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Bone tissue engineering: treatment of cranial bone defects in rabbits using self-reinforced poly-L,D-lactide 96/4 sheets.

This study is one of a series in which the authors evaluate various absorbable sheets to guide bone regeneration in cranial bone defects. The aim was to evaluate the use of self-reinforced poly-L,D-lactide 96/4 (SR-PLA96) sheets for cranial bone tissue engineering in experimental defects in rabbits. Square defects of 10 x 10 mm were created in the right parietal bone. SR-PLA96 implants (15 x 15 mm) were used to cover these defects in 12 New Zealand White rabbits. Similar defects were created in the left parietal bone, but no sheets were used (controls). The rabbits were killed after 6, 24, or 48 weeks. Histology and histomorphometry were used to evaluate healing of the defects. Defects covered with SR-PLA96 sheets showed more abundant bone formation than control (non-covered) defects. At 6 weeks, the defects were occupied mainly by fibrous tissue. At 24 weeks, healing with bone formation was more obvious in the covered defects. At 48 weeks, bone completely bridged defects covered with SR-PLA96 sheets, and incomplete bridging was seen in non-covered control defects. Hence, bone tissue engineering in experimental cranial bone defects in rabbits can be achieved using SR-PLA96 sheets to guide bone regeneration.

Absorbable Implants↗

[Experimental study on bioglass application in extending alveolar bone crest in rabbit].

OBJECTIVE: To observe the effect of Bioglass guiding bone regeneration and forming normal new bone in extending alveolar bone crest by surgery. METHODS: Thirty-six rabbits were randomly divided into three groups. The first group was treated with Bioglass and the second with hudroxyapectite (HA). The third group was control group. At 4 8 12 weeks after surgery, the condition of bone regeneration was observed with radiological and pathological methods. RESULTS: Statistical analysis showed that there was a significant difference between the third group and the other two groups (P<0.05). In addition, Bioglass can guide bone regeneration faster than hydroxyapatite, and it can be substituted by new bone to form completely normal bone. CONCLUSION: Since Bioglass is more effective than HA in guiding bone regeneration, it is an ideal bone graft substitute.

English Abstract↗

Role of a new member of IGFBP superfamily, IGFBP-rP10, in proliferation and differentiation of osteoblastic cells.

Bone regeneration is critically regulated by various molecules. To identify the new genes involved in bone regeneration, we performed microarray-based gene expression analysis using a mouse bone regeneration model. We identified a new member of the IGFBP superfamily, designated IGFBP-rP10, whose expression is up-regulated at the early phase of bone regeneration. IGFBP-rP10 consists of an IGFBP homologous domain followed by a Kazal-type protein inhibitor domain and an immunoglobulin G-like domain. A real-time-based RT-PCR analysis demonstrated that various tissues including bone expressed IGFBP-rP10 mRNA in various degrees, and confirmed an up-regulation at the early phase of bone regeneration. In situ hybridization revealed that osteoblastic cells expressed IGFPB-rP10 mRNA during bone regeneration. Bone morphogenetic protein-2 increased the expression level of IGFBP-rP10 mRNA in various cells including C3H10T1/2, MC3T3-E1, C2C12, and primary murine osteoblastic cells. The addition of recombinant mouse IGFBP-rP10 promoted the proliferation of these cells but failed to stimulate alkaline phosphatase activity. These results suggest that IGFBP-rP10 is involved in the proliferation of osteoblasts during bone formation and bone regeneration.

Amino Acid Sequence↗

Controlled subperiosteal tissue expansion to facilitate GBR for the placement of endosseous dental implants.

The success of endosseous dental implants is enhanced when sufficient bone is present to stabilize the implant. If adequate bone for full coverage of the implant is not possible, then the use of guided bone regeneration to regenerate the missing bone has been shown to be a predictable solution. Defect size can often limit the amount of soft tissue available for coverage of the membrane, which is essential in obtaining an optimal result when using regenerative and osseointegrative principles. The treatment philosophy demonstrated in this case report uses controlled subperiosteal tissue expansion to facilitate the incorporation of guided bone regeneration with the subsequent placement of endosseous dental implants. This treatment modality provided a successful treatment for an otherwise compromised case.

Adult↗

The quantification of bone tissue regeneration after electromagnetic stimulation.

In this study a titanium implant, the bone harvest chamber (BHC), was used to evaluate the effect of electromagnetic stimulation on osteogenesis. The BHC was inserted with a minimum of surgical trauma in the proximal tibial metaphysis in six adult lop-eared rabbits. Bone anchorage occurred after 4 weeks. After implant incorporation bone tissue was harvested at 3-week intervals with the implant in situ without killing the animal. The regenerated bone tissue was analysed by means of microradiography and densitometry. A test group and a control group each comprised six rabbits. The test group was stimulated with a 72-Hz electromagnetic field. Bone tissue was harvested from each tibia six times during the stimulation time and twice after the stimulation had been turned off. The control group had the same harvest procedure performed from one leg. Results showed that electromagnetic stimulation can maintain constant high osteogenetic activity. After the electromagnetic stimulation was turned off the osteogenetic activity diminished rapidly and osteogenesis was significantly lower than during stimulation.

Animals↗

[Experiment study of guiding bone tissue regeneration by frozen homologous periosteum].

OBJECTIVE: Explores the feasibility of guiding bone tissue regeneration by frozen homologous periosteum. METHODS: Rabbit's cranial periosteum was taken and refrigerated. In thirty-one white Japanese big ear rabbits, defects of the mandible were created. Defect at one side was covered with the membrane, another side not. The rabbits were sacrificed on four, eight, twelve, sixteen weeks. Specimens were examined by naked eye, X-ray, and histology. RESULTS: The frozen homologous periosteummet the requirement of guiding bone tissue regeneration There was no rejection, and could be kept 8 for 12 weeks in the body. It had the favorable efficacy of obstructing the fiber tissue from filling into bone defects and had an efficacy of guiding bone tissue regeneration. CONCLUSIONS: Frozen homologous periosteum is a perfect guiding bone tissue regeneration membrane.

Animals↗

Healing of bone defects in combination with immediate implants using the membrane technique.

Twenty Brånemark implants were placed with membranes (Gore-Tex Augmentation Material) as immediate or delayed implants in the extraction sockets of 15 patients. Membrane perforations through the mucous membrane occurred in 10 patients after 6 to 24 weeks and once after 2 weeks. Histologic examination of 15 tissue samples taken when the membrane was removed showed genuine bone regeneration in three patients, connective tissue regeneration with intermittent bone regeneration in eight patients, purely fibrous healing in two patients, and inflammatory granulation tissue in two patients. The high proportion of membrane perforations with immediate implants should be taken into account in the assessment and clinical application of this therapy principle.

Alveolar Process↗

[Future and needs of regenerative therapy in prosthetic treatment].

Bone regeneration is currently considered to be most significant in implantology as regenerative therapy is directly involved and essential in dental prosthetics. The following factors, however, must be clarified before prosthetic treatment can be performed; 1. Necessity of bone regeneration and recovery with individual method. 2. Change of regenerated bone. 3. Analysis of dynamics which will affect bone resorption. Though these factors are important in prosthetics, dynamic analysis is not performed well even in the existing bone. Clinical follow-ups so far indicate that not only infection but also excessive loading influence most of the cases whose progress is not good. Moreover, there are many challenges to be solved for bone generated by regenerative therapy such as the timing of placing the implant, the timing of loading, conditions for loading and occlusal control.

Bone Regeneration↗

Rigid fixation by means of titanium mesh in edentulous ridge expansion for horizontal ridge augmentation in the maxilla.

The edentulous ridge expansion has been introduced in recent years to reestablish an appropriate alveolar ridge width. This technique consists of the placement of implants in the space formed after the dislocation of the buccal plate in a labial direction. In guided bone regeneration, the quantity of bone regenerated under the membranes has been demonstrated to be directly related to the amount of the space under the membranes. This space can diminish as a result of membrane collapse. To avoid this problem, a new technique of edentulous ridge expansion, which involved the use of a titanium mesh barrier to protect the regenerating tissues and to achieve a rigid fixation of the bone segments, was used in association with autologous bone in 25 patients. At second-stage surgery in all patients, it was possible to see tissue, under the mesh, that had the macroscopic characteristics of mature bone and was superficially covered by a thin soft tissue layer. The microscopic examination showed that all autologous bone particles were embedded in newly formed bone. The use of a rigid mesh can assist bone regeneration in non-space-making defects, since it probably does not interfere with the blood flow to the underlying tissues because of the presence of microholes within the mesh.

Adult↗

The paradoxes in patterns and mechanism of bone marrow regeneration after irradiation. 1. Different volumes and doses.

Bone marrow regeneration (BMR) following irradiation has been largely studied as a dose-effect phenomenon, however, a large literature has simultaneously developed utilizing a wide variety of volumes, both in clinical studies and in experimental studies. In human situations radiation treatment fields and the amount of bone marrow organ exposed have ranged from total body irradiation (small daily and total doses) to large field (half-body) single high doses encompassing 50% of the bone marrow, to segmental or localized field (50-25%). Volume factors, more than dose, determine patterns of suppression and regeneration which have been documented by a variety of assay systems. Experimental evidence is presented which indicates that high dose irradiation (500-1000 cGy) to large volumes of bone marrow (50%) does not completely suppress bone marrow regeneration but results in a rapid compensatory response. The nadir response of bone marrow CFUc-GM stem cell compartment was directly proportional to increasing doses of irradiation (200-2000 cGy) delivered to a single limb. Immediate depression of CFUc-GM was followed by an increase proliferative phase with the most notable difference observed in doses less than or greater than 1000 rad. Following doses of 500 and 1000 rad to large field (half-body), an immediate depression was again observed followed by an immediate and greater compensatory response particularly after the 1000 rad dose. Comparisons ae made between the small and larger volumes at similar doses and indicate a greater overall compensatory response after the larger field irradiation, being more rapid in onset particularly after the 1000 rad dose. Although in-field regeneration of bone marrow occurs after single dose radiation to different volumes of bone marrow, experimental and clinical evidence from protracted conventional doses of irradiation to different volumes of bone marrow (greater or less than 50%) indicate significantly different response mechanisms. From our laboratory and clinical investigations it can be determined that bone marrow is extremely sensitive to radiation insult and has different compensatory mechanisms to "fine tune" its response in proportion to the volume insulted.

Animals↗

Prognostic factors for alveolar regeneration: effect of space provision.

OBJECTIVES: The role of space provision as an independent prognostic factor for periodontal regeneration remains to be established. The objective of this study was to evaluate the role of space provision on alveolar bone regeneration in periodontal sites. METHODS: Critical size, supra-alveolar, periodontal defects were created in 11 young adult Beagle dogs. Six animals received a porous ePTFE device to provide for space provision. Five animals received sham surgery. The animals were euthanized at 8 weeks post-surgery. A histometric analysis assessed vertical regeneration of alveolar bone and the width of the alveolar crest at the base of the defect. Because of the correlation of within-dog measurements, a mixed model anova/ancova was used to analyse the data. RESULTS: A significant relationship between the width of the alveolar crest at the base of the defect and bone regeneration was observed with no significant difference between sites receiving the different treatments (p=0.84). Bone regeneration at sites treated with the space-providing device was significantly greater compared with that at sites treated with sham surgery (p=0.0003), and the difference remained significant after adjusting for bone width (p=0.0001). CONCLUSIONS: Space provision has a significant effect on alveolar bone regeneration in periodontal sites. The width of the alveolar bone appears to influence space provision effectively supporting bone regeneration.

Alveolar Bone Loss↗

[Critical look at the use of osseous grafts in the treatment of periodontal disease].

Many types of materials are available for the regeneration of the periodontium destroyed by periodontal disease. In view of the fact that there are not many properly structured classical studies relative to the same, one cannot conclude that these materials regenerate bone, the periodontal ligament and the cementum which make up the periodontium. In this article, many classical studies relative to the use of bone grafts are carefully examined and analyzed.

Alveolar Bone Loss↗

[Surface reactivity of enosseous implanted bio-glass ceramics at varying lengths of implantation].

Chemical and structural surface changes at enosseous bioglass-ceramic-implants (Ap 40) were investigated by means of electron microprobe after an implantation period of 4 to 52 weeks. An intimate bonding between regenerated bone and bioglass-ceramic surface was evident at points already after 4 weeks. Initial degradation processes at implant surface came to a standstill after 12th week. A calcium and phosphorus rich layer of great importance for implant stability and biocompatibility was formed immediately contacting the bone. This surface layer had a thickness of nearly 25 micrometers -- 30 micrometers at 12 weeks and remains unchanged up to 52 weeks. The registered calcium and phosphorus impulse rate (cps) is equal to that of neighbouring bone. Chemical similarity of implant surface makes bioglass-ceramic Ap 40 a suitable biomaterial for durable bone replacement.

Animals↗