rnal of Oral Rehabilitation,
1975, Volume 2, pages 165-167
The primary factor of the creep resistance of dispersant amalgams
M. M . A. \K\^HOE¥ and F . C. M. D R I F S S E N S Science and Technology Department, University of Nijmegen, The Netherlands
Dental Materials Nijtnegen,
Introduction The creep of dental amaigam has been recognized as a property important for the functioning of amalgam restorations under oral conditions (Mahler e! al, 1970; Mahler, Terkia & Van Fysden, 1973; Binon et al., 1973). Recently attention has been paid to dispersant alloys because their amalgams have a high creep resistance. A dispersant amalgam alloy is prepared by adding between 5 and 25 wt % of a silver-copper alloy containing at least 50 wt % silver to a powder of a dental amalgam alloy with a composition within the conventional limits of the ADA-specification no. I (see, e.g. Youdelis & Innes, 1963). It is known that the creep resistance of non-dispersant amalgams can be determined for the whole or partially by the choice of the corresponding amalgam alloy (Vrijhoef & Driessens, 1974). No attention has been paid up to now to the effect of the choice of the amalgam alloy with the conventional composition occurring in the dispersant alloy mixture on the creep resistance of the resulting (dispersant) amalgam. Investigation It was the aim of this study to investigate the influence of this factor on the creep resistance of the dispersant amalgam. Three non-dispersant dental amalgam alloys were selected as available on the dental market; the resulting amalgam no. I* being very creep resistant, no. 2t having medium creep resistance and the amalgam prepared from alloy no. 3J showing up a low creep resistance. Dispersant amalgam alloys were prepared by mixing a silver-copper eutectic alloy (28-1 wt % Cu) with these amalgam alloys. The dental amalgam alloys were triturated with mercury for 10 s with a Silamat mixing machine. Cylindrical specimens were prepared according to ADA-specification no. I (ADA, 1972) except for two changes. The triturated mass was kept under a load of 76 MN/m- instead of 14 MN/ m^, and the time between the mixing and the loading was 60 s instead of 30 s. After annealing the specimens at 37°C for 24 h the cross sections of the test cylinders were * Cavex SF non zinc, Keur en Sneltjes, Haarlem, The Netherlands. + Cavex 68 non zinc, Keur en Sneltjes, Haarlem, The Netherlands, i Standalloy F, Degussa, Frankfurt am Main, West Germany. Correspondence: Professor F. C. M. Driessens, Dental Materials Science and Technology Department, University of Nijmegen, 'Heyendael', Erasmuslaan 1, Nijmegen, The Netherlands. 165
166
M. M. A. Vrijhoefand F. C. M. Driessens
Fig. 1. The creep rate i, determined at a stress of 116 MN/m^ at 22-5' C, of three different dispersant amalgams as a function of the silver-copper eutectic content of the corresponding dispersant amalgam alloy.
ground under tapwater and polished with a diamond paste perpendicular to the cylinder axis. Then the creep rate was determined in compression at 22'5+0'5^C and at a stress of 116 MN/m- as described elsewhere (Vrijhoef & Driessens, 1974). The influence of the addition of a silver-copper eutectic to the different amalgam alloys on the creep resistance of the resulting amalgams has been given in Fig. 1. From these results it might, be concluded that the creep resistance of a dispersant amalgam is controlled mainly by the choice of the (original) amalgam alloy and by the ratio of alloy to eutectic. Acknowledgment
The authors wish to thank Mr F. L. Lourens and Miss G. Covers for carrying out the experiments. References ADA (1972) Guide lo Dental Muterialx and Devices (Ed. by American Dental Association), ^th edn. Chicago. BiNoN, P., PHILLIPS, R.W., SWARTZ., M.L., NORMAN, R.D. & MEHRA, R. (1973) Clinical behavior
of amalgam as related to certain mechanical properties. Program and abstracts of papers I.A.D.R., Journal of Dental Research, 52., Special Issue, paper 509. MAHLER, D.B., TERKLA, L.G., VAN EYSDEN, J. & REISBICK, N . H . (1970) Marginal fracture vs mecha-
nical properties of amalgam. Journal of Dental Research, 49, 1452.
Creep resistance of dispersant amalgams
167
MAHLER, D.B., TERKLA, L.G. & VAN EYSDEN, J. (1973) Marginal fracture of amalgam restorations. Journal of Dental Research, 52, 823. VRIJHOEF, M.M.A. & DRJESSENS, F.C.M. (1974) On the static creep of denial amalgam. Journal of Dental Research, 53, 1138. YOUDELIS, W. V. & INNES, D.B.K. (1963) Dispersion strengthened amalgams. Journal of the Canadian Dental Association, 29, 587.
Manuscript accepted 16 September 1974
1975, Volume 2, pages 165-167
The primary factor of the creep resistance of dispersant amalgams
M. M . A. \K\^HOE¥ and F . C. M. D R I F S S E N S Science and Technology Department, University of Nijmegen, The Netherlands
Dental Materials Nijtnegen,
Introduction The creep of dental amaigam has been recognized as a property important for the functioning of amalgam restorations under oral conditions (Mahler e! al, 1970; Mahler, Terkia & Van Fysden, 1973; Binon et al., 1973). Recently attention has been paid to dispersant alloys because their amalgams have a high creep resistance. A dispersant amalgam alloy is prepared by adding between 5 and 25 wt % of a silver-copper alloy containing at least 50 wt % silver to a powder of a dental amalgam alloy with a composition within the conventional limits of the ADA-specification no. I (see, e.g. Youdelis & Innes, 1963). It is known that the creep resistance of non-dispersant amalgams can be determined for the whole or partially by the choice of the corresponding amalgam alloy (Vrijhoef & Driessens, 1974). No attention has been paid up to now to the effect of the choice of the amalgam alloy with the conventional composition occurring in the dispersant alloy mixture on the creep resistance of the resulting (dispersant) amalgam. Investigation It was the aim of this study to investigate the influence of this factor on the creep resistance of the dispersant amalgam. Three non-dispersant dental amalgam alloys were selected as available on the dental market; the resulting amalgam no. I* being very creep resistant, no. 2t having medium creep resistance and the amalgam prepared from alloy no. 3J showing up a low creep resistance. Dispersant amalgam alloys were prepared by mixing a silver-copper eutectic alloy (28-1 wt % Cu) with these amalgam alloys. The dental amalgam alloys were triturated with mercury for 10 s with a Silamat mixing machine. Cylindrical specimens were prepared according to ADA-specification no. I (ADA, 1972) except for two changes. The triturated mass was kept under a load of 76 MN/m- instead of 14 MN/ m^, and the time between the mixing and the loading was 60 s instead of 30 s. After annealing the specimens at 37°C for 24 h the cross sections of the test cylinders were * Cavex SF non zinc, Keur en Sneltjes, Haarlem, The Netherlands. + Cavex 68 non zinc, Keur en Sneltjes, Haarlem, The Netherlands, i Standalloy F, Degussa, Frankfurt am Main, West Germany. Correspondence: Professor F. C. M. Driessens, Dental Materials Science and Technology Department, University of Nijmegen, 'Heyendael', Erasmuslaan 1, Nijmegen, The Netherlands. 165
166
M. M. A. Vrijhoefand F. C. M. Driessens
Fig. 1. The creep rate i, determined at a stress of 116 MN/m^ at 22-5' C, of three different dispersant amalgams as a function of the silver-copper eutectic content of the corresponding dispersant amalgam alloy.
ground under tapwater and polished with a diamond paste perpendicular to the cylinder axis. Then the creep rate was determined in compression at 22'5+0'5^C and at a stress of 116 MN/m- as described elsewhere (Vrijhoef & Driessens, 1974). The influence of the addition of a silver-copper eutectic to the different amalgam alloys on the creep resistance of the resulting amalgams has been given in Fig. 1. From these results it might, be concluded that the creep resistance of a dispersant amalgam is controlled mainly by the choice of the (original) amalgam alloy and by the ratio of alloy to eutectic. Acknowledgment
The authors wish to thank Mr F. L. Lourens and Miss G. Covers for carrying out the experiments. References ADA (1972) Guide lo Dental Muterialx and Devices (Ed. by American Dental Association), ^th edn. Chicago. BiNoN, P., PHILLIPS, R.W., SWARTZ., M.L., NORMAN, R.D. & MEHRA, R. (1973) Clinical behavior
of amalgam as related to certain mechanical properties. Program and abstracts of papers I.A.D.R., Journal of Dental Research, 52., Special Issue, paper 509. MAHLER, D.B., TERKLA, L.G., VAN EYSDEN, J. & REISBICK, N . H . (1970) Marginal fracture vs mecha-
nical properties of amalgam. Journal of Dental Research, 49, 1452.
Creep resistance of dispersant amalgams
167
MAHLER, D.B., TERKLA, L.G. & VAN EYSDEN, J. (1973) Marginal fracture of amalgam restorations. Journal of Dental Research, 52, 823. VRIJHOEF, M.M.A. & DRJESSENS, F.C.M. (1974) On the static creep of denial amalgam. Journal of Dental Research, 53, 1138. YOUDELIS, W. V. & INNES, D.B.K. (1963) Dispersion strengthened amalgams. Journal of the Canadian Dental Association, 29, 587.
Manuscript accepted 16 September 1974
