WO2003039389A1 - Systems for ascertaining proximity of an oral surgical instrument to a mandibular canal and methods of protecting a mandibular canal from damage during an oral surgical procedure - Google Patents

Systems for ascertaining proximity of an oral surgical instrument to a mandibular canal and methods of protecting a mandibular canal from damage during an oral surgical procedure Download PDF

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Publication number
WO2003039389A1
WO2003039389A1 PCT/US2002/033718 US0233718W WO03039389A1 WO 2003039389 A1 WO2003039389 A1 WO 2003039389A1 US 0233718 W US0233718 W US 0233718W WO 03039389 A1 WO03039389 A1 WO 03039389A1
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WIPO (PCT)
Prior art keywords
mandibular canal
surgical instrument
oral surgical
canal
energy
Prior art date
Application number
PCT/US2002/033718
Other languages
French (fr)
Inventor
Dan Cohen
Alon Eitan
Yuval Jacoby
Garri Passi
Boris Pershitz
Yuval Shai-El
Pavel Smirnov
Uri Stein
Original Assignee
Imadent Ltd.
Friedman, Mark, M.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Imadent Ltd., Friedman, Mark, M. filed Critical Imadent Ltd.
Publication of WO2003039389A1 publication Critical patent/WO2003039389A1/en

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    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/68—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient
    • A61B5/6801—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient specially adapted to be attached to or worn on the body surface
    • A61B5/6813—Specially adapted to be attached to a specific body part
    • A61B5/6814—Head
    • A61B5/682—Mouth, e.g., oral cavity; tongue; Lips; Teeth
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B8/00—Diagnosis using ultrasonic, sonic or infrasonic waves
    • A61B8/08—Detecting organic movements or changes, e.g. tumours, cysts, swellings
    • A61B8/0858—Detecting organic movements or changes, e.g. tumours, cysts, swellings involving measuring tissue layers, e.g. skin, interfaces
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61C—DENTISTRY; APPARATUS OR METHODS FOR ORAL OR DENTAL HYGIENE
    • A61C1/00—Dental machines for boring or cutting ; General features of dental machines or apparatus, e.g. hand-piece design
    • A61C1/08—Machine parts specially adapted for dentistry
    • A61C1/082—Positioning or guiding, e.g. of drills
    • A61C1/084—Positioning or guiding, e.g. of drills of implanting tools
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B90/00—Instruments, implements or accessories specially adapted for surgery or diagnosis and not covered by any of the groups A61B1/00 - A61B50/00, e.g. for luxation treatment or for protecting wound edges
    • A61B90/03—Automatic limiting or abutting means, e.g. for safety

Definitions

  • the present invention relates to systems for ascertaining proximity of an oral surgical instrument to a mandibular canal and to methods of protecting a mandibular canal from damage during an oral surgical procedure. It is now common practice to replace a tooth with an implant-supported prosthesis. Placement of the implant to support the prosthesis entails exposing the jawbone (raising the mucoperiosteal flap), and drilling a receptive site for the fixture.
  • Panoramic X-ray Radiography The most common technique for preventing damage to the mandibular canal currently used in preparing an installation site for an implant is Panoramic X-ray Radiography.
  • Panoramic X-Ray Radiography has several inherent disadvantages. First, it is well established that X-ray radiation is hazardous to the health of the patient. Second, Panoramic X-ray is inherently distorted and inaccurate because it projects the three-dimensional jaw into a two-dimensional image. It is therefore unreliable for assessing the depth of the bone tissue available for drilling a fixture socket. Third, the X-ray image is taken prior to (as opposed to during) the drilling procedure so that it does not portray a position of the drill relative to the mandibular canal during the procedure. All of these disadvantages make the panoramic X-ray image a hazardous, imprecise, and unreliable solution for protecting the mandibular canal during an oral surgical procedure.
  • CT Computerized Tomography
  • a CT image of the lower jaw provides a sectional view of the jaw, and is less distorted than panoramic X-Ray Radiography.
  • CT involves a substantially higher dosage of X-ray radiation than conventional radiography, and therefore poses a significantly greater risk to the health of the patient.
  • CT equipment is expensive so that it is rarely found in a dental clinic.
  • the CT image is typically taken prior to (as opposed to during) the drilling procedure so that it does not portray a position of the drill relative to the mandibular canal during the procedure.
  • a method of protecting a mandibular canal from damage during an oral drilling procedure includes: (a) transmitting acoustic energy into the mandibular canal thereby causing the canal to function as an acoustic waveguide; (b) collecting data pertaining to a portion of the acoustic energy from a position outside the acoustic waveguide by means of an ultrasonic receiver; and (c) stopping progress of a drill when the portion of the energy reaches a predetermined limit.
  • a system for ascertaining proximity of an oral surgical instrument to a mandibular canal includes (a) an ultrasonic transmitter, the transmitter capable of transmitting acoustic energy into a mandibular canal, thereby causing the mandibular canal to act as an acoustic waveguide; (b) a pulser, the pulser capable of controlling a transmission from the transmitter; (c) an ultrasonic receiver, the receiver capable of receiving at least a portion of the energy transmitted by the transmitter; (d) an amplifier, the amplifier capable of amplifying the at least a portion of the energy received by the receiver; (e) a comparator, the comparator configured to execute an evaluation of the at least a portion of the energy received by the receiver according to a predetermined rule; and (f) an indicator, the indicator capable of communication with the comparator and designed and constructed display data pertaining to the evaluation to an operator of the system.
  • a system for ascertaining proximity of an oral surgical instrument to a mandibular canal includes: (a) an ultrasonic transmitter, the transmitter capable of transmitting acoustic energy into a mandibular canal, thereby causing the mandibular canal to act as an acoustic waveguide; (b) a pulser, the pulser capable of controlling a transmission from the transmitter; (c) an ultrasonic receiver, the receiver capable of receiving at least a portion of the energy transmitted by the transmitter; (d) an amplifier, the amplifier capable of amplifying the at least a portion of the energy received by the receiver; (e) an analog to digital converter designed and configured to convert the amplified at least a portion of the energy received by the receiver to a stream of digital data; (f) a central processor (CPU) designed and configured to analyze the stream of digital data according to a predetermined rule; and (g) an indicator, the indicator capable of communication with the CPU and designed and constructed display data
  • the method further includes attaching the ultrasonic receiver and the drill one to the other.
  • the method further includes processing the data pertaining to the portion of the acoustic energy to ascertain a parameter selected from the group consisting of an amplitude, a wavelength and a frequency of the portion of the acoustic energy.
  • the system further includes the oral surgical instrument.
  • the oral surgical instrument is a drill.
  • system further includes a controller designed and configured to operate the oral surgical instrument in accord with a signal received from the comparator.
  • the oral surgical instrument and the ultrasonic receiver are attached one to the other.
  • the comparator compares at least one data item selected from the group consisting of an amplitude, a wavelength and a frequency of the portion of the acoustic energy to a predetermined value.
  • the CPU is further designed and configured to operate the oral surgical instrument in accord with a result of an analysis of the stream of digital data.
  • the CPU analyzes a digital data stream representing at least one data item selected from the group consisting of an amplitude, a wavelength and a frequency of the portion of the acoustic energy with respect to a predetermined value.
  • the present invention successfully addresses the shortcomings of the presently known configurations by providing systems for ascertaining proximity of an oral surgical instrument to a mandibular canal and methods of protecting a mandibular canal from damage during an oral surgical procedure.
  • the present invention has, as an inherent advantage, the ability to provide relative positional information about the location of a surgical instrument during a procedure.
  • Implementation of the method and system of the present invention involves performing or completing selected tasks or steps manually, automatically, or a combination thereof.
  • several selected steps could be implemented by hardware or by software on any operating system of any firmware or a combination thereof.
  • selected steps of the invention could be implemented as a chip or a circuit.
  • selected steps of the invention could be implemented as a plurality of software instructions being executed by a computer using any suitable operating system.
  • selected steps of the method and system of the invention could be described as being performed by a data processor, such as a computing platform for executing a plurality of instructions.
  • FIG. 1 is a diagrammatic representation of a mandible including teeth and a mandibular canal
  • FIG. 2 is a diagrammatic representation of a portion of a mandible as in figure 1 illustrating insertion of a surgical implement therein;
  • FIG. 3 is a simplified schematic diagram of components of a system according to the present invention.
  • FIG. 4 is a flow diagram illustrating steps in a method according to the present invention employing the system of figure 3;
  • FIG. 5 illustrates placement of probes on a mandible in conjunction with practice of the present invention
  • FIGs. 6A and 6B illustrate the relationship between distance (d) and amplitude (A) according to the present invention
  • FIG. 7 is a simplified schematic diagram of components of an additional system according to the present invention.
  • FIG. 8 is a flow diagram illustrating steps in a method according to the present invention employing the system of figure 7;
  • FIG. 9 is a simplified schematic diagram of components of another additional system according to the present invention.
  • FIG. 10 is a flow diagram illustrating steps in a method according to the present invention employing the system of figure 9. DESCRIPTION OF THE PREFERRED EMBODIMENTS
  • the present invention is of systems for ascertaining proximity of an oral surgical instrument to a mandibular canal and is further of methods of protecting a mandibular canal from damage during an oral surgical procedure.
  • the present invention can be employed to insure that a surgical instrument, such as a drill, does not damage a mandibular canal or an inferior alveolar nerve.
  • the present invention can be used to reliably and safely allow implantation of an anchor for a dental prosthesis deep within the trabecular bone of the jaw without endangering the mandibular canal.
  • Mandible 30 includes several layers of tissue.
  • Mandible 30 features an external layer of mucoperiosteal tissue (gums 32) covering the jawbone.
  • Beneath gums 32 is a layer of cortical (compact) bone 34, which is normally characterized by a high density.
  • Beneath cortical bone 34 lies trabecular bone 36 which is typically softer than cortical bone 34.
  • mandibular canal 38 resides and contains inferior alveolar nerve 39.
  • Mandibular canal 38 is an elongated tubular cavity, typically bordered by cortical bone 34. In cases where dense borders are not present, mandibular canal 38 is a conduit within a sponge-like matrix. In the latter case, mandibular canal cavity 38 may be distinguished from the cavities of the trabecular environment 36 by the mandibular canal's regular shape (i.e. an elongated tubular cavity). All cavities inside the cross-section of mandible 30 are normally filled with fluids. The upper region of mandible 30 forms the alveolar ridge 40 in which teeth 42 are normally situated. Referring now to FIG.
  • the common procedure prior to installation of a dental fixture typically includes drilling into cortical bone 34 and trabecular bone 36 of mandible 30 using a drill 70, in order to prepare a socket in which a fixture may be anchored. If a practitioner drilling into mandible 30 is not aware of the precise location of mandibular canal 38, then during the drilling procedure drill 70 may contact and damage inferior alveolar nerve 39. Such damage typically causes severe pain and hemorrhage and has been known to induce local paralysis. For this reason, it is universally agreed that a practitioner must be able to cease drilling prior to damaging the mandibular canal.
  • the present invention is offered to provide a reliable and effective means to assure that progress of a surgical instrument, such as a drill, towards a mandibular canal is stopped before damage to the canal occurs.
  • the present invention is thus embodied by a method 120 (figure 4) of protecting a mandibular canal from damage during an oral drilling procedure.
  • the method includes transmitting 130 acoustic energy into the mandibular canal thereby causing the canal to function as an acoustic waveguide. This transmission is preferably accomplished by an emitting probe 106.
  • probe 106 is coupled to a pulser 104 operably connected to a controller 102. Alternately, probe 106 may be connected directly to controller 102.
  • Transmitting 130 may be accomplished, for example, by coupling 122 emitting probe 106 to a patient, activating 124 pulser 104 (e.g. by means of controller 102), Generating 176 an electric signal and converting 128 the electric signal to an acoustic signal. The result of these actions is to transform mandibular canal 38 into an acoustic waveguide.
  • Method 120 further includes collecting or receiving 132 data pertaining to a portion of the acoustic energy from a position outside the acoustic waveguide by means of an ultrasonic receiver 108 and stopping progress of drill 70 when the portion of the energy reaches a predetermined limit. Stopping progress of drill 70 may be accomplished, for example, by issuing 140 a warning. The warning may be, for example, a visible indicator, an audible signal or a tactile stimulus. In order to make method 120 more efficient, it is preferable to attach ultrasonic receiver 108 to drill 70 or to integrally form these two components of system 100 together.
  • energy received 132 by probe 108 may be converted 134 to an electric signal which is optionally, but also preferably, amplified 136 by amplifier 110. This facilitates comparison 138 by means of comparator 112.
  • a measured amplitude A n is compared to a predetermined maximum amplitude (A max ). When A n exceeds A max indicator 114 issues 140 a warning. While amplitude corresponding to a portion of the acoustic energy received at probe 108 outside of canal 38 is used in this example, wavelength or frequency may also be employed without significantly affecting practice of method 120.
  • the relative position of transmitter 106 and receiver 108 in the context of mandible 30 is illustrated in figure 5.
  • System 100 for ascertaining proximity of an oral surgical instrument to a mandibular canal.
  • System 100 includes an ultrasonic transmitter 106 capable of transmitting 130 acoustic energy into mandibular canal 38, thereby causing the mandibular canal to act as an acoustic waveguide.
  • System 100 further includes a pulser 104 capable of controlling transmission 126 from transmitter 106 either alone or in combination with controller 102.
  • System 100 further includes ultrasonic receiver 108 capable of receivingl32 at least a portion of the energy transmitted by transmitter 106.
  • System 100 further includes amplifier 100 capable of amplifying 136 the at least a portion of the energy received 132 by receiverlO ⁇ .
  • amplification 136 occurs after conversion 134 of the energy to electric energy.
  • System 100 further includes comparatorll2 configured to execute an evaluation of the at least a portion of the energy received 132 by receiver 108 according to a predetermined rule.
  • the rule may be, for example, a comparison of A réelle to A max as detailed hereinabove.
  • System 100 further includes indicator 114 capable of communication with comparator 112 and designed and constructed display data pertaining to the evaluation to an operator of the system. According to one preferred embodiment of the invention indicator 114 and drill 70 are functionally combined. According to this embodiment, issuing 140 of a warning includes interruption of a power supply to drill 70.
  • System 100 preferably further includes a controller (e.g.
  • system 100 designed and configured to operate oral surgical instrument 70 in accord with a signal received from the comparator 112.
  • drill 70 functions as indicator 114 and cessation of the motor of drill 70 serves as the warning. Therefore, it is preferable for system 100 to include the oral surgical instrument, for example drill 70. This configuration functions optimally when oral surgical instrument 70 and ultrasonic receiver 108 are attached one to the other or integrally formed together.
  • the present invention is further embodied by a system 200 (figure 7) for ascertaining proximity of oral surgical instrument 70 to a mandibular canal 38.
  • Use of system 200 constitutes an additional method 220 (figure 8) according to the present invention.
  • System 200 includes ultrasonic transmitter 106, pulser 104, receiver 108 and amplifier 110 each as described hereinabove.
  • System 200 further includes an analog to digital converter (ADC) 202 designed and configured to convert the amplified at least a portion of the energy received by the receiver to a stream of digital data and a central processor (CPU) 204 designed and configured to analyze the stream of digital data according to a predetermined rule (e.g. threshold value 204').
  • ADC analog to digital converter
  • CPU central processor
  • system 200 includes indicator 114.
  • indicator 114 is, in this case, capable of communication with CPU 204 and designed and constructed display data pertaining to analysis with respect to rule 204' to an operator of system 200.
  • CPU 204 is further designed and configured to operate oral surgical instrument 70 in accord with a result of an analysis of the stream of digital data. This operation may require additional inputs either prior to onset of operation or during operation of system 200. These inputs may be, for example, in the form of programmed instructions, or direct operator input including, but not limited to, keyboard input, voice commands, joystick input, touch screen input, menu selections or inputs from other mechanical or electronic control devices.
  • CPU 204 may analyze, for example, a digital data stream representing an amplitude, a wavelength or a frequency of the portion of the acoustic energy with respect to a predetermined value 204'.
  • method 220 (figure 8) is similar to method 120 as described hereinabove except that received 132 acoustic signal is first converted 134 to an electric signal, then amplified 136 and then converted 222 a second time to a digital signal with a value V.
  • comparison 224 is between V n and V max (i.e. predetermined value 204') instead of between A n and A max as in method 120 detailed hereinabove.
  • controller 102 it is preferable for controller 102 to be coupled to pulser 104, which is coupled to emitting probe 106.
  • Receiving probe 108 is preferably coupled to amplifier 110, which is coupled to either comparator 112 or ADC 202/CPU204, which is coupled to indicator 114.
  • Controller 102 includes means for controlling the operation of pulser 104, for example, an on/off switch and preferably additional adjustable elements enabling the user to determine pulse frequency, voltage, and duration, as well as other relevant parameters.
  • Pulser 104 is operable to generate electric pulses based on parameters set by controller 102.
  • Emitting probe 106 is operative to convert electric pulses into analog acoustic (mechanical) pulses.
  • emitting probe 106 includes a wideband piezoelectric transducer, although any other known type of emitting transducer is also within the scope of the present invention.
  • Receiving probe 108 is operative to convert acoustic pulses into analog electric pulses.
  • receiving probe 108 includes a wideband hydrophone transducer, although any other known type of receiving transducer is also within the scope of the present invention.
  • Both probes 106 and 108 are preferably biocompatible, meaning that they can be safely placed in contact with a living organism, especially inside the mouth of a patient.
  • receiving probe 108 is preferably small enough in diameter (e.g. 3 mm or less) to fit inside the fixture socket drilled by drill 70.
  • a hydrophone transducer may be used for this purpose.
  • Amplifier 110 is operative to amplify electric pulses to a predefined level or by a predefined factor.
  • Comparator 112 is operative to receive amplified electric pulses and to compare their amplitude to a predetermined threshold amplitude A max .
  • the threshold amplitude can be hardwired (i.e. a permanent threshold amplitude), or preferably, it can be controlled and changed by the user using a threshold amplitude control element 112' (i.e. an adjustable threshold amplitude).
  • a threshold amplitude control element 112' i.e. an adjustable threshold amplitude
  • Indicator 114 includes at least one means for notifying an operator of the system that the predetermined threshold has been met, for example, a light-emitting diode (LED) that emits red light, a cathode-ray tube (CRT) that displays a warning message, a buzzer that produces a warning sound, or any other known indicator.
  • a light-emitting diode LED
  • CRT cathode-ray tube
  • cessation of a motor of drill 70 preferably serves as the means for notifying an operator.
  • a preferred method 120 of operation of system 100 is described in greater detail. According to method 120, an operator of system 120 couples 122 emitting probe 106 to a first location 51 on mandible 30, and receiving probe 108 to a second location 52 thereon (step 122).
  • Either or both locations can be on a surface inside the mouth cavity, such as the buccal or lingual gum surface, or outside the mouth cavity, such as the skin surface of the cheek or chin.
  • either or both probes can be coupled directly to a bone surface (cortical or trabecular) of the mandible.
  • the operator couples 122 emitting probe 106 to a location that is assumed or known (e.g. empirically) to maximize penetration of acoustic emission into mandibular canal 38, for example, on the buccal gum surface covering the anterior opening 381 of the mandibular canal.
  • anterior opening 381 is situated a few millimeters below and between the roots of the second bicuspid and first molar teeth (on either side of the mouth).
  • the operator couples 122 receiving probe 108 to the alveolar ridge that is covering the implant site being prepared, whilst facing downwards (toward the mandibular canal).
  • probe 108 will be placed inside the drilled socket, again facing downwards (toward the mandibular canal).
  • the user may swap the locations of the emitting and receiving probes, so that emitting probe 106 is coupled to the implant or drilling site whilst receiving probe 108 is coupled facing the anterior opening of the mandibular canal.
  • a coupling material is preferably applied between each probe (106 and 108) and the jaw surface.
  • the fluids present in the mouth of the patient e.g. saliva, blood, drill cooling water
  • a commercially available non-toxic ultrasound coupling gel or similar composition may be employed.
  • mandibular canal 38 when an acoustic signal is emitted toward the mandibular canal, mandibular canal 38 will serve as a waveguide for the signal (as illustrated in figure 5). This phenomenon occurs for two reasons. First, mandibular canal 38 is normally filled with nerves, blood vessels and other soft or fluid tissues which possess more favorable acoustic properties (e.g. lower attenuation) than the surrounding bone tissue. Second, the mandibular canal's 38 tube-like bone tissue borders cause acoustic waves to be repeatedly reflected from the internal walls of the canal, and hence to propagate along and inside the canal.
  • Pulser 104 When the probes 106 and 108 are properly coupled, the operator adjusts the pulse parameters and activates 124 pulser 104 using controller 102. Pulser 104 generates an electric signal based on the provided parameters and sends the signal to emitting probe 106 (step 126). Emitting probe 106 converts 128 the electric signal to an acoustic signal, for example, a wideband ultrasonic pulse at a frequency range of approximately 1 to 3 MHz. The acoustic signal is then emitted 130 toward mandibular canal 38. Part of the energy of the emitted signal penetrates the border between the emitting probe and mandible 30. Part of the energy of the penetrating signal travels toward anterior opening 381, and then continues to propagate inside mandibular canal 38.
  • acoustic signal for example, a wideband ultrasonic pulse at a frequency range of approximately 1 to 3 MHz.
  • the acoustic signal is then emitted 130 toward mandibular canal 38. Part
  • Receiving probe 108 converts 134 the received acoustic signal to an analog electric signal.
  • Amplifier 110 amplifies 136 the electric signal and sends it to comparator 112.
  • Comparator 112 compares 138 the amplitude of the signal A n to the predetermined threshold amplitude A max .
  • the predetermined threshold amplitude can be permanent, or preferably, adjustable. If adjustable, the operator will set a desired threshold amplitude using control element 112' at any time prior comparison 138. It is well known that the degree of attenuation of an acoustic signal is correlated to its travel distance (d). In particular, the greater the distance an acoustic signal travels through a medium which causes attenuation (e.g.
  • a first distance d ⁇ between mandibular canal 38 and the bottom of the socket correlates to a first amplitude A] received by receiving probe 108: d A X
  • a second distance d 2 between mandibular canal 38 and the socket correlates to a second received amplitude A 2 : d 2 ⁇ A 2
  • the first distance is shorter than the second distance: d ⁇ > d 2
  • the second amplitude is greater than the first amplitude:
  • comparison 138 by comparator 112 ascertains whether or not received amplitude A n is greater than the predetermined threshold amplitude A max . As long as A n is less than or equal to A max , system 100 will continue to generate electric signal 126 without issuing 140 any warning to the operator. As soon as A n exceeds threshold amplitude A max , comparator 112 sends an electric signal to indicator 114 which immediately indicates to the user that any further drilling may be too close to mandibular canal 38 by issuing warning 140. As indicated, cessation of generation 126 of electric signal may accompany the warning.
  • FIG. 7 depicts, an alternate system 200 according to the present invention which is partially similar to system 100.
  • System 200 includes a controller 102, a pulser 104, an emitting probe 106, a receiving probe 108, an amplifier 110, and an indicator 114, all similar to those described hereinabove with reference to system 100.
  • system 200 does not include a comparator 112. Instead, the comparison function is performed by an analog-to-digital converter (ADC) 202, and a processor 204.
  • ADC analog-to-digital converter
  • controller 102 is coupled to pulser 104, which is coupled to emitting probe 106.
  • Receiving probe 108 is coupled to amplifier 110, which is coupled to ADC 202.
  • ADC 202 is coupled to processor 204, which is coupled to indicator 114.
  • ADC 202 comprises a conventional analog-to-digital converter that is operable to convert an analog electric signal into a stream of digital samples or readings, at a predetermined sampling rate (e.g. 40 MHz).
  • Processor 204 comprises digital computing means, for example, a conventional IBM-compatible PC.
  • Processor 204 is operable to receive from ADC 202 a stream of digital samples representing the received acoustic signal, and to compare each sample value V n to a predetermined threshold value V max .
  • the threshold value preferably, can be controlled and changed by the user (i.e.
  • processor 204 detects that a value of an incoming digital sample VNT exceeds the given threshold value V max , it sends a message, such as an electric signal, to indicator 114.
  • indicator 114 may be as described hereinabove with respect to apparatus 100.
  • indicator 114 of system 200 further includes a computer monitor capable of communication with processor 204.
  • Operation of system 200 constitutes a method 220 which is similar to method 120 described hereinabove and common actions are therefore denoted with the same reference numerals.
  • steps 122 through 136 of method 220 are identical to these steps in method 120 described hereinabove.
  • ADC 202 After the received electric signal is amplified 136, the signal is converted 222 by ADC 202, at a predetermined sampling rate, into a stream of digital samples.
  • ADC 202 sends the digital samples representing the received acoustic signal, to processor 204.
  • Processor 204 executes 224 a first algorithm (e.g. computer executable code, software code, etc.) for comparing the digital value of each incoming sample V n to the predetermined threshold value V max .
  • a first algorithm e.g. computer executable code, software code, etc.
  • the first algorithm can be any known algorithm for comparing each value in a series of digital values to a predetermined value.
  • the predetermined threshold value can be permanent, or preferably, adjustable. If adjustable, the user will set the desired threshold value using control element 204' at any time prior to execution 224 of the first algorithm.
  • the practitioner performs the steps of method 220 repeatedly, after every desired depth is drilled (e.g. every 1 mm). As the practitioner drills nearer to mandibular canal 38, the acoustic travel distance from emitting probe 106 to receiving probe 108 is shortened; and as the acoustic travel distance shortens, the amplitude of the signal received by receiving probe 108 increases.
  • FIG. 9 depicts an additional system 300 according to the present invention.
  • System 300 includes the same elements as apparatus 200, except that instead of a threshold value control element 204' apparatus 300 comprises a threshold central frequency control element 204".
  • processor 204 is operable to receive from ADC 202 a stream of digital samples representing the received acoustic signal, to produce a frequency domain of the signal, to find the central frequency , in the frequency domain of the signal, and to compare the central frequency to a predetermined threshold central frequency f max .
  • the threshold central frequency preferably, can be controlled and changed by the user (i.e. an adjustable threshold central frequency) using threshold central frequency control element 204".
  • the threshold central frequency can be hardwired (i.e. a permanent threshold central frequency) in the electronic circuitry of processor 204.
  • FIG. 10 depicts a method 320 of operation of apparatus 300 according to the present invention.
  • Method 320 is partially similar to method 220 common portions of the method are denoted with the same reference numerals. Thus, steps 122 through 222 of method 320 are identical to these steps in method 220 described hereinabove.
  • processor 204 executes a second algorithm, such as a known FFT (fast Fourier transform) algorithm, for producing 322 a frequency domain (e.g. an array of amplitudes per frequency) of the digital samples received from the ADC.
  • FFT fast Fourier transform
  • processor 204 executes a third algorithm for finding 324 the central frequency f max in the frequency domain of the received acoustic signal, i.e. the frequency around which most of the energy of the received signal is concentrated.
  • processor 204 further executes 326 a fourth algorithm for comparing the central frequency/ to the predetermined threshold central frequency/, ⁇ .
  • the fourth algorithm can be any known algorithm for comparing two digital values.
  • the predetermined threshold central frequency 204" can be permanent, or preferably, adjustable. If adjustable, the user will set the desired threshold frequency using control element 204" at any time prior operation 326.
  • the degree of attenuation of an acoustic signal correlates to certain changes in the frequency domain of the signal.
  • the greater the distance an acoustic signal travels through a medium which causes attenuation e.g. bone tissue
  • the central frequency of the signal e.g. bone tissue
  • the practitioner performs the steps of method 320 repeatedly, after every desired depth is drilled (e.g. every 1 mm). As the practitioner drills nearer to mandibular canal 38, the acoustic travel distance d from emitting probe 106 to receiving probe 108 is shortened; and as d shortens, the central frequency/ in the frequency domain of the signal received by receiving probe 108 increases.
  • processor 204 sends an electric signal to indicator 114 which immediately indicates 140 to the operator that any further drilling is too close to mandibular canal 38.
  • an oral surgical instrument for example drill 70 used for drilling a receptive socket for a dental implant, is included in system 100, 200 or 300 as described hereinabove.
  • either emitting probe 106 or receiving probe 108 is mounted on oral surgical instrument 70, preferably on the distal tip of the bit and facing mandibular canal 38.
  • the method of operation according to this embodiment is similar to the method of operation of systems 100, 200 or 300, respectively.
  • This embodiment is preferred because providing a surgical tool 70 on which one of probes 106 or 108 is mounted eliminates the need to stop the surgical procedure (e.g. stop drilling into the jawbone) before each comparison of a determined data value to a threshold data value. Instead, determined data values are constantly compared to the threshold value as work proceeds, resulting in a continuous workflow until issue 140 of a warning.
  • the present invention provides accurate, safe, radiation-free, and economical method and apparatus for detection and location of mandibular canal 38 in situ during an oral surgical procedure, preferably without interruption of the procedure. It is emphasized that the present invention is not limited to detection and location of mandibular canal 38. Other uses, including but not limited to detection and location of other types of human hard tissue, in addition to animal hard tissue, are also included within the scope of the present invention.

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  • Dental Tools And Instruments Or Auxiliary Dental Instruments (AREA)

Abstract

Systems for ascertaining proximity of an oral surgical instrument to a mandibular canal and methods of protecting a mandibular canal from damage during an oral surgical procedure are disclosed. The method includes transmitting (130) acoustic energy into canal (38), collecting (132) data pertaining to the acoustic energy using ultrasonic receiver (108) and stopping progress of drill (70) when collected data reaches a predetermined limit. Stopping may be by issuing (140) a warning. Disclosed systems include ultrasonic transmitter (106), pulser (104), ultrasonic receiver (108), amplifier (110) and indicator (114). System (100) further includes comparator (112) to evaluate received data according to a predetermined rule. Disclosed system (200) further includes analog to digital converter (202) and central processor (CPU) (204).

Description

SYSTEMS FOR ASCERTAINING PROXIMITY OF AN ORAL SURGICAL INSTRUMENT TO A MANDIBULAR CANAL AND METHODS OF PROTECTING A MANDIBULAR CANAL FROM DAMAGE DURING AN ORAL SURGICAL PROCEDURE
FIELD AND BACKGROUND OF INVENTION
The present invention relates to systems for ascertaining proximity of an oral surgical instrument to a mandibular canal and to methods of protecting a mandibular canal from damage during an oral surgical procedure. It is now common practice to replace a tooth with an implant-supported prosthesis. Placement of the implant to support the prosthesis entails exposing the jawbone (raising the mucoperiosteal flap), and drilling a receptive site for the fixture.
The possibility that the drill will enter and damage a mandibular canal during the drilling procedure is an inherent danger of this practice. Currently, there is no equipment or method available to reliably prevent entry of a drill into the mandibular canal. Practitioners are required to use their experience and instincts to know when to stop drilling. Skilled practitioners choose to err on the side of caution. As a result, implants are often mounted at less than the maximum achievable depth. This results in a weaker anchor for the subsequently installed prosthesis.
Practitioners typically rely on images of the jaw and mandibular canal prepared in advance to aid them in deciding how deep to drill as summarized hereinbelow.
The most common technique for preventing damage to the mandibular canal currently used in preparing an installation site for an implant is Panoramic X-ray Radiography. Panoramic X-Ray Radiography has several inherent disadvantages. First, it is well established that X-ray radiation is hazardous to the health of the patient. Second, Panoramic X-ray is inherently distorted and inaccurate because it projects the three-dimensional jaw into a two-dimensional image. It is therefore unreliable for assessing the depth of the bone tissue available for drilling a fixture socket. Third, the X-ray image is taken prior to (as opposed to during) the drilling procedure so that it does not portray a position of the drill relative to the mandibular canal during the procedure. All of these disadvantages make the panoramic X-ray image a hazardous, imprecise, and unreliable solution for protecting the mandibular canal during an oral surgical procedure.
Computerized Tomography (CT) is an available alternative to panoramic X- Ray. A CT image of the lower jaw provides a sectional view of the jaw, and is less distorted than panoramic X-Ray Radiography. However, CT involves a substantially higher dosage of X-ray radiation than conventional radiography, and therefore poses a significantly greater risk to the health of the patient. Further, CT equipment is expensive so that it is rarely found in a dental clinic. Finally, like Panoramic X-Ray, the CT image is typically taken prior to (as opposed to during) the drilling procedure so that it does not portray a position of the drill relative to the mandibular canal during the procedure. All of these disadvantages make CT imaging a hazardous, imprecise, and unreliable solution for protecting the mandibular canal during an oral surgical procedure. In summary, none of the available diagnostic imaging technology can provide a practitioner with an image of the drill in situ so that proximity to the mandibular canal may be gauged during the procedure.
There is thus a widely recognized need for, and it would be highly advantageous to have, systems for ascertaining proximity of an oral surgical instrument to a mandibular canal and methods of protecting a mandibular canal from damage during an oral surgical procedure devoid of the above limitation.
SUMMARY OF THE INVENTION
According to one aspect of the present invention there is provided a method of protecting a mandibular canal from damage during an oral drilling procedure. The method includes: (a) transmitting acoustic energy into the mandibular canal thereby causing the canal to function as an acoustic waveguide; (b) collecting data pertaining to a portion of the acoustic energy from a position outside the acoustic waveguide by means of an ultrasonic receiver; and (c) stopping progress of a drill when the portion of the energy reaches a predetermined limit.
According to another aspect of the present invention there is provided a system for ascertaining proximity of an oral surgical instrument to a mandibular canal. The system includes (a) an ultrasonic transmitter, the transmitter capable of transmitting acoustic energy into a mandibular canal, thereby causing the mandibular canal to act as an acoustic waveguide; (b) a pulser, the pulser capable of controlling a transmission from the transmitter; (c) an ultrasonic receiver, the receiver capable of receiving at least a portion of the energy transmitted by the transmitter; (d) an amplifier, the amplifier capable of amplifying the at least a portion of the energy received by the receiver; (e) a comparator, the comparator configured to execute an evaluation of the at least a portion of the energy received by the receiver according to a predetermined rule; and (f) an indicator, the indicator capable of communication with the comparator and designed and constructed display data pertaining to the evaluation to an operator of the system.
According to yet another aspect of the present invention there is provided a system for ascertaining proximity of an oral surgical instrument to a mandibular canal. The system includes: (a) an ultrasonic transmitter, the transmitter capable of transmitting acoustic energy into a mandibular canal, thereby causing the mandibular canal to act as an acoustic waveguide; (b) a pulser, the pulser capable of controlling a transmission from the transmitter; (c) an ultrasonic receiver, the receiver capable of receiving at least a portion of the energy transmitted by the transmitter; (d) an amplifier, the amplifier capable of amplifying the at least a portion of the energy received by the receiver; (e) an analog to digital converter designed and configured to convert the amplified at least a portion of the energy received by the receiver to a stream of digital data; (f) a central processor (CPU) designed and configured to analyze the stream of digital data according to a predetermined rule; and (g) an indicator, the indicator capable of communication with the CPU and designed and constructed display data pertaining to the evaluation to an operator of the system.
According to further features in preferred embodiments of the invention described below, the method further includes attaching the ultrasonic receiver and the drill one to the other.
According to still further features in the described preferred embodiments the method further includes processing the data pertaining to the portion of the acoustic energy to ascertain a parameter selected from the group consisting of an amplitude, a wavelength and a frequency of the portion of the acoustic energy. According to still further features in the described preferred embodiments the system further includes the oral surgical instrument.
According to still further features in the described preferred embodiments the oral surgical instrument is a drill.
According to still further features in the described preferred embodiments the system further includes a controller designed and configured to operate the oral surgical instrument in accord with a signal received from the comparator.
According to still further features in the described preferred embodiments the oral surgical instrument and the ultrasonic receiver are attached one to the other. According to still further features in the described preferred embodiments the comparator compares at least one data item selected from the group consisting of an amplitude, a wavelength and a frequency of the portion of the acoustic energy to a predetermined value.
According to still further features in the described preferred embodiments the CPU is further designed and configured to operate the oral surgical instrument in accord with a result of an analysis of the stream of digital data.
According to still further features in the described preferred embodiments the CPU analyzes a digital data stream representing at least one data item selected from the group consisting of an amplitude, a wavelength and a frequency of the portion of the acoustic energy with respect to a predetermined value.
The present invention successfully addresses the shortcomings of the presently known configurations by providing systems for ascertaining proximity of an oral surgical instrument to a mandibular canal and methods of protecting a mandibular canal from damage during an oral surgical procedure. The present invention has, as an inherent advantage, the ability to provide relative positional information about the location of a surgical instrument during a procedure.
Implementation of the method and system of the present invention involves performing or completing selected tasks or steps manually, automatically, or a combination thereof. Moreover, according to actual instrumentation and equipment of preferred embodiments of the method and system of the present invention, several selected steps could be implemented by hardware or by software on any operating system of any firmware or a combination thereof. For example, as hardware, selected steps of the invention could be implemented as a chip or a circuit. As software, selected steps of the invention could be implemented as a plurality of software instructions being executed by a computer using any suitable operating system. In any case, selected steps of the method and system of the invention could be described as being performed by a data processor, such as a computing platform for executing a plurality of instructions. BRIEF DESCRIPTION OF THE DRAWINGS
The invention is herein described, by way of example only, with reference to the accompanying drawings. With specific reference now to the drawings in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the preferred embodiments of the present invention only, and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice.
In the drawings: FIG. 1 is a diagrammatic representation of a mandible including teeth and a mandibular canal;
FIG. 2 is a diagrammatic representation of a portion of a mandible as in figure 1 illustrating insertion of a surgical implement therein;
FIG. 3 is a simplified schematic diagram of components of a system according to the present invention;
FIG. 4 is a flow diagram illustrating steps in a method according to the present invention employing the system of figure 3;
FIG. 5 illustrates placement of probes on a mandible in conjunction with practice of the present invention; FIGs. 6A and 6B illustrate the relationship between distance (d) and amplitude (A) according to the present invention;
FIG. 7 is a simplified schematic diagram of components of an additional system according to the present invention;
FIG. 8 is a flow diagram illustrating steps in a method according to the present invention employing the system of figure 7;
FIG. 9 is a simplified schematic diagram of components of another additional system according to the present invention; and
FIG. 10 is a flow diagram illustrating steps in a method according to the present invention employing the system of figure 9. DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention is of systems for ascertaining proximity of an oral surgical instrument to a mandibular canal and is further of methods of protecting a mandibular canal from damage during an oral surgical procedure. The present invention can be employed to insure that a surgical instrument, such as a drill, does not damage a mandibular canal or an inferior alveolar nerve. Specifically, the present invention can be used to reliably and safely allow implantation of an anchor for a dental prosthesis deep within the trabecular bone of the jaw without endangering the mandibular canal.
Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments or of being practiced or carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein is for the purpose of description and should not be regarded as limiting.
For purposes of better understanding the present invention, as illustrated in figures 3-10 of the drawings, reference is first made to the structure of the mandible and insertion of a drill therein as illustrated in figures 1 and 2.
Referring to figure 1, the anatomy of the lower jaw, or mandible 30, is briefly described. Mandible 30 includes several layers of tissue. Mandible 30 features an external layer of mucoperiosteal tissue (gums 32) covering the jawbone. Beneath gums 32 is a layer of cortical (compact) bone 34, which is normally characterized by a high density. Beneath cortical bone 34 lies trabecular bone 36 which is typically softer than cortical bone 34. Within trabecular bone 34, and along a longitudinal aspect of mandible 30, mandibular canal 38 resides and contains inferior alveolar nerve 39.
Mandibular canal 38 is an elongated tubular cavity, typically bordered by cortical bone 34. In cases where dense borders are not present, mandibular canal 38 is a conduit within a sponge-like matrix. In the latter case, mandibular canal cavity 38 may be distinguished from the cavities of the trabecular environment 36 by the mandibular canal's regular shape (i.e. an elongated tubular cavity). All cavities inside the cross-section of mandible 30 are normally filled with fluids. The upper region of mandible 30 forms the alveolar ridge 40 in which teeth 42 are normally situated. Referring now to FIG. 2, the common procedure prior to installation of a dental fixture typically includes drilling into cortical bone 34 and trabecular bone 36 of mandible 30 using a drill 70, in order to prepare a socket in which a fixture may be anchored. If a practitioner drilling into mandible 30 is not aware of the precise location of mandibular canal 38, then during the drilling procedure drill 70 may contact and damage inferior alveolar nerve 39. Such damage typically causes severe pain and hemorrhage and has been known to induce local paralysis. For this reason, it is universally agreed that a practitioner must be able to cease drilling prior to damaging the mandibular canal. The present invention is offered to provide a reliable and effective means to assure that progress of a surgical instrument, such as a drill, towards a mandibular canal is stopped before damage to the canal occurs. The present invention is thus embodied by a method 120 (figure 4) of protecting a mandibular canal from damage during an oral drilling procedure. The method includes transmitting 130 acoustic energy into the mandibular canal thereby causing the canal to function as an acoustic waveguide. This transmission is preferably accomplished by an emitting probe 106. Preferably probe 106 is coupled to a pulser 104 operably connected to a controller 102. Alternately, probe 106 may be connected directly to controller 102. Transmitting 130 may be accomplished, for example, by coupling 122 emitting probe 106 to a patient, activating 124 pulser 104 (e.g. by means of controller 102), Generating 176 an electric signal and converting 128 the electric signal to an acoustic signal. The result of these actions is to transform mandibular canal 38 into an acoustic waveguide.
Method 120 further includes collecting or receiving 132 data pertaining to a portion of the acoustic energy from a position outside the acoustic waveguide by means of an ultrasonic receiver 108 and stopping progress of drill 70 when the portion of the energy reaches a predetermined limit. Stopping progress of drill 70 may be accomplished, for example, by issuing 140 a warning. The warning may be, for example, a visible indicator, an audible signal or a tactile stimulus. In order to make method 120 more efficient, it is preferable to attach ultrasonic receiver 108 to drill 70 or to integrally form these two components of system 100 together.
In order to determine when it is appropriate to issue 140 warning on indicator 114, energy received 132 by probe 108 may be converted 134 to an electric signal which is optionally, but also preferably, amplified 136 by amplifier 110. This facilitates comparison 138 by means of comparator 112. In figures 3 and 4, a measured amplitude An is compared to a predetermined maximum amplitude (Amax). When An exceeds Amax indicator 114 issues 140 a warning. While amplitude corresponding to a portion of the acoustic energy received at probe 108 outside of canal 38 is used in this example, wavelength or frequency may also be employed without significantly affecting practice of method 120. The relative position of transmitter 106 and receiver 108 in the context of mandible 30 is illustrated in figure 5. The relationship between a distance (d) between transmitter 106 and receiver 108 and A is diagrammed in figures 6a and 6b. It will be appreciated that it is theoretically possible for probe 108 to function as a transmitter and probe 106 to function as a receiver. However, this would result in less energy being channeled through waveguide 38 and therefore require greater amplification 136.
The present invention is further embodied by system 100 for ascertaining proximity of an oral surgical instrument to a mandibular canal. System 100 includes an ultrasonic transmitter 106 capable of transmitting 130 acoustic energy into mandibular canal 38, thereby causing the mandibular canal to act as an acoustic waveguide. System 100 further includes a pulser 104 capable of controlling transmission 126 from transmitter 106 either alone or in combination with controller 102. System 100 further includes ultrasonic receiver 108 capable of receivingl32 at least a portion of the energy transmitted by transmitter 106. System 100 further includes amplifier 100 capable of amplifying 136 the at least a portion of the energy received 132 by receiverlOδ. Preferably, amplification 136 occurs after conversion 134 of the energy to electric energy. System 100 further includes comparatorll2 configured to execute an evaluation of the at least a portion of the energy received 132 by receiver 108 according to a predetermined rule. The rule may be, for example, a comparison of A„ to Amax as detailed hereinabove. System 100 further includes indicator 114 capable of communication with comparator 112 and designed and constructed display data pertaining to the evaluation to an operator of the system. According to one preferred embodiment of the invention indicator 114 and drill 70 are functionally combined. According to this embodiment, issuing 140 of a warning includes interruption of a power supply to drill 70. System 100 preferably further includes a controller (e.g. 102) designed and configured to operate oral surgical instrument 70 in accord with a signal received from the comparator 112. In this case, drill 70 functions as indicator 114 and cessation of the motor of drill 70 serves as the warning. Therefore, it is preferable for system 100 to include the oral surgical instrument, for example drill 70. This configuration functions optimally when oral surgical instrument 70 and ultrasonic receiver 108 are attached one to the other or integrally formed together.
The present invention is further embodied by a system 200 (figure 7) for ascertaining proximity of oral surgical instrument 70 to a mandibular canal 38. Use of system 200 constitutes an additional method 220 (figure 8) according to the present invention. System 200 includes ultrasonic transmitter 106, pulser 104, receiver 108 and amplifier 110 each as described hereinabove. System 200 further includes an analog to digital converter (ADC) 202 designed and configured to convert the amplified at least a portion of the energy received by the receiver to a stream of digital data and a central processor (CPU) 204 designed and configured to analyze the stream of digital data according to a predetermined rule (e.g. threshold value 204'). Like system 100, system 200 includes indicator 114. Because of the differences between system 100 and 200 indicator 114 is, in this case, capable of communication with CPU 204 and designed and constructed display data pertaining to analysis with respect to rule 204' to an operator of system 200. Preferably, CPU 204 is further designed and configured to operate oral surgical instrument 70 in accord with a result of an analysis of the stream of digital data. This operation may require additional inputs either prior to onset of operation or during operation of system 200. These inputs may be, for example, in the form of programmed instructions, or direct operator input including, but not limited to, keyboard input, voice commands, joystick input, touch screen input, menu selections or inputs from other mechanical or electronic control devices. CPU 204 may analyze, for example, a digital data stream representing an amplitude, a wavelength or a frequency of the portion of the acoustic energy with respect to a predetermined value 204'. Thus, method 220 (figure 8) is similar to method 120 as described hereinabove except that received 132 acoustic signal is first converted 134 to an electric signal, then amplified 136 and then converted 222 a second time to a digital signal with a value V. Thus in method 220, comparison 224 is between Vn and Vmax (i.e. predetermined value 204') instead of between An and Amax as in method 120 detailed hereinabove.
Thus, according to the various embodiments of the invention, it is preferable for controller 102 to be coupled to pulser 104, which is coupled to emitting probe 106. Receiving probe 108 is preferably coupled to amplifier 110, which is coupled to either comparator 112 or ADC 202/CPU204, which is coupled to indicator 114. Controller 102 includes means for controlling the operation of pulser 104, for example, an on/off switch and preferably additional adjustable elements enabling the user to determine pulse frequency, voltage, and duration, as well as other relevant parameters. Pulser 104 is operable to generate electric pulses based on parameters set by controller 102. Emitting probe 106 is operative to convert electric pulses into analog acoustic (mechanical) pulses. Preferably, emitting probe 106 includes a wideband piezoelectric transducer, although any other known type of emitting transducer is also within the scope of the present invention.
Receiving probe 108 is operative to convert acoustic pulses into analog electric pulses. Preferably, receiving probe 108 includes a wideband hydrophone transducer, although any other known type of receiving transducer is also within the scope of the present invention. Both probes 106 and 108 are preferably biocompatible, meaning that they can be safely placed in contact with a living organism, especially inside the mouth of a patient. Furthermore, receiving probe 108 is preferably small enough in diameter (e.g. 3 mm or less) to fit inside the fixture socket drilled by drill 70. For example, a hydrophone transducer may be used for this purpose. Amplifier 110 is operative to amplify electric pulses to a predefined level or by a predefined factor. Comparator 112 is operative to receive amplified electric pulses and to compare their amplitude to a predetermined threshold amplitude Amax. The threshold amplitude can be hardwired (i.e. a permanent threshold amplitude), or preferably, it can be controlled and changed by the user using a threshold amplitude control element 112' (i.e. an adjustable threshold amplitude). When the comparator detects that the input amplitude A„ exceeds the threshold amplitude Amax, it sends a message, such as an electric signal, to indicator 114. Indicator 114 includes at least one means for notifying an operator of the system that the predetermined threshold has been met, for example, a light-emitting diode (LED) that emits red light, a cathode-ray tube (CRT) that displays a warning message, a buzzer that produces a warning sound, or any other known indicator. As detailed hereinabove, cessation of a motor of drill 70 preferably serves as the means for notifying an operator. Referring again to figures 4 and 5, a preferred method 120 of operation of system 100 is described in greater detail. According to method 120, an operator of system 120 couples 122 emitting probe 106 to a first location 51 on mandible 30, and receiving probe 108 to a second location 52 thereon (step 122). Either or both locations can be on a surface inside the mouth cavity, such as the buccal or lingual gum surface, or outside the mouth cavity, such as the skin surface of the cheek or chin. Alternatively, in case the jawbone is exposed (e.g. by raising the mucoperiosteal flap) either or both probes can be coupled directly to a bone surface (cortical or trabecular) of the mandible. Preferably, the operator couples 122 emitting probe 106 to a location that is assumed or known (e.g. empirically) to maximize penetration of acoustic emission into mandibular canal 38, for example, on the buccal gum surface covering the anterior opening 381 of the mandibular canal. Normally, in an adult patient, anterior opening 381 is situated a few millimeters below and between the roots of the second bicuspid and first molar teeth (on either side of the mouth). Preferably, the operator couples 122 receiving probe 108 to the alveolar ridge that is covering the implant site being prepared, whilst facing downwards (toward the mandibular canal). In case drilling has already been performed in the implant site, probe 108 will be placed inside the drilled socket, again facing downwards (toward the mandibular canal). Alternatively, the user may swap the locations of the emitting and receiving probes, so that emitting probe 106 is coupled to the implant or drilling site whilst receiving probe 108 is coupled facing the anterior opening of the mandibular canal.
In order to improve transmission 130 and reception 132 of acoustic signals to and from mandible 30, a coupling material is preferably applied between each probe (106 and 108) and the jaw surface. In some cases, the fluids present in the mouth of the patient (e.g. saliva, blood, drill cooling water) will sufficiently serve this purpose. In other cases, a commercially available non-toxic ultrasound coupling gel or similar composition may be employed.
It is a particular teaching of the present invention, that when an acoustic signal is emitted toward the mandibular canal, mandibular canal 38 will serve as a waveguide for the signal (as illustrated in figure 5). This phenomenon occurs for two reasons. First, mandibular canal 38 is normally filled with nerves, blood vessels and other soft or fluid tissues which possess more favorable acoustic properties (e.g. lower attenuation) than the surrounding bone tissue. Second, the mandibular canal's 38 tube-like bone tissue borders cause acoustic waves to be repeatedly reflected from the internal walls of the canal, and hence to propagate along and inside the canal.
When the probes 106 and 108 are properly coupled, the operator adjusts the pulse parameters and activates 124 pulser 104 using controller 102. Pulser 104 generates an electric signal based on the provided parameters and sends the signal to emitting probe 106 (step 126). Emitting probe 106 converts 128 the electric signal to an acoustic signal, for example, a wideband ultrasonic pulse at a frequency range of approximately 1 to 3 MHz. The acoustic signal is then emitted 130 toward mandibular canal 38. Part of the energy of the emitted signal penetrates the border between the emitting probe and mandible 30. Part of the energy of the penetrating signal travels toward anterior opening 381, and then continues to propagate inside mandibular canal 38. On each encounter between the signal and the internal walls of mandibular canal, reflection and refraction of the signal occur (represented by broken arrows in FIG. 5). Eventually, some of the reflected and refracted energy of the acoustic signal is received 132 at the implant site by receiving probe 108. In case emitting probe 106 is coupled to the implant or drilling site and receiving probe 108 is coupled facing the anterior opening 381 of mandibular canal 38, the emitted signal will travel through a similar path but in the opposite direction.
Receiving probe 108 converts 134 the received acoustic signal to an analog electric signal. Amplifier 110 amplifies 136 the electric signal and sends it to comparator 112. Comparator 112 compares 138 the amplitude of the signal An to the predetermined threshold amplitude Amax. As detailed hereinabove, the predetermined threshold amplitude can be permanent, or preferably, adjustable. If adjustable, the operator will set a desired threshold amplitude using control element 112' at any time prior comparison 138. It is well known that the degree of attenuation of an acoustic signal is correlated to its travel distance (d). In particular, the greater the distance an acoustic signal travels through a medium which causes attenuation (e.g. bone tissue), the more energy it loses and the more its amplitude decreases (see figures 6A and 6B). During the socket preparation procedure, the practitioner performs the steps of method 120 repeatedly, after every desired depth is drilled (e.g. every 1 mm). As drill 70 approaches mandibular canal 38, the acoustic travel distance d from emitting probe 106 to receiving probe 108 is shortened. This causes amplitude of the signal received 132 by receiving probe 108 to increase. Referring to FIG. 6 A, in the beginning of the implant socket drilling procedure, a first distance dι between mandibular canal 38 and the bottom of the socket, correlates to a first amplitude A] received by receiving probe 108: d AX
After drill 70 penetrates deeper down the socket, a second distance d2 between mandibular canal 38 and the socket correlates to a second received amplitude A2: d2 κ A2
Since the socket is now deeper and closer to mandibular canal 38, the first distance is shorter than the second distance: dλ > d2
and accordingly, the second amplitude is greater than the first amplitude:
A, > A,
Referring again to figure 4, comparison 138 by comparator 112 ascertains whether or not received amplitude An is greater than the predetermined threshold amplitude Amax. As long as An is less than or equal to Amax, system 100 will continue to generate electric signal 126 without issuing 140 any warning to the operator. As soon as An exceeds threshold amplitude Amax, comparator 112 sends an electric signal to indicator 114 which immediately indicates to the user that any further drilling may be too close to mandibular canal 38 by issuing warning 140. As indicated, cessation of generation 126 of electric signal may accompany the warning.
Figure 7 depicts, an alternate system 200 according to the present invention which is partially similar to system 100. In order to highlight the similarity between systems 100 and 200, common elements are labeled with the same reference numerals. System 200 includes a controller 102, a pulser 104, an emitting probe 106, a receiving probe 108, an amplifier 110, and an indicator 114, all similar to those described hereinabove with reference to system 100. Unlike system 100, system 200 does not include a comparator 112. Instead, the comparison function is performed by an analog-to-digital converter (ADC) 202, and a processor 204. In system 200, controller 102 is coupled to pulser 104, which is coupled to emitting probe 106. Receiving probe 108 is coupled to amplifier 110, which is coupled to ADC 202. ADC 202 is coupled to processor 204, which is coupled to indicator 114. ADC 202 comprises a conventional analog-to-digital converter that is operable to convert an analog electric signal into a stream of digital samples or readings, at a predetermined sampling rate (e.g. 40 MHz). Processor 204 comprises digital computing means, for example, a conventional IBM-compatible PC. Processor 204 is operable to receive from ADC 202 a stream of digital samples representing the received acoustic signal, and to compare each sample value Vn to a predetermined threshold value Vmax. The threshold value, preferably, can be controlled and changed by the user (i.e. an adjustable threshold value) using a threshold value control element 204'. Alternatively, the threshold value can be hardwired (i.e. a permanent threshold value) in the electronic circuitry of processor 204. When processor 204 detects that a value of an incoming digital sample V„ exceeds the given threshold value Vmax, it sends a message, such as an electric signal, to indicator 114. In system 200, indicator 114 may be as described hereinabove with respect to apparatus 100. Preferably indicator 114 of system 200 further includes a computer monitor capable of communication with processor 204.
Operation of system 200 constitutes a method 220 which is similar to method 120 described hereinabove and common actions are therefore denoted with the same reference numerals. Thus, steps 122 through 136 of method 220 are identical to these steps in method 120 described hereinabove. After the received electric signal is amplified 136, the signal is converted 222 by ADC 202, at a predetermined sampling rate, into a stream of digital samples. ADC 202 sends the digital samples representing the received acoustic signal, to processor 204. Processor 204 executes 224 a first algorithm (e.g. computer executable code, software code, etc.) for comparing the digital value of each incoming sample Vn to the predetermined threshold value Vmax. The first algorithm can be any known algorithm for comparing each value in a series of digital values to a predetermined value. As detailed hereinabove, the predetermined threshold value can be permanent, or preferably, adjustable. If adjustable, the user will set the desired threshold value using control element 204' at any time prior to execution 224 of the first algorithm. During the socket preparation procedure, the practitioner performs the steps of method 220 repeatedly, after every desired depth is drilled (e.g. every 1 mm). As the practitioner drills nearer to mandibular canal 38, the acoustic travel distance from emitting probe 106 to receiving probe 108 is shortened; and as the acoustic travel distance shortens, the amplitude of the signal received by receiving probe 108 increases. As the amplitude of the received signal increases, so does the value Vn of the samples representing the signal. As long as V„ is less than or equal to threshold value Vmax, meaning that a safe distance between the bottom of the drilled socket and mandibular canal 38 is being kept, system 200 will continue to generate 126 an electric signal without issuing 140 any warning to the operator. As soon as Vn exceeds threshold value Vmax, processor 204 sends an electric signal to indicator 114 which immediately indicates 140 to the user that any further drilling is too close to mandibular canal 38. Figure 9 depicts an additional system 300 according to the present invention.
System 300 includes the same elements as apparatus 200, except that instead of a threshold value control element 204' apparatus 300 comprises a threshold central frequency control element 204". In apparatus 300, processor 204 is operable to receive from ADC 202 a stream of digital samples representing the received acoustic signal, to produce a frequency domain of the signal, to find the central frequency , in the frequency domain of the signal, and to compare the central frequency to a predetermined threshold central frequency fmax. The threshold central frequency, preferably, can be controlled and changed by the user (i.e. an adjustable threshold central frequency) using threshold central frequency control element 204". Alternatively, the threshold central frequency can be hardwired (i.e. a permanent threshold central frequency) in the electronic circuitry of processor 204. When processor 204 detects that the central frequency/ of the received acoustic signal exceeds the given threshold central frequency/,^, it sends a message, such as an electric signal, to indicator 114. Figure 10 depicts a method 320 of operation of apparatus 300 according to the present invention. Method 320 is partially similar to method 220 common portions of the method are denoted with the same reference numerals. Thus, steps 122 through 222 of method 320 are identical to these steps in method 220 described hereinabove. Following conversion 222 of electric signal, processor 204 executes a second algorithm, such as a known FFT (fast Fourier transform) algorithm, for producing 322 a frequency domain (e.g. an array of amplitudes per frequency) of the digital samples received from the ADC. Next, processor 204 executes a third algorithm for finding 324 the central frequency fmax in the frequency domain of the received acoustic signal, i.e. the frequency around which most of the energy of the received signal is concentrated. Such algorithms are known in the art and one of ordinarily skill will be able to incorporate them into the context of the present invention. Processor 204 further executes 326 a fourth algorithm for comparing the central frequency/ to the predetermined threshold central frequency/,^. The fourth algorithm can be any known algorithm for comparing two digital values. As detailed hereinabove, the predetermined threshold central frequency 204"can be permanent, or preferably, adjustable. If adjustable, the user will set the desired threshold frequency using control element 204" at any time prior operation 326.
It is well known that the degree of attenuation of an acoustic signal correlates to certain changes in the frequency domain of the signal. In particular, the greater the distance an acoustic signal travels through a medium which causes attenuation (e.g. bone tissue), the lower the central frequency of the signal. During the socket preparation procedure, the practitioner performs the steps of method 320 repeatedly, after every desired depth is drilled (e.g. every 1 mm). As the practitioner drills nearer to mandibular canal 38, the acoustic travel distance d from emitting probe 106 to receiving probe 108 is shortened; and as d shortens, the central frequency/ in the frequency domain of the signal received by receiving probe 108 increases. As long as/ is less than or equal to threshold central frequency/,^, a safe distance between the bottom of the drilled socket and mandibular canal 38 remains and system 300 will return to generation 126 of electric signal without issuing 140 any warning to the operator. As soon as/ exceeds threshold frequency/,^, processor 204 sends an electric signal to indicator 114 which immediately indicates 140 to the operator that any further drilling is too close to mandibular canal 38.
According to yet another alternative embodiment of the present invention, an oral surgical instrument, for example drill 70 used for drilling a receptive socket for a dental implant, is included in system 100, 200 or 300 as described hereinabove. According to this embodiment of the invention either emitting probe 106 or receiving probe 108 is mounted on oral surgical instrument 70, preferably on the distal tip of the bit and facing mandibular canal 38. The method of operation according to this embodiment is similar to the method of operation of systems 100, 200 or 300, respectively. This embodiment is preferred because providing a surgical tool 70 on which one of probes 106 or 108 is mounted eliminates the need to stop the surgical procedure (e.g. stop drilling into the jawbone) before each comparison of a determined data value to a threshold data value. Instead, determined data values are constantly compared to the threshold value as work proceeds, resulting in a continuous workflow until issue 140 of a warning.
Thus, it is evident that the present invention provides accurate, safe, radiation-free, and economical method and apparatus for detection and location of mandibular canal 38 in situ during an oral surgical procedure, preferably without interruption of the procedure. It is emphasized that the present invention is not limited to detection and location of mandibular canal 38. Other uses, including but not limited to detection and location of other types of human hard tissue, in addition to animal hard tissue, are also included within the scope of the present invention.
It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable subcombination.
Although the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims. All publications, patents and patent applications mentioned in this specification are herein incorporated in their entirety by reference into the specification, to the same extent as if each individual publication, patent or patent application was specifically and individually indicated to be incorporated herein by reference. In addition, citation or identification of any reference in this application shall not be construed as an admission that such reference is available as prior art to the present invention.

Claims

WHAT IS CLAIMED IS:
1. A method of protecting a mandibular canal from damage during
an oral drilling procedure, the method comprising:
(a) transmitting acoustic energy into the mandibular canal thereby
causing the canal to function as an acoustic waveguide;
(b) collecting data pertaining to a portion of said acoustic energy
from a position outside said acoustic waveguide by means of an ultrasonic
receiver; and
(c) stopping progress of a drill when said portion of said energy
reaches a predetermined limit.
2. The method of claim 1, further comprising attaching said
ultrasonic receiver and said drill one to the other.
3. The method of claim 1, further comprising processing said data
pertaining to said portion of said acoustic energy to ascertain a parameter
selected from the group consisting of an amplitude, a wavelength and a
frequency of said portion of said acoustic energy.
4. A system for ascertaining proximity of an oral surgical
instrument to a mandibular canal, the system comprising: (a) an ultrasonic transmitter, said transmitter capable of transmitting
acoustic energy into a mandibular canal, thereby causing the mandibular canal
to act as an acoustic waveguide;
(b) a pulser, said pulser capable of controlling a transmission from
said transmitter;
(c) an ultrasonic receiver, said receiver capable of receiving at least a
portion of said energy transmitted by said transmitter;
(d) an amplifier, said amplifier capable of amplifying said at least a
portion of said energy received by said receiver;
(e) a comparator, said comparator configured to execute an
evaluation of said at least a portion of said energy received by said receiver
according to a predetermined rule; and
(f) an indicator, said indicator capable of communication with said
comparator and designed and constructed display data pertaining to said
evaluation to an operator of the system.
5. The system of claim 4 further comprising the oral surgical
instrument.
6. The system of claim 5, wherein the oral surgical instrument is a
drill.
7. The system of claim 5, further comprising a controller designed
and configured to operate said oral surgical instrument in accord with a signal
received from said comparator.
8. The system of claim 5, wherein the oral surgical instrument and
said ultrasonic receiver are attached one to the other.
9. The system of claim 4, wherein said comparator compares at least
one data item selected from the group consisting of an amplitude, a wavelength
and a frequency of said portion of said acoustic energy to a predetermined
value.
10. A system for ascertaining proximity of an oral surgical
instrument to a mandibular canal, the system comprising:
(a) an ultrasonic transmitter, said transmitter capable of transmitting
acoustic energy into a mandibular canal, thereby causing the mandibular canal
to act as an acoustic waveguide;
(b) a pulser, said pulser capable of controlling a transmission from
said transmitter;
(c) an ultrasonic receiver, said receiver capable of receiving at least a
portion of said energy transmitted by said transmitter;
(d) an amplifier, said amplifier capable of amplifying said at least a
portion of said energy received by said receiver; (e) an analog to digital converter designed and configured to convert
said amplified at least a portion of said energy received by said receiver to a
stream of digital data;
(f) a central processor (CPU) designed and configured to analyze
said stream of digital data according to a predetermined rule; and
(g) an indicator, said indicator capable of communication with said
CPU and designed and constructed display data pertaining to said evaluation to
an operator of the system.
1 1. The system of claim 9 further comprising the oral surgical
instrument.
12. The system of claim 11, wherein the oral surgical instrument is a
drill.
13. The system of claim 11, wherein said CPU is further designed
and configured to operate said oral surgical instrument in accord with a result
of an analysis of said stream of digital data.
14. The system of claim 10, wherein the oral surgical instrument and
said ultrasonic receiver are attached one to the other.
15. The system of claim 10, wherein said CPU analyzes a digital data
stream representing at least one data item selected from the group consisting of
an amplitude, a wavelength and a frequency of said portion of said acoustic
energy with respect to a predetermined value.
PCT/US2002/033718 2001-11-06 2002-10-23 Systems for ascertaining proximity of an oral surgical instrument to a mandibular canal and methods of protecting a mandibular canal from damage during an oral surgical procedure WO2003039389A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US33100401P 2001-11-06 2001-11-06
US60/331,004 2001-11-06

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US10799210B1 (en) 2017-09-01 2020-10-13 S-Ray Incorporated Dental imaging apparatus and method

Citations (2)

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Publication number Priority date Publication date Assignee Title
US5304214A (en) * 1992-01-21 1994-04-19 Med Institute, Inc. Transurethral ablation catheter
US5846081A (en) * 1995-08-23 1998-12-08 Bushway; Geoffrey C. Computerized instrument platform positioning system

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5304214A (en) * 1992-01-21 1994-04-19 Med Institute, Inc. Transurethral ablation catheter
US5846081A (en) * 1995-08-23 1998-12-08 Bushway; Geoffrey C. Computerized instrument platform positioning system

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US10799210B1 (en) 2017-09-01 2020-10-13 S-Ray Incorporated Dental imaging apparatus and method

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