Tyrosine-derived polycarbonate membrane in treating mandibular bone defects. An experimental study

Abstract

This study was designed to evaluate the suitability of a novel bioabsorbable material in treating bone defects. A poly(desaminotyrosyl-tyrosine-ethyl ester carbonate) (PDTE carbonate) membrane (thickness 0.2-0.3 mm) was implanted into the mandibular angle of 20 New Zealand White rabbits to cover a through-and-through defect (12 x 6 mm). In group 1, the defects were left unfilled but covered with membrane and in group 2 the defects were filled with bioactive glass mesh and covered with membrane, too. Controls were left uncovered and unfilled. The animals were followed for 6, 12, 24 and 52 weeks, respectively. The material was evaluated by qualitative analysis of histological reactions and newly formed bone. We found that PDTE carbonate elicited a modest foreign body reaction in the tissues, which was uniform throughout the study. New bone formation was seen in all samples after six weeks. Group 1 had more new bone formation until 24 weeks and after this the difference settled. Based on findings of this study it was concluded that PDTE carbonate membranes have good biocompatibility and are sufficient to enhance bone growth without additional supportive matrix.

Figure 1

The defect before placement of the PDTE carbonate membrane.

Figure 2

Schematic of the defect site. The box at the bottom indicating the removed piece of bone.

Figure 3

Folded PDTE carbonate membrane before implantation.

Figure 4

The PDTE carbonate membrane has become surrounded with bone after 12 weeks of healing. Note the absent foreign-body reaction with giant cells to the implant. In the surrounding capsule only fibroblasts are seen. The formed fibrous capsule is less than 100 μm thick where fixation has been adequate. Arrow up indicating the membrane, arrow right the bone and arrow left fibrous capsule.

Figure 5

Control radiographs (a) without membrane treatment and (b) with BAG treatment only after 52 weeks. At both radiographs edges of the defects are rounded and original bony contour is not achieved.

Figure 6

At this 24-week sample, the formed fibrous capsule between surrounding the PDTE membrane is over 100 μm thick possibly due the inadequate fixation of the membrane. Also no foreign body reaction with giant cells is seen in this sample. Arrow up indicating the membrane, arrow right the bone and arrow left fibrous capsule.