INTERFACIAL BEHAVIOR OF PEO PBT COPOLYMERS (POLYACTIVE(R)) IN A CALVARIAL SYSTEM - AN IN-VITRO STUDY/

Polyactive(R), a polyethylene oxide/polybutylene terephthalate (PEO/PB T) copolymer, has been reported to display bone-bonding behavior. Alth ough a detailed description of the in vivo bone/Polyactive(R) interfac e is available, the underlying bone-bonding mechanism is still largely unknown. In this in vitro study, a calvarial envelope method has been adopted to reproduce the in vivo bone-bonding phenomenon and subseque ntly to obtain information on the biological effect of varying PEO/PBT segment ratios. The following PEO/PBT ratios were examined: 70/30,60/ 40, 55/45, 40/60, and 30/70. Light microscopy (LM) and scanning (SEM), transmission (TEM), and backscatter electron microscopy (BSE), as wel l as X-ray microanalysis (XRMA), were employed. Within the period of a nalysis (3 weeks), an intimate contact between mineralized deposition and the 70/30, 60/40, and, to a lesser extent, the 55/45 surface was o bserved. Calcified areas developed within the surface of these PEO/BPT proportions during the culture period. Needle-shaped crystals from th e mineralized tissue compartment and from calcified areas within the m aterials surface were intermingled at the interface, providing a morph ologic continuity. A cellular layer was interposed with the mineraliza tion front and the noncalcified 40/60 and 30/70 substrates. Apparently , the percentage of PEO is important for calcification within the near surface of the polymer. This relation is such that the higher the PEO content in PEO/PBT ratios, the more rapid the calcification. The occu rrence of material calcification is considered to be largely responsib le for the subsequent interfacial interactions. The calvarial envelope culture method allows not only reproduction of the in vivo bone/Polya ctive(R) interface, but also a relatively rapid differentiation within the range of PEO/PBT ratios. It was therefore concluded that this in vitro system is suitable for further studies toward a better understan ding of the bone/Polyactive(R) interfacial composition and the underly ing mechanisms. (C) 1994 John Wiley and Sons, Inc.