Effects of occlusiveness of a titanium cap on bone generation beyond the skeletal envelope in the rabbit calvarium

We evaluate the effects of occlusiveness of a titanium cap on bone generation beyond the skeletal envelope. In eight rabbits, the calvarial bone was exposed and a circular groove was prepared with a trephine drill. After marrow penetration, a standardized hemispherical titanium cap, either with or without small holes (1.5 mm in diameter), was then placed into the bone and covered by a cutaneous flap. After 1 month or 3 months of healing, the animals were euthanized and examined histologically. The percentage area of newly generated tissue consisting of mineralized bone and marrow spaces in each section was calculated relative to the area bounded by the hemispherical shape of the titanium cap and the parent bone; this latter volume was taken to be 100%. Furthermore, the cross-sectional areas of generated mineralized bone expressed as percentages of the total tissue area generated within each space were determined. In the 1-month specimens, there was no statistically significant difference between the two caps in the amount of tissue generated, 54.7%+/-12.2% with holes vs. 60.4%+/-8.8% without holes (p=0.225). However, in the 3-month specimens, we observed a significant difference between the caps (55.9%+/-7.4% with holes vs. 89.9%+/-6.5% without holes, P<0.05). Also, there was a statistically significant difference between 1- and 3-month specimens in the amount of tissue generated under the cap without holes (60.4%+/-8.8% vs. 89.9%+/-6.5%, P<0.05). Although there was no significant difference in the relative amount of mineralized bone generated between the caps with holes and those without holes in the 1-month specimens (27.7%+/-4.8% vs. 30.8%+/-6.4%, P=0.225), there was a statistically significant difference between the two caps in the 3-month specimens (24.3%+/-4.1% with holes vs. 34.0%+/-8.6% without holes, P<0.05). A substantial ingrowth of fibrous connective tissue through the holes appeared to prevent further new tissue generation in a defined area adjacent to the bone surface. We concluded that total occlusiveness, sufficient stiffness of the cap, as well as the passage of time will allow predictable mineralized bone augmentation to occur in spaces beyond the skeletal envelope.     

Canine prostate stimulates osteoblast function using the endothelin receptors

BACKGROUND: Bone metastases are common in humans and dogs with late-stage prostate cancer. A unique feature of prostate cancer metastases is new bone formation at metastatic sites ("osteoblastic metastases"). Many carcinomas that metastasize to bone cause bone destruction, not new bone formation. The mechanisms by which prostate cancer induces bone formation at sites of bone metastasis are not well understood. We hypothesized that stimulation of osteoblasts by prostate tissue at metastatic sites was due to the paracrine actions of growth factors produced by prostate epithelial cells. METHODS: We have previously shown that normal canine prostate tissue induced new bone formation when implanted adjacent to the calvarium of nude mice. To complement this in vivo model, we developed an in vitro system of prostate-stimulated osteoblast function to investigate mechanisms of prostate-induced new bone formation. RESULTS: We found that treatment of cultured rat calvaria for 24 hr with proteins from normal dog prostate stimulated alkaline phosphatase activity in a dose-dependent manner 4-6 fold compared to controls. Stimulation began approximately 8 hr after treatment, and was diminished after 72 hr. Calvaria treated with homogenates of normal dog salivary gland, kidney, bladder, and muscle did not increase ALP activity. Pretreatment of the calvaria for 1 hr with endothelin antagonists, but not anti-parathyroid hormone-related protein (PTHrP) antibody or indomethacin, abrogated the stimulation of ALP. CONCLUSIONS: Our results indicated that osteoblast activation by canine prostate occurs via an endothelin-dependent mechanism, and that PTHrP or prostaglandin synthase-mediated pathways are likely not involved. This is a reliable, reproducible assay for determining the roles of molecules important in the activation of osteoblasts by the prostate.     

Multiple calvarial haemangiomas

Calvarial haemangiomas are rare benign tumours that may be suspected by their characteristic expansile ‘sunburst’ appearance. It is important to recognize them as such and to make the surgeon aware of haemorrhage after biopsy or resection.     

Extensive augmentation of the alveolar ridge using autogenous calvarial split bone grafts for dental rehabilitation

Free autogenous iliac bone is the most commonly used graft material for an extensive alveolar ridge reconstruction. The application of iliac bone, however, is associated with problems, such as transplant loss resulting from postoperative infection and late bone resorption. A bone-graft material more suitable than iliac bone is therefore still needed. This paper describes a concept for alveolar-ridge reconstruction using calvarial split bone, and the related surgical techniques. Clinical and radiological follow-up examinations were undertaken to evaluate the potential benefit of calvarial split bone in alveolar-ridge reconstruction. Between 1999 and 2002, 13 patients with a mean age of 54 years (range 31-70 years) underwent surgery, seven patients in the maxilla and six in the mandible. In four cases, wound dehiscence occurred postoperatively. In one of these cases, the dehiscence was associated with a local infection. However, no bone transplants were lost. After a mean follow-up time of 19.6 months, bone resorption, measured radiologically, was minimal. Endosseous dental implants were successfully installed and maintained. Satisfactory prosthetic rehabilitation was achieved in all patients. Our preliminary experience suggests that calvarial split bone may be regarded as a promising alternative to autogenous iliac bone in connection with extensive augmentation of the alveolar ridge.     

Long-term results of mandibular reconstruction with autogenous bone grafts and oral implants after tumor resection

Objectives: (a) To evaluate retrospectively the clinical outcome of non‐vascularized bone grafts used for the reconstruction of mandibular defects following tumor resection; (b) to evaluate the clinical outcome of implants and implant‐supported prostheses placed in the reconstructed areas; and (c) to evaluate patients' satisfaction regarding function and esthetics after oral rehabilitation. Material and methods: In a 9‐year period (1995–2003), 29 patients affected by mandibular tumors involving to tooth bearing areas were treated by means of tumor resection and immediate or delayed reconstruction with autogenous non‐revascularized calvarial or iliac bone grafts. Among these patients, 16 patients were selected for dental rehabilitation of the lost dentition with implant‐supported 3fixed prosthese333s. For to 7 months later, the patients received 60 oral implants for the prosthetic rehabilitation of the reconstructed edentulous areas. Results: No total failure of the graft was observed, while partial loss of the graft was observed in one patient. The mean follow‐up of patients after the start of prosthetic loading of implants treated was 94 months (range: 36–132 months). Two patients dropped out of the follow‐up after 3 and 4 years of observation, respectively. Two implants were removed due to loss of osseointegration, while two implants, although still integrated, presented peri‐implant bone resorption values higher than those proposed by Albrektsson et al. for successful implants. Cumulative survival and success rates of implants were 96.7% and 93.3%, respectively. Conclusion: Results from this study demonstrated that bone defects following resection of mandibular tumors can be predictably reconstructed with autogenous bone grafts taken from the calvarium or the anterior iliac crest. It has also been shown that the long‐term survival and success rates of implants placed in the reconstructed areas (96.7% and 93.3%, respectively) may guarantee an excellent prognosis of implant‐supported prostheses.     

Angiogenesis in newly augmented bone observed in rabbit calvarium using a titanium cap

Objectives: In our previous work using a rabbit experimental model, we identified the importance of using a rigid support device for augmenting the development of mineralized bone. In the early stage of healing, newly generated tissue has not filled occlusive spaces, and mineralized bone forms and tends to climb along the inner wall of a device. Even though the blood supply is critical for successful bone augmentation, few studies have been conducted on angiogenesis in augmented bone. The purpose of the present study was to evaluate a method for observing angiogenesis in newly augmented bone. Material and methods: The right and left sections of the calvarium of six adult male Japanese white rabbits were exposed. The cortical bone was penetrated, and custom‐made, standardized, hemispherical titanium caps were fixed to the exposed bone. The caps on the right side of each rabbit were filled with granulated β‐tricalcium phosphate (β‐TCP). After a healing period of 1 month, the animals were injected with MICROFIL^® into the right and left common carotid arteries to form a three‐dimensional cast of the vasculature, and the newly generated blood vessels in the augmented bone were observed. Results: The newly generated blood vessels were observed entering the space beyond the existing calvarial bone. Furthermore, angiogenesis was seen to have occurred to a similar extent through the inter‐granular β‐TCP in the right caps. These areas of angiogenesis were observed in a histological study with cross‐sections. Conclusions: The results of the present study suggest that this observation method allows the examination of angiogenesis in hard tissue before the preparation of histological specimens.     

染料木黄酮对大鼠颅盖骨骨吸收活性的作用

目的 :体外观察染料木黄酮 (genistein)对颅盖骨骨吸收活性的作用。方法 :分离乳鼠颅盖骨 ,分别加入 0、10 -8和 10 -6mol/L的染料木黄酮 ,并以 10 -9mol/L的 17β -雌二醇 (17βE2 )为对照 ,检测培养液上清中Ca2 + 含量和酸性磷酸酶活性 ,以评价染料木黄酮对颅盖骨骨吸收活性的作用。结果 :10 -8和 10 -6mol/L染料木黄酮使培养液上清中Ca2 + 含量下降 ,吸收指数 <1.0。 10 -9mol/L 17βE2 的吸收指数介于 10 -8与 10 -6mol/L染料木黄酮之间。酸性磷酸酶活性在各组之间无差异。结论 :染料木黄酮抑制大鼠器官培养中颅盖骨的骨吸收活性     

基于特征点抽取的闭合曲线快速检测法在颅盖骨图像中的应用

目的:探讨基于特征点抽取的闭合曲线快速检测法在颅盖骨图像中的应用效果。方法:将颅盖骨图像提取出来并进行细化处理后,从图论的观点出发,提取图中的端点、歧点和叉点,根据Euler公式计算图像中的边数和顶点数,由此判断颅盖骨是否闭合。结果:测试已明确诊断的61幅从第三脑室上部层面到大脑皮层下部层面的CT图像,结果有56幅判断正确,正确率为91.8%。结论:实验表明,此方法可以用来判断颅盖骨的闭合情况。