Experiments On The Effect Of Two Different Micro/Nanocrystallization Methods On The Performance And Early Osseointegration Of Titanium Implant Surfaces

It is universally acknowledged that dental implantation is the first choicefor the treatment of dentition defect or missing, and good osseointegrationbetween the implant and bone is key to successful treatment. However, theduration of three to six months that osseointegration usually takes has greatlyinterfered the work and life of the patients. Therefore, the shortening oftreatment period of dental implantation through the promotion of dentalimplants osseointegration in early stage of implantation and the improvementof the load-bearing capacity of the implant has become clinical research hotspot. One effective and controllable method is the surface treatment of dentalimplants. In this study, two methods, hydrofluoric acid etching+anodizingand hydrofluoric acid etching+magnetron sputtering, were used respectivelyto treat titanium implant surfaces and micro/nanorough-surfaces whichcombined both the advantages of micro and nano surfaces were constructed.The performances of the micro/nanorough-surfaces treated with the twodifferent methods were compared, then all implants were implanted intoexperimental animals. Double fluorescence analysis, hard tissue slicing andbiomechanical tests were conducted to observe the osseointegration in earlystage of implantation, aiming at providing new implant surface treatmentmethods and experimental basis which could shorten the duration of theosseointegration process.Objective:1To evaluate the performance of titanium implant surfaces treated byhydrofluoric acid etching+anodizing and hydrofluoric acid etching+magnetron sputtering.2To compare the influences of micro/nanorough-surfaces treated with two different methods on the osseointegration in early stage of implantationthrough animal implantation experiments.Methods:1Construction and examination of micro/nanorough-surfaces: Fortytitanium plates were evenly divided into two groups: hydrofluoric acid etchedand anodized plates as group A; hydrofluoric acid etched and magnetronsputtered plates as group B. The surface properties of these treated plates wereassessed by scanning electron microscopy (SEM) and atomic forcemicroscope (AFM); the chemical composition were assessed by energydispersive X-Ray spectroscopy detector (EDS) and X-ray diffraction (XRD);the bonding strength were assessed by epoxy resin tensile test.2Animal experiment on osseointegration in early stage of implantation:Forty helical cylindrical titanium implants were evenly divided into twogroups: hydrofluoric acid etched and anodized implants as group A;hydrofluoric acid etched and magnetron sputtered implants as group B. Then,all implants were randomly implanted into the distal femurs of20SD ratswhich were double fluorescence sequential labeled after the surgery.2weekslater, fluorescence microscope observation and histological examination onthe hard tissue slices were conducted to evaluate the influence of the twogroups on osseointegration. The biomechanical property was measured byuniversal material testing machine.Result:1SEM: Group A showed a surface micro-structure consisted ofuniformly distributed and closely adjacent nanotubes. The spacing between themicron-hollow protuberances was4~10μm, and the diameter of the nanotubeswas80~100nm. Group B showed a surface micro-structure consisted ofclosely adjacent nanopillars. The spacing between the micron-trenches was1~2μm, and the diameter of the nanopillars was20~50nm.2AFM: Micro-structure surfaces with micron protuberances spacing of4μm formed on group A. On this basis blunt and loosely distributed nanoprotuberances formed. Micro-structure surfaces with micron protuberances spacing of2μm formed on group B. On this basis sharp and closely adjacentnano protuberances formed.3EDS: Both groups contained Ti and F. Strontium loaded on group Bthrough magnetron sputtering.4XRD: α-Ti crystalline phase appeared on both groups.5Bonding strength assessment: Epoxy resin tensile test showed that thebonding strength of group B was5.49±0.91KN, much higher than the3.73±0.58KN bonding strength of group A (P＜0.01).6Double fluorescence labeling: Immunofluorescences were visible withmicroscope. Calcein showed green fluorescence strips and most of them weredouble labeled, indicating that the bone metabolism and regeneration werevigorous after the surgery (1~3d). Areas labeled with tetracycline showedearth yellow strips, representing the bone reconstruction and maturity stages(11~13d). Both groups showed large areas of green and earth yellow strips,while the area of group B was broader than that of group A.7Hard tissue slicing: Ponceau staining showed that the implants andsurrounding bone tissues displayed different colors. Mineralized bonematrixes were red or brown, bone marrows were yellow, and the implantswere black. Implants of group B had more surrounding mineralized bonematrixes than those of group A. Bone-implant contact (BIC%) of group A andB was50.21±3.72and61.49±5.42, respectively. Statistical results showedthat group B had a much higher BIC%than group A (P<0.05).8Biomechanical test: The maximum pullout force of group A and B was74.15±5.11and90.08±7.32, respectively. Statistical results showed that groupB had a much higher maximum pullout force than group A (P<0.05).Conclusion：1The two different methods constructed micro/nanorough-surfaces withdifferent structures on titanium plates. Strontium loaded on the hydrofluoricacid etched and magnetron sputtered surface, while no new crystalline phaseappeared. The bonding strength of the magnetron sputtered group was higherthan that of the anodized group. 2Hydrofluoric acid etched and magnetron sputtered surfaces have a betterinfluence than anodized surfaces on dental implants osseointegration in earlystage of implantation.