Effects Of Hydrofluoric Combine With Silane Coupling Agent On The Bonding Strength Of Ceramic Bracket Under Different Treatments

Objective:It is inevitable for ceramic orthodontic bracket,an indispensable part of dental apppliance,to fall off during the process of fixation and correction.There are normally three ways to solve this problem,the first is to replace the deciduous with a new bracket,which is costly;the second is to select a metal bracket,which will make the correction difficult due to different materials;and the third is to reuse the deciduous bracket.However,it has always been a worth-exploring subject clinically to obtain the floor plate,which is economical and suitable,of the deciduous bracket.It is well-known that hydrofluoric acid can improve the bonding strength between porcelain surface and bracket.Nevertheless,it is rarely reported that whether the combination of hydrofluoric acid and coupling agent will enhance the adhesive force of deciduous bracket during the process of fixation and correction.This thesis aims to explore the suitable clinical bedside application through the following procedures.Firstly,the author will model an oral environment,deal the bottom of the dropped ceramic bracket with acid corrosion inhibitor and coupling agent after burning,sandblasting,polishing the bracket,then rebound it on the surface of teeth.Secondly,the author will compare it with the new bracket group and coupling agent group.At last,the author will measure the shear strength needed for dropping off with micro force testing machine,and observe the shear strength and the residual condition of the binder under different treatments.Methods: 1 Preparation of the Experimental Model 1.1 105 premolars were extracted for orthodontic treatment,and all the teeth selected for this study were in good condition.Brush the teeth with a brush before storage,then keep them in thyme solution,keep them in cold storage for less than 5 months.1.2 First is to temper the self-solidification resin,and fix premolar on the mould with a specifications of 5.4cm*3cm*2cm,making sure the bonding surface of the tooth bracket is perpendicular to the bottom surface of the base(measured with a right angle triangle plate)and the premolar is in the middle of the mould.Second is the make the top of the base reach the enamel junction,with the crow part exposing outside and refrigerating in the artificial saliva.2 GroupingThe author will make 105 premolars removed due to orthodontic reasons into dental models,and divide them into seven groups randomly,i.e.new brackets group(1),cauterizing + coupling agent group(2),sand blasting + coupling agent group(3),polishing + coupling agent group(4),cauterizing + hydrofluoric acid + coupling agent group(5),sand blasting + hydrofluoric acid + coupling agent group(6)and polishing,hydrofluoric acid + coupling agent group(7).3 Preparation of the Deciduous Ceramic BracketApart from the first control group,there are other six groups,with the number of tooth models being 90.The author will make dropped brackets on the lingual side of the other 90 without smearing acid corrosion inhibitor on the tooth surface.Then the author will smear 3M unite TM solvent on the bottom plate of ceramic brackets and the lingual side of tooth modules with hairbrush respectively,and appropriate 3M unite TM ointment on the bottom plate,and then clamp the brackets with tweezers,and bond them with the micro wet tooth model on the lingual side.Ten minutes later,the brackets were carefully removed with bracket forceps,then the deciduous ceramic brackets will be formed.4 Treatment of the Floor Plate of the Deciduous BracketApart from the first control group,the author will burn,sandblast and polish the deciduous ceramic brackets of the other six groups,with each method dealing with 30 brackets,and then bond them for later use.be Cauterizing,sand blasting and Polishing 5 The Bonding of Bracket 5.1 The Bonding of New brackets Group(1)The teeth surface of Group 1 will be etched with 35% phosphoric acid for about 60 seconds,douched with high pressure water gun for 30 seconds,and then blew high pressure jet for 15 seconds.Then the tooth surface and the bottom plate of new bracket will be coated with 3M unite TM solvent with hairbrush respectively,and the floor plate of new ceramic bracket will be coated with appropriate 3M unite TM ointment.Later,the author will clamp the new bracket with tweezers and bond it on the tooth model,and adjust it to requested location,i.e.the bottom plate of bracket should perpendicular to the self-solidifying plastic substrate.Then the author will to press the bracket gently with tweezer,squeezing out the excess adhesive,and making sure the bottom plate of bracket contact with the tooth surface evenly.5.2 The Bonding of Experimental GroupsThe bottom of processed ceramic bracket in Group5,Group6,and Group7 will be etched with 9.6% hydrofluoric acid for about 30 seconds,washed with high pressure water gun for 30 seconds,and then blew dry with high pressure jet.The author then will smear the bottom of the bracket with silane coupling agent using brush,and leave it for evaporation for 1min.Then the brackets will be bonded to the tooth model according to the procedures of Group1.Then the author will deal with the processed deciduous ceramic bracket in Group2,Group3 and Group4 with conventional silane coupling agent,and bond them to the tooth model in accordance with the operation procedure of Group1.5.3 After being bonded for 15 minutes,all models will be stored in distilled water with a temperature of 37?.24 h later,these models will be circulated in hot and cold cycle machine for 600 times.6 The Test of Shear StrengthThe author will put tooth models on the Indira Strong Pulse micro force testing machine,with the cutting head of the machine placing on the groove,a position between the bracket bottom and the bracket wing,and the shearing direction paralleling to the surface of adhesive bracket.Then the loading speed of the tool will be set as 5mm/min,and gradually increased.When the bracket is dropped off,the author will record the maximum shear stress whose unit is N.Then the shear strength,whose unit is MPa,will be calculated according to the formula t=F/S.7 Evaluation of the Adhesive Remnant Index(ARI)After the bracket is fell off,the author will observe the residual situation of the adhesive on tooth surface with decuple magnifier.8 Statistical Analysis 8.1 The author will conduct statistical analysis of the instantaneous shear strength value while the ceramic bracket is falling off with SPSS13.0 statistical software.Average shear strength(x)and standard deviation(s).8.2 Then the author will compare Group 2 with Group 5,Group 3 with Group 6,and Group 4 with Group 7 with LSD method.When P <0.05,it will be statistically significant.8.3 The author will also make comparisons among Group 2,Group 3 and Group 4,and among Group 5,Group 6 and Group 7,with variance analysis.8.4 The ARI will be scored with t-test.Results:1 The shear strength values of each group are as follows: Group 1:12.70 + 1.85 MPa;Group 2:5.80±2.79 MPa;Group 3:5.44±2.00 MPa;Group 4: 5.92±2.14 MPa;Group 5: 8.00±2.76 MPa;Group 6: 6.20±1.76 MPa;Group 7: 7.99±2.18 MPa.2 There is no statistically significant differences among Group 2,Group 3 and Group 4 whose deciduous ceramic brackets have been burned,sandblasted,polished and dealt with silane coupling agent(P>0.05).There is also no statistically significant differences among Group 5,Group 6 and Group 7 which have been dealt with acid corrosion inhibitor and silane coupling agent(P>0.05).However,there are statistically significant differences while comparing different treatments with Group 1(P<0.05).3 The deciduous ceramic brackets of Group 2,Group 3 and Group 4 have been burned,sandblasted,polished and dealt with silane coupling agent.And the shear strength of these three groups are 5.80± 2.79 MPa,5.44± 2.00 MPa,and 5.92±2.14 MPa respectively.There is no statistically significant difference among Group 2,Group 3 and Group 4 examined with variance analysis(P>0.05).4 The deciduous ceramic brackets of Group 5,Group 6 and Group 7 have been burned,sandblasted,polished and dealt with acid corrosion inhibitor and silane coupling agent.Among these three groups,Group5 has the biggest shear strength,i.e.7.99±2.18 MPa,Group 7 the middle,i.e.7.99 ±2.18 MPa,and Group 6 the smallest,i.e.6.20±1.76 MPa.There is no statistically significant difference among the three groups examined with variance analysis(P>0.05).5 There is statistical significance between Group 2 and Group 5,Group 4 and Group 7(P<0.05),but there is no statistical significance between Group 3 and Group 6(P>0.05).6 There is no statistically significant difference between Group3 and Group6,Group3 and Group 5,Group3 and Group7(P>0.05),but there is statistically significant difference between Group5 and Group2,Group4 and Group7,which shows that even though the shear strength of these six groups have been increased,but the differences among them are not significant(P>0.05).7 There is no significant difference among ARI score of these groups.Conclusion:1 The bond strength of ceramic bracket which has been burned,sandblasted and polished is lower than that of new bracket no matter the former is treated with hydrofluoric acid and silane coupling agent or coupling agent alone.2 If the deciduous ceramic bracket has been burned,sandblasted and polished,and treated with hydrofluoric acid and silane coupling agent,its effect will be better than that of bracket treated with coupling agent only.