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V Piddock

Publications and source records attributed to V Piddock.

30 records · Page 2Linked to original sources
PubMed1990

Dental ceramics--an update.

The application of certain industrial ceramics and processing techniques has facilitated the introduction of a wide range of new dental restorative products including castable glass-ceramics, shrink-free materials and an ion-strengthening paste. However, these recent advances must be evaluated against the well-established materials and techniques developed more than 20 years ago. This article outlines interesting developments in the evolution of dental ceramics over the past 30 years and considers the current state of the art.

Ceramics↗
PubMed1989

Effect of alumina concentration on the thermal diffusivity of dental porcelain.

The importance of the thermal diffusivity of restorative dental materials is well established. The laser flash method first described by Parker et al. (1961) is widely used to determine the diffusivity of industrial materials but has not hitherto been reported in the study of dental materials. The effect of the crystalline alumina content of dental porcelains has been investigated using this technique which permits rapid and accurate measurement. Values of 1.45 mm2/s and 0.66 mm2/s were determined for a commercial aluminous core porcelain and a dentine porcelain respectively. Mixtures of core and dentine powders exhibited intermediate levels. Increasing the alumina content resulted in increased diffusivity. The highest value was determined for a new high strength aluminous core porcelain which yielded a diffusivity of 1.74 mm2/s. This material was found to contain an increased concentration of alumina particles.

Aluminum↗
PubMed1986

Comparison of the strengths of aluminous porcelain fired on to platinum and palladium foils.

The disc strengths of aluminous porcelain fired on to both platinum and palladium foil matrices have been determined. Also, the effect on strength of removing the matrices has been measured. The appearance of the separated metal and porcelain surfaces has been studied using scanning electron microscopy, and energy dispersive X-ray analysis has been used to evaluate the chemical composition of these surfaces. Reasons for the increase in strength observed when the matrix is left intact are discussed. Practical suggestions for obtaining stronger jacket crowns are presented.

Aluminum↗
PubMedDate not supplied

Lithium ion strengthening of dental porcelain.

The effects of experimental lithium-containing ion exchange pastes on dental porcelain were compared with a commercial ion strengthening paste. Maximum biaxial flexure strength using the experimental pastes was obtained by firing lithium paste containing 200 g per L lithium sulphate dihydrate for 45 minutes at 750 degrees C onto the surface of the porcelain. However, the commercial paste produced the greatest strengthening overall.

Aluminum Oxide↗
PubMedDate not supplied

An investigation of an ion strengthening paste for dental porcelains.

The effect of a commercial ion exchange paste on the tensile strength of high- and low-expansion dental porcelains was investigated. Strength measurements were correlated with changes in surface chemistry. The paste was found to be more effective for aluminous porcelains than for an inlay ceramic, although only when applied to the surface placed in tension. Surface finish also influenced the effectiveness of the paste. The depth of ion exchange was assessed by energy dispersive x-ray analysis and was found to extend to at least 100 microns, although the most marked change occurred within a 10-microns layer below the surface.

Aluminum Oxide↗
PubMedDate not supplied

Production of bioceramic surfaces with controlled porosity.

The inability to precisely control pore morphology has limited investigations into the exact geometric requirements for optimum ingrowth of bone into porous ceramic implants. A laser machining technique was used to create regular arrays of tubular pores with opening diameters of 75 and 150 microns in sintered hydroxyapatite specimens. Scanning electron microscopy revealed that the size of pores produced in this way is highly reproducible. Heat from the laser beam appeared to produce a fused layer of material, approximately 6 microns thick, around each pore. The nature of this altered material was studied using x-ray diffractometry.

Bioprosthesis↗