Experimental Study On Restoration Of Bone Defect Around Titanium Screw Nail By Heterogeneous Freeze-dried Bone And Its PRF Compound

Objective:The object of the study is to observe bone regeneration in peri-titaniumscrew nail bone defect using heterogeneous freeze-dried bone and its PRFcompound, discuss the ossification function of heterogeneous freeze-driedbone and the effect of PRF in bone defect repair,through the establishment ofrabbit mandibular bone defect model, and immediately implantation oftitanium screw nails, heterogeneous freeze-dried bone and its PRF compound.Methods:1Animals grouping: Twelve experimental animals were randomly devidedinto three groups which killed separately in4th,8th and12th week aftersurgery. In all experimental animals, the right side of the mandible served asthe experimental group (implantation of heterogeneous freeze-dried bone)andthe left side as the control group(implantation of heterogeneous freeze-driedbone with PRF), using self-control.2Preparation of heterogeneous freeze-dried bone: Heterogeneous bone wastaken from human bone tissue and prepared by means of cleaning bonemarrow, deep freezing, freeze-drying and ray irradiation.3Preparation of PRF:Before anesthesia,5ml of blood was drawn from therabbit central ear artery and then was puted into no anticoagulant centrifugetube. And then it was centrifuged in the centrifuge at the speed of3000r/minfor10minutes. At last the blood in the blood collection tube was layered intothree layers, including upper layer, interlayer and bottom layer. Upper layerwas cell-free plasma and bottom layer was erythrocyte and the rest was PRFgel. Then gently squeezing out serum in PRF using two layers of gauze, PRF gel became tough membranous.4Establishment of an animal model of bone defect: Under anesthesia, make aincision of15mm in the skin corresponding the upper edge of the rightmandible (experimental group), bluntly dissect muscle and periosteum andfully expose upper and buccal edge on the toothless alveolar bone. At last abone defect that was5mm×4mm×3mm in size was prepared in exposedtoothless alveolar, with normal saline washing. The same surgical methods asthe left (control group).5Implantation of titanium screw nail: Two planting nests were separatelyprepared on the bone near mesial and distal edge of the alveolar bone defect.This planting nest without one bone wall was implanted titanium screw nailwhich size is1.5mm×3.5mm afterwards.6Implantation of heterogeneous freeze-dried bone and its PRF compound:Heterogeneous freeze-dried bone and PRF were implanted in right(experimental group) bone defect; only heterogeneous freeze-dried bone in left(control group) bone defect.7Observations: Animals in each group were killed in4th,8th and12th weekafter surgery. General observation included the condition of the defect healingand tightness of the titanium screw nails on both sides. X-ray observationincluded the condition of newborn bone density and bone resorption. Bonedensity was represented by gray value. The measured gray value was countedfor the statistical test. According to the statistical result we could compare thedifference between the experimental and control groups. The tissue went bytaking materials, slicing, HE staining, and was observed under lightmicroscope.Results:1gross observation：Any titanium screw nail was not loose and falling off. Atvarious time points, osteogenesis of the experimental group was better thanthat of the control group. Compared to the control group, the sclerotin of thenew bone of the experimental group was harder and the surface was smoother.2X-rays observation：At various time points, There did not show obvious radiolucent lesions and abnormal bone resorption area in the titanium screwnail-bone interface. With the increase of time, bone mineral density risedgradually.3BMD analysis：Using statistical analysis software for X-ray gray values forstatistical analysis，the results showed that at the same time (in4,8,12weeks),gray values of the new bone near the side of bone defect of mesial and distaltitanium screw nails in experimental group were higher than that in controlgroup and it is statistically significant (P<0.05).4histopathoIogy observation: In4th,8th and12th week after surgery，the newbone of the experimental group was better matured and a number of osteoblastand osteocyte were observed. Bone trabecula were arranged orderly andcalcification degree was high slightly. Compared to the experimental group,the mumber of osteoblast and osteocyte of the control group were fewer.Bone trabecula were fewer and calcification degree was lower.Conclusion:1Heterogeneous freeze-dried bone as a bone substitute can repair bone defectsaround titanium screw nails.2PRF plays a significant role of promoting osteogenesis in bone defect repairusing heterogeneous freeze-dried bone.