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Biomedical subjects

T K Vaidyanathan

Publications and source records attributed to T K Vaidyanathan.

33 records · Page 2Linked to original sources
PubMed1986

Fracture toughness determination of dental amalgams through microindentation.

A microindentation technique was used to study and estimate the fracture toughness of six amalgams. A significant difference is observed between fracture toughness at the bulk and the margin of amalgams. All amalgams show significant differences in fracture toughness as a function of distance from the margin. Microindentation measurement of fracture toughness appears to be an effective method of evaluating the localized brittleness of amalgams.

Dental Alloys↗
PubMed1985

Scanning electron microscope evaluation of wear of dental curettes during standardized root planing.

Root planing relies upon the quality of instrument cutting edges. This study evaluated the sharpness and wear of some dental curettes available in the market following standardized root planing procedures. Nine working edges of nine Gracey No. 1/2 DE curettes, three each from three different manufacturers, were used as controls. These unused factory-sharpened edges were examined by scanning electron microscope (SEM). Eighteen edges of nine curettes of the same brands were likewise examined after root planing procedures. Root planing was carried out on extracted one-rooted teeth mounted in natural positions in manikin jaws. Working areas measuring 3 X 5 mm were marked on root surfaces previously exposed by periodontitis. Root planing procedures included 15 vertical strokes done by either Side 1 or Side 2 of each instrument in relation to a single working area of a tooth, and the same procedure repeated 3 times using the opposite side of the curette. All working edges were examined at points 1 and 2 mm from the tip under 500 times magnification. Edge deformation increased significantly from the control group to the "15-stroke" group and from the "15-stroke" group to the "45-stroke" group. Factory-sharpened curettes (control) were sharp, with functional wire edges present on 55% of the specimens. After 15 strokes, nonfunctional wire edges and narrow edge deformations with bevels measuring less than 15 mu were present. After 45 strokes eight cutting edges (88.9%) showed bevels wider than 15 mu. The difference between the three brands was not significant in any group (i.e., controls, 15 strokes, 45 strokes). Further study is indicated to evaluate the relationships between bevel dimensions and root planing effectiveness.

Curettage↗
PubMed1984

Demineralization and ion binding action of polycarboxylate cement liquid on human dental enamel.

The demineralization and ion binding effects on dental tissues due to poly(acrylic) acid attack under different dilution conditions of the latter are studied by scanning electron microscope (SEM) and infrared (IR) spectroscopy. The results indicate that in addition to the general demineralization effects such as preferential prism core attack, prism periphery attack, and protruding prism rods, competing ion binding effects also occur. Using optimum dilution conditions, the microstructural effects of demineralization and ion binding are shown and the effects are related to IR spectral observations.

Dental Cements↗
PubMed1983

Dental amalgams.

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Chemical Phenomena↗
PubMed1981

In vitro corrosion and tarnish characterization of typical dental gold compositions.

Analysis of the anodic polarization and alternate immersion test response of 16 precious metal alloys with compositions similar to those of commercial dental golds indicate that alloys containing high (Ag + Cu) contents are likely to be more corrosion and tarnish prone. It also appears that the alloys containing high precious metals contents (Au, Pt, and Pd) are characterized by immunity or anodic film protection over a range of anodic overpotentials, indicating superior corrosion resistance.

Copper↗
PubMed1981

In vitro tarnish of dental amalgams.

1. Tuccillo-Nielsen tarnish test in an effective screening device for dental amalgams. 2. The gamma phase appears to be more tarnish prone in conventional dental amalgams than gamma 1 phase. Although gamma 2 appeared to be tarnish prone, it was difficult to discriminate this phase because of the porosity in the amalgams. 3. The copper-rich phases are the most tarnish prone in high-copper amalgams. Gross examinations of amalgam from additive systems show spotty tarnish, whereas more uniform tarnish appearance is observed in amalgams from single-composition alloys. 4. The amalgams can be graded for in vitro tarnish performance in selected groups like the additive systems and the single-composition alloys.

Copper↗
PubMed1981

Correlation between macroscopic porosity location and liquid metal pressure in centrifugal casting technique.

Radiographic analysis of uniform cylindrical castings fabricated by the centrifugal casting technique has revealed that the macroscopic porosity is dependent on the location of the sprue attachment to the casting. This is attributed to the significant pressure gradient associated with the centrifugal casting technique. The pressure gradient results in different heat transfer rates at portions of the castings near and away from the free surface of the button. Consequently, the macroscopic porosity is invariably at portions of the casting close to the free surface of the button. In addition, some optimized sprue-reservoir combinations could be predicted and proved, based on this pressure gradient concept.

Chemical Phenomena↗
PubMed1981

In vitro corrosion and tarnish analysis of the Ag-Pd binary system.

Binary compositions over the entire range of compositions of the Ag-Pd system are characterized by anodic polarization in Ringer's solution and alternate immersion in 0.5% Na2S solution. The results show that a wide range of protection and passivation tendencies are introduced with Pd alloying of Ag.

Corrosion↗
PubMed1979

In vitro deformation failure analysis of dental amalgams.

The in vitro deformation failure behavior of the conventional and the recent high copper dental amalgams is studied under different strain rates. The conventional silver-tin amalgams exhibited significant slow compressive flow at low strain rates, but failed catastrophically at the higher loading rates. On the other hand, amalgams containing highest copper contents showed no compressive flow and failed catastrophically at all the loading rates. The slow compressive flow in the conventional dental amalgams indicate that dislocations may play an important role in the deformation process of the amalgams at the lower strain rates.

Copper↗