The aim of this prospective pilot study is to find answers to the following question: In the treatment protocol of open membrane technique defined by Funakoshi, do the histological and biological properties of the tissue that has already covered the graft surface following the removal of the d-PTFE membrane resemble those properties of induced membrane?

4 male, white Vienna rabbits were used for experiments. Bicortical and 10mm in diameter four bone defects were created on each calvarial bone. 2 rabbits (8 defects) were accepted as group I and other 2 rabbits (8 defects) were accepted as group II. Bone cement was placed into the all-defect in group I. 8 defects were filled with Bi-Oss graft material and covered with d-PTFE membranes in group II. After 8 weeks, sacrifice of the rabbits was performed. In group I, without damaging the formed membrane around it, the bone cement was removed from the defects and the achieved membrane was sent to the pathology department. In group II, the thin film layer that formed under the d-PTFE membrane was sent for histological evaluations. Inflammation, edema, foreign body reaction, synovial-like epithelium existence, thickness, vascularisation (CD31, VEGF), fibrosis were assessed.

Inflammation, fibrosis and thickness measurements are significantly different between the groups (P<0,05) and for these parameters, the mean of d-PTFE group (Group II) is significantly higher than the mean of the induced-membrane group (Group I). There isn’t any significant difference for other parameters.

The morphological characteristics of membranes of the two groups were similar. There was a cell-rich, vascularised tissue with fibrous structures; fibroblasts, myofibroblast, and collagen, orientated parallel to the cement.