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PubMed1982

Comments on the porosity of human tooth enamel.

The porous nature of surface and sub-surface enamel undergoing the final stages of maturation has been observed on unerupted, partly-erupted, and fully-erupted human teeth, using polarized light microscopy, microradiography, and scanning electron microscopy. Maturation deficiency of developmental origin can be distinguished from early carious lesions with polarized light by the absence of a well-circumscribed "dark" zone.

Dental Enamel↗
PubMed1981

Experimental study of the influence of porosity on development of neointima in Gore-Tex grafts: a method to increase long-term patency rate.

The objective of this study was to evaluate the controlled microscopic development and fate of the neointima of Gore-Tex graft pretreated with multiple regular perforations, compared to nonperforated controls. Gore-Tex grafts (each 7 cm x 8 mm), perforated at regular 2 mm intervals with a special needle (0.8 mm internal diameter) for one half the length, with the remaining half kept intact, were implanted in 37 canine abdominal aortas in an end-to-end fashion. Standard untreated Gore-Tex grafts, of identical size, were similarly implanted in ten as controls. The perforated portion of the artificially treated Gore-Tex grafts demonstrated early neointimization at one week, the presence of fibroblasts and developing vasovasorum at 4 weeks, and complete endothelialization at 12 weeks. In contrast, the unperforated portion of implanted grafts demonstrated delayed endothelialization, requiring 24 weeks for complete development. Untreated controls demonstrated incomplete healing of the central luminal portion of the graft, with reddish thrombi still present at 24 weeks. Our study demonstrated that the poor development of neointima persists in the central portion of standard Gore-Tex controls in the last postoperative period, while pretreatment with multiple small perforations significantly hastens the development of a smooth neointima.

Animals↗
PubMed1981

Effect of surface porosity on early thrombogenicity using vascular grafts with two surfaces in sequence.

This experiment addresses the multifactorial dilemma of defining the ideal performance parameters of small internal diameter vascular grafts. We found silicone rubber vascular grafts with smooth surfaces remain acutely free of thrombotic deposits whereas grafts with rough surfaces promote a dispersed thrombus formation. This study also questions the concept that the thrombogenicity of one surface determines the thrombotic response of different and adjacent flow surfaces in the blood flow. Here the distinction between response to each surface was abruptly delineated and equal in intensity regardless of proximal or distal positioning. By studying the 2 surfaces in sequence, surface properties were evaluated using the minimal number of experiments by mitigating the effects of interanimal variability. This is an important consideration in an era of "cost accountability".

Animals↗