Defect healing with various bone substitutes

Gene expression, micro-CT and histomorphometrical analysis of sinus floor augmentation with biphasic calcium phosphate and deproteinized bovine bone mineral: A randomized controlled clinical trial

AIMS

The aim of this randomized controlled clinical trial was to compare the gene expression, micro-CT, histomorphometrical analysis between biphasic calcium phosphate (BCP) of 70/30 ratio and deproteinized bovine bone mineral (DBBM) in sinus augmentation.

MATERIALS AND METHODS

Twenty-four patients in need for sinus floor augmentation through lateral approach were randomized into BCP 70/30 ratio or DBBM. After at least 6 months of healing, a total of 24 bone specimens were collected from the entire height of the augmented bone at the area of implant placement and underwent micro-CT, histomorphometric and gene expression analysis. The 12 bone specimens of BCP 70/30 ratio were equally allocated to micro-CT and histologic analysis (test group, n = 6) and gene expression analysis (test group, n = 6). Similarly, the 12 bone specimens of DBBM were also allocated to micro-CT and histologic analysis (control group, n = 6) and gene expression analysis (control group, n = 6). The newly formed bone, remaining graft materials and relative change in gene expression of four target genes were assessed.

RESULTS

The micro-CT results showed no statistically significant difference in the ratio of bone volume to total volume (BV/TV ratio) for the two groups (BCP 41.51% vs. DBBM 40.97%) and the same was true for residual graft material to total volume (GV/TV ratio, BCP 9.97% vs. DBBM 14.41%). Similarly, no significant difference was shown in the histological analysis in terms of bone formation, (BCP 31.43% vs. DBBM was 30.09%) and residual graft area (DBBM 40.76% vs. BCP 45.06%). With regards to gene expression, the level of ALP was lower in both groups of bone grafted specimens compared with the native bone. On the contrary, the level of OSX, IL-1B and TRAP was higher in augmented bone of both groups compared with the native bone. However, the relative difference in all gene expressions between BCP and DBBM group was not significant.

CONCLUSIONS

The BCP, HA/β-TCP ratio of 70/30 presented similar histological and micro-CT outcomes in terms of new bone formation and residual graft particles with DBBM. The gene expression analysis revealed different gene expression patterns between augmented and native bone, but showed no significant difference between the two biomaterials.

Recent Advances in Scaffolds for Guided Bone Regeneration

The rehabilitation of alveolar bone defects of moderate to severe size is often challenging. Currently, the therapeutic approaches used include, among others, the guided bone regeneration technique combined with various bone grafts. Although these techniques are widely applied, several limitations and complications have been reported such as morbidity, suboptimal graft/membrane resorption rate, low structural integrity, and dimensional stability. Thus, the development of biomimetic scaffolds with tailor-made characteristics that can modulate cell and tissue interaction may be a promising tool. This article presents a critical consideration in scaffold's design and development while also providing information on various fabrication methods of these nanosystems. Their utilization as delivery systems will also be mentioned.

Evaluation of the osteoconductive properties of scaffold containing platete-enriched-fibrin (PRF) with three calcium phosphate (TCP) in the alveolar socket repair after tooth extraction: An animal study

Bone regeneration can be accomplished through osteogenesis, osteoinduction, and osteoconduction mechanisms. This study aimed to investigate the properties of the PRF scaffold with tricalcium phosphate nanoparticles in socket preservation in an animal model. Fabrication of PRF performed. In this experimental study, 18 rats were divided into three negative control, PRF, and PRF/TCP groups. The mechanical and chemical tests including swelling rate, degradation time, and MTT tests were applied to the scaffolds. In each animal, the first maxillary right molar was extracted, and extraction sites of test groups were filled with a resorbable biocompatible biomaterial in situ hardening bone substitute. After 2 and 4 weeks all animals were sacrificed and examined histopathologically and with qRT-PCR. Histological results showed TCP in combination with PRF accelerates bone regeneration with the highest amount of lamellar bone and collagen formation compared to the control and PRF alone. Mechanical and chemical tests on the scaffolds showed the addition of TCP to the PRF scaffold decreases the swelling rate and increases the degradation time. qRT-PCR showed expression of osteogenic genes increased significantly (p < 0.05) in PRF/TCP and PRF, respectively. In conclusion, the gelatin hydrogel containing PRF/TCP scaffold led to more bone formation after tooth extraction. Therefore, the injectable PRF\TCP hydrogel is a promising candidate for bone repair and regeneration.

Rabbit calvarial and mandibular critical-sized bone defects as an experimental model for the evaluation of craniofacial bone tissue regeneration

INTRODUCTION

Many studies have aimed to investigate the regeneration potential of bone substitutes through animal models at different defect sites, where the bone healing mechanism varies due to developmental, structural and functional differences. This study aims to develop a rabbit model with two functionally different (non-load-bearing calvarias and load-bearing mandibular) critical-sized defects (CSD) in one rabbit.

MATERIAL & METHOD

The comparison of the "gold standard" autograft to a sham (no graft) control was undertaken in order to validate this model; at the same time, a 3D-printed biphasic calcium phosphate scaffold was implanted to test its utility in the evaluation of new bone substitute materials. Twenty rabbits were selected with both a 10 mm calvaria defect and a 11 mm bicortical semi-cylindrical mandibular defect. The animals were euthanized at 4 and 12 weeks once surgery, microcomputed tomography and histological analysis had been performed.

RESULTS

In the case of the calvaria, the results for the non-healing sham group compared with the healing of those that had undergone the autograft validated the CSD model. But the mandibular defect was not validated, due to the particularity of mandible high mechanical stress and infectious risk.

DISCUSSION

This study showed for the first time that rabbits have a high tolerance for the bilateral double-site CSD model under consideration; and further studies are essential to modify and improve the design of mandibular CSD.

Biomaterials for Periodontal Regeneration

As a widespread chronical disease, periodontitis progressively destroys tooth-supporting structures (periodontium) and eventually leads to tooth loss. Therefore, regeneration of damaged/lost periodontal tissues has been a major subject in periodontal research. During periodontal tissue regeneration, biomaterials play pivotal roles in improving the outcome of the periodontal therapy. With the advancement of biomaterial science and engineering in recent years, new biomimetic materials and scaffolding fabrication technologies have been proposed for periodontal tissue regeneration. This article summarizes recent progress in periodontal tissue regeneration from a biomaterial perspective. First, various guide tissue regeneration/guide bone regeneration membranes and grafting biomaterials for periodontal tissue regeneration are overviewed. Next, the recent development of multifunctional scaffolding biomaterials for alveolar bone/periodontal ligament/cementum regeneration is summarized. Finally, clinical care points and perspectives on the use of biomimetic scaffolding materials to reconstruct the hierarchical periodontal tissues are provided.

Comparison of the osseointegration of implants placed in areas grafted with HA/TCP and native bone

This study evaluated the osseointegration of implants in areas grafted with biphasic ceramic based on hydroxyapatite/β-tricalcium phosphate (HA/TCP) and in native bone (NB). Twenty-eight rats were randomly assigned into two groups of 14 animals each: HA/TCP group: implants installed in areas grafted with HA/TCP and NB group: implants installed in areas of native bone. Bone defects were made in both tibiae of the rats belonging to the HA/TCP group and then filled with this bone substitute. After 60 days, the rats were submitted to surgical procedures for implant placement in grafted areas in both tibiae in the HA/TCP group while the implants were installed directly in native bone in the NB group. The animals were euthanized 15 and 45 days, respectively, after the implant placement. Biomechanical (removal torque), microtomographic (volume of mineralized tissues around the implants), and histomorphometric (Bone-Implant contact-%BIC and bone area between the implant threads-%BBT) analyzes were conducted to assess the osseointegration process. The HA/TCP group showed lower values of removal torque, volume of mineralized tissue around the implants, lower %BIC, and %BBT compared to the NB group in both experimental periods. Osseointegration of implants placed in grafted areas with HA/TCP was lower compared to the osseointegration observed in native bone areas.

Magnesium Modified β-Tricalcium Phosphate Induces Cell Osteogenic Differentiation In Vitro and Bone Regeneration In Vivo

In vitro, in vivo, and clinical studies have shown how the physicochemical and biological properties of β-tricalcium phosphate (β-TCP) work in bone regeneration. This study aimed to improve the properties of β-TCP by achieving optimum surface and bulk β-TCP chemical/physical properties through the hydrothermal addition of magnesium (Mg) and to later establish the biocompatibility of β-TCP/Mg for bone grafting and tissue engineering treatments. Multiple in vitro and in vivo analyses were used to complete β-TCP/Mg physicochemical and biological characterization. The addition of MgO brought about a modest rise in the number of β-TCP surface particles, indicating improvements in alkaline phosphatase (ALP) activity on day 21 (p < 0.05) and in the WST-1assay on all days (p < 0.05), with a corresponding increase in the upregulation of ALP and bone sialoprotein. SEM analyses stated that the surfaces of the β-TCP particles were not altered after the addition of Mg. Micro-CT and histomorphometric analysis from rabbit calvaria critical defects resulted in β-TCP/Mg managing to reform more new bone than the control defects and β-TCP control at 2, 6, and 8 weeks (* p ≤ 0.05, ** p ≤ 0.01, *** p ≤ 0.001, and **** p ≤ 0.0001). The hydrothermal addition of MgO to the β-TCP surfaces ameliorated its biocompatibility without altering its surface roughness resulting from the elemental composition while enhancing cell viability and proliferation, inducing more bone regeneration by osteoconduction in vivo and osteoblastic differentiation in vitro.

Tricalcium phosphate (-containing) biomaterials in the treatment of periodontal infra-bony defects: A systematic review and meta-analysis

OBJECTIVES

This study aimed to investigate the additional clinical benefit of tricalcium phosphate (TCP) (-containing) biomaterials compared to open flap debridement (OFD) in periodontal infra-bony defects.

DATA

A literature search was conducted in Pubmed, Embase and Cochrane library for entries published up to 14th July 2021. All randomized controlled trials (RCTs) that compared a TCP (-containing) material with OFD and studies that assessed a beta-TCP group alone, with vertical defect sites with PPD of ≥ 6 mm and/or presence of infra-bony defects of ≥ 3 mm and a minimum follow-up of 6 months were included. Risk of bias was assessed with the Oxford scale. The random-effects (RE) model was synthesized as differences between weighted average (MD) for probing pocket depth (PPD) and clinical attachment level (CAL) between TCP and OFD groups. An RE analysis was also performed for the beta-TCP group alone.

STUDY SELECTION

Data from 16 RCTs were included in the analysis. Six studies that represented 151 patients and sites were selected for meta-analysis. The overall MD with 95% CI at 6 months was calculated to be -0.47 [-0.83, -0.12; P = 0.0087] and -1.06 [-1.67, -0.46; P = 0.0006] for PPD and CAL, respectively. Whereas MD at 12 months for PPD and CAL was -0.89 [-1.54, -0.23; P = 0.0078] and -1.25 [-1.85, -0.66; P<0.0001], respectively. All results were in favor of TCP (-containing) group over OFD.

CONCLUSIONS

The results of the study suggest that the use of a TCP (-containing) material may have the potential for additional clinical improvement in PPD and CAL compared with OFD in infra-bony defects, given the limitations of the included evidence.

CLINICAL SIGNIFICANCE

The use of TCP as a bone graft substitute is becoming increasingly common. Therefore, it would be advantageous if an adjunctive benefit in the regeneration of infra-bony defects could be demonstrated to facilitate material selection.

Preliminary Animal Study on Bone Formation Ability of Commercialized Particle-Type Bone Graft with Increased Operability by Hydrogel

The purpose of this study was to evaluate the bone-generating ability of a new bovine-derived xenograft (S1-XB) containing hydrogel. For control purposes, we used Bio-Oss and Bone-XB bovine-derived xenografts. S1-XB was produced by mixing Bone-XB and hydrogel. Cell proliferation and differentiation studies were performed to assess cytotoxicities and cell responses. For in vivo study, 8 mm-sized cranial defects were formed in 16 rats, and then the bone substitutes were transplanted into defect sites in the four study groups, that is, a Bio-Oss group, a Bone-XB group, an S1-XB group, and a control (all n = 4); in the control group defects were left empty. Eight weeks after surgery, new bone formation areas were measured histomorphometrically. In the cell study, extracts of Bio-Oss, Bone-XB, and S1-XB showed good results in terms of the osteogenic differentiation of human mesenchymal stem cells (hMSCs) and no cytotoxic reaction was evident. No significant difference was observed between mean new bone areas in the Bio-Oss (36.93 ± 4.27%), Bone-XB (35.07 ± 3.23%), and S1-XB (30.80 ± 6.41%) groups, but new bone area was significantly smaller in the control group (18.73 ± 5.59%) (p < 0.05). Bovine-derived bone graft material containing hydrogel (S1-XB) had a better cellular response and an osteogenic effect similar to Bio-Oss.

Advantages of Porcine Xenograft over Autograft in Sinus Lift: A Randomised Clinical Trial

This study aimed to compare the performance of intra-oral autologous bone grafts versus porcine xenografts in a two-step lateral window sinus lift. This split-mouth randomised controlled trial sequentially enrolled 12 patients with a 6-month follow-up. For each patient, a simultaneous randomised bilateral maxillary sinus lift was performed and filled with autologous bone from the mandible (control) or a porcine xenograft (test). A bone biopsy sample was collected during the implant placement for histological and histomorphometric analysis. CT scans were performed at the beginning and at the end of the trial to assess radiological evolution. A comparison of initial and six-month CT scans indicated statistically significant increases in bone level for both materials (7.8 ± 2.4 mm for autologous and 8.7 ± 2.2 mm for xenograft, p < 0.05), and there were no significant differences between the performance of the two materials over time (p = 0.26). The histological analysis showed various stages of the remodelling process and no cells or other signs of inflammation or infection were visible in both groups. The porcine xenografts presented similar results for the studied variables when compared to autologous bone, being a reasonable alternative for a sinus lift.

Surface Modified β-Tricalcium phosphate enhanced stem cell osteogenic differentiation in vitro and bone regeneration in vivo

A major number of studies have demonstrated Beta-tricalcium phosphate (β-TCP) biocompatibility, bioactivity, and osteoconductivity characteristics in bone regeneration. The aim of this research was to enhance β-TCP's biocompatibility, and evaluate its physicochemical properties by argon glow discharge plasma (GDP) plasma surface treatment without modifying its surface. Treated β-TCP was analyzed by scanning electron microscopy (SEM), energy-dispersive spectrometry, X-ray photoelectron spectroscopy (XPS), X-ray diffraction analysis, and Fourier transform infrared spectroscopy characterization. To evaluate treated β-TCP biocompatibility and osteoblastic differentiation, water-soluble tetrazolium salts-1 (WST-1), immunofluorescence, alkaline phosphatase (ALP) assay, and quantitative real-time polymerase chain reaction (QPCR) were done using human mesenchymal stem cells (hMSCs). The results indicated a slight enhancement of the β-TCP by GDP sputtering, which resulted in a higher Ca/P ratio (2.05) than the control. Furthermore, when compared with control β-TCP, we observed an improvement of WST-1 on all days (p < 0.05) as well as of ALP activity (day 7, p < 0.05), with up-regulation of ALP, osteocalcin, and Osteoprotegerin osteogenic genes in cells cultured with the treated β-TCP. XPS and SEM results indicated that treated β-TCP’s surface was not modified. In vivo, micro-computed tomography and histomorphometric analysis indicated that the β-TCP test managed to regenerate more new bone than the untreated β-TCP and control defects at 8 weeks (p < 0.05). Argon GDP treatment is a viable method for removing macro and micro particles of < 7 μm in size from β-TCP bigger particles surfaces and therefore improving its biocompatibility with slight surface roughness modification, enhancing hMSCs proliferation, osteoblastic differentiation, and stimulating more new bone formation.

Collagen-Based Matrices for Osteoconduction: A Preclinical In Vivo Study

The aim of this study was to evaluate the influence of additional hydroxyapatite (HA) in collagen-based matrices (CM) and membrane placement on bone formation in calvarial defects. Critical size defects in the calvaria of 16 New Zealand White Rabbits were randomly treated with CM or mineralized collagen-based matrices (mCM). Half of the sites were covered with a collagen membrane. Animals were euthanized after 12 weeks of healing. The samples were studied by micro-CT and histology. Newly formed lamellar bone was observed in all samples at the periphery of the defect. In the central areas, however, new bone composed of both woven and lamellar bone was embedded in the soft tissue. Samples treated with mCM showed more residual biomaterial and induced more small bony islands in the central areas of the defects than samples with CM. Nevertheless, a complete defect closure was not observed in any of the samples at 12 weeks. Membrane placement resulted in a decrease in bone density and height. Significant differences between the groups were revealed only between CM groups with and without membrane coverage for bone height in the central area of the defect. Neither mineralization of CM nor membrane placement improved the osteogenic capacity in this particular defect. Nevertheless, mineralisation influenced bone density without a membrane placement and bone volume underneath a membrane. CM may be used as a scaffold in bone regeneration procedures, without the need of a membrane coverage. Further preclinical studies are warrant to optimise the potential of mCM.

The effect of synthetic bone graft substitutes on bone formation in rabbit calvarial defects

The aim of this study was to evaluate the influence of the intensity of the biomimetic hydroxyapatite (HA) coating of α-tricalcium phosphate (α-TCP) on biomaterial degradation and bone formation. Twenty-four female NZW rabbits of approximately 12 weeks of age were used. Critical size defects were randomly treated with 3%:97% HA:α-TCP (BBCP1), 12%:88% HA:α-TCP (BBCP2), and 23%:77% HA:α-TCP (BBCP3), respectively or sham. All defects were covered with a resorbable collagen membrane. Animals were euthanized after 3 and 12 weeks of healing and samples were investigated by micro-CT and histologic analysis. Ingrowth of newly formed woven bone from the original bone at 3-week healing period was observed in all samples. At the 12-week healing period, the new bone in the peripheral area was mainly lamellar and in the central region composed of both woven and lamellar bone. New bony tissue was found on the surface of all three types of granules and at the interior of the BBCP1 granules. Samples with 3% HA showed significantly less residual biomaterial in comparison to the other two groups. Furthermore, BBCP1 significantly promoted new bone area as compared to other three groups and more bone volume as compared to the control. Within its limitations, this study indicated the highest degradation rate in case of BBCP1 concomitant with the highest rate of bone formation. Hence, formation of new bone can be affected by the level of biomimetic HA coating of α-TCP.

Micro-Nano Surface Characterization and Bioactivity of a Calcium Phosphate-Incorporated Titanium Implant Surface

The surface topography of dental implants and micro-nano surface characterization have gained particular interest for the improvement of the osseointegration phases. The aim of this study was to evaluate the surface micro-nanomorphology and bioactivity (apatite forming ability) of Ossean^® surface, a resorbable blast medium (RBM) blasted surface further processed through the incorporation of a low amount of calcium phosphate. The implants were analyzed using environmental scanning electronic microscopy (ESEM), connected to Energy dispersive X-ray spectroscopy (EDX), field emission gun SEM-EDX (SEM-FEG) micro-Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) before and after immersion in weekly refreshed Hank’s balanced salt solution (HBSS) for 28 days. The analysis of the samples before immersion showed a moderately rough surface, with micropits and microgrooves distributed on all of the surface; EDX microanalysis revealed the constitutional elements of the implant surface, namely titanium (Ti), aluminum (Al) and vanadium (V). Limited traces of calcium (Ca) and phosphorous (P) were detected, attributable to the incorporated calcium phosphate. No traces of calcium phosphate phases were detected by micro-Raman spectroscopy. ESEM analysis of the implant aged in HBSS for 28 days revealed a significantly different surface, compared to the implant before immersion. At original magnifications <2000×, a homogeneous mineral layer was present on all the surface, covering all the pits and microgrooves. At original magnifications ≥10,000×, the mineral layer revealed the presence of small microspherulites. The structure of these spherulites (approx. 2 µm diameter) was observed in nanoimmersion mode revealing a regular shape with a hairy-like contour. Micro-Raman analysis showed the presence of B-type carbonated apatite on the implant surface, which was further confirmed by XPS analysis. This implant showed a micro-nano-textured surface supporting the formation of a biocompatible apatite when immersed in HBSS. These properties may likely favor bone anchorage and healing by stimulation of mineralizing cells.

Bone regeneration of a polymeric sponge technique-Alloplastic bone substitute materials compared with a commercial synthetic bone material (MBCP+TM technology): A histomorphometric study in porcine skull

Background

Polymeric sponge technique is recommended for developing the desired porosity of Biphasic calcium phosphate (BCP) which may favor bone regeneration.

Purpose

To investigate the healing of BCP with ratio of HA30/β‐TCP70 (HA30) and HA70/β‐TCP30 (HA70) polymeric sponge preparation, compare to commercial BCP (MBCP+TM).

Materials and Methods

Materials were tested X‐ray diffraction (XRD) pattern and scanning electron microscope (SEM) analysis. In eight male pigs, six calvarial defects were created in each subject. The defects were the filled with 1 cc of autogenous bone, MBCP+TM (MBCP), HA30, HA70, and left empty (negative group). The new bone formations, residual material particles and bone‐to‐graft contacts were analyzed at 4, 8, 12 and 16 weeks.

Results

Fabricated BCP showed well‐distributed porosity. At 16 weeks, new bone formations were 45.26% (autogenous), 33.52% (MBCP), 24.34% (HA30), 19.43% (HA70) and 3.37% (negative). Residual material particles were 1.88% (autogenous), 17.58% (MBCP), 26.74% (HA30) and 37.03% (HA70). These values were not significant differences (Bonferroni correction <0.005). Bone‐to‐graft contacts were 73.68% (MBCP), which was significantly higher than 41.68% (HA30) and 14.32% (HA70; Bonferroni correction <0.017).

Conclusions

Polymeric sponge technique offers well‐distributed porosity. The new bone formation and residual material particles were comparable to MBCP+TM, but the bone‐to‐graft contact was lower than MBCP+TM.

Platelet-rich plasma-enhanced osseointegration of decellularized bone matrix in critical-size radial defects in rabbits

Background

Bone defects represent a common orthopedic condition. With its vast array of donor sources, xenogeneic bone shows considerable potential as a bone defect repair material but may also be associated with immune rejection and reduced osteogenic capacity. Thus, reducing the risks for immune rejection of xenogeneic bone, while improving its osseointegration, are key technical challenges.

Methods

Decellularized bone matrix scaffolds (DBMs) were fabricated by thorough ultrasonic vibration and subjection to chemical biological agents to remove cells and proteins. The DBMs were then mixed with platelet-rich plasma (PRP) under negative pressure. Growth factor concentrations of PRP, as well as the microstructures and biomechanical properties of the system, were examined. Furthermore, osseointegration capacities in the critical-size radial defect rabbit model were verified.

Results

Complete decellularization of the scaffold and limited reductions in mechanical strength were observed. Moreover, the obtained PRP demonstrated various growth factors. Radiographic evaluation and histological analysis verified that more new bone formation occurred in the DBM mixed with PRP group at 6 and 12 weeks after implantation compared with both the blank group and the DBM without PRP group.

Conclusions

Thorough physical and chemical treatments can reduce the probability of immune rejection of DBMs. The novel composite of DBMs mixed with PRP can serve as a promising bone regeneration material.

Effects of additional collagen in biphasic calcium phosphates: a study in a rabbit calvaria

OBJECTIVES

Biphasic calcium phosphates (BCP) are synthetic biomaterials developed as an alternative to the autogenous bone grafts and xenografts. The aim of the present study was to assess the influence of the addition of collagen onto the BCP resorption rate and bone formation.

MATERIAL AND METHODS

Eighteen male NWZ rabbits approximately 12 weeks of age were used. Critical size defects were randomly treated with bilayered BCP materials comprising 12% HA and 88% α-TCP with and without collagen or sham-operated, respectively. All defects were covered with a resorbable collagen membrane. Animals were euthanized after 3 and 12 weeks of healing and investigated by micro-CT, histologic, and histomorphometric analysis.

RESULTS

Woven bone formation was observed from the original bone at 3-week healing in all samples. After 3 months, mainly lamellar new bone in the peripheral area was observed. In the central region, both woven and lamellar bone were seen. Samples containing collagen showed less residual biomaterial than without collagen at both healing periods. Both types of granules were in close contact with new bone, yielding a complete defect closure at 3 months of healing. However, new bone volume and area was similar for both biomaterials.

CONCLUSIONS

Within its limitations, the study results qualify collagen as a biocompatible carrier for BCPs. The presence of collagen indicated neither significant impact on the resorption of the BCPs nor on bone formation.

CLINICAL RELEVANCE

The addition of collagen to BCPs might not be beneficial for the augmentation of extended bone deficiencies.

The effects of hard and soft tissue grafting and individualization of healing abutments at immediate implants: an experimental study in dogs

Purpose

To evaluate the effects of intra-alveolar socket grafting, subepithelial connective tissue grafts, and individualized abutments on peri-implant hard and soft tissue outcomes following immediate implant placement.

Methods

This randomized experimental study employed 5 mongrel dogs, with 4 sites per dog (total of 20 sites). The mesial roots of P3 and P4 were extracted in each hemimandible and immediate dental implants were placed. Each site was randomly assigned to 1 of 4 different treatment groups: standardized healing abutment (control group), alloplastic bone substitute material (BSS) + standardized healing abutment (SA group), BSS + individualized healing abutment (IA group), and BSS + individualized healing abutment + a subepithelial connective tissue graft (IAG group). Clinical, histological, and profilometric analyses were performed. The intergroup differences were calculated using the Bonferroni test, setting statistical significance at P<0.05.

Results

Clinically, the control and SA groups demonstrated a coronal shift in the buccal height of the mucosa (0.88±0.48 mm and 0.37±1.1 mm, respectively). The IA and IAG groups exhibited an apical shift of the mucosa (−0.7±1.15 mm and −1.1±0.96 mm, respectively). Histologically, the SA and control groups demonstrated marginal mucosa heights of 4.1±0.28 mm and 4.0±0.53 mm relative to the implant shoulder, respectively. The IA and IAG groups, in contrast, only showed a height of 2.6 mm. In addition, the height of the mucosa in relation to the most coronal buccal bone crest or bone substitute particles was not significantly different among the groups. Volumetrically, the IA group (−0.73±0.46 mm) lost less volume on the buccal side than the control (−0.93±0.44 mm), SA (−0.97±0.73 mm), and IAG (−0.88±0.45 mm) groups.

Conclusions

The control group demonstrated the most favorable change of height of the margo mucosae and the largest dimensions of the peri-implant soft tissues. However, the addition of a bone substitute material and an individualized healing abutment resulted in slightly better preservation of the peri-implant soft tissue contour.

PLA-Based Mineral-Doped Scaffolds Seeded with Human Periapical Cyst-Derived MSCs: A Promising Tool for Regenerative Healing in Dentistry

Human periapical cyst mesenchymal stem cells (hPCy-MSCs) are a newly discovered cell population innovatively collected from inflammatory periapical cysts. The use of this biological waste guarantees a source of stem cells without any impact on the surrounding healthy tissues, presenting a valuable potential in tissue engineering and regenerative medicine applications. In the present study, hPCy-MSCs were collected, isolated, and seeded on three experimental mineral-doped porous scaffolds produced by the thermally-induced phase-separation (TIPS) technique. Mineral-doped scaffolds, composed of polylactic acid (PLA), dicalcium phosphate dihydrate (DCPD), and/or hydraulic calcium silicate (CaSi), were produced by TIPS (PLA-10CaSi, PLA-5CaSi-5DCPD, PLA-10CaSi-10DCPD). Micro-CT analysis evaluated scaffolds micromorphology. Collected hPCy-MSCs, characterized by cytofluorimetry, were seeded on the scaffolds and tested for cell proliferation, cells viability, and gene expression for osteogenic and odontogenic differentiation (DMP-1, OSC, RUNX-2, HPRT). Micro-CT revealed an interconnected highly porous structure for all the scaffolds, similar total porosity with 99% open pores. Pore wall thickness increased with the percentage of CaSi and DCPD. Cells seeded on mineral-doped scaffolds showed a superior proliferation compared to pure PLA scaffolds (control), particularly on PLA-10CaSi-10DCPD at day 12. A higher number of non-viable (red stained) cells was observable on PLA scaffolds at days 14 and 21. DMP-1 expression increased in hPCy-MSCs cultured on all mineral-doped scaffolds, in particular on PLA-5CaSi-5DCPD and PLA-10CaSi-10DCPD. In conclusion, the innovative combination of experimental scaffolds colonized with autologous stem cells from periapical cyst represent a promising strategy for regenerative healing of periapical and alveolar bone.

Bone Healing in Rabbit Calvaria Defects Using a Synthetic Bone Substitute: A Histological and Micro-CT Comparative Study

Bioactive alloplastic materials, like beta-tricalcium phosphate (β-TCP) and calcium sulfate (CS), have been extensively researched and are currently used in orthopedic and dental bone regenerative procedures. The purpose of this study was to compare the performance of EthOss versus a bovine xenograft and spontaneous healing. The grafting materials were implanted in standardized 8 mm circular bicortical bone defects in rabbit calvariae. A third similar defect in each animal was left empty for natural healing. Six male rabbits were used. After eight weeks of healing, the animals were euthanized and the bone tissue was analyzed using histology and micro-computed tomography (micro-CT). Defects treated with β-TCP/CS showed the greatest bone regeneration and graft resorption, although differences between groups were not statistically significant. At sites that healed spontaneously, the trabecular number was lower (p < 0.05) and trabecular separation was higher (p < 0.05), compared to sites treated with β-TCP/CS or xenograft. Trabecular thickness was higher at sites treated with the bovine xenograft (p < 0.05) compared to sites filled with β-TCP/CS or sites that healed spontaneously. In conclusion, the novel β-TCP/CS grafting material performed well as a bioactive and biomimetic alloplastic bone substitute when used in cranial defects in this animal model.

Evaluation of an In Situ Hardening β-Tricalcium Phosphate Graft Material for Alveolar Ridge Preservation. A Histomorphometric Animal Study in Pigs

The purpose of this study was to investigate the effectiveness of a resorbable alloplastic in situ hardening bone grafting material for alveolar ridge preservation in a swine model. Seven Landrace pigs were used. In each animal, the maxillary left and right deciduous second molars were extracted, and extraction sites were either grafted with a resorbable alloplastic in situ hardening bone substitute, composed of beta-tricalcium phosphate (β-TCP) granules coated with poly(lactic-co-glycolic) acid (PLGA), or left unfilled to heal spontaneously. Animals were euthanized after 12 weeks, and the bone tissue was analyzed histologically and histomorphometrically. Linear changes of ridge width were also clinically measured and analyzed. Pronounced bone regeneration was found in both experimental and control sites, with no statistically significant differences. At the experimental sites, most of the alloplastic grafting material was resorbed and remnants of the graft particles were severely decreased in size. Moreover, experimental sites showed, in a statistically nonsignificant way, less mean horizontal dimensional reduction of the alveolar ridge (7.69%) compared to the control sites (8.86%). In conclusion, the β-TCP/PLGA biomaterial performed well as a biocompatible resorbable in situ hardening bone substitute when placed in intact extraction sockets in this animal model.

Sinus Floor Augmentation Comparing an In Situ Hardening Biphasic Calcium Phosphate (Hydroxyapatite/β-Tricalcium Phosphate) Bone Graft Substitute with a Particulate Biphasic Calcium Phosphate (Hydroxyapatite/β-Tricalcium Phosphate) Bone Graft Substitute: An Experimental Study in Sheep

OBJECTIVE

The aim of the present split-mouth study in sheep was to assess the influence of in situ hardening properties of a biphasic calcium phosphate (BCP) bone graft substitute (BGS) (ratio hydroxyapatite/β-tricalcium phosphate = 60/40) compared with a particulate BGS with the same biphasic core-granule composition without in situ hardening properties on sinus floor augmentation.

MATERIALS AND METHODS

Therefore, bilateral sinus floor augmentation was performed in eight sheep. Poly(lactide-co-glycolide) (PLGA)-coated, in situ hardening biphasic BGS (PLGA-NMP [N-Methyl-2-pyrrolidone]-BCP) was placed at the test site, and a particulate biphasic BGS without PLGA coating (BCP) was used for the contralateral site as a control. Animals were sacrificed after 21 weeks. Sinus augmentation sites were analyzed histologically. The volume was analyzed by computed tomography. Histomorphometric parameters were assessed for the 12 and 21 weeks' time points. Slopes of new bone formation over time were compared with a linear growth regression model.

RESULTS

Bone formation after 12 and 21 weeks of healing was 8.94% (±3.74) and 19.82% (±6.29) for PLGA-NMP-BCP and 7.00% (±2.58) and 14.38% (±4.51) for BCP, respectively. The bone growth rate for PLGA-NMP-BCP was higher than the growth rate for BCP (probability 97.5%). The total fraction of calcified hard tissue (% bone fraction + % biomaterial) was around 46% for both tested biomaterials, 21 weeks after sinus floor augmentation.

CONCLUSION

The in situ hardening BGS (PLGA-NMP-BCP) performed better than the particulate material (BCP) in terms of bone formation rate. The in situ hardening properties of the PLGA-NMP-BCP material mediated by the PLGA coating and NMP solution as plasticizer had no negative influence on the bone formation.

Comparison of three block bone substitutes for bone regeneration: long-term observation in the beagle dog

This study aimed to evaluate the impact of three types of block bone substitute material on bone formation and graft resorption in vivo. Standardized bone defects (n = 4 defects/animal) were created in the calvaria of nine dogs. Block bone substitutes made of deproteinized bovine bone mineral (DBBM), beta-tricalcium phosphate (β-TCP) and a mixture alpha-TCP and hydroxyapatite (α-TCP/HA) were inserted into the bone defects. A fourth defect was left untreated (empty). All sites were covered with a collagenous membrane. Block biopsies were harvested at 3, 6 and 12 months post-implantation and analyzed by micro-CT and histology. Biomaterial absorption was minimal and incorporation within the defect margin was good for all biomaterials. However, β-TCP demonstrated a relatively greater volume of new bone formation and less residual material volume when compared with DBBM and α-TCP/HA. Conversely, α-TCP/HA showed higher osteoconductive potential and a greater new bone area compared with the other two biomaterials. The block bone substitutes used in the present in vivo study showed advantageous in terms of maintenance of their original form in bony defect. However, the positive impact of all biomaterials on new bone formation and replacement of bone was minor even at 12 months. These findings indicate that block bone substitutes are not well suited to vertical bone augmentation. Further investigations are required to improve the insufficient new bone volume for promising clinical results.

Alveolar Ridge Preservation Using a Novel Synthetic Grafting Material: A Case with Two-Year Follow-Up

This case report highlights the use of a novel in situ hardening synthetic (alloplastic), resorbable, bone grafting material composed of beta tricalcium phosphate and calcium sulfate, for alveolar ridge preservation. A 35-year-old female patient was referred by her general dentist for extraction of the mandibular right first molar and rehabilitation of the site with a dental implant. The nonrestorable tooth was “atraumatically” extracted without raising a flap, and the socket was immediately grafted with the synthetic biomaterial and covered with a hemostatic fleece. No membrane was used, and the site was left uncovered without obtaining primary closure, in order to heal by secondary intention. After 12 weeks, the architecture of the ridge was preserved, and clinical observation revealed excellent soft tissue healing without loss of attached gingiva. At reentry for placement of the implant, a bone core biopsy was obtained, and primary implant stability was measured by final seating torque and resonance frequency analysis. Histological analysis revealed pronounced bone regeneration while high levels of primary implant stability were recorded. The implant was successfully loaded 12 weeks after placement. Clinical and radiological follow-up examination at two years revealed stable and successful results regarding biological, functional, and esthetic parameters.

Osteoinductive porous biphasic calcium phosphate ceramic as an alternative to autogenous bone grafting in the treatment of mandibular bone critical-size defects

The bone-induction capacity of a porous biphasic calcium phosphate (pBCP) using heterotopic implantation in mouse (mHI-model) and its efficacy as substitute for autograft in mandibular critical-size defect in rabbit (rabMCSD-model) was investigated. In mHI-model, pBCP was implanted into the thigh muscles and bone formation was histomorphometrically and immunohistochemically evaluated. In rabMCSD-model, 13 mm bone defects were treated with pBCP or autograft and bone repair comparatively evaluated by radiographic and histomorphometric methods. In mHI-model, formed bone and immunolabeling for bone morphogenetic protein-2 and osteopontin were observed in 90% of pBCP implanted samples after 12 weeks. In rabMCSD-model neither statistically significant difference was found in newly formed bone between pBCP and autograft groups at 4 weeks (18.8 ± 5.5% vs 27.1 ± 5.6%), 8 weeks (22.3 ± 2.7% vs 26.2 ± 5.1), and 12 weeks (19.6 ± 4.7% vs 19.6 ± 2.3%). At 12 weeks, the stability and contour of the mandible were restored in both treatments. Near tooth remaining, pBCP particles were covered by small amount of mineralized tissue exhibiting perpendicular attachments of collagen fiber bundles with histological characteristic of acellular cementum. Within the limitations of this study, it was concluded that pBCP is osteoinductive and able to stimulate the new formation of bone and cementum-like tissues in rabMCSD-model, suggesting that it may be an alternative to treatment of large bone defect and in periodontal regenerative therapy. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1546-1557, 2018.

Comparative Efficacies of Collagen-Based 3D Printed PCL/PLGA/β-TCP Composite Block Bone Grafts and Biphasic Calcium Phosphate Bone Substitute for Bone Regeneration

The purpose of this study was to compare bone regeneration and space maintaining ability of three-dimensional (3D) printed bone grafts with conventional biphasic calcium phosphate (BCP). After mixing polycaprolactone (PCL), poly (lactic-co-glycolic acid) (PLGA), and β-tricalcium phosphate (β-TCP) in a 4:4:2 ratio, PCL/PLGA/β-TCP particulate bone grafts were fabricated using 3D printing technology. Fabricated particulate bone grafts were mixed with atelocollagen to produce collagen-based PCL/PLGA/β-TCP composite block bone grafts. After formation of calvarial defects 8 mm in diameter, PCL/PLGA/β-TCP composite block bone grafts and BCP were implanted into bone defects of 32 rats. Although PCL/PLGA/β-TCP composite block bone grafts were not superior in bone regeneration ability compared to BCP, the results showed relatively similar performance. Furthermore, PCL/PLGA/β-TCP composite block bone grafts showed better ability to maintain bone defects and to support barrier membranes than BCP. Therefore, within the limitations of this study, PCL/PLGA/β-TCP composite block bone grafts could be considered as an alternative to synthetic bone grafts available for clinical use.

The Effect of Bisphasic Calcium Phosphate Block Bone Graft Materials with Polysaccharides on Bone Regeneration

In this study, bisphasic calcium phosphate (BCP) and two types of polysaccharide, carboxymethyl cellulose (CMC) and hyaluronic acid (HyA), were used to fabricate composite block bone grafts, and their physical and biological features and performances were compared and evaluated in vitro and in vivo. Specimens of the following were prepared as 6 mm diameter, 2 mm thick discs; BPC mixed with CMC (the BCP/CMC group), BCP mixed with crosslinked CMC (the BCP/c-CMC group) and BCP mixed with HyA (the BCP/HyA group) and a control group (specimens were prepared using particle type BCP). A scanning electron microscope study, a compressive strength analysis, and a cytotoxicity assessment were conducted. Graft materials were implanted in each of four circular defects of 6 mm diameter in calvarial bone in seven rabbits. Animals were sacrificed after four weeks for micro-CT and histomorphometric analyses, and the findings obtained were used to calculate new bone volumes (mm³) and area percentages (%). It was found that these two values were significantly higher in the BCP/c-CMC group than in the other three groups (p < 0.05). Within the limitations of this study, BCP composite block bone graft material incorporating crosslinked CMC has potential utility when bone augmentation is needed.

Enhancing the proliferation of MC3T3-E1 cells on casein phosphopeptide-biofunctionalized 3D reduced-graphene oxide/polypyrrole scaffolds

The CPP-biofunctionalized 3D rGO/PPY scaffold can greatly boost the proliferation and differentiation of MC3T3-E1 cells, especially the 3D rGO/PPY/CPP20 scaffold.

The effect of local application of low-magnitude high-frequency vibration on the bone healing of rabbit calvarial defects-a pilot study

Background

The objective of this pilot study was to evaluate the effect of local application of low-magnitude high-frequency vibration (LMHFV) on the bone healing of rabbit calvarial defects that were augmented with different grafting materials and membranes.

Methods

Four calvarial defects were created in each of two New Zealand rabbits and filled with the following materials: biphasic calcium phosphate (BCP), deproteinized bovine bone mineral covered with a non-cross-linked collagen membrane (BO/BG), biphasic calcium phosphate covered with a strontium hydroxyapatite-containing collagen membrane (BCP/SR), and non-cross-linked collagen membrane (BG). Four defects in one rabbit served as a control, while the other was additionally subjected to the local LMHFV protocol of 40 Hz, 16 min per day. The rabbits were sacrificed 1 week after surgery. Histomorphometric analysis was performed to determine the percentages of different tissue compartments.

Results

Compared to the control defects, the higher percentage of osteoid tissue was found in LMHFV BG defects (35.3 vs. 19.3%), followed by BCP/SR (17.3 vs. 2.0%) and BO/BG (9.3 vs. 1.0%). The fraction occupied by the residual grafting material varied from 40.3% in BO/BG to 22.3% in BCP/SR LMHFV defects. Two-way models revealed that material type was only significant for the osteoid (P= 0.045) and grafting material (P = 0.001) percentages, while the vibration did not provide any statistical significance for all histomorphometric outcomes (P > 0.05).

Conclusion

Local application of LMHFV did not appear to offer additional benefit in the initial healing phase of rabbit calvarial defects. Histomorphometric measurements after 1 week of healing demonstrated more pronounced signs of early bone formation in both rabbits that were related with material type and independent of LMHFV.

Comparative clinical and radiographic evaluation of mineralized cancellous bone allograft (puros®) and autogenous bone in the treatment of human periodontal intraosseous defects: 6-months follow-up study

AIMS

Several materials have been introduced as bone grafts, i.e., autografts, allograft, xenografts, and alloplastic grafts, and studies have shown them to produce greater clinical bone defect fill than open flap debridement alone. The aim of this clinical and radiological 6-month study was to compare and evaluate the clinical outcome of deep intraosseous defects following reconstructive surgery with the use of mineralized cancellous bone allograft (Puros®) or autogenous bone.

MATERIALS AND METHODS

Ten patients with 12 sites exhibiting signs of moderate generalized chronic periodontitis were enrolled in the study. The investigations were confined to two and three-walled intra bony defects with a preoperative probing depth of ≥5 mm. Six of these defects were treated with Puros® (group A) the remaining six were treated with autogenous bone graft (group B). Allocation to the two groups was randomized. The clinical parameters, plaque index (PI), gingival index (GI), probing pocket depth (PPD), clinical attachment level (CAL), and bone fill, were recorded at different time intervals at the baseline, 1 month, 3 months, and 6 months. Intraoral radiographs were taken using standardized paralleling cone technique at baseline, 1, 3, and 6 months. Statistical analysis was done by using the one-way analysis of variance (ANOVA) followed by Tukey highly significant difference.

RESULTS

Both groups resulted in decrease in probing depth (group A, 3.0 mm; group B, 2.83 mm) and gain in clinical attachment level (group A, 3.33 mm; group B, 3.0 mm) over a period of 6 months, which was statistically insignificant.

CONCLUSION

Within the limitations of the present study, it can be concluded that both mineralized cancellous bone allograft (Puros®) or autogenous bone result in significant clinical improvements.

Histologic and histomorphometric evaluation of two grafting materials Cenobone and ITB-MBA in open sinus lift surgery

Aims and Objectives:

Alveolar ridge reduction caused after tooth extraction can be minimized through ridge preservation and application of graft materials. The aim of this study was to compare the histologic and histomorphometric aspects of bone particulated allografts, Cenobone and ITB-MBA, in the reconstruction of vertical alveolar ridge after maxillary sinus augmentation.

Materials and Methods:

This clinical trial was performed among 20 patients. The participants were randomly divided into two groups of 10 participants. The first group received Cenobone and the second group received ITB-MBA. Tissue samples were prepared 6 months later at the time of implant installation and after successful maxillary sinus floor augmentation. Tissue sections were examined under a light microscope. The data were analyzed by Chi-square and t-test.

Results:

The mean trabecular thickness of the samples in the Cenobone group was 13.61 ± 7.47 μm compared to 13.73 ± 7.37 μm in the ITB-MBA group (P = 0.93). A mild inflammation process (Grade 1) was detected in both the groups. The amount of remaining biomaterial in the Cenobone group was estimated to be 8 ± 19% vs. 7 ± 12% in the ITB-MBA group (P = 0.30). Bone formation was reported 49.71% in the Cenobone group vs. 40.76% in the ITB-MBA group (P = 0.68). The mean newly formed vessel in the Cenobone group was 0.64 ± 0.7 vs. 1.5 ± 2.3 in the ITB-MBA group (P = 0.14).

Conclusions:

There was no significant difference between the two groups of patients regarding trabecular thickness, remaining biomaterial allograft, and the density of blood vessels after sinus floor elevation; hence, there was no difference between the two groups regarding implant outcome. More designed studies as randomized controlled trials and controlled clinical trials, which evaluate the long-term implant outcome; comparing the different bone graft materials is also required to improve evidence on survival and success rate.

Recombinant human bone morphogenetic protein (rhBMP)9 induces osteoblast differentiation when combined with demineralized freeze-dried bone allografts (DFDBAs) or biphasic calcium phosphate (BCP)

OBJECTIVES

Recently, recombinant human bone morphogenetic protein 9 (rhBMP9) has been characterized as one of the most osteogenic growth factors among the 15 human BMPs. The aim of the present study was to investigate the effects of rhBMP9 in comparison to the clinically utilized rhBMP2 on in vitro cell behavior when combined with two bone graft materials including demineralized freeze-dried bone allografts (DFDBAs) and biphasic calcium phosphate (BCP).

MATERIALS AND METHODS

The absorption and release kinetics of rhBMPs from DFDBA and BCP were investigated by ELISA. Moreover, murine bone stromal ST2 cell behavior was investigated on DFDBA or BCP seeded on (1) graft only, (2) rhBMP2 (10 ng/ml), (3) rhBMP2 (100 ng/ml), (4) rhBMP9 (10 ng/ml), and (5) rhBMP9 (100 ng/ml). The effects of rhBMPs on DFDBA and BCP were assessed for cell adhesion, proliferation, and osteoblast differentiation by alkaline phosphatase (ALP) activity, alizarin red staining, and real-time PCR for genes encoding Runx2, ALP, and bone sialoprotein (BSP).

RESULTS

While both BMPs were gradually released from DFDBA and BCP over time, significantly higher adsorption was observed on BCP when compared to DFDBA. Cell attachment and proliferation was higher on BCP with little influence of either rhBMP2/9. Despite rhBMPs having relatively no effect on cell attachment/proliferation, a pronounced and marked effect was observed on osteoblast differentiation for both rhBMP2/9. Interestingly, it was observed that rhBMP9 induced significantly higher ALP activity, alizarin red staining, and messenger RNA (mRNA) levels of ALP and BSP when compared to rhBMP2. Our results also revealed higher differentiation for rhBMP2/9 with BCP when compared to DFDBA most likely as a result of higher growth factor adsorption.

CONCLUSION

While both rhBMP2/9 combined with DFDBA or BCP induced osteoblast differentiation, rhBMP9 induced greater osteoblast differentiation when compared to rhBMP2.

CLINICAL RELEVANCE

rhBMP9 may be a recombinant growth factor with higher potential to induce new bone formation when compared to rhBMP2. Further in vivo studies are necessary to characterize its regenerative potential in various animal models.

In vivo evaluation of shark teeth-derived bioapatites

OBJECTIVE

The present work proposes the shark teeth as a new source of bioapatites for bone filler applications in maxillary sinus elevation, periodontal regeneration or implants placement. This abundant fishing by-product provides an improved hydroxyapatite (HA) with fluorine contributions. The in vivo evaluation of osteointegration and bone mineral density levels promoted by these marine bioapatites was the main objective.

MATERIALS AND METHODS

Marine bioapatite granules of two sizes (1 mm, <20 μm) were obtained and characterized (XRD, SEM, ICP-OES) to determine morphology and composition. In vivo evaluation was performed, after bioapatites implantation in critical defects of parietal bone of 25 rats, for 3 weeks. Commercial synthetic HA/βTCP (60/40%) material and unfilled defects were used as controls. Radiology, micro-CT, histology and quantification of bone mineral density are presented.

RESULTS

These marine bioapatites presented a globular porous morphology. A biphasic composition ~70% apatitic (HA, apatite-CaF, fluorapatite) and ~30% non-apatitic phase (whitlockite, tricalcium bis(orthophosphate)), with contributions of F (1.0 ± 0.5%wt), Na (0.9 ± 0.2%wt) and Mg (0.65 ± 0.04%wt) was confirmed. After implantation period, higher osteointegration of 1-mm marine bioapatites than commercial synthetic granules was observed, together with bone formation from the defect surroundings but also at central area (potential osteoinductive properties). New bone cells penetrated inside pores and inter-granular cavities. Higher bone mineral density, in both 1-mm and <20-μm granules, than on commercial synthetic graft was determined, being significant in 1-mm bioapatites (a P < 0.05).

CONCLUSION

Shark teeth bioapatites were successfully validated as new functionally efficient bone filler in rat model, promoting significantly increased bone mineral density than synthetic control.

In vitro characterization of an osteoinductive biphasic calcium phosphate in combination with recombinant BMP2

BACKGROUND

The repair of alveolar bone defects with growth factors and bone grafting materials has played a pivotal role in modern dentistry. Recombinant human bone morphogenetic protein-2 (rhBMP2), an osteoinductive growth factor capable of cell recruitment and differentiation towards the osteoblast lineage, has been utilized in combination with various biomaterials to further enhance new bone formation. Recently, a group of novel biphasic calcium phosphate (BCP) bone grafting materials have been demonstrated to possess osteoinductive properties by demonstrating signs of ectopic bone formation. The aim of the present study was to study the effects of rhBMP2 in combination with osteoinductive BCP bone grafts on osteoblast cell behaviour.

METHODS

MC3T3-E1 pre-osteoblasts were seeded on 1) control tissue culture plastic, 2) 10 mg of BCP alone, 3) 100 ng rhBMP2, and 4) 100 ng rhBMP2+ 10 mg of BCP and analyzed for cell recruitment via a Transwell chamber, proliferation via an MTS assay and differentiation as assessed by alkaline phosphatase (ALP) activity, alizarin red staining and real-time PCR for osteoblast differentiation markers including Runx2, collagen1, ALP, and osteocalcin (OCN).

RESULTS

rhBMP2 was able to significantly upregulate cell recruitment whereas the addition of BCP as well as BCP alone had no additional ability to improve osteoblast recruitment. Both BCP and rhBMP2 were able to significantly increase cell proliferation at 3 and 5 days post seeding and cell number was further enhanced when rhBMP2 was combined with BCP. In addition, the combination of rhBMP2 with BCP significantly improved ALP activity at 7 and 14 days post seeding, alizarin red staining at 14 days, and mRNA levels of Runx2, ALP and osteocalcin when compared to cells seeded with rhBMP2 alone or BCP alone.

CONCLUSIONS

The results from the present study demonstrate that 1) the osteoinductive potential of BCP bone particles is equally as osteopromotive as rhBMP2 on in vitro osteoblast differentiation and 2) BCP particles in combination with rhBMP2 is able to further increase the osteopromotive differentiation of osteoblasts in vitro when compared to either rhBMP2 alone or BCP alone. Future animal testing is further required to investigate this combination approach on new bone formation.

The improved biological response of shark tooth bioapatites in a comparative in vitro study with synthetic and bovine bone grafts

Autologous bone is considered to be the gold standard for bone tissue regeneration, providing more highly efficient functional responses compared to synthetic materials, and avoiding the rejection risks of allogenic grafts. However, it presents limitations for certain types of surgery due to its high resorption levels and donor site morbidity. Different biphasic synthetic composites, based onnon-apatitic calcium phosphates enriched with apatitic phases-such as hydroxyapatite, and bioderived bone grafts of bovine and porcine origin-are proposed as lower resorption materials due to their higher crystalline structure. The present work proposes two new sources of bioapatites for bone filler applications obtained from the dentine and enameloid of shark teeth, respectively. These bioapatites each present a characteristic apatite-based composition and additional enrichments of specific trace elements, such as magnesium and fluorine, with proven roles in bone metabolism. Their processing and physicochemical characterization (SEM, FT-Raman and XRD) is presented, together with an in vitro evaluation of osteogenic activity compared to a commercial bovine mineralized matrix and synthetic HA/β TCP grafts. The results proved the globular morphology (0.5-1.5 μm) and porosity (~50 μm and ~0.5-1 μm) of shark dentine bioapatites with biphasic composition: apatitic (hydroxyapatite and apatite-(CaF)), non-apatitic (whitlockite), and an apatitic phase (fluorapatite), organized in oriented crystals in enameloid bioapatites. An evaluation of the pre-osteoblast MC3T3-E1 morphology revealed the colonization of pores in dentine bioapatites and an aligned cell growth in the oriented enameloid crystals. A higher proliferation (p  <  0.01) was detected at up to 21 d in both the shark bioapatites and synthetic biphasic graft with respect to the bovine mineralized matrix. Finally, the great potential of porous biphasic dentine bioapatites enriched with Mg and the aligned fluorapatite crystals of enameloid bioapatites in promoting greater osteogenic activity was confirmed with a significantly increased ALP synthesis (p  <  0.01) compared to the commercial grafts.

Osteoinductive potential of a novel biphasic calcium phosphate bone graft in comparison with autographs, xenografts, and DFDBA

OBJECTIVES

Since the original description of osteoinduction in the early 20th century, the study and development of innovative biomaterials has emerged. Recently, novel synthetic bone grafts have been reported with potential to form ectopic bone in vivo. However, their full characterization in comparison with other leading bone grafts has not been investigated. The aim of this study was to determine the osteoinductive potential of bone grafts by comparing autogenous bone grafts, demineralized freeze-dried bone allografts (DFDBA), a commonly utilized natural bone mineral (NBM) from bovine origin (Bio-Oss), and a newly developed biphasic calcium phosphate (BCP).

MATERIALS AND METHODS

Grafts were compared in vitro for their ability to stimulate bone marrow stromal cell (BMSC) migration, proliferation, and differentiation as assessed by quantitative real-time PCR for genes coding for bone markers including Runx2, collagen I, and osteocalcin. Furthermore, bone grafts were implanted in the calf muscle of 12 beagle dogs to determine their potential to form ectopic bone in vivo.

RESULTS

The in vitro results demonstrate that both autografts and DFDBA show potential for cell recruitment, whereas only autografts and BCP demonstrated the ability to differentiate BMSCs toward the osteoblast lineage. The in vivo ectopic bone model demonstrated that while NBM particles were not osteoinductive and autogenous bone grafts were resorbed quickly in vivo, ectopic bone formation was reported in DFDBA and in synthetic BCP grafts.

CONCLUSION

The modifications in nanotopography and chemical composition of the newly developed BCP bone grafts significantly promoted ectopic bone formation confirming their osteoinductive potential. In conclusion, the results from this study provide evidence that synthetic bone grafts not only serve as a three-dimensional scaffold but are also able to promote osteoinduction.

Gene expression profiles in guided bone regeneration using combinations of different biomaterials: a pilot animal study

OBJECTIVES

The aim of this study was to investigate the gene expression profile related to guided bone regeneration (GBR) at the early healing stage while using combinations of different biomaterials.

MATERIALS AND METHODS

Cranial defects in 4 New Zealand rabbits were filled with A) biphasic calcium phosphate/experimental pericardium-derived collagen membrane, B) Bio-Oss^® /Bio-Gide^® , C) biphasic calcium phosphate/strontium hydroxyapatite-containing collagen membrane and D) Bio-Oss^® /strontium hydroxyapatite-containing collagen membrane. Seven days after surgery, one animal was subjected to histological observation and histomorphometric analysis, and three animals to real-time quantitative reverse transcription polymerase chain reaction (PCR). An RT² Profiler PCR Array (PANZ-026Z, QIAGEN, QIAGEN Sciences, Germantown, MD, USA) was conducted to observe the gene expression profile of groups A, C and D as compared with the control group B.

RESULTS

The analysis showed 9 of the 84 genes on the array to be significantly different in the three experimental groups (six genes in group D, four in group C and one in group A). Group D demonstrated the most changes in gene expression profile at day 7. Genes that were significantly down-regulated (AHSG, EGF) or up-regulated (CDH11, MMP13, GLI1 and MCSF) are responsible for early-stage bone formation, bone remodeling and pre-osteoclast development. The gene expression profile of this group correlated with the histological findings, as this group showed the higher formation of osteoid as compared with the other groups.

CONCLUSION

Gene expression patterns at early-stage healing of GBR-treated defects appear to be related to the biomaterial used. The combination of Bio-Oss^® and strontium hydroxyapatite-containing collagen membrane showed the most pro-osteogenic gene regulation profile (group D), implying the stimulation of key transcriptional factors, which appeared to translate into the up-regulation of the osteogenic process and earlier bone formation.

Effects of a collagen membrane positioned between augmentation material and the sinus mucosa in the elevation of the maxillary sinus floor. An experimental study in sheep

OBJECTIVE

To assess the influence of a collagen membrane placed subjacent to a pristine sinus mucosa on the healing outcome of a sinus floor elevation procedure.

MATERIALS AND METHODS

Eight Pelibuey sheep (Cubano rojo) underwent sinus floor elevation on both sides of the maxilla. At a randomly selected side (test), a collagen membrane was placed subjacent to the sinus mucosa, while the contralateral side (control) was left without the placement of a membrane. Deproteinized bovine bone mineral (DBBM) was used to fill the space created. A collagen membrane was placed bilaterally to cover the access osteotomy. After 4 months, biopsies were harvested and ground sections prepared. Morphometric analysis was performed in four different regions, three within the elevated area and one at the site of the osteotomy.

RESULTS

The total percentages of mineralized new bone within the elevated area were 29.4 ± 16.2% and 30.9 ± 9.2% and of marrow spaces 44.0 ± 23.0% and 45.6 ± 14.1%, at the Non-membrane and at the Membrane sites, respectively. A low content of connective tissue within the elevated area was noticed. A higher content of connective tissue was found in the osteotomy region, however. Remnants of DBBM granules were found at a percentage of 17-19%. No statistically significant differences were observed between test and control sites.

CONCLUSION

The application of a collagen membrane subjacent to the Schneiderian mucosa in a sinus floor elevation procedure did not influence the healing outcomes at all.

Effectiveness of biphasic calcium phosphate block bone substitutes processed using a modified extrusion method in rabbit calvarial defects

PURPOSE

This study evaluated the mechanical and structural properties of biphasic calcium phosphate (BCP) blocks processed using a modified extrusion method, and assessed their in vivo effectiveness using a rabbit calvarial defect model.

METHODS

BCP blocks with three distinct ratios of hydroxyapatite (HA):tricalcium phosphate (TCP) were produced using a modified extrusion method:HA8 (8%:92%), HA48 (48%:52%), and HA80 (80%:20%). The blocks were examined using scanning electron microscopy, X-ray diffractometry, and a universal test machine. Four circular defects 8 mm in diameter were made in 12 rabbits. One defect in each animal served as a control, and the other three defects received the BCP blocks. The rabbits were sacrificed at either two weeks (n=6) or eight weeks (n=6) postoperatively.

RESULTS

The pore size, porosity, and compressive strength of the three types of bone block were 140-170 µm, >70%, and 4-9 MPa, respectively. Histologic and histomorphometric observations revealed that the augmented space was well maintained, but limited bone formation was observed around the defect base and defect margins. No significant differences were found in the amount of new bone formation, graft material resorption, or bone infiltration among the three types of BCP block at either of the postoperative healing points.

CONCLUSIONS

Block bone substitutes with three distinct compositions (i.e., HA:TCP ratios) processed by a modified extrusion method exhibited limited osteoconductive potency, but excellent space-maintaining capability. Further investigations are required to improve the processing method.

Regeneration of rabbit calvarial defects using biphasic calcium phosphate and a strontium hydroxyapatite-containing collagen membrane

OBJECTIVES

Biphasic calcium phosphate (BCP) composed of 10% hydroxyapatite (HA) and 90% beta-tricalcium phosphate has been developed. Recently, a strontium hydroxyapatite-containing collagen membrane (Sr) was shown to stimulate early bone formation in rat calvarial defects at 4 weeks postoperatively, as compared with a cross-linked collagen membrane, for guided bone regeneration (GBR). The objective of this study was to evaluate these novel biomaterials for GBR in relation to a non-cross-linked collagen membrane (BG) and deproteinized bovine bone mineral (BO).

MATERIALS AND METHODS

Twenty New Zealand rabbits were used in this study. Four defects of 7 mm in diameter were created in each rabbit, and three of the defects were treated with BG/BO, Sr/BO, and Sr/BCP. Ten rabbits were sacrificed at 12 and 24 weeks, respectively. Histological and histomorphometric analyses were conducted. Volumetric densities of mineralized new bone (MNB), bone marrow (BM), residual grafting material (RG), and non-mineralized connective tissue (NCT) were determined for each group.

RESULTS

After 12 weeks, Sr/BCP yielded more MNB than BG/BO and Sr/BO with no significant difference among the three groups. After 24 weeks, however, Sr/BCP demonstrated significantly more MNB than BG/BO and Sr/BO. Both after 12 and 24 weeks, Sr/BCP showed significantly less RG than BG/BO and Sr/BO. There was a significant increase in MNB in Sr/BCP from 12 to 24 weeks.

CONCLUSIONS

In defects grafted with BCP, more MNB was formed while less RG remained, than in defects grafted with BO. The Sr membrane was as effective as BG when comparing Sr/BO with BG/BO.

Bone regenerative efficacy of biphasic calcium phosphate collagen composite as a carrier of rhBMP-2

OBJECTIVES

This study compared the bone regenerative effects of a recombinant human bone morphogenetic protein 2 (rhBMP-2)-loaded collagen-based biphasic calcium phosphate composite (BCPC) and rhBMP-2-loaded biphasic calcium phosphate (BCP).

MATERIAL AND METHODS

The in vitro release profiles of rhBMP-2-loaded BCP and BCPC were measured. The animal surgery was performed on ten rabbits. Four 8-mm-diameter circular calvarial defects were made and filled with BCP, BCPC, rhBMP-2-loaded BCP (BMP + BCP) and rhBMP-2-loaded BCPC (BMP + BCPC). The animals were euthanized either 2 or 8 weeks after surgery.

RESULTS

The initial burst release of rhBMP-2 was greater for BCP than for BCPC, and both presented a slow release pattern thereafter. In rabbit calvarial defects, the space maintaining capability and graft resorption of all experimental groups did not show statistical differences at 2 and 8 weeks. New bone formation in the rhBMP-2-loaded groups was greater than in the non-loaded groups at both weeks, but the amount of new bone was comparable between both rhBMP-2-loaded groups at both weeks. There was a distinct histologic difference between the BMP + BCP and BMP + BCPC groups at 2 weeks; the new bone formation occurred more in the intergranular spaces and the BCP-to-bone contact was greater in the BMP + BCPC group, but these differences were no longer discernible at 8 weeks.

CONCLUSIONS

BCP- and BCPC-loaded rhBMP-2 significantly improved bone regeneration and BCPC led to a dense network of new bone and bone particles during the early healing period. BCPC can therefore be considered as a promising candidate for carrying rhBMP-2.