Implants, resorbable

Health Safety. PET fibers pose no health risk to humans or animals. Eibers have been used extensively iu textiles with no adverse physiological effects from prolonged skin contact. PET has been approved by the U.S. Eood and Dmg Administration for food packagiug and botties. PET is considered biologically iuert and has been widely used iu medical iaserts such as vascular implants and artificial blood vessels, artificial bone, and eye sutures (19). Other polyester homopolymers including polylactide and polyglycoHde are used iu resorbable sutures (19,47). 

The concept of using biodegradable materials for implants which serve a temporary function is a relatively new one. This concept has gained acceptance as it has been realized that an implanted material does not have to be inert, but can be degraded and/or metabolized in vivo once its function has been accompHshed (12). Resorbable polymers have been utilized successfully in the manufacture of sutures, small bone fixation devices (13), and dmg dehvery systems (qv) (14). 

Other Ceramic Calcium Phosphate Materials. Other ceramic calcium phosphate materials for repairing bony defect iaclude p-tricalcium phosphate (P-TCP) [7758-87-4], P-Ca2(PO, and biphasic calcium phosphate (BCP) ceramics which consist of both P-TCP and HA. Unlike ceramic HA, P-TCP resorbs ia the tissue (293). The in vivo dissolution of BCP ceramic implants was shown (296) to iacrease with increasing P-TCP/HA ratio ia the implants. Both P-TCP and BCP can lead to new bone growth to various extents depending on the appHcations and the type of materials used (293,296). 

Miller, R. A., Brady, J. M., and Cutright, D. E., Degradation rates of oral resorbable implants (polylactates and poly-glycolates) Rate modification with changes in PLA/PGA copolymer ratios, J. Biomed. Mater. Res., 11, 711, 1977. 

Abbushi A et al (2008) Regeneration of intervertebral disc tissue by resorbable cell-free polyglycolic acid-based implants in a rabbit model of disc degeneration. Spine 33(14) 1527-1532... 

Our researchers have worked very hard to accomplish our goals by doing things we felt would enhance our synthetic bone materials and their performance to enable them to equal and often exceed the performance of autograft as implants as well as in other types of bone augmentation and replacement. The nonporous tooth enamel solid calcium phosphate materials have flexural strengths of over 20,000 lb in.2 However, without pores it would take an extremely long time to resorb this nonporous bioceramic. 

The developmental effects of 1,4-dichlorobenzene have been evaluated in New Zealand White rabbits (Hayes et al. 1985). Pregnant rabbits were exposed to 1,4-dichlorobenzene by inhalation at 800 ppm for 6 hours per day on Gd 6-18. At 300 ppm, there was a significant increase in the number of litters with resorptions and the percentages of resorbed implantations per litter however, this effect was not seen at 800 ppm and was thus probably not treatment-related. An increased incidence of retroesophageal right subclavian artery present in the offspring was noted it was not considered to constitute a teratogenic response to exposure to 1,4-dichlorobenzene, but was considered only a minor variation. Based on the NOAEL of 300 ppm, an acute-duration MRL of 0.8 ppm was calculated as described in the footnote to Table 2-1 and Appendix A (Hayes et al. 1985). 

The uterus and its contents should also be examined prior to parturition to determine the number of live young and dead embryos and fetuses. The sum of these values equals the number of implantation sites. If the corpora lutea are counted (this may be very difficult in mice), then the difference between the number of implants and the number of corpora lutea indicates the extent of preimplantation loss. However, this is not necessarily accurate if the dam is dosed at the time of implantation, because it is possible to interfere with implantation to the extent that no visible sign remains. The difference between the total number of implants and the number of live implants gives the postimplantation loss, subject to the same caution as above. If there are no signs of implantation, the uterus can be stained with ammonium sulfide (Saleweski, 1964), which reveals completely resorbed implantation sites. The difficulty of distinguishing between preimplantation loss and very early postnatal implantation loss emphasizes the necessity of evaluating both parameters. 

Despite advances in hepatocyte culture, tissue engineering of the liver faces significant challenges.One important factor in the development of a self-sufficient hepatic device is vascularization. While in the early stages of development, a device can be maintained by providing sufficient void volume the device ultimately will have to provide for natural supplies of raw materials. This is one of the factors that makes the development of a biodegradable implanted device problematic. Not only must the so-called biodegradable scaffold (and its associated problems) be resorbed... 

Implants made of TCP and, to some extent, also of HA are partly resorbed after the implanta-tion. This may take place cellularly, in which case the material will be incorporated into the normal physiological process of making and breaking down bone. This phenomenon promotes the formation of new bone material and the strong connection between the rest of the implant and the living tissue. By immersing the bio-material into the patient s osteoblasts (= self bone cells) which have been cultivated in vitro, we can stimulate these processes. 

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