In vivo degradation of polyurethane foam with 55 wt % polyethylene glycol.

Most topical hemostatic agents are based on animal-derived products like collagen and gelatin. They carry the potential risk of pathogen transmission while adjustments in the production process of these materials are limited. A synthetic hemostatic agent based on polyurethane (PU) and polyethylene glycol (PEG) was developed to overcome these disadvantages. The goal of this study was to compare the degradation process of this biomaterial to collagen and gelatin hemostatic agents. Samples of the test materials were implanted subcutaneously in both rats and rabbits. The animals were sacrificed at certain time intervals up to three years and the explanted samples were microscopically assessed. The histological examination showed a comparable pattern of degradation for the different test materials. Remnants of gelatin and collagen were seen up to 26 and 39 weeks, respectively. For PU, it took up to three years before micro-particles of the material were no longer detected. All biomaterials showed a good biocompatibility and no severe foreign body reactions occurred. The good biocompatibility and predictable pattern of resorption indicate that PU can be used as a topical hemostatic agent. However, a degradation time comparable to collagen and gelatin would be favorable.

Oral biofilm architecture on natural teeth.

Periodontitis and caries are infectious diseases of the oral cavity in which oral biofilms play a causative role. Moreover, oral biofilms are widely studied as model systems for bacterial adhesion, biofilm development, and biofilm resistance to antibiotics, due to their widespread presence and accessibility. Despite descriptions of initial plaque formation on the tooth surface, studies on mature plaque and plaque structure below the gum are limited to landmark studies from the 1970s, without appreciating the breadth of microbial diversity in the plaque. We used fluorescent in situ hybridization to localize in vivo the most abundant species from different phyla and species associated with periodontitis on seven embedded teeth obtained from four different subjects. The data showed convincingly the dominance of Actinomyces sp., Tannerella forsythia, Fusobacterium nucleatum, Spirochaetes, and Synergistetes in subgingival plaque. The latter proved to be new with a possibly important role in host-pathogen interaction due to its localization in close proximity to immune cells. The present study identified for the first time in vivo that Lactobacillus sp. are the central cells of bacterial aggregates in subgingival plaque, and that Streptococcus sp. and the yeast Candida albicans form corncob structures in supragingival plaque. Finally, periodontal pathogens colonize already formed biofilms and form microcolonies therein. These in vivo observations on oral biofilms provide a clear vision on biofilm architecture and the spatial distribution of predominant species.

Closure of oroantral communications using biodegradable polyurethane foam: a long term study in rabbits.

An oroantral communication (OAC) is an open connection between the oral cavity and maxillary sinus. Closure of OACs is commonly performed with a surgical procedure using a mucoperiosteal flap. An alternative technique using synthetic biodegradable polyurethane (PU) foam for closure of OACs is presented. This PU foam is composed of hard urethane segments, and soft segments made of D/L lactide (50/50), epsilon-caprolactone, and 5% polyethyleneglycol (PEG). To evaluate the use of PU foam for this application, OACs were created in the edentulous part of the maxilla in 21 rabbits, after which PU foams were fitted in the defects. Results showed complete healing of the oral mucosa after 4-10 weeks, healing of the antral mucosal lining after 6 months and complete bony regeneration after 1 year. No reopening of the defects occurred and no maxillary sinusitis was observed. Degradation of the PU foam had not yet reached completion 1 year after implantation. In conclusion, PU foam with 5% PEG provides adequate closure of an OAC in the rabbit model to support healing of the oral and maxillary sinus mucosa. Longer time intervals are needed to assess the complete degradation of the PU foam.

Nonsurgical closure of oroantral communications with a biodegradable polyurethane foam: A pilot study in rabbits.

PURPOSE: Surgical closure of oroantral communications (OACs) has several disadvantages. An animal study was performed to test whether OACs can be closed nonsurgically with a biodegradable polyurethane (PU) foam. MATERIALS AND METHODS: In 6 rabbits, an OAC was created on both sides of the maxilla. Three rabbits were used to evaluate the animal model by applying a surgical treatment on 1 side and by leaving the other defects untreated. In the 3 other rabbits, OACs were closed with PU foam. Wound healing was evaluated clinically and histologically. RESULTS: The surgically treated defects healed without complications. The untreated defects showed complicated and delayed healing. Healing of the foam-treated OACs was dependent on the type of foam that was used. CONCLUSIONS: The rabbit is a suitable animal model for OAC investigations. It is possible to close an OAC with a biodegradable PU foam. Further research is needed to show the most suitable composition of the PU for this purpose.