Surface analysis of dental amalgams by X-ray photoelectron spectroscopy and X-ray diffraction

doi:10.1016/S0109-5641(03)00007-1

Dental Materials

Volume 19, Issue 7, November 2003, Pages 639-644

https://doi.org/10.1016/S0109-5641(03)00007-1 Get rights and content

Abstract

Objectives. It is important to characterize the surface of dental amalgam in order to understand the process of mercury release from amalgam restorations in the oral cavity. The mercury evaporation occurs not only from the newly made restoration but also from the set material.

Methods. The surfaces of four different types of amalgams, which had been well set, were analyzed with X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) and the relationship between surface compositions and mercury release was studied. Fresh amalgam surfaces as well as aged surfaces, which were stored for 30 days in air, were investigated using XPS and the chemical states of amalgam components and oxygen were studied. The aged surfaces were also characterized with XRD and grazing angle XRD.

Results. With increased oxidation, the surface contents of tin and oxygen were increased in all amalgams. In contrast, the surface contents of copper and mercury were decreased. An increase of zinc or indium content were observed in zinc or indium containing amalgams, respectively. A surface layer enriched with indium and oxygen was clearly detected by XPS but not with grazing angle XRD.

Significance. The thickness of the enriched surface layer is estimated to be in the order of few nanometer, which is approximately equal to the analysis depth of XPS. In addition, the presence of metallic elements, like tin and zinc, that readily form a stable oxide layer at the surface suppress the release of mercury.

Introduction

The mercury evaporation from amalgam restorations in the oral cavity has been extensively debated in recent years. The evaporation occurs not only from the newly made restoration but also from the set material [1], [2], [3], [4], [5], [6], [7], [8], [9], [10], [11], [12], [13], [14]. In an ongoing study, Berglund et al. studied the in vitro mercury evaporation from brushed surfaces of four different brands of amalgam. The conventional type of amalgam showed a more rapid decrease of mercury release after brushing compared to the other types. The mercury evaporation is closely related to the state of the amalgam surface. Therefore, an analysis of the chemical state of the amalgam surface is necessary in order to reveal the relationship between the mercury release and amalgam composition.

X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) provide the chemical state information on the surface layer and the depth composition profiles. Therefore, XPS and AES have been widely applied for the analysis of surface layer of amalgam. Hanawa et al. [15], [16] revealed that the zinc containing amalgam forms a tin and zinc oxide layer on the surface and this layer suppresses the mercury evaporation. Nakajima et al. [17] using AES reported that the surface of indium containing amalgam was rapidly covered with both an indium and a tin oxide films. McDermott et al. [18] studied the surface of high copper amalgams using XPS and suggested a SnO₂ like surface oxide component in high copper amalgams.

The purpose of this study was to analyze the surface layers formed on four different brands of amalgams and estimate the relationship between the chemical state of surface layers and mercury release rates.

Section snippets

Materials and methods

The dental amalgam alloys tested were ANA 68, ANA 2000, Dispersalloy and Indiloy (Table 1). The cylindrical specimens of each alloy (4 mm in diameter, 8 mm in height) were prepared by a specially trained person. This was carried out 5 years prior to the measurements of mercury release according to the procedures outlined in ISO 1559:1995 Dental materials–alloys for dental amalgam. The specimens were kept in dried air at room temperature. The specimens were thereafter cut into disks with a

Results

The bulk composition (Table 1) and the surface composition of metallic elements measured by XPS (oxygen and carbon excluded) of nearly non-oxidized (fresh) and fully oxidized (aged) surfaces are shown in Fig. 1. The oxygen content of fresh and aged surfaces were shown in Table 2. With increasing oxidation from a fresh surface to an aged surface, the surface content of tin and oxygen increased in all amalgams. In contrast, the surface contents of copper and mercury decreased. In the zinc

Discussion

As shown in Fig. 1, the amalgam surfaces were enriched either with tin, zinc, indium or two of these and oxygen with oxidation. The surfaces of conventional amalgam (ANA 68) and high copper amalgam (ANA 2000) were rapidly enriched with tin. The zinc containing amalgam Dispersalloy showed rapid increase of zinc content and a slow increase of tin content on the surface. The indium containing amalgam Indiloy showed a rapid increase of indium. The tin content for fresh surfaces and aged surfaces of

Acknowledgements

This study was supported by the scientific exchange program between the Royal Swedish Academy of Science and the Japan Society for the Promotion of Science. The authors would like to thank Dr Andrei Shchukarev and Dr Dan Boström, Department of Inorganic Chemistry, Umeå University, for XPS and XRD measurements. The authors would also like to thank Ms Ewa Gruffman and Mr Rolf Olofsson, Department of Dental Materials Science, Umeå University, for the valuable technical assistance. The authors

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The intravenous administration of ionic indium to pregnant hamsters is reported to produce malformations of the fetal digits.
The most common routes of exposure for the general population are inhalation and ingestion; for occupationally exposed persons, it is inhalation. The use of In for nanotechnology may increase the possibility of dermal absorption in work environments.
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Surface analysis of dental amalgams by X-ray photoelectron spectroscopy and X-ray diffraction

Abstract

Introduction

Section snippets

Materials and methods

Results

Discussion

Acknowledgements

Lancet

Dent Mater

Dent Mater

Dent Mater

The effect of dental amalgams on mercury levels in expired air

J Dent Res

The effect of dental amalgam restorations on blood mercury levels

J Dent Res

Mercury in human breath from dental amalgams

Bull Environ Contam Toxicol

Intra-oral air mercury released from dental amalgam

J Dent Res

Serial measurements of intra-oral air mercury: estimation of daily dose from dental amalgam

J Dent Res

Mercury exposure from dental fillings. II. Release and absorption

Swed Dent J

Determination of the rate of release of intra-oral mercury vapor from amalgam

J Dent Res

Estimation by a 24 h study of the daily dose of intra-oral mercury vapor inhaled after release from dental amalgam

J Dent Res