Bioabsorbable materials for guided bone regeneration prior to implant placement and 7-year follow-up: report of 14 cases

BACKGROUND: The purpose of the present study was to evaluate the efficacy of a guided bone regeneration (GBR) procedure prior to implant placement and the long-term outcome of the inserted implants. METHODS: Prior to dental implant placement, GBR procedure was performed on 14 patients (mean age 48 years) using a synthetic hydroxyapatite (HA) spacer under a collagen membrane. After a mean healing period of 8 months, bone biopsies were obtained during the placement of 14 implants. The specimens were processed for histology without demineralization in order to assess bone quality and quantity of the regenerated bone. RESULTS: Both the bone density and the resorption degree of HA particles were relatively varied between samples. The different phenotypes of osteoclasts and multinucleated giant cells and the individual host response could partially explain the unpredictable results in terms of bone remodeling and biomaterial resorption. However, the presence of HA particles in the regenerated bone had no influence on the osseointegration of implants presenting a success rate of 86% after a 7-year observation period. CONCLUSIONS: These results confirm the possibility of regenerating bone by means of bioabsorbable materials, assuring at the same time the long-term success for implants inserted in regenerated sites.     

Vertical ridge augmentation with guided bone regeneration in association with dental implants: an experimental study in dogs

AIM: To evaluate the effect of using guided bone regeneration (GBR) with a titanium-reinforced e-PTFE membrane in alveolar bone defects with titanium implants. MATERIAL AND METHODS: Following extraction of three mandibular premolars and a molar on both sides of the jaw in three dogs, alveolar bone defects (depth: 5-7 mm) were produced. After 4 months, three implants were inserted into each defect to a depth of approximately 4 mm, so that their coronal portion was protruding about 5 mm. Four sides in the dogs were assigned to a test group and the remaining two sides to a control group. The 12 implants in the test group were covered with a reinforced e-PTFE membrane. The space under the membrane was filled with peripheral venous blood from the animal, and the flaps were sutured over the membrane. The six control implants received no membrane before the suturing of the flaps to complete wound closure. The animals were sacrificed after 6 months, and non-decalcified histological specimens of the implants and surrounding tissues were prepared. RESULTS: Histologic and histomorphometric analyses revealed a significantly (Mann-Whitney test; P=0.08) larger amount of bone fill in the test group (mean=57.42%) than in the controls (mean=11.65%), and clinical evaluation of one test site showed that the implants were completely covered with tissue resembling bone. In most of the specimens, bone had grown in height close to, or in direct contact with the membrane. However, the new bone generally was not in direct contact with the implants. Regularly, a zone of dense connective tissue was interposed between the implants and the newly formed bone. CONCLUSION: The formation of even considerable amounts of bone following vertical ridge augmentation with GBR and implants was not accompanied by predictable osseointegration of the implants.     

牙髓干细胞的研究和应用展望

成体干细胞的研究在组织和器官修复再生中具有重要的意义。近年来，在现代细胞生物学、分子生物学和分子遗传学研究推动下，有关牙髓干细胞的来源、体外培养、细胞表型和功能等研究积极展开，本文将对其研究进展及在牙髓疾病和牙齿再生修复中的应用前景作一综述。     

Calvarial bone regeneration by a combination of natural anorganic bovine-derived hydroxyapatite matrix coupled with a synthetic cell-binding peptide (PepGen): an experimental study in rats

Objectives: The aim of this study was to evaluate histologically the effect of natural anorganic bovine‐derived hydroxyapatite matrix (ABM) coupled with a synthetic cell‐binding peptide on the healing of critical size calvarial defects in rats. Material and methods: Sixteen 4‐month‐old rats were used in the study. A 5 mm trephine defect was created in each parietal bone of every animal. One defect was left untreated (control) while the contralateral defect was treated with a natural ABM coupled with a synthetic cell‐binding peptide (test). At 60 and 120 days post‐operatively, groups of eight animals were sacrificed and 7–10‐μm‐thick decalcified sections were produced from both test and control sides. Three sections, 100 μm apart, representing the central area of each defect were selected for the histometric analysis. Results: Histological analysis showed limited bone formation in both control and test defects at both observation periods. The control defects healed with fibrous connective tissue occupying the midportion of the defect and minimal new bone formation at the periphery. In the test defects, the major part of the defect was occupied by graft particles embedded in connective tissue. After 60 days of healing the residual defects accounted up to 94.6% of the original defect dimensions in the control specimens and 90.6% in the test specimens. The differences between test and control defects were not statistically significant (P=0.06). After 120 days of healing, the residual defects accounted up 89.9% of the original defect dimensions in the control specimens and 85% in the test specimens. The difference was not statistically significant (P=0.33). Conclusion: The ABM coupled with a synthetic cell‐binding peptide failed to substantially promote new bone formation in rat calvarial defects.     

引导骨再生术对前牙区种植牙龈美学及牙槽骨吸收的影响

目的 了解前牙美学区种植位点存在骨缺损的患者行引导骨再生术（guided bone regeneration,GBR）在种植术后能否获得无明显骨缺损患者相近的牙龈美学效果,评价引导骨再生术对牙槽骨吸收的影响。方法 选取2017年8月—2018年6月间在中国科学技术大学附属第一医院（安徽省立医院）口腔医学中心行前牙种植术的患者31例,术前测量种植位点牙槽骨宽度,宽度小于6.8 mm的患者为GBR组,宽度大于6.8 mm患者为非GBR组,比较2组二期修复时牙龈美学评分、探诊深度及牙槽骨吸收的差异。采用SPSS 19.0软件包对数据进行两独立样本t检验。结果 GBR组牙龈美学评分显著高于非GBR组（P<0.01）,GBR组与非GBR组探诊深度无显著差异（P>0.05）,GBR组牙槽骨吸收显著小于非GBR组（P<0.01）。结论 使用GBR术可以减缓骨吸收速度,使存在局部牙槽骨缺损的患者达到无骨缺损患者牙种植术后的美学效果。     

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.     

人釉原蛋白真核表达载体体外表达产物生物学活性的检测

目的探讨人釉原蛋白基因重组质粒PcDNA3．1-AMG的真核细胞转染表达产物是否具有促进牙周组织再生的作用。方法脂质体介导PcDNA3．1-AMG体外转染COS1细胞．ELISA法检测转染细胞内及其培养上清液中重组釉原蛋白的表达：建立犬牙周组织缺损模型．局部使用转染表达产物冻干粉．8周后通过组织学观察牙周组织再生的情况。结果PcDNA3．1-AMG转染的COS1细胞内重组釉原蛋白浓度为（0．253±0．075）μg／ml。培养液中浓度为（0．065±0．011）μg／ml；使用转染表达产物8周后．牙周缺损区牙骨质、牙槽骨均有显著再生，并且新生牙骨质为有胶原纤维穿通的无细胞牙骨质。结论重组质粒PcDNA3．1－AMG在体外转染哺乳动物细胞后能够表达重组人釉原蛋白．并且表达产物具有促进牙周组织再生的生物学活性。     

Biologic interaction of three-dimensional periodontal fibroblast spheroids with collagen-based and synthetic membranes

Background: Cell‐based therapy using autologous cells has been suggested as a potential approach for periodontal tissue regeneration. Spheroid systems are a form of three‐dimensional cell culture that promotes cell matrix interaction, which could recapitulate the aspect of cell homeostasis in vivo. The aim of this study is to assess the interaction of periodontal fibroblast spheroids with synthetic and collagen‐based membranes that have been used in guided tissue regeneration. Methods: Commercially available normal human periodontal ligament fibroblasts were grown in spheroid forms using a liquid overlay technique and then transplanted onto a collagen‐based and a polyglycolic acid–based membrane. The biologic interaction of the spheroids with the membranes was assessed using basic histology, Alamar blue tissue viability assay, scanning electron microscopy, and immunohistochemical analysis. Results: Periodontal fibroblast spheroids adhered to both membranes, and the cells were able to proliferate and migrate from the spheroids both horizontally and vertically into the membrane scaffolds. Immunohistochemical analysis showed expression of collagen type I, periostin, and Runx2 by the periodontal fibroblasts. Conclusion: Periodontal fibroblast spheroids were able to grow three‐dimensionally on the biologic membranes and may have the potential to be used together with guided tissue regeneration approaches as an adjunct for periodontal regeneration.     

种植体周围炎导致骨缺损的再结合研究

目的探索种植体周围炎症所致骨缺损的治疗方法,从组织学角度评价治疗后种植体周围骨再生和再结合情况。方法Beagle犬5条,双侧下颌植入标准型Br nemark种植体30颗,建立种植体周围炎骨缺损模型,随机分组进行治疗(1)单纯去除种植体周围炎性肉芽组织;(2)植入不可吸收生物膜;(3)生物膜 骨粉植入;(4)生物膜 生物活性玻璃植入。采用X线和手术直接测量以及荧光标记组织切片和不脱钙硬组织切片,观察种植体周围骨量。采用SPSS12.0软件对数据作方差分析。结果直观测量种植体周围骨量、X线测量骨接触水平、组织学测量矿化沉积率,各组间有显著性差异,P<0.05。骨粉植入组,种植体周围能形成较多的新生骨。结论炎症导致的种植体周围骨缺损,可通过治疗手段达到缺损骨的再生。