Expanded polytetrafluoroethylene (e-PTFE) has been used successfully as a membrane barrier for regeneration procedures. However, when exposed to the oral cavity, its high porosity increases the risk of early infection, which can affect surgical outcomes. An alternative to e-PTFE is non-expanded and dense polytetrafluoroethylene (n-PFTE), which results in lower levels of early infection following surgical procedures. The aim of this literature review was to analyze and describe the available literature on n-PFTE, report the indications for use, advantages, disadvantages, surgical protocols, and complications. The medical databases Medline–PubMed and Cochrane Library were searched and supplemented with a hand search for reports published between 1980 and May 2012 on n-PTFE membranes. The search strategy was limited to animal, human, and in vitro studies in dental journals published in English. Twenty-four articles that analyzed the use of n-PTFE as a barrier membrane for guided tissue regeneration and guided bone regeneration around teeth and implants were identified: two in vitro studies, seven experimental studies, and 15 clinical studies. There is limited clinical and histological evidence for the use of n-PTFE membranes at present, with some indications in guided tissue regeneration and guided bone regeneration in immediate implants and fresh extraction sockets.
The first non-resorbable membranes available for dental use were made of expanded polytetrafluoroethylene (e-PTFE). PTFE is a stable polymer, chemically and biologically inert, and able to resist enzymatic and microbiological attack. Expanded membranes have been applied widely in periodontal and bone regeneration. It has been documented that their use predictably leads to successful regeneration.
A common feature of the majority of existing synthetic membranes, such as e-PTFE, is macroporosity, which is believed to enhance regeneration by improving wound stability. One of the main drawbacks of e-PTFE is that an early bacterial infection can occur, affecting the outcomes of the regeneration. The e-PTFE membranes and the resorbable membranes classically require soft tissue coverage or primary closure to prevent soft tissue ingrowth, bacterial contamination, infection, membrane migration, early membrane degradation, and graft exposure.
High-density polytetrafluoroethylene membranes (n-PTFE) offer an alternative to e-PTFE or resorbable membranes. The n-PTFE membrane is made of 100% pure medical-grade bio-inert PTFE, which is non-porous, dense, non-expanded, and non-permeable. The thickness of the different commercially available membranes ranges from 0.13 to 0.25 mm and their low porosity ranges from 0.2 to 0.3 μm; e-PTFE membranes have a similar thickness but a higher porosity (5–30 μm). The indications for the use of n-PTFE are similar to those for e-PTFE, but their properties allow no primary closure.
n-PTFE membranes currently available are: Cytoplast Regentex TXT-200, GBR-200, and Ti-250 Titanium-Reinforced (Osteogenics Biomedical Inc., Lubbock, TX, USA). All these membranes are made of 100% pure high-density PTFE with low porosity and are available in different sizes, textures (textured and non-textured), and with or without titanium reinforcement.
The aim of this literature review was to analyze and describe the available literature related to n-PTFE membranes in guided bone regeneration (GBR) and guided tissue regeneration (GTR) approaches, attempting to report the indications for use, advantages, disadvantages, surgical protocols, and complications. An answer to the following question was sought: ‘What are the clinical indications, limitations, advantages, and protocols for the use of n-PTFE membranes in GBR and GTR procedures?’
Materials and methods
The medical databases Medline–PubMed and Cochrane Library were searched for reports published between 1980 and May 2012 on dense PTFE membranes used in GTR and GBR procedures (ridge preservation and ridge augmentation). The search strategy was limited to animal, human (randomized clinical trials (RCT), controlled clinical trials, prospective and retrospective studies, case series, and case reports), and in vitro studies in dental journals published in English, using the following key words: high-density PTFE, dense PTFE, non-expanded PTFE, non-porous PTFE, microporous PTFE, and non-permeable PTFE. The electronic search was supplemented with a hand search of the following publications: International Journal of Periodontics and Restorative Dentistry , International Journal of Oral and Maxillofacial Implants , Journal of Periodontology , Implant Dentistry , Dentistry Today , Journal of Oral Implantology , Quintessence International , International Journal of Oral and Maxillofacial Surgery, Medicina Oral Patologia Oral y Cirugia Bucal , Journal of Periodontal and Implant Science , Clinical Oral Implants Research , and Journal of Clinical Periodontology . Two reviewers (JMC, ISM) performed the electronic and hand searches using the above-mentioned inclusion criteria. Articles were first screened by title and abstract. A full text reading of all selected articles was further conducted. Disagreement between the two reviewers was resolved by consensus. If an agreement could not be reached, a third reviewer (JN) was consulted.
The search strategy resulted in 46 articles: 35 were retrieved by electronic search and 17 by hand search; six duplicate articles were excluded. After the initial screening phase 26 articles were eligible for full text reading and all of them met the required inclusion criteria. Finally, 24 articles were selected for the literature review ( Fig. 1 ). Two reports were excluded after a consensus between the three reviewers. One article was excluded because the clinical cases were treated indistinctly with collagen and n-PTFE membranes limiting the real results obtained with n-PTFE membranes, and the other because it could not be retrieved.
The search protocol identified 24 reports with evidence of the use of n-PTFE as a barrier membrane for GTR and GBR around teeth and implants: two in vitro studies, seven experimental studies, and 15 clinical studies. Evidence of the clinical use of n-PTFE as a GTR membrane was found in two clinical studies, as GBR in extraction sockets as a ridge preservation technique in 10 clinical studies, and around immediate implants in nine clinical reports. It has also been tested in seven experimental studies: four of them in a rat model, two in rabbits, and one in dogs. Furthermore, two in vitro studies were found.
In vitro studies ( Table 1 )
Colonization and adherence of periodontopathic bacteria around different membrane configurations has been studied widely and has been reported to be different depending on the membrane used. Sela et al. reported that periodontal bacteria ( Aggregatibacter actinomycetemcomitans (Aa), Treponema denticola (Td), and Porphyromonas gingivalis (Pg)) showed significantly greater adherence to the bioabsorbable collagen membranes than to the Teflon membranes (n-PTFE and e-PTFE), showing no significant differences between the adhesion properties of the two types of synthetic membrane.
|Sela et al. 1999||In vitro||Adherence of three periodontopathic bacteria (Aa, Td, Pg) to different barriers||Collagen vs. n-PTFE a vs. e-PTFE||• Bacteria showed greater adhesion capacity to collagen membranes
• No differences between the adhesion properties of n-PTFE and e-PTFE
|Kasaj et al. 2008||In vitro||Determination of biological effects of six membranes||n-PTFE a , b , c ( n = 3) vs. collagen membranes ( n = 3)||• Bioabsorbable membranes demonstrated to be more suitable to stimulate cellular proliferation compared to non-resorbable membranes|
However, Kasaj et al. demonstrated that the bioabsorbable membranes are more biocompatible and suitable to stimulate cellular proliferation compared to non-resorbable membranes (n-PTFE). Therefore, n-PTFE materials may be less biocompatible and responsible for impaired tissue integration in vivo in comparison to collagen membranes. Although minimal tissue integration to n-PTFE membranes may be an advantage for membrane retrieval, this may also create potential problems for initial clot formation, wound stabilization, and membrane stability.
Experimental studies ( Table 2 )
The first study of n-PTFE was reported in 1995 by Bartee and Carr, evaluating the stability and efficacy of n-PTFE membranes to facilitate GBR in experimental non-healing bone defects in the rat mandible. Histologically, osteogenic tissue was observed to completely bridge the defect by 2 weeks, and osteogenic repair at the margins of the defects, with islands of woven bone seen in the central areas, was observed by 6 weeks. Clinically, at 6 and 10 weeks the defects were completely filled with a hard, bone-like tissue and the membrane was adherent to the underlying bone, but was easily removed.
|Bartee and Carr 1995||Experimental: 12 adult Sprague-Dawley rats||GBR in bone defects in the mandible||n-PTFE a vs. control (no membrane)||• At 6 and 10 weeks the defects were completely filled with a hard, bone-like tissue
• The membrane was adherent to the underlying bone, but was easily removed
|Crump et al. 1996||Experimental: 30 adult Sprague–Dawley rats||GBR in bone defects in calvaria||n-PTFE a vs. e-PTFE vs. absorbable polylactic acid/citric acid ester base vs. control (no membrane)||• At 2 weeks: greater bone formation for n-PTFE membrane
• At 4 weeks: e-PTFE presented more bone formation than n-PTFE
• Removal forces for n-PTFE were less than for e-PTFE
• No differences in osseous healing and degree of fill between e-PTFE and n-PTFE and control group
|Marouf and El-Guindi 2000||Experimental: 18 elderly half-lop rabbits||GBR in calvarium bone defects||n-PTFE a vs. e-PTFE||• Reliability and efficacy of e-PTFE are relatively greater than n-PTFE with respect to GBR in elderly bone
• Easier removal for n-PTFE
|de Macedo et al. 2008||Experimental: 16 Wistar rats||GBR in defects in parietal bones||n-PTFE b vs. calcium sulphate barrier||• The PTFE group showed notably quantitative and qualitative superiority of new bone formation
• At 30 days: the defect was partially filled with bone tissue (non-mature bone)
• At 45 days: mature bone with smaller medullar spaces and fibrous connective tissue
|de Macedo et al. 2009||Experimental: five New Zealand rabbits||GBR in partially inserted implants in tibiae||n-PTFE b + titanium plasma-spray vs. n-PTFE + acid-treated implant||• The placement of implants protruding 3 mm from crestal bone defects may result in vertical bone augmentation using an n-PTFE barrier|
|Monteiro et al. 2010||Experimental: 25 Wistar rats||GBR in the subcutaneous connective tissue||n-PTFE b vs. absorbable polyurethane-derived membrane||• n-PTFE presents good biocompatibility
• Both groups presented moderate initial inflammatory infiltrate with oedema and granulation tissue
|Park et al. 2011||Experimental: four mongrel dogs||GBR in immediate implants (without dehiscence)||n-PTFE a + bone tacks vs. control group (no membrane)||• n-PTFE group: first bone contact on the buccal side was more coronally positioned (0.8 mm) with a 1 mm thicker buccal bone than the control group|