Extraction socket grafting and buccal wall regeneration with recombinant human bone morphogenetic protein-2 and acellular collagen sponge

Reconstruction of the Extraction Socket: Methods, Manipulations, and Management

Extensive reviews have concluded that grafting of the socket reduces bone loss regardless of product or method. However, nothing has been shown to reliably and completely maintain alveolar dimensions. We advocate a biologically driven and anatomically based approach for reconstruction of the socket. There are various socket manipulations that we have found to predictably prepare a site for dental implant. The combination of graft construct design and socket management maximizes graft success for any practitioner. Each socket should be treated individually, and products or methods used that are coincident with the complexity of the defect in question.

Enhanced Wound Healing Potential of Primary Human Oral Fibroblasts and Periodontal Ligament Cells Cultured on Four Different Porcine-Derived Collagen Matrices

Xenogenic collagen-based matrices represent an alternative to subepithelial palatal connective tissue autografts in periodontal and peri-implant soft tissue reconstructions. In the present study, we aimed to investigate the migratory, adhesive, proliferative, and wound-healing potential of primary human oral fibroblasts (hOF) and periodontal ligament cells (hPDL) in response to four commercially available collagen matrices. Non-crosslinked collagen matrix (NCM), crosslinked collagen matrix (CCM), dried acellular dermal matrix (DADM), and hydrated acellular dermal matrix (HADM) were all able to significantly enhance the ability of hPDL and hOF cells to directionally migrate toward the matrices as well as to efficiently repopulate an artificially generated wound gap covered by the matrices. Compared to NCM and DADM, CCM and HADM triggered stronger migratory response. Cells grown on CCM and HADM demonstrated significantly higher proliferative rates compared to cells grown on cell culture plastic, NCM, or DADM. The pro-proliferative effect of the matrices was supported by expression analysis of proliferative markers regulating cell cycle progression. Upregulated expression of genes encoding the adhesive molecules fibronectin, vinculin, CD44 antigen, and the intracellular adhesive molecule-1 was detected in hPDL and hOF cells cultured on each of the four matrices. This may be considered as a prerequisite for good adhesive properties of the four scaffolds ensuring proper cell–matrix and cell–cell interactions. Upregulated expression of genes encoding TGF-β1 and EGF growth factors as well as MMPs in cells grown on each of the four matrices provided support for their pro-proliferative and pro-migratory abilities. The expression of genes encoding the angiogenic factors FGF-2 and VEGF-A was dramatically increased in cells grown on DADM and HADM only, suggesting a good basis for accelerated vascularization of the latter. Altogether, our results support favorable influence of the investigated collagen matrices on the recruitment, attachment, and growth of cell types implicated in oral soft tissue regeneration. Among the four matrices, HADM has consistently exhibited stronger positive effects on the oral cellular behavior. Our data provide solid basis for future investigations on the clinical application of the collagen-based matrices in surgical periodontal therapy.

Adsorption and Release of Growth Factors from Four Different Porcine-Derived Collagen Matrices

Xenogeneic acellular collagen matrices represent a safe alternative to autologous soft tissue transplants in periodontology and implant dentistry. Here, we aimed to investigate the adsorption and release of growth factors from four porcine-derived collagen matrices using enzyme-linked immunosorbent assay. Non-crosslinked collagen matrix (NCM), crosslinked collagen matrix (CCM), dried acellular dermal matrix (DADM), and hydrated acellular dermal matrix (HADM) adsorbed each of the following growth factors, TGF-β1, FGF-2, PDGF-BB, GDF-5 and BMP-2, with an efficiency close to 100%. Growth factor release for a 13-day period was in the range of 10-50% of the adsorbed protein, except for the BMP-2 release that was in the range of 5-7%. Generally, protein release occurred in two phases. Phase I was arbitrary defined by the highest release from the matrices, usually within 24 h. Phase II, spanning the period immediately after the peak release until day 13, corresponded to the delayed release of the growth factors from the deeper layers of the matrices. HADM showed significantly (P < 0.001) higher TGF-β1, FGF-2, and PDGF-BB release in phase II, compared to the rest of the matrices. NCM exhibited significantly (P < 0.001) higher FGF-2 release in phase II, compared to CCM and DADM as well as a characteristic second peak in PDGF-BB release towards the middle of the tested period. In contrast to NCM and HADM, CCM and DADM showed a gradual and significantly higher release of GDF-5 in the second phase. Several burst releases of BMP-2 were characteristic for all matrices. The efficient adsorption and sustained protein release in the first 13 days, and the kinetics seen for HADM, with a burst release within hours and high amount of released growth factor within a secondary phase, may be beneficial for the long-term tissue regeneration following reconstructive periodontal surgery.

Extraction Socket Preservation Using Growth Factors and Stem Cells: a Systematic Review

Objectives

To evaluate the reported literature on the use of stem cells or growth factors for post extraction treatment of the alveolar bone.

Material and Methods

A NCBI PubMed and PubMed Central databases search was conducted between September 2010 and August 2018, to identify animal or clinical studies reporting the clinical, radiographical and/or histological outcomes of socket preservation techniques after applying mesenchymal stem cells or growth factors. Only studies published in English language in the last 10 years were included in the study.

Results

Eleven studies were identified fulfilling the inclusion criteria. They evaluate a total of 386 post extraction sockets. The main tested materials identified in the current review were bone morphogenetic protein-2 - 3 studies and mesenchymal stem cells - 3 studies. Other comparators were bone morphogenetic protein-9, platelet-derived growth factor-BB homodimers and bone marrow. Overall evaluation indicate positive results for all test groups showing differences in final socket width between 0.64 and 1.28 mm favouring the test groups. Histologically, no particular differences are detected between test and control groups. Most of the studies present low risk of bias.

Conclusions

In general, the use of mesenchymal stem cells or bioactive osteogenic molecules favours bone regeneration after tooth extraction, as evaluated clinically, radiographically and histologically. However, specific differences that support particular recommendations are still unclear in light of the current published evidence. Future studies should include the standardization of the mesenchymal stem cells selection and purification as well as dosage and delivery methods of bioactive molecules.

Repair of surgical bone defects grafted with hydroxylapatite + β-TCP combined with hyaluronic acid and collagen membrane in rabbits: A histological study

Objectives

This study aimed to assess the repair of bone defects with or without grafts using biphasic synthetic micro-granular hyaluronic acid (HA) with β-TCP and bovine type I collagen (Osteon II Collagen) with or without either hyaluronic acid or a collagen membrane in surgically created bone defects in the tibia of rabbits.

Methods

Fifteen male rabbits were divided into 3 groups, each with 5 rabbits. Two bone defects were made in each tibia. In the right tibia, the defects were either filled with clot as a control or grafted with Osteon II Collagen and hyaluronic acid. In the left tibia, the other two defects were filled with Osteon II Collagen alone or with Osteon II Collagen and a collagen membrane. The specimens were observed one, two, and four weeks after surgery. Histological examinations were used to evaluate the degree of healing according to the amount of newly formed bone.

Results

The combination of the bone grafting biomaterial with hyaluronic acid was found to develop into the most advanced stages of the bone repair process at the second and fourth week only (p ≤ 0.05), compared to the biomaterial with a collagen membrane, as well as the other groups. On the other hand, the biomaterial in combination with a collagen membrane showed significantly more bone formation than the biomaterial alone or the control group by the fourth week.

Conclusions

The local application of hyaluronic acid and collagen membranes made a greater contribution to the bone repair process in the tibia of rabbits than the bone graft substitute (Osteon II Collagen) alone.

Recombinant human BMP9 (RhBMP9) in comparison with rhBMP2 for ridge augmentation following tooth extraction: An experimental study in the Beagle dog

OBJECTIVES

The purpose of this study was to compare the effects of rhBMP2 with rhBMP9 on ridge augmentation following healing of extraction sockets in dogs.

MATERIAL AND METHODS

Five male Beagle dogs, approximately 12 months of age, were used. The mesial roots of the four maxillary premolars were endodontically treated. The distal roots were extracted, and the buccal bony walls removed. All extraction sockets were filled with deproteinized bovine bone mineral (DBBM). A collagen membrane was soaked with 4 μg or 20 μg of rhBMP9, 20 μg of rhBMP2 or sterile saline and placed over the augmented sites. All animals were euthanized after 8 weeks of healing and investigated by micro-CT and histologic analysis. A one-way ANOVA with Tukey's HSD post hoc test was used to compare the differences between the four groups.

RESULTS

New bone apposition in all defects was observed from the original bone. RhBMP samples showed an increase in bone formation in the buccal area and better integration of DBBM particles when compared to control sites. Both rhBMP9 defects showed higher values of bone (p = 0.024), bone marrow (p = 0.044), and total augmentation volume (p = 0.033) than the rhBMP2 (20 μg) or control sites. Highest bone area was found in rhBMP9 defects (p = 0.895).

CONCLUSIONS

Within the limitations of the present study, rhBMP9 sites demonstrated higher bone-inducing potential in combination with DBBM than rhBMP2. While rhBMP9s failed to demonstrate a clear dose-response relationship to the outcomes, future studies are necessary to evaluate the appropriate dose and carrier systems.

Absorbable collagen sponges loaded with recombinant bone morphogenetic protein 9 induces greater osteoblast differentiation when compared to bone morphogenetic protein 2

The use of growth factors for the regeneration of soft and hard tissues has been utilized extensively in dental medicine over the past decade. Recently our group found that recombinant human bone morphogenetic protein 9 (rhBMP9) was more osteopromotive than recombinant human bone morphogenetic protein 2 (rhBMP2) when combined with a deprotenized bovine bone mineral bone grafting material. The aim of the present in vitro study was to evaluate the regenerative potential of an absorbable collagen sponge(ACS) specifically designed for extraction socket healing loaded with rhBMP9 when compared to rhBMP2. The adsorption and release kinetics of rhBMP2 and rhBMP9 were first investigated by enzyme-linked immunosorbent assay quantification. Then, the cellular effects of stromal cell line (ST2) preosteoblasts were investigated utilizing four groups including rhBMP2 and rhBMP9 at both low(10 ng/ml) and high(100 ng/ml) concentrations loaded onto ACS. Cellular attachment(8 hours) and proliferation(1, 3, and 5 days) as well as osteoblast differentiation were investigated by real-time polymerase chain reaction (PCR) at 3 and 14 days, alkaline phosphatase (ALP) activity at 7 days, and alizarin red staining at 14 days. ACS fully adsorbed both rhBMP2 and rhBMP9 that were slowly released up to 10 days. Although neither rhBMP2 nor rhBMP9 had any effects on cell attachment or proliferation, pronounced effects were observed on osteoblast differentiation. ALP activity was increased seven-fold with rhBMP2-high, whereas a marked 10-fold and 20-fold increase was observed with rhBMP9-low and high loaded to ACS, respectively. Furthermore, mRNA levels of collagen1, ALP, bone sialoprotein, and osteocalcin were all significantly higher for rhBMP9 when compared to control or rhBMP2 groups. Alizarin red staining further confirmed that rhBMP9-low and high demonstrated marked increases in mineralization potential when compared to rhBMP2-high. The results demonstrate the marked effect of rhBMP9 on osteoblast differentiation when combined with ACS in comparison to rhBMP2 at doses as much as 10 times lower. Further in vivo studies are necessary to investigate whether the regenerative potential is equally as potent.

Osteogain® loaded onto an absorbable collagen sponge induces attachment and osteoblast differentiation of ST2 cells in vitro

OBJECTIVES

Dimensional changes of the alveolar bone following tooth extraction are a major challenge in daily dental practice. To limit bone loss, a variety of biomaterials including bone grafts, barrier membranes, and growth factors have been utilized either alone or in combination therapies to increase the speed and quality of new bone formation. The aim of the present in vitro study was to investigate the regenerative potential of Osteogain®, a new liquid carrier system of enamel matrix derivative (EMD) in combination with an absorbable collagen sponge (ACS) specifically designed for extraction socket healing.

MATERIALS AND METHODS

The potential of ACS was first investigated using ELISA to quantify total amelogenin adsorption and release from 0 to 10 days. Thereafter, the cellular effects of ST2 pre-osteoblasts were investigated for cellular attachment at 8 h and cell proliferation at 1, 3, and 5 days as well as osteoblast differentiation by real-time PCR and alizarin red staining for cells seeded on (1) tissue culture plastic, (2) ACS alone, and (3) ACS + Osteogain®.

RESULTS

ACS efficiently loaded nearly 100% of the amelogenin proteins found in Osteogain® which were gradually released up to a 10-day period. Osteogain® also significantly induced a 1.5-fold increase in cell attachment and resulted in a 2-6-fold increase in mRNA levels of osteoblast differentiation markers including runt-related transcription factor 2 (Runx2), collagen1a2, alkaline phosphatase, and bone sialoprotein as well as induced alizarin red staining when combined with ACS.

CONCLUSIONS

In summary, these findings suggest that Osteogain® is capable of inducing osteoblast attachment and differentiation when combined with ACS. Future animal studies and randomized human clinical trials are necessary to further support these findings.

CLINICAL RELEVANCE

The use of Osteogain® in combination with ACS may provide a valuable means to limit dimensional changes following tooth extraction.

Resorbable collagen membranes: histopathologic features

OBJECTIVE

Resorbable collagen membranes (RCMs) are commonly used by oral surgeons, periodontists, and endodontists for multiple purposes. We report 6 cases of RCMs that did not resorb as expected and describe the histopathologic features.

STUDY DESIGN

Cases of an unusual fibrillar foreign material were noted in biopsy specimens curetted from bone. Hematoxylin-eosin and Masson trichrome stains were performed. Clinicians were contacted for detailed clinical information.

RESULTS

There were 3 men and 3 women. RCMs presented as hyalinized, paucicellular, delicate eosinophilic fibrils or a meshwork without a foreign body reaction. They were refractile and stained for Masson trichrome as expected. These RCMs persisted longer than expected (2-6 weeks) in 3 cases and may have retarded healing in 5 cases.

CONCLUSIONS

Although RCM is supposed to be fairly rapidly resorbable, this material sometimes persists within wound sites without any obvious foreign body reaction and may retard healing.