The effect of experimental osteoporosis on bone regeneration: Part 1, histology findings

Healing patterns of alveolar bone following ridge preservation procedures

OBJECTIVES

Examine the histomorphometric bone composition, following alveolar ridge preservation techniques and unassisted socket healing.

MATERIALS AND METHODS

Forty-two patients (42) requiring a single rooted tooth extraction were randomly allocated into three groups (n = 14 per group): Group 1: Guided Bone Regeneration (GBR) using deproteinised bovine bone mineral (DBBM) and a porcine collagen membrane; Group 2: Socket Seal (SS) technique using DBBM and a porcine collagen matrix; Group 3: Unassisted socket healing (Control). Trephined bone biopsies were harvested following a 4-month healing period. Forty-two samples underwent Back-Scattered Electrons -Scanning Electron Microscopy (BSE-SEM) imaging, with 15 samples examined using Xray Micro-Tomography (XMT) (n = 6 for each GBR/SS and n = 3 Control). Images were analysed to determine the percentage (%) of connective tissue, new bone formation, residual DBBM particles and direct bone to DBBM particle contact (osseointegration).

RESULTS

BSE-SEM analysis demonstrated that new bone formation was higher in the Control (45.89% ± 11.48) compared to both GBR (22.12% ± 12.7/p < .004) and SS (27.62% ± 17.76/p < .005) groups. The connective tissue percentage in GBR (49.72% ± 9), SS (47.81% ± 12.57) and Control (47.81% ± 12.57) groups was similar. GBR (28.17% ± 16.64) and SS (24.37% ± 18.61) groups had similar levels of residual DBBM particles. XMT volumetric analysis indicated a lower level of bone and DBBM particles in all test groups, when matched to the BSE-SEM area measurements. Osseointegration levels (DBBM graft and bone) were recorded at 35.66% (± 9.8) for GBR and 31.18% (± 19.38) for SS.

CONCLUSION

GBR and SS ARP techniques presented with less bone formation when compared to unassisted healing. GBR had more direct contact/osseointegration between the DBBM particles and newly formed bone.

Bone regeneration in implant dentistry: Which are the factors affecting the clinical outcome?

The key factors that are needed for bone regeneration to take place include cells (osteoprogenitor and immune-inflammatory cells), a scaffold (blood clot) that facilitates the deposition of the bone matrix, signaling molecules, blood supply, and mechanical stability. However, even when these principles are met, the overall amount of regenerated bone, its stability over time and the incidence of complications may significantly vary. This manuscript provides a critical review on the main local and systemic factors that may have an impact on bone regeneration, trying to focus, whenever possible, on bone regeneration simultaneous to implant placement to treat bone dehiscence/fenestration defects or for bone contouring. In the future, it is likely that bone tissue engineering will change our approach to bone regeneration in implant dentistry by replacing the current biomaterials with osteoinductive scaffolds combined with cells and mechanical/soluble factors and by employing immunomodulatory materials that can both modulate the immune response and control other bone regeneration processes such as osteogenesis, osteoclastogenesis, or inflammation. However, there are currently important knowledge gaps on the biology of osseous formation and on the factors that can influence it that require further investigation. It is recommended that future studies should combine traditional clinical and radiographic assessments with non-invasive imaging and with patient-reported outcome measures. We also envisage that the integration of multi-omics approaches will help uncover the mechanisms responsible for the variability in regenerative outcomes observed in clinical practice.

The effect of experimental diabetes and membrane occlusiveness on guided bone regeneration: A proof of principle study

OBJECTIVES

To evaluate the effect of membrane occlusiveness and experimental diabetes on early and late healing following guided bone regeneration.

MATERIAL AND METHODS

A total of 30 Wistar rats were randomly allocated to three groups: healthy (H), uncontrolled diabetic (UD) and controlled diabetic (CD). A critical size calvarial defect (CSD) was created at the mid-portion of one parietal bone, and it was treated with a double layer of e-PTFE membrane presenting 0.5 mm perforations. The animals were killed at 7 and 30 days of healing, and qualitative and quantitative histological evaluations were performed. Data were compared with the ones previously obtained from other 30 animals (10H, 10UD, 10 CD), where two CSDs were randomly treated with a double-layer e-PTFE occlusive membrane or left empty.

RESULTS

Following application of cell occlusive or cell permeable membranes, significant regeneration can be observed. However, at 30 days in the H group occlusive compared to cell permeable membranes promoted enhanced bone regeneration (83.9 ± 7.3% vs. 52.5 ± 8.6%), while no significant differences were observed within the CD and UD groups. UD led to reduced regeneration compared to H when an occlusive barrier was applied, whereas comparable outcomes to H and CD were observed when placing perforated membranes.

CONCLUSION

The application of cell permeable membranes may have masked the potentially adverse effect of experimental UD on bone regeneration.

CLINICAL RELEVANCE

Membrane porosity might contribute to modulate the bone regenerative response in UD conditions. Future studies are needed to establish the degree of porosity associated with the best regenerative outcomes as well as the underlying molecular mechanisms.

A long-lasting guided bone regeneration membrane from sequentially functionalised photoactive atelocollagen

The fast degradation of collagen-based membranes in the biological environment remains a critical challenge, resulting in underperforming Guided Bone Regeneration (GBR) therapy leading to compromised clinical results. Photoactive atelocollagen (AC) systems functionalised with ethylenically unsaturated monomers, such as 4-vinylbenzyl chloride (4VBC), have been shown to generate mechanically competent materials for wound healing, inflammation control and drug delivery, whereby control of the molecular architecture of the AC network is key. Building on this platform, the sequential functionalisation with 4VBC and methacrylic anhydride (MA) was hypothesised to generate UV-cured AC hydrogels with reduced swelling ratio, increased proteolytic stability and barrier functionality for GBR therapy. The sequentially functionalised atelocollagen precursor (SAP) was characterised via TNBS and ninhydrin colourimetric assays, circular dichroism and UV-curing rheometry, which confirmed nearly complete consumption of collagen's primary amino groups, preserved triple helices and fast (< 180 s) gelation kinetics, respectively. Hydrogel's swelling ratio and compression modulus were adjusted depending on the aqueous environment used for UV-curing, whilst the sequential functionalisation of AC successfully generated hydrogels with superior proteolytic stability in vitro compared to both 4VBC-functionalised control and the commercial dental membrane Bio-Gide®. These in vitro results were confirmed in vivo via both subcutaneous implantation and a proof-of-concept study in a GBR calvarial model, indicating integrity of the hydrogel and barrier defect, as well as tissue formation following 1-month implantation in rats. STATEMENT OF SIGNIFICANCE: Collagen-based membranes remain a key component in Guided Bone Regeneration (GBR) therapy, but their properties, e.g. proteolytic stability and soft tissue barrier functionality, are still far from optimal. This is largely attributed to the complex molecular configuration of collagen, which makes chemical accessibility and structure-function relations challenging. Here, we fabricated a UV-cured hydrogel network of atelocollagen, whereby triple helices were sequentially functionalised with two distinct ethylenically unsaturated monomers. The effects of the sequential functionalisation and UV-curing on the macroscopic properties, degradation behaviour and GBR capability were investigated in vitro and in vivo. The results highlight the key role of the sequential functionalisation and provide important insights for the design of future, longer-lasting resorbable membranes for GBR therapy.

Study on the Local Anti-Osteoporosis Effect of Polaprezinc-Loaded Antioxidant Electrospun Membrane

Background

Compared with the healthy condition, osteoporotic bone defects are often accompanied by poor osteogenesis and excessive reactive oxygen species (ROS), which pose serious challenges to bone augmentation and repair by normal resorbable guided bone regeneration (GBR) membrane.

Purpose

Polaprezinc (PZ) was loaded into polycaprolactone/gelatin (PG) hybrid electrospun nanofibers to fabricate a GBR membrane with antioxidant and osteogenesis ability.

Methods

A series of physicochemical characterization were performed by scanning electron microscopy, Fourier-transform infrared spectroscopy, and water contact angle measurement. In addition to membrane degradation and PZ release detection, membranes were tested for cell viability, differentiation, and protein expression in MC3T3-E1 cells by CCK8, alkaline phosphatase activity, mineralization, and Western blotting assays. The membrane osteogenic capacity in cranial bone defects was studied by micro-CT in vivo.

Results

PZ was successfully doped into the PCL/GEL nanofibers to form a hydrophilic GBR membrane. The cumulative release of PZ was closely related to the membrane degradation behavior. PG/0.4%PZ membranes produced the best protective effect on cell proliferation/differentiation under oxidative stress microenvironment; however, the PG/0.8%PZ membrane was cytotoxic. Western blotting demonstrated that the PZ-loaded membrane upregulated the Nrf2/HO-1/SOD1 signaling molecules in a concentration-dependent manner. In addition, micro-CT results showed an abundant formation of new bones in the PG/0.4%PZ group compared to the PG group.

Conclusion

PZ-loaded degradable PG membranes (especially PG/0.4%PZ) have great potential to accelerate bone regeneration in oxidative stress-related diseases.

Histological and Histomorphometric Analyses of Bone Regeneration in Osteoporotic Rats Using a Xenograft Material

We evaluated the effect of osteoporotic induction after eight weeks of initial healing of bone defects grafted with a xenograft material in a rat model. Bone defects were created in the femoral condyles of 16 female Wistar rats (one defect per rat). The defects were filled with bovine bone (Inter-Oss) granules. After eight weeks of bone healing, rats were randomly ovariectomized (OVX) or sham-operated (SHAM). At 14 weeks of bone healing, all animals were euthanized. Bone specimens were harvested and processed for histological and histomorphometric analyses to assess new bone formation (N-BF%), remaining bone graft (RBG%) and trabecular bone space (Tb.Sp%) within the defect area. After 14 weeks of bone healing, histological evaluation revealed a significant alteration in trabecular bone in OVX rats compared to SHAM rats. There was lower N-BF% in OVX rats (22.5% ± 3.0%) compared to SHAM rats (37.7% ± 7.9%; p < 0.05). Additionally, the RBG% was significantly lower in OVX (23.7% ± 5.8%) compared to SHAM (34.8% ± 9.6%; p < 0.05) rats. Finally, the Tb.Sp% was higher in OVX (53.8% ± 7.7%) compared to SHAM (27.5% ± 14.3%; p < 0.05) rats. In conclusion, within the limitations of this study, inducing an osteoporotic condition in a rat model negatively influenced bone regeneration in the created bone defect and grafted with a xenograft material.

The role of strontium ranelate and guided bone regeneration in osteoporotic and healthy conditions

BACKGROUND/ OBJECTIVES

SR is a chemical agent developed for the treatment of osteoporosis. In vitro, SR enhanced replication of osteoprogenitor cells and bone formation. In vivo, in ovariectomized rats SR prevented the biomechanical deterioration of bone while in non-ovariectomized rats, enhanced bone architecture and increased trabecular and cortical bone mass. The aim of this study was to evaluate the effect of SR on bone healing of calvarial critical size defects treated with a deproteinized bovine bone mineral (DBBM) and a collagen barrier (CM), in healthy and osteoporotic rats.

MATERIAL AND METHODS

Sixty-four, 4-month-old Wistar female rats were used. Osteoporosis was induced by ovariectomy and calcium-deficient diet in half of them. Sixteen ovariectomized (OSR) and 16 healthy (HSR) rats were treated with SR while no medication was administered in the remaining 16 healthy (H) and 16 ovariectomized (O) rats. At 6 weeks after ovariectomy, a 5mm defect was created in each parietal bone of every animal. One defect was treated with DBBM and CM, while the contralateral was left untreated. Qualitative and quantitative histological analysis was performed at 30 and 60 days of healing. A generalized estimating equations test was performed to evaluate the effect of SR and osteoporosis, on new bone formation (NB).

RESULTS

After 30 days of healing, NB in the untreated defects was 3.4%±1.7%, 4.3%±6.2%, 3.2±4.5%, 15.9±23.5% in O, OSR, H and HSR groups, respectively; after 60 days, NB was 4.7%±4.3%, 11.3%±7%, 7.1%±13.2, 12.1%±13.5%, respectively. In the GBR-treated defects, after 30 days, NB was 2.6%±1.4%, 2.4%±1.6%, 4.5%±4.1%, 10.3%±14.4% in O, OSR, H and HSR groups, respectively; after 60 days, NB was 2.2%±1.6%, 4.3%±4.2%, 7%±5.1%, 10.8%±17.4%, respectively. Osteoporosis (p=0.008) and the absence of strontium ranelate treatment (p=0.01) had a negative impact on NB.

CONCLUSION

SR may promote bone formation in calvarial defects in healthy and osteoporotic rats, albeit in a moderate extent.

Photobiomodulation as adjunctive therapy for guided bone regeneration. A microCT study in osteoporotic rat model

Regeneration of diseased bone is challenging. Guided bone regeneration (GBR) has been applied to favor the bone repair. Photobiomodulation (PBM) is also a recognized therapy able to improve bone repair in healthy and diseased individuals. Thus, with the hypothesis that PBM therapy could improve the GBR of diseased bone, this study evaluated the effect of PBM as adjunctive therapy to GBR in osteoporotic rats. Osteoporosis was induced in rats using the oophorectomy model. Then, 5-mm calvaria bone defects were created and treated according to the experimental groups, as follows: with no further treatment (Control); conventional GBR (Membrane), GBR and PBM applied with 3 s, 4 J/cm² and 0.12 J per point (PBM-1) and GBR and PBM applied with 10s, 14 J/cm², 0.4 J per point (PBM-2). PBM therapy (808 nm, 40 mW, 1.42 W/cm²) was applied immediately, 48 and 96 h postoperatively. Four and eight weeks later, the samples were harvested and processed for micro-computerized tomography (Micro CT). Data were statistically compared (p < 0.05). From 4 to 8 weeks mostly significant changes were observed in the PBM groups. The bone volume fraction and number of trabeculae of the PBM groups, especially the PBM-1, were significantly higher than those of Control (p < 0.0001). The values of thickness and separation of the trabeculae and structural model index of the PBM groups were significantly smaller than Control (p < 0.0001). The connectivity density was significantly higher on Membrane and PBM groups than Control (p < 0.0004). The application of PBM as adjunctive therapy to GBR results in enhanced bone formation and maturation in comparison to the conventional GBR in the regeneration of lesions of osteoporotic bone in rats. Overviewing the challenges that face bone regeneration in patients with osteoporosis, our findings open new perspectives on the treatment of bone defects under osteoporotic conditions.

Proteomic and Transcriptomic Approaches for Studying Bone Regeneration in Health and Systemically Compromised Conditions

Bone regeneration is a complex biological process, where the molecular mechanisms are only partially understood. In an ageing population, where the prevalence of chronic diseases with an impact on bone metabolism is increasing, it becomes crucial to identify new strategies that would improve regenerative outcomes also in medically compromised patients. In this context, omics are demonstrating a great potential, as they offer new insights on the molecular mechanisms regulating physiologic/pathologic bone healing and, at the same time, allow the identification of new diagnostic and therapeutic targets. This review provides an overview on the current evidence on the use of transcriptomic and proteomic approaches in bone regeneration research, particularly in relation to type 1 diabetes and osteoporosis, and discusses future scenarios and potential benefits and limitations on the integration of multi-omics. It is suggested that future research will leverage the synergy of omics with statistical modeling and bioinformatics to prompt the understanding of the biology underpinning bone formation in health and medically compromised conditions. With an eye toward personalized medicine, new strategies combining the mining of large datasets and bioinformatic data with a detailed characterization of relevant phenotypes will need to be pursued to further the understanding of disease mechanisms.

PLGA-BMP-2 and PLA-17β-Estradiol Microspheres Reinforcing a Composite Hydrogel for Bone Regeneration in Osteoporosis

The controlled release of active substances-bone morphogenetic protein 2 (BMP-2) and 17β-estradiol-is one of the main aspects to be taken into account to successfully regenerate a tissue defect. In this study, BMP-2- and 17β-estradiol-loaded microspheres were combined in a sandwich-like system formed by a hydrogel core composed of chitosan (CHT) collagen, 2-hidroxipropil γ-ciclodextrin (HP-γ-CD), nanoparticles of hydroxyapatite (nano-HAP), and an electrospun mesh shell prepared with two external electrospinning films for the regeneration of a critical bone defect in osteoporotic rats. Microspheres were made with poly-lactide-co-glycolide (PLGA) to encapsulate BMP-2, whereas the different formulations of 17β-estradiol were prepared with poly-lactic acid (PLA) and PLGA. The in vitro and in vivo BMP-2 delivered from the system fitted a biphasic profile. Although the in vivo burst effect was higher than in vitro the second phases (lasted up to 6 weeks) were parallel, the release rate ranged between 55 and 70 ng/day. The in vitro release kinetics of the 17β-estradiol dissolved in the polymeric matrix of the microspheres depended on the partition coefficient. The 17β-estradiol was slowly released from the core system using an aqueous release medium (Deff = 5.58·10-16 ± 9.81·10-17m2s-1) and very fast in MeOH-water (50:50). The hydrogel core system was injectable, and approximately 83% of the loaded dose is uniformly discharged through a 20G needle. The system placed in the defect was easily adapted to the defect shape and after 12 weeks approximately 50% of the defect was refilled by new tissue. None differences were observed between the osteoporotic and non-osteoporotic groups. Despite the role of 17β-estradiol on the bone remodeling process, the obtained results in this study suggest that the observed regeneration was only due to the controlled rate released of BMP-2 from the PLGA microspheres.

Influence of Cigarette Smoke Inhalation on an Autogenous Onlay Bone Graft Area in Rats with Estrogen Deficiency: A Histomorphometric and Immunohistochemistry Study

PURPOSE

The present study aimed to evaluate the influence of cigarette smoke inhalation on an autogenous onlay bone graft area, either covered with a collagen membrane or not, in healthy and estrogen-deficient rats through histomorphometry and immunohistochemistry.

MATERIALS AND METHODS

Sixty female rats (Wistar), weighing 250-300 g, were randomly divided and allocated into groups (either exposed to cigarette smoke inhalation or not, ovariectomized and SHAM). After 15 days, the test group underwent cigarette smoke inhalation. Sixty days after exposition, autogenous bone grafting was only performed on all right hemimandibles, and the left ones underwent autogenous onlay bone grafting with the collagen membrane (BioGide^®). The graft was harvested from the parietal bone and attached to the animals' jaws (right and left). They were euthanized at 21, 45, and 60 days after grafting. Histological measurements and immunohistochemical analyses were performed, and results were submitted to a statistical analysis.

RESULTS

The addition of a collagen membrane to the bone graft proved more efficient in preserving graft area if compared to the graft area without a collagen membrane and the one associated with cigarette smoke inhalation at 21 (p = 0.0381) and 60 days (p = 0.0192), respectively. Cigarette smoke inhalation combined with ovariectomy promoted a significant reduction of the autogenous graft area at 21 and 60 days. At 45 days, no statistically significant results were observed. In the immunohistochemical analysis, the ovariectomized and smoking subgroups, combined or not with collagen membrane, received moderate and intense immunolabeling at 21 days for Receptor Activator of Nuclear Factor Kappa-B Ligand (RANKL) (p = 0.0017 and p = 0.0381, respectively). For Osteoprotegerin (OPG), intense immunolabeling was observed in most subgroups under analysis at 60 days.

CONCLUSION

Smoking inhalation promoted resorption on the autogenous onlay bone graft, mainly when associated with ovariectomy. Furthermore, when associated with the collagen membrane, a lower resorption rate was observed if compared to the absence of the membrane.

Microporous polysaccharide multilayer coated BCP composite scaffolds with immobilised calcitriol promote osteoporotic bone regeneration both in vitro and in vivo

Incorporating a biomimetic coating and integrating osteoinductive biomolecules into basic bone substitutes are two common strategies to improve osteogenic capabilities in bone tissue engineering. Currently, the underlying mechanism of osteoporosis (OP)-related deficiency of osteogenesis remains unclear, and few treatments target at OP-related bone regeneration. Herein, we describe a self-assembling polyelectrolyte multilayered (PEM) film coating with local immobilisation of calcitriol (Cal) in biphasic calcium phosphate (BCP) scaffolds to promote osteoporotic bone regeneration by targeting the calcium sensing receptor (CaSR). Methods: The ovariectomy-induced functional changes in bone marrow mesenchymal stem cells (BMSCs), protective effects of Cal, and the potential mechanism were all verified. A PEM film composed of hyaluronic acid (HA) and chitosan (Chi) was prepared through layer-by-layer self-assembly. The morphology, growth behaviour, and drug retention capability of the composite scaffolds were characterised, and their biocompatibility and therapeutic efficacy for bone regeneration were systematically explored in vitro and in vivo.Results: The osteogenic differentiation, adhesion, and proliferation abilities of ovariectomised rat BMSCs (OVX-rBMSCs) decreased, in accordance with the deficiency of CaSR. Cal effectively activated osteogenesis in these OVX-rBMSCs by binding specifically to the active pocket of the CaSR structure, while the biomimetic PEM coating augmented OVX-rBMSCs proliferation and adhesion due to its porous surface structure. The PEM-coated scaffolds showed advantages in Cal loading and retention, especially at lower drug concentrations. HA/Chi PEM synergised with Cal to improve the proliferation, adhesion, and osteogenesis of OVX-rBMSCs and promote bone regeneration and BCP degradation in the critical-size calvarial bone defect model of OVX rats. Conclusion: A composite scaffold based on BCP, created by simply combining a biomimetic PEM coating and Cal immobilisation, could be clinically useful and has marked advantages as a targeted, off-the-shelf, cell-free treatment option for osteoporotic bone regeneration.

Effect of Semelil, an Herbal Selenium-Based Medicine, on New Bone Formation in Calvarium of Rabbits

Background

This study aims to analyze the effect of Semelil, an herbal selenium-based medicine, on osteogenesis in rabbit calvarium defects.

Methods

Four identical bony defects (8 mm) were created in the calvarium of 16 New Zealand male rabbits and filled randomly with xenogenic bone substitute material (Bio-Oss®) and semelil herbal drug (ANGIPARS™). One site was filled with Bio-Oss (B); the second site was treated with ANGIPARS (A); the third site was treated with ANGIPARS + Bio-Oss (AB); and the fourth site was left as untreated control (C) and defects were left unfilled. Rabbits were randomly divided into two groups (n = 8) and sacrificed at four and eight weeks. Percentage of new bone formation, type of the newly formed bone, percentage of the remaining xenograft biomaterial, and foreign body reaction (FBR) were evaluated via histological and histomorphometric analyses.

Results

The percentage of new bone formation was significantly different among four groups. The highest effect was observed in AB, followed by A, B, and C groups, respectively. The difference in the mean percentage of new bone formation between four and eight weeks was significant for all four groups (P < 0.001). Regarding bone formation, the interaction effect of A and B was significant at four (P < 0.001) and eight weeks (P = 0.002). ANGIPARS alone and in presence of Bio-Oss enhanced new bone formation at both four and eight weeks (P < 0.001). The mean amount of new bone formation was significantly different at four and eight weeks in groups C (P = 0.008), A (P < 0.001), B (P < 0.001), and AB (P = 0.003). FBR was not observed in any group.

Conclusion

Semelil may be useful as an adjunct to conventional osteoconductive materials in order to enhance osteogenesis.

Collagen and mPCL-TCP scaffolds induced differential bone regeneration in ovary-intact and ovariectomized rats

BACKGROUND

The data on biomaterial-mediated bone regeneration directly comparing commercially available scaffolds in aging and osteoporotic conditions remain sparse.

OBJECTIVE

To investigate the effects of an absorbable collagen sponge (ACS) and a medical grade polycaprolactone-tricalcium phosphate (mPCL-TCP) scaffold on calvarial defect healing in ovary-intact and ovariectomized rats.

METHODS

Forty-two, 5-month old female Sprague-Dawley rats were divided into sham (OVI) or ovariectomy (OVX) groups (n=21). When rats reached 6 months old, 7 mm diameter calvarial defects were created and treated, further dividing each group into blood clot control, mPCL-TCP, or ACS subgroups (n=7). After four weeks, the calvarial specimens were evaluated using micro-computed tomography for bone volume fraction (BVF), and histopathology.

RESULTS

The effects of ovariectomy were confirmed by changes in body, uterine, and vaginal weight, and osteopenia in the femur. A significant increase in BVF was observed in ACS-subgroups compared with their respective control groups (p<0.05). Histopathological analysis revealed no cellular inflammatory infiltrate in any group. Fibrous tissue encapsulated the mPCL-TCP, while the ACS was well-integrated with the bone matrix. The OVX groups presented more osteoid and enlarged marrow cavities compared with the OVI groups.

CONCLUSION

ACS scaffold enhanced calvarial bone regeneration in OVI and OVX rats after four weeks.

Degradation pattern of a porcine collagen membrane in an in vivo model of guided bone regeneration

BACKGROUND AND OBJECTIVE

Although collagen membranes have been clinically applied for guided tissue/bone regeneration for more than 30 years, their in vivo degradation pattern has never been fully clarified. A better understanding of the different stages of in vivo degradation of collagen membranes is extremely important, considering that the biology of bone regeneration requires the presence of a stable and cell/tissue-occlusive barrier during the healing stages in order to ensure a predictable result. Therefore, the aim of this study was to investigate the degradation pattern of a porcine non-cross-linked collagen membrane in an in vivo model of guided bone regeneration (GBR).

MATERIAL AND METHODS

Decalcified and paraffin-embedded specimens from calvarial defects of 18, 10-month-old Wistar rats were used. The defects were treated with a double layer of collagen membrane and a deproteinized bovine bone mineral particulate graft. At 7, 14 and 30 days of healing, qualitative evaluation with scanning electron microscopy and atomic force microscopy, and histomorphometric measurements were performed. Markers of collagenase activity and bone formation were investigated using an immunofluorescence technique.

RESULTS

A significant reduction of membrane thickness was observed from 7 to 30 days of healing, which was associated with progressive loss of collagen alignment, increased collagen remodeling and progressive invasion of woven bone inside the membranes. A limited inflammatory infiltrate was observed at all time points of healing.

CONCLUSION

The collagen membrane investigated was biocompatible and able to promote bone regeneration. However, pronounced signs of degradation were observed starting from day 30. Since successful regeneration is obtained only when cell occlusion and space maintenance exist for the healing time needed by the bone progenitor cells to repopulate the defect, the suitability of collagen membranes in cases where long-lasting barriers are needed needs to be further reviewed.

Dental implants in Sjögren's syndrome patients: A systematic review

Objectives

The Sjögren’s syndrome (SS) is a chronic autoimmune disease that affects salivation and consequently the health of oral tissues. The aim of this systematic review was to investigate the implant survival rate, marginal bone loss (MBL) and biological complications of dental implants in SS patients.

Materials and methods

Eligibility criteria included prospective and retrospective cohort studies, controlled clinical trials, and randomized clinical trials (RCTs). An electronic search without date or language restrictions was carried out in MEDLINE, Cochrane, Web of Science, and LILACS until June 2017. In addition, manual search and in the grey literature were also conducted. The search process, data analysis, and quality assessment were performed by two independent reviewing authors. The protocol of this systematic review was registered in PROSPERO under number CRD42016053277.

Results

The search and selection process yielded 6 studies, published between 1997 and 2016. An average of 93.7% survival in a mean period of 3.97 years of follow-up was observed. A low number of MBL and biological complications were reported by the studies. All the studies analyzed observed an improvement in life quality of subjects with SS and rehabilitated through dental implants.

Conclusions

With the limitations of this review and based on the available data, the dental implant therapy in SS patients seems to present high implant survival rate, low MBL and low biological complications. In addition, all included studies observed an increase in the quality of life of SS patients who were rehabilitated through dental implants.

Maxillary Sinus Floor Augmentation Using an Equine-Derived Graft Material: Preliminary Results in 17 Patients

Objective

Sinus floor elevation with lateral approach is probably the most frequently performed reconstructive procedure to rehabilitate posterior maxilla when a bone deficiency is present. Different graft materials have been proposed and tested, often with high clinical performances and predictable results. Histological analysis is required when evaluating new materials. We investigated human biopsies retrieved after sinus floor elevation procedure by histomorphometric evaluation to test the performance of an equine-derived bone grafting material.

Study Design

Seventeen consecutive patients were enrolled and sinus lift surgeries were performed using an equine bone graft. Six months after surgery, at implant placement, bone samples were collected. Histomorphometry analysis was carried out on decalcified samples.

Results

All surgeries were uneventful and no additional grafting was required prior to implant insertion. Forty percent of new bone formation was detected, which represented the most abundant tissue retrieved, followed by the residual graft material (33%) and fibrous tissue (27%). A significant reduction in particles size demonstrates a remodeling activity of the graft material.

Conclusion

Within the limitations of this study, this equine-derived bone graft proved to be an effective material to induce new bone formation in the sinus floor elevation procedure.

Protein expression during early stages of bone regeneration under hydrophobic and hydrophilic titanium domes. A pilot study

BACKGROUND AND OBJECTIVES

There is significant evidence that, during the early stages of osseointegration, moderately rough hydrophilic (SLActive) surfaces can accelerate osteogenesis and increase bone-to-implant contact in comparison to hydrophobic (SLA) surfaces. However, very little is known regarding the molecular mechanisms behind the influence that surface chemistry modifications to increase hydrophilicity determine on bone healing. The aim of this study was to describe for the first time the proteins and related signalling pathways expressed during early osseous healing stages under SLA and SLActive titanium domes for guided bone regeneration.

MATERIAL AND METHODS

One SLA and 1 SLActive dome with an internal diameter of 5.0 mm and a height of 3.0 mm were secured to the parietal bones of nine 6-month-old male New Zealand rabbits. Three animals were randomly euthanized at 4, 7 and 14 days and the newly formed tissues retrieved under the domes were analysed with liquid chromatography-mass spectrometry/mass spectrometry. STRING and KEGG databases were applied for Gene Ontology and pathway analyses.

RESULTS

A different modulation of several pathways was detected between the 2 groups at all healing times. The main differences in the osseous healing response associated to the 2 surfaces were related to pathways involved in regulating the inflammatory response, differentiation of osteoblast precursors and skeletogenesis. At day 7, the highest number of proteins and the highest cellular activity were observed in both groups, although a more complex and articulated proteome in terms of cellular metabolism and signal transduction was observed in SLActive samples.

CONCLUSION

This is the first study describing the proteome expressed during early healing stages of guided bone regeneration and osseointegration. A combination of enhanced early osteogenic response and reduced inflammatory response were suggested for the hydrophilic group. Future studies are needed to corroborate these findings and explore the molecular effects of different titanium surfaces on the cascade of events taking place during bone formation.

Functionalization of Ti-40Nb implant material with strontium by reactive sputtering

BACKGROUND

Surface functionalization of orthopedic implants with pharmaceutically active agents is a modern approach to enhance osseointegration in systemically altered bone. A local release of strontium, a verified bone building therapeutic agent, at the fracture site would diminish side effects, which could occur otherwise by oral administration. Strontium surface functionalization of specially designed titanium-niobium (Ti-40Nb) implant alloy would provide an advanced implant system that is mechanically adapted to altered bone with the ability to stimulate bone formation.

METHODS

Strontium-containing coatings were prepared by reactive sputtering of strontium chloride (SrCl2) in a self-constructed capacitively coupled radio frequency (RF) plasma reactor. Film morphology, structure and composition were investigated by scanning electron microscopy (SEM), time of flight secondary ion mass spectrometry (ToF-SIMS) and X-ray photoelectron spectroscopy (XPS). High-resolution transmission electron microscopy (HR-TEM) was used for the investigation of thickness and growth direction of the product layer. TEM lamellae were prepared using the focused ion beam (FIB) technique. Bioactivity of the surface coatings was tested by cultivation of primary human osteoblasts and subsequent analysis of cell morphology, viability, proliferation and differentiation. The results are correlated with the amount of strontium that is released from the coating in biomedical buffer solution, quantified by inductively coupled plasma mass spectrometry (ICP-MS).

RESULTS

Dense coatings, consisting of SrOxCly, of more than 100 nm thickness and columnar structure, were prepared. TEM images of cross sections clearly show an incoherent but well-structured interface between coating and substrate without any cracks. Sr2+ is released from the SrOxCly coating into physiological solution as proven by ICP-MS analysis. Cell culture studies showed excellent biocompatibility of the functionalized alloy.

CONCLUSIONS

Ti-40Nb alloy, a potential orthopedic implant material for osteoporosis patients, could be successfully plasma coated with a dense SrOxCly film. The material performed well in in vitro tests. Nevertheless, the Sr2+ release must be optimized in future work to meet the requirements of an effective drug delivery system.

The effect of experimental diabetes and glycaemic control on guided bone regeneration: histology and gene expression analyses

OBJECTIVES

To investigate the effect of experimental diabetes and metabolic control on intramembranous bone healing following guided bone regeneration (GBR).

MATERIAL AND METHODS

Ninety-three Wistar rats were allocated to three experimental groups, healthy (H), uncontrolled diabetes (D) and controlled diabetes (CD). Twenty one days following diabetes induction, a standardised 5-mm defect was created at the mid-portion of each parietal bone. In 75 animals (25H, 25D, 25CD), one defect was treated with an intracranial and extracranial membrane according to the GBR principle, and one defect was left empty (control); five animals per group were then randomly sacrificed at 3, 7, 15, 30 and 60 days and processed for decalcified histology. In 18 animals (6H, 6D, 6CD), both defects were treated according to the GBR principle; three animals from each group were then randomly sacrificed at 7 and 15 days of healing and employed for gene expression analysis.

RESULTS

Application of the GBR therapeutic principle led to significant bone regeneration even in the D group. However, at 15 and 30 days, the osteogenesis process was impaired by uncontrolled diabetes, as shown by the significant reduction in terms of defect closure (38-42%) and newly formed bone (54-61%) compared to the healthy group. The comparison of the D vs. H group at 15 days of healing yielded the largest number of genes with significantly differential expression, among which various genes associated with the ossification process (bmp4, ltbp4, thra and cd276) were identified.

CONCLUSIONS

Uncontrolled diabetes seems to affect early phases of the bone regeneration following GBR. A misregulation of genes and pathways related to cell division, energy production, inflammation and osteogenesis may account for the impaired regeneration process in D rats. Further studies are warranted to optimise the GBR process in this medically compromised patient population.

Influence of a collagen membrane positioned subjacent the sinus mucosa following the elevation of the maxillary sinus. A histomorphometric study in rabbits

OBJECTIVE

To evaluate the healing after elevation of the sinus mucosa when a collagen membrane was placed between the sinus mucosa and a xenograft used as filler.

MATERIALS AND METHODS

Eighteen rabbits were used. Sinus mucosa elevation was performed bilaterally, and a collagen membrane was applied subjacent to the sinus mucosa only at a randomly selected test site. At both sites, a collagenated corticocancellous porcine bone was placed within the elevated space and the access window was covered with a collagen membrane. The animals were sacrificed after 2, 4, and 8 weeks of healing, six animals for group. Ground sections were prepared.

RESULTS

At the histomorphometric evaluation, the elevated area after 2 and 8 weeks was 11.8 and 8.8 mm² at the test, and 10.0 and 5.3 mm² at the control sites, respectively. The available area was obtained subtracting the remaining area occupied by the membrane from the elevated area and, after 8 weeks, was 6.7 ± 0.9 mm² . After 8 weeks of healing, the mineralized new bone within the elevated space was 18.2 ± 5.5% at the test and 26.7 ± 7.7% at the control sites. Within the available space at the test site, the percentage was 27.3 ± 7.0% after 8 weeks of healing. At 2 and 8 weeks of healing, within the elevated space, the xenograft proportion was 30.9 ± 4.4% and 6.9 ± 2.8% at the test, and 35.2 ± 7.3% and 9.6 ± 4.9% at the control sites, respectively.

CONCLUSIONS

The placement of a collagen membrane subjacent the sinus mucosa did not reveal any major morphometric difference. The collagen membrane was not completely resorbed after 8 weeks.

[AGE AND SEX FEATURES OF BONE MINERAL DENSITY IN RATS]

In vivo assessment of bone mineral density (BMD) and bone mineral content (BMC) indices gives an objective description of the possible rates of bone loss during aging and various diseases, as well as response to treatment by various drugs, affecting bone metabolism. This study was conducted on 376 Wistar rats of both genders, divided into 12 age groups using the method of dual-energy X-ray absorptiometry. Studying the parameters of BMD and BMC depending on age and sex has found no bone mass opeak) in rats of both sexes. Bone mineral density indices were increased in both male and female rats during growing, more pronounced in males. These differences are noted in all age groups of animals. Moreover, we have established age and gender particularities of BMC indices in different parts of the skeleton. In female rats, a significant increase of BMD and BMC parameters have been detected in age from 1.5 to 2 months (33%), from 2 to 3 months - by 12.5%. In males, the increase of BMD indices was found to happen 1 month later and it was less pronounced (from 2 to 3 months - 27%, from 4 to 5 months - 5%). In other age periods, the dynamics of BMD indices had only an upward trend, but significant differences different groups were not established. Our results of BMD and BMC indices and their age and gender features can be used for further research in osteology as reference data for modeling of experimental osteoporosis in rats and study of response to the use of different antiosteoporotic drugs.