A Resurgence of Interest in Bioelectric Medicine
The use of electrical currents in medicine is not new. Records indicate that electrical stimulation was prescribed as early as 46 A.D. Patients were advised to place one foot on a species of fish that used electrical shocks as a defense mechanism, and the other foot on wet sand to complete the electrical circuit. In the 19th century, medical texts suggested a wide use for electrical medicine. By 1894, it is reported that about 10,000 physicians were using electrical therapy routinely in their practices. After the turn of the century, however, the medical profession reevaluated the situation in light of rampant charlatanism. The Carnegie Foundation established an investigative commission, and a final report was published in 1910 that almost instantaneously changed medical education. Electrotherapy was then regarded as an unsubstantiated technique and physicians avoided its use.
Over the past 30 years, new interest in the bioelectric activity of living tissues has emerged. One might say that the human body is now recognized as an organic battery and all living cells of the body as tiny bioelectric units. Research has been conducted into concepts of neurotrophism in growth and healing. Investigation has shown that when cells are subjected to electrical pulses, they can change into more primitive forms and by DNA coding produce whatever cell type is necessary for regeneration. Entire limbs have been regenerated through electrical stimulation after amputation in animals. The concept of piezoelectric bone remodeling has emerged, as well as accelerated orthodontic treatment with electrical appliances.
Currently, there is renewed interest in pain control by means of electrical stimulation. Recent demonstrations of specific opiate binding sites in the brain and spinal cord--along with the discovery of the endogenous transmitter substances, enkephalins and endorphins (which have morphine-like activity)--support the view that there is a neural system in the brain to produce pain relief. The system is apparently activated either through direct stimulation with morphine-like drugs or electrically by inducing release of the endogenous substances.
Particularly interesting to orthodontists is the increasing treatment of temporomandibular joint disorders. Electrotherapy is presently being advocated by some, and many systems are for sale in two basic forms: TENS (transcutaneous electrical nerve stimulation) and EGS (electrogalvanic stimulation).
One theory of TENS efficacy relates to endorphin release, mainly from the pituitary. Endorphin levels are reported to be low in chronic pain patients. Low-frequency current seems to stimulate endorphin release endogenously; heat, mechanical manipulation, and acupuncture are also said to cause endorphin release.
The second theory of the TENS mechanism is based on the work of Melzack and Wall. There are two basic types of afferent nerves conveying pain sensations from the receptor organ to the central nervous system. A-delta fibers convey rapid, sharp, pricking sensations; C-fibers convey slow, dull, burning ones. Both types terminate in the substantia gelatinosa in the dorsal horn of the spinal cord, ending in what Melzack and Wall called "gates". If the gates are open, pain sensations stimulate "T" cells, which send impulses up the spinothalamic tract to higher levels. A third type of fiber has been discovered--A-beta--that can close the gates. This type is stimulated by touch, massage, heat, light pressure, and low-frequency electricity. Normally the three sets of fibers are in a state of balance at a gate, and it remains open for any alarm of pain. With chronic pain an imbalance occurs, and C-fibers are in a constant state of stimulation. By activating A-beta fibers electrically, the gate can be closed and perception of pain decreased. Repeated stimulation seems to be required to restore a normal balance.
On the other hand, EGS is typically used more for direct pain control in muscle tissue. By adjusting the polarity, it is said to cause the coagulation of protein and vasoconstriction, or the liquefaction and softening of protein and vasodilation. Its primary purpose seems to be the treatment of muscle hypercontraction and trigger points.
Both techniques offer units for office use or portable ones for home treatment. The TENS units may be attached to the body and thus worn constantly.
Research in the field of electrotherapy is still limited, and generally published in journals of low circulation. Clinical information tends to be anecdotal and subjective. More research activity should clarify the nature of electrotherapy's effectiveness so that the pendulum of health care does not again swing toward charlatanism. EHW
