The In Vivo Evaluation Of Micro/nano Topographic Implant In Canine Model

With the rapid development of dental implantation technology in recent years,dental implantation has become an important method for the treatment of tooth missing.At present,the implants widely used in clinical are pure titanium implants.After the implantation,there are some problems such as low biological activity,long healing time,poor osseointegration union and free titanium.Surface characteristic is one of the key factors that determine the long-term success of implantation^[1].The optimal design of implant surface morphology is an important method to improve the osseointegration.In the early stage,our team prepared micro/nano-textured containing different diameters nanotubes by means of acid etching and anodic oxidation from the perspective of bionics,and confirmed that the morphology had significant osteoinduction function^[2].In this study,the micro/nano-textured with different diameters nanotubes was loaded on the surface of the screw root implant commonly used in clinical practice.Through in vivo implantation experiments,the differences in osteogenic properties of nanotubes with different diameters were compared,and the implant was implanted into the mandible of beagle dogs with different primary stability.The osseointegration was analyzed and compared with the acid-etched and sand-blasted surface implants commonly used in clinical practice,so as to provide a reference for the clinical application.At the same time,according to the problems found in the experiment,the evaluation method of osseointegration was discussed.Part ? Implant surface micro/nano topography fabrication and integrityafter implantionObjective:To lay a foundation for the later evaluation of osseointegration in vivo,different micro-nano morphologies were constructed on the implant surface,and the integrity of the implant after implantation was observed.Methods:Prepared micro/nano-textured containing different diameters nanotubes by means of acid etching and anodic oxidation on implant surface,named V-5 group and V-20 group respectively according to the anodic oxidation voltage.Smooth surface implant?P group?and acid-etched and sand-blasted surface implant?SLA group?,which are commonly used clinically,were used as the control group.SEM was used to observe the surface morphology of the implant and observe its integrity after implantationResults:The uniform and compact nanotube structures were observed on the implant surface by SEM.The diameter of the V-5 nanotubes was about 30nm,and the length was not measured.The V-20 nanotubes were 80-100nm in diameter and 550nm in length.The surface morphology of V-5 group was well preserved after implantion,while the V-20group's micro-nano morphology of the surface showed slight wear and shedding,and the wear was mainly concentrated at the top of the screw.Conclusion:The micro/nano-textured morphology containing TiO₂ nanotubes can be constructed on the surface of pure titanium threaded implants,after the treatment of acid etching and anodic oxidation,the diameter of TiO₂ nanotubes is positively correlated with the anodic oxidation voltage.The micro/nano-textured morphology of the implant surface was basically integrated after the implant was inserted into the bone with 35N torsion,ISQ?70.Part ? The in vivo osseointegration of implants with different surfacemorphologiesObjective:To observe and compare the in vivo osseointegration of implants with different surface morphologies.Methods:Twenty four male beagle dogs were performed extraction from the second premolar to the first molar of bilateral mandible.After 3 months'healing,8 implants were implanted in bilateral mandible,with 2 implants from group P,V-5,V-20 and SLA.Measured implant stability quotient?ISQ?during and 2?4?8 weeks after surgery.Eight dogs were sacrificed at 2 weeks,4 weeks and 8 weeks after implantation,respectively.Micro-ct scanning,histological examination and EDX scanning were used to evaluate the osseointegration of implants with different surface morphologies.Results:Compared with the operation,the ISQ of each group decreased at 2 weeks,then increased at 4 weeks,and finally stabilized at 8 weeks.At 2 weeks,the ISQ of the micro/nano topographic implant decreased less than that of the P group,and the ISQ of the V-5 group decreased less than that of the V-20 group;Compared with bone parameters,the micro/nano topographic implant was superior to the P group in?BV/TV?and?Tb.Sp?,and was superior to the P group at 2 weeks?Tb.N?and 4 weeks?Tb.Th?.The bone parameters in V-5 group and SLA group were similar,superior to those in the V-20 group;Histological examination showed that the bone tissue around the implant with micro/nano-textured morphology and SLA group was more than that in the P group at the same time point,and the bone tissue in the thread groove of the V-5 group and SLA group was more than that in the V-20 group;The bone-implant contact?BIC?was higher in group V-5 and SLA than in group V-20 and P.EDX element scanning analysis showed that Ca and Pwt%of newborn bone around V-5 group,V-20 group and SLA group were higher than that of P group,and Ca and Pwt%of V-5 group and SLA group were higher than that of V-20 group.Conclusion:Compared with the smooth surface,the micro/nano-textured morphology can promote osseointegration,and the ability of small-diameter nanotubes to promote osseointegration is better than that of large-diameter nanotubes.The ability of small-diameter nanotubes to promote osseointegration and the strength of new bone are similar to that of acid-etched and sand-blasted implants.The ability of large-diameter nanotubes to promote osseointegration in the early stage is weaker than that of acid-etched and sand-blasted implants,and the strength of surrounding new bone is lower than that of acid-etched and sand-blasted implants.Part ? The influence of primary stability on the osseointegration ofmicro/nano topographic implantObjective:Observed the osseointegration of micro/nano topographic implant with different primary stability.Methods:Six beagle dogs were performed extraction from the second premolar to the first molar of bilateral mandible,nurture healing for 3 months.The ISQ was controlled with a tapping drill,and the small-diameter nanotube implants were implanted into the bilateral mandible of the beagle with less primary stability,which was recorded as group V-5?L?.Micro-ct scanning,histological examination and EDX scanning were used to evaluate the in vivo osseointegration,the results were compared with those of V-5 group.Results:The ISQ of V-5?L?increased rapidly in the first 2 weeks,slowed down in the 2⁴weeks,and stabilized in the eighth week;Results of bone parameters and BIC showed that at 2 weeks,V-5?L?group was lower than V-5 group,and equal at 4?8week.There was no significant difference in Ca,P wt%between the two groups.Conclusion:The small-diameter nanotube implants with less primary stability can achieve favourable osseointegration after 4 weeks.Reasonable implant implantation is expected to eliminate or reduce the bone remodeling period and accelerate the bone formation process.Part ? Research on advantage of the bone-implant contact evaluationby Micro-CTObjective:To discuss the advantage of using Micro-CT in bone-implant contact?BIC?evaluation,and provide reference for clinical and scientific research.Methods:Take the P group in part II as the research object,Micro-CT was applied to scan and reconstruct the samples,and to analyze bone-implant interface by selecting different analysis regions?25,50 and 100?m from implants'surface?,and evaluate BIC,and the results were counted as Micro-CT₂₅,Micro-CT₅₀,and Micro-CT₁₀₀ groups.The advantages and disadvantages,evaluation efficiency and BIC of Micro-CT and optical microscope were analyzed.Results:To evaluate single sample BIC,Micro-CT took much less time than optical microscope,and the success rate of Micro-CT modeling was higher than the success rate of making slides in the light microscope method;Results of BIC in Micro-CT₂₅ group at each time point were smaller than those in light microscope group,and there was no statistical difference between Micro-CT₅₀ group,Micro-CT₁₀₀ group and light microscope group.There was a higher correlation and consistency between Micro-CT₅₀ group BIC and light microscope group BIC.Conclusion:Micro-CT is a faster,simpler and more efficient way to analyze BIC than using the optical microscope.And BIC analysis by selecting 50?m from implants'surface as analysis region by using Micro-CT is in consistent with that when using the optical microscope.