The Effects of Recombinant Human Bone Morphogenetic Protein-2-Loaded Tricalcium Phosphate Microsphere-Hydrogel Composite on the Osseointegration of Dental Implants in Minipigs

Concentration-Dependent Efficacy of Recombinant Human Bone Morphogenetic Protein-2 Using a HA/β-TCP Hydrogel Carrier in a Mini-Pig Vertebral Oblique Lateral Interbody Fusion Model

Bone morphogenetic protein-2 (BMP-2) is used in the treatment of degenerative spinal disease and vertebral fractures, spine fusion, dental surgery, and facial surgery. However, high doses are associated with side effects such as inflammation and osteophytes. In this study, we performed spinal fusion surgery on mini-pigs using BMP-2 and a HA/β-TCP hydrogel carrier, and evaluated the degree of fusion and osteophyte growth according to time and dosage. Increasing the dose of BMP-2 led to a significantly higher fusion rate than was observed in the control group, and there was no significant difference between the 8-week and 16-week samples. We also found that the HA + β-TCP hydrogel combination helped maintain the rate of BMP-2 release. In conclusion, the BMP-2-loaded HA/β-TCP hydrogel carrier used in this study overcame the drawback of potentially causing side effects when used at high concentrations by enabling the sustained release of BMP-2. This method is also highly efficient, since it provides mineral matter to accelerate the fusion rate of the spine and improve bone quality.

Effects of rhBMP-2-loaded hydroxyapatite granules/beta-tricalcium phosphate hydrogel (HA/β-TCP/hydrogel) composite on a rat model of caudal intervertebral fusion

The effects and inflammation-related side effects of bone morphogenetic protein (BMP)-2 on posterior lumbar interbody fusion are controversial. One of the potential causes for the inconsistent results is the uncontrolled release of BMP-2 from the collagen carrier. Therefore, BMP delivery systems that support effective bone regeneration while attenuating the side effects are strongly sought for. We developed NOVOSIS putty (NP), a novel composite material of hydroxyapatite (HA), beta-tricalcium phosphate (β-TCP)/hydrogel, and BMP-2, which can sustainably release BMP-2 over 2 weeks. This study was aimed at comparing the effects and side effects of NP and collagen sponge (CS) containing BMP-2 using a rat caudal intervertebral fusion model. The fusion rates of NP with low and high doses of BMP-2 were significantly higher than those of an iliac bone (IB) graft, but those of CS with low and high doses of BMP-2 were not different from those of the IB graft. Furthermore, the incidences of ectopic bone formation and soft tissue swelling were significantly lower in the NP group than in the CS group. The HA/β-TCP/hydrogel carrier enabled superior bone induction with low-dose BMP-2 and decreased the incidence of side effects caused by high-dose BMP-2 vis-à-vis the collagen carrier.

A novel BMP-2-loaded hydroxyapatite/beta-tricalcium phosphate microsphere/hydrogel composite for bone regeneration

Although bone morphogenetic protein (BMP) has potent osteoinductivity, the potential adverse events attributed to its burst release prevent its widespread clinical application. Therefore, there is a strong need for BMP delivery systems that maximize osteoinductivity while preventing adverse effects. We evaluated the bone-regenerating potential of NOVOSIS putty (NP), a novel composite combining hydroxyapatite, beta-tricalcium phosphate microsphere/poloxamer 407-based hydrogel, and recombinant human (rh) BMP-2. In vitro assessment of release kinetics by enzyme-linked immunosorbent assay demonstrated sustained release of rhBMP-2 from NP and burst release from collagen sponge (CS), and in vivo assessment of release kinetics by longitudinal tracking of fluorescently labeled rhBMP-2 showed a longer biological half-life of rhBMP-2 with NP than with CS. Furthermore, osteogenic gene expression in MC3T3-E1 cells was significantly higher after co-culture with NP than after co-culture with CS, suggesting that the sustained release of rhBMP-2 from NP effectively contributed to the differentiation of osteoblasts. In a rat spinal fusion model, the volume and quality of newly formed bone was higher in the NP group than in the CS group. Use of NP results in efficient bone regeneration through sustained release of rhBMP-2 and improves the quality of BMP-induced bone.

Methods of Topical Administration of Drugs and Biological Active Substances for Dental Implants-A Narrative Review

Dental implants are, nowadays, established surgical devices for the restoration of lost teeth. Considered as an alternative for traditional prosthetic appliances, dental implants surpass them in reliability and patient feedback. Local drug delivery around the implants promotes osseointegration and reduces peri-implantitis. However, there are currently no methods of a multiple, precise topical administration of drugs to the implant area. Engineering coatings on the implants, drug application on carriers during implantation, or gingival pockets do not meet all requirements of dental surgeons. Therefore, there is a need to create porous implants and other medical devices that will allow a multiple drug delivery at a controlled dose and release profile without traumatic treatment. Due to the growing demand for the use of biologically active agents to support dental implant treatment at its various stages (implant placement, long-term use of dental superstructures, treatment of the peri-implant conditions) and due to the proven effectiveness of the topical application of pharmacological biologically active agents to the implant area, the authors would like to present a review and show the methods and devices that can be used by clinicians for local drug administration to facilitate dental implant treatment. Our review concludes that there is a need for research in the field of inventions such as new medical devices or implants with gradient solid-porous structures. These devices, in the future, will enable to perform repeatable, controllable, atraumatic, and repeatable injections of active factors that may affect the improvement of osteointegration and the longer survival of implants, as well as the treatment of peri-implantitis.

Role and influence of growth factors on early osseointegration in animal jaw bone: A meta-analysis

Aim:

Growth factors (GFs) are polypeptides, which are intricately involved in the regulation of bone formation, preservation, and regeneration through gene expression. However, the role of these bioactive agents in osseointegration of dental implants has not been substantially proven. The objective of this systematic review (SR) and meta-analysis was to explore the effect of GFs on early osseointegration of dental implants in animal jaws. An attempt to decipher an adjunctive role of GFs in modulating predictable bone growth in peri-implant areas was done.

Materials and Methods:

An electronic and manual search of different databases was performed. Only randomized controlled trials (RCTs) were included and reviewed. The risk of bias (ROB) of the selected studies was assessed using the SR Centre for Laboratory Animal Experimentation (Cochrane) tool. A meta-analysis was also performed to evaluate the different study characteristics quantitatively.

Statistical Analysis used:

The total Weighted mean difference was evaluated using the Rev-Manv5.3 algorithm. Chi-square test and I² test were done to assess the heterogeneity between the studies.

Results:

Seven RCTs were included in the study. These were associated with a high ROB. The total weighted mean difference (WMD) of the percentage of bone–implant contact was 3.25% (95% confidence interval [CI] = 1.49%–6.03%; P = 0.001; I² = 91%) between groups with and without exogenous application of GFs. The total WMD of the percentage of newly formed bone area was 4.48% (95% CI = 2.31%–5.90%; P < 0.00001, I² = 84%). A high level of heterogeneity (P < 0.001 for Chi-square test; I²>50 %) among comparable studies was observed.

Conclusion:

The ancillary application of external GFs exhibited evidence of early osseointegration, resulting in more predictable and faster results. However, a careful discernment of conclusions drawn from this SR is a must before conducting any human trials.

The efficacy of rhBMP-2 loaded hydrogel composite on bone formation around dental implants in mandible bone defects of minipigs

Background

In dental or orthopedic surgery, bone substitutes are inserted with implants to promote osteogenesis and enhance osseointegration. The purpose of this research was to evaluate the efficacy of rhBMP-2 (recombinant human bone morphogenetic protein-2) loaded hydrogel composite for bone formation around dental implant in minipig mandible bone defect models.

Methods

We made bone defects with a diameter of 4 mm in minipig mandibles and inserted implants of the same size, to mimic the cases of inserting the screws in the bone defect or poor-quality bone. The rhBMP-2 (300 μg) loaded hydrogel composite (0.5 cc) inserted in the bone defect with the implant in the rhBMP-2 group. After 4 weeks, the mandibles were harvested to evaluate the new bone mass around implants using plain radiographs, micro-CT, and histology.

Results

The micro-CT analysis result showed that the quantity of new bone generation around the implant in the rhBMP-2 group was greater than that in the other groups. Comparing the ratios of bone to implant area in three groups by histology, the amount of newly formed bone in the rhBMP-2 group was the most.

Conclusion

The rhBMP-2 loaded hydrogel composite promotes osteogenesis around dental implant in minipig mandible bone defect, and enhance osseointegration between the dental implant and host bone.

Gap healing after medial open-wedge high tibial osteotomy using injectable beta-tricalcium phosphate

PURPOSE

The study aim was to evaluate gap healing after medial open-wedge high tibial osteotomy (MOWHTO) using novel injectable beta-tricalcium phosphate (β-TCP) as gap filler. We also aimed to evaluate radiographic and clinical outcome of MOWHTO using injectable β-TCP.

METHODS

Consecutive 28 patients underwent MOWHTO using anatomical locking plate fixation, and β-TCP was injected as gap filler. Serial radiographs and computed tomography were taken at postoperative 3 and 12 months, and gap healing was assessed. Lower extremity alignment was measured on radiographs, and clinical outcome was evaluated by determining International Knee Documentation Committee, Western Ontario and McMaster Universities Arthritis Index, and visual analogue scales for pain scores.

RESULTS

Progress of bone union was found on plain radiographs, and the mean ratio (β-TCP/host bone) of computed tomography attenuation values significantly changed from postoperative 3 months to 12 months, which indicates maturation of β-TCP. The average mechanical femoro-tibial angle changed from 4.1° varus (preoperative) to 4.8° valgus (3 months) and maintained until 12 months (4.3° valgus). All clinical outcome scores were significantly improved and no significant complication occurred.

CONCLUSION

Using injectable β-TCP as gap filler for MOWHTO resulted in satisfactory gap healing without complication. Radiographic and clinical results were satisfactory. The injectable β-TCP can be a safe and effective option for gap filling after MOWHTO.

Efficacy of Octacalcium Phosphate Collagen Composite for Titanium Dental Implants in Dogs

Background: Previous studies showed that octacalcium (OCP) collagen composite (OCP/Col) can be used to repair human jaw bone defects without any associated abnormalities. The present study investigated whether OCP/Col could be applied to dental implant treatment using a dog tooth extraction socket model. Methods: The premolars of dogs were extracted; each extraction socket was extended, and titanium dental implants were placed in each socket. OCP/Col was inserted in the space around a titanium dental implant. Autologous bone was used to fill the other sockets, while the untreated socket (i.e., no bone substitute material) served as a control. Three months after the operation, these specimens were analyzed for the osseointegration of each bone substitute material with the surface of the titanium dental implant. Results: In histomorphometric analyses, the peri-implant bone areas (BA%) and bone-implant contact (BIC%) were measured. There was no difference in BA% or BIC% between OCP/Col and autologous bone. Conclusion: These results suggested that OCP/Col could be used for implant treatment as a bone substitute.

Betulinic acid synergically enhances BMP2-induced bone formation via stimulating Smad 1/5/8 and p38 pathways

BACKGROUND

Healing of bone defects is a dynamic and orchestrated process that relies on multiple growth factors and cell types. Bone morphogenetic protein 2 (BMP2) is a key growth factor for bone healing, which stimulates mesenchymal stem cells to differentiate into osteoblasts. Betulinic acid (BetA) is a natural pentacyclic triterpenoid from plants. This study aimed to examine combinatory effects of BetA and BMP2 on ectopic bone generation in mice.

RESULTS

In MC3T3-E1 preosteoblast culture, 10-15 μM of BetA increased the alkaline phosphatase (ALP) activity and expression levels of osteogenic marker genes without the decreased cell viability. In addition, BetA synergistically enhanced BMP2-induced gene expressions and mineralization with the enhancement of phosphorylation of Smad1/5/8 and p38. In an in vivo ectopic bone formation model, combination of BetA (50 μg) and BMP2 (3 μg) resulted in increases in the amount of new bone generation, compared with treatment with BMP2 alone. Histological studies showed that bone generation with cortical and trabecular structures was resulted from the combination of BetA and BMP2.

CONCLUSION

BetA can enhance in vivo osteogenic potentials of BMP2, possibly via stimulating Smad 1/5/8 and p38 pathways, and combination of both agents can be considered as a therapeutic strategy for bone diseases.

Lithium-doped β-tricalcium phosphate: Effects on physical, mechanical and in vitro osteoblast cell-material interactions

In this work, we have investigated the effects of lithium (Li) dopant at different concentrations and sintering temperatures on the physical and mechanical properties of β-tricalcium phosphate (β-TCP). Our results showed that Li addition at concentrations of 0.65 and 1.0 wt % inhibits the β-TCP to α-TCP phase transformation. 0.15 wt % Li addition resulted in grain growth and extensive liquid phase was formed at higher concentrations. At 1150°C, compressive strength of β-TCP increased from 138.7 ± 19.9 MPa to 170.9 ± 29.8 MPa with the addition of 0.15 wt % Li. Addition of higher amounts of Li decreased the compressive strength and the lowest compressive strength of 99.8 ± 13.7 MPa was found in samples containing 1.0 wt % Li. After 3 days of culture, osteoblast cells grew to confluence on samples containing 0.65 and 1.0 wt % Li. Cells grew to confluence on all doped samples after 11 days of culture and optical cell density was 4-5 folds higher on 0.15 and 1.0 wt % Li-doped TCP samples. Our results show that both Li content and sintering temperature have significant influence toward physicochemical and mechanical properties of β-TCP which affects the osteoblast cell-materials interaction in Li-doped TCP scaffolds. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 391-399, 2017.

Fabrication and characterization of carboxymethyl chitosan/poly(vinyl alcohol) hydrogels containing alginate microspheres for protein delivery

In this research, a novel drug delivery system consisting of alginate microspheres and carboxymethyl chitosan/poly(vinyl alcohol) hydrogel was developed for prolonged and sustained controlled drug release. The alginate microspheres and various volume ratios of carboxymethyl chitosan were incorporated physically into poly(vinyl alcohol) to form the composite system. Scanning electron microscope, rheometer, differential scanning calorimetry, and thermogravimetric analysis were used to investigate the morphological, rheological, and thermal properties. The adsorptivity and hydrogel content were evaluated by swelling ratio and gel fraction, respectively. Incorporation of alginate microspheres improved the swelling ratio and thermal stability of carboxymethyl chitosan/poly(vinyl alcohol) hydrogel. Carboxymethyl chitosan decreased gel fraction and elasticity while increased swelling and porosity of hydrogel. In vitro, the release profiles of bovine serum albumin from the composite gels were sustained for 2 weeks in phosphate buffered saline.