The Influence Of Different Coarsening Treatment To The Fatigue Resistance Of Pure Titanium Implant

Objective:Thanks to its well restoring the beauty and chewing function of patients with missing teeth,artificial implants were widely used in recent years.Titanium is viewed as the ideal implant material currently due to its good biocompatibility and excellent corrosion resistence.Surface morphology of the implants have a huge impact on the rate of the osseointegration process.Studies have shown that surface coarsening treatment of titanium implants can not only broaden the contact area and increase mechanical embedding ability of implants and alveolar bone,but also lead the distribution of stress more uniformity and therefore shorten the period of the osseointegration process and improve the success rate of implants.Surface modification technology including methods of sandblasting-acid etching,micro-arc oxidation,anodic oxidation,alkali heat treatment,laser processing,etc.Among all those surface modification technologies,sandblasting-acid etching method is relatively more mature and widely used to make implants obtain ideal surface topography.In the point of view of engineering,dental implants is a kind of engineering parts with special structure,which need to possess enough strength,stiffness and fatigue resistance.Typically,implants can withstand the mouth chewing stress is determined by its strength and rigidity,and the use of implant period length is decided by its anti-fatigue performance.Therefore,all implant components have to possess excellent fatigue resistance performance.A comparative study according to the international standards ISO 14801:2008 was performed using two-phase threaded cylindrical pure titanium implants with and without the surface treatment of sandblasting-acid etch as the subjects,and Implant surface topography,surface relative element content and its fatigue strength were tested to analyze the influence of the surface treatment of sandblasting-acid etch on dental implant fatigue resistanceperformance to provide theoretical basis for the design of dental implants with better biological properties and mechanical properties.Method:1 Design and manufacture of specimens1.1 Design: Twenty-six modular implants with pure titanium abutments,each of which comprises a pure titanium in-connection implant,a mating central screw bolt,a abutment and a metal cap.1.2 Manufacture: The diameter of each implant is 4.0mm,total length 14.5mm;Thread area: length 11 mm,vertex 60 degrees,height 0.40 mm,pitch 0.8mm;Abutment length 5mm;length of inner connection part 1.5mm;Metal cap:outer diameter 6.5mm,inner diameter 4.6mm,height 6.5mmCleaning all the 26 specimens ultrasonically with acetone?75%alcohol and distilled water respectively for 20 min.Normal temperature drying was processed for use.2 Grouping and implant surface coarsening treatmentGroups: Group A and Group B,each group has 13 pieces of pure titanium specimensGroup A:?control group?: No surface roughing treatment processed.Ra:1.6?m.Specifically divided into:A_{static load}: Static failure load with 1 specimen.A₁: Preload with 3 specimens.A350NA₂: Peak load less than A₁ with 3 specimens.A_325NA₃: Peak load less than A₁ with 3 specimens A_300NA₄: Maximum endured load with 3 specimens A_275NGroup B:?TiO₂ sandblasting-60? acid etching group?: Under the sand blasting pressure of 0.2MPa,the sandblasting machine evenly sprayed 80 mesh TiO₂ sand to the surface of the implants thread area with a time of 7seconds;acid etching the implants with a mixture of HCl of 18% with H₂SO₄ of 49% under the condition of water bath at 60? for 40min;Specifically divided into:Bstatic load: Static failure load with 1 specimen.B₁: Preload with 3 specimens.B350NB₂: Peak load less than A₁ with 3 specimens.B_325NB₃: Peak load less than A₁ with 3 specimens.B_300NB₄: Maximum endured load with 3 specimens.B_275N3 Scanning electron microscopy?SEM?observation and surface relative elements content analysisUsing scanning electron microscopy?SEM?to observe surface morphology and X-ray spectroscopy?EDX?to analyze surface relative element contents of Group A and B.4 Fatigue testThe universal test machine loaded the specimens with a resin fixture,and the angle of inclination of the specimen with respect to the load axis was 30 degrees.The loading center,which is the hemispherical metal cap on the implant,was on the central longitudinal axis of the dental implant.The implant was fastened at a 3 mm distance from the apex from the level of the treated surface of the implant.Testing was carried on with a unidirectional and sinusoidal load at 15 Hz for 5×10⁶ cycles in room air at 25?.The loading rate was 1mm/min.Starting load was 80% of the load to failure in a static test performed using the same test geometry.Subsequent tests typically were performed at lower loads.Generating the data at a series of loads,until a lower limit?maximum endured load?was reached.Three specimens were tested at each of four loads.Under the maximum load,3 specimens of were not deformed or damaged by the completion of 5×10⁶ cycles.The hemispherical loading surface and the surface of the loading device were examined visually after each test to ensure that permanent deformation had not occured.If permanent deformation was observed,the deformed components were replaced and the test should be repeated.Record the test data and draw the load cycle diagram.Results:1 SEM observations of surface topography1.1 At low magnification?×35?Group A: Smooth and level.Group B: Rough;No impurities and even in the groove and slope of the thread;Dotted and stripe like hollows in the ridge of the thread.1.2 At high magnification?×2000?×5000?×8000?Group A: In the same direction of shallow groove grain structures with dotted hollow occasionally.Group B: Many cavities with the diameter 3³2?m.In these first class cavities,there are many irregular second class cavities with the diameter2⁵?m,and the edge is blunt,the level is clear.2 EDXA analyzingThe vast majority elements of the surfaces of Group A and B are titanium element.The content is above 99.50%.3 Fatigue test results of two groups of pure titanium implantGroup A: The maximum endured load A₄,i.e.,fatigue strength is 275 N,Under this load,3 specimens are completed 5×10⁶ cycles of load without deformation or failure.The static failure load is 439N;The preload A₁ is 350 N,which is 80% of the static failure load.A₂:325N;A₃:300N;Group B: The maximum endured load A₄,i.e.,fatigue strength is 375 N,Under this load,3 specimens are completed 5×10⁶ cycles of load without deformation or failure.The static failure load is 573N;The preload B₁ is 450 N,which is 80% of the static failure load.B₂:425N;B₃:400N;Conclusions:1 The fatigue strength of the pure titanium implants treated by sandblasting-pickling and the strength of the implant without roughening treatment are all within the range of the bite force of the oral cavity,which can meet the requirements of clinical application.2 The fatigue strength of pure titanium implant treated by sandblasting-pickling is better than that of pure titanium implant withoutroughing treatment.3 The appropriate design of the surface sandblasting-pickling treatment not only makes the ideal surface morphology of the titanium implant,but also improves the osseointegration of the implant,and can improve the fatigue strength of the pure titanium implant.