Experimental ammonia-free phosphate-bonded investments using Mg(H2PO4)2.

Z Zhang, Y Tamaki, T Miyazaki

Journal: Dental materials journal 2002;20(4):339-44

PMID: 11915627

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Abstract

In previous study, we found that Mg(H2PO4)2 instead of NH4H2PO4 was available as a binder material for phosphate-bonded investments and possibly could be used to develop the phosphate-bonded investment without ammonia gas release. The purpose of the present study was to develop the experimental ammonia-free phosphate-bonded investments by investigating suitable refractories. Mg(H2PO4)2.nH2O and MgO were prepared as a binder. Cristobalite and quartz were selected as refractories. The power ratio of MgO/Mg(H2PO4)2.nH2O was set constant at 1.2 according to our previous findings. Fundamental properties of dental investment such as strength, manipulation and expansion were evaluated. Using cristobalite as the refractory material, further investigations were performed. The refractory/binder ratio was definitely effective. The increase of this ratio led to low mold strength and large mold expansion. The present findings suggested that C5 was desirable for dental investment.

Address: Department of Operative Dentistry, Showa University School of Dentistry, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo 142-8555, Japan.

DOI: 10.4012/dmj.20.339

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MeSH Terms: Ammonia, Chemical Phenomena, Chemistry, Physical, Compressive Strength, Dental Casting Investment, Humans, Magnesium Compounds, Magnesium Oxide, Materials Testing, Particle Size, Phosphates, Powders, Quartz, Rheology, Silicon Dioxide, Statistics as Topic, Stress, Mechanical, Surface Properties, Thermodynamics, Viscosity, Water