Root apex position detection method

Abstract

Methods of detecting a root apex position of a root canal of a test tooth, including applying a plurality of types of measurement signals to one of the measurement electrode and the mouth electrode; sequentially applying each of the plurality of types of measurement signals to one of the measurement electrode and the mouth electrode; sequentially detecting a plurality of electrical characteristic values between the measurement electrode and the mouth electrode based on each of the applied measurement signals using a detection unit. The methods further include obtaining a test tooth data group; comparing the test tooth data group with a plurality of model tooth data groups; detecting whether one of the plurality of model tooth data groups is in a predetermined relationship with the test tooth data group; and displaying the detected result.

1 . A method of detecting a root apex position of a root canal of a test tooth, wherein a measurement electrode is inserted into the root canal, a mouth electrode is placed onto an intraoral surface, and the measurement electrode is moved through the root canal towards the root apex position, the method comprising:
 applying a plurality of types of measurement signals to one of the measurement electrode and the mouth electrode;   sequentially applying each of the plurality of types of measurement signals to one of the measurement electrode and the mouth electrode;   sequentially detecting a plurality of electrical characteristic values between the measurement electrode and the mouth electrode based on each of the applied measurement signals using a detection unit;   obtaining a test tooth data group comprising the plurality of electrical characteristic values sequentially detected by the detection unit;   comparing the test tooth data group with a plurality of model tooth data groups, each of the model tooth data groups comprising electrical characteristic values from between the measurement electrode and the mouth electrode with respect to each of the plurality of types of measurement signals obtained when a distal end of a measurement electrode is placed at a root apex of a model tooth, the model tooth including different model teeth for each model tooth data group;   detecting whether one of the plurality of model tooth data groups is in a predetermined relationship with the test tooth data group; and   displaying the detected result.   
   
   
       2 . The method of  claim 1 , wherein the plurality of types of measurement signals differ from each other in at least one of frequency, waveform, and peak value. 
   
   
       3 . The method of  claim 1 , wherein the plurality of types of measurement signals comprise two types of measurement signals, such that the two types of measurement signals have voltages which differ from each other in frequency. 
   
   
       4 . The method of  claim 1 , wherein the electrical characteristic value is at least one of an impedance value between the two electrodes, a current value flowing between the two electrodes, a voltage value between the two electrodes, and a phase difference between the current value or voltage value between the two electrodes and the measurement signal. 
   
   
       5 . The method of  claim 1 , wherein the predetermined relationship with the test tooth data group is at least one of a relationship in which the test tooth data group coincides with any one of the plurality of the model tooth data groups and a relationship in which a difference between the test tooth data group and the model tooth data group falls within a predetermined range. 
   
   
       6 . The method of  claim 1 , wherein displaying the detected result is used for at least one of displaying on, warning on, and controlling a dental instrument. 
   
   
       7 . The method of  claim 1 , wherein each of the plurality of model tooth data groups is one of measured data based on an actual tooth, theoretical data, simulation data, approximate data obtained by calculation based on measured data, or a combination thereof. 
   
   
       8 . The method of  claim 1 , further comprising root apex position model data and predictive intra-root-canal-position-specific model data, the root apex position model data comprising the plurality of model tooth data groups and the predictive intra-root-canal-position-specific model data comprising an electrical characteristic value predicted in a state in which the distal end of the measurement electrode is located at a position before the root apex position, the method further comprising the steps of:
 comparing a measured electrical characteristic value sequentially detected by the detection unit with the root apex position model data and the predictive intra-root-canal-position-specific model data;   detecting whether at least one of the root apex position model data and the predictive intra-root-canal-position-specific model data include data in a predetermined relationship with the measured electrical characteristic value; and   outputting a detected result.   
   
   
       9 . The method of  claim 8 , further comprising predicting an electrical characteristic value at a position midway between an intra-root-canal position indicated by the outputted, detected result and the root apex position, wherein the predicted impedance value is used as the intra-root-canal-position-specific model data. 
   
   
       10 . A method of detecting a root apex position of a test tooth and a distance between a distal end of a measurement electrode and the root apex position, wherein a measurement electrode is inserted into the root canal, a mouth electrode is placed onto an intraoral surface, and the measurement electrode is moved through the root canal towards the root apex position, the method comprising:
 applying a plurality of types of measurement signals to one of the measurement electrode and the mouth electrode;   sequentially applying each of the plurality of types of measurement signals to one of the measurement electrode and the mouth electrode;   sequentially detecting a plurality of electrical characteristic values between the measurement electrode and the mouth electrode with respect to each of the applied measurement signals using a detection unit;   obtaining a test tooth data group comprising the plurality of electrical characteristic values sequentially detected by the detection unit;   comparing the test tooth data group with a plurality of model tooth data groups, each of the model tooth data groups comprising electrical characteristic values from between the measurement electrode and the mouth electrode with respect to each of the plurality of types of measurement signals obtained when a distal end of a measurement electrode is located at each of a plurality of predetermined positions in a model tooth, the model tooth including different model teeth for each model tooth data group;   detecting whether one of the plurality of model tooth data groups is in a predetermined relationship with the test tooth data group; and   displaying the detected result as a position information.   
   
   
       11 . The method of  claim 10 , further comprising displaying the detected result using a display unit. 
   
   
       12 . The method of  claim 11 , wherein the plurality of types of measurement signals differ from each other in at least one of frequency, waveform, and peak value. 
   
   
       13 . The method of  claim 11 , wherein the plurality of types of measurement signals comprise two types of measurement signals, the two types of measurement signals having voltages which differ from each other in frequency. 
   
   
       14 . The method of  claim 11 , wherein the electrical characteristic value is at least one of an impedance value between the two electrodes, a current value flowing between the two electrodes, a voltage value between the two electrodes, and a phase difference between the current value or voltage value between the two electrodes and the measurement signal. 
   
   
       15 . The method of  claim 11 , wherein the predetermined relationship with the test tooth data group is at least one of a relationship in which the test tooth data group coincides with any one of the plurality of model tooth data groups and a relationship in which a difference between the test tooth data group and the model tooth data group falls within a predetermined range. 
   
   
       16 . The method of  claim 11 , wherein displaying the detected result is used for at least one of displaying on, warning on, and controlling a dental instrument. 
   
   
       17 . The method of  claim 11 , wherein each of the plurality of model tooth data groups is one of measured data based on an actual tooth, theoretical data, simulation data, approximate data obtained by calculation based on measured data, or a combination thereof. 
   
   
       18 . The method of  claim 11 , further comprising intra-root-canal-position-specific model data and predictive intra-root-canal-position-specific model data, the intra-root-canal-position-specific model data comprising the plurality of model tooth data groups and the predictive intra-root-canal-position-specific model data comprising an electrical characteristic value predicted at a position midway between a first predetermined position of a plurality of predetermined positions and a second predetermined position, the method further comprising the steps of:
 comparing a measured electrical characteristic value sequentially detected by the detection unit with the intra-root-canal-position-specific model data and the predictive intra-root-canal-position-specific model data;   detecting whether at least one of the intra-root-canal-position-specific model data and the predictive intra-root-canal-position-specific model data include data in a predetermined relationship with the measured electrical characteristic value; and   outputting a detected result.   
   
   
       19 . The method of  claim 18 , further comprising predicting an electrical characteristic value at a position midway between an intra-root-canal position indicated by the outputted, detected result and the next intra-root-canal position, wherein the predicted electrical characteristic value is used as the intra-root-canal-position-specific model data. 
   
   
       20 . The method of  claim 18 , wherein the plurality of types of measurement signals comprise two types of measurement signals, the two types of measurement signals having voltages which differ from each other in frequency. 
   
   
       21 . The method of  claim 18 , wherein the electrical characteristic value is at least one of an impedance value between the two electrodes, a current value flowing between the two electrodes, a voltage value between the two electrodes, and a phase difference between the current value or voltage value between the two electrodes and the measurement signal. 
   
   
       22 . The method of  claim 18 , wherein the predetermined relationship is at least one of a relationship in which the test tooth data group coincides with any one of a plurality of model tooth data groups in the intra-root-canal-position-specific model data and a relationship in which a difference between the test tooth data group and the model tooth data group falls within a predetermined range. 
   
   
       23 . The method of  claim 18 , wherein outputting the detected result is used for at least one of displaying on, warning on, and controlling a dental instrument. 
   
   
       24 . The method of  claim 18 , wherein the root apex position model data is one of measured data based on an actual tooth, theoretical data, simulation data, approximate data obtained by calculation based on measured data, or a combination thereof.