| Objective: Tooth immediate implant model were set up by extracting the central incisor both in maxillary and mandibular of rabbits,simultaneously,well prepared biomimetic calcium phosphate(CaP)coating on titanium screw incorporated with or with not Recombinant human parathyroid hormone(1-34)[PTH(1-34)] loading would be implanted into the socket respectively.The aim of this study was to explore the role of local application of PTH(1-34)on immediate implant osseointegration by observing and measuring the situation of new bone regeneration around titanium screw.Methods:1 Fabrication of titanium screw coating: All titanium screw were roughened using 800# sandpaper,and then soaked in 5 M NaOH solution at 60°C for 24 h,rinsed thoroughly with de-ionized water and dried at room temperature.To avoid protein absorption onto the wall of container,all the tubes used in this study were pre-coated with 1 % bovine serum albumin(BSA).Twenty-four screws which were vertically placed into a 1.5 m L eppendorf tube containing 1.0 mL modified simulated body fluid and 100?g/ml PTH(1-34)was chosen to be used in experimental group.The modified simulated body fluid without PTH was employed to prepare 12 screws for in control group.All the samples were prepared at 42 C for 24 h in a water bath.After rinsed and dried,all the screws were kept at-20°C for future measurement.2 Group: Nine healthy adult New Zealand rabbits,male and female,were randomly divided into 2 groups,one group of 6 rabbits as the experimental group,while other 3 as control group.In the experimental group,each socket was implanted into a titanium screw with PTH loaded biomimetic CaP coating,while in the control group,implanted into a titanium screw with only Ca P coating.Animals would be killed at 4th,8th,and 12 th week respectively,which 2 experimental rabbits and 1 controlled rabbit for each time.3 Preparation of animal model: In order to extract incisor successfully,under local anesthesia,incisor crown would be ground off while cooling with 0.9% sodium chloride drop.This procedure would be repeated once a week,and kept for 3times.When gradual grinding was completed at the fourth week,rabbit's maxillary and mandibular incisors were extracted integrally.After filled with some heterogeneous freeze-dried bone firstly,each socket would be implanted into a titanium screw,sutured gingiva to cover the screw.4 Results observation: Animals were sacrificed respectively at 4th,8th and 12 th week after operation by deep anesthesia.Specimens of maxilla and mandible were harvest immediately.Generally observation was recorded to whether titanium screws became loose or fell off,and the situation of new bone tissue around them.X-ray examination was used to evaluate the osseointegration at the interface of the implant and surrounding bone.Bone density were measured by the gray value of regenerated osseous tissue around screw,and analyzed by statistical analysis software.As a biomechanical testing method,torque test was used to evaluate screw-bone integrate strength.Histological analysis was made by observing bone remodeling process around screw on HE sections.Results:1 General observation: In experimental group,no screw which became loose or fell off was founded,and each titanium screw was tightly encysted by bone tissue around.Screws became some loose in control group at 4th week,but did not fall off,while there was a bone defect existed at the top of the screw.With the extension of time,loose phenomenon gradually disappeared and bone defect area was reduced.2 X-ray observation: All titanium screws were still in specimens,and new bone mass around screws increased as time goes by.At 4th week,cloud-like new bone were surrounding the whole titanium screw in experimental group,while in contrast,shadow of low density and bone defection at the top of the screw was shown in control group.Compared with 4th week,bone density at 8th week was increased in both groups,and new bone boundaries could not be seen between screw and surround bone in experimental group.At 12 th week,new bone density was higher than that in normal bone in experimental group.In control group,though bone defect was vanished,the bone density was still low than normal.3 Bone density analysis: With the extension of time,the average gray values in each group were increased.At the same time point of 4th,8th,12 th weeks after operation,gray value of regenerated bone tissue around screw in experimental group was higher than that in control group,P value was 0.032,0.013,0.027 respectively,the results were significantly different,and were statistically significant(P < 0.05).4 Torque test: The peak torque values in each group were increased as time went on.Implant bone integrate strength in experimental group was higher than that in control group,P value was 0.04,0.018,0.002 respectively,the results shows significantly different,and were statistically significant(P < 0.05).5 Histological observation: At the same time point,osteogenesis showed occurring faster,and the regenerated osseous tissue had more maturity in the experimental group.A large number of osteoblast,bone lacunae,bone matrix,fibrous bone and new capillaries could be found in 4th week in experimental group sections.It was observed that a great number of connective tissue cells and osteoclasts in control group,and capillary sparse.At 8th week both group presented active osteogenesis,in experimental group part of the fibrous bone transformed into lamellar bone,and trabecular-like bone could be found,while in control group had a lower degree of maturity.In the sections of 12 th week experimental group,a large number of lamellar bone was founded,which was relatively low in control group.Conclusion: Local application of PTH can make bone formation occurring earlier,thus could help improve the osseointegration of titanium implants and enhance the stability of implant when local applying. |
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