磷酸钙/聚乳酸羟基乙酸复合骨水泥对破骨前体细胞炎症因子表达的影响

目的观察磷酸钙/聚乳酸羟基乙酸复合骨水泥(CPC/PLGA)对破骨前体细胞炎症因子TNF-α、IL-1、IL-6表达的影响,了解PLGA促进CPC降解的机理。方法 1根据高效液相色谱法检测出的乳酸、羟基乙酸浓度配置CPC/PLGA替代液。2将RAW264.7细胞分别培养在DMEM培养基(对照组),第6小时CPC初凝块浸提液(A组)及CPC/PLGA替代液(B组)。通过CCK-8法检测各组细胞的增殖变化,并通过RT-PCR法检测各组中TNF-α、IL-1、IL-6 mRNA的表达情况。结果增殖实验结果示,A组细胞的增殖率在5 d时达到最高值(1.01±0.02),而B组细胞的增殖率在5 d时达到最高值(1.07±0.02),均与对照组相比有统计学意义(P<0.05)。RT-PCR法示A组和B组细胞TNF-αmRNA、IL-1 mRNA在6 h时表达最高,IL-6mRNA在12 h时表达最高,与对照组比较均有统计学差异(P<0.05)。结论磷酸钙/聚乳酸羟基乙酸复合骨水泥调控破骨前体细胞炎症因子增高。     

Development of a nonrigid, durable calcium phosphate cement for use in periodontal bone repair

BACKGROUND: Calcium phosphate cement (CPC) hardens in situ to form hydroxyapatite and has been used in dental and craniofacial restorative applications. However, when CPC was used in periodontal osseous repair, tooth mobility resulted in the fracture and exfoliation of the brittle CPC implant. The objective of the authors' study was to develop a strong and nonrigid CPC to provide compliance for tooth mobility without fracturing the implant. METHODS: The authors used tetracalcium phosphate, dicalcium phosphate anhydrous and biopolymer chitosan to develop a strong and nonrigid CPC. They used a powder:liquid ratio of 2:1, compared with the 1:1 ratio of a previously developed nonrigid CPC control. Specimens were characterized using a flexural test, scanning electron microscopy and powder X-ray diffraction. RESULTS: After 28 days of immersion, the new cement had a flexural strength (mean +/- standard deviation; n = 6) of 5.2 +/- 1.0 megapascals, higher than 1.8 +/- 1.5 MPa for the control (P < .05) and overlapping the reported strengths of sintered hydroxyapatite implants and cancellous bone. This cement showed a high ductility with a strain at peak load of 6.5 +/- 1.3 percent, compared with 4.4 +/- 1.9 percent for the control; both were 20-fold higher than the 0.2 percent of the conventional CPC. Nanosized hydroxyapatite crystals, similar to those in teeth and bones, were formed in the cements. CONCLUSIONS: The new nonrigid cement, containing nanohydroxyapatite crystals, possessed a high ductility and superior fracture resistance. This strong, tough and nonrigid CPC may be useful in periodontal repair to provide compliance for tooth mobility without fracture. CLINICAL IMPLICATIONS: The results of this study may yield the first self-hardening and nonrigid hydroxyapatite composite with high strength and durability and large deformation capability to be useful in the regeneration of periodontal osseous defects.     

Injectable calcium phosphate cement as a filler for bone defects around oral implants: an experimental study in goats

The aim of this study was to evaluate the clinical applicability and biological behavior of a newly developed injectable calcium phosphate (Ca-P) cement as bone filler for gaps around oral implants. Twenty-four step-like implants, creating gaps of 1 and 2 mm, were inserted into the trabecular bone of the medial femoral condyles of six goats. Four different situations were tested: (1) implant + gaps; (2) implant + gaps, but covered with a polylactic acid membrane; (3) implant + gaps that were filled with Ca-P cement; and (4) implant + gaps that were filled with Ca-P cement and covered with a membrane. All implants were left in place for 12 weeks. Histological and quantitative histomorphometrical measurements demonstrated that implants + gaps had generally poor bone contact at the implant base. Furthermore, fibrous encapsulation was observed in the gap part. In contrast, the presence of a membrane promoted bone ingrowth into the gap and also the bone contact at the implant base. Injection of Ca-P cement resulted in an almost complete filling of the gaps around the implant. The cement surface was completely covered by bone. Active resorption and remodeling of cement particles was observed, suggesting a pattern of slow resorption associated with full replacement with newly formed bone. Additional use of a membrane did not result in adjunctive benefits. Bone-to-implant contact at the implant base was comparable with the implants provided only with a membrane. In conclusion, the Ca-P cement used here showed excellent clinical handling properties combined with a superior bone behavior. On the other hand, the degradation rate of the material was still very slow. This current characteristic can hamper the final clinical applicability of the material as gap filler for periimplant or periodontal defects.     

Periodontal repair in dogs: evaluation of a bioresorbable calcium phosphate cement (Ceredex) as a carrier for rhBMP-2

BACKGROUND: Recombinant human bone morphogenetic protein-2 (rhBMP-2) has been shown to induce clinically relevant bone formation for orthopedic, craniofacial, and oral indications. It appears critical, in particular for onlay indications, that the associated carrier technology exhibits structural integrity to offset compressive forces in support of rhBMP-2-induced bone formation. The objective of this study was to evaluate a calcium phosphate (CP) cement, Ceredex, as a candidate carrier for rhBMP-2 in a defect model with limited osteogenic potential. MATERIALS: Bilateral, critical size, 6-mm, supra-alveolar, periodontal defects were created in six, adult, male, Hound Labrador mongrels. Three animals received rhBMP-2/Ceredex (rhBMP-2 at 0.20 and 0.40 mg/ml) in contralateral defect sites (implant volume/defect approximately 1 ml). One defect site in each of the three remaining animals received Ceredex without rhBMP-2 (control). The animals were euthanized at 12 weeks postsurgery for histologic and histometric analysis. RESULTS: Mean induced bone height exceeded 80% of the defect height for supra-alveolar periodontal defects receiving rhBMP-2/Ceredex without major differences between rhBMP-2 concentrations compared with approximately 40% for the control. The newly formed bone, a mixture of lamellar and woven bone in fibrovascular tissue, circumscribed relatively large portions of the residual Ceredex biomaterial. Inflammatory lesions were associated with limited bone formation in some sites. From a periodontal perspective, sites receiving rhBMP-2/Ceredex exhibited increased cementum formation compared with control, but without a functionally oriented periodontal ligament, and increased ankylosis and root resorption. Control sites exhibited early wound failure and exposure, loss of the Ceredex biomaterial, and limited bone formation. CONCLUSIONS: The Ceredex CP cement appears a potentially promising carrier technology for rhBMP-2 onlay indications. However, a slow resorption rate may prevent its wider use. This study does not support use of the rhBMP-2/Ceredex combination for periodontal indications.     

Repair of bone defects around dental implants with bone morphogenetic protein/fibroblast growth factor‐loaded porous calcium phosphate cement: a pilot study in a canine model

Objectives: To study the effects of the bone morphogenetic protein‐2 (BMP‐2)/fibroblast growth factor (bFGF)‐loaded porous calcium phosphate cement (CPC) on the repair of bone defects around dental implants. Material and methods: Thirty critical‐sized bone defects in beagle dogs were repaired with engineered bone composed of autologous bone‐marrow‐derived mesenchymal stem cells (BMSCs), BMP‐2, bFGF and CPC. Repairs were divided into six groups: BMSC/BMP‐2/bFGF/CPC, BMSC/BMP‐2/CPC, BMSC/bFGF/CPC, BMSC/CPC, CPC and no treatment. Polychrome sequential fluorescent labels were also performed post‐operatively. Fluorescence histological examinations of undecalcified sections at post‐operative week 12 were performed to clarify changes in the new bone around the dental implants. Results: The animals exhibited a perfect post‐operative course, with none experiencing any infection. Undecalcified sections showed that new bone was actively formed in the BMP‐2/bFGF group after 12 weeks. The bone mineralization apposition rate was better in the BMP‐2/bFGF group than in the other groups (P<0.05). Conclusion: BMP‐2 and bFGF together are more effective than either one alone in promoting the formation of new bone and may exert a synergistic activity at bone defects around dental implants. To cite this article:
Wang L, Zou D, Zhang S, Zhao J, K Pan, Huang Y. Repair of bone defects around dental implants with bone morphogenetic protein/fibroblast growth factor‐loaded porous calcium phosphate cement: a pilot study in a canine model.
Clin. Oral Impl. Res. 22 , 2011; 173–181.
doi: 10.1111/j.1600‐0501.2010.01976.x     

Histomorphometric assessment of bone formation in sinus augmentation utilizing a combination of autogenous and hydroxyapatite/biphasic tricalcium phosphate graft materials: at 6 and 9 months in humans

Objective: The aim of this study was to examine the efficacy of a new biphasic hydroxyapatite/tricalcium phosphate (HA/TCP) bone substitute in combination with particulate autogenous bone in sinus floor augmentation procedures.
Material and methods: A simultaneous or a two-stage sinus augmentation and implant placement were conducted in 28 patients. A mixture of HA/TCP and autogenous bone chips in a 1 : 1 ratio was used as the grafting biomaterial. Cylindrical specimen bone retrieval was performed in all patients except one. Specimens were harvested either at 6 ( n =14) or 9 ( n =13) months post-augmentation. For histologic and histomorphometric evaluations, the non-decalcified tissue processing (Donath's technique) was performed.
Results: Newly formed bone around the grafted particles was found in all samples. The encircling, highly cellular bone followed the outline of the grafted particles in direct contact. Both woven and lamellar types of bone were observed.
Morphometrically, the total mean bone area fraction of all sections was 34.8±10.3%, increasing from 28.6±7.8% at 6 months to 41.6±8.3% at 9 months ( P <0.001). Mean particle area fraction average was 25.5±11.6% and 23.5±9.3% at 6 and 9 months, respectively, with a total mean of 24.5±10.4%. The increase in bone area fraction was not significantly correlated to the decrease of the grafted particles area fraction.
Conclusions: The biphasic HA/TCP showed biocompatible and osteoconductive properties. This alloplast as a composite with autogenous bone chips promotes newly formed bone, which increases in its fraction along an extended healing period.