A common refrain from the dental associations is that if mercury from amalgam is so dangerous for the patients, than why aren’t the dentists sick, as they are exposed to levels on a daily basis, far higher than most patients.  It’s an interesting proposition, which if it were true would be fair enough to ask. 

The results published by the IAOMT show that;

When cutting amalgam with a high speed drill, the levels of mercury vapour 18 inches from the mouth, can exceed 4,000mcg/m3

When the nurse opens a freshly mixed amalgam capsule the level of mercury vapour she (and the rest of the surgery) will be exposed to is 1,000 mcg/m3. This is 200 times above OSHA standards and 50,000   above the ATSDR levels.

These figures are beyond comprehension, especially when our very own trade associations claim that they are safe.  A reminder to all dentists and dental associations, in 1991 (criteria 118) the World Health Organization stated clearly that the No Observable Effects Level (NOEL) for mercury vapour is ZERO.  Why is it then that every regulatory body in this country is scared to take on the dental association and the dental boards and in fact the universities when such clear breaches of the law are flagrantly advertised?

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From 1975 till 1983 the American Dental Association conducted a survey of the dentists who participated in the Health Assessment Programs they conducted.  This study looked at urinary mercury levels of 4,272 Dentists in the USA.  They measured straight urine/mercury levels.  We could expect that if a DMPS Challenge test had been employed, the figures would be at least five times higher.

These 4,272 dentists had a mean mercury urine level of 14.2mcg/l (micrograms per litre). What was then considered to be the maximum normal level as stated by the American Dental Association was 20mcg/l.  The observed ranges of urine mercury levels was 0 to 556 mcg/l.

The study showed that;

1. 19.1% are over the maximum normal measurement of 20 ugHg/L
2. 10.9% are over the C.D.C. maximum acceptable level of 30 ugHg/L
3. 4.9% are over 50 ugHg/L, the level found to cause induced tremors
4. 1.3% are over 100 ugHg/L, the level found to cause tremors

This study was used for many years to show how well dentists were!  Note that the reference levels used were 20 micrograms of mercury per litre of urine.  The new German guidelines for urine mercury levels since 2006 have dropped significantly. The new reference level for urinary mercury is now 0.7 mcg/l.  This would suggest that dentists with a level of 20 mcg/l would show significant physical and psychological disturbances.

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A study from 2001 explored the mercury levels in dental students and dental teachers over a one year period.  This study is published in the British Dental Journal!

“There were statistically significant increases  in plasma mercury concentration between measurements in all groups at the end of the academic year. Red cell mercury levels were also consistently elevated. Although the highest levels of mercury were recorded in persons working with amalgam, increased levels were also found in subjects working in the teaching classrooms but not with amalgam (controls and first year students).”

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“Our results indicate that the urinary mercury levels of the tested dental professionals were significantly higher than those of the control group”

“This study showed that there may be a mercury health hazard in some dental environments.”

“…it is apparent that exposure to mercury during the preparation of silver amalgam definitely presents an additional occupational hazard as an allergen in the dentist.”

“The results showed that mercury levels in the urine and head hair of dental personnel were significantly higher than in the controls
The highest urine mercury level was found in the group of dental assistants.
The amounts of urine mercury from dental assistants, dentists and dental students were 81.0%, 38.2% and 43.5% higher than the threshold limit value respectively.”

“General dentists were found to have more than twice the level of mercury in toenails than non-dental health professionals  … and 60 percent higher than dental specialists …”

“Of the 298 dentists evaluated, 28% had greater than 20 micrograms/g of mercury in the head.”

“The urinary concentrations of mercury of the dentists who used amalgam in their work were statistically highly significantly   elevated.”

Another study from 1991 concluded;  “In the group of dental personnel, the effect of their own amalgam fillings on Hg concentrations....was as important as their occupational exposure to Hg”.

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The publication in 1985, of a huge study of 9,241 people has hardly raised an eyebrow.   A study of this size has great statistical significance yet has not made it into the dental association information.  This group was comprised of 3,454 male dentists,  1,125 female dentists, 4,662 female dental nurses.  It showed that the rate of a particular type of brain cancer called a Glioblastoma was twice as high in this group of dental personnel compared to the rest of the population.
 
Another study of 298 dentists revealed that 30% of the high mercury group had polyneuropathies.  No polyneuropathies were detected in the control group. 

The high mercury group had mild visuographic dysfunction; they also had more symptom-distress than did the control group.
These findings suggest that the use of mercury as a restorative material is a health risk for dentists.

A different study of 66 dentists;
“with a sample of 37 (56%), 22 dentists (59.5%, 19 male, 3 female) and 15 dental assistants (40.5%, all female).
Most frequent symptoms referred by dentists were: irritability   (54.5%), cephalalgia (45.4%), arthralgias (40.9%), and the ones more   referred by assistants were arthralgias (53.3%), irritability (46.7%)   and cephalalgia (46.7%).”

Female Dental Personnel

A study published in the Journal of the American Dental Association states that for female dental personnel;

“rates of spontaneous abortion or non-congenital abnormalities  in children during this period, were higher in respondents exposed to high levels of mercury in the dental environment than those exposed to low levels.”

In fact the rate of infertility, miscarriage, stillbirths, and congenital deformities is up to twice the rate of the rest of the population.  The incidence of menstrual problems increases with length of exposure. ,

The US Environmental Protection Agency have stated that;
“Women chronically exposed to mercury vapour experienced increased frequencies of menstrual disturbances and spontaneous abortions.”
“A high mortality rate was observed among infants born to women who displayed symptoms of mercury poisoning.”

These   findings indicate that dental work could be another occupational hazard with respect to reproductive processes.

The probability of falling pregnant at each menstrual cycle for women who prepared 30 or more amalgam fillings per week is only 63% of that for unexposed women. 

As long ago as 1981 it was shown that female dentists had a higher rate of spontaneous abortions then a control of female medical personnel or the rest of the population.  The Peri-Natal Mortality Rate for the female dentists was significantly higher than for the rest of the population 19.5 / 1000 as compared to 7.5 / 1000  - twice the rate of the controls.

Female dental personnel are perhaps the most sensitive of the dental fraternity exposed to mercury.  Many girls start a career in dental nursing in their early teens.  They continue often into their 30’s and some longer.  This is the prime reproductive age. 

Psychological Effects

Psychological studies of dentists show some really scary results.   One such by Professor Joel Butler, Professor of Psychology at the University of North Texas, and entitled “Neuropsychological Dysfunctioning Associated with the Dental Office Environment" has the following results.
Fifty-one dentists and dental personnel were studied on standardised tests, which revealed there were a significant number who measured in the abnormal range;
Some motor tremor – 90%
Some psychomotor dysfunction – 41%
Severe psychomotor dysfunction – 16%
Impaired immediate recall – 58%
Impaired auditory memory - 84%
Visual memory reduced – 52%
Vigilance attention concentration and cognitive comprehension – 52%
Work and lives felt to be pointless -36%
Tactile sensory dysfunction/inability to locate finger position – 52%
Logical thinking and story recall impaired – 79%
Spatial and visual memory impaired – 68%
History of unsatisfying interpersonal relationships – 27%
Out of normal range on emotional stability scale – 72%
Suicidal depression / disgust with life / despondency and despair – 27%
Increased state of agitation – 30%
Increased scores on psychopathic scale – 42%

This study concludes that as a group, dentists are, after a number of years, at least one standard deviation below the rest of the population in IQ levels.  Considering that a dentist must be at least one standard deviation above the rest of the population to have passed dental school, this represents an enormous and significant drop!

Another study from 1995 stated;
… analysis showed that the coefficient of urinary mercury was statistically and adversely associated with complex attention (switching task), the perceptual motor task (symbol-digit   substitution), symptoms and mood.

In the same year other research by Echeverria et al came up with a similar conclusion. “Significant urinary Hg dose-effects were found for poor mental concentration, emotional lability, somatosensory irritation, and mood   scores.”  There was Evidence of subtle pre-clinical changes in behaviour associated with Hg exposure. Urine mercury Levels Directly related to; Reduced Concentration and Emotional Instability and Fine Motor Function was seriously effected.  

New distinctions between subtle preclinical effects on symptoms, mood, motor function, and cognition were found associated with Hg body burden as compared with those associated with recent   exposure. … presents convincing new evidence of adverse behavioral effects associated with low Hg(o) exposures within the range of that received by the general population.

In neurobehavioural tests measuring motor speed (finger tapping),   visual scanning (trail making), visuomotor coordination and   concentration (digit symbol), verbal memory (digit span, logical   memory delayed recall), visual memory (visual reproduction, immediate   and delayed recall), and visuomotor coordination speed (bender-gestalt time), the performance of the dentists was significantly worse than that of the controls.
In trail making, digit span, logical memory delayed recall, visual reproduction delayed recall, and bender-gestalt time test scores were more than 10% poorer. … the performance decreased as the exposed dose increased. These results raise the question as to whether the current threshold limit value of 0.050 mg/m3 (TWA) provides adequate protection against adverse effects of mercury.

Another study was performed “to find out if the first "professional" contact of dental students with amalgam resulted in an increased mercury excretion.”
The study was conclusive.  The longer the students were exposed to mercury in the clinic, the greater was their body burden of mercury. 

The levels of Hg in the urine samples of the dentists was about three times higher than the control subjects. …

30% of the 23 high mercury dentists had polyneuropathies. No   polyneuropathies were detected in the control group. The high mercury group had mild visuographic dysfunction; they also had more symptom- distress than did the control group. These findings suggest that the use of mercury as a restorative material is a health risk for dentists.

Dentists were significantly more likely than control subjects to have had disorders of the kidney and memory disturbance.

The older dentists showed significantly better performance on the simple reaction time test and significantly poorer performance in the   immediate word recall and delayed word recall tests.

In light of new research, which shows that over time there is a reduction in kidney filtration and a reduction in urine mercury levels due to the inability to excrete, these statements become even more terrifying.

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[JADA  Vol. 122  August 1991  By Irwin Mandel DDS Assoc. Dean for Research School of Dental and Oral Surgery Colombia University New York]

[Nylander et al.Fourth international symposium Epidemiology  in Occupational Health.,Como Italy Sept 1985]