Background The Norwegian Directorate for Health and Social Affaires requested the Norwegian Knowledge Centre for the Health Service (NOKC) to do a health technology assessment (HTA) of the health effects of replacing amalgam fillings in persons on the suspicion of adverse health effects form amalgams. This HTA report will be one of three documents used in the work on guidelines to physicians and dentists.
Methods The work was carried out by a review team of external professionals. A systematic literature search was done and the literature was evaluated in a stepwise manner according to general principles of HTA-work. In all, 1.647 abstracts were reviewed by NOKC professionals at step 1. The review team evaluated full text publications in pairs reading 157 studies at step 2. In all 46 studies remained for internal and external validation assessment at step 3. A total of 17 studies were found to be relevant and of sufficient quality according to checklists and were included as the evidence base for the evaluation of the health effects of the removal of amalgam fillings.
Results of the literature search Fifteen clinical studies and two experimental studies were finally evaluated. The study design were patient series ranging from pilot studies of ten persons participating to 142 patients. The majority of identified studies of sufficient good quality on the health benefit of amalgam removal are concentrated on OLL.
The 13 studies on OLL and OLP indicate OLL to be contact dermatitis. The diagnosis was in general based on clinical examination and patchtest and sometimes biopsy. In nine of the follow-up studies, complete healing or partial healing were achieved in 72-95 % of the patients. Lesions extending beyond the contact area or not in contact with amalgam showed varying results. The results on OLP were weaker than for OLL. Most studies used a patch test as a diagnosic tool. Two studies followed both patch test positive and negative patient groups. In one study the groups were not different, and in the other the degree of healing was less than 50 % and the two groups varied. A third study showed complete or partial healing in 29 % of the patients despite not having removed the amalgam fillings. An immunohistochemistry study showed the reaction in OLL to have great similarities to contact dermatitis.
Patients often report multiple adverse health effects. Norwegian experience from the Dental Biomaterials Adverse Reaction Unit showed that the patients’ intensity in local and general symptoms was reduced after replacement of dental materials, but 37 not to the level found in a comparable group in the general population. No studies showed improvement in specific somatic diseases after replacement of amalgam fillings.
These patients presents themselves with complaints that can be considered to be of psychosomatic nature. These complaints are shared with other disorders. Any relevant studies of satisfactorily study design concentrating on using psychological tests when studying the effect of amalgam removal, could not be identified.
Conclusions The quality of the identified studies is low, regarding the effect on health problems believed to be relieved by amalgam removal. The main results of the synthesis of the study results are:
A great majority of oral lichenoid lesions in contact with amalgam fillings completely heal or improve after removal of amalgam fillings.
Lesions extending beyond the contact area, or not in contact with amalgam fillings, show little or no effect on healing after removal of the amalgam fillings.
The intensity of oral and general symptoms associated with amalgam fillings was reduced after removal of fillings but remained above the level observed in a representative control group. After removing the amalgam fillings the mercury level in urin and blood temporarily increase before being reduced to an acceptable level. Amalgam removal in healthy subjects was shown not to affect the kidneys as measured by the glomerular filtration rate.
Studies of sufficiently good scientific quality observing a reduction in signs and symptoms of general disorders after the removal of amalgam fillings, were not found.
Keywords: Dental Amalgam; Retreatment; Device Removal; Adverse effects.
Copyright ©2006 by The Norwegian Institute of Public Health (NIPH).