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At least 523 records · Page 29Linked to original sources
PubMed1992

Conventional versus high-porosity polytetrafluoroethylene grafts: clinical evaluation.

In baboons, nonreinforced (unwrapped) 60 microns internodal distance polytetrafluoroethylene grafts form a complete endothelial lining within 2 weeks by capillary ingrowth through the wall. Smooth muscle cells then grow under the endothelium and proliferate to form a complete neointima. To determine if spontaneous endothelialization of these grafts can also occur in humans, 10 above-knee femoropopliteal grafts composed of equal lengths of 60 and 30 microns polytetrafluoroethylene were placed in eight patients. These grafts were reinforced (wrapped) for human use. Because biopsy of the grafts was not possible, endothelialization was assessed noninvasively by 111In-labeled platelet imaging 1 week and 3 months after surgery. There was no difference in indium uptake between 60 and 30 microns segments at either time. Histologic sections were available from 60 microns segments of two patients who underwent operation for graft thrombosis. Capillary ingrowth was seen in these grafts, but it rarely extended more than half the distance from the outside of the graft to the lumen. Smooth muscle cells were not seen on the flow surface, indicating that a neointima had not formed. These findings demonstrate that capillary ingrowth can occur in 60 microns grafts in humans but does not produce an endothelial lining. The failure to endothelialize is perhaps a result of inadequacy of angiogenesis in adult humans or retardation of capillary ingrowth by the reinforcing wrap.

Aged↗
PubMedDate not supplied

Porosities in five automixed addition silicone elastomers.

Five automixed and one hand-mixed addition silicones were evaluated by counting the number of voids produced in impressions made. It was concluded that although automixing produced fewer voids than hand-mixing, certain automixed materials were better than others.

Dental Impression Materials↗
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↗
PubMed1991

Dental composite resin porosity and effect on water absorption.

The aims of this study were: 1) to characterize the solubility and water absorption of different composite resins used as dental restorative materials; 2) to analyse their surface morphology using S.E.M. The resins tested were a mixture of glycidyl methacrylate (Bis-GMA) and TEGMA filled with silane-coated particles of inorganic fillers, and Bis-GMA and urethane resin. Cylindrical samples of composite resin were polymerized and stored in distilled water and weighed after different times. SEM analysis demonstrated voids and porous in several samples. The present study shows that dental restorative composite loose a small percentage of their components during storage time and that the type of resin, the nature of fillers and the methods of polymerization greatly influence water uptake and solubility of dental composite resin materials. These findings could explain the loss of anatomic form and the occlusal degradation of dental composites in "in vivo" conditions.

Absorption↗
PubMedDate not supplied

[The determination of the porosity of a basic acrylic plastic by mercury porometry].

A method for estimation of pore sizes in acrylic plastic dentures is described. Size-distribution of pores may be a very informative characteristic of not only strength, esthetic, and hygienic characteristics of dentures, but an indicator of a plastic polymerization process in various humidity and temperature conditions.

Acrylic Resins↗
PubMed1995

Porosity in resin composite core restorations: the effect of manipulative techniques.

Forty acrylic resin duplicates of an endodontically treated and extracted human molar were restored with two resin composite materials for core restorations. Two different manipulation techniques, bulk insertion and syringe application, were used. In a simulated clinical setup, the core buildups produced by the different manipulation techniques were investigated for voids. In 20 duplicates, a post was placed to simulate a metal post and resin composite core buildup. The syringe technique produced significantly fewer incorporated voids for both resin composite core materials than did the bulk insertion technique. It was not possible to demonstrate a relationship between the presence of voids and the presence of a metal post.

Analysis of Variance↗