Simultaneously constructing nanotopographical and chemical cues in 3D-printed polylactic acid scaffolds to promote bone regeneration.

Topographical structures and bioactive surface coatings are effective in improving the biological function for bone regeneration. However, the simultaneous introduction of these benefits into three-dimensional (3D) porous scaffolds poses a daunting challenge. In this study, we proposed a simple yet effective approach to decorate 3D-printed polylactic acid (PLA) scaffolds with chemically modified nanotopographical patterns. The nanotopography was produced by etching the amorphous phase of PLA in an alcohol/alkali solution to expose dense lamellae. Subsequently, conformal decoration of polydopamine (PDA) was realized via self-assembly of catecholamines without changing the surface nanotopography. In vitro cell experiments including live and dead staining, cell morphology, cell growth, and alkaline phosphatase showed that the combination of nanotopography and PDA-coating led to a favorable enhancement of osteoblasts adhesion, spread and proliferation in 3D-printed scaffolds. The contribution of integrated patterns to bone regeneration was evaluated using a rat femur critical-sized defect model in vivo. Micro-CT evaluation and histological analysis demonstrated that the scaffold decorated with integrated pattens promoted osteogenesis more than the bare scaffolds and the scaffolds decorated with only nanotopography. Our proposed approach offers a promising method for improving bioactivity of 3D polymer scaffolds for bone tissue regeneration.

Role of HA and BG in engineering poly(ε-caprolactone) porous scaffolds for accelerating cranial bone regeneration.

Effects of varied bioactive fillers on the biological behavior of porous polymer/inorganic composite scaffolds are lack of comprehensive comparison and remain elusive. Moreover, composite scaffolds with high porosity suffer from inferior mechanical performance. Herein, high-pressure molding and salt leaching were employed to prepare poly(ε-caprolactone) (PCL) composite porous scaffolds loaded with hydroxyapatite (HA) and bioactive glass (BG), respectively. Structural analysis indicated all the porous scaffolds presented interconnected open-pore structure with the porosity of ~87% and pore size of ~180 µm, hinging on the amounts and size of porogen. Compared to PCL/HA scaffolds, PCL/BG scaffolds showed ~2.3-fold augment in the water absorption. Attributing to the compact framework, the PCL/HA and PCL/BG porous scaffolds exhibited outstanding compressive modulus, which was notably higher than other PCL composite porous scaffolds reported in literatures. Cells culture results demonstrated that PCL/BG scaffolds displayed higher expression of osteogenic differentiation than PCL and PCL/HA scaffolds. Furthermore, in vivo results showed that more mature bone was formed within PCL/BG scaffolds than PCL/HA scaffolds, manifesting that the introduction of BG accelerated cranial bone regeneration to obtain complete bone healing within a short time. Therefore, these data indicate that PCL/BG scaffolds are more competitive for bone tissue engineering application. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 654-662, 2019.

Surgical repair of hard palate cleft with absorbable membrane: the new surgical technique and its clinical application.

This study evaluated a new surgical technique with absorbable membrane to repair hard palate cleft without extensive mobilisation of the mucoperiosteum. From 2001 to 2002, 32 selected patients with complete unilateral clefts underwent this surgical operation. The traditional flap surgical operation was performed at the soft palate, uvula and anterior alveolar cleft. The absorbable membrane was implanted to the hard palate cleft gap to guide the regeneration of the mucoperiosteum. The patients were followed up for 1-6 months after the operation. The speech assessment was carried out 12 months after the operation. Of 32 patients, 30 were successfully operated by this method and no obvious complications occurred. Primary healing on tissue defect of hard palate was obtained in 27 patients and secondary healing in 3 patients. Eighty percent of the 30 patients had good or excellent speech 12 months after the operation. The operation failed in 2 patients. The surgical technique with absorbable membrane to repair hard palate appears to have several valuable advantages including the decreased area of the hard palate involved and favourable outcome for speech in the majority of cases.

Effect of nerve growth factor and Schwann cells on axon regeneration of distracted inferior alveolar nerve following mandibular lengthening.

OBJECTIVE: To study the effect of nerve growth factor (NGF) and Schwann cells on axon regeneration of the inferior alveolar nerve following mandibular lengthening with distraction osteogenesis. METHODS: Unilateral mandibular osteodistraction was performed in 9 healthy adult male goats with a distraction rate of 1 mm/d. Every 3 goats were killed on days 7, 14 and 28 after mandibular lengthening, respectively. The inferior alveolar nerves in the distraction callus were harvested and processed for ultrastructural and NGF immunohistochemical study. The inferior alveolar nerves from the contralateral side were used as controls. RESULTS: On day 7 after distraction, axon degeneration and Schwann cell proliferation were observed, and very strong staining of NGF in the distracted nerve was detected. On day 14 after distraction, axon regeneration and remyelination were easily observed, and NGF expression started to decline. On day 28 after distraction, the gray scale of NGF immunoreactivity recovered to the normal value and the Schwann cells almost recovered to their normal state. CONCLUSIONS: Gradual mandibular osteodistraction can result in mild or moderate axon degeneration of the inferior alveolar nerve. Nerve trauma may stimulate the proliferation of Schwann cells and promote the synthesis and secretion of NGF in the Schwann cells. Schwann cells and NGF might play important roles in axon regeneration of the injured inferior alveolar nerve following mandibular lengthening.

Correction of mandibular deficiency by inverted-L osteotomy of ramus and iliac crest bone grafting.

This study was to describe the use of inverted-L osteotomy of ramus and iliac bone graft for the management of mandibular deficiency in adult patients. From 2008 to 2010, 11 patients (aged 19 to 29 years) with mandibular deficiency underwent intraoral or extraoral inverted-L osteotomy of ramus and iliac crest bone grafting. Data were collected from the patients' records, photographs and radiographs. The height and width of the ramus were successfully expanded by inverted-L osteotomy and iliac crest bone grafting with minimal complications in all patients, resulting in significant improvement in occlusion and facial appearance. Our early results showed that the inverted-L osteotomy of ramus and iliac crest bone grafting is safe and effective, and should be considered as a good alternative for the patients with mandibular deficiency.

[Narrowing and sliding genioplasty procedure combined with mandibular outer cortex ostectomy technique to correct square jaw in short face].

OBJECTIVE: To evaluate the the feasibility and effectiveness of narrowing and sliding genioplasty combined with mandibular outer cortex ostectomy technique to reshape a square jaw in short face. METHODS: From July 2005 to October 2009, a total of 57 patients received narrowing and sliding genioplasty combined with mandibular outer cortex ostectomy procedure to correct square jaw in short face. All the patients had standard frontal and lateral cephalometric radiographs, panoramic radiographs, and were photographed preoperatively and postoperatively to assess their face contour. The alteration of mandibular angle, mental contour and width of lower face was observed for 6 to 24 months postoperatively. Questionnaires were used to assess the patients' satisfactory. RESULTS: It showed that the postoperative lower face had narrowed and become softer, slender and oval, with a slick mental region. The final aesthetic outcomes were quite satisfactory in all cases from both the view of surgeons and patients. CONCLUSIONS: Narrowing and sliding genioplasty combined with mandibular outer cortex ostectomy procedure could efficiently adjust the shape and position of chin to obtain a good proportion of the lower face, and to change square and short face to slender oval one by single operation in accordance with the fashionable aesthetics in orientals.

[Reconstruction of critical sized calvarial defects by porous nano-hydroxyapatite/polyamide 6 composite with bone marrow mesenchymal stem cells in rat].

OBJECTIVE: To evaluate the effects of the nano-hydroxyapatite/polyamide 6 (n-HA/PA6) on the proliferation and osteoblastic differentiation of rat bone marrow mesenchymal stem cells (BMSCs), and the feasibility of using both for constructing tissue engineered bone in the calvarias of rats with critical sized defects. METHODS: The third passage of BMSCs were cultured in osteoblastic medium and seeded on the scaffolds of n-HA/PA6, the proliferation of the BMSCs was tested by MTT (3-{4,5-dimethylthiazol-2yl}-2,5-diphenyl-2H-tetrazolium-bromide) on scheduled dates, and the osteoblastic differentiation of the BMSCs were measured by alkaline phosphatase (ALP) staining. Furthermore, the scaffolds with or without BMSCs in rat calvarial defects, after 4 weeks, 8 weeks, and 16 weeks have been implanted. Histology and scanning electron microscope were used to test the bone healing in the different groups. RESULTS: The BMSCs seeded on the n-HA/PA6 grew well, the proliferation of cells was not affected by the scaffold, and the staining of ALP was also positive. At 4 week and 8 week after implantation, the n-HA/PA6 with BMSCs showed more new bone formation on the surface of scaffolds, with a better osseointegration of implant and host bone when compared with the group of n-HA/PA6 without BMSCs. However, there was no significant difference between these two groups at 16 week. CONCLUSION: The porous n-HA/PA6 has no negative effects on the proliferation and osteoblastic differentiation of rat BMSCs, and using BMSCs as seed cells and n-HA/PA6 as scaffolds is a good choice for constructing tissue engineered bone due to the enhanced new bone formation and osseointegration.

Growth of the mandible after condylar reconstruction using transport distraction osteogenesis: an experimental investigation in goats.

BACKGROUND: Mandibular condyle damage during childhood disturbs mandibular growth and facial skeletal development. Transport distraction osteogenesis provides a new treatment for condyle reconstruction, but there are no data available on mandibular growth in growing individuals following surgery. The authors investigated the effect of condylar reconstruction by transport distraction osteogenesis on mandibular growth in goats. METHODS: A condylar defect was created unilaterally in 44 growing goats. The animals were divided randomly into group A (n = 22) and group B (n = 22). Transport distraction was used to reconstruct the condyles in group A, whereas group B served as sham controls. Three-dimensional computed tomographic imaging was performed at different intervals. Ten animals from each group were used for mandibular growth measurements at 48 weeks after the end of distraction. Four animals from each group were euthanized at 12, 24, and 48 weeks after surgery. Their transport disks were harvested and processed for histologic evaluation. RESULTS: In group A, the hemimandible of the distracted side exhibited similarities to the contralateral side except for the larger neocondyles. In group B, ramus height and width were significantly shorter on the undistracted side than on the contralateral side; concomitantly, there was mandibular deviation to the operated side. Well-organized fibrocartilage was seen at the neocondylar surface over time in group A but not in group B. CONCLUSIONS: This study suggests that a neocondyle reconstructed by means of transport distraction has the potential to grow under functional stimuli of the temporomandibular joint. Therefore, this technique may serve as an alternative method for condylar reconstruction in growing individuals.

[Study of reconstruction of mandibular condyle by transport distraction osteogenesis in monkeys].

OBJECTIVE: To evaluate the applicability and effectiveness of reconstruction of mandibular condyle by transport distraction osteogenesis in an animal model of rhesus monkeys. METHODS: Six adult rhesus monkeys were used in this study. Bilateral condyles and articular discs were extirpated, and the technique of transport distraction osteogenesis was performed to reconstruct the condyle. X-ray and CT scanning films were taken at various intervals. Two monkeys selected at random were sacrificed respectively at 4, 12 and 24 weeks after completion of distraction, and the newly formed condyles resulted from bony transport disc were harvested and processed for histologic examination. The removed condyles at surgery were used as normal control and prepared in the same manner. RESULTS: Open bite was seen in all animals postoperatively, and disappeared at the end of distraction. The shape and appearance of the bony transport disc was similar to original condyles at sacrifice. The articular cavity was filled with fibrous connective tissue and considerable cartilage cells were observed in the surface of the condyle stump. Bone regeneration was perfect in the distraction gap. CONCLUSION: A neocondyle with functional shape can be created by transport distraction osteogenesis, which suggested that this technique might be an alternative method in reconstruction of the condyle.

[Quantitative histomorphometric observation of distraction osteogenesis during mandibular lengthening].

PURPOSE: To evaluate the regenerating bone during mandibular distraction osteogenesis by bone histomorphometry combining tetracycline bone labeling fluorescence microscopy. METHODS: Osteotomy was performed on bilateral mandibles in ten goats. A custom-made distractor was applied to lengthen the mandible at a rate of 1 mm/d (0.5 mm/12 hrs) for ten days. Every two animals were sacrificed at 10 d, 15 d, 25 d, 35 d and 45 d postoperatively. Two additional goats were used as normal control. The bony specimens were collected and prepared for bone histomorphometry and tetracycline bone labeling fluorescence microscopy with analysis of variance. RESULTS: From 10 days subgroup to 45 days subgroup, bone volume fraction,trabecular thickness,trabecular number and volume density were gradually increased (P<0.05), while trabecular separation distance and surface density were gradually decreased (P<0.05). Between 15 days subgroup and 45 days subgroup,the index of osteoblast was significantly higher than normal control (P<0.05) and index of osteoclast was increased gradually (P<0.05). Compared with normal control, bone formation rate was accelerated by thousand times between 15 days subgroup and 45 days subgroup (P<0.05). CONCLUSIONS: During the process of mandibular distraction osteogenesis, the bone formation is active, the newly formed bone trabecula gradually become mature, and the remodeling activities of regenerated bone are enhanced gradually. The rate of bone formation within distraction period is faster than consolidation period.

[Mode of new bone formation following distraction osteogenesis in mandibular lengthening].

OBJECTIVE: To investigate the mode and influential factor of new bone formation following distraction osteogenesis in mandibular lengthening. METHODS: Corticotomy was performed on bilateral mandibles in twelve adult male goats. A custom-made distractor was used to lengthen the mandible at a rate of 1 mm/day for 10 days (total 10 mm elongation). Four goats were sampled respectively at 2, 4 and 8 weeks after completion of distraction. The lengthening mandibles were examined by roentgenography and histology. RESULTS: Newly formed callus was observed in the distraction gap after mandibular lengthening. The new bone exhibited intramembranous ossification generally, but cartilage islands could be found in the specimen that distractor loosed. CONCLUSION: The above findings indicate that the mode of new bone formation in mandibular lengthening following distraction osteogenesis appears to be intramembranous ossification and that endochondral ossification takes place in case distractor has loosened.

[Expression of vascular endothelial growth factor during mandibular distraction osteogenesis in rabbits].

OBJECTIVE: To investigate the expression pattern of vascular endothelial growth factor (VEGF) in the distracted callus during mandibular osteodistraction. METHODS: Bilateral mandibular osteotomies were performed in 12 rabbits. 3 rabbits were sacrificed respectively at 0, 7, 14 and 28 days after completion of distraction. The newly formed calluses were harvested and processed for histology and immunohistochemistry of VEGF. RESULTS: Intense angiogenesis was observed in the regenerated callus after mandibular lengthening, and positive staining for VEGF was mainly noted in vascular endothelial cells and the active osteoblasts. CONCLUSIONS: Mechanical strain created by distraction led to angiogenesis in distraction gap. VEGF may play a critical role in angiogenesis and subsequent osteogenesis during mandibular lengthening.

[Recombinant human BMP-2 accelerates bone formation of mandibular distraction osteogenesis in rabbits].

OBJECTIVE: To study the effects of rhBMP-2 on bone formation of mandibular distraction osteogenesis in rabbits. METHODS: Bilateral mandibular osteotomies were performed in 12 mature rabbits. 5 mg rhBMP-2 with the collagen carrier was implanted in the osteotomy site of one side of the mandibles. Only the collagen sponge was placed in the contra-lateral side as control. The mandibles of 8 rabbits were lengthened by 6mm using a custom-made distractor. At 4 weeks after the end of distraction, all animals were killed and the distracted calluses were harvested and processed for histological, scanning electron microscopic, as well as Ca/P ratio analysis. RESULTS: The regenerated bone was found in the distraction gap after mandibular lengthening. The mandibular side treated with rhBMP-2 had greater amounts of new bone formation and earlier mineralization than contra-lateral side (non-rhBMP-2 treated). CONCLUSION: Recombinant human BMP-2 appears to be able to accelerate bone formation of mandibular distraction osteogenesis in rabbits.