The shocking reality of metal dental materials – Phillip Silver

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  Posted by: Dental Design      6th July 2018

Since the 1980s, there has been a noticeable increase in the number of metal alloys used in dentistry.[1]A wide range of metal materials are used, for example gold crowns, chrome cobalt partial dentures, mercury fillings, nickel or iron based orthodontic wires, silver solders and titanium implants, all of which have different levels of electrical potential. This means that when dissimilar or incompatible restorative metals are located in the mouth, the scene may be set for oral galvanism.[2]

Oral galvanism, sometimes referred to as oral electricity, electro galvanism or galvanic currents is a dental phenomenon that has the potential to cause oral pain and discomfort. To explain: when metal dental materials are placed in the oral cavity, electromechanical and chemical reactions occur. If two or more dissimilar alloys exist in the mouth and are combined with saliva, which acts as an electrolyte, a flow of electric current can be produced through the metal/metal connections as well as the oral tissues, which can cause a sharp shock or pain.1

It has been suggested that these electrical currents can reach up to 900 millivolts superseding the body’s normal 450 millivolts, which could interfere with the energy flow to the brain. This may be the reason why electro galvanism has been named as a catalyst for many illnesses and symptoms including lack of concentration and memory, insomnia, tinnitus, vertigo, epilepsy, hearing loss, eye problems and psychological problems.[3]

The other aspect of oral galvanism is that the interaction of dissimilar alloys can also accelerate corrosion rates and therefore pose a greater risk of undesirable reactions in the mouth as well as the amount of metal ions that may be released into the body.1 Interestingly, in a study conducted in 1985, a research team[4]found that when mercury fillings were in close proximity to gold crowns, the mercury release was ten times greater when compared to mercury fillings alone.3It has also been noted that, although the corrosive process is primarily due to electrochemical reaction, fluctuations in temperature and changes in pH due to diet as well as the decomposition of food, are also favourable for galvanic corrosion.1

The exposure of metal ions as a result of galvanic currents means that corrosive products are distributed into the saliva and surrounding tissues. This alone can cause an unpleasant metallic taste and burning feeling and but as well as local sensations, it can trigger a variety of symptoms from mucosal changes and skin disease to headache, nausea, problems with the eyes, throat or ears and even excessive fatigue and autoimmune diseases.[5],[6]

It is becoming increasingly important to evaluate the potential for incompatible electricity-generating dental materials. Dental professionals are seeing many more patients of ‘the heavy metal generation’ who have been treated for many years with metal fillings and restorations. Not only do these patients have higher maintenance needs as they age, but due to their existing oral environment they are placed at a higher risk of oral galvanism. Correspondingly, dental health surveys indicate that the proportion of partially dentate older adults is increasing[7]and a great many of these patients are likely to be looking for solutions to replace missing teeth.

Certainly, dental implants have good survival rates and are an extremely popular choice with both clinicians and patients. However, it is worth bearing in mind that the corrosion behaviour of some dental alloys could render certain materials inappropriate for placement.[8]An equally large proportion of patients opt for a removable partial denture and GDPs often prefer to supply a cobalt-chromium based frame.[9]However, an interesting study that measured the electrochemical cells created when dentures of cobalt-chromium alloys were placed on teeth with various metal restorations revealed that conventional amalgam and nickel-chromium alloys had high corrosion currents.[10]

Fortunately, the selection of materials that can be used in the clinical field is evolving rapidly and there are a number of alternatives to mixing different metals in the mouth. Solvay Dental 360for instance, has custom-developed a material called Ultaire AKPspecifically for the fabrication of removable partial denture (RPD) frames. With biocompatibility of paramount importance, this high performance polymer is completely metal-free and eliminates the difficulties associated with different metal combinations in the mouth. RPDs made from Ultaire AKPare strong enough to meet rigid performance requirements but are also elastic in tension, thin and lightweight so they feel comfortable in the mouth. This new material does not distort and has bone-like properties that improve the overall fit of the dentures. This also effectively avoids point loading or uneven force and could even limit future bone loss.


Of course, dental practitioners should be ever mindful of the range of chemical combinations that could be occurring in the mouths of patients. Yet, with progressive new technology and innovative new materials it is hoped that oral galvanisation and other such difficulties might rapidly become a thing of the past.


For more information about Solvay Dental 360™, Ultaire™ AKP and Dentivera™ milling discs, please visit





[1]Hamoon Zohdi et al. Galvanic Corrosion Behaviour of Dental Alloys.  Environmental and Industrial Corrosion – Practical and Theoretical Aspects, Chapter 7. 157-168.[Accessed 1st November 2017]

[2]Certosimo AJ et al. Oral electricity. Gen Dent. 1996 Jul-Aug;44(4):324-6.[Accessed 1st November 2017]

[3]Dr Gerald H Smith, author of Reversing Cancer: a Journey from Cancer to Cure – Dental/Cancer Connection. International Centre for Nutritional Reaserch Inc.[Accessed 1st November 2017]

[4]A. Knappworst, E. Gura, D. Fuhrmann and A. Enginalev.

[5]Stejskal V et al. Diagnosis and treatment of metal-induced side effects. Neuro Endocrinol Lett. 2006 Dec;27 Suppl 1:7-16.[Accessed 1st November 2017]

[6]Prof. Dr. W. Opydo Poznanand Dr. J. Opydo-Szymaczek. Metallic dental materials in patient’s oral cavity acting as electrodes of electrochemical cells. 2003. W 3775 Materials and Corrosion 2004, 55, No. 7[Accessed 1st November 2017]

[7]J Steele et al. Adult Dental Health Survey 2009: transformations in British oral health 1968–2009. British Dental Journal 213, 523 – 527 (2012)[Accessed 1st November 2017]

[8]NM Taher et al. Galvanic corrosion behaviour of implant suprastructure dental alloys. 2003. DOI: 10.1016/S0109-5641(02)00008-8[Accessed 1st November 2017].

[9]PF Allen et al.Attitudes and practice in the provision of removable partial dentures. British Dental Journal 204, E2 (2007)[Accessed 1st November 2017]

[10]Gjerdet NR. Galvanic cells including cobalt-chromium alloys.Acta Odontol Scand. 1980;38(5):273-8.[Accessed 1st November 2017]



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