Bone morphogenetic proteins for periodontal and alveolar indications; biological observations - clinical implications

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

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

Clinical application of platelet-rich fibrin to enhance dental implant stability: A systematic review and meta-analysis

Objective

To investigate the effect of platelet-rich fibrin application on implant stability.

Study design

Five databases, namely, PubMed, Embase, Web of Science, Wiley, and China National Knowledge Infrastructure, were searched for reports published up to November 20, 2022. Randomized controlled trials (RCT), including parallel RCTs and split-mouth RCTs, with at least 10 patients/sites were considered for inclusion.

Results

After screening based on the inclusion criteria, ten RCTs were included. Low heterogeneity was observed in study characteristics, outcome variables, and estimation scales (I2 = 27.2%, P = 0.19). The qualitative and meta-analysis results showed that PRF increased the effect of implant stabilizers after implant surgery.

Conclusions

The results of the present systematic review and meta-analysis suggest that PRF can increase implant stability after implant surgery. PRF may also have a role in accelerating bone healing and tends to promote new bone formation at the implant site.

The Influence of rhBMP-7 Associated with Nanometric Hydroxyapatite Coatings Titanium Implant on the Osseointegration: A Pre-Clinical Study

Background: Bioceramic nanometer coatings have been regarded as potential substitutes for plasma-sprayed hydroxyapatite coatings, and the association with bone morphogenetic protein (BMP) is an attempt to achieve faster osseointegration to hasten oral rehabilitation. Objective: This study aimed to investigate the effect of recombinant human bone morphogenetic protein-7 (rhBMP-7) on the osseointegration of titanium implants coated with a thin film surface of hydroxyapatite (HA). Methods: Two implants (n = 24) were placed in each white New Zealand rabbits’ femur (n = 6). Implants were placed in the right femur after standard instrumentation (A and B) and in the left femur after an over-instrumentation (C and D), preventing bone-implant contact. The distal implants were installed associated with rhBMP-7 (groups B [regular instrumentation] and D [over-instrumentation]) and, also, in the absence of without BMP (control groups A [regular instrumentation] and C [over-instrumentation]). After 4 weeks, the animals were euthanized. The bone blocks containing the implants were embedded in methyl methacrylate and sectioned parallel to the long axis of the implant, which were analyzed by image segmentation. The data were analyzed using a nonparametric statistical method. Results: We observed that Group A had a mean bone formation of 35.6% compared to Group B, which had 48.6% (p > 0.05). Moreover, this group showed 28.3% of connective tissue compared to Group A, with 39.3%. In the over-instrumented groups, rhBMP-7 (Group D) showed an enhanced and significant increase in bone formation when compared with the group without rhBMP-7 (Group C). Conclusion: We concluded that the association of rhBMP-7 to thin nanostructure HA-coated implants promoted greater new bone area than the same implants in the absence of rhBMP-7, mainly in cases of over-instrumented implant sites.

Preclinical Evaluation of BMP-9-Treated Human Bone-like Substitutes for Alveolar Ridge Preservation following Tooth Extraction

The success of dental implant treatment after tooth extraction is generally maximized by preserving the alveolar ridge using cell-free biomaterials. However, these treatments can be associated with inflammatory reactions, leading to additional bone volume loss hampering dental implant positioning. Our group developed a self-assembled bone-like substitute constituted of osteogenically induced human adipose-derived stromal/stem cells (hASCs). We hypothesized that a bone morphogenetic protein (BMP) supplementation could improve the in vitro osteogenic potential of the bone-like substitute, which would subsequently translate into enhanced alveolar bone healing after tooth extraction. ASCs displayed a better osteogenic response to BMP-9 than to BMP-2 in monolayer cell culture, as shown by higher transcript levels of the osteogenic markers RUNX2, osterix (OSX/SP7), and alkaline phosphatase after three and six days of treatment. Interestingly, BMP-9 treatment significantly increased OSX transcripts and alkaline phosphatase activity, as well as pro-angiogenic angiopoietin-1 gene expression, in engineered bone-like substitutes after 21 days of culture. Alveolar bone healing was investigated after molar extraction in nude rats. Microcomputed tomography and histological evaluations revealed similar, or even superior, global alveolar bone preservation when defects were filled with BMP-9-treated bone-like substitutes for ten weeks compared to a clinical-grade biomaterial, with adequate gingival re-epithelialization in the absence of resorption.

Proposal for a New Bioactive Kinetic Screw in an Implant, Using a Numerical Model

A new biomechanism, Bioactive Kinetic Screw (BKS) for screws and bone implants created by the first author, is presented using a bone dental implant screw, in which the bone particles, blood, cells, and protein molecules removed during bone drilling are used as a homogeneous autogenous transplant in the same implant site, aiming to obtain primary and secondary bone stability, simplifying the surgical procedure, and improving the healing process. The new BKS is based on complex geometry. In this work, we describe the growth factor (GF) delivery properties and the in situ optimization of the use of the GF in the fixation of bone screws through a dental implant. To describe the drilling process, an explicit dynamic numerical model was created, where the results show a significant impact of the drilling process on the bone material. The simulation demonstrates that the space occupied by the screw causes stress and deformation in the bone during the perforation and removal of the particulate bone, resulting in the accumulation of material removed within the implant screw, filling the limit hole of the drill grooves present on the new BKS.

Synthesis of Human Bone Morphogenetic Protein-2 (hBMP-2) in E. coli Periplasmic Space: Its Characterization and Preclinical Testing

Human BMP-2, a homodimeric protein that belongs to the TGF- β family, is a recognized osteoinductor due to its capacity of inducing bone regeneration and ectopic bone formation. The administration of its recombinant form is an alternative to autologous bone grafting. A variety of E. coli-derived hBMP-2 has been synthesized through refolding of cytoplasmic inclusion bodies. The present work reports the synthesis, purification, and characterization of periplasmic hBMP-2, obtained directly in its correctly folded and authentic form, i.e., without the initial methionine typical of the cytoplasmic product that can induce undesired immunoreactivity. A bacterial expression vector was constructed including the DsbA signal peptide and the cDNA of hBMP-2. The periplasmic fluid was extracted by osmotic shock and analyzed via SDS-PAGE, Western blotting, and reversed-phase high-performance liquid chromatography (RP-HPLC). The purification was carried out by heparin affinity chromatography, followed by high-performance size-exclusion chromatography (HPSEC). HPSEC was used for qualitative and quantitative analysis of the final product, which showed >95% purity. The classical in vitro bioassay based on the induction of alkaline phosphatase activity in myoblastic murine C2C12 cells and the in vivo bioassay consisting of treating calvarial critical-size defects in rats confirmed its bioactivity, which matched the analogous literature data for hBMP-2.

Effects of low-dose rhBMP-2 on peri-implant ridge augmentation in a canine model

AIMS

The aim of this study was to investigate the potential of low-dose rhBMP-2 combined with Hydroxyapatite (HAp)/β-tricalcium phosphate (TCP)/ Collagen (Col) composite in repairing the peri-implant critical size defect and to determine the optimal rhBMP-2 concentration.

MATERIALS AND METHODS

Fifty saddle-type alveolar defects (10 mm mesiodistally and 4 mm apicocoronally) were surgically prepared on edentulous ridges in ten beagle dogs. Following implant placement, the defects with vertically exposed implant fixtures either received (a) no graft, (b) HAp/TCP/Col composite, (c) HAp/TCP/Col +0.02 mg/ml rhBMP-2, (d) HAp/TCP/Col +0.08 mg/ml rhBMP-2 or (e) HAp/TCP/Col +0.2 mg/ml rhBMP-2. After healing for 4 or 8 weeks, bone regeneration and mineralization were assessed through radiography, micro-CT, fluorescence labelling and histologic analyses. Implant stability was measured through resonance frequency analysis.

RESULTS

It was evident HAp/TCP/Col with 0.2 mg/ml rhBMP-2 manifested strong osteogenic potential in this large animal model, as significantly more and faster new bone formation with better implant stability was identified compared to the HAp/TCP/Col-alone control group (adjusted p < .05).

CONCLUSIONS

Our results highlight the constructs of HAp/TCP/Col +0.2 mg/ml rhBMP-2 without barrier membranes as a promising tool for peri-implant ridge augmentation.

Human bone morphogenetic protein-2 (hBMP-2) characterization by physical-chemical, immunological and biological assays

Commercially available preparations of methionyl-human BMP-2 and CHO-derived hBMP-2, which belongs to the transforming growth factor β (TGF-β) superfamily, were used for a complete characterization. This protein is an extremely efficient osteoinductor that plays an important role during bone regeneration and embryonic development. Characterization was carried out via SDS-PAGE and Western blotting, followed by reversed-phase HPLC, size-exclusion HPLC and MALDI-TOF-MS. The classical in vitro bioassay, based on the induction of alkaline phosphatase activity in C2C12 cells, confirmed that hBMP-2 biological activity is mostly related to the dimeric form, being ~ 4-fold higher for the CHO-derived glycosylated form when compared with the E. coli counterpart. The E. coli-derived met-hBMP-2 has shown, by MALDI-TOF-MS, a large presence of the bioactive dimer. A more complex molecular mass (MM) distribution was found for the CHO-derived product, whose exact MM has never been reported because of its variable glycosylation. A method based on RP-HPLC was set up, allowing a quantitative and qualitative hBMP-2 determination even directly on ongoing culture media. Considering that hBMP-2 is highly unstable, presenting moreover an extremely high aggregate value, we believe that these data pave the way to a necessary characterization of this important factor when synthesized by DNA recombinant techniques in different types of hosts.

Promoting Induced Pluripotent Stem Cell-driven Biomineralization and Periodontal Regeneration in Rats with Maxillary-Molar Defects using Injectable BMP-6 Hydrogel

Periodontal disease may cause considerable destruction of alveolar bone, periodontal ligaments (PDLs) and cementum and even lead to progressive oral dysfunction. Periodontal tissue regeneration is the ultimate goal of periodontal disease treatment to reconstruct both structures and functions. However, the regenerative efficiency is low, possibly due to the lack of a proper periodontal microenvironment. In this study, we applied an injectable and thermosensitive chitosan/gelatin/glycerol phosphate hydrogel to provide a 3D environment for transplanted stem cells and to enhance stem cell delivery and engraftment. The iPSCs-BMP-6-hydrogel complex promoted osteogenesis and the differentiation of new connective tissue and PDL formation. In animal models of maxillary-molar defects, the iPSCs-BMP-6-hydrogel-treated group showed significant mineralization with increased bone volume, trabecular number and trabecular thickness. Synergistic effects of iPSCs and BMP-6 increased both bone and cementum formation. IPSCs-BMP-6-hydrogel-treated animals showed new bone synthesis (increased ALP- and TRAP-positive cells), new PDL regeneration (shown through Masson’s trichrome staining and a qualification assay), and reduced levels of inflammatory cytokines. These findings suggest that hydrogel-encapsulated iPSCs combined with BMP-6 provide a new strategy to enhance periodontal regeneration. This combination not only promoted stem cell-derived graft engraftment but also minimized the progress of inflammation, which resulted in highly possible periodontal regeneration.

Stepwise verification of bone regeneration using recombinant human bone morphogenetic protein-2 in rat fibula model

Objectives

The purpose of this study was to introduce our three experiments on bone morphogenetic protein (BMP) and its carriers performed using the critical sized segmental defect (CSD) model in rat fibula and to investigate development of animal models and carriers for more effective bone regeneration.

Materials and Methods

For the experiments, 14, 16, and 24 rats with CSDs on both fibulae were used in Experiments 1, 2, and 3, respectively. BMP-2 with absorbable collagen sponge (ACS) (Experiments 1 and 2), autoclaved autogenous bone (AAB) and fibrin glue (FG) (Experiment 3), and xenogenic bone (Experiment 2) were used in the experimental groups. Radiographic and histomorphological evaluations were performed during the follow-up period of each experiment.

Results

Significant new bone formation was commonly observed in all experimental groups using BMP-2 compared to control and xenograft (porcine bone) groups. Although there was some difference based on BMP carrier, regenerated bone volume was typically reduced by remodeling after initially forming excessive bone.

Conclusion

BMP-2 demonstrates excellent ability for bone regeneration because of its osteoinductivity, but efficacy can be significantly different depending on its delivery system. ACS and FG showed relatively good bone regeneration capacity, satisfying the essential conditions of localization and release-control when used as BMP carriers. AAB could not provide release-control as a BMP carrier, but its space-maintenance role was remarkable. Carriers and scaffolds that can provide sufficient support to the BMP/carrier complex are necessary for large bone defects, and AAB is thought to be able to act as an effective scaffold. The CSD model of rat fibula is simple and useful for initial estimate of bone regeneration by agents including BMPs.

Vertical bone regeneration using rhBMP-2 and VEGF

Background

Sufficient vertical and lateral bone supply and a competent osteogenic healing process are prerequisities for the successful osseointegration of dental implants in the alveolar bone. Several techniques including autologous bone grafts and guided bone regeneration are applied to improve quality and quantity of bone at the implantation site. Depending on the amount of lacking bone one- or two-stage procedures are required. Vertical bone augmentation has proven to be a challenge particularly in terms of bone volume stability. This study focuses on the three dimensional vertical bone generation in a one stage procedure in vivo. Therefore, a collagenous disc-shaped scaffold (ICBM = Insoluble Collagenous Bone Matrix) containing rhBMP-2 (Bone Morphogenetic Protein-2) and/or VEGF (Vascular Endothelial Growth Factor) was applied around the coronal part of a dental implant during insertion. RhBMP-2 and VEGF released directly at the implantation site were assumed to induce the generation of new vertical bone around the implant.

Methods

One hundred eight titanium implants were inserted into the mandible and the tibia of 12 mini pigs. Four experimental groups were formed: Control group, ICBM, ICBM + BMP-2, and ICBM + BMP-2 + VEGF.

After 1, 4 and 12 weeks the animals were sacrificed and bone generation was investigated histologically and histomorphometrically.

Results

After 12 weeks the combination of ICBM + rhBMP2 + VEGF showed significantly more bone volume density (BVD%), a higher vertical bone gain (VBG) and more vertical bone gain around the implant (PVBG) in comparison to the control group.

Conclusion

By using collagenous disc-shaped matrices in combination with rhBMP-2 and VEGF vertical bone can be generated in a one stage procedure without donor site morbidity. The results of the presenting study suggest that the combination of rhBMP-2 and VEGF applied locally by using a collagenous carrier improves vertical bone generation in vivo. Further research is needed to establish whether this technique is applicable in clinical routines.

Use of rhBMP-2/β-TCP for Interpositional Vertical Grafting Augmentation: 5.5-Year Follow-up Clinically and Histologically

PURPOSE

This case report documented long-term results using rh-BMP-2/β-tricalcium phosphate (TCP) for vertical grafting augmentation.

MATERIALS AND METHODS

A 58-year-old patient with extreme atrophy of the left posterior mandible was treated with rh-BMP-2/β-TCP for vertical bone augmentation. At the time of implant placement, bone biopsy was performed for histological evaluation.

RESULTS

Seven months after surgery, CT scan demonstrated approximately 8 mm of bone gain height. The histological results revealed a newly formed vital bone tissue, predominantly lamellar with variable density. Remaining bone ceramic surrounded by newly formed bone tissue or connective tissue was observed. The bone levels remained unchanged during the entire period treatment (5.5 years).

CONCLUSION

This technique has demonstrated a potential for reconstruction of atrophic sites when vertical bone gain is desirable. Moreover, the bone gain has shown long-term maintenance without resorption. Future long-term prospective clinical trials are needed to confirm these findings.

Preparation of resorbable carbonate-substituted hollow hydroxyapatite microspheres and their evaluation in osseous defects in vivo

Hollow hydroxyapatite (HA) microspheres, with a high-surface-area mesoporous shell, can provide a unique bioactive and osteoconductive carrier for proteins to stimulate bone regeneration. However, synthetic HA has a slow resorption rate and a limited ability to remodel into bone. In the present study, hollow HA microspheres with controllable amounts of carbonate substitution (0-12 wt.%) were created using a novel glass conversion route and evaluated in vitro and in vivo. Hollow HA microspheres with ~12 wt.% of carbonate (designated CHA12) showed a higher surface area (236 m(2) g(-1)) than conventional hollow HA microspheres (179 m(2)g(-1)) and a faster degradation rate in a potassium acetate buffer solution. When implanted for 12 weeks in rat calvarial defects, the CHA12 and HA microspheres showed a limited capacity to regenerate bone but the CHA12 microspheres resorbed faster than the HA microspheres. Loading the microspheres with bone morphogenetic protein-2 (BMP2) (1 μg per defect) stimulated bone regeneration and accelerated resorption of the CHA12 microspheres. At 12 weeks, the amount of new bone in the defects implanted with the CHA12 microspheres (73±8%) was significantly higher than the HA microspheres (59±2%) while the amount of residual CHA12 microspheres (7±2% of the total defect area) was significantly lower than the HA microspheres (21±3%). The combination of these carbonate-substituted HA microspheres with clinically safe doses of BMP2 could provide promising implants for healing non-loaded bone defects.

Interventions for treating bisphosphonate-related osteonecrosis of the jaw (BRONJ)

BACKGROUND

Bisphosphonate drugs can be used to prevent and treat osteoporosis and to reduce symptoms and complications of metastatic bone disease; however, they are associated with a rare but serious adverse event: osteonecrosis of the maxillary and mandibular bones. This condition is called bisphosphonate-related osteonecrosis of the jaw or BRONJ. BRONJ is diagnosed when people who are taking, or have previously taken, bisphosphonates have exposed bone in the jaw area for more than eight weeks in the absence of radiation treatment. There is currently no "gold standard" of treatment for BRONJ. The three broad categories of intervention are conservative approaches (e.g. mouth rinse, antibiotics), surgical interventions and adjuvant non-surgical strategies (e.g. hyperbaric oxygen therapy, platelet-rich plasma), which can be used in combination.

OBJECTIVES

To determine the efficacy and safety of any intervention aimed at treating BRONJ.

SEARCH METHODS

We searched the following databases to 15 December 2015: the Cochrane Oral Health Group Trials Register, the Cochrane Breast Cancer Group Trials Register (20 September 2011), the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE via Ovid, EMBASE via Ovid, CancerLit via PubMed, CINAHL via EBSCO and AMED via Ovid. We scanned the references cited in retrieved articles and contacted experts in the field, the first authors of included papers, study sponsors, other bisphosphonates investigators and pharmaceutical companies. We searched for ongoing trials through contact with trialists and by searching the US National Institutes of Health Trials Register (clinicaltrials.gov) and the World Health Organization Clinical Trials Registry Platform. We also conducted a grey literature search to September 2015.

SELECTION CRITERIA

Randomised controlled trials (RCTs) comparing the effects of any treatment for BRONJ with another treatment or placebo.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened the search results, assessed the risk of bias in the included trials and extracted data. When in dispute, we consulted a third review author.

MAIN RESULTS

One small trial at high risk of bias met the inclusion criteria. The trial randomised 49 participants, most of whom had cancer. It compared standard care (defined as surgery, antibiotics and oral rinses at the discretion of the oral-maxillofacial surgeon) to standard care plus hyperbaric oxygen therapy (2 atmospheres twice a day for 40 treatments). The trial measured the percentage of participants who improved or healed at three, six, 12 and 18 months and last contact. It also measured mean weekly pain scores.At three months, the study found that the participants in intervention group were more likely to have an improvement in their osteonecrosis than the standard care group participants (risk ratio (RR) 1.94, 95% confidence interval (CI) 1.01 to 3.74). There was no clear difference between the groups for the outcome 'healed' at three months (RR 3.60, 95% CI 0.87 to 14.82). There was no clear difference between the groups for improvement or healing when they were evaluated at six, 12 and 18 months and last contact.The study did not give any information on adverse events.Although the findings suggest adjunctive hyperbaric oxygen improved BRONJ, the quality of the evidence is very low since the only study was underpowered and was at high risk of bias due to lack of blinding, cross-over of participants between groups and very high attrition (50% at 12 months and 80% at 18 months in this study, which was designed for an intended follow-up of 24 months).

AUTHORS' CONCLUSIONS

There is a lack of evidence from randomised controlled trials to guide treatment of bisphosphonate-related osteonecrosis of the jaw (BRONJ). One small trial at high risk of bias evaluated hyperbaric oxygen therapy (HBO) as an adjunct to "standard" care and could not confirm or refute the effectiveness of HBO. There are two ongoing trials of teriparatide treatment for BRONJ. We found no randomised controlled trials of any other BRONJ treatments. High quality randomised controlled trials are needed. We provide recommendations for their focus and design.

Effect of targeted delivery of bone morphogenetic protein-2 on bone formation in type 1 diabetes

PURPOSE

Bone formation and healing are diminished in experimental type 1 diabetes. The present study investigated whether controlled local release of recombinant human bone morphogenetic protein 2 (rhBMP-2) stimulates bone defect healing in diabetes as a consequence of its anabolic effects on bone.

MATERIALS AND METHODS

Bilateral experimental circular bone defects were created in the temporal bones of 64 BALB/cByJ mice. Defects were treated with acellular collagen sponge plus 0.4 or 1.8 μg of rhBMP-2 per defect, and untreated defects served as controls. The healing of the defects over a 14-day period in diabetic and nondiabetic mice was analyzed histomorphometrically.

RESULTS

Diabetes inhibited bone formation in both untreated and BMP-treated bone defects. Controlled local release of rhBMP-2 significantly stimulated bone formation in diabetic animals, bringing it nearly to normal levels, and enhanced bone regeneration in normal animals.

CONCLUSION

Recombinant human BMP-2 may be beneficial in treating deficient intramembranous bone formation in diabetes.

Periimplant bone regeneration in hydroxyapatite block grafts with mesenchymal stem cells and bone morphogenetic protein-2

Hydroxyapatite (HA) blocks as an alternative material for autogenous onlay bone grafts are regarded as an insufficient substitute for osseointegration of dental implant. In this study, we evaluated the effects of dog mesenchymal stromal cells (dMSCs) with or without bone morphogenetic protein-2 (BMP) on new peri-implant bone formation after HA block graft. In four mandibular bone defects (8×8×6 mm each) in five beagle dogs, dental implants were placed with HA block loaded with autogenous dMSCs with or without BMP-2. Animals were sacrificed at eight weeks, and bone healing was evaluated among four groups consisting of 1) HA alone as a control, 2) HA+dMSCs, 3) HA+BMP-2, and 4) HA+dMSCs+BMP-2. According to histomorphometric evaluation, the MSC+BMP-2 group and the BMP-2 group showed significantly higher bone-implant-contact (BIC) length than the MSC group, while there was no significant difference in new bone formation among the groups. According to micro-CT analysis, bone volume and bone mineral density were significantly higher in the MSC+BMP-2 group compared with the control group (p<0.01 and p<0.05, respectively). BIC was significantly higher in the MSC+BMP-2 group than both the control and MSC groups (p<0.01 and p<0.05, respectively). In conclusion, our results showed that bone regeneration at peri-implant bone defects grafted with HA blocks was significantly increased by dual delivery of MSCs and BMP-2. Conversely, HA blocks with MSC or BMP-2 alone did not allow for efficient peri-implant bone regeneration.

Characterization of a shorter recombinant polypeptide chain of bone morphogenetic protein 2 on osteoblast behaviour

BACKGROUND

Recombinant bone morphogenetic protein two (rhBMP2) has been utilised for a variety of clinical applications in orthopaedic surgery and dental procedures. Despite its widespread use, concerns have been raised regarding its short half-life and transient bioactivity in vivo. Recent investigation aimed at developing rhBMP2 synthesized from a shorter polypeptide chain (108 amino acids) has been undertaken.

METHODS

The osteopromotive properties of BMP2 were investigated on cell behaviour. Five concentrations of rhBMP2_108 including 10, 50, 100, 200 and 500 ng/ml were compared to a commercially available rhBMP2 (100 ng/ml). Each of the working concentrations of rhBMP2_108 were investigated on MC3T3-E1 osteoblasts for their ability to induce osteoblast recruitment, proliferation and differentiation as assessed by alkaline phosphatase (ALP) staining, alizarin red staining, and real-time PCR for genes encoding ALP, osteocalcin (OCN), collagen-1 (COL-1) and Runx2.

RESULTS

The results demonstrate that all concentrations of rhBMP2_108 significantly improved cell recruitment and proliferation of osteoblasts at 5 days post seeding. Furthermore, rhBMP2_108 had the most pronounced effects on osteoblast differentiation. It was found that rhBMP2_108 had over a four fold significant increase in ALP activity at seven and 14 days post-seeding and the concentrations ranging from 50 to 200 ng/ml demonstrated the most pronounced effects. Analysis of real-time PCR for genes encoding ALP, OCN, COL-1 and Runx2 further confirmed dose-dependant increases at 14 days post-seeding. Furthermore, alizarin red staining demonstrated a concentration dependant increase in staining at 14 days.

CONCLUSION

The results from the present study demonstrate that this shorter polypeptide chain of rhBMP2_108 is equally as bioactive as commercially available rhBMP2 for the recruitment of progenitor cells by facilitating their differentiation towards the osteoblast lineage. Future in vivo study are necessary to investigate its bioactivity.

Dental Implants

Dental implants restore function to near normal in partially or completely edentulous patients. A root-form implant is the most frequently used type of dental implant today. The basis for dental implants is osseointegration, in which osteoblasts grow and directly integrate with the surface of titanium posts surgically embedded into the jaw. Radiologic assessment is critical in the preoperative evaluation of the dental implant patient, as the exact height, width, and contour of the alveolar ridge must be determined. Moreover, the precise locations of the maxillary sinuses and mandibular canals, as well as their relationships to the site of implant surgery must be ascertained. As such, radiologists must be familiar with implant design and surgical placement, as well as augmentation procedures utilized in those patients with insufficient bone in the maxilla and mandible to support dental implants.

Bmp2 and Bmp4 accelerate alveolar bone development

Alveolar bone remodeling is a continuous process that takes place during development and in response to various physiological and pathological stimuli. However, detailed knowledge regarding the underlying mechanisms involved in alveolar bone development is still lacking. This study aims at improving our understanding of alveolar bone formation and the role of bone morphogenetic proteins (Bmps) in this process. Mice at embryonic (E) day 13.5 to postnatal (PN) day 15.5 were selected to observe the process of alveolar bone development. Alveolar bone development was found to be morphologically observable at E14.5. Molar teeth isolated from mice at PN7.5 were pretreated with Bmp2, Bmp4, Noggin, or BSA, and grafted subcutaneously into mice. The subcutaneously implanted tooth germs formed alveolar bone indicating the role of the dental follicle in alveolar bone development. Alveolar bone formation was increased after pretreatment with Bmp2 and Bmp4, but not with Noggin. Gene expression levels in dental follicle cells from murine molars were also determined by real-time RT-PCR. The expression levels of Runx2, Bsp, and Ocn were significantly higher in dental follicle cells cultured with Bmp2 or Bmp4, and significantly lower in those cultured with Noggin when compared with that of the BSA controls. Our results suggest that the dental follicle participates in alveolar bone formation and Bmp2/4 appears to accelerate alveolar bone development.

A high concentration of recombinant human bone morphogenetic protein-2 induces low-efficacy bone regeneration in sinus augmentation: a histomorphometric analysis in rabbits

OBJECTIVES

The aim of the study was to elucidate the efficacy of bone regeneration at the early stage of healing in rabbit sinuses grafted with a biphasic calcium phosphate (BCP) carrier soaked in a high concentration of recombinant human bone morphogenetic protein-2 (rhBMP-2).

MATERIALS AND METHODS

Both maxillary sinuses of eight male rabbits were used. The sinus on one side (assigned randomly) was grafted with BCP loaded with rhBMP-2 (1.5 mg/ml; test group) using a soaking method, while the other was grafted with saline-soaked BCP (control group). After a 2-week healing period, the sinuses were analyzed by micro-computed tomography and histomorphometry.

RESULTS

The total augmented area and soft tissue space were significantly larger in the test group than in the control group, whereas the opposite was true for the area of residual material and newly formed bone. Most of the new bone in the test group was localized to the Schneiderian membrane (SM), while very little bone formation was observed in the window and center regions of the sinus. New bone was distributed evenly in the control group sinuses.

CONCLUSION

Within the limitations of this study, it appeared that application of a high concentration of rhBMP-2 soaked onto a BCP carrier inhibited bone regeneration from the pristine bone and increased soft tissue swelling and inflammatory response at the early healing stage of sinus augmentation, although osteoinductive potential was found along the SM.

Fibrin Hydrogel Based Bone Substitute Tethered with BMP-2 and BMP-2/7 Heterodimers

Current clinically used delivery methods for bone morphogenetic proteins (BMPs) are collagen based and require large concentrations that can lead to dangerous side effects. Fibrin hydrogels can serve as osteoinductive bone substitute materials in non-load bearing bone defects in combination with BMPs. Two strategies to even further optimize such a fibrin based system include employing more potent BMP heterodimers and engineering growth factors that can be covalently tethered to and slowly released from a fibrin matrix. Here we present an engineered BMP-2/BMP-7 heterodimer where an N-terminal transglutaminase substrate domain in the BMP-2 portion provides covalent attachment to fibrin together with a central plasmin substrate domain, a cleavage site for local release of the attached BMP-2/BMP-7 heterodimer under the influence of cell-activated plasmin. In vitro and in vivo results revealed that the engineered BMP-2/BMP-7 heterodimer induces significantly more alkaline phosphatase activity in pluripotent cells and bone formation in a rat calvarial model than the engineered BMP-2 homodimer. Therefore, the engineered BMP-2/BMP-7 heterodimer could be used to reduce the amount of BMP needed for clinical effect.

Improved osseointegration of dental titanium implants by TiO2 nanotube arrays with recombinant human bone morphogenetic protein-2: a pilot in vivo study

TiO2 nanotube arrays on the surface of dental implants were fabricated by two-step anodic oxidation. Their effects on bone-implant contact were researched by a pilot in vivo study. The implants were classified into four groups. An implant group with TiO2 nanotube arrays and recombinant human bone morphogenetic protein-2 (rhBMP-2) was compared with various surface implants, including machined surface, sandblasted large-grit and acid-etched surface, and TiO2 nanotube array surface groups. The diameter of the TiO2 nanotube window and TiO2 nanotube were ~70 nm and ~110 nm, respectively. The rhBMP-2 was loaded into TiO2 nanotube arrays and elution was detected by an interferometric biosensing method. A change in optical thickness of ~75 nm was measured by flow cell testing for 9 days, indicating elution of rhBMP-2 from the TiO2 nanotube arrays. For the in vivo study, the four groups of implants were placed into the proximal tibia of New Zealand White rabbits. In the implant group with TiO2 nanotube arrays and rhBMP-2, the bone-to-implant contact ratio was 29.5% and the bone volume ratio was 77.3%. Bone remodeling was observed not only in the periosteum but also in the interface between the bone and implant threads. These values were higher than in the machined surface, sandblasted large-grit and acid-etched surface, and TiO2 nanotube array surface groups. Our results suggest that TiO2 nanotube arrays could potentially be used as a reservoir for rhBMP-2 to reinforce osseointegration on the surface of dental implants.

Effectiveness of autologous platelet-rich fibrin in the treatment of intra-bony defects: A systematic review and meta-analysis

The aim of the present meta-analysis is to determine the clinical and radiographic outcomes of using platelet-rich fibrin (PRF) for the treatment of periodontal intra-bony defect (IBD) compared with open flap debridement (OFD). MEDLINE/PubMed, EBSCO and Cochrane database were used to identify studies in English language published from January 1, 2005 to January 31, 2013. An additional hand search of the relevant journals and of the bibliographies of the paper identified was also performed. Articles retrieved were screened using specific inclusion criteria by five independent reviewers: Studies investigating the effect of platelet concentrate in surgical procedure for the treatment of periodontal intra osseous defects compared with the control group in which platelet concentrate was not used were included. Five relevant articles were selected for the meta-analysis of which 3 articles were retrieved after electronic search and two articles were included after hand search. The number of patients in studies ranged from 15 to 62 (32-90 sites) with mean age ranging from 29.47 to 39.7. A total of 298 sites were treated using PRF either in combination with graft or as a monotherapy in comparison to traditional OFD procedure. The meta-analysis showed a standard mean difference of 0.95 mm; 95% confidence interval (CI): 0.20-1.71 in clinical attachment level (CAL) and 2.33 mm; 95% CI: 1.43-3.23 in IBD after treatment of IBD with PRF compared with OFD. The meta-analysis showed clinically significant improvements in periodontal parameters such as CAL, IBD, and reduction in probing depth when IBDs were treated with PRF alone when compared to OFD.

Initial Experience With rhBMP-2 Delivered in a Compressive Resistant Matrix for Mandibular Reconstruction in 5 Dogs

OBJECTIVE

To document cumulative initial experience and long-term follow-up of the use of rhBMP-2/CRM for reconstruction of large mandibular defects (≥5 cm) in dogs.

STUDY DESIGN

Retrospective case series.

ANIMALS

Dogs (n = 5).

METHODS

Medical records (October 1999-April 2011) of dogs that had mandibular reconstruction for defects/resections of ≥5 cm using rhBMP-2/CRM were reviewed. Signalment, preoperative assessment/rationale for mandibular reconstruction, surgical methods, postoperative assessment of the reconstruction (evaluation of occlusion), and complications were recorded. A definitive histologic diagnosis was obtained in dogs that had mandibular resection for mass removal. Long-term complications were determined. A minimum time frame of 2-year in-hospital follow-up was required for case inclusion.

RESULTS

Mandibular reconstruction was successfully performed in all dogs' defects where gaps of 5-9 cm were bridged. Surgical reconstruction rapidly restored cosmetic appearance and function. All dogs healed with new bone formation across the gap. New bone formation was present within the defects as early as 2 weeks after surgery based on palpation, and new bone formation bridging the gap was documented radiographically by 16 weeks. Minor complications occurred in all dogs in the early postoperative period, and included early firm swelling and gingival dehiscence in 1 dog; late plate exposure in 3 dogs; and exuberant/cystic bone formation in 2 dogs (related to concentration/formulation of rhBMP-2/CRM). Two dogs had minor long-term complications of late plate exposure and a non-vital canine tooth; the plates and the affected canine tooth were removed. Long-term in-hospital follow-up was 5.3 years (range, 2-12.5 years); further long-term telephone follow-up was 6.3 years (range, 2-12.5 years). All owners were pleased with the outcome and would repeat the surgery again under similar circumstances.

CONCLUSION

The efficacy and success of this mandibular reconstruction technique, using rhBMP-2/CRM with plate fixation, was demonstrated with bridging of large mandibular defects regardless of the underlying cause, and with excellent cosmetic and functional results. Complications were common, but considered minor and easily treated. The complications encountered revealed the importance of tailoring the use of BMPs and fixation methods to this specific anatomic location and indication.

Effects of bone morphogenetic protein-6 on periodontal wound healing/regeneration in supraalveolar periodontal defects in dogs

OBJECTIVE

Application of a synthetic BMP-6 polypeptide in a rat periodontal fenestration defect model enhanced periodontal wound healing/regeneration including new bone and cementum formation. The purpose of this study was to translate the relevance of these initial observations into a discriminating large animal model.

METHODS

Critical-size (4-5 mm) supraalveolar periodontal defects were created at the 2(nd) and 3(rd) mandibular premolar teeth in 11 Beagle dogs. Experimental sites received BMP-6 at 0.25, 1.0 and 2.0 mg/ml soak-loaded onto an absorbable collagen sponge (ACS) carrier or ACS alone (control) each condition repeated in four jaw quadrants. The animals were euthanized at 8 weeks when block biopsies were collected and processed for histologic/histometric analysis.

RESULTS

BMP-6 at 0.25, 1.0 and 2.0 mg/ml soak-loaded onto the ACS yielded significantly enhanced new bone (0.99 ± 0.07 versus 0.23 ± 0.13 mm/BMP-6 at 0.25 mg/ml) and cementum (2.45 ± 0.54 versus 0.73 ± 0.15 mm/BMP-6 at 0.25 mg/ml) formation including a functionally oriented periodontal ligament compared with control (p < 0.05). A significant inverse linear association between BMP-6 dose and new bone (β = -0.21 ± 0.09 mm, p = 0.016) and cementum height (β = -0.34 ± 0.15 mm, p = 0.023) was observed. Minimal root resorption was observed without significant differences between groups. Ankylosis was not observed for any of the experimental groups.

CONCLUSIONS

Surgical application of BMP-6/ACS onto critical-size supraalveolar defects enhanced periodontal wound healing/regeneration, in particular cementogenesis including a functionally oriented periodontal ligament; the low BMP-6 0.25 mg/ml concentration apparently providing the most effective dose.

Sequential platelet-derived growth factor-simvastatin release promotes dentoalveolar regeneration

OBJECTIVES

Timely augmentation of the physiological events of dentoalveolar repair is a prerequisite for the optimization of the outcome of regeneration. This study aimed to develop a treatment strategy to promote dentoalveolar regeneration by the combined delivery of the early mitogenic factor platelet-derived growth factor (PDGF) and the late osteogenic differentiation factor simvastatin.

MATERIALS AND METHODS

By using the coaxial electrohydrodynamic atomization technique, PDGF and simvastatin were encapsulated in a double-walled poly(D,L-lactide) and poly(D,L-lactide-co-glycolide) (PDLLA-PLGA) microspheres in five different modes: microspheres encapsulating bovine serum albumin (BB), PDGF alone (XP), simvastatin alone (SB), PDGF-in-core and simvastatin-in-shell (PS), and simvastatin-in-core and PDGF-in-shell (SP). The microspheres were characterized using scanning electronic microscopy, and the in vitro release profile was evaluated. Microspheres were delivered to fill large osteotomy sites on rat maxillae for 14 and 28 days, and the outcome of regeneration was evaluated by microcomputed tomography and histological assessments.

RESULTS

Uniform 20-μm controlled release microspheres were successfully fabricated. Parallel PDGF-simvastatin release was noted in the PS group, and the fast release of PDGF followed by the slow release of simvastatin was noted in the SP group. The promotion of osteogenesis was observed in XP, PS, and SP groups at day 14, whereas the SP group demonstrated the greatest bone fill, trabecular numbers, and thickest trabeculae. Bone bridging was evident in the PS and SP group, with significantly increased osteoblasts in the SP group, and osteoclastic cell recruitment was promoted in all bioactive molecule-treated groups. At day 28, osteogenesis was promoted in all bioactive molecule-treated groups. Initial corticalization was noted in the XP, PS, and SP groups. Osteoblasts appeared to be decreased in all groups, and significantly, a greater osteoclastic cell recruitment was noted in the SB and SP groups.

CONCLUSIONS

Both PDGF and simvastatin facilitate dentoalveolar regeneration, and sequential PDGF-simvastatin release (SP group) further accelerated the regeneration process through the enhancement of osteoblastogenesis and the promotion of bone maturation.

Alveolar ridge and maxillary sinus augmentation using rhBMP-2: a systematic review

PURPOSE

The aim of this systematic review was to evaluate clinical and safety data for recombinant human bone morphogenetic protein-2 (rhBMP-2) in an absorbable collagen sponge (ACS) carrier when used for alveolar ridge/maxillary sinus augmentation in humans.

MATERIALS AND METHODS

Clinical studies/case series published 1980 through June 2012 using rhBMP-2/ACS were searched. Studies meeting the following criteria were considered eligible for inclusion: >10 subjects at baseline and maxillary sinus or alveolar ridge augmentation not concomitant with implant placement.

RESULTS

Seven of 69 publications were eligible for review. rhBMP-2/ACS yielded clinically meaningful bone formation for maxillary sinus augmentation that would allow placement of regular dental implants without consistent differences between rhBMP-2 concentrations. Nevertheless, the statistical analysis showed that sinus augmentation following autogenous bone graft was significantly greater (mean bone height: 1.6 mm, 95% CI: 0.5-2.7 mm) than for rhBMP-2/ACS (rhBMP-2 at 1.5 mg/mL). In extraction sockets, rhBMP-2/ACS maintained alveolar ridge height while enhancing alveolar ridge width. Safety reports did not represent concerns for the proposed indications.

CONCLUSIONS

rhBMP-2/ACS appears a promising alternative to autogenous bone grafts for alveolar ridge/maxillary sinus augmentation; dose and carrier optimization may expand its efficacy, use, and clinical application.

Stem cells in dentistry--Part II: Clinical applications

New technologies that facilitate solid alveolar ridge augmentation are receiving considerable attention in the field of prosthodontics because of the growing requirement for esthetic and functional reconstruction by dental implant treatments. Recently, several studies have demonstrated potential advantages for stem-cell-based therapies in regenerative treatments. Mesenchymal stem/stromal cells (MSCs) are now an excellent candidate for tissue replacement therapies, and tissue engineering approaches and chair-side cellular grafting approaches using autologous MSCs represent the clinical state of the art for stem-cell-based alveolar bone regeneration. Basic studies have revealed that crosstalk between implanted donor cells and recipient immune cells plays a key role in determining clinical success that may involve the recently observed immunomodulatory properties of MSCs. Part II of this review first overviews progress in regenerative dentistry to consider the implications of the stem cell technology in dentistry and then highlights cutting-edge stem-cell-based alveolar bone regenerative therapies. Factors that affect stem-cell-based bone regeneration as related to the local immune response are then discussed. Additionally, pre-clinical stem cell studies for the regeneration of teeth and other oral organs as well as possible applications of MSC-based immunotherapy in dentistry are outlined. Finally, the marketing of stem cell technology in dental stem cell banks with a view toward future regenerative therapies is introduced.

Effect of bone morphogenetic protein-2, demineralized bone matrix and systemic parathyroid hormone (1-34) on local bone formation in a rat calvaria critical-size defect model

AIM

To determine the potential of recombinant human bone morphogenetic protein-2 (rhBMP-2) soak-loaded on to an absorbable collagen sponge (ACS) to induce local bone formation compared with the clinical reference demineralized bone matrix (DBM) and to investigate potential additive/synergistic effects of exogenous parathyroid hormone (PTH).

METHODS

Critical-size (8 mm), through-through calvaria osteotomy defects in 160 adult male Sprague-Dawley rats were randomized to receive one of eight interventions: rhBMP-2/ACS, DBM, ACS, or serve as controls (empty defects) combined or not with systemic PTH. Ten animals from each group were followed for 4 and 8 wks for radiographic and histometric analysis. Multivariable analysis was used to assess the effect of experimental intervention and healing time on local bone formation.

RESULTS

In the multivariable analysis, rhBMP-2/ACS exhibited significantly greater histologic bone formation than control (β ± SE: 54.76 ± 5.85, p < 0.001) and ACS (β ± SE: 9.14 ± 3.31, p = 0.007) whereas DBM showed significantly less bone formation than control (β ± SE: -32.32 ± 8.23, p < 0.001). Overall, PTH did not show a significant effect on bone formation (β ± SE: 2.72 ± 6.91, p = 0.70). No significant differences in histological defect closure were observed between 4 and 8 wks for all but the control group without PTH.

CONCLUSION

rhBMP-2/ACS significantly stimulates local bone formation whereas bone formation appears significantly limited by DBM. Systemic application of PTH provided no discernible additive/synergistic effects on local bone formation.

Studies of bone morphogenetic protein-based surgical repair

Over the past several decades, recombinant human bone morphogenetic proteins (rhBMPs) have been the most extensively studied and widely used osteoinductive agents for clinical bone repair. Since rhBMP-2 and rhBMP-7 were cleared by the U.S. Food and Drug Administration for certain clinical uses, millions of patients worldwide have been treated with rhBMPs for various musculoskeletal disorders. Current clinical applications include treatment of long bone fracture non-unions, spinal surgeries, and oral maxillofacial surgeries. Considering the growing number of recent publications related to clincal research of rhBMPs, there exists enormous promise for these proteins to be used in bone regenerative medicine. The authors take this opportunity to review the rhBMP literature paying specific attention to the current applications of rhBMPs in bone repair and spine surgery. The prospective future of rhBMPs delivered in combination with tissue engineered scaffolds is also reviewed.

Alveolar ridge augmentation using implants coated with recombinant human growth/differentiation factor -5 (rhGDF-5). Radiographic observations

OBJECTIVES

Application of growth factors onto dental implant surfaces is being considered to support local bone formation. Bone morphogenetic protein-2 (BMP-2) and BMP-7 have been shown to support local bone formation, but are also associated with adverse events including seroma formation, extensive bone remodeling, and implant displacement captured in the radiographic evaluation. This report presents mineralized tissue formation and associated adverse events following implantation of recombinant human growth/differentiation factor-5 (rhGDF-5) coated onto a purpose-designed titanium porous-oxide implant surface.

MATERIAL AND METHODS

Twelve young adult Labrador dogs were used. Three 10-mm titanium implants/jaw quadrant were placed 5 mm into the alveolar ridge in the posterior mandible following surgical extraction of the premolar teeth and reduction of the alveolar ridge. Six animals received implants coated with rhGDF-5 at 30 or 60 μg/implant in contralateral jaw quadrants. Six animals received implants coated with rhGDF-5 at 120 μg/implant or uncoated implants (sham-surgery control) using the same split-mouth design. The mucoperiosteal flaps were advanced, adapted, and sutured to submerge the implants. Radiographic recordings were made immediately postsurgery (baseline), and at week 4 and 8 (end of study). Two masked examiners performed the analysis using computer enhanced radiographic images.

RESULTS

rhGDF-5 coated implants displayed mineralized tissue formation significantly exceeding that of the sham-surgery control in a dose-dependent order. The greatest increase was observed for implants coated with rhGDF-5 at 60 μg and 120 μg amounting to approximately 2.2 mm for both groups at 8 weeks. Importantly, none of the implants showed evidence of peri-implant bone remodeling, implant displacement, or seroma formation. The newly formed mineralized tissues assumed characteristics of the resident bone.

CONCLUSIONS

rhGDF-5 coated onto a titanium porous-oxide implant surface exhibits a dose-dependent potential to stimulate local mineralized tissue formation. Application of rhGDF-5 appears safe as it is associated with limited, if any, adverse events.

A clinical study of alveolar bone tissue engineering with cultured autogenous periosteal cells: coordinated activation of bone formation and resorption

In ongoing clinical research into the use of cultured autogenous periosteal cells (CAPCs) in alveolar bone regeneration, CAPCs were grafted into 33 sites (15 for alveolar ridge augmentation and 18 for maxillary sinus lift) in 25 cases. CAPCs were cultured for 6weeks, mixed with particulate autogenous bone and platelet-rich plasma, and then grafted into the sites. Clinical outcomes were determined from high-resolution three-dimensional computed tomography (3D-CT) images and histological findings. No serious adverse events were attributable to the use of grafted CAPCs. Bone regeneration was satisfactory even in cases of advanced atrophy of the alveolar process. Bone biopsy after bone grafting with CAPCs revealed prominent recruitment of osteoblasts and osteoclasts accompanied by angiogenesis around the regenerated bone. 3D-CT imaging suggested that remodeling of the grafted autogenous cortical bone particles was faster in bone grafting with CAPCs than in conventional bone grafting. The use of CAPCs offers cell-based bone regeneration therapy, affording complex bone regeneration across a wide area, and thus expanding the indications for dental implants. Also, it enables the content of particulate autogenous bone in the graft material to be reduced to as low as 40%, making the procedure less invasive, or enabling larger amounts of graft materials to be prepared. It may also be possible to dispense with the use of autogenous bone altogether in the future. The results suggest that CAPC grafting induces bone remodeling, thereby enhancing osseointegration and consequently reducing postoperative waiting time after dental implant placement.