BITE BACK
And there it is again. The painful experience resulting from foul teeth and the dawning realisation that another undesired visit to the dentist becomes inevitable. In the reality of shrill drilling sounds, affected humans of all ages tend to make a promise to take better care of their ivories after this surgery. However, once the pain has subsided, this promise usually does not persist. Though it really should.
Tooth decay is one of the most widespread diseases amongst humans, and is a result of a progressed invasion of the bacteria Streptococcus Mutans, a natural inhabitant of our oral cavity. Estimation of the amount of carious teeth in school-age children in the UK alone, sums up to the breathtaking quantity of twelve million decayed teeth every year. In other words, this relates to one necessary surgery every two and a half seconds! Amazingly, similar figures are also available for all industrialised nations worldwide.
And although the outer shell of our teeth, the dental enamel, is the hardest material produced by our body, the reality is that even this substance is subject to decay. So understanding the process of this decomposition will effectively help to reduce the enormous amount of affected teeth worldwide.
Here, scientific investigations have found that the role of bacteria is, in fact, passive. These single cell organisms feed on organic nutrition provided in abundance by our modern sugar rich diet. The metabolism of the micro organisms converts these carbohydrates into acids. Fortunately, our teeth are relatively resistant against such corrosive conditions, but the reaction is still happening, albeit very slowly. Crevices are formed in which the bacteria can spread more easily, and also hide from tooth brush attacks. At some point, it’s when these crevices develop into larger cavities, that a visit to the dentist is due.
Until recent years, this visit resulted in teeth decorated with a dark silver material called amalgam, derived from the Arabic expression al-malgam meaning softening ointment. This filling substance can be cheaply produced and is easily incorporated into the tooth. Unfortunately, metallic teeth are now generally considered unsightly, and are thus no longer first choice in restorative dental materials. Furthermore, there is a bigger disadvantage with amalgams. They contain small amounts of the noxious metal mercury, which can constantly vaporize and wash out of the filling to be breathed or swallowed.
Even now, research is still uncertain about how much daily mercury can be attributed to amalgam fillings in an individual. Investigations carried out almost a decade ago by Peter Krauss at the University of Tübingen, Germany, revealed that only approximately 30% of a sampled European population remain within the healthy limit of 21ug of mercury ingestion per day (as recommended by the World Health Organisation). However, this means that 70% lies above this maximum, suggesting a need to for health officials to be seriously concerned of mercury poisoning. In this particular case, the German Ministry of Health answered these findings with a counterstatement downplaying the results, but (according to Krauss), these counterstatements lacked any scientific merit. In fact, Krauss suggests such action was taken solely to calm the concerns his research evoked in central Europe. In any event, many patients still tried to remove all their fillings at once, inadvertently deteriorating the situation as far more mercury gets into the body during application and removal of the amalgam.
In practical terms, however, amalgam fillings are still the cheapest available and consequently are often the only type of filling to be subsidized by many health insurance companies (including some in Canada). In addition, amalgams also fair better in clinical dental performance tests. There is low incidence of cusp fracture and recurrent decay in teeth with mercury fillings. While polymer resin fillings have a lifetime of less than five years, amalgam restorations have proven to last for decades in many cases exceeding the lifetime of ceramic restoratives.
Therefore, continuing studies into longevity of dental materials and possible adverse health effects should provide answers to better alternatives – perhaps to the development of novel materials that are both safe, cheap, and also exceed the performance of mercury amalgams. However, such materials are not yet available, and it remains with the patient to pick a preference. Of course, the best dental material is arguably that which occurs naturally in your mouth, developed by hundreds of thousands of years of trial and error. In short, maybe it’s just a case of not forgetting them so easily.
Further Reading
1 P. Krauss, M. Deyhle: Field Study on the Mercury Content of Saliva, Toxicological and Environmental Chemistry, Vol.63, 29, (1997). Email discussions with Prof. Krauss on the topic of mercury poisoning are very enlightening.
2 WHO, The European Health Report, Regional Office for Europe, Kopenhagen, Denmark, 2002
3 German Ministry of Health: “Saliva test”: Mercury Burden due to Amalgam Fillings, Bundesgesundheitsblatt, Band 40, 1997.
4 http://www.health.gov/environment/amalgam2/National.html
5 http://www.mercurypolicy.org
6 http://www.dentalwatch.org/hg/myths110.html
7 http://www.hc-sc.gc.ca/ahc-asc/media/nr-cp/1996/1996_63_e.html
8 http://www.sfenvironment.com/facts/mercury.htm
9 J. Welin, J.C. Wilkins, D. Beighton, K. Wrzesinskic, S.J. Fey, P. Mose-Larsen, I.R. Hamilton, G. Svensäter: Effect Of Acid Shock On Protein Expression By Biofilm Cells Of Streptococcus Mutans, FEMS Microbiology Letters, (2003), 2, Vol.227, p.287-293.
10 W.J.N. Collins, T.F. Walsh: A Handbook For Dental Hygienists, (1992), 3rd edition, Oxford, Wright.
11 H. Keene: History Of Dental Caries In Human Populations: The First Million Years, Symposium and Workshop on Animal Models in Cariology, Massachusetts, 1980.
12 R. Schiele, A. Knappworst: Amalgam – Pro und Contra, German Doctor’s Publishing, Köln, 1992.
13 H. Lichtenberg: Mercury Vapour in the Oral Cavity in Relation to the Number of Amalgam Fillings and Chronic Mercury Poisoning, Journal of Orthomolecular Medicine, 1996.
14 S.M. McKinlay: The Children’s Amalgam Trial Study Group, The Children’s Amalgam Trial: design and methods, Controlled Clinical Trials, Vol.24, Iss.6, p.795-814, 2003.