An Experimental Study About PRF Combined With Induced Bone Matrix In Repairing Of Bone Defects Around Implants

With the improvement of the living standards and the development of dental implant technology,more and more patients choose implant-support denture,not limited to young people as before.Due to the constraints of dental implant,less patients were fully in accord with its condition.However,with the ripeness of dental implant and further research on tissue engineering,peri-implant bone defect is no longer the taboo of implant surgery and bone deficiency which had plagued dentists a long time can be solve in more than one way,so more and more people can choose an ideal way to repair their teeth.In recent years,tissue engineering has been the focus of regenerative medicine research,in which growth factor arouses tremendous research.Along with the research and replacement of blood products to better play the role of growth factor.Platelet-rich fibrin(PRF)as a second-generation platelet concentrate product is obtained centrifugating autologous blood,without any anticoagulants and intensification matter.PRF contains white blood cell,fiber matrix and a variety of growth factors,which plays a key role in bone repairing,bone regeneration,anti-inflammatory and healing soft tissue.Experimental model in this paper is based on rabbit mandibular bone defect around implant region,by implanting medical induced bone matrix and different proportion of PRF mixtures of bone defect around implant to explore bone forming conditions.Objective:This study aims to explore whether regenerative repair of peri-implant bone defect can be promoted when applying PRF combined with medical induced bone matrix.The combined ratio,osteoblasts and osteoblast time are discussed,in order to reach the best recovery effect to provide theoretical basis for the clinical application.Methods:1 PRF preparation:20 m L of blood was obtained from the central artery of the rabbit ear and centrifuged for 8 min at 3000 rpm to get PRF.2 Establishment of peri-implant bone defects: Twelve rabbits were randomly divided into group 4w?group 8w?group 12 w.After weighing,one of them were anesthetized intravenously with 1 ml/kg pentobarbital sodium.After general anesthesia,placed the rabbit in a supine position,disinfected rabbit's forehead,paved sheet,and local infiltration anesthesia with 2% lidocaine hydrochloride.Cut the skin along the rabbit's inferior border of mandible,separated soft tissue and periosteum to fully expose the operation area,and ligatured the blood vessels.With a standard trephine bur,a pieces of bone grafts,three bone defects were made in each side,which is the left side and right side of the mandible.Each bone defect is 5 mm in diameter and 2 mm in depth,osteotomized from the inferior margin of 2mm.These bone defects were nearly 2mm away from each other.Then implanted titanium screws(diameter 2mm,length 7mm),these defects was respectively filled with nothing,PRF,bone matrix,mixture of PRF and bone matrix in different proportion,and sutured periosteum muscle and skin.Antibiotics were used 3 days to prevent infection after operation.One rabbit was selected randomly from each group.Tetracycline hydrochloride injection(25mg/kg)and calcein(5mg/kg)were administered subcutaneous injection separately at 10 days and 3 days before death.The animals of 3 groups were sacrificed after 4 weeks,8 weeks and 12 weeks respectively,isolating mandible and fixing it.Results:1 Experimental animal observation: The day after the surgery the rabbits were in poor spirit,less active without eating anything.They took small amounts of food the first day after surgery and returned to normal diet and activity,no infection and death three days after surgery.2 General observation: Operative incision of mandible were healing without swelling and the suture dropped off.All screws were fixed rigidly without loosening and shedding.At 4 weeks,screws in bone defects with filling showed different degrees of bone coverage without bone defect and unabsorbed bone particles at peri-implant,while there were no bone coverage but fibrous connective tissue at the screw surface in bone defects without filling.The longer healing time was,the thicker bone covered the same part of the implant surface was at 8weeks and 12 weeks.3 X-ray examination: There were different degrees of high density around titanium screws in all group.Titanium screws were wrapped by the bone tissue form nut to thread.There were different degrees of bone between screw threads,and the density of bone increased with PRF concentration increasing.On the contrary,there was a low density lesion between screw and bone when the bone density was relatively low,and some bone defects were even visible.4 HE staining: As PRF concentration increased,the density of interstitium and fibrous connective tissue became larger while the range of them decreased obviously.The number of blood vessels and osteoblasts increased and trabecular bone was found.Over healing time,bone trabecula arraged more regularly than ever,having the shape of island shape which would finally be a lamellar structure with a large amount of bone lacunas.Bone formation rate:Bone formation rate from high to low was PRF:bone matrix 2:1,PRF,PRF:bone matrix 1:1,PRF:bone matrix 1:2,bone matrix,blank.5 Fluorescence labeling: Calcein as green fluorescent strip was located in the region where new bone formed,which represented vigorous degree of bone metabolism and proliferation;Tetracycline as a soil yellow located at the inner side of the new bone,representing bone remodeling and bone mature.The bone defect zone filled by PRF and bone matrix with mixing ratio 2:1 had the widest and largest number of strips,followed by bone defects filled only with PRF,with bone defect without nothing worst.And stripes were narrower and less as the decreasing of PRF.6 Methylene blue acid fuchsin staining: The implants were black,while bone tissue red.The 4w group showed trabecular bone,more fibrous tissue between bone tissue and implant.The bone defect without filled had a small amount of trabecular bone,and the implant was surrounded by fibrous tissue.Over healing time,bone tissue increased,and the bone trabecula became thicker which would finally fused.Conclusion:PRF and bone matrix in bone repairing bone defect had a good effect.When combining PRF and bone matrix,with the increase of PRF concentration,osteogenesis effect was better.The addition of induced bone matrix to PRF worked better than PRF alone in promoting bone repairing.The combined application of PRF and bone matrix could accelerate bone healing and shorten healing time.