Title

Mercury Leakage from Amalgam Restorations due to Carbamide Peroxide

Clinical Question

In adults with amalgam restorations, can teeth-whitening products like carbamide peroxide cause a release of mercury?

Clinical Bottom Line

All three in vitro studies indicated that carbamide peroxide could cause a significant release of mercury ions from various brands or types of dental amalgams. However, the average amount of Hg released over 2 hours would be within the World Health Organization (WHO) regulation (40 ug/day).

Best Evidence

PubMed ID	Author / Year	Patient Group	Study type (level of evidence)
21203732	Kasraei/2010	48 admixed (GS-80) and 48 spherical (Orally Magicap S) amalgam discs	In vitro comparative study
Key results	48 admixed and 48 spherical amalgam discs treated with 16% carbamide peroxide (Nite White) at 14 and 28 hours were found to release more mercury than controlled group (p<0.001). No significant difference was found in Hg release between the two brands of amalgam (p=0.119) and between the two difference exposure times (p=0.329). Kasraei et al. concluded that the amount of Hg released was 27.8µg/day from 2hr application, which was less than the maximum mercury intake (40µg/day) established by WHO.
17910224	Gurgan/2007	62 amalgam discs (Tgloy, Septalloy NG 50, Dispersalloy, Permite C)	In vitro
Key results	62 amalgam discs from four different brands exposed to 16% and 30% carbamide peroxide for different lengths were found to release a significant amount of Hg compared to controlled group (p<0.05). No significant difference was found between the two concentration (p>0.05). However, Dispersalloy (admixed alloy) had the highest Hg release from 16% CP exposure, and Septalloy NG50 had the lowest Hg release from 30% CP exposure. In short, Dispersalloy released about 17.38µg of Hg per day from 1hr of 16% CP application, and this amount is below the WHO standard.
15575446	Rotstein/2004	128 amalgam discs (Valiant Ph. D.)	In vitro
Key results	A total of 128 amalgam discs were separated into freshly prepared and aged groups and subdivided as polished versus unpolished. Then, they were submerged in 10% CP at either pH 4.5 or pH 6.5 for 1, 4, 7, 10, 13 days. Aged amalgam significantly released more Hg than fresh amalgam (p<0.001). They also found that longer exposure, lower pH, and unpolished surface could cause more Hg release. The aged, unpolished amalgam submerged in 10% CP at pH 4.5 for 13 days released about 10.24µg/hr. Based on the average hourly Hg released by any of the tested discs at any of the tested conditions, 2-hr bleaching session would not exceed the WHO regulation (40µg/day).

Evidence Search

(("Dental Amalgam"[Mesh]) AND "Mercury"[Mesh]) AND ( "Peroxides"[Mesh] OR "carbamide peroxide" [Supplementary Concept] )

Comments on
The Evidence

All three studies were done in vitro with fairly large sample sizes, so there were a great amount of control and consistency over various factors. Method and resulting data were all provided in detail. None of the researches showed any competing interest, and biases were unlikely.

Applicability

Based on all three studies, the average amount of Hg released over a 2 hours bleaching treatment would be within WHO regulation (40ug/day). However, dentist should know that these numbers came from in vivo studies, and they must use this information with that in mind.

Specialty

(Public Health) (General Dentistry) (Restorative Dentistry) (Dental Hygiene)

Keywords

Carbamide peroxide, bleach, dental amalgam, mercury

ID#

2393

Date of submission

03/01/2013

E-mail

Changs3@livemail.uthscsa.edu

Author

Shingmei Chang

Co-author(s)

Co-author(s) e-mail

Faculty mentor

Karen Troendle, DDS

Faculty mentor e-mail

troendle@uthscsa.edu

Basic Science Rationale
(Mechanisms that may account for and/or explain the clinical question, i.e. is the answer to the clinical question consistent with basic biological, physical and/or behavioral science principles, laws and research?)

None available

Comments and Evidence-Based Updates on the CAT
(FOR PRACTICING DENTISTS', FACULTY, RESIDENTS and/or STUDENTS COMMENTS ON PUBLISHED CATs)

None available