Cranioplasty Using a Novel Osteoconductive Scaffold and Platelet Gel.

BACKGROUND: Commonly used materials for cranioplasty include autogenous bone grafts, methyl methacrylate, and titanium mesh. We evaluated a novel osteoconductive scaffold [N-isopropylacrylamide cross-linked with acrylic acid using γ-rays (ANa powder)] mixed with platelet gel for cranioplasty. METHODS: ANa powder mixed with platelet gel was implanted into a 15 × 15-mm, full-thickness calvarial bone defect in 5 New Zealand white rabbits. ANa powder mixed with phosphate-buffered saline was implanted in 5 rabbits. The calvarial bone defect was left unreconstructed in another 5 rabbits. Twelve weeks after surgery, computed tomography examination was used to evaluate the radiographic evidence of bone healing in vivo. Bone specimens were then retrieved for histologic study. RESULTS: The ANa scaffold mixed with platelet gel is biocompatible, biodegradable, and both osteoconductive and osteoinductive, leading to progressive growth of new bone into the calvarial bone defect. CONCLUSION: The use of this novel osteoconductive scaffold combined with osteoinductive platelet gel offers a valuable alternative for the reconstruction of calvarial bone defects.

Single-donor allogeneic platelet fibrin glue and osteoconductive scaffold in orbital floor fracture reconstruction.

BACKGROUND: Commonly used materials for orbital floor fracture reconstruction include autologous cranial bone graft and titanium mesh. We have evaluated here a biomaterial combining biphasic calcium phosphate (hydroxyapatite [HA]/ß-tricalcium phosphate [TCP]) osteoconductive scaffold with single-donor allogeneic platelet fibrin glue. METHODS: The study was conducted on 10 consecutive patients with a follow-up of up to 4 years. Platelet fibrin glue was prepared by mixing equal volumes of single-donor platelet-rich plasma and cryoprecipitate with HA/ß-TCP followed by activation with human thrombin prepared by plasma activation. Postoperative evaluations included serial photographs, repeated physical examination, and 3-dimensional computed tomography scan performed 2 years after surgery. RESULTS: The fibrin-rich platelet biomaterial was easy to mold and to apply on the surgical site allowing the surgeon to sculpt accurately the bone defect, providing mechanical stability while avoiding spillage of the scaffold. No infection of the orbit or extrusion of HA/ß-TCP was observed. Ocular motility was normal, and no diplopia or enophthalmos of the injured orbit was noted. Coronal computed tomography scans of the reconstructed orbits revealed good restoration of the orbital floor defect in all 10 patients. CONCLUSIONS: The use of single-donor platelet fibrin glue combined with an osteoconductive scaffold offers a valuable alternative to autologous cranial bone graft or titanium mesh in the reconstruction of orbital floor bone defect.

Dental optical coherence tomography.

This review paper describes the applications of dental optical coherence tomography (OCT) in oral tissue images, caries, periodontal disease and oral cancer. The background of OCT, including basic theory, system setup, light sources, spatial resolution and system limitations, is provided. The comparisons between OCT and other clinical oral diagnostic methods are also discussed.

Combination of guided osteogenesis with autologous platelet-rich fibrin glue and mesenchymal stem cell for mandibular reconstruction.

BACKGROUND: This study examined whether a combination of autologous platelet-rich fibrin glue (PRFG) with mesenchymal stem cells (MSCs) and MEDPOR as guided tissue regeneration (GTR) could act as an osteogenic substitute and whether this treatment yields faster new bone formation than MEDPOR alone or PRFG plus MSC. MATERIAL: MSCs were harvested and isolated from the bone marrow of dog ilium. Full-thickness bony defects (1.5×1.5 cm) were created in the bilateral mandible angles of the dog. Treatments for bone defect in each group were as follows: group I (n=4), MEDPOR sheet as GTR and autologous PRFG/MSCs admixtures; group II (n=4), autologous PRFG/MSCs admixtures; group III (n=4), MEDPOR sheet as GTR; and group IV (n=4), control (empty defect). The percentage of new bone regeneration in computerized tomography at 2 months and 4 months was calculated by Analyze version 7.0 software. The mandibles were harvested from all specimens at 4 months, and the grafted sites were evaluated by gross, histologic, and X-ray examination. RESULTS: By radiographic analysis at 16 weeks posttransplantation, it was shown that an average of 72.8%±8.02% new bone formation in group I, 53.34%±6.87% in group II, 26.58%±6.41% in group III, and 15.14%±2.37% in group IV. Histologic examination revealed that the defect was repaired by typical bone tissue in groups I and II, whereas only minimal bone formation with fibrous connection was observed in the groups III and IV group. Besides, muscle incarceration was found in groups II and IV without MEDPOR as GTR. CONCLUSION: Autologous PRFG plus osteoinduced MSCs have good potential for bone regeneration. In combination with MEDPOR as GTR, bone regeneration is enhanced by preventing soft tissue ingrowth hindering bone regeneration.

Evaluation of bone growth using artificial bone substitute (osteoset) and platelet gel mixtures: a preliminarily study in dogs.

Platelet gels (PG), activated by bovine thrombin (BT), have increasingly been used in orthopedic surgery. However, BT may induce immunological reactions and carry potential viral and prion risks. To avoid these side effects, thrombin derived from human plasma (human thrombin, HT) is becoming the preferred platelet activator to prepare PG. However, limited experience and data on the clinical benefits of HT-generated PG (HTPG) in orthopedic surgery is reported. Consequently, we designed and performed a series of studies in dogs to compare the impacts of promotion of bone growth by an artificial bone substitute (Osteoset) in combination with HTPG or without it in the spinal repair experiments. X-ray observations and histological studies were performed at predetermined periods post-operation. The preliminary results revealed the preparation of HTPG was easy and required less than 30 minutes. HTPG was capable of embedding the artificial bone substitute Osteoset to prepare a sticky and easily manipulated composite for the application into spinal defect. We found HTPG exhibited enhancement of grafting capacity in consolidation of bone mass. After 12 weeks, tissue reconstruction reached approximately 80% of the injury defects when treated by HTPG/Osteoset combination, but only 30 approximately 40% in the absence of HTPG. The physiological activity of artificial bone substitute combined with PG activated by HT may therefore open beneficial prospects for more successful and safer bone formation in spine procedures in the near future.

Enzyme-crosslinked gene-activated matrix for the induction of mesenchymal stem cells in osteochondral tissue regeneration.

The development of osteochondral tissue engineering is an important issue for the treatment of traumatic injury or aging associated joint disease. However, the different compositions and mechanical properties of cartilage and subchondral bone show the complexity of this tissue interface, making it challenging for the design and fabrication of osteochondral graft substitute. In this study, a bilayer scaffold is developed to promote the regeneration of osteochondral tissue within a single integrated construct. It has the capacity to serve as a gene delivery platform to promote transfection of human mesenchymal stem cells (hMSCs) and the functional osteochondral tissues formation. For the subchondral bone layer, the bone matrix with organic (type I collagen, Col) and inorganic (hydroxyapatite, Hap) composite scaffold has been developed through mineralization of hydroxyapatite nanocrystals oriented growth on collagen fibrils. We also prepare multi-shell nanoparticles in different layers with a calcium phosphate core and DNA/calcium phosphate shells conjugated with polyethyleneimine to act as non-viral vectors for delivery of plasmid DNA encoding BMP2 and TGF-ß3, respectively. Microbial transglutaminase is used as a cross-linking agent to crosslink the bilayer scaffold. The ability of this scaffold to act as a gene-activated matrix is demonstrated with successful transfection efficiency. The results show that the sustained release of plasmids from gene-activated matrix can promote prolonged transgene expression and stimulate hMSCs differentiation into osteogenic and chondrogenic lineages by spatial and temporal control within the bilayer composite scaffold. This improved delivery method may enhance the functionalized composite graft to accelerate healing process for osteochondral tissue regeneration. STATEMENT OF SIGNIFICANCE: In this study, a gene-activated matrix (GAM) to promote the growth of both cartilage and subchondral bone within a single integrated construct is developed. It has the capacity to promote transfection of human mesenchymal stem cells (hMSCs) and the functional osteochondral tissues formation. The results show that the sustained release of plasmids including TGF-beta and BMP-2 from GAM could promote prolonged transgene expression and stimulate hMSCs differentiation into the osteogenic and chondrogenic lineages by spatial control manner. This improved delivery method should enhance the functionalized composite graft to accelerate healing process in vitro and in vivo for osteochondral tissue regeneration.