Biomaterials-aided mandibular reconstruction using in vivo bioreactors.

Large mandibular defects are clinically challenging to reconstruct due to the complex anatomy of the jaw and the limited availability of appropriate tissue for repair. We envision leveraging current advances in fabrication and biomaterials to create implantable devices that generate bone within the patients themselves suitable for their own specific anatomical pathology. The in vivo bioreactor strategy facilitates the generation of large autologous vascularized bony tissue of customized geometry without the addition of exogenous growth factors or cells. To translate this technology, we investigated its success in reconstructing a mandibular defect of physiologically relevant size in sheep. We fabricated and implanted 3D-printed in vivo bioreactors against rib periosteum and utilized biomaterial-based space maintenance to preserve the native anatomical mandibular structure in the defect site before reconstruction. Nine weeks after bioreactor implantation, the ovine mandibles were repaired with the autologous bony tissue generated from the in vivo bioreactors. We evaluated tissues generated in bioreactors by radiographic, histological, mechanical, and biomolecular assays and repaired mandibles by radiographic and histological assays. Biomaterial-aided mandibular reconstruction was successful in a large superior marginal defect in five of six (83%) sheep. Given that these studies utilized clinically available biomaterials, such as bone cement and ceramic particles, this strategy is designed for rapid human translation to improve outcomes in patients with large mandibular defects.

Human Dental Pulp Stem Cells in Rat Mandibular Bone Defects.

This study aimed to evaluate the use of human dental pulp stem cells (hDPSCs) in non-critical-sized mandibular bone defects in rats. hDPSCs from permanent teeth were isolated and engrafted in mandibular bone defects in rats for 7, 14, and 28 days; bone defects without cells formed the control group. Samples were evaluated by scanning electron microscopy (SEM), light microscopy (hematoxylin and eosin staining), and the regeneration area was measured by the Image J program. Before surgery procedures, the human dental pulp cells were characterized as dental pulp stem cells: fusiform morphology, plastic-adherent; expression of CD105, CD73, and CD90; lack of expression of CD45 and CD34, and differentiated into osteoblasts, adipocytes, and chondroblasts. The results indicated that within 7 days the control group presented a pronounced bone formation when compared with the treated group (p < 0.05). After 14 days, the treated group showed an increase in bone formation, but with no statistical difference among the groups (p > 0.05). In the final evaluated period there was no difference between the control group and the treated group (p > 0.05). There was a significant difference between 7 and 14 days (p < 0.05) and between 7 and 28 days (p < 0.05) in the treated group. In conclusion, there is no evidence that the use of hDPSCs in the conditions of this study could improve bone formation in non-critical-sized mandibular bone defects.

[SOME REACTIONS OF THE REGIONAL LYMPH NODES OF RATS AFTER IMPLANTATION OF MULTIPOTENT STROMAL CELLS ADSORBED ON POLYHYDROXYALKANOATE INTO A BONE TISSUE DEFECT].

The reactions of the regional lymph nodes, caused by implantation of the autologous multipotent stromal cells of bone marrow origin (AMSCBMO) to accelerate the healing of mandibular bone defect were studied by fluorescent microscopy in inbred male Wag rats aged 6 months (n=62). After the introduction of polyhydroxyalkanoate transplant containing adsorbed AMSCBMO with a transfected Green Fluorescent Protein (GFP) gene into a damaged bone area, the lymphoid nodules in submandibular lymph nodes demonstrated the appearance of numerous large macrophages containing multiple oval fluorescent inclusions in the cytoplasm. The number of these macrophages increased within 2 weeks after surgery and then began to decline. Apparently, AMSCBMO introduced in this way, were partially absorbed by macrophages. After destruction of the structures formed from AMSCBMO, the debris was also phagocytized by macrophages. In either case, these macrophages appeared in the germinal centers of lymphoid nodules in lymph nodes, where the induction of immune responses against DNA and GFP protein was probable.

Flapless cortical bone damage has no effect on medullary bone mesial to teeth being moved.

INTRODUCTION: In this study, we evaluated the effects of bone awl-induced damage to bone surrounding a tooth that was moved. METHODS: A randomized split-mouth design with 7 foxhounds was performed to evaluate protraction of the mandibular third premolars for 56 days with 200 g of orthodontic force. Before initiating tooth movements, a bone awl was used on the experimental side to create 60 buccal and lingual microfracture injuries to the cortical bone without a periosteal flap. Tooth movements were performed on the control and experimental sides. Microcomputed tomography and histology were used to assess bone morphology and modeling. Radiographic and caliper measures were used to assess tooth movements. RESULTS: The awl-induced injuries produced significant damage and microfractures (95 mm(3)). Buccal and lingual cortical bone volume fractions and densities were significantly less and cortical modeling was significantly greater on the experimental sides than on the control sides. Bone volume fractions and densities mesial to the third premolars were the same on the experimental and control sides. Experimental side tooth movements (1.40 ± 0.25 mm) were statistically the same as the control side tooth movements (1.57 ± 0.45 mm). CONCLUSIONS: The effects of flapless, bone awl-induced damage were limited to the cortical bone. Because there was no effect on the medullary bone mesial to the tooth being moved, no differences in tooth movements were produced.

Delivery of growth factors using a smart porous nanocomposite scaffold to repair a mandibular bone defect.

Implantation of a porous scaffold with a large volume into the body in a convenient and safe manner is still a challenging task in the repair of bone defects. In this study, we present a porous smart nanocomposite scaffold with a combination of shape memory function and controlled delivery of growth factors. The shape memory function enables the scaffold with a large volume to be deformed into its temporal architecture with a small volume using hot-compression and can subsequently recover its original shape upon exposure to body temperature after it is implanted in the body. The scaffold consists of chemically cross-linked poly(ε-caprolactone) (c-PCL) and hydroxyapatite nanoparticles. The highly interconnected pores of the scaffold were obtained using the sugar leaching method. The shape memory porous scaffold loaded with bone morphogenetic protein-2 (BMP-2) was also fabricated by coating the calcium alginate layer and BMP-2 on the surface of the pore wall. Under both in vitro and in vivo environmental conditions, the porous scaffold displays good shape memory recovery from the compressed shape with deformed pores of 33 µm in diameter to recover its porous shape with original pores of 160 µm in diameter. In vitro cytotoxicity based on the MTT test revealed that the scaffold exhibited good cytocompatibility. The in vivo micro-CT and histomorphometry results demonstrated that the porous scaffold could promote new bone generation in the rabbit mandibular bone defect. Thus, our results indicated that this shape memory porous scaffold demonstrated great potential for application in bone regenerative medicine.

[Mandibular bone tissue regeneration after the introduction of the implantation system performed on the basis of carbon composite material].

The purpose of this study was to investigate the processes of regeneration of bone tissue after the introduction of new implant systems. In the experiment, performed on 10 male pigs of Landras breed aged 50-55 days and weighing 17-18.5 kg, the time course of histological changes was studied in the area of mandibular regeneration after the formation of tissue defect and the introduction of the implant of a proposed construction. Morphological analysis of the experimental results 90, 180 and 270 days after the operation demonstrated the process of reparative regeneration of damaged bone along implant-bone block boundaries. Bone repair proceeded through the stage of formation of the woven bone with its progressive substitution by the lamellar bone, with the maintenance of the shape, size and symmetry of the damaged organ.

[Morphological features of reparative osteogenesis of experimental mandibular hole defects with use of osteoplastic material "Hialuost"].

On 45 outbred crawls in a comparative aspect studied motion of reparated osteogenesis in an area holed defects of lower jaw. It is well-proven positive influence is on the processes of alteration bone-tissue regenerat with formation of mature organspetiality of bone tissue.

Traumatic thrombosis of internal carotid artery sustained by transfer of kinetic energy.

A 31-year-old male patient with a fatal thrombosis of the internal carotid artery caused by gun shot injury was presented in this case report. The patient was referred to the hospital with a diffuse edema on his left cheek. On otolaryngologic examination, there was a bullet entrance hole at the left mandibular corpus. No exit hole could be found. The finding from his axial computed tomography of neck and paranasal sinuses was normal. On neurological examination, a dense right hemiparesis was observed. In his cerebral angiogram, left common carotid artery was totally obliterated. Diffuse ischemia was observed in the left cerebral hemisphere. Despite intensive interventions, the patient died 4 days after the accident. In the autopsy, a large thrombosis was obtained in the left common carotid artery. This case emphasizes a fatal kinetic energy effect in vascular structures. It is stressed that a gun shot injury could be fatal with its indirect kinetic energy effects at subacute phase.

Microdamage of the cortical bone during mini-implant insertion with self-drilling and self-tapping techniques: a randomized controlled trial.

INTRODUCTION: The purpose of this research was to evaluate microdamage accumulation after mini-implant placement by self-drilling (without a pilot hole) and self-tapping (screwed into a pilot hole) insertion techniques. The null hypothesis was that the mini-implant insertion technique would have no influence on microcrack accumulation and propagation in the cortical bones of the maxillae and mandibles of adult hounds. METHODS: Mini-implants (n = 162; diameter, 1.6 mm; length, 6 mm) were placed in the maxillae and mandibles of 9 hounds (12-14 months old) with self-drilling and self-tapping insertion techniques. The techniques were randomly assigned to the left or the right side of each jaw. Each hound received 18 mini-implants (10 in the mandible, 8 in the maxilla). Histomorphometric parameters including total crack length and crack surface density were measured. The null hypothesis was rejected in favor of an alternate hypothesis: that the self-drilling technique results in more microdamage (microcracks) accumulation in the adjacent cortical bone in both the maxilla and the mandible immediately after mini-implant placement. A cluster level analysis was used to analyze the data on the outcome measured. Since the measurements were clustered within dogs, a paired-samples t test was used to analyze the average differences between insertion methods at both jaw locations. A significance level of 0.05 was used for both analyses. RESULTS: The self-drilling technique resulted in greater total crack lengths in both the maxilla and the mandible (maxilla: mean difference, 18.70 ± 7.04 µm/mm(2); CI, 13.29-24.11; mandible: mean difference, 22.98 ± 6.43 µm/mm(2); CI, 18.04-27.93; P <0.05), higher crack surface density in both the maxilla and the mandible (maxilla: mean difference, 10.39 ± 9.16 µm/mm(2); CI, 3.34-17.43; mandible: mean difference, 11.28 ± 3.41 µm/mm(2); CI, 8.65-13.90; P <0.05). CONCLUSIONS: This study demonstrated greater microdamage in the cortical bones of adult hounds in both the maxilla and the mandible by the self-drilling insertion technique compared with the self-tapping technique.

Bone damage associated with orthodontic placement of miniscrew implants in an animal model.

INTRODUCTION: The purposes of this study were to quantify bone damage associated with insertion of 2 types of miniscrew implants and to relate the amount of bone damage to monocortical plate thickness. METHODS: Nondrilling (n = 28) and self-drilling (n = 28) miniscrew implants (6 × 1.6 mm, Dentaurum, Newtown, Pa), and pilot holes (n = 26) were placed bilaterally in the maxillae and the mandibles of 5 adult dogs immediately after death. Bone blocks were cut, bulk stained with 1% basic fuchsin, embedded in methyl methacrylate, sectioned, and mounted. Monocortical plate thickness was measured adjacent to the miniscrew implant insertion site. Damage amounts were quantified at distances of 0 to 0.5 mm (adjacent region) and 0.5 to 1 mm (distant region) from the bone-implant interface. Total fractional damaged area (%), fractional microcracked area (%), and fractional diffuse damaged area (%) were quantified by using standard histomorphometric methods. RESULTS: The mean monocortical plate thickness of the specimens from the mandible (2.2 mm) was significantly (P <0.001) greater than that of the maxillary specimens (0.9 mm). In the mandible, the 3 damage parameters were greater with self-drilling miniscrew implants than with nondrilling miniscrew implants; however, there were no differences in the damage parameters in the maxilla. CONCLUSIONS: Bone damage accumulation is related to the type of miniscrew implant and the thickness of the bone.

Regeneration of red bone marrow in rat lower jaw after transplantation of mesenchymal stem cells into the site of injury.

Regeneration processes in rat mandibular bone after transplantation of a suspension of autologous BM MSC in culture medium were studied by methods of light microscopy and X-ray densitometry. It was found that the structures of red BM in the callus after transplantation of autologous BM MSC formed earlier than in natural reparation. The formation of cavities containing BM determines lower tissue density at the site of injury after transplantation of autologous BM MSC on weeks 4 and 5 of observation than during spontaneous healing. These changes progressed throughout the observation period and attested to accelerated bone tissue reparation.

Biomechanical and microscopic response of bone to titanium implants in the presence of inorganic grafts.

This study evaluated the biomechanical and microscopic response of previously grafted bone to titanium implants. The lower incisors of 16 rabbits were surgically extracted, and bilateral perforations communicating with the remaining sockets were created distally. A socket/perforation defect on each mandible was chosen at random to be immediately filled with a xenogenic graft, whereas the contralateral perforation was left to heal naturally and served as a paired control. After 60 days, titanium implants were installed in the previously operated areas. After periods of 2 and 6 months, the animals were killed, and the force necessary to retrieve implants as well as the bone-implant contact (BIC) and bone mass (BM) were quantified and statistically compared by 2-way analysis of variance and Tukey's test (α  =  .05). No significant differences in removal torque were observed, either by time or by treatment condition. Differences in BIC and BM between experimental and control groups were not statistically significant through the intervals studied (P < .05). The presence of a xenogenic graft did not influence the microscopic tissue response to titanium implants or fixation into newly formed or mature bone.

Leukocyte-platelet rich fibrin on the treatment of a large paradental cyst: a novel regenerative approach.

Leukocyte-platelet rich fibrin (PRF) is an autologous biomaterial formed by platelets, cytokines, growth factors and cells imprisoned on a fibrin mesh, produced according to Choukroun's protocol. The aim of the present article was to report the use of PRF, associated with a bone substitute, on the regenerative treatment of a large bone defect resulting from the enucleation of a paradental cyst involving the posterior mandible. The treatment resulted in the maintenance of the bone volume, and radiographic evaluation showed new bone formation after 40 days, suggesting an osteogenic and osteoinductive effect. Also, the current literature was reviewed.

Local administration of HMGB-1 promotes bone regeneration on the critical-sized mandibular defects in rabbits.

Reconstruction of a critical-sized osseous defect is challenging in maxillofacial surgery. Despite novel treatments and advances in supportive therapies, severe complications including infection, nonunion, and malunion can still occur. Here, we aimed to assess the use of a beta-tricalcium phosphate (ß-TCP) scaffold loaded with high mobility group box-1 protein (HMGB-1) as a novel critical-sized bone defect treatment in rabbits. The study was performed on 15 specific pathogen-free New Zealand rabbits divided into three groups: Group A had an osseous defect filled with a ß-TCP scaffold loaded with phosphate-buffered saline (PBS) (100 µL/scaffold), the defect in group B was filled with recombinant human bone morphogenetic protein 2 (rhBMP-2) (10 µg/100 µL), and the defect in group C was loaded with HMGB-1 (10 µg/100 µL). Micro-computed tomography (CT) examination demonstrated that group C (HMGB-1) showed the highest new bone volume ratio, with a mean value of 66.5%, followed by the group B (rhBMP-2) (31.0%), and group A (Control) (7.1%). Histological examination of the HMGB-1 treated group showed a vast area covered by lamellar and woven bone surrounding the ß-TCP granule remnants. These results suggest that HMGB-1 could be an effective alternative molecule for bone regeneration in critical-sized mandibular bone defects.

Scanning electron microscopy analysis of experimental bone hacking trauma of the mandible.

The authors report on a macroscopic and microscopic study of human mandible bone lesions achieved by a single-blade knife and a hatchet. The aim of this work was to complete the previous data (scanning electron microscopy analysis of bone lesions made by a single-blade knife and a hatchet, on human femurs) and to compare the lesions of the femur with those of the mandible. The results indicate that the mandible is a more fragile bone, but the features observed on the mandible are quite similar to those previously observed on the femur. This work spells out the main scanning electron microscopy characteristics of sharp (bone cutting) and blunt (exerting a pressure on the bone) mechanisms on human bone. Weapon characteristics serve to explain all of these features.

[Comparative histomorphological analysis of bone fragments consolidation in compression and non-compression mandible osteosynthesis].

On experimentally produced model of mandible fractures (on 18 rabbits) the efficacy of compression osteosynthesis was compared with fixation by usual plates (non-compression osteosynthesis). As was shown by histological study and morphometrical analysis of tissue structures from the region of experimentally isolated in rabbit mandible bone fragments fixed by microdevices for compression and non-compression osteosynthesis in cases of compression osteosynthesis if compared with non-compression osteosynthesis at the experimental terms of 2, 3 and 4 months more intensive new formation and secondary rebuilding of bone tissue with its compactification in the region of cortical layer happened. Histological study and morphometrical analysis of histological pictures showed that reparative osteosynthesis processes were activated in cases of compression osteogenesis not only in cortical but also in sponge layer that together with contact enforcing of the edge of experimentally isolated bone fragment with maternal bone and bone splinters fixation strengthening stipulated for integral positive effect in the form of bone integrity restoration acceleration. In case of non-compression osteosynthesis the processes of reparative bone formation were observed mainly in cortical layer region, in sponge layers they were expressed poorly.

The effect of platelet-rich fibrin exudate addition to porous poly(lactic-co-glycolic acid) scaffold in bone healing: An in vivo study.

Bone grafting procedures have been widely utilized as the current state-of-the-art for bone regeneration, with autogenous bone graft being the gold-standard bone reconstructive option. However, the use of autografts may be limited by secondary donor-site comorbidities, a finite amount of donor supply, increased operating time, and healthcare cost impact. Synthetic materials, or alloplasts, such as the polymeric material, poly(lactic-co-glycolic acid) (PLGA) has previously been utilized as a transient scaffold to support healing of bone defects with the potential to locally delivery osteogenic additives. In this study a novel procedure was adopted to incorporate both the dissolved contents and mechanical components of leukocyte- and platelet-rich fibrin (L-PRF) into an PLGA scaffold through a two-step method: (a) extraction of the L-PRF membrane transudate with subsequent immersion of the PLGA scaffold in transudate followed by (b) delivering a fibrin gel as a low-viscosity component that subsequently polymerizes into a highly viscous, gel-like biological material within the pores of the PLGA scaffold. Two, ~0.40 cm3 , submandibular defects (n = 24) were created per side using rotary instrumentation under continuous irrigation in six sheep. Each site received a PLGA scaffold (Intra-Lock R&D, Boca Raton, FL), with one positive control (without L-PRF exudate addition [nL-PRF]), and one experimental (augmented with PLGA/L-PRF Blocks [L-PRF]). Animals were euthanized 6 weeks postoperatively and mandibles retrieved, en bloc, for histological analysis. Histomorphometric evaluation for bone regeneration was evaluated as bone area fraction occupancy (BAFO) within the region of interest of the cortical bone (with specific image analysis software) and data presented as mean values with the corresponding 95% confidence interval values. Qualitative evaluation of nondecalcified histologic sections revealed extensive bone formation for both groups, with substantially more bone regeneration for the L-PRF induced group relative nL-PRF group. Quantitative BAFO within the defect as function of the effect of L-PRF exudate on bone regeneration, demonstrated significantly (p = .018) higher values for the L-PRF group (38.26% ± 8.5%) relative to the nL-PRF group (~28% ± 4.0%). This in vivo study indicated that L-PRF exudate has an impact on the regeneration of bone when incorporated with the PLGA scaffold in a large translational model. Further studies are warranted in order to evaluate the L-PRF exudate added, as well as exploring the preparation methods, in order to facilitate bone regeneration.

Reconstruction of canine mandibular bone defects using a bone transport reconstruction plate.

OBJECTIVES: Reconstruction of mandibular segmental bone defects is a challenging task. This study tests a new device used for reconstructing mandibular defects based on the principle of bone transport distraction osteogenesis. METHODS: Thirteen beagle dogs were divided into control and experimental groups. In all animals, a 3-cm defect was created on one side of the mandible. In 8 control animals, the defect was stabilized with a reconstruction plate without further reconstruction and the animals were killed 2 to 3 months after surgery. The remaining 5 animals were reconstructed with a bone transport reconstruction plate, comprising a reconstruction plate with attached intraoral transport unit, and were killed after 1 month of consolidation. RESULTS: Clinical evaluation, cone-beam CT densitometry, three-dimensional histomorphometry, and docking site histology revealed significant new bone formation within the defect in the distracted group. CONCLUSION: The physical dimensions and architectural parameters of the new bone were comparable to the contralateral normal bone. Bone union at the docking site remains a problem.

[Bone defects of ramus mandibulae healing in rabbits under bioengineering constructions from titanium and gold alloy with xenogenic mesenchymal stem cells].

Aim of the study was substantiation in experiments on rabbit ramus mandibulae of the method of mesenchymal stem cells (MSC) on the carrier from titanium and gold alloy for reparative osteogenesis enforcement. There was shown stimulating action of the MSC implantation in the bone wound upon reparative osteogenesis at the terms from 1 to 4 months. It was concluded that implants from titanium and gold alloy may be used as carrier for MSC for bone tissue reparative regeneration stimulation.

[Regeneration processes in bone defects after implantation of composite material of different density of polylactide origin filled with HAP (experimental-morphological study)].

In experimental-morphological study on 6 dogs the dynamics of regenerate formation in ulna and mandible defects after implantation in them composite material of different density (0.46-0.50 and 0.38-0.42 g/cm(3)) of polylactide (PL) origin filled with HAP was followed at the terms of 6 and 9 months. Histologic study and structural determinant distribution analysis in the content of regenerate showed that optimal results according to the bone defect substitution by bone regenerate criterion at 9th month of the experiment were received after composite material from PL and HAP with the density of 0.38-0.42 g/cm(3) implantation. Newly formed trabecular bone tissue was seen in the regenerate and as well as strong tendency for bone matrix maturation. It was confirmed by the appearance of lamellar structures in newly formed bone trabecules situated in peripheral zones of bone defect. In bone mandible defects the substitution process of the implants from PL with HAP by the bone tissue was much slower than in ulna defects.