Enzymatic degradation of collagen-guided tissue regeneration membranes by periodontal bacteria

Evaluation of Porcine-Derived Collagen Membranes for Soft Tissue Augmentation in the Oral Cavity: An In Vivo Study

The use of porcine-derived collagen membranes (PDCM) to improve intraoral soft tissue rehabilitation remains under investigation. Different degrees of crosslinking have yielded differences in resorption time and inflammation surrounding collagen membranes. The aim of this study was to evaluate the in vivo performance of bilayered PDCMs with varying degrees of crosslinking for the regeneration of oral soft tissue defects. Bilateral split-thickness oral mucosa defects were created in mandibles of beagles (n=17) and assigned to one of the following: bilayer PDCM (high crosslinking porcine dermis in sheet form-H-xlink) and (low crosslinking porcine dermis in sheet form-L-xlink), bilayer PDCM (non-crosslinked predicate collagen membrane in spongy form-Ctrl), or negative control (Sham) and compared with positive control (unoperated). Animals were euthanized after 4-, 8-, or 12-weeks of healing to evaluate soft tissue regeneration and remodeling through histomorphometric analyses. H-xlink membranes presented delayed healing with a poorly developed epithelial layer (analogous to the sham group) across time points. Relative to Ctrl at 8 and 12 weeks, defects treated with H-xlink presented no difference in semiquantitative scores ( P > 0.05), while L-xlink exhibited greater healing ( P = 0.042, P = 0.043, at 8 and 12 weeks, respectively). Relative to positive control, L-xlink exhibited similar healing at 8 weeks and greater healing at 12 weeks ( P = 0.037) with a well-developed epithelial layer. Overall, groups treated with L-xlink presented with greater healing relative to the positive control after 12 weeks of healing and may serve as an alternative to autologous grafts for intraoral soft tissue regeneration.

All-in-one porous membrane enables full protection in guided bone regeneration

The sophisticated hierarchical structure that precisely combines contradictory mechanical and biological characteristics is ideal for biomaterials, but it is challenging to achieve. Herein, we engineer a spatiotemporally hierarchical guided bone regeneration (GBR) membrane by rational bilayer integration of densely porous N-halamine functionalized bacterial cellulose nanonetwork facing the gingiva and loosely porous chitosan-hydroxyapatite composite micronetwork facing the alveolar bone. Our GBR membrane asymmetrically combine stiffness and flexibility, ingrowth barrier and ingrowth guiding, as well as anti-bacteria and cell-activation. The dense layer has a mechanically matched space maintenance capacity toward gingiva, continuously blocks fibroblasts, and prevents bacterial invasion with multiple mechanisms including release-killing, contact-killing, anti-adhesion, and nanopore-blocking; the loose layer is ultra-soft to conformally cover bone surfaces and defect cavity edges, enables ingrowth of osteogenesis-associated cells, and creates a favorable osteogenic microenvironment. As a result, our all-in-one porous membrane possesses full protective abilities in GBR.

Membrane barriers for guided bone regeneration: An overview of available biomaterials

Dental implants revolutionized the treatment options for restoring form, function, and esthetics when one or more teeth are missing. At sites of insufficient bone, guided bone regeneration (GBR) is performed either prior to or in conjunction with implant placement to achieve a three-dimensional prosthetic-driven implant position. To date, GBR is well documented, widely used, and constitutes a predictable and successful approach for lateral and vertical bone augmentation of atrophic ridges. Evidence suggests that the use of barrier membranes maintains the major biological principles of GBR. Since the material used to construct barrier membranes ultimately dictates its characteristics and its ability to maintain the biological principles of GBR, several materials have been used over time. This review, summarizes the evolution of barrier membranes, focusing on the characteristics, advantages, and disadvantages of available occlusive barrier membranes and presents results of updated meta-analyses focusing on the effects of these membranes on the overall outcome.

Guided Tissue and Bone Regeneration Membranes: A Review of Biomaterials and Techniques for Periodontal Treatments

This comprehensive review provides an in-depth analysis of the use of biomaterials in the processes of guided tissue and bone regeneration, and their indispensable role in dental therapeutic interventions. These interventions serve the critical function of restoring both structural integrity and functionality to the dentition that has been lost or damaged. The basis for this review is laid through the exploration of various relevant scientific databases such as Scopus, PubMed, Web of science and MEDLINE. From a meticulous selection, relevant literature was chosen. This review commences by examining the different types of membranes used in guided bone regeneration procedures and the spectrum of biomaterials employed in these operations. It then explores the manufacturing technologies for the scaffold, delving into their significant impact on tissue and bone regenerations. At the core of this review is the method of guided bone regeneration, which is a crucial technique for counteracting bone loss induced by tooth extraction or periodontal disease. The discussion advances by underscoring the latest innovations and strategies in the field of tissue regeneration. One key observation is the critical role that membranes play in guided reconstruction; they serve as a barrier, preventing the entry of non-ossifying cells, thereby promoting the successful growth and regeneration of bone and tissue. By reviewing the existing literature on biomaterials, membranes, and scaffold manufacturing technologies, this paper illustrates the vast potential for innovation and growth within the field of dental therapeutic interventions, particularly in guided tissue and bone regeneration.

A novel computationally engineered collagenase reduces the force required for tooth extraction in an ex-situ porcine jaw model

The currently employed tooth extraction methods in dentistry involve mechanical disruption of the periodontal ligament fibers, leading to inevitable trauma to the bundle bone comprising the socket walls. In our previous work, we have shown that a recombinantly expressed truncated version of clostridial collagenase G (ColG) purified from Escherichia coli efficiently reduced the force needed for tooth extraction in an ex-situ porcine jaw model, when injected into the periodontal ligament. Considering that enhanced thermostability often leads to higher enzymatic activity and to set the basis for additional rounds of optimization, we used a computational protein design approach to generate an enzyme to be more thermostable while conserving the key catalytic residues. This process generated a novel collagenase (ColG-variant) harboring sixteen mutations compared to ColG, with a nearly 4℃ increase in melting temperature. Herein, we explored the potential of ColG-variant to further decrease the physical effort required for tooth delivery using our established ex-situ porcine jaw model. An average reduction of 11% was recorded in the force applied to extract roots of mandibular split first and second premolar teeth treated with ColG-variant, relative to those treated with ColG. Our results show for the first time the potential of engineering enzyme properties for dental medicine and further contribute to minimally invasive tooth extraction.

In vitro evaluation of membranes for regenerative procedures against oral bacteria

The current literature on guided bone regeneration (GBR) and guided tissue regeneration (GTR) membrane contamination reports that the physicochemical characteristics of these biomaterials might influence affinity to bacteria, which appears to be a major drawback for the clinical outcome of the regenerative procedures. Thus, this study aimed to evaluate, in vitro, a multispecies biofilm adherence and passage of bacteria through different types of commercially available membranes for GTR/GBR. Four types of membranes were tested (n=12): LC) Lumina Coat®; JS) Jason®; BG) Biogide®; and LP) Lumina PTFE®. Aluminum foil (AL) simulated an impermeable barrier and was used as the control. The membranes were adapted to specific apparatus and challenged with a mixed bacterial culture composed of A. actinomycetemcomitans b, S. mutans, S. mitis, and A. israelii. After 2 h or 7 days, bacterial adhesion and passage of bacteria were evaluated through CFU counting, which was analyzed by two-way ANOVA e post hoc Tukey, at a 5% significance level. Representative areas of two membranes of each group were analyzed through scanning electron microscopy (SEM) to assess the morphology and organization of the biofilm over the membrane fibers. LC and LP presented similar values of adhered bacterial cells (p > 0.05), significantly inferior when compared to the other groups, in both time points (p < 0.05). All the tested groups were permeable to bacterial cells, with no significant difference between the trial period of 2 h and 7 days (p > 0.05). SEM analyses demonstrated that adhered bacteria number increased throughout the time points (2 h < 7 days). Commercially available biological membranes demonstrated intense bacterial adherence and passage of bacteria, which increased throughout the trial period.

Antimicrobial and Osteogenic Effects of Collagen Membrane Decorated with Chitosan-Nano-Hydroxyapatite

Collagen membranes are routinely used in oral surgery for bone regeneration. Despite their numerous advantages, such as stimulating bone growth, bacterial contamination still remains one of the disadvantages of membrane use. Thus, we assessed the biocompatibility and osteogenic and antibacterial properties of a collagen membrane (OsteoBiol) modified with chitosan (CHI) and hydroxyapatite nanoparticles (HApNPs). Attenuated total reflectance-Fourier transform infrared spectroscopy (ATR FT-IR), X-ray powder diffraction (XRD), and field emission scanning electron microscopy (FE-SEM) were performed for membrane characterization. Biocompatibility was assessed on dental pulp stem cells (DPSCs) by an MTT assay, while the osteogenic effect was assessed by an ALP activity assay and qPCR analysis of osteogenic markers (BMP4, ALP, RUNX2, and OCN). Antimicrobial properties were investigated by counting colony-forming units (CFUs) of Streptococcus mitis, Porphyromonas gingivalis, and Fusobaterium nucleatum on membranes and in the surrounding medium. Membranes showed no cytotoxicity. ALP activity was higher and ALP, BMP4, and OCN genes were up-regulated in DPSCs on modified membranes compared to unmodified membranes. The CFUs were reduced on modified membranes and in the medium. Modified membranes showed great biocompatibility and a high osteoinductive effect. Additionally, they showed antimicrobial and antibiofilm effects against periopathogens. It can be concluded that the incorporation of CHI and hydroxyapatite nanoparticles in collagen membranes may be advantageous to promote osteogenesis and reduce bacterial adhesion.

Effect of argon plasma pre-treatment of healing abutments on peri-implant microbiome and soft tissue integration: a proof-of-concept randomized study

PURPOSE

Biofilm-free implant surface is ultimate prerequisite for successful soft and bone tissue integration. Objective of the study was to estimate the effects of argon plasma healing abutment pre-treatment (PT) on peri-implant soft-tissue phenotype (PiSP), inflammation, plaque accumulation and the microbiome (PiM) between non-treated (NPT) and treated (PT) abutments following 3-months healing period. The hypothesis was that cell-conductive and antimicrobial properties of PT would yield optimal conditions for soft tissue integration.

MATERIAL AND METHODS

Two months following second-phase surgery, microbiological and clinical parameters were assessed around thirty-six healing abutments with two types of microtopography, smooth surface (MACHINED) and ultrathin threaded microsurface (ROUGH). A two level randomization schema was used to achieve equal distribution and abutments were randomly divided into rough and machined groups, and then divided into PT and NPT groups. PiM was assessed using next-generation DNA sequencing.

RESULTS

PiM bacterial composition was highly diverse already two months post-implantation, consisting of key-stone pathogens, early and late colonizers, while the mycobiome was less diverse. PT was associated with lower plaque accumulation and inflammation without significant impact on PiSP, while in NPT clinical parameters were increased and associated with periopathogens. NPT mostly harbored late colonizers, while PT exerted higher abundance of early colonizers suggesting less advanced plaque formation. Interaction analysis in PT demonstrated S. mitis co-occurrence with pro-healthy Rothia dentocariosa and co-exclusion with Parvimonas micra, Porphyromonas endodontalis and Prevotella oris. PiSP parameters were generally similar between the groups, but significant association between PiM and keratinized mucosa width was observed in both groups, with remarkably more expressed diversity in NPT compared to PT. PT resulted in significantly lower BOP and PI around rough and machined abutments, respectively, without specific effect on PiM and PiSP.

CONCLUSIONS

PT contributed to significantly the less advanced biofilm accumulation and inflammation without specific effects on PiSP.

In Vitro Evaluation of the Permeability of Different Resorbable Xenogeneic Membranes after Collagenolytic Degradation

In this in vitro study, we compare the penetration of cells through different resorbable collagen membranes, which were collagenolytically degraded over different time periods. Three different resorbable collagen membranes were evaluated, including two non-cross-linked (NCL) membranes-namely, a porcine (NCL-P) and an equine (NCL-E) membrane-and an enzymatically cross-linked porcine (ECL-B) membrane. A special two-chamber model was fabricated, allowing for the placement of separating membranes, and a non-porous polyester membrane was used as a negative control (C), in order to verify the impermeability of the experimental chamber device. Round membrane samples with a diameter of 16 mm were fabricated. Eighteen membranes of each type were punched and placed on polyethylene nets as carriers. The membranes were then biodegraded-each on its carrier-in 12-well polystyrene plates: three samples of each membrane type were degraded for 1.5, 3, 6, or 12 h in 2 mL of a buffered collagenase solution, at 37 °C. For control purposes, three samples of each membrane type were not degraded, but only immersed in buffer solution for 1.5, 3, 6, or 12 h, at 37 °C. Another three samples of each type of membrane were degraded until complete dissolution, in order to determine the full hydroxyproline content for comparison. Liquid-preserved boar semen (containing at least 120 million sperm cells per milliliter) was used to test the cell occlusivity of the degraded membranes. At baseline and initial degradation, all tested membranes were tight, and no penetration was observed with up to 30 min of incubation time (results not shown). After 1.5 h, cells were partially capable of penetrating the NCL-E membrane only. One sample showed leakage, with a sperm volume of 1.7 million cells/mL over all samples. No penetration occurred in the test, NCL-P, and ECL-B groups. After a degradation time of 3 h, the NCL-P and ECL-B membranes remained occlusive to cells. All the membranes and measurements indicated leakage in the NCL-E group. After 6 h, four NCL-P measurements showed the first signs of cell penetration, as boar spermatozoa were detectable in the lower chamber (64 million cells/mL). The ECL-B membranes remained completely cell occlusive. After 12 h, four NCL-P measurements were cell penetration positive (14.6 million cells/mL), while the ECL-B group remained tight and showed no cell penetration. As the findings of our study are well in accordance with the results of several previous animal studies, it can be concluded that the surrogate model is capable of performing rapid and cheap screening of cell occlusivity for different collagen membranes in a very standardized manner. In particular, claims of long degradation resistance can be easily proven and compared. As the boar spermatozoa used in the present report had a size of 9 × 5 μm, smaller bacteria are probably also able to penetrate the leaking membranes; in this regard, our proposed study set-up may provide valuable information, although it must be acknowledged that sperm cells show active mobility and do not only translocate by growth.

Fabrication of Guided Tissue Regeneration Membrane Using Lignin-Mediated ZnO Nanoparticles in Biopolymer Matrix for Antimicrobial Activity

Periodontal disease is a common complication, and conventional periodontal surgery can lead to severe bleeding. Different membranes have been used for periodontal treatment with limitations, such as improper biodegradation, poor mechanical property, and no effective hemostatic property. Guided tissue regeneration (GTR) membranes favoring periodontal regeneration were prepared to overcome these shortcomings. The mucilage of the chia seed was extracted and utilized to prepare the guided tissue regeneration (GTR) membrane. Lignin having antibacterial properties was used to synthesize lignin-mediated ZnO nanoparticles (∼Lignin@ZnO) followed by characterization with analytical techniques like Fourier-transform infrared spectroscopy (FTIR), UV–visible spectroscopy, and scanning electron microscope (SEM). To fabricate the GTR membrane, extracted mucilage, Lignin@ZnO, and polyvinyl alcohol (PVA) were mixed in different ratios to obtain a thin film. The fabricated GTR membrane was evaluated using a dynamic fatigue analyzer for mechanical properties. Appropriate degradation rates were approved by degradability analysis in water for different intervals of time. The fabricated GTR membrane showed excellent antibacterial properties against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) bacterial species.

Permeability of P. gingivalis or its metabolic products through collagen and dPTFE membranes and their effects on the viability of osteoblast-like cells: an in vitro study

Membrane exposure is a widely reported and relatively common complication in Guided Bone Regeneration (GBR) procedures. The introduction of micro-porous dPTFE barriers, which are impervious to bacterial cells, could reduce the technique sensitivity to membrane exposure, even if there are no studies investigating the potential passage of bacterial metabolites through the barrier. Aim of this study was the in vitro evaluation of the permeability of three different GBR membranes (dPTFE, native and cross-linked collagen membranes) to Porphyromonas gingivalis; in those cases, where bacterial penetration could not be observed, another purpose was the analysis of the viability and differentiation capability of an osteosarcoma (U2OS) cell line in presence of bacteria eluate obtained through membrane percolation. A system leading to the percolation of P. gingivalis broth culture through the experimental membranes was arranged to assess the permeability to bacteria after 24 and 72 h of incubation. The obtained solution was then added to U2OS cell cultures which underwent, after 10 days of incubation, MTT and red alizarin essays. The dPTFE membrane showed resistance to bacterial penetration, while both types of collagen membranes were crossed by P. gingivalis after 24 h. The bacteria eluate filtered through dPTFE membrane didn't show any toxicity on U2OS cells. Results of this study demonstrate that dPTFE membranes can contrast the penetration of both P. gingivalis and its metabolites toxic for osteoblast-like cells. The toxicity analysis was not possible for the collagen membranes, since permeability to bacterial cells was observed within the first period of incubation.

Complications in bone-grafting procedures: Classification and management

Bone-regenerative interventions aiming to restore deficient alveolar ridges, such as the use of block grafts or through the application of guided bone-regeneration principles, have reported positive outcomes in the published scientific literature. These interventions, however, are invasive, and hence, intraoperative and/or postoperative complications may occur. The types of complications and their severity may vary from the exposure of the biomaterial (membrane or graft) to postsurgical infections, neurosensorial disturbances, occurrence of hemorrhage, and pain, etc. The aim of the present narrative review was to search the available scientific evidence concerning the incidence of these complications, their effect on treatment outcomes, their clinical management and, finally, strategies aimed at prevention. Exposure of the barrier membrane or the block graft is the most common complication associated with oral regenerative interventions. To manage these complications, depending on the extent of the exposure and the presence or absence of concomitant infections, therapeutic measures may vary, from the topical application of antiseptics to the removal of the barrier membrane or the block graft. Regardless of their treatment, the occurrence of these complications has been associated with patient selection, with compliant patients (eg, nonsmokers) having a lower reported incidence of complications. Similarly, surgical factors such as correct flap elevation and a tensionless closure are of obvious importance. Finally, to prevent the incidence of complications, it appears prudent to utilize whenever possible less invasive surgical interventions.

Periodontitis and diabetes mellitus co-morbidity: A molecular dialogue

BACKGROUND

Type 2 diabetes mellitus (T2DM) and periodontitis are two biologically linked diseases that often coexist in complex interaction. While periodontitis may lead to insulin receptor desensitization, diabetes may increase the expression of inflammatory cytokines, such as Tumor Necrosis Factor-α (TNF-α) and Interleukin 6 (IL-6), in the gingival crevicular fluid and activate osteoclasts via Receptor activator of nuclear factor kappa-Β ligand (RANK-L) production, leading to bone resorption. However, the association between the two diseases processes, where one may exacerbate the progression of the other, is unclear. In addition, both diseases have similar mechanistic themes, such as chronic inflammation and oxidative stress. This review aimed to investigate the pathophysiological and molecular mechanisms underlying T2DM and periodontitis.

HIGHLIGHT

Uncontrolled diabetes is often associated with severe periodontitis, measured by clinical attachment loss. Alteration in the oral microbiome composition, which may activate the host inflammatory response and lead to irreversible oxidative stress, is a common finding in both diseases. An understanding of the molecular crosstalk between the two disease processes is crucial for developing therapeutic targets that inhibit bone resorption and halt the progression of periodontitis in patients with diabetes.

CONCLUSION

The Oral microbiome composition in T2DM and periodontitis shifts toward dysbiosis, favoring bacterial pathogens, such as Fusobacteria and Porphyromonas species. Both conditions are marked by pro-inflammatory immune activity via the activation of Interleukin 17 (IL-17), Interleukin 1 (IL-1), TNF-α, and Nuclear Factor Kappa Beta (NF-κB). Common molecular crosstalk signaling appears to involve advanced glycation end products (AGEs) and oxidative stress. Thus, future drug targets are multifactorial, ranging from modulatory of host inflammatory response to preventing the accumulation of AGEs and oxidative free radicals.

The Collagen Origin Influences the Degradation Kinetics of Guided Bone Regeneration Membranes

Collagen membranes are currently the most widely used membranes for guided bone regeneration; however, their rapid degradation kinetics means that the barrier function may not remain for enough time to permit tissue regeneration to happen. The origin of collagen may have an important effect on the resistance to degradation. The aim of this study was to investigate the biodegradation pattern of five collagen membranes from different origins: Biocollagen, Heart, Evolution X-fine, CopiOs and Parasorb Resodont. Membranes samples were submitted to different degradation tests: (1) hydrolytic degradation in phosphate buffer saline solution, (2) bacterial collagenase from Clostridium histolyticum solution, and (3) enzyme resistance using a 0.25% porcine trypsin solution. Immersion periods from 1 up to 50 days were performed. At each time point, thickness and weight measurements were performed with a digital caliper and an analytic microbalance, respectively. ANOVA and Student–Newman–Keuls tests were used for comparisons (p < 0.05). Differences between time-points within the same membranes and solutions were assessed by pair-wise comparisons (p < 0.001). The Evolution X-fine collagen membrane from porcine pericardium attained the highest resistance to all of the degradation tests. Biocollagen and Parasorb Resodont, both from equine origin, experienced the greatest degradation when immersed in PBS, trypsin and C. histolyticum during challenge tests. The bacterial collagenase solution was shown to be the most aggressive testing method.

In Vitro Biodegradation Pattern of Collagen Matrices for Soft Tissue Augmentation

Collagen matrices have become a great alternative to the use of connective tissue grafts for soft tissue augmentation procedures. One of the main problems with these matrices is their volume instability and rapid degradation. This study has been designed with the objective of examining the degradation of three matrices over time. For this purpose, pieces of 10 × 10 mm² of Fibro-Gide, Mucograft and Mucoderm were submitted to three different degradation tests-(1) hydrolytic degradation in phosphate buffer solution (PBS); (2) enzyme resistance, using a 0.25% porcine trypsin solution; and (3) bacterial collagenase resistance (Clostridium histolyticum)-over different immersion periods of up to 50 days. Weight measurements were performed with an analytic microbalance. Thickness was measured with a digital caliper. A stereomicroscope was used to obtain the matrices' images. ANOVA and Student-Newman-Keuls tests were used for mean comparisons (p < 0.05), except when analyzing differences between time-points within the same matrix and solution, where pair-wise comparisons were applied (p < 0.001). Fibro-Gide attained the highest resistance to all degradation challenges. The bacterial collagenase solution was shown to constitute the most aggressive test as all matrices presented 100% degradation before 14 days of storage.

Porous polymeric membranes: fabrication techniques and biomedical applications

Porous polymeric membranes have shown great potential in biological and biomedical applications such as tissue engineering, bioseparation, and biosensing, due to their structural flexibility, versatile surface chemistry, and biocompatibility. This review outlines the advantages and limitations of the fabrication techniques commonly used to produce porous polymeric membranes, with especial focus on those featuring nano/submicron scale pores, which include track etching, nanoimprinting, block-copolymer self-assembly, and electrospinning. Recent advances in membrane technology have been key to facilitate precise control of pore size, shape, density and surface properties. The review provides a critical overview of the main biological and biomedical applications of these porous polymeric membranes, especially focusing on drug delivery, tissue engineering, biosensing, and bioseparation. The effect of the membrane material and pore morphology on the role of the membranes for each specific application as well as the specific fabrication challenges, and future prospects of these membranes are thoroughly discussed.

The Role of Epigenetic Functionalization of Implants and Biomaterials in Osseointegration and Bone Regeneration-A Review

The contribution of epigenetic mechanisms as a potential treatment model has been observed in cancer and autoimmune/inflammatory diseases. This review aims to put forward the epigenetic mechanisms as a promising strategy in implant surface functionalization and modification of biomaterials, to promote better osseointegration and bone regeneration, and could be applicable for alveolar bone regeneration and osseointegration in the future. Materials and Methods: Electronic and manual searches of the literature in PubMed, MEDLINE, and EMBASE were conducted, using a specific search strategy limited to publications in the last 5 years to identify preclinical studies in order to address the following focused questions: (i) Which, if any, are the epigenetic mechanisms used to functionalize implant surfaces to achieve better osseointegration? (ii) Which, if any, are the epigenetic mechanisms used to functionalize biomaterials to achieve better tissue regeneration? Findings from several studies have emphasized the role of miRNAs in functionalizing implants surfaces and biomaterials to promote osseointegration and bone regeneration, respectively. However, there are scarce data on the role of DNA methylation and histone modifications for these specific applications, despite being commonly applied in cancer research. Studies over the past few years have demonstrated that biomaterials are immunomodulatory rather than inert materials. In this context, epigenetics can act as next generation of advanced treatment tools for future regenerative techniques. Yet, there is a need to evaluate the efficacy/cost effectiveness of these techniques in comparison to current standards of care.

Local tissue effects of various barrier membranes in a rat subcutaneous model

Purpose

The purpose of this study was to examine the local tissue reactions associated with 3 different poly(lactic-co-glycolic acid) (PLGA) prototype membranes and to compare them to the reactions associated with commercially available resorbable membranes in rats.

Methods

Seven different membranes—3 synthetic PLGA prototypes (T1, T2, and T3) and 4 commercially available membranes (a PLGA membrane, a poly[lactic acid] membrane, a native collagen membrane, and a cross-linked collagen membrane)—were randomly inserted into 6 unconnected subcutaneous pouches in the backs of 42 rats. The animals were sacrificed at 4, 13, and 26 weeks. Descriptive histologic and histomorphometric assessments were performed to evaluate membrane degradation, visibility, tissue integration, tissue ingrowth, neovascularization, encapsulation, and inflammation. Means and standard deviations were calculated.

Results

The histological analysis revealed complete integration and tissue ingrowth of PLGA prototype T1 at 26 weeks. In contrast, the T2 and T3 prototypes displayed slight to moderate integration and tissue ingrowth regardless of time point. The degradation patterns of the 3 synthetic prototypes were similar at 4 and 13 weeks, but differed at 26 weeks. T1 showed marked degradation at 26 weeks, whereas T2 and T3 displayed moderate degradation. Inflammatory cells were present in all 3 prototype membranes at all time points, and these membranes did not meaningfully differ from commercially available membranes with regard to the extent of inflammatory cell infiltration.

Conclusions

The 3 PLGA prototypes, particularly T1, induced favorable tissue integration, exhibited a similar degradation rate to native collagen membranes, and elicited a similar inflammatory response to commercially available non–cross-linked resorbable membranes. The intensity of inflammation associated with degradable dental membranes appears to relate to their degradation kinetics, irrespective of their material composition.

Differential Biodegradation Kinetics of Collagen Membranes for Bone Regeneration

Native collagen-based membranes are used to guide bone regeneration; but due to their rapid biodegradation, this treatment is often unpredictable. The purpose of this study was to investigate the biodegradability of natural collagen membranes. Three non-cross-linked resorbable collagen barrier membranes were tested: Derma Fina (porcine dermis), Evolution Standard (equine pericardium) and Duo-Teck (equine lyophilized collagen felt). 10 × 10 mm² pieces of membranes were submitted to three different degradation procedures: (1) hydrolytic degradation in phosphate buffer solution, (2) enzyme resistance, using a 0.25% porcine trypsin solution, and (3) bacterial (Clostridium histolyticum) collagenase resistance test. Weight measurements were performed with an analytic microbalance. Thickness was measured with a digital caliper. Membranes were analyzed at different time-points, up to 21 d of immersion. A stereomicroscope was used to obtain membranes’ images. ANOVA and Student Newman Keuls were used for mean comparisons (p < 0.05), except when analyzing differences between time-points within the same membrane and solution where pair-wise comparisons were applied (p < 0.001). Derma Fina attained the highest resistance to all degradation challenges. Duo-Teck was the most susceptible membrane to degradation, complete degradation occurred as soon as 8 h. The bacterial collagenase solution performed as the most aggressive test as all membranes presented 100% degradation before 21 d.

Antimicrobial Efficacy Assessment of Human Derived Composite Amnion-Chorion Membrane

Human derived composite amnion-chorion membrane (ACM) has been used to facilitate wound healing due to reported anti-inflammatory properties and promotion of cell proliferation. This study aimed to assess the antimicrobial properties of the ACM using novel methods to visualize the antimicrobial efficacy of membranes in situ at different time points. Porcine Pericardium Collagen Membranes (PPCM) served as membrane controls. Circular pieces of the membranes were used in three different assays: insert, agar contact and glass-bottom well assays. Streptococcus gordonii were spotted onto the membranes and the plates were subsequently centrifuged to ensure direct bacterial contact with the membranes in the insert and agar contact assays, thus better mimicking bacterial adherence in the oral cavity. After incubation at 37 °C for 8, 24, and 48 hours, the membranes were dyed with the Live/Dead BacLight Bacterial Viability fluorescence stain and analyzed via confocal microscopy. The results demonstrated that the ACM completely inhibited bacterial growth at all time points, whereas the PPCM did not demonstrate any antimicrobial properties. Within the limits of this study, the ACM showed extremely high antimicrobial efficacy against oral streptococci. In addition, our methods may be useful in assessing antimicrobial properties for biomaterials with minimum diffusion ability, when traditional assessment methods are not applicable.

Enamel matrix derivative in liquid form as adjunct to natural bovine bone grafting at buccal bone dehiscence defects at implant sites: An experimental study in beagle dogs

OBJECTIVES

To evaluate the effect of enamel matrix derivative in liquid form (EMD-liquid) as adjunct to grafting with natural bovine bone (NBB), on new bone formation and osseointegration in buccal dehiscence defects at dental implants.

MATERIAL AND METHODS

In six beagles, 3 months after extraction of the mandibular premolars and first molars. Three titanium implants (3.3 Ø × 8.0 mm) were inserted, and dehiscence-type defects (mesiodistal width 3 mm × 5 mm depth) were created on their buccal aspect. The defects were randomly assigned to one of the following three treatment groups: Group 1: NBB, Group 2: NBB/EMD-L, Group 3: Control. All sites were covered with a collagen membrane. Histomorphometric measurements were performed after 3 months of healing.

RESULTS

New bone area, bone-to-implant contact (BIC), and first BIC (fBIC) in the NBB and NBB/EMD-L groups were significantly greater than in the control group (p < .05). Further, f-BIC was at a significantly more coronal position in the NBB + EMD-liquid group (0.4 ± 0.1 mm) compared with the NBB group (1.2 ± 0.2 mm).

CONCLUSIONS

Natural bovine bone grafting enhances bone regeneration and osseointegration at implants with buccal bone dehiscences compared with no grafting, and adjunct use of EMD-liquid appears to further enhance bone formation and osseointegration.

Efficacy of Collagen-Based Membranes in Alveolar Bone Augmentation

Collagen-based membranes (CBMs) have similar permissive bone formation capabilities when compared to non-absorbable membranes. CBMs have been classified as non-cross-linked membranes (NCLMs) and cross-linked membranes (CLMs) depending on whether the cross-linking between the collagen fibers was artificially increased. The purpose of this study is to evaluate the bone maintenance capacity between NCLMs and CLMs by comparing resorption of regenerated bone. The inclusion criteria consisted of: (1) The use of a CBM, either being an NCLM or CLM for coverage of grafted bone; (2) follow-up for more than one year; (3) the presence of the patient's orthopantomographic X-ray (OPTG) immediately following the installation of implants and one year after. The bone resorption observed in the OPTG was determined by measuring the number of exposed threads of the implant. The number of thread exposures in the implant was compared according to CBM types. OPTGs taken immediately following the installation of implants and at one year after installation were compared. The subject of the measurement was always the implant in which the greatest number of exposed threads were present in each patient. A total of 56 subjects and 97 implants were used in this study. There was no significant difference between NCLM and CLM groups (p > 0.05). However, there was a statistically significant difference (p = 0.02) between the groups when a bone graft was applied to both the maxilla and the mandible. The average number of thread exposures was less than 1.5. In this study, no comparison was made between commonly known causes of bone loss and membrane types.

Hyaluronic acid on collagen membranes: An experimental study in rats

OBJECTIVE

The aim of this study was to evaluate the effect of hyaluronic acid (HA) in the structure and degradation patterns of BioGide^® and OsseoGuard™ collagen membranes. HA mediates inflammation and acts in cell migration, adhesion, and differentiation, benefitting tissue remodeling and vascularization. These are desirable effects in guided regeneration procedures, but it is still unknown whether HA alters the barrier properties of absorbable membranes.

DESIGN

Bone defects were created in the calvaria of rats, which were treated with HA gel 1% (HA group) or simply filled with blood clot (control group), and covered with BioGide^® or OsseoGuard™. The animals were euthanized after 1, 30, and 60days, and their calvarias were processed for histological analysis.

RESULTS

BioGide^®, in both HA and control groups, showed vascularization, intense cell colonization, bone formation, and tissue integration at 30 and 60days. In contrast, Osseoguard™ presented minimal cellular colonization, and inflammatory reaction associated to foreign body reaction in both time points and groups. The HA group of BioGide^® showed higher cell colonization (574.9±137.6) than the control group (269.1±70.83) at 60days (p<0.05). Despite this finding, the structure and degradation pattern were similar for BioGide^® and Osseoguard™ in the HA and control groups.

CONCLUSION

The results suggest that HA did not interfere with tissue integration and structural degradation of BioGide^® and Osseoguard™ membranes.

Biodegradable Polymer Membranes Applied in Guided Bone/Tissue Regeneration: A Review

Polymer membranes have been widely used in guided tissue regeneration (GTR) and guided bone regeneration (GBR). In this review, various commercially available membranes are described. Much attention is paid to the recent development of biodegradable polymers applied in GTR and GBR, and the important issues of biodegradable polymeric membranes, including their classification, latest experimental research and clinical applications, as well as their main challenges are addressed. Herein, natural polymers, synthetic polymers and their blends are all introduced. Pure polymer membranes are biodegradable and biocompatible, but they lack special properties such as antibacterial properties, osteoconductivity, and thus polymer membranes loaded with functional materials such as antibacterial agents and growth factors show many more advantages and have also been introduced in this review. Despite there still being complaints about polymer membranes, such as their low mechanical properties, uncontrollable degradation speed and some other drawbacks, these problems will undoubtedly be conquered and biodegradable polymers will have more applications in GTR and GBR.

Assessment of dehydrothermally cross-linked collagen membrane for guided bone regeneration around peri-implant dehiscence defects: a randomized single-blinded clinical trial

Purpose

The aim of this study was to determine the clinical feasibility of using dehydrothermally cross‐linked collagen membrane (DCM) for bone regeneration around peri-implant dehiscence defects, and compare it with non-cross-linked native collagen membrane (NCM).

Methods

Dehiscence defects were investigated in twenty-eight patients. Defect width and height were measured by periodontal probe immediately following implant placement (baseline) and 16 weeks afterward. Membrane manipulation and maintenance were clinically assessed by means of the visual analogue scale score at baseline. Changes in horizontal thickness at 1 mm, 2 mm, and 3 mm below the top of the implant platform and the average bone density were assessed by cone-beam computed tomography at 16 weeks. Degradation of membrane was histologically observed in the soft tissue around the implant prior to re-entry surgery.

Results

Five defect sites (two sites in the NCM group and three sites in the DCM group) showed soft-tissue dehiscence defects and membrane exposure during the early healing period, but there were no symptoms or signs of severe complications during the experimental postoperative period. Significant clinical and radiological improvements were found in all parameters with both types of collagen membrane. Partially resorbed membrane leaflets were only observed histologically in the DCM group.

Conclusions

These findings suggest that, compared with NCM, DCM has a similar clinical expediency and possesses more stable maintenance properties. Therefore, it could be used effectively in guided bone regeneration around dehiscence-type defects.

Comparative evaluation of biphasic calcium phosphate and biphasic calcium phosphate collagen composite on osteoconductive potency in rabbit calvarial defect

BACKGROUND

The aim of this study was to determine the osteoconductivity of biphasic calcium phosphate collagen composite (BCPC) in rabbit calvarial defect model by comparing with biphasic calcium phosphate (BCP). Four 8 mm diameter bicortical calvarial defects were made in ten rabbits. Each of the defects was randomly assigned and filled with 1) collagen sponge, 2) BCP, 3) BCPC, and 4) nothing as control. The animals were sacrificed at either 2 weeks (n = 5) or 8 weeks (n = 5) healing period.

RESULTS

All groups showed wedge shaped new bone formation limited to the area of the defect margin at both healing periods. The amounts of new bone and defect closure were similar among all groups. In the control and collagen sponge group, the center of the defect was depressed by surrounding tissues. In contrast, in BCP and BCPC group, the center of the defect did not depressed and the grafted materials maintained the space. And the augmented area was significantly higher in BCP and BCPC group compared to the control and collagen sponge group at both healing periods (p < 0.05).

CONCLUSIONS

The BCPC and BCP demonstrated proper space maintaining capacity and osteoconductive property, suggesting BCPC can be efficiently utilized in various clinical situations.

Biocompatibility and resorption pattern of newly developed hyaluronic acid hydrogel reinforced three-layer poly (lactide-co-glycolide) membrane: histologic observation in rabbit calvarial defect model

Background

The aim of this study was to evaluate the biocompatibility and resorption pattern in three-layer poly (lactide-co-glycolide) (PLGA) membrane according to the concentrations of hyaluronic acid (HA) hydrogel in rabbit calvarial defect model. Four standardized circular defects with 8 mm diameter were created on the four rabbit calvarium. Three-layer PLGA membranes (5% and 10% HA gel) were used as the test groups, both collagen membrane and monolayer PLGA membrane as the control groups.

Results

After sacrificing the animals after 4 and 8 weeks, block sections were harvested and histological observation was performed. Pus formation was observed in a site on the three-layer PLGA membranes (with 10% HA gel) of 4 weeks group and initial inflammatory responses were observed on the three-layer PLGA membrane group. However, when compared to both the monolayer PLGA membrane group and collagen membrane group, the HA gel-reinforced three-layer PLGA membrane showed improved cell occlusion and retention period, showing the formation of the capsule-like structure. There was no definite difference between the results of the membranes fabricated with either 5% or 10% HA hydrogel.

Conclusion

The HA reinforced three-layer PGLA membrane was retained longer than control group and showed good property in cell occlusion. Future study is under process to improve the inflammatory response of the three layer PLGA membranes, which were observed in this study.

Biodegradation pattern and tissue integration of native and cross-linked porcine collagen soft tissue augmentation matrices - an experimental study in the rat

INTRODUCTION

Within the last decades, collagen types I and III have been established as a sufficient biomaterial for GBR and GTR procedures. They might also be an adequate matrix for soft tissue augmentations. However, collagen materials differ significantly regarding resorption time, biodegradation pattern and the invasion of inflammatory cells.The aim of the present study was to compare the biodegradation and tissue integration of native, differently processed and cross-linked collagen scaffolds in rats.

METHODS

Four experimental porcine collagen matrices of 1.0 mm thickness, developed for soft tissue augmentation procedures, were tested. Based on the same native dermal Type I and III collagen, native (ND, Mucoderm prototype), specifically defatted (DD), ethylene dioxide cross-linked (ECL) and dehydrothermally cross-linked (DCL) dermis collagen (AAP/Botiss Biomaterials, Berlin, Germany) were evaluated. Two specimens of 1 × 1 cm were fixed around a non-absorbable spacer using non-absorbable sutures. After rehydration, specimens (N = 8) were randomly allocated in unconnected subcutaneous pouches on the back of 40 Wistar rats. Rats were divided into five groups (1, 2, 4, 8 and 12 weeks), including eight animals each. After each period, eight rats were sacrificed and explanted specimens were prepared for histological analysis. The following parameters were evaluated: membrane thickness as a sign of biodegradation and volume stability, cell ingrowth, vascularization, tissue integration and foreign body reaction.

RESULTS

Biodegradation pattern of the non cross-linked collagen scaffolds differed only slightly in terms of presence of inflammatory cells and cell invasion into the matrix. In terms of biodegradation, ECL displayed a considerable slower resorption than ND, DCL and DD. Chemical cross-linking using ethylene dioxide showed a significant higher invasion of inflammatory cells.

CONCLUSION

Within the limits of the present study it was concluded that the processing techniques influenced the collagen properties in a different intensity. Dehydrothermal cross-linking and special defatting did not notably change the biodegradation pattern, whereas cross-linking using ethylene dioxide led to significant higher volume stability of the matrix. However, ECL showed an increased inflammatory response and compromised tissue integration. Therefore, ethylene dioxide seems to be not suitable for stabilization of collagen matrices for soft tissue augmentation procedures.

Collagen--emerging collagen based therapies hit the patient

The choice of biomaterials available for regenerative medicine continues to grow rapidly, with new materials often claiming advantages over the short-comings of those already in existence. Going back to nature, collagen is one of the most abundant proteins in mammals and its role is essential to our way of life. It can therefore be obtained from many sources including porcine, bovine, equine or human and offer a great promise as a biomimetic scaffold for regenerative medicine. Using naturally derived collagen, extracellular matrices (ECMs), as surgical materials have become established practice for a number of years. For clinical use the goal has been to preserve as much of the composition and structure of the ECM as possible without adverse effects to the recipient. This review will therefore cover in-depth both naturally and synthetically produced collagen matrices. Furthermore the production of more sophisticated three dimensional collagen scaffolds that provide cues at nano-, micro- and meso-scale for molecules, cells, proteins and bulk fluids by inducing fibrils alignments, embossing and layered configuration through the application of plastic compression technology will be discussed in details. This review will also shed light on both naturally and synthetically derived collagen products that have been available in the market for several purposes including neural repair, as cosmetic for the treatment of dermatologic defects, haemostatic agents, mucosal wound dressing and guided bone regeneration membrane. There are other several potential applications of collagen still under investigations and they are also covered in this review.

Nano-crystalline hydroxyapatite bone graft combined with bioresorbable collagen membrane in the treatment of periodontal intrabony defects: A randomized controlled clinical trial

Aim:

To evaluate the clinical outcome of nanocrystalline hydroxyapatite (NcHA) bonegraft (Sybograf^®) in combination with collagen membrane (PerioCol^®) compared with open flap debridement (OFD) only in the treatment of intrabony periodontal defects.

Materials and Methods:

Eighteen intrabony defects in 16 systemically healthy patients aged between 25-65 years, were randomly assigned to test and control groups. The Plaque index, gingival index, probing pocket depth (PPD), clinical attachment level (CAL), and gingival recession were recorded at baseline, and were reevaluated at 6 months. In addition to this, radiographic bone fill was assessed using digital software. At the test site NcHA bone graft and collagen membrane was placed, whereas at the control site only, OFD was done. Recall appointments were made at 7^th day, 1^st month, 3^rd month, and 6^th month.

Results:

The data were subjected to statistical analysis using the Mann-Whitney ‘U’ Test and Wilcoxon signed rank sum test. In the control group, the mean reduction of PPD was 3.22±1.09 mm and CAL gain was 2.78±1.09 mm. In the test group, the mean PPD reduction of 4.33±0.5 mm and mean gain in CAL was 3.78±0.66 mm at 6 months. The mean increase in gingival recession was 0.55±0.72 mm in test and 0.44±0.52 mm in control group.

Conclusion:

The NcHA bone graft in combination with collagen membrane demonstrated better clinical outcomes compared with OFD alone.

Clinical and radiographic evaluation of Nano-crystalline hydroxyapatite bone graft (Sybograf) in combination with bioresorbable collagen membrane (Periocol) in periodontal intrabony defects

Background:

Nanosized ceramics may represent a promising class of bone graft substitutes due to their improved osseointegrative properties. Nanocrystalline Hydroxyapatite (NcHA) bind to bone and stimulate bone healing by stimulation of osteoblast activity. The present study aims to explore the clinical and radiographical outcome of NcHA bonegraft (Sybograf^®) with collagen membrane (Periocol^®), in comparison with open flap debridement (OFD), in the treatment of intrabony periodontal defects.

Materials and Methods:

A parallel-group, randomized, controlled clinical trial was designed to conduct the study. Eighteen intrabony defects in 14 systemically healthy patients aged between 25 to 65 years were randomly assigned to test and control group. The plaque index, gingival index, probing pocket depth (PPD), clinical attachment level (CAL), and gingival recession (REC) were recorded at baseline, and were reevaluated at 6 months. In addition to this, radiographic bone fill was assessed using digital software. At the test site, NcHA bone graft and collagen membrane was placed, whereas at the control site, only OFD was done. Recall appointments were made at 7 days, 30 days, and then at 3 months and 6 months.

Results:

The data were subjected to statistical analysis using the Mann-Whitney ‘U’ Test and Wilcoxon signed rank sum test. In the control group, the mean reduction of PPD was 3.22±1.09 mm (P=0.007) and CAL gain was 2.77±1.09 mm (P=0.007). In the test group, the mean PPD reduction of 4.33±0.5 mm (P=0.006) and mean gain in CAL was 3.77±0.66 mm (P=0.006) at 6 months. The mean increase in REC was 0.55±0.72 mm (P=0.025) in test, and 0.44±0.52 mm (P=0.046) in control group. The mean gain in radiographic defect fill was 2.07±0.67 mm (P=0.008) in test and 0.91±0.21 mm (P=0.007) in control group.

Conclusion:

The nanocrystalline hydroxyapatite bone graft in combination with collagen membrane demonstrated clinical advantages beyond that achieved by OFD alone.

Influence of a collagen membrane and recombinant platelet-derived growth factor on vertical bone augmentation in implant-fixed deproteinized bovine bone--animal pilot study

OBJECTIVES

Combinations of bone substitute block materials with membrane techniques as well as with growth factors are possible options to enhance the prognosis of vertical bone augmentation. Therefore, the aim of the pilot study was to compare the influence of a collagen membrane and a signal protein (rhPDGF-BB) on vertical bone augmentation with a stable fixed block material (deproteinized bovine bone [DBB]).

MATERIALS AND METHODS

In 12 rabbits, a DBB-block was implant-fixed on the tibia in a split-leg-design. Included were: DBB only (control), DBB + collagen membrane (test), DBB + rhPDGF-BB (test) and DBB + rhPDGF-BB + collagen membrane (test). 24 samples were examined after 3 (n = 12) and 6 weeks (n = 12). Calculated parameters were new bone area (NBA;%), new vertical bone height (VBH; mm). Due to the pilot character of this study, single values are shown descriptively only.

RESULTS

After 3 weeks, there were constant higher NBA values in the rhPDGF-BB-group without membrane (NBA (%) DBB: 30/16/4; DBB + membrane: 25/17/7, DBB + rhPDGF-BB: 40/33/34, DBB + rhPDGF-BB + membrane: 0/30/16; VBH (mm) DBB: 1.2/1.2/1, DBB + membrane: 0.7/0.9/1, DBB + rhPDGF-BB: 0.7/0.9/1, DBB + rhPDGF-BB + membrane: 0/1.1/1). After 6 weeks, both membrane groups showed a constant higher NBA and VBH independent to the use of rhPDGF-BB (NBA DBB: 3/0/5, DBB + membrane: 20/35/31, DBB + rhPDGF-BB: 5/8/4, DBB + rhPDGF-BB + membrane: 31/35/40; VBH DBB: 0.3/0.3/0.6, DBB + membrane: 1.6/2.4/2.1, DBB + rhPDGF-BB: 0.4/0.7/0.8, DBB + rhPDGF-BB + membrane: 1.8/2/1.8).

CONCLUSIONS

For vertical augmentation, the addition of rhPDGF-BB to DBB-blocks may increase early bone growth. In the later phase, the use of a collagen membrane enhances new bone volume and height to a significant greater extend. Even if the results are higher than those in the non-membrane groups, the low gain of bone after the short time periods still needs improvement.

Randomized controlled trial on lateral augmentation using two collagen membranes: morphometric results on mineralized tissue compound

BACKGROUND

Guided bone regeneration is considered an effective tool for gaining mineralized tissue either at exposed implant surface or in deficient alveolar ridge areas before implant placement.

MATERIAL AND METHODS

Customized casts obtained following impression taking at surgery and re-entry allowed for morphometric assessment of alveolar ridge alterations 6 months after one-stage augmentation of bone dehiscences. In a randomized pilot study using biphasic calcium phosphate tests (n=17) received treatment with ribose cross-linked collagen membranes (RCLM), whereas controls (n=20) received non-cross-linked membranes. The primary endpoint was to quantify the effect of membrane type on dimensional changes in bone margins at crestal level of endosseous implants.

RESULTS

Soft tissue dehiscencies occurred at 70.5% and 55% frequency for tests and controls, respectively. Gain in clinically hard newly mineralized tissue at the crestal level was significantly higher in test group in lateral (1.8 versus 0.7 mm; p=.046) and in vertical dimensions (1.1 versus 0.2 mm; p=.035) compared with controls. Second measurement obtained at the border of reflected flap revealed no significant difference between groups (3.0 versus 2.1 mm; p=0.57) for lateral dimension.

CONCLUSIONS

Both collagen devices were effective in bone augmentation. RCLMs supported mineralization process and remodelling even in sites showing compromised healing as indicated by morphometric outcome.

Use of a new cross-linked collagen membrane for the treatment of dehiscence-type defects at titanium implants: a prospective, randomized-controlled double-blinded clinical multicenter study

OBJECTIVES

The aim of the present randomized-controlled double-blinded clinical multicenter study was to assess the use of either a new cross-linked (VN) or a native collagen membrane (BG) for the treatment of dehiscence-type defects at titanium implants.

MATERIAL AND METHODS

A total of n=54 patients were recruited in four German university clinics. According to a parallel-groups design, dehiscence-type defects at titanium implants were filled with a natural bone mineral and randomly assigned to either VN or BG. Submerged sites were allowed to heal for 4 months. Primary (e.g., changes in defect length - DeltaDL, quality of newly formed tissue [0-4] - TQ) and secondary parameters (e.g., membrane exposure, tissue conditions at dehisced sites) were consecutively recorded.

RESULTS

Four patients were excluded due to an early wound infection (VN:3; BG:1), and one patient was lost during follow-up (VN). The mean DeltaDL was 3.0 +/- 2.5 mm in the VN, and 1.94 +/- 2.13 mm in the BG group. The assessment of TQ revealed comparable mean values in both groups (VN: 3.05 +/- 1.66, BG: 3.46 +/- 1.48). A significant correlation between membrane exposure and inflammation of the adjacent soft tissue was observed in the VN group. In both groups, the mean DL and TQ values were not significantly different at either non-exposed or exposed implant sites.

CONCLUSION

The results of the present study have indicated that VN supported bone regeneration on a level non-inferior to BG. However, in case of a premature membrane exposure, cross-linking might impair soft-tissue healing or may even cause wound infections.

Degradation of collagen-guided tissue regeneration membranes by proteolytic enzymes of Porphyromonas gingivalis and its inhibition by antibacterial agents

Previous studies have shown that whole cells of several periodontal pathogenic bacteria including Porphyromonas gingivalis may degrade the clinically used regeneration membranes Biomend Extend and Bio-Gide. Fractionation of P. gingivalis cells revealed that cell membrane-associated proteases are responsible for the in vitro degradation of the collagen membranes. In the present study, the specific role of extracellular vesicles and the purified Arg-gingipain enzyme of P. gingivalis in the degradation of three differently cross-linked collagen membranes (Ossix; Bio-Gide and Biomend Extend) was examined. In addition, the inhibitory effect of antibacterial agents and antibiotics used in local periodontal therapy on the enzymatic degradation was evaluated. The data presented show that while all tested collagen membranes, are prone to lysis by oral bacterial proteases, cross-linked membranes are more resistant to proteolysis. Furthermore, therapeutical concentrations of the antibacterial and antibiotic agents chlorhexidine, cetylpyridiniumchloride, minocycline and doxycycline were found to partially inhibit the enzymatic breakdown of the membranes, while metronidazole had no such effect. These results suggest that the presence of P. gingivalis cells, extracellular vesicles and enzymes in the vicinity of regeneration membranes in the periodontium, may change their physical structure and therefore alter their biological properties. Furthermore, the use of cross-linked collagen membranes and antibacterial agents may significantly inhibit this proteolytic process.

Biodegradation of different synthetic hydrogels made of polyethylene glycol hydrogel/RGD-peptide modifications: an immunohistochemical study in rats

AIM

The aim of the present study was to investigate the pattern of biodegradation of different polyethylene glycol (PEG) hydrogel/RGD-peptide modifications in rats.

MATERIAL AND METHODS

Two different hydrogels were employed: (i) a combination of four-arm PEG-thiol, M(n)=2.3 kDa, and eight-arm PEG-acrylate, M(n)=2.3 kDa (PEG1); and (ii) a combination of four-arm PEG-thiol, M(n)=2.3 kDa, and four-arm PEG-acrylate, M(n)=15 kDa (PEG2). Both PEG1 and PEG2 were either used alone or combined with a nine amino acid cys-RGD peptide (RGD). A non-cross-linked porcine type I and III collagen membrane [BioGide (BG)] served as control. Specimens were randomly allocated in unconnected subcutaneous pouches separated surgically on the back of 60 wistar rats, which were divided into six groups (1, 2, 4, 8, 16, and 24 weeks). Specimens were prepared for histological (tissue integration, foreign body reactions, biodegradation) and immunohistochemical (angiogenesis) analysis.

RESULTS

All materials investigated revealed unimpeded and comparable tissue integration without any signs of foreign body reactions. While BG exhibited transmembraneous blood vessel formation at 1 week, all PEG specimens were just surrounded by a well-vascularized connective tissue. The hydrolytic disruption of PEG1 and PEG1/RGD specimens was associated with an ingrowth of blood vessels at 4 weeks. Biodegradation times were highest for PEG1 (24 weeks)>PEG1/RGD (16 weeks)>BG (4 weeks)>PEG2=PEG2/RGD (2 weeks).

CONCLUSION

Within the limits of the present study, it was concluded that (i) all materials investigated revealed a high biocompatibility and tissue integration, and (ii) hydrogel biodegradation was dependent on PEG composition.

Biodegradation of three different collagen membranes in the rat calvarium: a comparative study

BACKGROUND

Collagen barrier membranes are commonly applied in periodontal and bone-regenerative procedures. Membranes differ in their resorption pattern following implantation, thus influencing clinical outcome. The purpose of this study was to quantitatively evaluate the biodegradation of three different commercially available collagen membranes.

METHODS

Collagen membranes were cut into 5-mm-diameter disks and labeled with aminohexanoyl-biotin-N-hydroxy-succinimide ester. One membrane disk of each type (non-cross-linked [NCL], glutaraldehyde cross-linked [GCL], and ribose cross-linked [RCL]) was implanted on the calvaria of 20 Wistar rats. Block sections were retrieved after 2 days (baseline, two animals), 14 days (10 animals), or 28 days (eight animals). Decalcified histologic sections were stained with streptavidin horseradish peroxidase. Residual membrane thickness and area were measured. Statistical analysis consisted of analysis of variance (ANOVA) with repeated measures.

RESULTS

Statistically significant differences in the amount of residual membrane material were recorded within each membrane (among different time points) and among different membranes at the same time points (P <0.001). At 28 days, the least amount of residual collagen area, expressed as the percentage of baseline, was observed in the NCL group (13.9% +/- 10.25%), followed by the GCL (24.7% +/- 35.11%) and RCL (91.3% +/- 10.35%) groups. Residual membrane thickness, expressed as the percentage of baseline thickness, presented a similar pattern (31% +/- 16.55%, 37% +/- 41.90%, and 94.1% +/- 12.22%, respectively). ANOVA with repeated measures showed a significant interaction between membranes and time (P <0.001).

CONCLUSIONS

The tested membranes differed in their degradation patterns and collagen contents. Membranes should be chosen for each clinical case according to the desired biodegradation characteristics.

Guided bone regeneration at dehiscence-type defects using biphasic hydroxyapatite + beta tricalcium phosphate (Bone Ceramic) or a collagen-coated natural bone mineral (BioOss Collagen): an immunohistochemical study in dogs

The aim of this study was to immunohistochemically investigate bone regeneration following application of either hydroxyapatite+beta tricalcium phosphate (BCG) or a collagen-coated natural bone mineral (BOC) in combination with a collagen membrane at dehiscence-type defects in dogs. Standardized buccal dehiscence defects were surgically created following implant bed preparation in six beagle dogs. Defects were randomly filled with either BOC (BioOss Collagen) or BCG (Bone Ceramic) according to a split-mouth design, and covered with a native porcine derived collagen membrane (BioGide). After 1, 4 and 9 weeks of submerged healing, dissected blocks were processed for immunohistochemical (osteocalcin) and histomorphometrical analysis (residual defect length, new bone-implant contact, area of new bone fill, percentage of osseointegrated bone-graft particles). Both groups revealed a significant decrease in mean residual defect length, and increases in mean new bone-implant contact, bone fill and percentage of osseointegrated bone-graft particles after 4 and 9 weeks of healing. Remaining BCG and BOC granules were completely integrated into a secondarily formed network of spongiosa, but there was no osteoclastic activity at the surface of either type of bone-graft particle. Both BCG and BOC may provide an osteoconductive scaffold to support guided bone regeneration procedures at dehiscence-type defects.