Amalgama dentale tossica o non tossica. Il punto dalla letteratura scientifica

Dopo il servizio de Le Iene di ieri sera (Domenica 18 dicembre) è ripartito il dibattito sulla pericolosità o meno del materiale.

Da tempo la comunità scientifica evidenza come non ci sia univoca certezza sulla pericolosità o meno del materiale mentre sono ampiamente appurati i danni che possono provocare i fumi derivanti dalla eliminazione di una otturazione in amalgama, soprattutto per dentista ed assistente prima che del paziente, se non viene seguito un protocollo operativo definito e utilizzati strumenti di protezione idonei.

Grazie al prof Massimo Gagliani (nella foto), Direttore Scientifico dell'Area Odontoiatrica di EDRA, abbiamo cercato di fare una analisi dal punto di vista dei lavori scientifici pubblicati.

"Il problema dell'amalgama dentale -spiega il prof. Gagliani- rimane vivo sebbene in Italia il consumo di amalgama si sia drasticamente ridotto. Ci sono alimenti, come il pesce, e o prodotti per la cura del corpo che rilasciano dosi di mercurio ben piu consistenti di quelli rilasciate da una otturazione in amalgama dentale, inoltre gli amalgama dentali di ultima generazione hanno un contenuto di Hg molto basso e quindi facilmente neutralizzabile. Certamente, come evidenziato anche nel servizio de Le Iene ma indicato dalla comunità scientifica da oltre 20 anni, le modalità di rimozione dovrebbero essere fatte sempre con la diga di gomma e l'aspirazione ad alta velocità. In tema di lavori scientifici, sebbene si siano riscontrati in studi autoptici maggiori accumuli di mercurio a livello cerebrale in soggetti con molti amalgama non è stato possibile stabilire una correlazione causa effetto per questi pazienti, ovvero patologie ad esse correlate. Togliere le otturazioni in amalgama, solo in soggetti con particolare sensibilità (esempio pazienti affetti da lichen delle mucose orali), può avere vantaggi ma non sono documentati (se non in scritti scandalistici) veri miglioramenti di patologie neurologiche attribuite allo amalgama dentale.
Le raccomandazioni ministeriali, ma anche quelle della comunità scientifica, prevedono di non impiegare amalgama in donne in gravidanza e nei bambini".

Di seguito alcuni lavori scientifici indicati come significativi sul tema:

1) J Occup Med Toxicol. 2011 Jan 13;6(1):2. doi: 10.1186/1745-6673-6-2.

Is dental amalgam safe for humans? The opinion of the scientific committee of the European Commission.

Mutter J 1.

Abstract

It was claimed by the Scientific Committee on Emerging and Newly Identified Health Risks (SCENIHR)) in a report to the EU-Commission that "....no risks of adverse systemic effects exist and the current use of dental amalgam does not pose a risk of systemic disease..." [1, available from: http://ec.europa.eu/health/ ph_risk/committees/04_scenihr/docs/scenihr_o_016.pdf ]. SCENIHR disregarded the toxicology of mercury and did not include most important scientific studies in their review. But the real scientific data show that:
(a) Dental amalgam is by far the main source of human total mercury body burden. This is proven by autopsy studies which found 2-12 times more mercury in body tissues of individuals with dental amalgam. Autopsy studies are the most valuable and most important studies for examining the amalgam-caused mercury body burden.
(b) These autopsy studies have shown consistently that many individuals with amalgam have toxic levels of mercury in their brains or kidneys.
(c) There is no correlation between mercury levels in blood or urine, and the levels in body tissues or the severity of clinical symptoms. SCENIHR only relied on levels in urine or blood.
(d) The half-life of mercury in the brain can last from several years to decades, thus mercury accumulates over time of amalgam exposure in body tissues to toxic levels. However, SCENIHR state that the half-life of mercury in the body is only "20-90 days".(e) Mercury vapor is about ten times more toxic than lead on human neurons and with synergistic toxicity to other metals.(f) Most studies cited by SCENIHR which conclude that amalgam fillings are safe have severe methodical flaws.

2) Environ Health. 2014 Nov 18;13:95. doi: 10.1186/1476-069X-13-95.

Longitudinal analysis of the association between removal of dental amalgam, urine mercury and 14 self- eported health symptoms.

Zwicker JD 1, Dutton DJ, Emery JC.

Abstract

BACKGROUND: Mercury vapor poses a known health risk with no clearly established safe level of exposure. Consequently there is debate over whether the level of prolonged exposure to mercury vapor from dental amalgam fillings, combining approximately 50% mercury with other metals, is sufficiently high to represent a risk to health. The objective of our study is to determine if mercury exposure from amalgam fillings is associated with risk of adverse health effects.

METHODS: In a large longitudinal non-blind sample of participants from a preventative health program in Calgary, Canada we compared number of amalgam fillings, urine mercury measures and changes in 14 self-reported health symptoms, proposed to be mercury dependent sub-clinical measures of mental and physical health. The likelihood of change over one year in a sample of persons who had their fillings removed was compared to a sample of persons who had not had their fillings removed. We use non-parametric statistical tests to determine if differences in urine mercury were statistically significant between sample groups. Logistic regression models were used to estimate the likelihood of observing symptom improvement or worsening in the sample groups.

RESULTS: At baseline, individuals with dental amalgam fillings have double the measured urine mercury compared to a control group of persons who have never had amalgam fillings. Removal of amalgam fillings decreases measured urine mercury to levels in persons without amalgam fillings. Although urine mercury levels in our sample are considered by Health Canada to be too low to pose health risks, removal of amalgam fillings reduced the likelihood of self-reported symptom deterioration and increased the likelihood of symptom improvement in comparison to people who retained their amalgam fillings.

CONCLUSIONS: Our findings suggest that mercury exposure from amalgam fillings adversely impact health and therefore are a health risk. The use of safer alternative materials for dental fillings should be encouraged to avoid the increased risk of health deterioration associated with unnecessary exposure to mercury.

3) Aust Dent J. 2000 Dec;45(4):224-34.

Dental amalgam and mercury in dentistry.

Spencer AJ 1.

Abstract

Mercury in dentistry has re-emerged as a contentious issue in public health, predominantly because so many people are inadvertently exposed to mercury in order to obtain the benefits of dental amalgam fillings, and the risks remain difficult to interpret. This commentary aims to examine the issues involved in public policy assessment of the continued use of dental amalgam in dentistry. More than 30 per cent of Australian adults are concerned about mercury from dental amalgam fillings but only a small percentage report having their amalgam fillings removed. The placement of dental fillings nearly halved between 1983 and 1997, but many millions of dental amalgam fillings exist in the Australian community. These fillings release mercury (mercury vapour or inorganic ions) at a low level (about 2-5 micrograms/day in an adult). Evidence on the health effect of dental amalgams comes from studies of the association between their presence and signs or symptoms of adverse effects or health changes after removal of dental amalgam fillings. More formal risk assessment studies focus on occupational exposure to mercury and health effects. Numerous methodological issues make their interpretation difficult but new research will continue to challenge policymakers. Policy will also reflect prudent and cautious approaches, encouraging minimization of exposure to mercury in potentially more sensitive population groups. Wider environmental concerns and decreasing tolerance of exposure to other mercury compounds (for example, methylmercury in seafoods) will ensure the use of mercury in dentistry remains an issue, necessitating dentists keep their patients informed of health risks and respect their choices.

4) J Air Waste Manag Assoc. 2016 Nov;66(11):1077-1083.

Mercury in dental amalgam: Are our health care workers at risk?

Sahani M 1, Sulaiman NS 2, Tan BS 3, Yahya NA 1, Anual ZF 1, Mahiyuddin WR 2, Khan MF 4,

Muttalib KA 5.

Abstract

Dental amalgam in fillings exposes workers to mercury. The exposure to mercury was investigated among 1871 dental health care workers. The aim of the study was to evaluate the risk of mercury exposure among dental compared to nondental health care workers and to determine other risk factors for mercury exposure. Respondents answered questionnaires to obtain demographic, personal, professional, and workplace information and were examined for their own amalgam fillings. Chronic mercury exposure was assessed through urinary mercury levels. In total, 1409 dental and 462 nondental health care workers participated in the study. Median urine mercury levels for dental and nondental health care workers were 2.75 ¦Ìg/L (interquartile range [IQR] = 3.0175) and 2.66 ¦Ìg/L (IQR = 3.04) respectively. For mercury exposure, there were no significant risk factor found among the workers involved within the dental care. The Mann- Whitney test showed that urine mercury levels were significantly different between respondents who eat seafood more than 5 times per week compared to those who eat it less frequently or not at all (p = 0.003). The urinary mercury levels indicated significant difference between dental workers in their practice using squeeze cloths (Mann-Whitney test, p = 0.03). Multiple logistic regression showed that only the usage of cosmetic products that might contain mercury was found to be significantly associated with the urinary mercury levels (odds ratio [OR] = 15.237; CI: 3.612-64.276). Therefore, mean urinary mercury levels of health care workers were low. Exposure to dental amalgam is not associated with high mercury exposure. However, usage of cosmetic products containing mercury and high seafood consumption may lead to the increase of exposure to mercury.

IMPLICATIONS: Exposure to the high levels of mercury from dental amalgam can lead to serious health effects among the dental health care workers. Nationwide chronic mercury exposure among dental personnel was assessed through urinary mercury levels. Findings suggest low urinary mercury levels of these health care workers. Exposure to dental amalgam is not associated with high mercury exposure. However, the usage of cosmetic products containing mercury and high seafood consumption may lead to the increase of exposure to mercury.

5) Cochrane Database Syst Rev. 2014 Mar 31;(3):CD005620. doi: 10.1002/14651858.CD005620.pub2.

Direct composite resin fillings versus amalgam fillings for permanent or adult posterior teeth.

Rasines Alcaraz MG 1, Veitz-Keenan A, Sahrmann P, Schmidlin PR, Davis D, Iheozor-

Ejiofor Z.

Abstract

BACKGROUND: Amalgam has been the traditional material for filling cavities in posterior teeth for the last 150 years and, due to its effectiveness and cost, amalgam is still the restorative material of choice in certain parts of the world. In recent times, however, there have been concerns over the use of amalgam restorations (fillings), relating to the mercury release in the body and the environmental impact following its disposal. Resin composites have become an esthetic alternative to amalgam restorations and there has been a remarkable improvement of its mechanical properties to restore posterior teeth.There is need to review new evidence comparing the effectiveness of both restorations.

OBJECTIVES: To examine the effects of direct composite resin fillings versus amalgam fillings for permanent posterior teeth, primarily on restoration failure.

SEARCH METHODS: We searched the Cochrane Oral Health Group's Trials Register (to 22 October 2013), the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2013, Issue 9), MEDLINE via OVID (1946 to 22 October 2013), EMBASE via OVID (1980 to 22 October 2013), and LILACs via BIREME Virtual Health Library (1980 to 22 October 2013). We applied no restrictions on language or date of publication when searching the electronic databases. We contacted manufacturers of dental materials to obtain any unpublished studies.

SELECTION CRITERIA: Randomized controlled trials comparing dental resin composites with dental amalgams in permanent posterior teeth. We excluded studies having a follow-up period of less than three years.

DATA COLLECTION AND ANALYSIS: We used standard methodological procedures expected by The Cochrane Collaboration.

MAIN RESULTS:

Of the 2205 retrieved references, we included seven trials (10 articles) in the systematic review. Two trials were parallel group studies involving 1645 composite restorations and 1365 amalgam restorations (921 children) in the analysis. The other five trials were split-mouth studies involving 1620 composite restorations and 570 amalgam restorations in an unclear number of children. Due to major problems with the reporting of the data for the five split-mouth trials, the primary analysis is based on the two parallel group trials. We judged all seven trials to be at high risk of bias and we analyzed 3265 composite restorations and 1935 amalgam restorations.The parallel group trials indicated that resin restorations had a significantly higher risk of failure than amalgam restorations (risk ratio (RR) 1.89, 95% confidence interval (CI) 1.52 to 2.35, P value < 0.001 (fixed-effect model) (low-quality evidence)) and increased risk of secondary caries (RR 2.14, 95% CI 1.67 to 2.74, P value < 0.001 (low-quality evidence)) but no evidence of an increased risk of restoration fracture (RR 0.87, 95% CI 0.46 to 1.64, P value = 0.66 (moderate-quality evidence)). The results from the split-mouth trials were consistent with those of the parallel group trials.Adverse effects of dental restorations were reported in two trials. The outcomes considered were neurobehavioral function, renal function, psychosocial function, and physical development. The investigators found no difference in adverse effects between composite and amalgam restorations. However, the results should be interpreted with caution as none of the outcomes were reported in more than one trial.

AUTHORS' CONCLUSIONS: There is low-quality evidence to suggest that resin composites lead to higher failure rates and risk of secondary caries than amalgam restorations. This review reinforces the benefit of amalgam restorations and the results are particularly useful in parts of the world where amalgam is still the material of choice to restore posterior teeth with proximal caries. Though the review found insufficient evidence to support or refute any adverse effects amalgam may have on patients, new research is unlikely to change opinion on its safety and due to the decision for a global phase-down of amalgam (Minamata Convention on Mercury) general opinion on its safety is unlikely to change.