician, physiotherapist or chiropractor. It usually takes from 10-30 sessions. Success rates of 70-80% using the laser only have been published. This is about the same success rate as is obtained with surgery but after surgery there is no follow up possible except for more surgery.
9. NERVE LESIONS
Effects of laser treatments:
* Return of sensation after traumatic damage or severing of a nerve
* Treatment of trigeminal neuralgia
10. FACIAL PAIN
Effects of laser treatments:
* Relaxation of muscle spasms
* Treatment of Trigger Points in the muscles
* Reduction of inflammation inside the joint
* Reduction of symptoms of osteoarthritis
* Treatment of chronic TMJ pain
* Treatment of Neurogenic lesions associated with facial pain
11. ACUPUNCTURE
The laser can be used very successfully on acupuncture points and the effects on healing and pain relief can be very dramatic.
ADVANTAGES OF LOW LEVEL LASER TREATMENT
The biggest advantage of laser therapy is that there are no side effects of treatment. The laser induces the bodies own natural functions so one does not see the side effects that are often seen with drug therapy. The evidence and public concern surrounding drug side effects and interactions has been in the forefront of the news lately with the controversies concerning Vioxx and Celebrex. The patient response to laser therapy is excellent making them an effective practice builder.
The only case where the laser does not work well is in a patient taking systemic corticosteroids. They suppress the laser effects so the clinical results are greatly reduced.
CONCLUSION
I have been using an Nd: YAG laser in my dental practice since 1992 and a low level laser since 1993. They have both been invaluable clinical tools. For further information on dosages and to obtain reference articles you may go to www.laserlightcanada.com. OH
Dr. Gerry Ross is a 1971 graduate from the University of Toronto. He has had numerous articles published on Air Abrasion, Caries Diagnosis and Lasers and has lectured internationally on the same subjects.
Disclaimer
Gerry Ross is president of Laser Light Canada, which sells Low Level Lasers to health professionals.
Oral Health welcomes this original article.
