Biomaterials 20 (1999) 1851}1866
E!ect of particle con"guration on structure and properties of dispersed
Pd-containing dental amalgam
K.I. Chen, C.P. Ju, J.H. Chern Lin*
Department of Materials Science and Engineering, National Cheng-Kung University, Tainan, Taiwan, ROC
Received 22 January 1999; accepted 10 April 1999
Abstract
The present work investigates the e!ect of particle con"guration on the structure and properties of four dispersed type
Pd-containing amalgams with the same chemical composition. The results indicate that particle con"guration plays an important role
not only in the structure and chemistry, but also in such properties as compressive strength, creep and mercury release rate.
Compromises among the various properties of the present Pd amalgams are needed, when a decision on particle con"guration is to be
made. As mechanical properties or corrosion resistance is concerned, the amalgam should comprise at least one spherical alloy
(matrix or dispersant). As far as mercury release is concerned, the amalgam should comprise irregular dispersant alloy. The amalgam
fabricated from irregular dispersant and spherical matrix particles seems to serve all well. 1999 Elsevier Science Ltd. All rights
reserved.
Keywords: Dental amalgam; Palladium; Microstructure; Compressive strength; Creep; Mercury vapor release
1. Introduction
Since the emergence of dispersed-type palladium (Pd)
amalgams in the mid-1980s, a number of promising re-
sults from Pd dispersants and Pd dispersant amalgams
have been reported. The Pd-induced improvements in-
clude reduced current density during anodic polarization
[1], higher compressive strength [2,3], lower creep rate
[4], inhibition of the formation of Cu
Sn
phase [5] and
the transformation of Ag
Hg
(
) to AgHg(
) at ele-
vated temperatures, as well as drastically reduced early
stage mercury vapor release from the matrix
phase [6].
It was also reported that the addition of Pd in
aAg}25Sn}12Cu amalgam alloy decreased the amount
of released mercury vapor during setting [7]. Amalgam
containing Pd also showed superiority in reduced
number of surface luster and less electrochemical
activity [8].
It was reported that the composition, particle shape
and size of amalgam alloys could all a!ect the handlabil-
ity, phase contents and properties of amalgam [9,10].
Compared to those from lathe-cut irregular-shaped
* Corresponding author. Tel./Fax: #6-2748086.
E-mail address: chernlin@mail.ncku.edu.tw (J.H. Chern Lin)
particles, amalgams fabricated from spherical-shaped (at-
omized) particles generally exhibited shorter working
time [9], less mercury content [11], less sensitivity to
condensation pressure [10], less dimensional change
[12], lower creep [9,11}14] and higher compressive
strength [12]. Disadvantages of amalgams prepared
from spherical particles include their relatively high mer-
cury vapor release rates [15,16] and the reported more
extensive microleakage than that from lathe-cut irregu-
lar-shaped alloy particles [17,18].
In a study of dispersed-type Pd amalgam by Marshall
et al. [19], a comparison was made between a lathe-cut
Ag}28Cu}10Pd dispersant blended with lathe-cut matrix
alloy and the same dispersant blended with spherical
matrix alloy. Their results indicated that the amalgam
prepared from spherical matrix alloy had higher Cu
Sn
() and less Sn
Hg (
) contents. The results of Mante
et al. [3,20], however, showed that the amalgam fab-
ricated from a lathe-cut Ag}28Cu}15Pd dispersant and
a spherical matrix alloy had a higher content of unreac-
ted particles and lower content of , compared
to a similar amalgam fabricated from a lathe-cut
matrix alloy. Apparently further research is needed in
this area.
Although the existing results of Pd amalgams concern-
ing particle con"guration e!ect are far from complete, it
0142-9612/99/$ - see front matter 1999 Elsevier Science Ltd. All rights reserved.
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