# US 8,540,511 B2 · Method and device for determining the apical position in a dental root canal > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,540,511 B2 - Document ID: US8540511B2 - Status: Granted - Kind: B2 - Application number: 12/934,181 - Filed: 2008-04-07 - Published: 2011-02-17 - Granted: 2013-09-24 - Earliest claimed: 2008-04-07 - Assignees: Maillefer Instruments Holding Sarl - Applicants: Francois Aeby; Pierre-Andre Farine; Roman Merz; Cyril Botteron - Inventors: Francois Aeby; Pierre-Andre Farine; Roman Merz; Cyril Botteron - Web page: https://patentgrep.com/patent/US8540511B2 ## CPC - A61B 5/063: {using impedance measurements} - A61B 5/0534: for testing vitality of teeth - A61B 5/4547: {Evaluating teeth} - A61C 19/041: {for measuring the length of the root canal of a tooth} - A61C 19/042: {for determining the position of a root apex} - A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D) - A61C: DENTISTRY; APPARATUS OR METHODS FOR ORAL OR DENTAL HYGIENE (non-driven toothbrushes A46B; {tongue scrapers A61B17/24;} preparations for dentistry A61K6/00; preparations for cleaning the teeth or mouth A61K8/00, A61Q11/00) ## Abstract An apex-locating method and device for determining the depth position of the apex in a dental root canal. It uses a device making it possible to form a circuit including a first probe electrode inserted into the root canal of a tooth, a second electrode in conductive contact with an oral mucous membrane, frequency-generating elements able to produce alternating electrical signals at a number of frequencies, and elements for measuring electrical magnitude of alternating signals in the circuit. Provision is made for exciting the circuit and measuring the levels of magnitude of the alternating signals, respectively at low frequency and at high frequency and for detecting a point of intersection where the two levels measured at low and high frequencies meet and become substantially equal, these frequencies being sufficiently far apart for this point of intersection to exist. This point gives the position of the apex. ## Claims ### Claim 1 Apex-locating method for determining a measurement (M) of the depth position of the apex in a root canal of a tooth (α, β, γ, Δ), using a device comprising a first conductive electrode (E1) forming an endodontic probe (S) able to be inserted into the root canal (CR) of a tooth, a second electrode (E0) shaped to be brought into electrically conductive contact with an oral mucous membrane, frequency-generating means (GF) able to produce alternating electrical signals at a number of frequencies, and means (AM) for measuring the magnitude of alternating electrical signals in a circuit comprising said frequency generator, the first probe electrode inserted into the root canal and the second electrode in contact with the oral mucous membrane, said method comprising the steps of: exciting the circuit and measuring the levels of magnitude (I) of the alternating electrical signals in the circuit, respectively at a lower frequency (f) and at a higher frequency (F); and detecting a point of coincidence (C) where two respective levels (If, IF) of the electrical magnitude (I) measured at said lower and higher frequencies (f, F) meet and are substantially equal, said lower and higher frequencies (f, F) being sufficiently far apart for such a point of coincidence (C) to exist, said point of coincidence (C, M) corresponding to the position (X) of the apex. ### Claim 2 (depends on 1) Apex-locating method as claimed in claim 1, characterised by measuring amplitude levels of the electrical signals applied to the circuit and/or the intensity (I) of the current passing through the electrodes (E0-E1). ### Claim 3 (depends on 2) Apex-locating method as claimed in claim 2, characterised by measuring absolute voltage amplitude values (U=Rm.I) of the electrical signals at the terminals of a resistor (Rm) in series with the electrodes (E0-E1-S). ### Claim 4 (depends on 1) Apex-locating method as claimed in claim 1, characterised in that the lower frequency (f) and the higher frequency (F) are selected so that in an initial phase (I), corresponding to the commencement of the insertion of the end of the endodontic probe electrode (E1-S) at the beginning of the root canal (CR), the first level (If=I1) measured at the lower frequency (f) is higher than the second level (IF=I2) measured at the higher frequency (F). ### Claim 5 (depends on 1) Apex-locating method as claimed in claim 1, characterised in that the lower and higher frequencies (f, F) are selected in opposing frequency bands (BF, HF) which are non-adjacent. ### Claim 6 (depends on 1) Apex-locating method as claimed in claim 1, characterised in that said lower and higher frequencies (f, F) are separated by one or more orders of magnitude. ### Claim 7 (depends on 1) Apex-locating method as claimed in claim 1, characterised in that said lower frequency (f) is selected in a low frequency band (BF) while said higher frequency (F) is selected in a high frequency band (HF). ### Claim 8 (depends on 1) Apex-locating method as claimed in claim 1, characterised in that said lower frequency (f) and said higher frequency (F) are located respectively in two opposing frequency ranges (BF, HF) on either side of a frequency range including at least the conventional number four band (VLF or hm.W.B. or no. 4) which covers the frequencies of three kilohertz to thirty kilohertz (3-30 kHz). ### Claim 9 (depends on 1) Apex-locating method as claimed in claim 1, characterised in that the lower frequency (f) is lower than 950 hertz. ### Claim 10 (depends on 1) Apex-locating method as claimed in claim 1, characterised in that the higher frequency (F) is higher than 9500 hertz. ### Claim 11 (depends on 1) Apex-locating method as claimed in claim 1, characterised in that the lower frequency (f) is located between 300 hertz and 30 hertz. ### Claim 12 (depends on 1) Apex-locating method as claimed in claim 1, characterised in that the higher frequency (F) is located between 300 kHz and 3 MHz. ### Claim 13 (depends on 1) Apex-locating method as claimed in claim 1, characterised in that the lower frequency (f) is in a frequency band of ten hertz to 100 hertz, while the higher frequency (F) is selected in a frequency band of the order of one half megahertz to ten megahertz, adjusting the choice of the higher frequency (F) to a value selected among a group of plural calibrated values depending on the electrolytic conditions prevailing in the root canal (CR). ### Claim 14 (depends on 1) Apex-locating method as claimed in claim 1, characterised in that the lower frequency (f) is lower than 500 hertz. ### Claim 15 (depends on 1) Apex-locating method as claimed in claim 1, characterised in that the higher frequency (F) is higher 95 kHz. ### Claim 16 (depends on 1) Apex-locating method as claimed in claim 1, characterised in that, the lower frequency (f) is in a frequency band of ten hertz to 100 hertz, the higher frequency (F) is selected in a frequency band of the order of one half megahertz to ten megahertz, and the higher frequency (F) is adjusted to a value selected among a group of plural calibrated values around 0.5 MHz, 1 MHz, 2 MHz, and 5 MHz, depending on the electrolytic conditions prevailing in the root canal (CR), including the presence of a conductive aqueous ionic solution. ### Claim 17 (depends on 16) Apex-locating method as claimed in claim 16, characterised in that the conductive aqueous ionic solution includes one of a physiological liquid based on a saline solution of sodium chloride (NaCl) or a Dakin's liquid based on a disinfectant solution by sodium hypochlorite (NaClO). ### Claim 18 (depends on 1) Apex-locating method as claimed in claim 1, characterised in that the lower and higher frequencies (f, F) are selected in opposing frequency bands (BF, HF) which are distinct. ### Claim 19 (depends on 1) Apex-locating method as claimed in claim 1, characterised in that said lower and higher frequencies (f, F) are separated by four orders of magnitude.