The Effect Of Angulated Abutment To The Fatigue Strength Of Pure Titanium Implant With Surface Roughening Treatment

Objective:when straight abutments used as superstructure of implants,people find that the abutments have some issues in its clinical application,like wise when jaw angle of implant area was too large for reasons or avoid some important anatomic structure like base of maxillary sinus or inferior alveolar nerve,it is difficult to rebuild patients'physiological occlusion by using straight abutments.With rapid development of implant restoration technology and biomechanical research,on the basis of straight abutment,a new type of abutment is developed,which the abutment's axis and implants'axis do not at the same line.Now,the world's largest manufacturers of dental implants developed their own angulated abutment.After long-term clinical application and research,people found that comparing to straight abutment,angulated abutment have some certain advantages:more extensive implanting indications,improving length and diameter of implants,shorten cycle of implanting treatment,avoid certain surgical complications and meet personalized requirements of patients.However,the application scope of angulated abutment has its limit,with increase of abutment's angle,lateral stress of implant and stress of surrounding bone interface increased.Overloard stress will eventually result in the failure of implant surgery.In addition,it's universally acknowledged that surface roughening treatment can increase the implant bone interface contact area,improve osseointegration and raise the success rate of implant surgery,but the research of whether it could effect the entire implant's mechanical strength rarely have,when using this technique into angulated abutment.Two-phase threaded cylindrical pure titanium implant is chosen as subject.Pure titanium angulated abutment and pure titanium straight abutment is chosen as superstructure of the implants.All of the subjects got sandblasting with large grit and acid etching and tests the capability of resisting lateral dynamic loading by using universal testing machine.The aim of this experiment is to find the effect of angulated abutment to the mechanical strength of pure titanium implant with surface roughening treatment and provid theoretical basis for angulated abutment's clinical application.Method:1 The design,manufacture,group and surface coarsening of pure titanium implantsThe design of implants:the implants are a combination of pure titanium angulated abutment implant and a combination of pure titanium straight abutment implant,with 24implants,12 angulated abutment,12 straight abutment,24 central bolts.The manufacture of specimen:All of the implants were of gingival type,the implants connect to the abutments with internal hexagon.The implant length is 14.5mm,the thread length is 11.0mm,the screw diameter is 4.0mm,the pitch is 0.8mm.The angulated abutment length is 6.9mm,the insert part?internal hexagon?length is 1.6mm,the exposed part length is 5.3mm,the inclined angle of exposed part is 15°.The straight abutment length is 5mm,the insert part length is 1.5mm,the exposed part length is 3.5mm.The central bolts length is 9.5mm.The group of experiment:24 implants were divided into group A and B,each group has 12implants.Group A?experimental group?is pure titanium angulated abutment implants with TiO₂ sandblasting and acid etching,including 4 secondary groups:3 implants of Group A_450N?Peak load is 450N?,3 implants of Group A_425N?Peak load is 425N?,3 implants of Group A400N?Peak load is 400N?,3implants of Group A_375N?Peak load is 375N?.Group B?contral group?is pure titanium straight abutment implants with TiO₂ sandblasting and acid etching,including 4 secondary groups:3 implants of Group B_450N?Peak load is 450N?,3 implants of Group B_425N?Peak load is425N?,3 implants of Group B_400N?Peak load is 400N?,3 implants of Group B_375N?Peak load is 375N?.Ultrasonic clean the two groups of pure titanium implants 20 minutes using acetone,75%alcohol,distilled water respectively.Dry under the normal temperature.The surface coarsening of implantsGroup A?pure titanium implants with angulated abutments?:80 mesh number TiO₂ sand,0.2Mpa sandblasting air pressure;concentrated HCl/H₂SO₄etching 40 minutes under 60?.Group B?pure titanium implants with straight abutments?:80 mesh number TiO₂ sand,0.2Mpa sandblasting air pressure;concentrated HCl/H₂SO₄etching 40 minutes under 60?.2 SEM and EDXA of surface topography after the two groups implants coarsening process.Choosing one implant randonly from the two groups to use SEM to observe surface topography and EDXA to analysis surface element.3 Stromeyer test of pure titanium implantsPMMA resin is used to embed A,B group of thread area and formed the test fixture.The fixture is a cylindrical which the diameter is 20mm,the height is 25mm.The top of fixture is located beneath the top of thread area about 3.0mm±0.5mm.Using the same universal testing machine to load group A,B respectively,the fixed form of fixture refer to ISO14801:2007.Test environment:air,temperature is 20±5?.The experiment adopt one-way load as its loading mode.The experimental loading should be float as sine curve between loading peak and 10%loading peak.The frequency of load is 15Hz.The initial load of group A,B is 450N.Each loading test 3 times.The result of single test has two types individually:the cycle reaches 5 million times,the cycle damag before reach 5 million times?damage means material yield,permanent deformation,loosening or fracture of any component of implants?.If one implant from three testing subject in single test do not reach5 million times,then reduce the loading force and test again,until all three implants from a loading test reach 5 million timesRecord the data and draw load-cycle diagram.Compare mechanical strength of the two kinds of abutment.Result:1 SEM observations of surface topography of the two groupsAfter Ti O₂ sandblasting and 60?HCl/H₂SO₄ mix acid etching 40minutes,the thread surface is rough,without metallic luster and black gray on gross examination.Coarser under lower lens,no impurities in the groove and slope of the thread,dotted and stripe like hollows can be detected on the crest of thread.Coarser under high lens,There is no obvious irregularity on the surface of implants.The surface of whole implants can be seen in various irregular cavities,hollows and fissures,which the diameter is about 10⁴0?m.In the first class cavities,hollows and fissures,there are many irregular second class cavities which the diameter is about 1⁵?m.2 EDXA analyzing of the two groupsThe elements of the surfaces of Group A,B are all titanium element.The content is 99.50%.3 The results of fatigue strength test of the two groupsGroup A?pure titanium angulated abutment implants?:the circulation number of A_450N is 1.50E+04,3.00E+04,9.00E+04;the circulation number of A_425N is 3.30E+05,4.00E+06,5.00E+06;the circulation number of A_400N is5.00E+06,5.00E+06,5.00E+06.The maximum tolerance load is L_F1=400N.The load of 400N has already finished Five million times circulation of three test specimens,so the experiment is over and group A_375N do not need to continute.Group B?pure titanium straight abutment implants?:the circulation number of B_450N is 1.30E+03,2.30E+03,5.00E+03;the circulation number of B_425N is 1.70E+04,3.20E+04,4.30E+04;the circulation number of B_400N is2.00E+05,3.50E+06,5.70E+05;the circulation number of B_375N is 5.00E+06,5.00E+06,5.00E+06.The maximum tolerance load is L_F2=375N.Except one test specimen broke at the abutment interface,all group A specimens'failure mode is flexural strain,the bending position is located at the top of the fixture.All group B specimens'failure mode is flexural strain,the bending position is located at the top of the fixture.Conclusion:1 Using ISO14801:2007 as test criteria,the fatigue strength of angulated abutment implant is better than straight abutment implant.It's indicated that angulated abutment do not effect fatigue strength of implant and can meet the requirements of clinical application.2 After surface coarsening treatment,the fatigue strength of angulated abutment implant and straight abutment implant is high than bite force required for human daily chewing.It's indicated that angulated abutment still can meet the requirements of mechanical strength of biomaterials,when using surface coarsening treatment to improve osseointegration and the success rate of implanting.3 The loading angle of angulated abutment's fatigue strength test should exist diversity angle design at different directions.