[Sinus floor augmentation with simultaneous implant insertion using recombinant human osteogenic protein-1]

Comparison of Material-mediated Bone Regeneration Capacities of Sintered and Non-sintered Xenogeneic Bone Substitutes via 2D and 3D Data

BACKGROUND/AIM

The aim of this study was the development of a new osteoconductivity index to determine the bone healing capacities of bone substitute materials (BSM) on the basis of 3D microcomputed tomographic (μ-CT) data.

MATERIALS AND METHODS

Sinus biopsies were used for the comparative analysis of the integration behavior of two xenogeneic BSM (cerabone® and Bio-Oss®). 3D μ-CT and data sets from histomorphometrical measurements based on 2D histological slices were used to measure the bone-material-contact and the tissue distribution within the biopsies. The tissue reactions to both BSM were microscopically analyzed.

RESULTS

The 3D and 2D results of the osteoconductivity measurements showed comparable material-bone contacts for both BSM, but the 2D data were significantly lower. The same results were found when tissue distribution was measured in both groups. The histopathological analysis showed comparative tissue reactions in both BSM.

CONCLUSION

Osteoconductivity index is a reliable measurement parameter for determining the healing capacities of BSM. The observed differences between both measurement methods could be assigned to the resolution capacity of μ-CT data that did not allow for a precise interface distinction between both BSM and bone tissue. Histomorphometrical data based on histological slides still allow for a more exact evaluation.

A collagen membrane containing osteogenic protein-1 facilitates bone regeneration in a rat mandibular bone defect

OBJECTIVES

Osteogenic protein-1 (OP-1) has shown osteoinductive activities and is useful for clinical treatments, including bone regeneration. Regenerative procedures using a bioabsorbable collagen membrane (BCM) are well established in periodontal and implant dentistry. We evaluated the subsequent effects of the BCM in combination with OP-1 on bone regeneration in a rat mandibular circular critical-sized bone defect in vivo.

DESIGN

We used 8 rats that received surgery in both sides of the mandible, and created the total 16 defects which were divided into 4 groups: Group 1; no treatment, as a control, Group 2; BCM alone, Group 3; BCM containing low dose 0.5μg of OP-1 (L-OP-1), and Group 4; BCM containing high dose 2.0μg of OP-1 (H-OP-1). Newly formed bone was evaluated by micro computed tomography (micro-CT) and histological analyses at 8 weeks postoperatively. In quantitative and qualitative micro-CT analyses of the volume of new bone formation, bone density, and percentage of new bone area was evaluated.

RESULTS

BCM with rhOP-1 significantly increased and accelerated bone volume, bone mineral density, and percentage of new bone area compared to control and BCM alone at 8 weeks after surgery; these enhancements in bone regeneration in the OP-1-treated groups were dose-dependent.

CONCLUSIONS

OP-1 delivered with a BCM may have effective osteoinductive potency and be a good combination for bone regeneration. The use of such a combination device for osteogenesis may result in safer and more predictable bone regenerative outcomes in the future.

Tissue engineering for bone regeneration and osseointegration in the oral cavity

OBJECTIVE

The focus of this review is to summarize recent advances on regenerative technologies (scaffolding matrices, cell/gene therapy and biologic drug delivery) to promote reconstruction of tooth and dental implant-associated bone defects.

METHODS

An overview of scaffolds developed for application in bone regeneration is presented with an emphasis on identifying the primary criteria required for optimized scaffold design for the purpose of regenerating physiologically functional osseous tissues. Growth factors and other biologics with clinical potential for osteogenesis are examined, with a comprehensive assessment of pre-clinical and clinical studies. Potential novel improvements to current matrix-based delivery platforms for increased control of growth factor spatiotemporal release kinetics are highlighting including recent advancements in stem cell and gene therapy.

RESULTS

An analysis of existing scaffold materials, their strategic design for tissue regeneration, and use of growth factors for improved bone formation in oral regenerative therapies results in the identification of current limitations and required improvements to continue moving the field of bone tissue engineering forward into the clinical arena.

SIGNIFICANCE

Development of optimized scaffolding matrices for the predictable regeneration of structurally and physiologically functional osseous tissues is still an elusive goal. The introduction of growth factor biologics and cells has the potential to improve the biomimetic properties and regenerative potential of scaffold-based delivery platforms for next-generation patient-specific treatments with greater clinical outcome predictability.

Use of bone morphogenetic proteins in sinus augmentation procedure

Bone morphogenetic proteins (BMPs) have shown osteoinductive properties, and favorable regenerative responses to the graft materials containing BMPs have been reported. Maxillary sinus augmentation with placement of dental implants is a well-established technique for functional and aesthetic dental rehabilitation of partially or completely edentulous patients with severe maxillary atrophy, and attempts have been made to promote the bone formation using BMPs with different carriers in various animal models in sinus augmentation procedures.In this review, the summary was done on various carriers and the dosages for BMPs in sinus augmentation procedures.

Assessment of the potential of growth factors for localized alveolar ridge augmentation: a systematic review

OBJECTIVE

To systematically assess the literature regarding the clinical, histological, and radiographic outcome of bone morphogenetic proteins (BMP-2, BMP-7), growth/differentiation factor-5 (GDF-5), platelet-derived growth factor (PDGF), and parathyroid hormone (PTH) for localized alveolar ridge augmentation.

MATERIAL AND METHODS

Five separate Medline searches were performed in duplicate for human and animal studies, respectively. The primary outcome of the included studies was bone regeneration of localized alveolar ridge defects or craniofacial defects.

RESULTS

In six human studies, BMP-2 affected local bone augmentation with increasing volume for higher doses. A majority (43 of 45) of animal studies using BMP-2 showed a positive effect in favour of the growth factor (GF). In six of eight studies, a positive effect was associated with the use of BMP-7. Only one animal study was included for GDF-5 revealing statistically significantly higher bone volume. Regarding PDGF, statistically significantly higher bone volume was observed in five of 10 included studies. Four animal studies using PTH revealed statistically significantly more bone regeneration compared with controls.

CONCLUSIONS

Differing levels and quantity of evidence were noted to be available for the GFs evaluated, revealing that BMP-2, BMP-7, GDF-5, PDGF, and PTH may stimulate local bone augmentation to various degrees. Human data for the potential of rhBMP-2 are supportive.

Bone graft versus BMP-7 in a critical size defect--cranioplasty in a growing infant model

Little data are available as regards to the action of bone morphogenetic protein-7 (rhBMP-7) in growing organisms. We put forward two hypotheses: Firstly, that regeneration of calvarial defects with autologous bone grafts would result in equivalent volume and shape as compared to calvaria regenerated with BMP-7. Secondly, that cranial development would remain undisturbed in infant individuals. A one-sided defect of the parietal bone (2x4 cm) including the coronal suture was generated in 2-month-old minipigs (n=17). Group 1: no further treatment (n=5); group 2: particulated iliac bone graft (n=6); group 3: rhBMP-7-composite (500 microg/g collagen+Carboxymethylcellulose, n=6). After the experimental period (4 months) with fluorochrome labeling, examination was performed by computed-tomography and non-decalcified histology. Group 1: major bony gaps remained, proving that defects of critical size were generated. Group 2: minor bony gaps remained, the bone volume was significantly reduced on the treated as compared to untreated sides (P=0.028). Group 3: bony continuity was seen in all cases and no significant difference of bone volumes of treated versus untreated sides (P=0.075) was found. Skull diameters increased by 16.4% but the physiological centrifugal cranial expansion remained undisturbed. Our first hypothesis was contradicted: contrary to our former assumption, bone induction by rhBMP-7 was superior to particulated bone transplants. In this growing model, calvaria approaching normal volume and shape were observed. However, only the quantity not the quality of bone regenerates was different. Our second hypothesis was confirmed: disruption of further cranial development was not seen after bone transplantation or rhBMP-7 implantation.

Tissue engineering in otorhinolaryngology

Tissue engineering is a field of research with interdisciplinary cooperation between clinicians, cell biologists, and materials research scientists. Many medical specialties apply tissue engineering techniques for the development of artificial replacement tissue. Stages of development extend from basic research and preclinical studies to clinical application. Despite numerous established tissue replacement methods in otorhinolaryngology, head and neck surgery, tissue engineering techniques opens up new ways for cell and tissue repair in this medical field. Autologous cartilage still remains the gold standard in plastic reconstructive surgery of the nose and external ear. The limited amount of patient cartilage obtainable for reconstructive head and neck surgery have rendered cartilage one of the most important targets for tissue engineering in head and neck surgery. Although successful in vitro generation of bioartificial cartilage is possible today, these transplants are affected by resorption after implantation into the patient. Replacement of bone in the facial or cranial region may be necessary after tumor resections, traumas, inflammations or in cases of malformations. Tissue engineering of bone could combine the advantages of autologous bone grafts with a minimal requirement for second interventions. Three different approaches are currently available for treating bone defects with the aid of tissue engineering: (1) matrix-based therapy, (2) factor-based therapy, and (3) cell-based therapy. All three treatment strategies can be used either alone or in combination for reconstruction or regeneration of bone. The use of respiratory epithelium generated in vitro is mainly indicated in reconstructive surgery of the trachea and larynx. Bioartificial respiratory epithelium could be used for functionalizing tracheal prostheses as well as direct epithelial coverage for scar prophylaxis after laser surgery of shorter stenoses. Before clinical application animal experiments have to prove feasability and safety of the different experimental protocols. All diseases accompanied by permanently reduced salivation are possible treatment targets for tissue engineering. Radiogenic xerostomia after radiotherapy of malignant head and neck tumors is of particular importance here due to the high number of affected patients. The number of new diseases is estimated to be over 500,000 cases worldwide. Causal treatment options for radiation-induced salivary gland damage are not yet available; thus, various study groups are currently investigating whether cell therapy concepts can be developed with tissue engineering methods. Tissue engineering opens up new ways to generate vital and functional transplants. Various basic problems have still to be solved before clinically applying in vitro fabricated tissue. Only a fraction of all somatic organ-specific cell types can be grown in sufficient amounts in vitro. The inadequate in vitro oxygen and nutrition supply is another limiting factor for the fabrication of complex tissues or organ systems. Tissue survival is doubtful after implantation, if its supply is not ensured by a capillary network.

Carboxymethylcellulose-stabilized collagenous rhOP-1 device?a novel carrier biomaterial for the repair of mandibular continuity defects

Human recombinant osteogenic protein-1 (rhOP-1) is osteoinductive. Efforts are made to develop carrier biomaterials with improved space-keeping properties. Bovine collagen type I matrix charged with rhOP-1 was suggested to be an advantageous device of relative liquid quality. We hypothesized that the addition of carboxymethylcellulose (CMC) may stabilize the device and facilitate the regeneration of mandibular continuity defects without further addition of mineralized carrier materials. To test this hypothesis, the anatomical shape, functional remodeling, and mechanical stability of such bony regenerates were evaluated in the course of an animal experiment. Mandibular continuity defects of 5 cm in size were created in five Göttingen minipigs on one side (contralateral hemimandible: control) and bridged with titanium plates. Four animals were treated with the rhOP-1 device (3000 microg rhOP-1, 2 g collagen, 1 g CMC), and one animal was treated with a placebo device omitting rhOP-1. After 12 weeks of experimental period, bony continuity was reestablished in rhOP-1-treated hemimandibles. The bony regenerates were of good anatomical shape, volume, and functional remodeling. Placebo treatment led to insufficient bony regenerates of significant lower bone volume (volume in 3D-CT scan 29.81 cm(3) vs 8.85 cm(3)). To produce 1 mm of bending, 1972 N were needed for rhOP-1-treated hemimandibles, 2617 N for control hemimandibles, and 642 N for the placebo treated hemimandible. CMC stabilization of collagen carrier biomaterials for rhOP-1 provides good plasticity as well as excellent space-keeping properties and may not interfere with osteoinduction. The results of this preliminary study suggest that the applied rhOP-1 device offers a potential option for further studies on the reconstruction of mandibular defects.