JP2014507194A - Dental installation quality inspection device - Google Patents

Abstract

  The present invention relates to a method and apparatus for inspecting the quality of attachment between crowns (11) attached to the surface of teeth (14; 17). This method comprises: detecting at least one resonance frequency of the member (16, 20, 21, 31) in contact with the crown (11); and detecting the degree of attachment of the crown to the tooth Interpreting the resonant frequency.

Description

  The present invention relates to a method and apparatus for examining the mounting quality of a dental crown, in particular a dental bridge crown attached to a patient or patient's teeth.

  A dental bridge is a restoration of a tooth that is used in place of a missing tooth. These are excellent replacements for dentures and dental implants, provide greater stability than dentures, and the procedure is less invasive than the treatment of dental implants. A dental bridge is one method used by dentists to fill gaps formed by one (or more) missing teeth. Installation procedures and costs vary depending on the type of dental bridge.

  Referring now to FIG. 1, the dental bridge 10 is typically composed of two crowns 11 for the teeth on both sides of the gap 12 and an intermediate denture or prosthetic tooth 13. Natural teeth 14 and 15, dental implants, or a combination of natural teeth and dental implants are used to support the bridge 10.

  During the initial treatment, the dentist may scrape the teeth on both sides of the gap left by the missing tooth. Once the teeth are fully prepared, the tooth mold, ie the impression, is taken and the custom built bridge and crown are produced. Finally, temporary crowns and bridges are placed to protect the patient's teeth and gums from further damage.

  Most patients revisit the dentist about a week after the initial appointment and have a permanent restoration placed. The dentist uses cement or adhesive to hold the crown and bridge in place, and then polishes the restoration's cusp to provide a comfortable bite to the patient.

  Dental bridge treatment is an effective measure for patients with several missing teeth, but there are some risks and limitations associated with this treatment.

  One important risk is the attachment of the crown to the surrounding teeth. Loose contact between the crown and teeth increases the risk of caries. The most common reason for replacement of a fixed bridge is caries, that is, phagocytosis of the underlying tooth structure. Once any abutment tooth of a bridge has caries, at least three crowns, the entire bridge, must be replaced. Often, abutment teeth also require further treatment such as pulp capping, abutment construction, crown length extension or root canal treatment.

  Implant quality inspection devices are well known, for example, from US Pat. No. 5,392,779 and International Patent Publication No. WO 2004/110272. However, these inventions relate to measuring the stability of an implant inserted into the bone and not to measure the attachment quality between the crown and teeth.

  For this reason, it is necessary to detect whether there is a problem in the attachment between the crown, especially the dental bridge of the dental bridge.

  For this reason, there is a need for a method and mechanism for clinical observation of the quality of attachment between the crown and the tooth surface. Non-destructive inspections help detect and reduce this type of failure and perform periodic inspections to ensure that they are still complete with regard to the installation of bridges being used It also makes it possible.

  Accordingly, it is an object of the present invention to provide a non-destructive test that can provide a reliable indicator of the quality and / or degree of attachment between a crown and the tooth to which the crown is attached.

  Thus, a method is provided for examining the attachment quality between crowns attached to tooth surfaces (and / or teeth attached to implants). The method includes detecting at least one resonance frequency of a member in contact with the crown; and interpreting the detected resonance frequency in terms of the degree of attachment between the crown and the tooth. The method may include the step of detachably attaching the member to the crown or a component attached thereto. The member may comprise a cantilever. The beam may be attached to the crown or a component connected to the crown through a screw hole. The beam may be attached to the crown or a component connected to the crown by an adhesive. The member may be incorporated into the crown or a part attached thereto.

  The method may include comparing the detected resonance frequency with one or more values of the resonance frequency of the same or similar member from a previous measurement. The method includes exciting the member with an AC signal, detecting a response of the member to the AC signal, and varying the frequency of the AC signal until the detected response of the member is maximized. A process. The method may further include deriving an output that is a ratio of the voltage of the response signal to the voltage of the excitation signal. This method also means that the member is pulse-excited, the response is detected, and the frequency of the response signal is analyzed. Preferably, the measurement is non-contact.

  The present invention also relates to a crown mounting quality inspection device. The apparatus comprises a detector for detecting at least one resonance frequency of the member when the member is attached to the crown. The detector for detecting at least one resonance frequency of the member comprises means for exciting the member with an AC signal and a converter for detecting a response of the member to the AC signal. Well, this device varies the frequency of the AC signal so that the transducer detects when the response of the member is maximized. The excitation means and / or detector may comprise a piezoelectric element, the piezoelectric element comprising excitation means driven by a variable frequency oscillator. The member includes a detectable portion, and the detector portion includes a detector for non-contact detection of the detectable portion.

  According to one embodiment, the member may comprise a magnetic part and the detector may comprise a coil.

  According to one embodiment, the member may comprise a marker and the detector may comprise an illuminance detector.

  According to one embodiment, the member may comprise a ferromagnetic material and the detector may comprise a coil for detecting disturbances in an external magnetic field.

  The apparatus may further comprise an amplifier, a processor, and a data storage device. The processor is further configured to vary the frequency output of the oscillator and stores the result in the data storage device. At least one coil may be configured to output a magnetic pulse to the member attached to the member and detect a response corresponding to the magnetic pulse from the member.

  The invention will be further described, by way of example only, with reference to the accompanying drawings.

Schematic diagram of the dental bridge; Schematic of the device of the second embodiment according to the present invention; Schematic of the device of the second embodiment according to the present invention; Schematic of the device of the third embodiment according to the present invention; 1 is a schematic diagram of a dental bridge according to an embodiment of the present invention; Diagram obtained by the coarse sweep used to obtain the resonant frequency; A schematic showing the resonant frequency as a function of time for a particular bridge; and FIG. 4 is a diagram illustrating data obtained by sweeping used to obtain the resonant frequency of the apparatus of FIG.

  Referring to FIG. 2, which shows the first aspect of the present invention, the device includes a cantilever 20 attached to a fixture at an appropriate location on the bridge 10 (in this case, a denture), eg, by a thread or adhesive. It has a shaped member. The bridge may be any one of a number of well-known types. Two transducers, such as piezoelectric elements or strain gauges 21 and 22, are attached to, for example, bonded to the opposite side of the beam 20, the gauge 21 being an excitation gauge and the gauge 22 being a receiving gauge.

  The term “attachment” as used herein to indicate the connection between the measurable part and the crown / bridge includes incorporation inside the crown / bridge or attachment to the surface of the crown bridge. It should be interpreted broadly.

  The excitation gauge 21 may be driven by a variable frequency oscillator, and a signal from this oscillator, for example in the form of a sinusoidal excitation voltage, is supplied to the gauge 21 via an amplifier. The oscillator and amplifier may be incorporated into the frequency response analyzer 28.

  The signal detected by the reception gauge 22 is amplified by the charge amplifier 27 and applied to the analyzer 28 as an input. The output from the analyzer, which represents the ratio of the response voltage to the excitation voltage, is fed to a processor, such as a microprocessor 26, used to vary the frequency output of the analyzer 28 oscillator and store the result in the data store 29. The The result is printed and / or displayed on an oscilloscope 25 and / or an AC voltmeter or the like.

  In use, the beam 20 is fixed or screwed to the bridge 10. An AC excitation signal of constant amplitude, for example 1 volt, is then applied to the beam 20 by the gauge 21. The frequency of the AC excitation signal varies until the amplitude of the signal displayed on the oscilloscope 25 is maximized. The resonance frequency is a frequency at which the amplitude of the ratio of the response voltage to the excitation voltage is maximized.

  FIG. 6 shows the coarse sweep data used to roughly obtain the resonant frequency. A finer sweep around this region is then used to more accurately identify this frequency, generally the first frequency, ie the fundamental frequency. This frequency is recorded and compared with data on other bridges / crowns, for example, at similar adhesion stages.

  For a particular bridge installation, the resonant frequency varies with time, as shown in FIG. Thus, by comparing the detected resonant frequency with previously collected data for similar previous measurements, an indication of the degree of crown attachment to the tooth can be obtained.

  Techniques based on detection and comparison of resonance frequency shifts, not amplitude changes, to determine the quality of installation between the crown (s) and the tooth (s) as a function of their stiffness It is effective.

  The beam 20 shown in FIG. 2 is preferably made of a metal such as aluminum, stainless steel or titanium, and is in the range of about 1 to 20 kHz, more specifically about 5 to 15 kHz, and more preferably about 10 kHz. Sized to provide the system's resonant frequency range.

  For example, an additional pair of excitation / detection transducers or gauges can be attached to the side of the beam at 90 ° to the illustrated transducers or gauges 21 and 22 without having to reorient the beam on the bridge. , It may be possible to provide an indication at right angles to the latter transducer. Additionally or alternatively, the beam and / or transducer system can be pivoted with respect to the dental bridge or crown.

  To protect the transducer during sterilization of the device, the transducer or gauge may be coated with, for example, an air-dried acrylic material, and optionally with the beam. The electrical connection or wire connected to the transducer is configured or adapted to minimize its damping effect on the resonant structure. The member may be in a form other than a cantilever and / or the piezoelectric transducer may be replaced with other receiving / transmitting elements using, for example, sound resonance. Instead of being basically straight, the beam may be substantially U-shaped and connected to a bridge or crown by its base. The transducer or equivalent can be attached to the same leg or opposite legs.

  According to the second aspect of the present invention, the measurement is performed in a non-contact manner.

  Referring to FIG. 3, the system includes a member 30 in the form of a cantilever that is attached to the bridge 10. The member 30 includes a magnetic member 31. The magnetic member 31 can be provided at one end of the beam 30, for example, at the free end of the beam, or can be integrated inside the beam.

  The second part of the system comprises an inspection device 35 including a probe 351 and a response analyzer unit 352. The probe 351 includes a coil 353 that detects the vibration of the magnetic member 31.

  In this case, one of the crowns 11 is attached to a tooth 17 connected to the implant instead of a real tooth. This implant is secured to the bone by a threaded portion 18.

  In order to generate vibration in the beam, it must be excited. This can be done manually or by applying a force F to the beam by means of an electrical exciter.

  The signal detected by the probe 350 is amplified by the amplifier 354 and applied to the analyzer as an input. The output from the analyzer, which represents the ratio of response voltage to excitation, is fed to a processor, such as a microprocessor 355, that is used to vary the frequency output of the analyzer's oscillator and store the result in the data store 356. The result is printed and / or displayed on a display or the like.

  Reference is now made to FIG. 4, which shows a third embodiment of the present invention, wherein the first part of the mechanism according to the present invention is attached to a dental bridge 10 in the form of a cantilever 30 as in the previous embodiment. It comprises the member which was made. In this case, the beam 30 includes a marking 42 such as a line disposed at one end of the beam 20.

  The second part of the mechanism comprises an inspection device 450 that includes a probe 451 and a response analyzer unit 452. The probe 450 includes a light source 453a, preferably but not limited to a laser, and a photodetector 453b that detects reflection from the beam and vibration of the beam caused thereby. The light source is preferably a laser diode. The beam comprises one or several markers, such as darker (or brighter) parts that provide light reflection.

  The beam is excited manually or by applying a force F to the beam, for example by an electric exciter.

  A light source at the tip of the probe irradiates the beam, and the photodetector 453b detects the reflected light. The detected optical signal is converted into an electrical signal by the detector, and the signal detected by the probe 451 is amplified by the amplifier 454 and applied to the analyzer as an input. The output from the analyzer, which indicates the ratio of response voltage to excitation, is provided to a processor, such as a microprocessor 455, that is used to vary the frequency output of the analyzer's oscillator and store the result in the data store 456. The result is printed and / or displayed on a display or the like.

  In use, the beam 31 is secured to the dental bridge 10. Preferably, but not necessarily, the beam according to the invention is disposable, which means that the beam can be removed and discarded and can provide a hygienic inspection mechanism. means.

  FIG. 8 shows the data from the coarse sweep used to roughly obtain the resonant frequency in the apparatus of FIG. A finer sweep around this region is then used to more accurately identify this frequency, generally the first frequency or fundamental frequency. This frequency is recorded and compared with data from previous measurements, for example when the bridge was installed, for example.

  For a particular bridge, the resonant frequency varies with the degree of crown attachment to the tooth. Thus, by comparing the detected resonant frequency with previously collected data for the same bridge, an indication of the degree of attachment of that bridge can be obtained.

  Techniques based on detecting and comparing resonant frequency shifts rather than amplitude changes are effective in determining the quality of the installation.

  The beam may preferably be of a metallic material, for example titanium or aluminum, in the region of about 1-20 kHz, more specifically on the order of 1-10 kHz and preferably about 8 kHz (arranged bridges And dimensions) to provide the resonance frequency range of the system. For example, in the embodiment of FIGS. 2 and 3, the upright beam can be about 1 cm high.

  In yet other embodiments, the beam may be made of a ferromagnetic material and may be excited by an external magnetic field generated by a magnetic field generator. The magnetic field generator may be a permanent magnet for generating a DC field or a coil for generating an AC field. Probes can also be placed externally.

  Magnets attached to smart pegs can be excited by magnetic pulses. After each pulse, an alternating magnetic field that is the result of a self-oscillating peg is detected by an electric coil in the measurement probe. The magnetic pulse may be generated by another coil in the same probe (or additional probe).

  Metal pegs have a simplified mechanical design compared to transducers and do not require separate calibration. Since they are not electrically connected to the instrument, it is impossible to store any calibration parameters in them. Instead, carefully controlled manufacturing processes minimize individual differences between pegs.

  Pegs also have simpler mechanical behavior when they are oscillating at their resonant frequency. The pegs are more sensitive and have a predictable effect until they have very low mounting stability.

  The measurement may consist of a plurality of pulses, for example 4 or 30 pulses. In the case of 30 pulses, these pulses cover the frequency spectrum of 1 to 10 kHz. Since the pulses are narrower, 30 pulses contain more energy. This makes the response signal stronger, improves the signal-to-noise ratio, and makes the measuring device of the present invention less sensitive to ambient electromagnetic noise. One skilled in the art will recognize that the number of pulses is not limited to four or thirty.

  An embodiment of the dental bridge 10 is shown in FIG. In this embodiment, a detectable part such as a magnetic or optical part 16 is incorporated into the crown 11 or denture 13. This embodiment makes it possible to use the same measurement points.

  It will be understood that various modifications may be made without departing from the scope of the invention as defined in the appended claims.

  To protect the transducer during sterilization of the device, the transducer or gauge may be coated with, for example, an air-dried acrylic material, and optionally with the beam. The member may take a form other than a cantilever. The beam is essentially U-shaped instead of being straight, and can be connected to the bridge by its base. In addition, alternative detectors such as ultraviolet light and sound can be used.

  The present invention is not limited to bridges and can be applied to crowns or other components attached to teeth.

Claims (23)

  A method for inspecting the quality of attachment between crowns (11) attached to the surface of teeth (14; 17), comprising: at least one of the members (16, 20, 21, 31) in contact with said crown (11) Detecting a resonance frequency; and interpreting the detected resonance frequency in terms of the degree of attachment of the crown to the tooth.   The method of claim 1, comprising removably attaching the member to the crown or a part attached to the crown.   The method of claim 1 or 2, wherein the member comprises a cantilever.   The method according to claim 3, wherein the beam is attached to the crown or a part connected to the crown through a screw hole.   The method according to claim 3, wherein the beam is attached to the crown or a component connected to the crown by an adhesive.   The method of claim 1, wherein the member is incorporated into the crown or a part attached thereto.   7. A method according to any one of the preceding claims, comprising comparing the detected resonance frequency with one or more values of the resonance frequency of the same or similar member from a previous measurement.   Exciting the member with an AC signal; detecting the response of the member to the AC signal; and varying the frequency of the AC signal until the detected response of the member is maximized. The method according to claim 1.   The method of claim 8, further comprising deriving an output signal that is a ratio of a voltage of the response signal to a voltage of the excitation signal.   The method according to claim 1, wherein the measurement is non-contact.   The method according to any one of claims 1 to 10, further comprising pulse excitation of the member, a step of detecting a response from the member, and a step of analyzing the frequency of the response signal.   A crown attachment quality inspection comprising a detector (27, 351, 451) for detecting at least one resonance frequency of a member (16, 20, 21, 31) attached to the crown (11). apparatus.   Means for exciting the member with an AC signal, and a detector for detecting a response of the member to the AC signal so as to vary the frequency of the AC signal, the detector comprising the member 13. The apparatus of claim 12, wherein the apparatus detects when the response of the system is maximized.   13. The apparatus of claim 12, comprising a piezoelectric element provided as the excitation means configured to be driven by a variable frequency oscillator.   The apparatus of claim 12, wherein the member comprises a magnetic portion.   The apparatus of claim 12, wherein the detector comprises a coil.   The apparatus of claim 12, wherein the member comprises a marker.   The apparatus of claim 17, wherein the detector comprises an illuminance detector.   The apparatus of claim 12, wherein the member comprises a ferromagnetic material.   The apparatus of claim 19, wherein the detector comprises a coil for detecting disturbances in an external magnetic field.   21. The apparatus of any one of claims 12-20, further comprising an amplifier, a processor, and a data storage device.   The apparatus of claim 21, wherein the processor is further configured to vary a frequency output of an oscillator and stores the result in the data storage device.   23. At least one coil configured to output a magnetic pulse to a member attached to a crown or component attached thereto and to detect a response corresponding to the magnetic pulse from the member. Equipment.

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