Research Of Tooth Synthetic Measuring Instrument Based On LabVIEW

The measurement of tooth bite force and tooth mobility displacement could help us have a comparatively accurate objective understanding of oral cavity sick tooth,and have important reference value to the diagnosis of many kinds of periodontal diseases.Bite force is the chewing force produced through the function of muscles when the upper and lower teeth touch, and which is transmitted to the periodontal tissues from teeth, then transmits to the jaw bone and scatters.Clinical research indicates that bite force is one of the important signs reflecting the chew muscles and the jaw system.Tooth mobility is the activity degree of natural tooth or plant tooth while receiving the function of external force,which is an important index of appraising the support tissue's state of the natural tooth or the plant body,making remedy program and assessing the recovery in clinic.In the field of oral cavity repairing,tooth mobility have reference meaning of the choice of base tooth,appraising the influence of repairing design towards base tooth or the curative effect of periodontal splint towards mobile tooth's fix.In sum,developing a set of synthetic measuring instrument which could precisely measuring tooth bite force and the mobility displacement at the same time,low cost and easy clinic pratice has great meanings.Some conductors,when they are out of shape that affected by external force in certain direction,it will produce polarising phenomenon inside,and will produce the electric charge on its surface,when the force is removed,it will get back to the state not with electricity again,this is called normal piezoelectricity effect.On the contrary,add electricity field on the dielectric polarized direction,it will produce mechanical deformation,this is called anti-piezoelectricity effect.The quartz crystal piezoelectricity sensor realizes energy tramform using the piezoelectricity effect of quartz crystal.The quartz crystal has the characters of bigger piezoelectricity constants,wider linear range, high inherent vibration frequency, good low frequency character and good stability of temprature,humidity and time.The structure of differential voltage transformer sensor is mainly the type of spiral tube,the coil is made up by the elementary coil and secondary coil.The coil is inserted of cylindrical iron core in its center.It could be divided into three-section type differential voltage transformer and two-section type differential voltage transformer,the two secondary coils of the differential voltage transformer are connected anti-phase.while adding certain changed voltage in the original coils,it will produce corresponding reaction voltage in the two secondary coils respectively,its magnitude has something to do with the position of the iron core in the spiral tube.The operation principle of the differential voltage transformer and the principle of general transformer are coincidence,the difference lies in:the general voltage transformer has a closed magnetism while the differential voltage transformer has a open magnetism;the mutual inductance between the general voltage transformer's winding is constant while the mutal inductance between the differential voltage transformer's winding is changed with the moving of the iron core.The operation principle of the differential voltage transformer sensor is set up on the basis of the change of mutual inductance.LabVIEW is the result that technology of the modern instrument and computer technology combine together. It gives full play to the strong ability of computer in data operation, data storing and data processing. LabVIEW has offered faster, simpler, more convenient, more flexible, high-efficient technological choice for engineers and technicians while developing the testing and measuring system,making the testing and measuring system has stronger property advantage, easy maintained and expanded, and can fully utilize the existing network advantage.This research proceeds from the angle of clinical application,under the existing technological condition,develops a set of tooth synthetic measuring instrument based on LabVIEW,mainly used in measuring the bite force and the mobility displacement of single sick tooth and display the force and displacement curve in real time.The diagram of the measuring instrument's signal transmitting shows as below:1,Quartz crystal piezoelectricity sensorThe quartz crystal piezoelectricity sensor changes bite force into measurable electric signal,its technical parameters are as follows:the sensitivity of electric charge is 3.60pC/N;the electric capacity is about 7pF;the insulating resistance is larger than 10¹²Î©;the measuring range is from 0 to 800N;the overload coefficient is 2.0;the frequency respond is from DC to 30KHz;the non-linear degree is less than 1% from -60 to +70℃;It adopts the outer cover of stainless steel, and receives force from the direction perpendicular to the direction of the aprons,cushions a layer of biomembrane on its surface while testing actually.2,Electric charge amplifierChoose a suitable electric charge amplifier according to the technical parameters of the quartz crystal piezoelectricicity sensor,change the electric charge signal into a voltage signal,make this signal pass a wave filter at the same time,filter the interfering signal.What this research selected for use is the type of TS5860 quasi-static electric charge amplifier,the parameters of this electric charge amplifier is as follows:the amount of electric charge imported is 0～106pCmax;the sensitivity of sensor adjusts from 1.00 to 9.99pC/Unit rightly;the sensitivity of electric charge is from 0.01 to 100mV/pC; 0.1,0.2,0.5,1,2.5,10,20,50,100mV/Unit are available for the output sensitivity;the accuracy is 1%;the dynamic time constant resistance is1.8×109?; the quasi-static time constant resistance larger than 1013?; the quasi-static time constant is 104～105s; the time drift is less than±0.03pC/s(20±3℃); the output is±10V/10mV with in-phase and opposite phase in duplex;the noise is smaller than 3×10-2pCRMS;the frequency respond is 2μHz～150KHz;the attenuation slope is 12±1dB/oct;the figure show is 0.000～10.000V;the resolution is 1mv;the precision is±0.1%; the power is 200V±10%,50Hz.3,DAQ cardConsider synthetically,we adopt the USB7822 DAQ card produced by HongTuo company.It is12 bits single-end 32 routes A/D transformation,16 routes TTL lever switches importation,16 routes TTL lever switches export to the interface board;we adopt high property transformation chip AD1674(BB774) in the A/D part,its transformation ratio is 100KHz,A/D has 2KB FIFO memory.We adopt Visual C++ to write the drive program of the DAQ card in this research, and then use the"Call Library Function Node.vi"to call the dynamic link library in LabVIEW to realize the operation to DAQ card.4,LabVIEW program and simulation testThe LabVIEW measuring program of measuring instrument is used for displaying the change condition of bite force and mobility displacement during the whole course of measuring and the maximum and average value.It gathers,analyzes and stores force and displacement signal through DAQ card.We could prove that the program is written correctly,run normally and could reach the purpose to measure two parameters at the same time by the simulation test.It could export the measuring target's personal information and the measuring result in the form of electric-form and benefit the follow-up analysis. 5,Measuring instrument's demarcationBecause the condition is limited,so this paper has only finished the demarcation and the measuring test of tooth bite force measuring system.After fininshing the design of measuring instrument's software and the building-up of hardware,we carried out the static and dynamic demarcation and the temperature drift test.Through the demarcation test,we could get that the sensitivity of the measuring instrument is 10.047mV/N;the nonlinear error is 0.14%;the repeatable error is 0.03%;the lagged error is 0.18%;the sensitivity change does not exceed 0.3% when loading dynamically;the temperature sensitivity coefficient is 0.002%/℃,each error index is smaller than 1%.6,Actual measuring testIn the actual measuring test,we select 6 experimenters whose bite relation is not unnormal obviously and carry on measurement to their first pair of sharp teeth. The test result shows that this measuring instrument could react the bite force curve in real time and display the bite force's maximum and average value once accurately.There is no obvious difference in a lot of measurement.At the same time it uses easily and measures quickly, achieves the goal we expected in this research.