富血小板血浆,种植体周围骨缺损 z-bo 2020-11-17 385

　　Background: The use of dental implants has become an important part of modern dental treatment. It is recommended to immediately implant a fresh extraction socket as a means to reduce bone loss and shorten the treatment time of the prosthesis. However, the residual bone defect, between the implant neck and the residual bone wall, may cause cell migration from connective tissue and epithelial tissue to the defect area, which can prevent the integration of the material and bone. For this defect, bone implantation and implant implantation are needed. Need to find replacement bone to reduce or avoid autologous bone grafting. Several materials, synthetically derived or processed from bone structures (xenografts) of other species, have been used to replace autologous bone. Bovine-derived xenogeneic bone is widely used as a bone graft material because of its abundant sources and easy transplantation. It can provide a bone conduction scaffold, which has a mineral content equivalent to that of human bone, so that it can be combined with the host bone. This is by far the best bone replacement material, combined with guided bone regeneration. For several years, platelet-rich plasma (PRP) has been thought to promote bone healing, especially bone graft materials mixed with PRP have been reported to enhance bone formation. The combination of PRP and autologous bone graft can increase the rate of bone formation and promote bone formation. Recently, PRP has become a valuable aid in many dental and oral surgery procedures, such as ablation surgery, periodontal plastic surgery, treatment of periodontal bone defects, and procedures related to implant placement. PRP can be defined as an autologous plasma whose platelet concentration is higher than the baseline. It is produced by centrifugation of the patient's own blood. Platelets release a variety of growth factors and cytokines for wound healing, such as platelet-derived growth factor (PDGF), transforming growth factor β1 and β2 (TGF-β1 and β2), vascular endothelial growth factor (VEGF), platelet-derived endothelial cell growth Factors, basic fibroblast growth factor, platelet activating factor-4. Therefore, PRP is a suspension of growth factors that has been proven to induce healing and regeneration of soft and hard tissues. However, reports on its biological effects on bone healing are contradictory. In the bone healing test of rabbit skull defect with autograft or without PRP, it was found that the relationship between PRP and autogenous bone did not improve the bone healing process. Tests have also proved that adding PRP to the allograft has no effect on the new bone formation of the graft. The inconsistency of these results led to the study of the effect of PRP on the healing of xenogeneic bone. Therefore, the purpose of this experiment is to evaluate the effect of PRP as an adjuvant combined with bovine xenogeneic bone to repair bone defects in rabbit dental implants.

　　Method: 24 titanium implants were used in the study, with a length of 8.5 mm and a diameter of 3 mm.

　　Collagen film is used as a barrier film to cover the entire surgical site. Twelve healthy female New Zealand rabbits aged 5-6 months, weighing 3.2-3.7 kg, were selected as animal models.

　　Preparation of PRP: 4 ml of autologous blood is drawn from each rabbit, connected to a 5 ml sterile syringe with a 23-gauge needle, and then added to a tube containing sodium citrate and mixed. The blood was initially centrifuged at 2400 rpm for 10 minutes to separate PRP and platelet-poor plasma (PPP). PRP and PPP were centrifuged at 3600 rpm for 15 minutes to separate PRP from PPP. The obtained platelet volume is about 0.5 ml, and then the platelet count is performed. In our laboratory animals, the platelet counts in whole blood and PRP were 236×103 /μL and 625×103 /μL, respectively. Using this blood system, the concentration of platelets in PRP was at least 2.6 times the baseline value of platelets. Before application, activate PRP with 10% calcium chloride solution and 1KU bovine thrombin. After activation, PRP turns into a gel-like substance and is mixed with xenografts in a ratio of 0.5 ml PRP and 0.5 mg xenografts.

　　Surgery: All rabbit operations are performed under aseptic conditions, under general anesthesia, induced by intramuscular injection of 5 mg/kg xylazine hydrochloride and 40 mg/kg ketamine, and a half dose of the same mixture is injected to maintain anesthesia. Then, the incision site is shaved and disinfected. 1.8ml 2% lidocaine hydrochloride contains 1:100,000 injection of epinephrine as local anesthesia at the incision site to reduce subcutaneous bleeding. There is an incision about 3 cm in length on the surface of the tibia, which is cut along the inside of the long axis of the tibia. Before implantation, under low-speed continuous sterile saline irrigation, a 6.5-7.0mm trephine drill was used to create an intraosseous defect through the cortical bone and cancellous layer in the implant area with a depth of approximately 3mm. The titanium implant has a length of 8.5 mm and a diameter of 3 mm, and is then placed through the defect and cortical bone to establish a standardized gap of 4 mm. A total of 24 implants and 1 tibia were implanted. All implants are stable when inserted. Two treatment methods were used to treat bone defects: (1) xenotransplantation alone was used as the control group transplantation, (2) xenograft mixed PRP was used as the experimental group transplantation. All experimental areas were covered with absorbable collagen membrane, and then the wound was closed with 4.0 black surgical thread. After operation, intramuscular injection of 50000IU/Kg penicillin G was administered every day for 3 consecutive days.

　　Tissue preparation: 12 rabbits were divided into 6 groups, each with a healing period of 1, 2, 3, 4, 5 and 6 weeks. At the end of each designated healing period, two rabbits were sacrificed with an excess of potassium chloride solution. The tibial implant and surrounding bone tissue were removed en bloc and immediately fixed by soaking in 10% neutral buffer formalin. It is dehydrated through a series of ethanol and then embedded in a methacrylic resin. The entire dehydration and penetration process usually takes 2 weeks. Section and perform HE staining.

　　Histomorphometry: After traditional optical microscopy, the bone morphometric measurement uses an automated two-image analysis software Image-Pro Plus. After magnifying the photo of the entire tissue specimen at 12.5×, the measurements required to measure each part through 50× and 100× magnifications, the various images do not overlap. The bone contact of the implant and bone healing is defined as the straight line length of the direct contact bone surface and the implant circumference divided by the distance from the crown surface treatment position to 2.1-2.7 mm along the implant surface.

　　Result: Histological appearance: Light microscopic examination section showed as follows: 2 weeks. In the control group, the tissue sections showed that the bone graft material had begun to absorb, and 2/3 of the bone gap formed new bone from the edge of the bone defect to the surface of the implant. However, in the experimental group, only new bone formation was observed in 1/3 of the bone space. In the 4-week control group, bone graft material still exists. The newly formed bone density on the implant surface is low. In the experimental group, 1/2 of the bone defect edge appeared on the surface of the implant, partially enclosing the bone graft material, and a small amount of absorption was observed. In the 6-week control group, the new bone completely filled the bone gap and was in full contact with the implant surface. A small amount of residual bone graft material appeared in the trabecular bone. In the experimental group, 2/3 of the bone space was completely filled with newly formed bone. The bone graft material is significantly less than the fourth week. The defect areas of the rabbits in each group showed different degrees of new bone formation, but the bone defects of the experimental group animals contained the least amount of new bone. Compared with the experimental group, the control group has more new bone around the prosthesis and better bone healing process.

　　Histomorphological analysis: Quantitative morphological analysis showed that the bone contact in the control group increased significantly. The bone contact rate of the implants in the control group was significantly higher than that of the experimental group.

　　Conclusion: This study reports the effect of PRP on repairing defects around bovine implants. Rabbit tibia creates bone defect. Dental implants are implanted in the defect with separate xenografts or a mixture of PRP and xenografts. The average percentage of single xenograft bone implant contact was 25.23±15.15%, while the average percentage of PRP and xenograft mixture bone implant contact was only 8.16±6.26%. Based on these findings, PRP-added bovine-derived xenogeneic bone was implanted around the dental implant to delay the healing of the bone around the implant. So far, scientific evidence regarding the efficacy and efficiency of PRP is still controversial.