Amalgam - Fact and fiction

Carl Molin

"If 1 want to succeed in leading a human being towards a special goal, I ftrst of all have to find her where she is, and begin from there. Those who cannot manage this, will deceive themselves when they think they can help other people. In order to help I, certainly, need to understand more than she does, but first atid foremost what she understands. If I cannot, what use is it that I know more - all true helpfulness begins with humility in relation to the one I want to help. Thence it follows that I must understand that this business of helping is not a wish to dominate but to serve. " ^ ' '" SoREN KIERKEGAARD (1813-55) Molin C. Amalgam - Fact and fiction, Scand J Dent Res 1992: 100: 66-73. A brief history of amalgam is given, stressing the role of G. V. Black. The background and the progress of the two Amalgam Wars are sketched. Aspects are presented of the drawbacks of amalgam with respect to toxic effects of, especially, mercury vapor and corrosion products. An account is given of some frequent fallacies concerning the health hazards of dental amalgam fillings and the role of psychosocial factors in the development of illness attributed to amalgam is emphasized.

To be asked to write about fiction in a journal devoted to science must, to say the least, be uncommon. The Journal concerned, however, is a remarkable one, and the saga of dental amalgam is both strange and dramatic. Noble heroes as well as vulgar villains appear and ruthless, even if not bloody, fights have been fought in at least two wars. Battle dust still obscures the view, but let me try to tell the true events and, hopefully, the facts about the fictions. Once upon a time, there was a "silver dough" invented in China. This is mentioned in a manuscript of the Tang dynasty, the "Materia Medica" by Su KuNG in the year 659 A.D. One hundred parts of mercury were mixed with 45 parts of silver and 900 parts of tin, and it is known that the alloy was used as material for filling teeth (1, 2). One milleniurn later a kind of copper amalgam was developed in Germany. A town medical officer in Ulm, IOHANNES STOCKER, or STOCKERUS, had become interested in treating decayed teeth and prepared a filling material by boiling together green vitriol and mercury. He was also the first to use the name "amalgam" (3). In the beginning ofthe 19th century the so-called d'Arcet's metal, consisting of bismuth, lead and tin, was tried for dental purposes. Melting at about 100°C, it caused both pain and damage when it was poured into a cavity (4) Louis REGNART, a member of a family of dentists dating back to the year 1000, found that the melting point could be considerably lowered if a small amount of mercury was added (5). His compatriot AUGUSTE ONESIME

Key words: dental amalgam; history: mercury , vapor; selenium psychosociai tactors ';i| Ludvigsbergsgatan 12, S-118 23 Stocktiolm, Sweden

about 1836 made a silver amalgam, "Pate d'Argent", by kneading filings of silver coins with mercury in his hand (4). . ^ TAVEAU

Fiction enters the stage

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The English chemist CHARLES BELL in 1819 invented a kind of silver amalgam. Originally it was named "Bell's putty" and later on "Mineral succedaneum", meaning "mineral substitute" (4). In the early 1830s the family CRAWCOUR, dental charlatans in London, realized the commercial potentiality. Advertising that they filled teeth with the' "Royal Mineral Succedaneum in two minutes without any pain, inconvenience or pressure" they enjoyed great economic success. The pretentious attribute "Royal" was meant to suggest a substitute for gold and to underline the fraudulent claims of the five brothers to be dentists to the courts of Austria, France, Russia and Prussia (5). But the clinical results were poor. Most of the fillings soon fell out or cracked the teeth, due to the expansion of the material, and if they did remain the teeth were decayed because neither excavation of caries nor any cavity preparation was performed. In 1833 two ofthe brothers CRAWCOUR moved to New York. There they met with hard opposition from the established dentists. Skilled in the use of cohesive gold the American dentists felt threatened by the competition from the users of an inferior but cheaper material. Making use of amalgam became stamped as synonymous with quackery, and a professional association, the American Society of Den-

Amalgam - Fact and fiction tal Surgeons, was founded in 1840 to counteract it. To be accepted as a member the dentist had to sign a statement that he did not use amalgam (6).

The First Amalgam War Quite a few dentists, however, believed in the possibilities of the new material. Many patients could not afford the expensive gold fillings or endure the great pain the gold mallet caused. Thus, the opinion of the profession became so seriously divided that it gave rise to what has been called the Amalgam War. Considering what is now going on, "The First" would be an appropriate addition. As in all controversies concerning faith the combatants stopped at nothing. The attacks were chiefly directed against mercury, which was accused of being the cause of almost every imaginable trouble. A fact that may have facilitated the blackening of mercury was that it had already acquired a bad reputation for its side effects in the treatment of the dreaded and not too uncommon malady of syphilis. Appalling case histories were published even as editorials in the leading professional journals such as the DENTAL COSMOS (7). A standardbearer wrote: "The matter which I wished to bring to the notice of the profession is the poisoning of thousands of people all over the world from corrosive sublimate generated in the mouth from amalgam plugs in the teeth. Neither Asiatic cholera, nor smallpox, nor any malarious disease, is half the mischief ... that is done by this poisoning ... a person poisoned in this way is hable to be treated for dyspepsia, neuralgia, paralysis, consumption, and numerous throat diseases" (8).

The Amalgam War delayed development of better amalgams Amalgam at that time, surely, was a very inferior product. Every dentist made his own alloy, usually by filing Spanish or Mexican silver coins. The most deleterious effect of the Amalgam War was that it delayed the development and acceptance of better compositions. Not until the late 1870s, when the most militant of the amalgam resisters had gone, were those who believed in the possibilities of amalgam able to join forces in an organization named the "New Departure". The leader was J. FOSTER FLAGG who experimented seriously and developed better amalgam formulas. The connecting idea behind the movement, however, was an electrochemical decay theory that blamed gold and increased the interest in the plastic filling materials (9).

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G. V. Black makes amalgam acceptable

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The decisive contribution, however, as in so many other dental domains, was made by GREENE VARDIMAN BLACK. His studies of the topography of the carious lesions had resulted in his epoch-making rules for cavity preparation that were based on the principle of "extension for prevention". This meant larger cavities which, in turn, required filling material with greater edge strength. As a consequence BLACK initiated research to develop better amalgams. It is typical for his systematic, scientific disposition that he began by studying how much force the masticatory muscles could exert. For that purpose BLACK constructed what he called a "gnathodynamometer", and then continued with studying the stress of mastication while chewing foods such as bread, steak and various vegetables. For ascertaining the volume changes ofthe amalgams during the setting, he also constructed a micrometer (10). From 1881 through 1908 BLACK worked with the obstinate amalgams and met with numerous disappointments and set-backs. In a letter dated 1895 to a close friend BLACK gave vent to his feelings: "I'll have to blow off or I'll bust. Of all the pure and unadultered cussed things this amalgam business is the cussedest of the cussed and merits all the cusses concentrated and boiled down that ever a Pope stuck into a Bull of Excommunication" (11). The following year, 1896, however. BLACK succeeded in developing a formula and a method of preparing an alloy that gave amalgam that neither expanded nor contracted and had strength enough to withstand the masticatory forces. Not until the early 1980s when the non-yj-amalgam was developed was there any significant change to BLACK'S formula. It is typical of BLACK'S idealistic character that he withstood all offers of commercialization and gave his achievements free to his colleagues and to manufacturers. Dentists began using his alloy but after some time complaints were reported that the alloys while fresh worked perfectly but after storing for some time behaved irregularly and resulted in unsatisfactory fillings. BLACK was puzzled but searched for a solution to the problem. One day he accidentally stumbled on a clue. His laboratory was stove-heated and near the very hot stove BLACK had stored glass bottles containing samples of "wild" amalgam. When BLACK tested specimens made of the heated alloys, he found that they were as good as those made from fresh alloys. Encouraged he continued his work along this line and eventually was able to give directions for a method of heating, or, as it is usually called, annealing

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alloys to make them remain stable for long periods of time (12). The victory of amalgam

At first it was argued that amalgam was used only by dentists who were not skilful enough to make good gold fillings. This argument, however, did not hold true when men as BLACK and G. A. BONWILL, inventor not only of the first scientifically constructed articulator but also of the electric gold mallet, declared that they too used amalgam. A European contemporary of BLACK'S, and in many respects his equal, was the German ADOLPH WiTZEL, who especially studied the corrosion of amalgam and its role in discoloration of the hard dental tissues. It is noteworthy that he enrolled both a chemist and a physicist in his studies, and thus was the pioneer of teamwork in dental research (13). As a result of their and many other dedicated researchers work amalgam improved more and more, and became adopted all over the world, especially in dentistry for children and in social praxis. The Second Amalgam War

In 1926, however, a first disquieting sign appeared. The German chemist ALFRED STOCK wrote an article, "Die Gefahrlichkeit des Quecksilberdampfes und der Amalgame" ("The danger of mercury vapor and amalgams") (14). It was followed by several others, and caused vehement discussions not only among dentists but also, and foremost, among alarmed laymen, especially in Germany but also in the US. The fear of and fight against amalgam, however, did not break out in full until the 1970s. Unfounded claims were then, as in the first amalgam war, and probably with the best intentions, used to scare people to refuse to accept amalgam fillings. When the alarming notion reached Sweden it found a fertile breeding ground. At first, however, the mercury itself did not provoke concern. Instead the galvanic currents produced by different metals in the oral environment were considered dangerous (15). Hence, the complaint was named "oral galvanism". Electric current magnitudes obtained by unreliable measurements were compared and symptoms, one hundred in all, were communicated at local meetings of the recently founded Association of Patients Damaged by Dental Treatment (APDT). As always, when it is a question of psychogenically contagious illnesses (16), the mass media played an active role by paying great atten-

tion to celebrities who claimed that their careers had suffered as the result of oral galvanism (17). For two decades the war against amalgam has been fought on several fronts and with various means. As soon as a theory or an argument has been refuted a new one has been brought forward to explain the torments the patients experience and ascribe to amalgam. For a review see MOLIN (17). Toxicologic aspects of mercury exposure

When toxicologic matters are debated, the fact that Paracelsus stated must always be borne in mind: "All matters are poison and nothing is without poison, only the dose determines if a matter is no poison". Even the air we inhale contains mercury vapor as 2700-6000 tons of mercury are (and have always been) supplied from the earth's crust, from volcanoes, and from natural bodies of water (18). From a toxicologic point of view mercury and its compounds may be divided into three separate categories: elemental mercury vapor, inorganic mercury salts, and organic mercury compounds. While the first two categories are relevant to dental amalgam, the third probably is not. To take the categories in reverse order, the extremely toxic methyl mercury can be formed by bacteria both outside and inside the human body. The capacity of ora] bacteria to produce this compound has been demonstrated in vitro but to date not in vivo (19). Consequences of amalgam corrosion

The inorganic mercury salts that are the result of corrosion, together with other salts deriving from amalgam and other metallic dental materials, were some years ago put forward by the advocates of the so-called "metal syndrome". Since then investigations have demonstrated that the concentrations of silver-, copper-, tin-, mercury-, and zinc-ions in saliva are the same in patients with self-diagnosed oral galvanism as in healthy controls (20). Moreover, several studies have failed to show any clear relationship between ascribed symptoms and corrosion (21-25). )^ In local tissue reactions, however, especially oral lichen planus (OLP), corrosion products from amalgam fillings, e.g. mercury, may be a contributory factor. Thus, FINNE et al. (26) in a study of 29 OLP patients found positive patch test reaction to mercury in 18 subjects (62%). A similar delayed hypersensitivity to mercury was found in 3.2% of eczema patients at the same hospital (26). LUNDSTROM (27) found allergic reactions (patch test) to substances used in dental restorations in 39% of her 48 OLP patients. Most commonly noted, 26%,

Amalgam - Fact and was reaction to mercury. Fillings showed signs of corrosion in 72% of the patients against 28% of her 40 controls. A lower than normal secretion rate of unstimulated saliva was found in 87% of the patients, and may give higher metal concentrations in the mucosa. In LUNDSTROM'S as in most other studies, replacement of amalgam fillings with other materials mostly resulted in total or pronounced improvement (27-29). This was also the case in a recent study of 24 patients with OLP and as many with burning mouth syndrome (BMS). While 1/3 ofthe OLP patients reacted positively to epicutaneous patch test for mercury, none of the BMS ones did. Nor did removal of restorations result in fewer BMS symptoms (30). Corrosion may not be a totally negative factor. By covering the amalgam surface with a relatively protective layer of oxides and/or sulfides as well as organic components from saliva, it also reduces the emission of mercury vapor that is the last, and presently most discussed, category of mercury dangers (31). In this respect, certainly, saliva per se is also a protective factor (32). Mercury vapor from amalgam fillings

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For a long time it has been known that mercury is released when amalgam fillings are inserted or removed (33). Yet, until rather recently, not even dentists have been aware of the fact that mercury also evaporates from amalgam as vapor during the whole functional life ofthe restoration (14, 34-36). However, both the amount and the significance of this release are still controversial. VIMY & LORSCHEIDER (37) estimated a daily dose of about 30'jig for subjects with >12 occlusal amalgam surfaces. More recent studies claim this value to be highly exaggerated (38, 39). Thus, BERGLUND (40) gives a corresponding amount of 1.7 |ig. This is about 1% ofthe dose obtained from a threshold limit value (TLV) of 50 |ig/m-\ TLV is the concentration of a substance in the air that workers for long periods can be exposed to during normal working weeks without adverse health effects. Although it is a fact that the mercury content in blood, plasma, and urine as well as in certain organs, especially in the kidneys, the brain, the pituitary and thymus glands increases with increasing number of amalgam surfaces (21, 41^3), no impairment of organ function has so far been demonstrated (44, 45). Even the highest established mercury values in human organs, especially the brain, are only about one hundredth of what has been found in symptom-free individuals with occupational exposure to mercury and one thousandth of amounts found in the victims of the Minimata disease in Japan (43, 44).

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Selenium and mercury from amalgam

Based on a methodologically unsatisfactory study (46) Swedish mass media has claimed that amalgam might also be harmful by consuming the body's supply of selenium. Since selenium is considered to play an important role in the mechanisms that limit harmful side-effects of free radicals, the organism would in that case be more vulnerable. However, the results in the above mentioned studies by MARGARETA MOLIN (45) indicate that the selenium status is not infiuenced by mercury release from dental amalgam. Nor did the analyses reveal any effects of such release on blood cells and erythrocyte components, electrolyte balance, infiammatory activity, immune stimulation, tissue damage or liver function. Furthennore, in two studies of self-diagnosed oral galvanists no deviating values of selenium or substances depending on selenium were found in the analyses of blood (47, 48). Studies of personnel occupationally exposed to mercury vapors

Some studies of personnel occupationally exposed to mercury vapors are of interest. High mercury values have been demonstrated in both the pituitary glands and the thyroid in autopsy specimens from such individuals (49). Hence, LANGWORTH et al. (50) compared basal pituitary hormone concentrations in serum as well as the response to thyrotrophin releasing hormone (TRH) in a group of dental personnel with those in an unexposed control group. No significant group differences were found. Similar results were obtained in a study of chloralkali workers by ERFURTH et al. (51). In an investigation of dentists by SHAPIRO et al. (52), the group with the highest mercury level showed a somewhat slowed motor nerve conduction in the forearm in comparison with controls with low values. In the high level group were 5 with carpal tunnel syndrome, a condition that is not uncommon in persons performing manual work. None ofthe 298 participants showed intellectual impairment, and all of them were performing their professional tasks adequately. A conspicuously high incidence of brain tumors (glioma) in dental personnel (53) was not verified in a study using an extended material (54). Nor did an epidemiologic study that examined mortality patterns of factory workers who had been heavily exposed to mercury vapor (many of them to >0.10 mg/m^) reveal any relation to diseases usually associated with mercury concentration (CNS, liver, kidneys and lungs), when compared to controls (55). Furthermore, a study on the health

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and quality of life of dentists indicates that they are healthier than the general population and many other professionals (56). Immunologic aspects Allergic reactions may be caused by minute amounts of trigger substances when sensitivity has been developed. In most cases the probable causes ofthe primary sensitization arc mercury-containing medicaments, cosmetics or food. The risk of being sensitized by mercury from amalgam fillings seems to be minute, since only 41 cases have been reported up to 1986 (57). Professional handling of amalgam increases the risk of developing mercury hypersensitivity as can be seen in a study of dental students (58). Theories have been launched that special immune or autoimmune disturbances may be developed by mercury released from amalgam (59). In the mass media these theories have been given great attention. Thus, it has recently been claimed in the largest daily newspaper of Sweden that mercury from amalgam is the causative factor in such diseases as multiple sclerosis, myasthenia gravis, rheumatism and asthma where immunologic factors are involved. Concerning primary fibromyalgia, the only effective treatment is stated to be removal, "sanitation", of amalgam (60). In this context should be pointed out the capacity of psychologic factors, especially various forms of stress, to exert infiuence on immunologic factors (61). Hence, the mercury scare may be more potent than mercury per se. So far no conclusive study has been produced that strengthens the theory of mercury as an etiologic factor in the mentioned immune or autoimmune diseases. For instance, in an investigation from Norway of 73 children, 12 yr old, no relation was found between the content of mercury in urine and the frequency of allergies or school absenteeism (62). In a Swedish study of 348 pupils, 13-15 yr old, there was no tendency towards lower prevalence of allergic diseases among the 44%) without amalgam fillings. On the contrary, there were more cases of asthma in this group (63).

Reproductive-toxicologic aspects Some authors have stated that mercury in connection with dental amalgam has deleterious effects on reproduction. Thus, in a report from Poland (64) a significant association has been claimed between total mercury concentration in the hair of female dental personnel and records of their reproductive failures. The fact that five out of six mal-

formed children comprised in the study had spina bifida has caused concern among dental personnel. The general scientific standard of this paper, however, is such that no conclusive inferences can be drawn from the material presented (65). Other surveys of pregnancy outcomes in female dentists, dental nurses and dental technicians in the United States (66), and Denmark (67) have not revealed any increase in spontaneous abortion rate or frequency of malformed children. In a Swedish study including more than 8000 pregnancy outcomes with respect to malformations, low birth weight and perinatal survival the only deviant finding was a lower perinatal death rate for the offspring of the female dental personnel in comparison with that of the total births (68). Epidemiologic studies To date, no conclusive evidence has been produced to substantiate the claims that dental amalgam should constitute any health hazards in individuals that are not allergic to mercury. On the contrary, there is a weak, even if not statistically significant, tendency in some recent Swedish epidemiologic studies that individuals with many fillings have fewer symptoms and a decreased risk of cardiovascular disease, stroke, diabetes and early death (69-71). This, of course, is not an effect of amalgam but, probably, of social and psychosocial conditions. Psychosocial factors While the First Amalgam War had the character of a civil war fought within the dental profession, the second war against amalgam, still in progress, is a popular rising. In this respect it has much in common with other popular movements, especially with environmental ones, but also with alternative health movements and exotic and zealous communions. Those taking part in the actions, the alleged victims of the illness, mostly have a background of psychosocial distress, difficult and uncertain conditions, often from early childhood, which ci^eate a need to find some external cause of one's afflictions. The fact that in most cases no physical explanation can be found makes the situation of the sufferer almost unbearable. In our Western societies people who complain of disorders without demonstrable pathology are at risk of being labeled as hypochondriacs or, often felt as even more offending, as psychosomatically ill. Any intimidation of a psychic iDackground is regarded as an insult and is strongly repudiated.

Amalgam - Fact and fiction Towards a holistic view

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To understand the various disorders attributed to factors in our external or internal environment, e.g. to amalgam, it is not enough to look at the different symptoms separately. It is imperative to see them in a wider context. As a paradigm can serve the classical "cultural" disease, neurasthenia (72). In spite of the wide range of symptoms displayed there is a uniting factor: all of them are somatic ones; they are physical but with a possible psychic background. This is the common denominator ofthe group of illnesses that is called somatizing disorders. The definition of somatization is a tendency to experience and communicate psychologic distress in the form of physical symptoms, and to seek medical help for them (73). Additional traits are reluctance to admit psychosocial stress, and an inclination to attribute the symptoms to the current most fashionable explanation of society or medicine (74). The diagnosis becomes the patient's most indispensable possession because it helps him to maintain both his selfrespect and his social standing. Hence, the ground may be prepared for conflicting opinions between him and his doctor concerning the attribution of the disorder (75). In the last few decades somatization has attracted increasing interest, in part due to the appearance of several new affiictions, often appearing epidemically (16). Depending on the special psychosocial conditions/settings of the various countries, the same symptoms recur in new constellations and with names that fire the imagination, e.g. myalgic encephalitis in Great Britain, repetitive strain injury in Australia, chronic fatigue syndrome in the US and oral galvanism in Sweden. The patient's symptoms are real, his explanations unrealistic In this context, it is mandatory to stress that the symptoms are not imaginary; they are as real as if they were caused by extrinsic factors. The mechanism of origin is the same that is active in the phenomenons of placebo and nocebo, i.e. the wellknown Pavlovian conditioned reflexes (16, 76). Feelings of strong expectation trigger physiologic reactions in various systems that produce the expected symptoms. This model also explains the important part that the mass media play in spreading these epidemics. Explanations based on external etiologic factors, e.g. amalgam, become very attractive, not least for the many OG patients demonstrating alexithymic features. This means that they cannot express feelings verbally (77). Hence, they refuse, often

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brusquely, to discuss any emotional factors, but instead can talk unlimitedly about their symptoms (78, 79). In this respect, as in many others, they have much in common with chronic non-malignant pain patients. Experience from treatment of these patient categories shows that cognitive factors are crucial for whether the patient will become an invalid or not. Relief cannot be expected if the patient is incapable of understanding that the cause, in the advanced stages, is mostly within himself He must also give up his hunt for physical treatment, e.g. surgery (80, 81). This approach might also apply to the present category of patients, oral galvanists. The general clinical experience is that these patients more than anything else shun everything beginning with "psych". This is confirmed in a Finnish study (82) where 15 OG patients were compared with a matched group of outpatients with diagnosed neurosis. The only major differences were the refusal of the OGs to consider themselves to have any psychologic problems and their high incidence of somatic symptoms. Although the majority had a history of matiy unsuccessful dental treatments, they were not willing to participate in psychiatric therapy even though most of them were considered candidates. Nor can psychiatry take care of all these distressed individuals; it must be the responsibility of the physician or dentist they seek. Experience from follow-up studies shows that the single most important factor is attention (25, 48, 83). No extraordinary qualities are required for this. Merely, besides being physicians or dentists we must also try to be human beings. . : ; Concluding remarks The general conclusion of this review is that dental amalgam does not constitute any health hazards in individuals who are not allergic to mercury. Hence, the fictions should be more feared than the facts since the threat of "mental" mercury most likely is a more dangerous menace to the health than metal mercury. The best prospect is that increasing and widespread knowledge will lend a more balanced view on these problems. The irrational notions may then fade away, as in the saga, the trolls perish when the sun rises. Then, perhaps, we and amalgam can live happily, if not ever after at least until Dental Research, maybe Scandinavian, has succeeded in developing the ideal dental filling material. References 1. CHU HSI-TAO. The use of amalgam as filling material in dentistry in ancient China. Chin Med J 1958; 76: 553-5.

Molin 2. DEMAAR F E R . Historically, when and by whom was silver amalgam introduced - Part II. ICD, Sc Bull 1973; 6: 59-64. 3. RiETHE P. Amalgamfullung Anno Domini 1528. Dt.tch ZahnaertzlZ 1980; 21: 301-7. 4. CHARLES AD. The story of dental amalgam. Bull Hist Dent 1982; 30: 2-6. 5. DEMAAR FER. Historically, when and by whom was silver amalgam introduced? ICD, Sc Bull 1972; 5: 23-6. 6. MCCLUGGAGE RW. A History of the American Dental Association. (Ch'.V, The Amalgam War). Chicago: Amer-' ican Dental Association, 1959. 7. WHITE JD. Amalgam. Dent Cosmos 1863; 4: 312-3. 8. PAYNE J. Poisoning from corrosive sublimate generated in the mouth from amalgam plugs in the teeth. Dent Cosmos ' 1874; 16: 213-4. 9. FLAGG JF. The amalgam question. Dent Cosmos 1882; 24: 237-42, 313-8,429-35.

BAOMS, SFOMK, SOF Joint Meeting, Tylosand 1987. Abstract. 30. SKOGLUND A, EGELRUD T. Hypersensitivity reactions to

dental materials in patients with lichenoid mucosal lesions and in patients with burning mouth syndrome. Scand J Dem Res 1991; 99: 320-8. 31. MEINERS H . Elektrische Erscheinungen an metallischen Fullungen. Zahnaerztl Welt 1984; 93: 3 8 ^ . 32. OLSON S, BERGLUND A, POHL L , BERGMAN M . Model of

mercury transport from amalgam restorations in the orai cavity. J Dent Res 1989; 68: 504-8. 33. FRYKHOLM K O . Mercury from dental amalgam. Its toxic and allergic effects and some comments on occupational hygiene. Acta Odontol Scand 1957; 22: 1-108. 34. GAY DD, Cox RD, REINHARDT JW. Chewing releases mercury from fillings. Lancet 1979; 2: 985-6. 35. SVARE CW, PETERSON LC, REINHARDT JW, et al. The effects

10. CANNON MS, RAPES ED, PALKUTI GA. Dr. Black and the

"Amalgam Question". J Hist Med Allied Sciences 1985; 40: 309-26.

36.

11. BLACK GV. Letter to Dr. CN JOHNSON. May 10th 1895.

Quoted in Ref 10. 12. BLACK GV. Annealing amalgam. Dent Hints 1901; 3: 115 (only). 13. WiTZEL A. Das Fallen der Zahne mit Amalgam. Berlin 1899. 14. STOCK A. Die Gefahrlichkeit des Quecksilberdampfes und der Amalgame. Med Klin 1926; 22: 1209-12, 1250-2. 15. NILNER K . Studies of electrochemical action in the orai cavity. Thesis Swed Dent / 1981, Suppl 9. 16. MOLIN C, NILSSON CG. Psykogent smittsamma sjukdomar - Nagra exempel och en forklaringsmodell. Laekartidning' e/1 1990; 87: 2510-1. 17. MOLIN C . Oral galvanism in Sweden. JADA 1990; 121: 281-4. 18. Environmental Health Criteria 118. Inorganic Mercury. World Health Organization. Geneva, 1991, p. 15. 19. HEINTZE

U , EDWARDSSON

S, DERAND T, BIRKHED T.

Methylation of mercury from dental amalgam and mercuric chloride by oral streptococci in vitro. Scand J Dent Res 1983; 91: 150-2. 20. NILNER K , GLANTZ P-O. The prevalence of copper-,

silver-, tin, mercury and zinc-ions in human saliva. Swed Dent J 1982; 6: 71-7. 21. ABRAHAM JE, SVARE CW, FRANK CW. The effect ofdental

amalgam restorations on blood mercury levels. J Dent Res 1984; 63: 71-3. 22. ELEY B M , COX SW. Mercury from dental amalgam fillings in patients. Br Dent J 1987; 163: 221-6. 23. MAXKORS R, MEINERS H , VOS. D. Zur galvanischen Korro-

sion von Amalgamen. Dtsch Zahnaerztl Z 1985; 40: 1137-40. 24. JOHANSSON B, STENMAN E, BERGMAN M . Clinical study of

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patients referred for investigation regarding so-called oral galvanism. Scand J Dent Res 1984; 22: 469-75. 25. YONTCHEV EA. Studies of individuals with orofacial discomfort complaints. An investigation of a group of patients who related their suffering to effects of dental materials and constructions. Thesis, Swed Dent J 1986, Suppl 38. 26. FrNNE K, GORANSSON K, WINCKLER L. Oral lichen planus and contact allergy to mercury. Int J Oral Surg 1982; 11: 236-9. 27. LUNDSTROM IMC. Allergy and corrosion of dental materials in patients with oral lichen planus. Int J Oral Surg 1984; 13: 16-24. 28. BoLEwsKA J, HANSEN HJ, HOLMSTRUP P, PINDBORG JJ,

STANGERUP M . Oral mucosal lesions related to silver amalgam restorations. Ota/ Surg Oral Med Oral Pathol 1990; 70: 55-8. 29. LUNDSTROM IMC. Oral lichen planus - effect of treatment.

37. 38. 39. 40.

of dental amalgams on mercury levels in expired air. J Dettl Res 1981:60: 1668-71. VIMY MJ, LORSCHEIDER FL. Intra-oral air mercury release from dental amalgam. J Dent Res 1985; 64: 1069-71. VIMY MJ, LORSCHEIDER FL. Serial measurements of intraoral air mercury: Estimation of daily dose from dental amalgam. J Dent Res 1985; 64: 1073-85. OLSSON S, BERGMAN M . Letter to the Editor. J Dent Res 1987; 66: 1288-9. MACKERT J R JR. Factors affecting estimation of mercury exposure from measurements of mercury vapor levels in intraoral and expired air. / Dent Res 1987; 66: 1775-80. BERGLUND A. Estimation by a 24-hour study of the daily dose of intra-oral mercury vapor inhaled after release from dental amalgam. J Dent Res 1990; 69: 1646-51.

41. LANGWORTH S, ELINDER C-G, AKESSON A. Mercury ex-

posure from dental fillings: I. Mercury concentrations in blood and urine. Swed Detit J 1988; 12: 69-70. 42. NYLANDER M , FRIBERG L, LIND B. Mercury concentrations

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Additional reading BoLEWSKA J, HOLMSTRUP P, MOLLER-MADSEN B , KENRAD B ,

DANSCHER G . Amalgam associated mercury accumulations in normal oral mucosa, oral mucosal lesions of lichen planus and contact lesions associated with amalgam. J Oral Pathol Med 1990; 19: 39^2. :,.- :..,..:, ,,,.,,,,.|.;.:„.,.;.,.,,.j.. r jHOLMSTRUP P. Reactions of the oral mueosa related to silver amalgam: a review. J Oral Pathol Med 1991; 20: 1-7. HORSTED-BINDSLEV P, MAGOS L , HOLMSTRUP P, ARENHOLT-

BiNDSLEV D. Dental amalgam - A health hazard? Copenhagen: Munksgaard. 1991. . ^ _ __ . _

Amalgam--fact and fiction.

A brief history of amalgam is given, stressing the role of G. V. Black. The background and the progress of the two Amalgam Wars are sketched. Aspects ...
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