| Objective A new type of composite artificial bone block was prepared by adsorbing biomimetically-precipitated nanocrystalline calcium phosphate powder hydrogel coating containing bone morphogenetic protein on the surface of 3D printed calcium-phosphate scaffold.To establish vertical bone defect model of Beagle dogs,and to evaluate the osteogenic effect of composite artificial bone block as bone graft material for vertical bone increment.To analyze the possibility of its application as bone graft material,and to provide a reference for further improving the synthetic block bone in order to develop a composite artificial bone block with bone induction and can replace autogenous bone for oral clinical vertical bone augmentation.Methods 1.Nanocrystalline calcium phosphate containing BMP-2(BMP-2/BpNcCap)was ground into biomimetic nanocrystal calcium phosphate powder with a diameter of 100 to 150μm,and hyaluronic acid containing biomimetic nanocrystal calcium phosphate powder suspension(HA/BMP-2/BpNcCap)was prepared by mixing BMP-2/BpNcCap powder with hyaluronic acid(HA).After low-speed shaking in the ultra-clean bench,the layered structure of the 3D printed calcium-phosphate scaffold was evenly coated with HA/BMP-2/BpNcCap coating after being placed at room temperature and dried so the composite artificial bone block was obtained.The composite artificial bone block was tested in vitro:the surface morphology and pore size were analyzed by scanning electron microscope(SEM),the porosity of scaffold and simulated body fluid absorptivity were measured.2.The mandibular premolar dentition defect model was established on the bilateral mandibular alveolar bone of 3 Beagle dogs,and the vertical bone defect model was established after 3 months of bone remodeling.Twelve bone defect sites were randomly divided into three groups:blank control group(group A),3D printed calcium-phosphate scaffold group(group B)and composite artificial bone block group(group C).The animals were killed 6 weeks after vertical bone increment.To observate of the operative area,analysis osteogenic parameters of Micro-CT scanning,and the hard tissue sections stained with MC Neal were used to evaluate the osteogenic effect of composite artificial bone block.Results 1.The surface morphology of 3D printed calcium-phosphorus scaffold was observed by scanning electron microscope(SEM):the surface of 3D printed calcium-phosphorus scaffold was(750.97±47)μm.The surface of composite artificial bone block was rough,which uniformly coated with HA/BMP-2/BpNcCap with a pore diameter of(258.78±27)μm.Porosity measurement:the porosity of 3D printed calcium-phosphorus scaffold was(52.50±2.39)%,and that of composite artificial bone block was(57.50±0.45)%.In the simulated body fluid environment,the performance of 3D printed calcium-phosphorus scaffold and composite artificial bone block is stable,and the space maintenance ability is good.It is expected that the scaffold material will collapse and soften due to body fluid infiltration after implantation in animals.2.Gross observation:3 Beagle dogs received antibiotics and analgesics after bone grafting,and they were in good general condition.One week after operation,among the 12 vertical bone defect sites,the mucosa of 10 sites healed well,the sutures of the remaining 2 bone augmentation sites partially fell off,and the implants were partially exposed,accompanied by mild soft tissue inflammation.The two sites were debrided and sutured.Three weeks after the operation,the soft tissue inflammation subsided.Six weeks after surgery,the beagles were in good general condition with good healing of the soft tissues in the mouth.3.Imaging observation:apical radiographs were taken immediately after surgery,and all bone graft materials were stable without rupture.At 6 weeks after operation,the apical radiograph showed complete high-density images of the scaffolds.There was no abnormal low-density image in the bone increment area.4.Six weeks later,Micro-CT scan was taken to analyze osteogenic parameters:Bone volume(BV),bone volume fraction(BV/TV),mean bone mineral density(BMD),trabecular junction density(Conn.D),trabecular number(Tb.N),trabecular thickness(Tb.Th).The BV of group A,B and C were(2.63±0.93)mm3,(11.92±1.17)mm3 and(88.21±4.37)mm3,respectively,and the difference was statistically significant(P<0.05).(BV/TV)were(0.01±0.003),(0.04±0.003)and(0.352±0.014),respectively,and the difference between group A and group B and C was statistically significant(P<0.05).There was no significant difference between groups A and B(P>0.05).BMD was(759.20±16.00)mg HA/cm3,(841.07±17.89)mg HA/cm3,(904.4319.23)mg HA/cm3,respectively,and the difference was statistically significant(P<0.05).Conn.Dwas(1.90±0.29)1/mm3,(4.91±0.32)1/mm3,(6.55±0.57)1/mm3,respectively,and the difference was statistically significant(P<0.05).Tb.N were(0.46±0.19)1/mm,(1.29±0.47)1/mm,(1.82±0.21)1/mm,respectively;Tb.Th were(0.18±0.04)mm,(0.24±0.04)mm,(0.39±0.05)mm,respectively.There were significant differences between A and C and between B and C(P<0.05).There was no significant difference between group A and B(P>0.05).5.MC Neal staining analysis:There was a small amount of new bone at the bottom of the original bone defect in group A,but no new bone formation was found in the buccal and lingual bone defect areas,while in group B,there was a small amount of new bone formation at the bottom of the stent,and no obvious new bone tissue was found in the buccal side,lingual side and the crown area protruding the original alveolar crest.In group C,a large number of new bone could be seen in the internal space of the stent,and a large number of new bone tissue could be seen in the coronal area,buccal area and lingual area of the original alveolar crest.The new bone adhesion rate on the pore surface of the scaffolds in group C was(41.72±4.23)%,(13.29±2.78)%and(40.99±6.68)%,which was significantly higher than that in group B(0.41±0.07)%,(0.11±0.04)%,and(0.33±0.07)%.The proportion of new bone area in the scaffold pores to the pore area in group C(57.41±11.01)%,(19.48±5.70)%and(54.75±10.01)%was significantly higher than that in group B(6.08±1.75)%,(1.13±0.45)%and(5.07±1.29)%,and the difference was statistically significant(P<0.05).Conclusion The biomimetic coating is uniformly adsorbed on the surface of 3D printed calcium-phosphorus scaffold to form a rough surface,and the composite artificial bone block has suitable porosity and pore size.The composite artificial bone block has good bone guidance and can maintain the spatial shape without collapse and deformation.The composite artificial bone block has significant osteoinductivity,especially in the bone defect without the support of the original bone wall,which can significantly promote the formation of new bone. |
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