Evidence that Mercury from Dental Amalgam May Have Caused Hearing Loss in Multiple Sclerosis Patients
Journal of Orthomolecular Medicine Vol. 12, No. 4, 199
RL Siblerud; E Kienholz
Seven female subjects diagnosed with multiple sclerosis were tested for hearing at threshold frequencies of 250, 500, 1000,4000 and 8000 Hz. The subjects then had their silver dental fillings (amalgams) removed. Between six and eight months after amalgam removal, testing for hearing was repeated. Six of the seven subjects showed improvement in hearing of the right ear and five of the seven showed improvement in the left ear. Four of the six frequencies tested in the right ear improved significantly and three of six improved significantly in the leftear. The total frequencies were averaged before amalgam removal and compared to after amalgam removal. Hearing improved an average of 8 dB (p=0.02).
One of the many symptoms of mercury toxicity is hearing loss.1 The silver dental filling commonly called the amalgam is composed of approximately 50% mercury.2 Studies have shown that mercury escapes from the amalgam in the form of elemental mercury vapor.3,4 A large percentage of mercury vapor can be inhaled into the lungs, where it enters the blood stream and can be transported to all parts of the body.5,6 Elemental mercury can readily cross the blood brain barrier and cause damage to the central nervous system.7
There has been evidence associating mercury from dental amalgam and multiple sclerosis (MS).8 The neurotoxic effect of mercury can produce effects similar to that found in MS. These toxic effects include demyelination of the nerve fiber7 damage to the blood brain barrier, slow nerve conduction velocity,9 and autoimmune responses.10 Epidemiological studies have correlated dental fillings to Multiple Sclerosis (MS).8
A recent study has given evidence that MS subjects with amalgam removal have significantly fewer exacerbations of symptoms, compared to a control group of MS subjects with amalgams11 who also had significantly higher total T-lymphocytes and (CD8) suppressor T-cells. In 1971-72, an outbreak of methylmercury poisoning occurred in Iraq, where hundreds of people were poisoned. Severely affected children became deaf, and many adults developed a marked hearing loss.1 Alkyl mercury can cause a sensorineural hearing loss.12
This study was undertaken to determine hearing sensitivity changes of MS subjects after the removal of silver dental fillings. Because of mercury’s known ability to damage hearing, before and after hearing tests were performed on the subjects.
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This study suggests that dental amalgam mercury may be involved in hearing loss of multiple sclerosis patients. It also raises the possibility that amalgam mercury may be an etiological factor in the hearing loss of non-MS patients.
Deafness is usually divided into two types.13 The first classification is nerve deafness which is caused by an impairment of the auditory nerve. The second classification is conduction deafness which is caused by impairment of the middle ear mechanisms for transmitting sound into the cochlea. One of the characteristics of nerve deafness is a decline in hearing for all frequencies.
The results of this study, showing an improvement in hearing ability in all frequencies after amalgam removal, suggests that there is nerve damage. Mercury can lead to nerve damage by affecting RNA protein synthesis,7 by reducing nerve conduction velocity, by demyelinating the nerve fiber, by increasing the threshold for excitation, by blockage of action potentials without changing the resting membrane potential ,7 and by affecting the neurotransmitter secretion or receptor site.14.15
All of these toxic effects could lead to hearing loss if the auditory nerve is involved. Evidence was presented that mercury from dental amalgam may be affecting hearing. Six of seven MS subjects showed improved hearing in the right ear six months after dental amalgam removal and five of seven showed improvement in the left ear. All six frequencies in the right and left ear showed an improvement for the seven subjects.
Because all frequencies showed an improvement, it was concluded that nerve damage was causing the hearing loss. With mercury’s ability to cause neurotoxic effects, the overall significant improvement in hearing may have resulted from removal of silver/mercury dental fillings.