The ultimate goal of research on platelet concentrates (PCs) is to develop a more predictable PC therapy. Because platelet-rich plasma (PRP), a representative PC, was identified as a possible therapeutic agent for bone augmentation in the field of oral surgery, PRP and its derivative, platelet-rich fibrin (PRF), have been increasingly applied in a regenerative medicine. However, a rise in the rate of recurrence (e.g., in tendon and ligament injuries) and adverse (or nonsignificant) clinical outcomes associated with PC therapy have raised fundamental questions regarding the validity of the therapy. Thus, rigorous evidence obtained from large, high-quality randomized controlled trials must be presented to the concerned regulatory authorities of individual countries or regions. For the approval of the regulatory authorities, clinicians and research investigators should understand the real nature of PCs and PC therapy (i.e., adjuvant therapy), standardize protocols of preparation (e.g., choice of centrifuges and tubes) and clinical application (e.g., evaluation of recipient conditions), design bias-minimized randomized clinical trials, and recognize superfluous brand competitions that delay sound progress. In this review, we retrospect the recent past of PC research, reconfirm our ultimate goals, and discuss what will need to be done in future.
Objectives: The study purpose was to examine peri-implant bone alternations around osseointegrated implants caused solely by abutment screw preload stress using different tightening torque values. Materials and methods: Twenty 20-to 22-week-old Japanese white rabbits received two implants each in right and left femurs. Implants were randomly assigned to one of three tightening torque groups or the control (Cont) group. After 8 weeks, 35 Ncm torque was delivered to abutment screws in the recommended torque (RT) group (n = 16). Other screws received 70 Ncm torque as the high torque (HT) group (n = 16). Temporary tightening (TT) groups (n = 8) received only 70 Ncm torque without preload stress as screws were untightened immediately. Cont group (n = 40) remained in situ. Animals were euthanized at 4, 6, 8, and 10 weeks after torque application. Micro-CT images were then taken, and undecalcified ground sections were stained with toluidine blue. Results: Cross-sections of cortical bone showed remodeling activities adjacent to the implant in all groups. While bone marrow spaces appearance was relatively small in Cont and TT groups, RT and HT groups showed large bone marrow spaces and extensive remodeling activity. Bone-to-implant contact was significantly less in RT and HT groups compared with Cont and TT groups at different time points (p ˂ .05). Furthermore, RT and HT groups showed significantly less bone volume and area (p ˂ .05). Conclusion: Results suggested that preload stress without any occlusal loading might negatively affect peri-implant bone stability and initiate bone remodeling. This could alter bone mechanical properties, subsequently influencing long-term implant success.
Bone matrix collagen, is one of the major contributors to bone quality. No studies have examined how bone quality affects the results of bone transplantation. Collagen cross-links (CCL) are the key factor in collagen properties. The purpose was to investigate the influences of CCL for both grafted bone and recipient site bone on the success of bone augmentation. Four-week-old male Wister rats (n = 54) were divided into control and test groups. Control and test groups equally sub-divided into donors and recipients. An additional six rats were used to characterize bone at day zero. Test groups received 0.2% beta-aminoproperionitrile (BAPN) for 4 weeks as CCL inhibitor. Animals were further divided into donor and recipient groups. The transplanted bone chips integrated with host bone by 25% more in CCL-deficient animals compared to control. However, no difference in cortical thickness among all conditions. CCL-deficient transplanted bone did not show any extra signs of osteocyte apoptosis, while sclerostin expression was comparable to that in control. The host periosteum of CCL-deficient animals showed higher cellular activity, as well as higher bone quantity and osteoclast activity. Collagen cross-links deficiency in host bone might accelerate the incorporation of grafted bone. effect. Incorporation of the bone grafts appears to depend mainly on host condition rather than graft condition.
Background : Implant treatment is highly influenced by marginal bone (MB) stability that is usually thought to be influenced by occlusal load application and or peri-implant inflammation. However, the sole effect of abutment preload installation on MB around implant had not been studied yet. The contact force that brings the abutment and implant clamped together is called preload, which is a tensile force. Finite element analysis was conducted and revealed the existence of preload stress distributed in MB.Aim/Hypothesis : The purpose was to investigate histological MB alternations around osseointegrated dental implants caused by abutment screw preload using recommended and high tightening torque values in-vivo.Material and Methods : Sixteen Japanese white male rabbits were used. Each animal received two implants in each right and left femur.After eight weeks, test and control implants were randomly selected. A 35Ncm torque was applied to tighten abutment screws ( n = 16) as recommended preload group (RP). Other abutment screws ( n = 16) were subjected to 70Ncm tightening torque as high preload group (HP).Tightening group (HT) received only 70Ncm tightening torque without preload ( n = 8) as screw was untightened immediately. Control group (Cont) implants remained in-situ ( n = 24). Animals were sacrificed at 4, 6, 8, 10 weeks after abutment screw attachment. MicroCT images were taken, undecalcified ground sections were prepared, stained with Toluidine Blue and investigated under light microscope and polarized light.Bone volume fracture (BVF), bone-to-implant contact (BIC), and bone area (BA) were calculated and two-way ANOVA test was performed as statistical analysis. The ethical approval obtained as No.28-189-2 Niigata Uni Results : Cross sections of cortical bone showed bone remodeling activities adjacent to the implants in all specimens of all groups. While bone marrow spaces were relatively small in Cont and HT groups, RP and HP groups showed a larger area of bone marrow spaces, especially after 10 weeks. Those spaces were defined as Bone Multicellular Units (BMUs), which is responsible for cortical bone remodeling activities.Moreover, lamellar bone thickness appeared to be larger in Cont and HT groups compared to RP and HP groups. Under polarized light, lamellar bone in Cont and HT groups displayed alignments of orderly homogeneous collagen fibers perpendicular to the implant axial plane. In contrast, predominant transverse or alternated collagen fibers appeared in RP and HP groups. BIC was significantly lower in RP and HP groups compared to Cont groups at 6, 8, 10 weeks ( P ˂ 0.05). Furthermore, RP and HP groups showed significantly less BVF and BA compared to other groups especially at 8 and 10 weeks ( P ˂ 0.05). Conclusion and Clinical Implications :The findings indicated the possible transfer of preload stress from the implant-abutment joint to the surrounding MB even without occlusal loading. This study demonstrated active bone remodeling, the appearance of BMUs in the interested area and decrease of BI...
Background: Bone transplantation is occasionally required prior to implant installation. Since Autografting is thought to be a gold standard for bone augmentation, a proper understanding of the paradigms that affect the outcome of bone transplantation is important for better prognosis. It is believed that bone components other than Bone Mineral Density are also very important determinants of bone quality and one of those is collagen. The influence of collagen quality that possibly affects the outcome of bone grafting is still unknown. Aim and hypothesis:To understand the influences of collagen quality of bone on the prognosis of bone transplantation, we investigated the fate of transplanted bone and adjacent tissues at the recipient site along with the healing of the donor site. Methods and MaterialsWister male Rats (n=48) 4 weeks old were divided into test group (n=24) and control group (n=24). 0.2% Beta-Aminoproperionitrile (BAPN) was dissolved in test group water for 4 weeks. Control & Test groups were subdivided equally in to 2 groups; Donor Group (DG) and Recipient Group (RG). The subdivision was made to resemble bone grafting/transplantation settings. Two 5mm diameter calvarial bone chips were harvested from DG and grafted on RG. At 1, 2 and 4 weeks after the surgery, rats were sacrificed and the specimens were prepared from retrieved calvaria for decalcified histological sections. The sections were prepared for observation under light microscopy and histomorphometry. Results:In test group of RG subdivision, bridging rates between transplanted bone chips and recipient surface were higher in the BAPN group compared to control at all time points. Regarding the tissue changes in the calvarial defects of DG subdivision, BAPN group showed faster tissue formation, and gap closure compared to control group. Conclusions and Clinical Implications:A low quality bone grafts could be selected for bone augmentation clinically. In addition, the low collagen quality bone might accelerate bone formation in vivo. However, the maintenance of these formed bones adjacent to such transplants is important and the long term outcome should be studied. The finding reflects the necessity to develop new clinical parameters and methods for comprehensive pre-operative assessment involving the collagen quality.
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