核素骨显像评价组织工程骨修复骨缺损效果的价值

目的 应用放射性核素骨显像评价组织工程骨修复兔股骨髁骨缺损的效果。方法 取人白兔15只，抽取骨髓，行骨髓间充质干细胞分离、培养、骨向诱导。双侧股骨髁制作0．6×1．2cm的骨缺损，将诱导的成骨细胞复合珊瑚羟基磷灰石植入左侧，右侧单纯植入羟基磷灰石为对照组。术后4间、8周和12周分别行静态核素骨显像评价骨缺损的修复能力。结果表明术后4、8、12周实验组ROI计数（单位像素）均较对照组有显著性增高（P〈0．001）。实验组ROI计数随时间的延长呈明显的上升趋势，但术后8周始增长放缓；对照组ROI也有卜升趋势，但术后8周始增长加快，均在12周达到峰值。结论 骨髓间充质干细胞诱导后复合珊瑚羟基磷灰石可有效的修复股骨髁松质骨缺损。放射性核素骨显像在骨修复过程中具有动态评价血管化和骨生长的作用。     

复合抗肿瘤珊瑚羟基磷灰石人工骨的体内成骨

背景：复合抗肿瘤珊瑚羟基磷灰石人工骨在体内外有良好的缓释效果及抗肿瘤作用,但由于其所复合药物量较大,植入体内骨缺损处较高的局部药物浓度是否影响骨的正常诱导、传导及生长？ 目的：建立复合抗肿瘤珊瑚羟基磷灰石人工骨成骨模型,进一步分析复合抗肿瘤珊瑚羟基磷灰石人工骨的体内成骨效应及规律。 方法：分别将珊瑚羟基磷灰石人工骨及复合抗肿瘤珊瑚羟基磷灰石人工骨植入兔股骨两干骺端骨缺损模型,定期观察股骨X射线影像,并取材行组织病理切片,观察材料降解和被新骨替代的速度、骨与材料界面的结合情况,材料内部新骨生长情况。 结果与结论：珊瑚羟基磷灰石人工骨植入后与周围骨形成组织及骨桥连接较复合抗肿瘤珊瑚羟基磷灰石人工骨快,植入4周后X射线片影像及组织切片示珊瑚羟基磷灰石人工骨边缘开始逐渐不清,并逐步与动物骨形成骨愈合。复合抗肿瘤珊瑚羟基磷灰石人工骨植入后早期8周内局部以抑制组织细胞生长为主,6~12周逐渐有组织结构向材料孔隙内生长且逐渐出现成骨细胞、骨基质及骨细胞,新生骨逐渐生长替代融合,26周左右与周围骨形成骨愈合。说明复合抗肿瘤珊瑚羟基磷灰石人工骨植入早期虽对骨愈合有一定的抑制作用,但最终仍可自行与周围骨缺损达到骨愈合。     

多孔羟基磷灰石与富血小板血浆和纤维蛋白胶复合修复骨缺损

背景：自体骨移植是治疗骨缺损的最理想方法,但来源有限,供区有一定的并发症,所以寻找自体骨的替代材料一直是骨科学领域的研究方向。 目的：观察珊瑚多孔羟基磷灰石、富血小板血浆和纤维蛋白胶复合物修复骨缺损的效果。 方法：在新西兰大白兔双侧前臂桡骨中段截骨1.5 cm制成骨缺损模型,随机分为3组,实验组植入珊瑚多孔羟基磷灰石、富血小板血浆和纤维蛋白胶复合物,对照组植入自体骨,空白对照组未植入任何物质。 结果与结论：①X射线：实验组术后12周时骨缺损基本修复,塑性完全,愈合过程与对照组同步;空白对照组骨缺损无明显变化。②组织病理学：实验组与对照组术后12周时骨缺损基本修复,出现成熟板层骨及哈佛氏管;空白对照组仅见大量成纤维细胞增生,未见骨质形成。③生物力学：术后2周时实验组最大扭矩和抗扭刚度优于对照组(P < 0.05),术后12周时两组最大扭矩和抗扭刚度差异无显著性意义。表明珊瑚多孔羟基磷灰石、富血小板血浆和纤维蛋白胶复合物具有促骨质愈合的作用,甚至在术后早期修复骨缺损的效果优于自体骨。     

纳米双相陶瓷人工骨的成骨及降解

背景：烧结后的纳米羟基磷灰石结晶度很高,在体内很难降解;纳米β-磷酸三钙的降解速度太快,不利于体内生物组织在材料上附着,不利于引导成骨。 目的：观察纳米羟基磷灰石/纳米β-磷酸三钙双相陶瓷人工骨的成骨及降解性能。 方法：将36只青紫蓝兔随机分为实验组、对照组及空白组,制作左侧挠骨缺损模型,实验组与对照组分别植入纳米羟基磷灰石/纳米β-磷酸三钙双相陶瓷人工骨、纳米羟基磷灰石人工骨,空白组不植入任何材料。术后4,8,12周观察成骨和材料降解情况。 结果与结论：①术后12周时X射线：实验组可见材料基本降解,连续性骨痂通过骨缺损部位。对照组材料未见明显降解,骨缺损处有骨痂修复。空白组骨缺损未见修复。②术后12周时组织学观察：实验组材料孔隙内以骨细胞和成骨细胞为主,有少量软骨细胞,出现散乱的骨松质,材料完全降解。对照组材料孔隙内以骨细胞为主,有少量成骨细胞和软骨细胞,材料未见明显降解。空白组可见纤维结缔组织及胶原纤维。③术后12周时扫描电镜观察：实验组材料降解,骨缺损部位被新生骨松质取代。对照组材料未见降解,骨缺损部位大都被新生骨松质取代。空白组无明显骨重建。表明纳米羟基磷灰石/纳米β-磷酸三钙双相陶瓷人工骨具有良好成骨能力及降解性能。     

自体红骨髓构建非细胞型组织工程化骨修复骨缺损**

背景：细胞型组织工程化骨修复骨缺损的效果良好,但存在操作复杂,容易污染及花费时间长等不足,不利于临床应用。 目的：观察自体红骨髓构建的非细胞型组织工程化骨修复大段骨缺损的成骨效果。 方法：在27只家兔一侧桡骨制作2 cm大段骨缺损模型后,随机分3组,分别植入自体红骨髓+重组人胰岛素样生长因子1/珊瑚羟基磷灰石非细胞型组织工程化骨、自体红骨髓/珊瑚羟基磷灰石复合人工骨材料、珊瑚羟基磷灰石/重组人胰岛素样生长因子1复合人工骨材料。 结果与结论：植入后4,8,12周,从植入物内部血管化程度、骨小梁数量、成熟骨结构形成及植入物的降解分析比较,自体红骨髓+重组人胰岛素样生长因子1/珊瑚羟基磷灰石非细胞型组织工程化骨组成骨能力及材料降解明显优于其他两组  (P < 0.05)。表明自体红骨髓构建的非细胞型组织工程化骨具有较高的成骨活性,修复大段骨缺损有显著效果。关键词：自体红骨髓;组织工程骨;重组人胰岛素样生长因子1;珊瑚羟基磷灰石;骨缺损;骨移植;扫描电镜 doi:10.3969/j.issn.1673-8225.2012.21.005     

可吸收珊瑚羟基磷灰石与天然珊瑚修复骨缺损的组织学及影像学分析

目的采用组织学及影像方法观察可吸收珊瑚羟基磷灰石与天然珊瑚修复骨缺损的牛物学特性。方法采集海南滨珊瑚，在一定的条件下珊瑚碳酸钙在“水热交换反应”转化成含羟基磷灰石80％的可吸收珊瑚人工骨（CHAP）。CHAP送国家材料实验室进行物理及化学检测。用40只新西兰大白兔，手术切除兔桡骨中段1．5cm，将长1.5cm、直径O.4cm的可吸收珊瑚羟基磷灰石植入骨缺损区，对照组植入天然珊瑚（Nc）。术后分批处死动物，拍X光照片，行组织学切片，对该人工骨的生物相容性和成骨效应进行了X线及组织学观察。结果珊瑚磨片片测得珊瑚孔道直径平均200Hm，孔隙率为51％。X光照片显示2周CHAP组织结构完整，NC组有少许吸收，4周时CHAP有大量外骨痂形成，NC组吸收明显，8周CHAP组与宿主骨完全愈合，NC组的移植材料大部吸收。术后2周可CHAP组有许多成纤维细胞和毛细血管长入珊瑚骨的微孔内，并有少量新生骨自接触部向珊瑚骨内爬行；天然珊瑚组孔道内为含新生骨的纤维结缔组织，内有炎性细胞浸润；4周时CHAP组有大量新生骨内含大量的毛细血管、成骨细胞及骨基质由周边深入珊瑚骨的中部，移植的人工骨面积无减少。NC组周边有新生骨形成，移植物面积减少（P〈O．001）;8周时CHAP组有大量成熟板层骨分布整个移植物的孔道内，部分骨组织内含有骨髓组织，人工骨有少量吸收。NC组在骨缺损未修复时移植物已大部吸收。结论通过对可吸收珊瑚羟基磷灰石材料与天然珊瑚材料体内植入的组织学及影像学分析比较，证实可吸收珊瑚羟基磷灰石是一种新制的可吸收骨组织移植替代材料，其理想的体内吸收速率与骨缺损修复的再生速率相吻合，作为骨缺损修复所必需的骨诱导活性是其独特的多孔结构所决定的，并具有良好的生物相容性和成骨潜能．     

载银珊瑚羟基磷灰石人工骨的机械性能及修复桡骨大段污染性骨缺损

背景：国内外学者在抗菌骨移植材料的基础实验和临床实践方面进行了大量的研究,取得了一定的进展。目的：通过体外力学实验检测抗菌性载银珊瑚羟基磷灰石人工骨的机械性能,并通过动物实验检测其修复大段污染性骨缺损的能力。方法：利用压缩试验及三点弯曲试验评价载银珊瑚羟基磷灰石、珊瑚羟基磷灰石与珊瑚的力学性能。将36只新西兰大白兔随机分为4组,均制作右侧大段污染性桡骨缺损模型,其中3组分别植入载银珊瑚羟基磷灰石、珊瑚羟基磷灰石与原位自体骨,另1组不植入任何材料(对照)。术后2,6,10周处死动物并取材,通过大体观察、影像学检查、组织学检查观察比较各组骨缺损修复情况,通过细菌学检查评估各组抗菌情况。结果与结论：载银珊瑚羟基磷灰石、珊瑚羟基磷灰石与珊瑚的力学性能无差异。术后10周时,X射线及组织学观察结果显示,载银珊瑚羟基磷灰石骨缺损内为成熟的骨组织,骨组织中有大量的骨陷窝和成熟的骨细胞,可见哈弗氏系统,材料大部分降解,只有少量残留,骨髓腔有部分再通,骨缺损修复效果与自体骨组相似,优于珊瑚羟基磷灰石组与对照组。细菌学检查显示载银珊瑚羟基磷灰石具有良好的抗菌能力。表明载银珊瑚羟基磷灰石具有较好的力学性能及抗菌性能,可用于修复大段污染性骨缺损。 中国组织工程研究杂志出版内容重点：生物材料;骨生物材料; 口腔生物材料; 纳米材料; 缓释材料; 材料相容性;组织工程     

珊瑚羟基磷灰石与异体脱细胞真皮基质联合修复牙根尖周组织缺损

背景：慢性根尖周炎症导致根尖周骨质破坏及缺损并不少见,若不能及时消除炎症终止骨吸收和牙龈组织的破坏,修复根尖周组织缺损,最终将导致牙丧失。脱细胞真皮基质和珊瑚羟基磷灰石在动物实验中常用于修复牙周损伤。目的：评价异体脱细胞真皮基质与珊瑚羟基磷灰石两种材料联合修复根尖周组织缺损的临床疗效。方法：选择76例慢性根尖周炎患者作为研究对象,患者等分为实验组和对照组。实验组患者采用异体脱细胞基质与珊瑚羟基磷灰石联合修复根尖周组织缺损;对照组患者不植入任何材料。2组患者均行根尖切除及根尖倒充。修复后1周及6,12个月复诊,通过临床症状和 X 射线片检查评价修复效果。结果与结论：修复1个月后,实验组患者异体脱细胞真皮基质全部存活,因修整瘘管口周围炎性的肉芽组织导致的牙龈组织缺损已经愈合。在修复12个月后,实验组患者的修复有效率明显高于对照组(P < 0.05)。实验组患者修复6个月后骨缺损区阴影基本消失,珊瑚羟基磷灰石颗粒间的透射影减小,出现有一定致密度的影像,提示有新骨长入;12个月后珊瑚羟基磷灰石颗粒密度已接近正常的骨组织密度,与正常骨组织之间有密度移行改变,逐渐与牙槽骨形成骨融合。异体脱细胞基质与珊瑚羟基磷灰石的生物相容性良好。提示异体脱细胞真皮基质与珊瑚羟基磷灰石联合修复根尖周组织缺损具有良好的临床疗效。中国组织工程研究杂志出版内容重点：生物材料;骨生物材料; 口腔生物材料; 纳米材料; 缓释材料; 材料相容性;组织工程全文链接：     

骨髓基质干细胞复合纳米材料修复骨缺损的微循环研究

目的:了解骨髓基质干细胞(MSCs)复合纳米羟基磷灰石/聚乳酸(n-HA/PLA)构建组织工程骨修复骨缺损过程中,实验动物血液流变学和骨缺损修复区血流量的变化。方法:选择20只新西兰白兔,制作15mm长的桡骨节段性骨缺损模型,根据植入不同移植材料分为实验组和对照组,实验组于动物左侧桡骨缺损区植入组织工程骨,对照组植入n-HA/PLA,观察各组动物术后1h、7天、14天血液流变学指标和术后14天骨缺损修复区血流量的变化。结果:实验组与对照组比较,血液流变学指标和骨缺损修复区血流量差异显著。组织工程骨修复骨缺损,实验动物血液粘度降低,骨缺损修复区局部血流量增加。结论:与单纯n-HA/PLA材料比较,组织工程骨可促进骨缺损的修复。     

可注射性纳米羟基磷灰石、壳聚糖复合材料修复骨缺损的实验研究

目的：观察可注射性羟基磷灰石/壳聚糖复合材料对兔桡骨骨缺损修复效果。方法：18只新西兰白兔双侧桡骨中段建立长度为10mm节段性缺损,将可注射性纳米羟基磷灰石/壳聚糖复合材料植入一侧骨缺损作为实验组,另一侧植入单纯羟基磷灰石材料作为对照组,于第4、8、12周末,分别行大体、X线检查、组织学、电镜检测,观察该材料对骨缺损的修复效果。结果：①大体观察、X线检查提示：实验组骨痂生长良好,骨缺损完全修复,对照组骨缺损部分修复,部分骨皮质不连续。②组织形态学: 术后12周,实验组新生骨皮质连接完整,髓腔完全再通;对照组少量新生骨形成,部分纤维组织填充③电镜检查:12周实验组材料基本降解,被新生骨组织替代。结论：可注射性纳米羟基磷灰石/壳聚糖复合材料骨缺损修复能力较单纯羟基磷灰石好,具有确实的骨缺损修复能力。     

Bone in-growth induced by biphasic calcium phosphate ceramic in femoral defect of dogs

Biphasic calcium phosphate (BCP) ceramics consisting of hydroxyapatite (HA) and tricalcium phosphate (TCP) has been used as a bone graft material during the last decade. In this paper, we report the bone in-growth induced by BCP ceramic in the experimentally created circular defects in the femur of dogs. This BCP ceramic consists of 55% hydroxyapatite (HA) and 45% b-tricalcium phosphate (TCP) prepared in situ by the microwave method. The defects were created as 4-mm holes on the lateral aspect of the femur of dogs and the holes were packed with the implant material. The defective sites were radiographed at a period of 4, 8, and 12 weeks postoperatively. The radiographical results showed that the process of ossification started after 4 weeks and the defect was completely filled with new woven bone after 12 weeks. Histological examination of the tissue showed the formation of osteoblast inducing the osteogenesis in the defect. The collageneous fibrous matrix and the complete Haversian system were observed after 12 weeks. The blood serum was collected postoperatively and biochemical assays for alkaline phosphatase activity were carried out. The measurement of alkaline phosphatase activity levels also correlated with the formation of osteoblast-like cells. This microwave-prepared BCP ceramic has proved to be a good biocompatible implant as well as osteoconductive and osteoinductive materials to fill bone defects.     

Correlation between hydroxyapatite osseointegration and Young's Modulus

From the standpoint of hard tissue response to implant materials, calcium phosphate is probably the most compatible of materials known. During the last few years, much attention has been paid to hydroxyapatite and beta-tricalcium phosphate as potential biomaterials for a bone substitute. Good implantation of biomaterials in the skeleton is evidenced by an ability to reach full integration of the non-living implant with living bone. The aim of this study is to correlate hydroxyapatite osseointegration with Young's Modulus. Cylinders (5-6 mm in diameter) of these ceramics were packed into holes made in the femur diaphysis of a mature sheep. At 2, 4, 8, 12, 16, 20, 28, 36 and 48 weeks after the operation, samples of the bone/implant interface were embedded in polymethylmethacrylate. We used the PIXE method (Particles Induced X-rays Emission) to measure the distribution of mineral elements (Ca, P, Sr, Zn, Mn and Fe) at the bone/implant interface. At 4, 8, 12, 16, 20, 28, 36 and 48 weeks after implantation we studied Young's Modulus on a biopsy of the ceramic. Young's Modulus increased with time after implantation and is linked with biomaterials integration into cortical bone.     

Bioactivity and osseointegration study of calcium phosphate ceramic of different chemical composition

Synthetic hydroxyapatite (HA) and tricalcium phosphate (TCP) are promising bone-substitute materials in the orthopaedic and dental fields, as their chemical composition is similar to that of bone. This study investigated the osseointegration performance of carbonated biphasic calcium phosphate (CBCP) ceramics containing carbonated hydroxyapatite and tricalcium phosphate prepared by microwave irradiation, in femoral defects of dogs. The defects were created as 3-mm holes on the lateral aspect of femur and filled with the implant material. The serum was collected postoperatively and biochemical assays for alkaline phosphatase activity levels were carried out. The animals' defective sites were radiographed at 4, 8, and 12 weeks. The radiographic results showed that the process of ossification started after 4 weeks and the defect was completely filled with new bone after 8 weeks. Histological examination of the tissue showed the osteoblastic activity inducing the osteogenesis in the defect. The complete haversian system with osteoblastic and osteoclastic activity and bone remodelling process were observed after 12 weeks. The alkaline phosphatase activity levels also correlated with the formation of osteoblast cells. This calcium phosphate ceramic has proved to work well as a biocompatible implant and as an osteoconductive and osteoinductive material for the filling of bone defects.     

Long-term implantation of zinc-releasing calcium phosphate ceramics in rabbit femora

Zinc is an essential trace element that has stimulatory effects on bone formation. Recently, we developed zinc-releasing calcium phosphate ceramics in order to add the pharmacologic effect of zinc to calcium phosphate ceramics. In our previous study, we showed that the optimum zinc content for promoting bone formation was 0.316 wt %. Therefore a zinc composite ceramic of zinc-containing beta-tricalcium phosphate and hydroxyapatite, with a zinc content of 0.316 wt %, was chosen for long-term implantation. Cylindrical rods of the zinc composite ceramic were implanted in rabbit femora for 2 to 60 weeks. Using computer-aided image analysis, a histomorphometric study was carried out to investigate bone formation and resorption around the implants. The control was a composite ceramic of beta-tricalcium phosphate and hydroxyapatite without zinc. The addition of zinc to the implant demonstrated both favorable and unfavorable effects on bone remodeling. The favorable effect was enhanced bone apposition to the implant surface, demonstrated by a significant increase in intramedullary bone apposition rate at 6 weeks and in cortical bone apposition rate at 24 and 60 weeks (p < 0.05). The unfavorable effect was increased bone resorption, demonstrated by a significant increase in medullary cavity area at 60 weeks (p < 0.05). In order to utilize the favorable effect and avoid the unfavorable effect of zinc, either a reduction in zinc content in the zinc composite ceramic or the selection of implantation sites that do not have excessive exposure to bone marrow are required.     

Micro-architecture of calcium phosphate granules and fibrin glue composites for bone tissue engineering

Calcium phosphate ceramics are currently used as bone graft substitutes in various types of clinical applications. Fibrin glue is also used in surgery due to its haemostatic, chemotactic and mitogenic properties. By combining these two biomaterials, new composite scaffolds were prepared. In this study, we attempt to analyse whether thrombin concentration in the fibrin glue could influence the properties of the composite. The association between fibrin glue and calcium phosphate ceramic granules was characterized at the ultra structural level. Micro and macroporous biphasic calcium phosphate ceramic granules with a diameter of 1-2mm composed of hydroxyapatite and beta-tricalcium phosphate (60/40) were associated to fibrin glue. The composites were observed by scanning and transmission electron microscopy and microcomputed tomography. Fibre thickness, porosity and homogeneity of the fibrin clot were modified by increased the thrombin concentration. Mixing fibrin glue with calcium phosphate granules (1:2) did not modify the microstructure of the fibrin clot in the composite. Nevertheless, thrombin interacted with the bioceramic by inducing the nucleation of crystalline precipitate at the ceramic/fibrin glue interface. Combining fibrin sealant and calcium phosphate ceramics could lead to new scaffolds for bone tissue engineering with the synergy of the properties of the two biomaterials.     

The material science of calcium phosphate ceramics

Tricalcium, tetracalcium phosphate and hydroxyapatite ceramics exhibit distinct differences in their chemical and structural composition. Only hydroxyapatite ceramic is identical with the original bone mineral. Different preparation methods lead to compact hydroxyapatite ceramic or to porous material with interconnecting macropores as structural equivalents of the spatial structure of cancellous bone. Concerning the behaviour in a biological environment, high crystallinity and large material density result in resistance to dissolution and long lasting stability. Amorphous ultrastructure and porous formation enhance interface activity and bone ingrowth, but also biological degradation of the ceramic implant material.     

Effect of sintered silicate-substituted hydroxyapatite on remodelling processes at the bone-implant interface

Phase pure, sintered granules of hydroxyapatite (HA) and silicon-substituted hydroxyapatite (Si-HA) were implanted for 6 and 12 weeks in an ovine model. Samples containing the bone-implant interface were prepared for ultramicrotomy and transmission electron microscopy (TEM) using an anhydrous sample preparation procedure. The results demonstrate that the morphology of apatite deposits and the sequence of events at the interfaces of bone with pure HA and with Si-HA implants, were different. Organised collagen fibrils were first found at the bone/Si-HA interface after 6 weeks, whereas they were found only after 12 weeks around the pure HA implant. Many more nodular aggregates comprised of plate-like apatite crystallites were observed in the vicinity of Si-HA than around the pure HA after 12 weeks in vivo. These findings suggest that the incorporation of silicate ions into HA promotes processes of bone remodelling at the bone/HA interface. TEM observations suggested that the trabecular bone weaves over the Si-HA and that the collagen fibrils form a mechanical interlock with the Si-HA ceramic implants. High-resolution lattice imaging illustrated apatite crystallites contiguous with the Si-HA ceramic and revealed a direct relationship between the bone mineral and the Si-HA ceramic.     

Development of calcium phosphate cement using chitosan and citric acid for bone substitute materials.

We developed a calcium phosphate cement that could be molded into any desired shape due to its chewing-gum-like consistency after mixing. The powder component of the cement consists of alpha-tricalcium phosphate and tetracalcium phosphate, which were made by decomposition of hydroxyapatite ceramic blocks. The liquid component consists of citric acid, chitosan and glucose solution. In this study, we used 20% citric acid (group 20) and 45% citric acid (group 45). The mechanical properties and biocompatibility of this new cement were investigated. The setting times of cements were 5.5 min, in group 20 and 6.4 min, in group 45. When incubated in physiological saline, the cements were transformed to hydroxyapatite at 3, and 6 weeks, the compressive strengths were 15.6 and 20.7 MPa, in group 45 and group 20, respectively. The inflammatory response around the cement implanted on the bone and in the subcutaneous tissue in rats was more prominent in group 45 than in group 20 at 1 week after surgery. After 4 weeks, the inflammation disappeared and the cement had bound to bone in both groups. These results indicate that this new calcium phosphate cement is a suitable bone substitute material and that the concentration of citric acid in the liquid component affects its mechanical properties and biocompatibility.     

Early stage mineralization in tissue engineering mapped by high resolution X-ray microdiffraction

The specific routes of biomineralization in nature are here explored using a tissue engineering approach in which bone is formed in porous ceramic constructs seeded with bone marrow stromal cells and implanted in vivo. Unlike previous studies this model system reproduces mammalian bone formation, here investigated at high temporal resolution. Different mineralization stages were monitored at different distances from the scaffold interface so that their spatial analysis corresponded to temporal monitoring of the bone growth and mineralization processes. The micrometer spatial resolution achieved by our diffraction technique ensured highly accurate reconstruction of the different temporal mineralization steps and provided some hints to the challenging issue of the mineral deposit first formed at the organic-mineral interface. Our results indicated that in the first stage of biomineralization organic tissue provides bioavailable calcium and phosphate ions, ensuring a constant reservoir of amorphous calcium phosphate (ACP) during hydroxyapatite (HA) nanocrystal formation. In this regard we suggest a new role of ACP in HA formation, with a continuous organic-mineral transition assisted by a dynamic pool of ACP. After HA nanocrystals formed, the scaffold and collagen act as templates for nanocrystal arrangement on the microscopic and nanometric scales, respectively.     

Bioreactions at the tissue/hydroxyapatite interface

The events at the hydroxyapatite implant material/tissue interface in the rat middle ear were studied by light microscopy, autoradiography, morphometry, transmission electron microscopy (TEM), scanning electron microscopy (SEM), and X-ray microanalysis. Deposition of calcium, partially in the form of calcium phosphate, was found at the interface. Resorption of the implant material occurred as the result of mono- and multinuclear phagocyte activity. Resorption decreased 6 mnth after the operation, possibly due to the decreasing number of phagocytes at the interface and the increasing amount of bone in the macropores.