Biomedical subjects

W F Regnault

Publications and source records attributed to W F Regnault.

5 recordsLinked to original sources

PubMed2007

Effect of particle size of an amorphous calcium phosphate filler on the mechanical strength and ion release of polymeric composites.

The random clustering of amorphous calcium phosphate (ACP) particles within resin matrices is thought to diminish the strength of their polymerized composites. The objective of this study was to elucidate the effect of ball-milling on the particle size distribution (PSD) of ACP fillers and assess if improved dispersion of milled ACP in methacrylate resin sufficiently enhanced filler/matrix interactions to result in improved biaxial flexure strength (BFS), without compromising the remineralizing potential of the composites. Unmilled and wet-milled zirconia-hybridized ACP (Zr-ACP) fillers were characterized by PSD analysis, X-ray diffraction, thermogravimetric and chemical analysis, infrared spectroscopy, and scanning electron microscopy. Composite specimens made from a photoactivated, ternary methacrylate resin admixed with a mass fraction of 40% of un-milled or milled Zr-ACP were evaluated for the BFS (dry and wet) and for the release of calcium and phosphate ions into saline solutions. While having no apparent effect on the structure, composition, and morphology/topology of the fillers, milling significantly reduced the average size of Zr-ACP particulates (median diameter, d(m) = 0.9 +/- 0.2 microm) and the spread of their PSD. Better dispersion of milled Zr-ACP in the resins resulted in the improved BFS of the composites, even after aqueous soaking, and also gave a satisfactory ion release profile. The demonstrated improvement in the mechanical stability of anti-demineralizing/remineralizing ACP composites based on milled Zr-ACP filler may be beneficial in potentially extending their dental utility.

Calcium Phosphates↗

PubMed1998

Replacement heart valves and performance standards.

The international use of medical device standards is expanding for both economic and regulatory reasons. It is no longer adequate to have standards that only specify measurement methods and labeling for a product. An effort needs to be put forth between industry, academia and government to promote standards that also include a minimum set of acceptable performance criteria. This will allow for a less subjective evaluation of the conformance of the medical device to the appropriate standard as well as promote a uniform set of minimal performance expectations for a class of products among consumers.

Animals↗

PubMed1994

FDA's requirements for in-vitro performance data for prosthetic heart valves.

The Center for Devices and Radiological Health, Food and Drug Administration, has recently revised its "Replacement Heart Valve Guidance". That document lists the data FDA deems necessary to support the approval of new prosthetic heart valves of all designs, and which should be contained in Premarket Approval Applications for these devices. The Guidance covers detailed data requirements for in vitro, animal, and clinical data. This paper is intended to briefly summarize FDA's requirements for in vitro data, and, for those cases where it may not be obvious, to provide an overview of the significance of these data and how FDA interprets them in the approval decision process.

Biomechanical Phenomena↗

PubMed1987

Review of medical biosensors and associated materials problems.

Developers of biosensors as medical devices are using emerging technologies that incorporate chemical assays with fiber optics and semiconductors. These biosensors will eventually become indwelling catheters for monitoring blood analyte concentrations as well as functioning as controlled feedback elements for artificial organs. Materials used in these devices are subject to problems of manufacture and reliability as well as those induced by the human body's response to these "foreign agents." The Division of Mechanics and Materials Science in the Center for Devices and Radiological Health at the Food and Drug Administration has initiated a program to investigate factors that effect sensitivity, selectivity and reliability of sensors used in biological applications. Our group's principle focus is on sensors of chemical processes. This article is an outgrowth of our research efforts and is a review of some of the technologies that are currently available or becoming available for these applications. The goal of our research is to identify factors that will have an impact on the reliability of long-term implanted medical devices with particular attention to sensors used in feedback-controlled therapeutic systems.

Artificial Organs↗

PubMedDate not supplied

Fracture mechanics principles applied to implant medical devices--a review.

Historically, the fatigue behavior of materials and structures, including biomaterials and implant devices, was analyzed using stress-life (S-N) techniques, i.e. by determining the number of cycles to failure at a calculated peak stress. The development of fracture mechanics technology has made the crack-growth aspect of fatigue analysis a more exact science, providing more precise data on the properties of materials, incorporating more geometric and metallurgical information from the structure, and, in some cases, providing for updated in-service lifetime predictions. Over the past decade, the medical implant industry and researchers have adopted this analytical tool to varying degrees. The result has been the development of some improved materials, operative procedures, and devices, based on a more exact knowledge of the properties most critical to assuring the long-term durability of devices. Examples of the application of fracture mechanics technology to orthopedic and cardiovascular devices and the potential for further applications are reviewed.

Biomechanical Phenomena↗