In vitro and in vivo evaluations of a novel post-electrospinning treatment to improve the fibrous structure of chitosan membranes for guided bone regeneration.

Electrospun chitosan membranes have been investigated for guided bone regeneration but are susceptible to swelling, dissolution, and loss of biomimetic nanofiber structure due to residual acid salts. A novel process was investigated for acidic salt removal from chitosan electrospun in 70% trifluoroacetic acid (TFA) by treating with triethylamine (TEA)/acetone and di-tert-butyl dicarbonate (tBOC) instead of the common Na2CO3 treatment. TFA salt removal and nanofiber structure stabilization were confirmed by EDS, FTIR, 19F NMR and electron microscopy before and after soaking in water. Membrane degradation after 4 weeks in PBS with 100 µg ml-1 lysozyme and osteoblastic proliferation were similar between TEA/tBOC-treated and Na2CO3-treated membranes. A simulated surgical tear test using surgical tacks showed that the peak tensile tear strength of the TEA/tBOC-treated chitosan membranes (62.1 ± 1.9 N mm-1) was significantly greater than a commercial polylactic acid (PLA) membrane (13.4 ± 0.4 N mm-1), similar to one commercial collagen membrane (55.3 ± 7.5 N mm-1) but lower than another commercial collagen membrane (133.9 ± 21.5 N mm-1). Rat 8 mm critical-sized calvarial defects covered with TEA/tBOC-treated chitosan membranes prevented soft tissue infiltration and supported new bone growth (15.76 ± 10.28%) similar to a commercial collagen membrane (16.08 ± 10.69%) at 12 weeks based on microCT analyses. Hence our novel TEA/tBOC process significantly improved nanofiber structure and mechanical strengths of electrospun chitosan membranes as compared to Na2CO3 treated membranes, without affecting in vitro degradation or cytocompatibility, improved membrane mechanical properties to be greater than a commercial PLA membrane and to be in range of commercial collagen membranes and supported calvarial bone defect healing similar to collagen. Thus TEA/tBOC-treated chitosan membranes exhibit many characteristics and properties that strongly support their potential for use in guided bone regeneration.

Novel naturally crosslinked electrospun nanofibrous chitosan mats for guided bone regeneration membranes: material characterization and cytocompatibility.

Guided bone regeneration (GBR) barrier membranes are used to prevent soft tissue infiltration into the graft space during dental procedures that involve bone grafting. Chitosan materials have shown promise as GBR barrier membranes, due to their biocompatibility and predictable biodegradability, but degradation rates may still be too high for clinical applications. In this study, chitosan GBR membranes were electrospun using chitosan (70% deacetylated, 312 kDa, 5.5 w/v%), with or without the addition of 5 or 10 mm genipin, a natural crosslinking agent, in order to extend the degradation to meet the clinical target time frame of 4-6 months. Membranes were evaluated for fibre diameter, tensile strength, biodegradation rate, bond structure and cytocompatibility. Genipin addition, at 5 or 10 mm, resulted in median fibre diameters 184, 144 and 154 nm for uncrosslinked, 5 mm and 10 mm crosslinked, respectively. Crosslinking, examined by Fourier transform infrared spectroscopy, showed a decrease in N-H stretch as genipin levels were increased. Genipin-crosslinked mats exhibited only 22% degradation based on mass loss, as compared to 34% for uncrosslinked mats at 16 weeks in vitro. The ultimate tensile strength of the mats was increased by 165% to 32 MPa with 10 mm crosslinking as compared to the uncrosslinked mats. Finally, genipin-crosslinked mats supported the proliferation of SAOS-2 cells in a 5 day growth study, similar to uncrosslinked mats. These results suggest that electrospun chitosan mats may benefit from genipin crosslinking and have the potential to meet clinical degradation time frames for GBR applications.

Evaluation of biocompatibility and degradation of chitosan nanofiber membrane crosslinked with genipin.

Chitosan, a natural polysaccharide, has demonstrated potential as a degradable biocompatible guided bone regeneration membrane. This study aimed to evaluate the in vivo biocompatibility and degradation of chitosan nanofiber membranes, with and without genipin crosslinking as compared with a commercial collagen membrane in rat model. Chitosan nanofiber membranes, with and without genipin crosslinking, and collagen membrane (control) were implanted subcutaneously in the backs of 30 rats. The membranes were analyzed histologically at 2, 4, 8, 12, 16, and 20 weeks. Sections were viewed and graded by a blinded pathologist using a 4-point scoring system (0 = absent, 1 = mild, 2 = moderate, and 3 = severe) to determine the tissue reaction to the membranes and to observe membrane degradation. There was no statistically significant difference in histological scores among chitosan and collagen membranes at different time points. Absence or minimal inflammation was observed in 57-74% of the membranes across all groups. Most chitosan membranes persisted for 16-20 weeks, whereas most collagen membranes disappeared by resorption at 12-16 weeks. The general tissue response to chitosan nanofiber membranes with and without genipin crosslinking, was similar to that of control commercial collagen membrane. However, the chitosan membranes exhibited slower degradation rates than collagen membranes.

Short-term objective and subjective evaluation of small-diameter implants used to support and retain mandibular prosthesis.

BACKGROUND: The introduction of small-diameter implants has provided dentists the means of providing edentulous and partially edentulous patients with immediate functioning transitional prostheses while definitive restorations are being fabricated. The successful use of these small-diameter implants for temporary stabilization of prostheses has led many clinicians to explore the option of using them as a definitive alternative, especially as the technique requires minimal time and also is economical for the patients. To date, there has been no study with multiple patients looking at both the subjective and objective outcomes of these small-diameter implants. MATERIALS AND METHODS: Twenty-seven edentulous patients were enrolled in this study, seven of them were smokers. One-hundred and eight small-diameter (2.0 mm, MDL) implants were surgically placed in 24 edentulous mandibles. All implants were immediately loaded. The patients filled out a screening questionnaire and four subsequent questionnaires to test their satisfaction with the altered prosthesis at 6, 12, 18 and 24 months. The survival of the implants was also noted. RESULTS: Smokers had an implant survival of 79%. Non-smokers had an implant survival of 100%. The results of the questionnaire indicated an overall satisfaction with the implant-supported prosthesis.

Emerging antibacterial biomaterial strategies for the prevention of peri-implant inflammatory diseases.

PURPOSE: Peri-implantitis is an inflammatory disease due to bacteria and plaque formation on implant surfaces which can lead to bone resorption and loss of osseointegration. Biomaterial strategies to prevent or eliminate initial bacterial attachment, in favor of host tissue attachment may have a positive effect on decreasing peri-implantitis, particularly for at risk patient groups. This study provides a brief overview of some of the experimental biomaterial strategies aimed at suppressing or inhibiting bacterial colonization of implant surfaces in favor or host cells and tissues. MATERIALS AND METHODS: These biomaterial strategies have different mechanisms of action from interfering with bacterial adhesion by modifying surface energies, immobilizing antimicrobials on implant surfaces, creating photocatalytic surfaces, as well as modifying surfaces to deliver antimicrobial agents either prophylactically or in response to bacterial challenge. This is not a comprehensive review, rather a review of studies that serve to illustrate many of the different approaches being investigated. RESULTS: While many of these strategies have demonstrated the potential to significantly reduce bacterial attachment on implant surfaces in vitro, it is unclear if these same reductions will be adequate clinically since even a few adhering bacteria may over time develop into inflammatory inducing biofilms or plaque. Also, data on the ability of the antibacterial modified biomaterials to support osseointegration and permuosal seal formation is still needed. CONCLUSION: Given the complex and multivariate causes of peri-implant disease, it is likely that combinations of these strategies (eg, antimicrobial surfaces and or delivery mechanisms coupled with methods to favor stable osseointegration and permucosal seal) will be most effective in developing implants resistant to peri-implant disease.