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Logo of oenvmedOccupational and Environmental MedicineVisit this articleSubmit a manuscriptReceive email alertsContact usBMJ
Occup Environ Med. 2007 December; 64(12): 856.
PMCID: PMC2095360

Authors' reply

We thank Minoia et al for their interest in our publication, and for suggesting that intra‐oral metallic amalgams and restorations may contribute to salivary levels of heavy metals, such as mercury, lead and cadmium. While the release of mercury from amalgams is well recognised, less is known of the release of cadmium and lead.

The dissolution rate of cadmium from dental gold solder alloys in vitro is estimated to be 40 µg per mm2 per year.1 In the worst simulated oral condition of an exposed solder area of 0.5 cm2, up to 2 mg of cadmium could be released into the oral cavity (0.004 µg of cadmium per min). Considering that it takes about one minute to collect 1 ml of saliva and assuming that all of the cadmium released from the dental amalgam during that time is deposited in the sample, it would contribute only 4 µg per litre of saliva obtained. In a study of workers with exposure to cadmium, mean (standard deviation) salivary cadmium levels of 59.7 (19.2) µg/l in exposed workers, while non‐exposed workers had mean salivary cadmium levels of 10.9 (0.8) µg/l.2 Thus, dental amalgams may not be a major confounder of salivary cadmium levels among exposed persons, but this will require confirmation with further studies.

Similarly, there is a weak correlation between blood and saliva lead concentrations at blood lead concentrations below 300–500 µg/l,3,4 but the correlation is stronger for higher blood lead levels.5 Thus, if the release of lead from intra‐oral metal restorations confounds measurement of their salivary concentrations, this is likely to occur among individuals with lower levels of lead exposure.

Finally, we agree with Minoia et al that contamination during sampling is potentially a major methodological issue, and did emphasise this in our paper. We would like to reiterate that environmental contamination during specimen collection can occur regardless of the specimen collected—saliva, blood or urine—and measures should be taken to minimise this.


Competing interests: None declared.


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3. Nriagu J, Burt B, Linder A. et al Lead levels in blood and saliva in a low income population of Detroit, Michigan. Int J Hyg Environ Health 2006. 209109–121.121 [PMC free article] [PubMed]
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