A Human Whole Blood Culture System Reveals Detailed Cytokine Release Profiles of Implant Materials.

Introduction: Common in vitro cell culture systems for testing implant material immune compatibility either rely on immortal human leukocyte cell lines or isolated primary cells. Compared to in vivo conditions, this generates an environment of substantially reduced complexity, often lacking important immune cell types, such as neutrophil granulocytes and others. The aim of this study was to establish a reliable test system for in vitro testing of implant materials under in vivo-like conditions. Methods: Test materials were incubated in closed, CO2-independent, tube-based culture vessels containing a proprietary cell culture medium and human whole blood in either a static or occasionally rotating system. Multiplex cytokine analysis was used to analyze immune cell reactions. Results: To demonstrate the applicability of the test system to implant materials, three commercially available barrier membranes (polytetrafluoroethylene (PTFE), polycaprolactone (PCL) and collagen) used for dental, trauma and maxillofacial surgery, were investigated for their potential interactions with immune cells. The results showed characteristic differences between the static and rotated incubation methods and in the overall activity profiles with very low immune cell responses to PTFE, intermediate ones to collagen and strong reactions to PCL. Conclusion: This in vitro human whole blood model, using a complex organotypic matrix, is an excellent, easily standardized tool for categorizing immune cell responses to implant materials. Compared to in vitro cell culture systems used for materials research, this new assay system provides a far more detailed picture of response patterns the immune system can develop when interacting with different types of materials and surfaces.

Physicochemical characterization of barrier membranes for bone regeneration.

Barrier membranes are essential biomaterials for guided bone regeneration. Due to different origin and structure of barrier membranes, singular mechanical properties and clinical behaviors can be expected. It is important to understand the physic and chemical properties of barrier membranes to select the needed biomaterial for each clinical situation. To date, no study has evaluated and compared the physicochemical properties of various families of barrier membranes. The aim of this study is to evaluate the physicochemical properties of various barrier membranes. Fifteen membranes of different origin were tested in this study. Membranes were divided into biological or synthetic origin and grouped in natural allogenic collagen, natural xenogenic collagen, cross-linked collagen and synthetic membranes. Physicochemical properties were evaluated in terms of tension, stiffness, absorption ability, pH and wettability. For the tension tests, all membranes showed similar low tension and low stiffness, especially after a 4-min hydration, except for bone laminas that showed a greater stiffness particularly in a dry status. Regarding wettability and hydration of the barrier membranes, porcine origin membranes had greater hydration; wettability was also superior in porcine derived barrier membranes and showed a faster absorption of the drop on the rough surfaces. All membranes had a stable pH, having the synthetic membranes the most stable pH when compared to physiologic. The wide variety of barrier membranes opens a debate in which the practitioner should select the adequate barrier membrane for each clinical situation. Different materials show singular potentials depending on their tissue origin making them suitable for specific clinical indications. More studies regarding adsorption, integration and degradation of barrier membranes are needed to understand their behavior.

Adsorption and release kinetics of growth factors on barrier membranes for guided tissue/bone regeneration: A systematic review.

OBJECTIVES: Guided bone / tissue regeneration (GBR/GTR) procedures are necessary to improve conditions for implant placement. These techniques in turn can be enhanced by using growth factors (GFs) such as bone morphogenetic protein (BMP-2) and platelet-derived growth factor (PDGF) to accelerate regeneration. The aim of the present systematic review was to evaluate the GF loading and release kinetics of barrier membranes. STUDY DESIGN: A total of 138 articles were screened in PubMed databases, and 31 meeting the inclusion criteria were included in the present systematic review. RESULTS: All the articles evaluated bio-resorbable membranes, especially collagen or polymer-based membranes. In most studies, the retention and release kinetics of osteogenic GFs such as BMP-2 and PDGF were widely investigated. Growth factors were incorporated to the membranes by soaking and incubating the membranes in GF solution, followed by lyophilization, or mixing in the polymers before evaporation. Adsorption onto the membranes depended upon the membrane materials and additional reagents such as heparin, cross-linkers and GF concentration. Interestingly, most studies showed two phases of GF release from the membranes: a first phase comprising a burst release (about 1 day), followed by a second phase characterized by slower release. Furthermore, all the studies demonstrated the controlled release of sufficient concentrations of GFs from the membranes for bioactivities. CONCLUSIONS: The adsorption and release kinetics varied among the different materials, forms and GFs. The combination of membrane materials, GFs and manufacturing methods should be considered for optimizing GBR/GTR procedures.

On the search of the ideal barrier membrane for guided bone regeneration.

BACKGROUND: GBRs are essential procedures in implant dentistry and periodontology where barrier membranes play an important role by isolating soft tissue and allowing bone to grow. Not all membranes function the same way, as they differ from their origin and structure, it is important to understand how membranes behave and differ one from others in order to achieve a predictable treatment. MATERIAL AND METHODS: A systematic search on Medline by two independent reviewers was performed for articles published until July 2017 reporting the characteristics or properties of barrier membranes. The question that preceded the search was designed according to PICO rules. RESULTS: A total of 124 articles were initially identified from electronic searching. After abstract/full-text review, 21 were included for a systematic review. According to the extracted data and article analysis, barrier membranes should fulfill the following criteria in order to success: biocompatibility, space maintaining, occlusive function, easy - handling and a bioactivation friendly property. With the development of new biomaterials and surfaces, a great advance in this area is expected. CONCLUSIONS: It has been clearly described that biocompatibility is the most important requirement to take into account when choosing a membrane, but other factors such as space maintaining capacity, cell oclusiveness, easy handling and bioactivation friendly materials are the ones that will fulfill our necessities. Key words:Barrier membrane, guided bone regeneration, dental implantology, oral surgery, collagen membrane, biomaterial.