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Biomedical subjects

M L Malhotra

Publications and source records attributed to M L Malhotra.

14 recordsLinked to original sources
PubMed1981

X-ray diffraction analysis of gamma 2 (Sn-Hg) phase in higher copper amalgams of varying mercury content.

Microstructures of high copper commercial amalgams containing varying amounts of mercury, ranging from 20% above to 25% below recommended values, were primarily investigated by x-ray diffraction. Mechanisms relating to the absence or presence of gamma 2 (Sn-Hg) phase in these amalgams were discussed in relation to the presence of copper and tin elements in their original alloys. The optimum mercury concentration in some amalgams was determined in order to keep them free of the gamma 2 (Sn-Hg) phase.

Chemical Phenomena↗
PubMed1980

Shear bond strength of porcelain-fused-to-alloys of varying noble metal contents.

The conclusions drawn from the present investigation are as follows: 1. The modification of waxing the metal rods prior to investing the baked porcelain disk in the dental stone eliminated the undesirable bond between the dental stone and the metal rod. The shear bond strengths obtained were believed to be true shear bond strengths. 2. Ceramo-metal restorations should be cooled at a slow rate, so that the alloy and the porcelain have approximately the same cooling rate. 3. Shear bond strengths developed in porcelain-metal composites were in descending order for Biobond, Vita, and Ceramco porcelain. 4. Push-test shear bond strengths were always higher than pull-test shear bond strengths. Both push- and pull-tests seemed to be equally valid for evaluating bond strengths in porcelain-metal composites. 5. The porcelain-metal composite of the silver-free gold alloy showed higher shear bond strengths for all porcelains.

Dental Alloys↗
PubMed1980

Shear bond strength in porcelain-metal restorations.

1. The push test method showed higher shear bond strength values than the pull test method. 2. A bond strength of 4,500 to 6,000 psi between the dental stone and metal rod was eliminated in a waxed-rod test. Although the strength values were lower in waxed-rod tests, they were believed to be true shear bond strength values. 3. Shear bond strengths of 12,000 psi in push tests and 9,700 psi in pull tests were observed in Ceramco porcelain fused to Ceramco gold.

Adhesiveness↗
PubMed1978

Physical properties of dental silver-tin amalgams with high and low copper contents.

Newly developed amalgams such as Tytin, Sybraloy, and Dispersalloy had low static creep, high compressive strength, and similar values for both diametral tensile strength and dimensional change in comparison with conventional amalgams such as Kerr Spheraloy, Caulk Spherical, Shofu Spherical, and Caulk 20th Century Micro Cut. The data for physical properties were evaluated statistically, and the amalgams were ranked according to the numerical position assigned to each property.

American Dental Association↗
PubMed1977

Microstructure of dental amalgams containing high and low copper contents.

Microstructure of commercial dental alloys and their amalgams were studied primarily by x-ray diffraction, optical metallography, scanning electron microscopy, and x-ray energy dispersive spectroscopy. X-ray diffraction revealed more phases than normally reported in these materials. Presence of new phase was discussed and their formation mechanism understood. Some phases having interacting 2 theta degrees values with others were properly identified. Both new and conventional dental alloys and their amalgams, namely Tytin, Sybraloy, Dispersalloy, Kerr Spheraloy, Caulk Spherical, Shofu Spherical, and Caulk 20th Century Microcut were used to complete the investigation.

Chemical Phenomena↗
PubMed1976

Microstructure in gold-containing Ag3Sn-amalgam.

The present study was conducted in order to understand the microstructural characteristics in dental amalgam which consists of both spherical and irregular Ag3Sn alloy particles with gold substituted in varying amounts for silver (0, 9, and 15%). Spherical alloy particles were used as obtained from Western Gold and Platinum and irregular alloy particles were prepared in the laboratory and then employed in the present study. The amalgam was prepared from the alloy particles by the trituration and condensation method. The polished and etched samples were studied using the techniques of X-ray diffraction, optical metallography, scanning electron microscopy, and X-ray energy dispersive spectroscopy. The microstructure in both types amalgam studied after two weeks of preparation contains gamma (unreacted Ag3Sn particles), gamma1 (Ag2Hg3), and gamma2 (Sn7-8Hg) phases in pure Ag3Sn-amalgam and gamma, gamma1, and (Au-Sn) phases in gold-containing amalgam. The The (Au-Sn) phase existed in the form of rings surrounding the gamma grains and acted as a barrier for mercury diffusion in Ag3Sn particles.

Dental Amalgam↗
PubMed1975

Identification of Au-Sn phase in Ag3Sn alloys containing gold.

Substitution of gold in part for silver in Ag3Sn alloys is found to result in two separate phases: gamma (Ag3Sn particles) grains with a uniform distribution of gold within the grain and an Au-Sn phase in a form of ring surrounding the gamma grain. The thickness of this ring increases with increasing gold concentration. The phases were identified by using the techniques of x-ray diffraction, optical metallography, scanning electron microscopy, and x-ray energy dispersive spectroscopy.

Dental Alloys↗