Efficacy of high-density versus semipermeable PTFE membranes in an elderly experimental model

Objective. The clinical effectiveness of expanded polytetrafluoroethylene (PTFE) membranes for guided bone regeneration has been reported in the literature on several occasions. However, one major drawback of this material is the need for a second surgical operation For removal of the membrane. In addition, most studies involving guided bone regeneration in animal models have used young animals or animals of unspecified age, but in some clinical situations guided bone regeneration may be indicated in elderly jaw bones. The objectives of this investigation were (1) to evaluate the effectiveness of a newly introduced high-density PTFE membrane (TetGen-FD)-a material that does not require second-stage surgery for its removal-for enhancement of bone ingrowth in elderly rabbits' calvaria and (2) to compare the findings with those obtained with the commonly used semipermeable expanded PTFE membrane (Gore-Tex). Study design. Eighteen elderly rabbits (each more than 30 months old) served as the experimental animals in this study. Two non-self-healing. full-thickness defects were created in each rabbit calvarium. One of the 2 defects was fully covered with macroprous expanded PTFE membrane (Gore-Tex); the ether defect was covered with microporous PTFE membrane (TefGen-FD). Specimens were obtained at 4, 8, and 16 weeks and examined by means of light microscopy. Results. Clinically, the high-density TefGen membrane was much easier to detach from the underlying bone than was the semipermeable Gore-Tex membrane, which showed strict adherence to bone surface on removal. Microscopically, the Gore-Tex membrane lamellae were infiltrated by fibro-osseous tissue at the membrane's lower surface. A relatively greater speed and quantity of bone regeneration were observed in the defective cavities covered with Gore-Tex membrane than in those covered with TefGen membrane. Conclusions. It appears that the semipermeable Core-Tex membrane is more effective than the high-density TefGen-FD membrane with respect to guided bone regeneration in elderly bone. These findings have relevance for the clinical situation of using guided bone regeneration in conjunction with implant placement and ridge augmentation procedures in atrophic elderly jaws.