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The aim of this study was to histologically evaluate and compare the treatment of ligature-induced peri-implantitis using guided bone regeneration, two bone grafts alone, or guided bone regeneration combined with one of the two bone graft materials. Mandibular premolars and first molars in seven beagle dogs were extracted. After placement of Brånemark implants and connection of abutments, experimental peri-implantitis was induced. Flap surgery was performed, abutments were removed, and implant surfaces were treated with an air-powder abrasive unit. Bony defects were randomly treated with either (1) debridement only; (2) debridement plus resorbable hydroxyapatite; (3) debridement plus canine demineralized freeze-dried bone; (4) debridement plus guided bone regeneration; (5) debridement plus resorbable hydroxyapatite and guided bone regeneration; or (6) debridement plus canine demineralized freeze-dried bone and guided bone regeneration. Four months after surgery, a flap was elevated and the barriers were removed. One month later, the animals were sacrificed, and the implants with their supporting peri-implant tissues were processed for histologic evaluation. Guided bone regeneration procedures resulted in the greatest amount of new bone formation, followed by bone grafts alone, and flap debridement. There was no significant difference between guided bone regeneration and both guided bone regeneration/graft combinations in terms of bone regeneration; however, the guided bone regeneration/graft combinations resulted in a greater amount of "reosseointegration" than all of the other treatments. Therefore, the combination of guided bone regeneration with either demineralized freeze-dried bone or resorbable hydroxyapatite appears to be the treatment of choice for plaque-induced peri-implant defects.
The purpose of this study was to evaluate and compare the treatment of ligature-induced peri-implantitis using guided bone regeneration and two bone grafts alone and in combination. Mandibular premolars and first molars were extracted from four beagle dogs and after 3 months of healing, three Brånemark implants were placed on each side of the mandibles. Following abutment connection 3 months later, experimental peri-implantitis was induced by tying plaque-retentive ligatures around all abutments. Ligatures and abutments were removed after 3 months, and bony defects measured and treated with either: (1) debridement only; (2) debridement plus resorbable hydroxyapatite; (3) debridement plus canine freeze-dried demineralized bone; (4) debridement plus guided bone regeneration; (5) debridement plus resorbable hydroxyapatite and guided bone regeneration; or (6) debridement plus canine freeze-dried demineralized bone and guided bone regeneration. Pretreatment and 4-month-posttreatment comparison revealed a significant but variable degree of clinically appreciable hard tissue fill with all treatment procedures. Guided bone regeneration procedures resulted in the greatest fill, followed by bone grafts alone and flap debridement. There was no significant difference between guided bone regeneration and both guided bone regeneration/graft combinations; therefore, guided bone regeneration procedures appear to be a predictable treatment for plaque-induced peri-implant defects.
The goal of this study was to evaluate, morphometrically, hard-tissue healing following the treatment of ligature-induced peri-implantitis defects in dogs and guided bone regeneration and/or bone grafts. Five dogs were used, and the mandibular premolars were removed. Three months later, two titanium implants were installed on each side of the mandible, and after another 3 months, abutment connection was performed. Following abutment connection, experimental periimplantitis was induced by placing cotton ligatures in a submarginal position. Ligatures and abutments were removed after 1 month and the bony defects were randomly assigned to one of the following treatments: debridement (DE), debridement plus guided bone regeneration (GBR), debridement plus mineralized bone graft (BG), and debridement plus guided bone regeneration associated with mineralized bone graft (GBR/BG). The dogs were euthanatized after 5 months. Morphometric analysis did not reveal significant differences among the treatments neither with respect to the percentage of bone to implant contact (p = 0.996) nor to the bone area (p = 0.946) within the limits of the threads of the implant. Within the limits of this investigation, there is insufficient evidence to indicate that any of the treatments presented an improved response in dealing with bony defects resulting from peri-implantitis.
Guided bone regeneration is a new technique that evolved following the guided tissue regeneration procedure for regeneration of lost periodontium. The objective of guided bone regeneration is to promote bone formation in osseous deformities either before or in conjunction with endosseous implant placement. Osseous defects consist mainly of extraction sites, dehiscences or fenestrations, and localized ridge deformities. In addition, bone defects may either provide natural spacemaking or be nonspacemaking. A plethora of publications indicate that the guided bone regeneration technique can be used successfully in all types of defects. Nonspacemaking defects usually require bone graft materials to assist in space maintenance and enhance bone formation. Fixation pins are also used, either with or without graft materials, in this regard. The scientific literature on guided bone regeneration was reviewed by a task force to determine techniques proven to increase predictability relative to successful patient outcomes and to develop specific evidence based diagnostic and treatment decision trees.
Bone morphogenetic proteins (BMPs) are becoming increasingly recognised as valuable molecular tools for regenerating bone and accelerating fracture healing. New bone growth is the result of BMP-induced differentiation of pluripotent mesenchymal cells along osteoblastic pathways. This phenomenon recapitulates in adults specific aspects of skeletal morphogenesis co-ordinated by BMPs during development. An understanding of the basic scientific research which has led to the characterisation and purification of these remarkable molecules is essential if their full therapeutic potential is to be realised.
This study evaluated, by clinical analysis, the hard tissue response following treatment of ligature-induced peri-implantitis defects in 5 dogs. The mandibular premolars were removed from both sides of the jaw. After 3 months of healing, two titanium implants were placed on each side of the mandible. Following abutment connection, 3 months later, experimental peri-implantitis was induced by the placement of cotton ligatures in a submarginal position. Ligatures and abutments were removed after one month and the bony defects were randomly assigned to one of the following treatments: debridement (DE), debridement plus guided bone regeneration (GBR), debridement plus mineralized bone graft (BG) and debridement plus guided bone regeneration associated with mineralized bone graft (GBR + BG). The peri-implant bone defects were clinically measured before and 5 months post-treatment. Results showed a higher percentage of vertical bone fill for GBR + BG (27.77 +/- 14.07) followed by GBR (21.78 +/- 16.19), BG (21.26 +/- 6.87), DE (14.03 +/- 5.6). However, there were no statistically significant differences between any of the treatments proposed (one way repeated measures analysis of variance, P = 0.265).
The aim of the present systematic review was to assess the survival of implants in regenerated bone applying the method of guided bone regeneration (GBR) compared with the survival of implants in non-regenerated bone. Studies to be included in this review needed to provide at least 12-month results following prosthetic reconstruction of titanium implants in bone regenerated by GBR with or without membrane supporting materials. The outcome measures were implant survival described as presence of implant, implant success (according to the criteria in the respective study), absence of clinical implant mobility, absence of implant fracture, absence of progressive peri-implant crestal bone loss as assessed on radiographs without clinical signs of peri-implant infection, absence of peri-implant infection with suppuration. A MEDLINE search and a hand search of relevant scientific journals were conducted including studies from the year 1990 to May 2001. A total of 11 studies could be identified fulfilling the inclusion criteria. All studies except two had the characteristics of case series or cross-sectional surveys. The two different studies had both test and control implants included in their analysis and qualified as controlled clinical trials. Cumulative success or survival rates, respectively, for implants in regenerated bone ranged from 100% after 5 years to 79.4% after 5 years of function. Regarding survival data, no significant differences were found in the controlled clinical trials between implants in regenerated compared to implants in non-regenerated bone. Within the limits of this systematic review characterized by second and third levels of evidence, the following conclusions can be drawn: The survival rate of implants placed into sites with regenerated/augmented bone using barrier membranes varied between 79% and 100% with the majority of studies indicating more than 90% after at least one year of function. The survival rates obtained in the present systematic review are similar to those generally reported for implants placed conventionally into sites without the need for bone augmentation.
The present study describes the use of unbiased stereological methods for the quantitative evaluation of the amount of regenerated bone. Using the principle of guided bone regeneration the amount of regenerated bone after placement of degradable or non-degradable membranes covering defects in rabbit calvaria was compared. Forty rabbits were divided into 5 groups. A titanium microplate was placed over the defect to prevent collapse of the membrane. The non-degradable expanded polytetrafluoroethylene membrane and the degradable Polyglactin 910 material were both placed unicortically and bicortically. Undecalcified sections were prepared for stereologic evaluation after an observation period of 8 weeks. Complete bone healing of the defects was not observed in any of the specimens. Unbiased stereologic estimates revealed 48% bone regeneration in defects covered by 2 ePTFE membranes, and 12% in defects covered by 2 Polyglactin 910 membranes. Defects covered by 1 ePTFE or 1 Polyglactin 910 membranes revealed 10% or 18% bone regeneration, respectively. The control group regenerated 14%. The major difference of the estimates was caused by real difference between specimens, i.e. biologic variation, whereas only minimal variance was added by the stereologic estimation procedure.
Bone loss due to trauma or disease is an increasingly serious health problem. Current clinical treatments for critical-sized defects are problematic and often yield poor healing due to the complicated anatomy and physiology of bone tissue, as well as the limitations of medical technology. Bone tissue engineering offers a promising alternative strategy of healing severe bone injuries by utilizing the body's natural biological response to tissue damage in conjunction with engineering principles. Osteogenic cells, growth factors, and biomaterial scaffolds form the foundation of the many bone tissue engineering strategies employed to achieve repair and restoration of damaged tissue. An ideal biomaterial scaffold will provide mechanical support to an injured site and also deliver growth factors and cells into a defect to encourage tissue growth. Additionally, this biomaterial should degrade in a controlled manner without causing a significant inflammatory response. The following chapter highlights multiple strategies and the most recent advances in various areas of research for bone tissue regeneration.
Bone tissue is osteoconductive. In particular, cancellous bone with its porous and highly interconnected trabecular architecture allows easy ingrowth of surrounding tissues. When placed in an osseous environment, living tissue for the host bed migrates into the cancellous structure, which results in new bone formation and incorporation of that structure. This is the process of osteoconduction. The mineral and collagenous components of bone are osteoconductive. Osteoconduction also is observed in fabricated materials that have porosity similar to that of bone structure. Corallin ceramics, hydroxyapatite beads, and combinations of hydroxyapatite and collagen all have osteoconductive properties, and porous metals and biodegradable polymers. Osteoconduction appears to be optimized in devices that mimic not only bone structure, but also bone chemistry. The incorporation of calcium salts and collagen by osteoconductive matrices leads to more complete ingrowth with new bone formation.
Resorbable devices offer a significant technological advance for craniofacial surgery; however, the potential for their use may extend beyond that of bone fixation. Applications to assist bone regeneration and to secure bone grafts in cranial defects in the pediatric patient are presented.
Bone marrow contains a population of rare progenitor cells capable of differentiating into bone, cartilage, muscle, tendon, and other connective tissues. These cells, referred to as MSCs, can be purified and culture expanded from animals and humans. This review summarizes recent experimentation focused on characterizing the cellular aspects of osteogenic differentiation, and exploration of the potential for using autologous stem cell therapy to augment bone repair and regeneration. The authors have completed an array of preclinical studies showing the feasibility and efficacy of MSC based implants to heal large osseous defects. After confirming that syngeneic rat MSCs could heal a critical size segmental defect in the femur, it was established that human MSCs form bone of considerable mechanical integrity when implanted in an osseous defect in an immunocompromised animal. Furthermore, bone repair studies in dogs verify that the technology is transferable to large animals, and that the application of this technology to patients at geographically remote sites is feasible. These studies suggest that by combining MSCs with an appropriate delivery vehicle, it may be possible to offer patients new therapeutic options.
This article reviews the role of barrier membranes in guided tissue regeneration (GTR) and guided bone regeneration (GBR), including the advantages of using absorbable barrier membranes in GTR and GBR and the unique properties of collagen membranes. The indications and contraindications for using collagen membranes for these procedures are examined, and successful cases are presented. Finally, the role of collagen membranes in the future of regenerative therapy is considered.
When nonabsorbable membranes are used for guided bone regeneration (GBR), second surgeries are required for membrane retrieval. In addition, these types of membranes show a high incidence of flap sloughing and membrane exposure that often lead to infection and unfavorable results. Absorbable barriers such as collagen membranes were developed to overcome these drawbacks. This article presents the principles and the clinical procedure of using barrier membranes composed of absorbable collagen in GBR aimed at the repair and regeneration of ridge dehiscence defects around implants. The unique properties of collagen membranes that make them ideally suited to GBR procedures are reviewed. In addition, the indications and contraindications for using collagen membranes for GBR procedures are examined. Finally, cases are presented to demonstrate details of surgical principles and techniques.
UNLABELLED: Runx2 is prerequisite for the osteoblastic differentiation in vivo. To elucidate Runx2 gene functions in adult bone metabolism, we conducted bone marrow ablation in Runx2 heterozygous knockout mice and found that aged (but not young) adult Runx2 heterozygous knockout mice have reduced new bone formation capacity after bone marrow ablation. We also found that bone marrow cells from aged Runx2 heterozygous knockout mice have reduced ALP(+) colony-forming potential in vitro. This indicates that full Runx2 dosage is needed for the maintenance of osteoblastic activity in adult mice. INTRODUCTION: Null mutation of the Runx2 gene results in total loss of osteoblast differentiation, and heterozygous Runx2 deficiency causes cleidocranial dysplasia in humans and mice. However, Runx2 gene functions in adult bone metabolism are not known. We therefore examined the effects of Runx2 gene function in adult mice with heterozygous loss of the Runx2 gene. MATERIALS AND METHODS: Bone marrow ablation was conducted in young adult (2.5 +/- 0.5 months old) or aged adult (7.5 +/- 0.5 months old) Runx2 heterozygous knockout mice and wildtype (WT) littermates. Cancellous bone regeneration was evaluated by 2D microCT. RESULTS: Although new bone formation was observed after bone marrow ablation in the operated bone marrow cavity of WT mice, such bone formation was significantly reduced in Runx2 heterozygous knockout mice. Interestingly, this effect was observed specifically in aged but not young adult mice. Runx2 heterozygous deficiency in aged mice significantly reduced the number of alkaline phosphatase (ALP)(+) cell colonies in the bone marrow cell cultures, indicating a reduction in the numbers of osteoprogenitor cells. Such effects of heterozygous Runx2 deficiency on osteoblasts in vitro was specific to the cells from aged adult mice, and it was not observed in the cultures of marrow cells from young adult mice. CONCLUSION: These results indicate that full gene dosage of Runx2 is required for cancellous bone formation after bone marrow ablation in adult mice.
OBJECTIVES: There is a limited understanding of the effect of defect characteristics on alveolar bone healing. The objectives of this study were to assess the effect of alveolar bone width and space provision on bone regeneration at teeth and titanium implants, and to test the hypothesis that the regenerative potentials at teeth and implants are not significantly different. METHODS: Critical size, 5-6-mm, supra-alveolar, periodontal defects were surgically created in 10 young adult dogs. Similarly, critical size, 5-mm, supra-alveolar, peri-implant defects were created in four dogs. A space-providing expanded polytetrafluoroethylene device was implanted for guided tissue regeneration/guided bone regeneration. The animals were euthanized at 8 weeks postsurgery. Histometric analysis assessed alveolar bone regeneration (height) relative to space provision by the device and the width of the alveolar crest at the base of the defect. Statistical analysis used the linear mixed models. RESULTS: A significant correlation was found between bone width and wound area (r=0.55892, p<0.0001). Generally, bone width and wound area had statistically significant effects on the extent of bone regeneration (p<0.0005 and p<0.0001, respectively). Bone regeneration was linearly correlated with the bone width at periodontal (p<0.001) and implant (p=0.04) sites, and with the wound area at periodontal (p<0.0001) and implant (p=0.03) sites. The relationships of bone regeneration with these two variables were not significantly different between teeth and implants (bone width: p=0.83; wound area: p=0.09). When adjusted for wound area, bone regeneration was significantly greater at periodontal than at implant sites (p=0.047). CONCLUSIONS: The horizontal dimension of the alveolar bone influences space provision. Space provision and horizontal dimension of the alveolar bone appear to be important determinants of bone regeneration at teeth and implants. The extent of alveolar bone formation at implant sites is limited compared with that at periodontal sites.
Bone matrix contents various development factors which control structuring and absorption and those factors play important role in bone and cartilage development. Bone morphological proteins are members of TGF-beta super family and their activity is certain becoming from the bone. This activity leads to the serial development processes which include chemo taxis, proliferation and differentiation which results in trans resistant formation of cartilage as well as production of life cells of a bone tissue. Biological activities of re combinative human bone morphogenetic protein 7 (rhBMP-7). induction bone formation of non critical size mandible defect of New Zealand rabbits were researched in the study. Markers of osteoblastic differential in the study included ALP specific activity. Histological analysis performed 7, 14, 30, 60 postoperative days, C-T analysis with determination Bone Mineral Density value of new structured tissue within the defect was done 30 days. Results indicate that ectopic bone formation has been inducted with rhBMP-7 and histological analysis shown mature bone with collagen and ostheociti 60th day. Early 7 day granulocyte tissue with angiogenesis was detected, and after 30 days ostheoblastsis shown with a lot of vascular and mezenhimal tissue. Ostheogenetic processes were characteristic for typical inter membraneous ossification without cartilage tissue. ALP activity was significantly increased 21 days. C-T and Bone Mineral Density value shown density of new structured tissue determinate as bone (413 mg/cm3 and 519 mg/cm3). Studies showed that concentration of 100 mg rhBMP-7 in collagen as career had strong ostheo inductive capacity. Conditions which module BMP depend ostheo induction should be considered in the future. Information could lead to improvements of rhBMP as substitution for bone graft in clinical practice.