SYSTEM AND METHOD FOR STERILIZING A DENTAL ROOT CANAL

FIELD AND BACKGROUND OF THE INVENTION

The present invention relates to a dental root canal sterilizing system and, more particularly, to a system and method for sterilizing a dental root canal utilizing an electric pulse.

The quality of obturation of a dental root canal depends on preparation of the root canal, the root canal filling material, and the filling technique used. In preparing a root canal, the bulk of material present in the canal must be removed, and it is important to remove any layer of debris that remains along the surface of the canal. This so-called smear layer, if not removed, will prevent contact between the root canal wall and the endodontic filling material. The smear layer may, however, be difficult to remove, as it may adhere firmly to the dentine along the root canal and may form.an irregular surface thereon.

It is known to biomechanically clean the root canal in order to reduce the number of bacteria present in the canal. In order to remove debris, necrotic tissue, bacteria, and smear layer, various substances have been used during canal preparation. "Chlorhexidine Gluconate," presented to the Fourth Transpacific Endodontic Conference, Port Douglas, September 2004, by Bettina Basrani, DDS, discusses the most commonly used irrigant, sodium hypochlorite, as an effective antimicrobial agent and tissue solvent. However, due to its possible toxicity, other irrigants may be alternatively used, but these are found to be less effective. It is noted that, in order to completely remove the smear layer, the root canal may be irrigated by agents containing both organic and inorganic solvents, but the way they are applied and their quantity were found to be important in achieving satisfactory results.

"Rinsing of the Root Canal," Scripta Media (BRNO) - 76(1): 49-54, January 2003 discusses preparation of a dental root canal by removal of cut debris which was smeared over the dentinal surface. The article states that, instead of using an irrigant, ultrasound may be used, wherein the smear layer may be removed by the mechanical and cavitation effect and the acoustic streaming of the ultrasound waves. However, this technique is only partly successful, in that it removes smear layers only in isolated areas of the coronal and middle thirds of the root canal.

"A Comparison between a Smooth Wire and a K-FiIe in Removing Artificially Placed Dentine Debris from Root Canals in Resin Blocks during Ultrasonic Irrigation" by L.W.M. van der Sluis, M.K. Wu, and P.R. Wesselink in the International Endodontic Journal, 38(9):593-596, Sept. 2005, discusses the efficacy of a smooth wire with a conventional K-file, in removing dentine debris from root canal grooves during ultrasonic irrigation. Results indicated that ultrasonic irrigation is not always successful in debris removal. Similar results were obtained in a study discussed in the article entitled "Effects of Various Irrigating Solutions on the Cleaning of the Root Canal with Ultrasonic Instrumentation" by Vansan LP, et al., in the Brazilian Dental Journal, 1990; l(l):37-44.

A study entitled "Do Brushes Have an Effect on Root Canal Cleanliness?" by M. Roggendorf, et al., at the University of Erlangen, Germany, compared root canal cleanliness after irrigation with and without ultrasonic activation, in contrast to root canal cleanliness after the use of endodontic brushes. Results showed better scores for debridement and smear layer removal after irrigation with and without brushes in contrast to treatment with ultrasonics.

While a variety of methods are known for cleaning out a dental root canal, such as those discussed above, none has been proven to be safe and able to thoroughly clean and sterilize the root canal. US Patent No. 6,482,008 to Perdomini et al. teaches devitalizing a tooth by inserting an electrode into a root canal of the tooth, and transmitting a high-frequency electric pulse. The part of the tissue within the root canal which is in contact with the electrode is destroyed, while the remainder of the tissue is coagulated, thus devitalizing the tooth. The device requires operation by a dentist, who must first determine that the electrode has reached a suitable position within the root canal. He must then choose the power, duration, and frequency of the electric pulse, according to the type of tooth being treated, i.e., whether the tooth is an incisor, a canine, a premolar, or a molar. Finally, the dentist must close the electrical circuit, such as by pressing on a pedal, in order to actuate the device to transmit the electric pulse. It should be noted that, as the device transmits the same electrical impulse, regardless of the canal condition, there is no safeguard provided against overheating of the canal.

There is thus a widely recognized need for, and it would be highly advantageous to have, a system and method for cleaning and sterilizing a dental root canal devoid of the above limitations.

SUMMARY OF THE INVENTION

According to one aspect of the present invention there is provided a system for sterilizing a dental root canal comprising: an electronic apex locator configured to determine the apex of the dental root canal; and a dental instrument, in data communication with the electronic apex locator and having a working tip, the working tip configured to be inserted into the dental root canal, the dental instrument in communication with a sterilizing unit configured to automatically transmit an electric pulse via the working tip into the root canal, the electric pulse selected for sterilizing the root canal.

According to another aspect of the present invention the sterilizing unit is configured to automatically transmit the electric pulse when the working tip of the dental instrument reaches a predetermined distance from the root canal apex.

According to a still another aspect of the present invention the predetermined distance is 3.0 mm.

According to yet another aspect of the present invention the predetermined distance is 2.0 mm.

According to yet a further aspect of the present invention the apex locator is configured to determine the distance between the working tip of the dental instrument and the apex of the root canal.

According to another aspect of the present invention the distance determined is accurate to substantially 0.1 mm.

According to still another aspect of the present invention the system further comprises a relay unit configured to selectively alternate between operation of the apex locator via the dental instrument and operation of the sterilizing unit via the dental instrument.

According to yet another aspect of the present invention the relay unit is configured to alternate between the operation of the apex locator and the operation of the sterilizing unit within 100 milliseconds. According to yet a further aspect of the present invention the system comprises a timing controller configured to control the selective alternating of the relay unit.

According to another aspect of the present invention the apex locator is configured to determine the condition of the root canal, the duration of the electric pulse being automatically determined based on the canal condition.

According to still another aspect of the present invention the system further comprises a timing controller configured to receive data regarding the root canal condition from the apex locator and, based on the received data, to automatically control the duration of the electric pulse. According to yet another aspect of the present invention the data regarding the root canal condition is based on a measure of the percentage of humidity in the root canal.

According to yet a further aspect of the present invention the timing controller is configured to limit the maximum duration of the electric pulse to a predetermined amount of time.

According to another aspect of the present invention the predetermined amount of time is 100 milliseconds.

According to still another aspect of the present invention the system further comprises an immobilizer device associated therewith, wherein: the apex locator is configured to operate when the following condition is met: (a) the immobilizer device is inactivated; the apex locator is configured to cease to operate when both of the following conditions are met: (b) the apex locator has determined that the working tip of the dental instrument is located at a predetermined distance from the root canal apex; and (c) the apex locator has determined that the humidity level of the root canal is within a predetermined range; and the sterilizing unit is configured to automatically transmit the electric pulse when all of conditions (a), (b), and (c) have been met.

According to yet another aspect of the present invention the system further comprises a grounding cable configured to ground the apex locator and the sterilizing unit. According to yet a further aspect of the present invention the system further comprises a dental instrument cable configured to connect the dental instrument to the apex locator and to the sterilizing unit.

According to another aspect of the present invention the electric pulse is configured to dry matter present within the root canal. According to still another aspect of the present invention the electric pulse is configured to sterilize the root canal.

According to yet another aspect of the present invention the electric pulse is configured to kill substantially 99% of all bacteria present in the root canal.

According to yet a further aspect of the present invention the electric pulse is configured to heat the working tip of the dental instrument to substantially 300 degrees Celsius.

According to another aspect of the present invention the system is configured to limit the heating effect of the electric pulse on the root canal to substantially 10 degrees above the temperature thereof.

According to still another aspect of the present invention the sterilizing unit is configured to transmit a short electric pulse a having a predetermined frequency and voltage. According to yet another aspect of the present invention the system further comprises an additional dental instrument configured to facilitate removal of the dried matter from the root canal.

According to yet a further aspect of the present invention the additional dental instrument comprises a flexible file. According to another aspect of the present invention the additional dental instrument is configured to be inserted into the root canal and to be flexed in accordance with the original configuration of the root canal.

According to still another aspect of the present invention the additional dental instrument further configured to buff and to polish the root canal after the electric pulse has been transmitted thereinto.

According to yet another aspect of the present invention the system further comprises a retaining device configured to retain the flexible file.

According to yet a further aspect of the present invention the system further comprises a handpiece configured to retain the flexible file. According to another aspect of the present invention at least a portion of the dental instrument is replaceable.

According to still another aspect of the present invention the replaceable portion of the dental instrument includes the working tip thereof.

According to yet another aspect of the present invention the replaceable portion is configured to be resterilized.

According to yet a further aspect of the present invention the replaceable portion comprises a tip retainer including the working tip.

According to another aspect of the present invention the dental instrument includes a socket formed in an end portion thereof, the tip retainer configured to be inserted into and to be retained in the socket.

According to still another aspect of the present invention the dental instrument includes an electrical contact adjacent the socket, the tip retainer including an electrical connector plug, the dental instrument and the tip retainer configured to provide an electrical connection between the electrical contact and the electrical connector plug.

According to yet another aspect of the present invention the replaceable portion of the dental instrument is configured to be replaced with an additional replaceable portion, and wherein the sterilizing unit is configured to automatically transmit additional electric pulse via the dental instrument into the root canal, the additional electric pulse selected for sterilizing the root canal.

According to yet a further aspect of the present invention the duration of the additional electric pulse is substantially half the duration of the electric pulse.

According to another aspect of the present invention the system further comprises a timing controller configured to automatically control the duration of the additional electric pulse.

According to still another aspect of the present invention the duration of the additional electric pulse is less than a predetermined amount of time.

According to yet another aspect of the present invention there is provided a method for sterilizing a dental root canal, the method comprising the following steps: (a) providing a dental instrument having a working tip; (b) inserting the dental instrument into the beginning of the root canal; (c) transmitting a pulsed signal from the dental instrument, via the root canal, to the apex of the root canal; (d) converting the signal to a digital signal indicative of the distance between the working tip of the dental instrument and the apex of the root canal; (e) if the digital signal indicates that the working tip of the dental instrument has reached a predetermined distance from the apex of the root canal then proceeding to step (g), otherwise proceeding to step (f); (f) inserting the dental instrument further into the root canal and returning to step (c); and (g) transmitting an electric pulse via the dental instrument, thereby sterilizing the root canal and drying any matter present in the root canal; (h) removing the dental instrument from the root canal; (i) removing any remaining matter present within the root canal; (j) replacing the working tip of the dental instrument with a second

working tip; (k) inserting the dental instrument into the beginning of the root canal; (1) transmitting a pulsed signal from the dental instrument, via the root canal, to the apex of the root canal; (m) converting the signal to a digital signal indicative of the distance between the second working tip of the dental instrument and the apex of the root canal; (n) if the digital signal indicates that the second working tip of the dental instrument has reached a predetermined distance from the apex of the root canal then proceeding to step (p), otherwise proceeding to step (o); (o) inserting the dental instrument further into the root canal and returning to step (1); and (p) transmitting an electric pulse via the dental instrument, thereby sterilizing the root canal. The present invention successfully addresses the shortcomings of the presently known configurations by providing a system and method for sterilizing a dental root canal comprising: an electronic apex locator configured to determine the apex of the dental root canal; a dental instrument, in data communication with the electronic apex locator and having a working tip, the working tip configured to be inserted into the dental root canal, the dental instrument in communication with a sterilizing unit configured to automatically transmit an electric pulse via the working tip into the root canal, the electric pulse selected for sterilizing the root canal.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described below. In case of conflict, the patent specification, including definitions, will be the determinant. In addition, the materials, methods, and examples are illustrative only and are not intended to be limiting. As used herein, the terms "comprising" and "including" or grammatical variants thereof are to be taken as specifying the stated features, integers, steps or components but do not preclude the addition of one or more additional features, integers, steps, components or groups thereof. These terms encompass the terms "consisting of and "consisting essentially of." The phrase "consisting essentially of or grammatical variants thereof when used herein is to be taken as specifying the stated features, integers, steps or components but do not preclude the addition of one or more additional features, integers, steps, components or groups thereof but only if the additional features,

integers, steps, components or groups thereof do not materially alter the basic and novel characteristics of the claimed composition, device or method.

The term "method" refers to a manner, means, technique and procedure for accomplishing a given task including, but is not limited to, those manners, means, techniques and procedures either known to, or readily developed from known manners, means, techniques and procedures by practitioners of the art.

The term "dentist" refers to any dental practitioner qualified to perform root canal treatment and may be replaced by any term denoting a suitable dental specialist such as, for example, "endodontist," "periodontist," or "prosthodontist."

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 schematic illustration of the components of a system for sterilizing a dental root canal in accordance with an embodiment of the present invention; Fig. 2 is an illustration of an exemplary embodiment of a system in accordance with the present invention;

Fig. 3a is an illustration of an exemplary embodiment of a dental instrument in accordance with the present invention;

Fig. 3b is an illustration showing an enlarged view of an end portion of the dental instrument indicated in Fig. 3a;

Fig. 3c is an illustration showing the end portion of the dental instrument shown in Fig. 3b, wherein the working tip has been separated therefrom;

Fig. 4 is a block diagram of an embodiment of an apex locator device in accordance with the present invention; and

Figs. 5a and 5b illustrate a method for sterilizing a dental root canal, in accordance with an embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The principles and operation of a system and method for sterilizing a dental root canal according to the present invention may be better understood with reference to the drawings and accompanying descriptions.

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. Referring now to the drawings, Figure 1 is a schematic illustration of the components of a system 10 for sterilizing a dental root canal 20 in accordance with an embodiment of the present invention. System 10 includes an apex locator 12 for determining the apex 16 of the dental root canal 20 and a dental instrument 14, in data communication with the electronic apex locator 12. Dental instrument 14 may be inserted into a dental root canal 20 and is associated with a sterilizing unit 18 which automatically transmits an electric pulse via the dental instrument 14 into the root canal 20, the electric pulse selected for sterilizing the root canal 20, as will be discussed in detail below. When dental instrument 14 is inserted into the root canal 20, it is initially employed to open the canal by pushing aside any debris that may be present therein, e.g., pulp matter.

Sterilizing unit 18 automatically transmits an electric pulse when a working tip 15 of the dental instrument 14 reaches a predetermined distance from the root canal apex 16. The predetermined distance may be any suitable distance selected by the dentist such as, for example, 3.0 mm. Alternatively, the predetermined distance may be 2.0 mm.

The apex locator 12 determines the distance between the working tip 15 of the dental instrument 14 and the apex 16 of the root canal 20, the distance determined being accurate to substantially 0.1 mm.

System 10 further comprises a relay unit 22 which selectively alternates between operation of the apex locator 12 via the dental instrument 14 and operation of the sterilizing unit 18 via the dental instrument 14. Relay unit 22 alternates between the operation of the apex locator 12 and the operation of the sterilizing unit 18 within 100 milliseconds. The selective alternating of relay unit 22 is provided by a timing controller 24.

In accordance with an embodiment of the present invention, apex locator 12 is configured to determine the condition of the root canal 20, as will be discussed further below, and the duration of the electric pulse is then automatically determined, based on the canal condition.

The timing controller 24 receives data regarding the root canal condition from the apex locator and, based on the received data, automatically controls the duration of the electric pulse. For example, a typical electric pulse may be transmitted for a duration of 0.08 seconds. Data regarding the root canal condition is based on a measure of the percentage of humidity in the root canal, which may be rated on a scale of 0-9. The more humidity detected within the root canal, the longer will be the duration of the pulse transmitted into the root canal. It may be noted that, in any event, the duration of a typical pulse transmitted in accordance with embodiments of the present invention varies only by tenths of a second, depending on the humidity measured. In the event that the humidity measured is higher than 9 on the scale, the system may provide an indication, such as on a display 40 (fig. 2), of a wet canal, in which case the dentist will first dry out the canal by some other means, such as by using paper points, before continuing with use of the present embodiments.

The timing controller 24 limits the maximum duration of the electric pulse to a predetermined amount of time such as, for example, 100 milliseconds. This ensures that transmission of the electric pulse is limited so that there is no overheating of the root canal. Thus, even in the event of a malfunction of the system, the electric pulse time is limited. It may be noted that the present embodiments are thus provided with a unique safety feature in that the duration of the electric pulse is limited and is automatically determined by the system, according to the canal condition, and not by the dentist. As a result, there is no danger of overheating the canal, as may occur with known devices, as the system of the present embodiments enables the condition of the root canal to be accurately determined such that an electric pulse of a specific duration is transmitted.

With additional reference to Fig. 2, there is shown an illustration of an exemplary embodiment of a system 10 for sterilizing a dental root canal in accordance with the present invention. System 10 is further provided with an immobilizer device (not shown) which prevents inadvertent operation of any component of the system 10. Immobilizer device may be inactivated by pressing on an immobilizer button 26 which is located on dental instrument 14, proximal to working tip 15. In accordance with the present embodiments, when the immobilizer device is inactivated, apex locator 12 begins operation, measuring the distance between the working tip 15 of dental instrument 14 and the root canal apex 16 and determining the condition of the root canal, as will be discussed further below. When apex locator 12 has determined that the dental instrument 14 is located at a predetermined distance from the root canal apex 16 and that the humidity level of the root canal 20 is within a predetermined range, operation of the apex locator 12 will cease and sterilizing unit 18 will automatically transmit the electric pulse. It may be noted that the system 10 of the present embodiments thus possesses another safety feature, in that all three conditions must be met: (a) the immobilizer must be inactivated, (b) the dental instrument must be located at the predetermined distance from the root canal apex, and (c) the amount of humidity within the root canal cannot be too great, in order for the electric pulse to be transmitted. Thus, after the immobilizer is inactivated, the sterilizing unit 18 is effectively put in a stand-by mode until conditions (b) and (c) are met.

The system 10 is further provided with a contact element in the form of a lip hook 44 and a cable 34 which acts as a grounding cable, to ground the apex locator 12 and the sterilizing unit 18. Lip hook 44 will be discussed further below. A dental instrument cable 32 connects the dental instrument 14 to the apex locator 12 and to the sterilizing unit 18.

In accordance with the present embodiments, in addition to sterilizing the root canal 20, the electric pulse transmitted by the system 10 is effective to dry any matter which may be present within the root canal, such as necrotic tissue, blood, etc. The electric pulse thus has an effect which is identical to that of microwaves which are utilized for heating and/or sterilizing food, in that the electric pulse spreads, via all tissue present, throughout the root canal 20, up to the dentin layer thereof. The pulse completely dries all tissue and kills substantially 99% of bacteria which may be present in the root canal 20. The present embodiments thus provide an automatic

system for the sterilization of a root canal with a level of accuracy that is not achievable with any other system, i.e., an automatic system for killing off of infection without the use of antibiotics and with a considerably shortened treatment time.

While the electric pulse heats the working tip 15 of the dental instrument 14 to substantially 300 degrees Celsius, the timing controller limits the duration of the pulse, as noted above, such that the heating effect of the electric pulse on the root canal is limited to substantially 10 degrees above the temperature thereof. This provides the present embodiments with another safety feature. The sterilizing unit 18 transmits a short electric pulse having a predetermined frequency and voltage, such as, for example, 500 volts, at a current of 0.2 amp, and at a power of 100 Watts. It may be noted that these values may vary slightly depending on the detected root canal condition and the specific algorithms used by the microprocessor, which is discussed below.

As noted above, the electric pulse transmitted by the system 10 is effective to dry any matter which may be present within the root canal 20, which greatly facilitates clearing out of the root canal. The system 10 is further provided with an additional dental instrument which facilitates removal of the dried matter from the root canal 20. The additional dental instrument is a flexible file 36 which is constructed so as to be inserted into the root canal 20 and to be flexed in accordance with the original configuration of the root canal. The flexible file 36 thoroughly cleanses the root canal 20 by buffing and polishing the surfaces thereof after the electric pulse has been transmitted thereinto, as any matter contained therein has been dried by the electric pulse, as noted above. This action of buffing and polishing, in accordance with the present embodiments, is advantageous when compared with drilling and excavating of tissue which is commonly done by dentists today using standard NiTi files. Thus, in accordance with the present embodiments, only a single flexible file is required, in contrast to the multiple files that are required using known methods for clearing debris from a dental root canal. It may be noted that, due to the rough surface of the flexible file 36, it cannot be sterilized, so it is not reusable. Thus, only an unused flexible file 36 may be used in accordance with the present embodiments, in order to ensure sterility of the root canal.

In accordance with the present embodiments, the system 10 is provided with a file retaining device 38 configured to retain the flexible file 36, which facilitates manual twisting of the file 36 within root canal 20 by a dentist. The system 10 is

further provided with a handpiece 42 for retaining and actuating the additional dental instrument. While a conventional handpiece (not shown) may hold and twist a conventional file (not shown) within a root canal or may hold a conventional file (not shown) while the handpiece is vibrated, the handpiece 42 facilitates the clearing out of dry matter from the canal by transmitting vibrations through the flexible file 36, in accordance with the present embodiments.

After the root canal 20 has been sterilized and any dry matter has been removed therefrom, as discussed above, in order to ensure sterility, the root canal must be resterilized, in accordance with the present embodiments, since impurities from the work environment may have been introduced into the root canal during cleaning by the flexible file 36. It should, however, be noted that the working tip 15 of the dental instrument 14 may have been exposed to bacteria and other contaminants in the air of the work environment when it was taken out of root canal 20. Thus, the working tip 15 cannot be simply reused to resterilize the root canal. Reference is now made to Figs. 3a-c, wherein there is shown a dental instrument 14 in accordance with the present embodiments, wherein the working tip 15 is replaceable, as will be discussed below. ^{~ ~}

In accordance with the present embodiments, sterility of the working tip 15 of the dental instrument 14 must be maintained, as discussed above. Therefore, after any dry matter has been removed from the root canal, at least the working tip 15 of the dental instrument 14 must be either resterilized or replaced, as discussed hereinbelow. In order to facilitate replacement of at least the working tip 15, it is constructed so as to be disposable and replaceable with an identical sterile working tip.

As shown in Figs. 3a-c, the end portion 44 of dental instrument 14 proximal to the working tip 15 is provided with a tip retainer 46 which is retained in a socket 50 formed in the dental instrument 14. Working tip 15 protrudes out of the end of tip retainer 46 distal to the dental instrument 14. The end of tip retainer 46 proximal to the dental instrument 14 is retained in a socket 50 formed in end portion 44 of dental instrument 14. Electrical connector plug 48 protrudes out of this end of tip retainer 46, and is constructed so as to contact an electrical contact 49 disposed adjacent to socket 50 of end portion 44. The electrical contact 49 thus provides an electrical connection between connector plug 48 and electrical conductor 31 and, thereby, provides an electrical connection from working tip 15 to cable 32.

After the dental instrument 14 has been used to sterilize a dental root canal, as discussed above, in order to ensure sterility during the root canal treatment, the working tip 15 is replaced with another sterile working tip. Dental instrument 14 has thus been provided with a unique feature in that the tip retainer 46 may be easily removed by pulling it out of the end portion 44 of dental instrument 14, thus discontinuing contact between connector plug 48 and electrical contact 49. The used tip retainer 46 may then be either discarded or resterilized for later use. The removed tip retainer 46 may then be easily replaced with an identical, sterile, tip retainer 46, wihch may simply be inserted into the end portion 44 of dental instrument such that connector plug 48 contacts electrical contact 49, thus completing the portion of the electric circuit from working tip 15 to cable 32.

It may be noted that tip retainer 46 has been constructed such that the angle between working tip 15 and electrical connector plug 48 is obtuse, preferably about 110°, in order to facilitate manipulation of working tip 15 by a dentist. If desired, however, another angular orientation may be chosen.

The provision of a replaceable tip retainer 46 containing the working tip 15 furnishes the present embodiments with an additional safety feature, in that complete sterility is ensured due to the fact that the disposable end portion 44, which includes the working tip 15, is easily replaceable, as noted above. In accordance with the present embodiments, in order to be able to resterilize the dental root canal 20 after any dry material has been removed therefrom, as discussed above, the disposable portion of the dental instrument is replaced with an additional disposable portion, as noted above. Once the disposable portion has been replaced, the sterilizing unit 18 is actuated again to automatically transmit an additional electric pulse via the dental instrument 14 into the root canal 20, the additional electric pulse selected for sterilizing the root canal, as discussed above. It should be understood that the additional electric pulse is automatically transmitted when the apex locator 12 has determined that the working tip 15 has reached a predetermined distance from the root canal apex and that the duration of the additional electric pulse is determined based on the canal condition, as noted above with regard to Figs. 1 and 2.

The required duration of the additional electric pulse is substantially half the duration of the first electric pulse, since any matter that was present within the root canal 20 has already been removed, as discussed above. For example, for a first

electric pulse duration of 0.08 seconds, a typical additional electric pulse duration is 0.04 seconds. As above, timing controller 24 automatically controls the duration of the additional electric pulse. As a further safety feature, the duration of the additional electric pulse is less than a predetermined amount of time, thus preventing possible overheating of the canal and dentin layer.

The present embodiments thus provide a closed-loop control system 10 which is very user friendly and simple to operate. The system facilitates substantially 99% sterilization of a dental root canal, as compared with up to 50% effectiveness, using known systems. With additional reference to Fig. 4, system 10 may provide an indication, such as on display 40, of the condition of the dental root canal 20, as noted above. The display 40 may also exhibit data concerning the dental root canal such as, for example, the distance of a working tip 15 of the dental instrument 14 from the root canal apex 16. In accordance with the present embodiments, the apex locator 12 is a digitally computerized unit comprising a software operated microcontroller 52 having a pulse generator 54, a memory 56 and an analog to digital converter (ADC) ^" 58, the pulse generator 54 for feeding a pulse to a gain control circuit 60 for controlling the amplitude of the pulse; a driver 62 for receiving signals from the gain control circuit 60 and for feeding the signals to an electrically conductive shaft 66 and dental instrument 14 having working tip 15; and an input buffer 64 for receiving signals from the dental instrument 14 and for feeding the signals to the ADC 58, wherein the signals are converted to digital signals. The pulse generator 54 is for producing micro- electrical signals at multiple frequencies and for sending the signals through the dental instrument 14 to the apex 16 of the root canal 20. For example, in accordance with the present embodiments, typical frequencies transmitted by the apex locator to the root canal apex are 1300 Hz and 1600 Hz. The pulsed signals comprise a plurality of waves wherein the length of the waves shortens as the working tip of the dental instrument approaches the apex of the root canal. In accordance with the present embodiments, the microcontroller 52 is configured to process the output of the multiple frequencies to determine the distance between the working tip 15 of the dental instrument 14 and the apex 16 of the root canal 20. The distance determined is accurate to substantially 0.1 mm, as noted above.

Additionally, as noted above, the apex locator 12 is configured to determine the physical condition of the interior of the dental root canal 20, based on a measure of the humidity therein. The microcontroller 52 automatically adjusts the impedance of current transmitted via the dental instrument 14 such that the impedance corresponds to the physical condition of the interior of the dental root canal 20. The gain control circuit 60 maintains the signals at a constant signal to noise ratio. The pulses are substantially square pulses. The system further comprises a filter (not shown) configured to filter the signals transmitted from the dental instrument 14 to the ADC 58. The microcontroller 52 calculates the average of the majority of signals received. The system 10 further comprises a contact element 44, as noted above, the contact element 44 suitable for contacting the tissue of a patient, the contact element transmitting the signals from the dental instrument 14 to the microcontroller 52. The contact element may contact any portion of the patient, such as his lip.

With reference to Figs. 5a and 5b, there is provided a method 100 for sterilizing a dental root canal in accordance with the present embodiments. Method 100 begins with step 102, providing a dental instrument having a working tip. At step 104, the dental instrument is inserted into the beginning of the root canal andrat step ^{^} 106, a pulsed signal is transmitted from the dental instrument, via the root canal, to the apex of the root canal. The signal is converted to a digital signal indicative of the distance between a working tip of the dental instrument and the apex of the root canal, as shown at step 108. At step 110, the apex locator determines whether the working tip of the dental instrument has reached a predetermined distance from the apex of the root canal. If so then the method proceeds with step 114; otherwise the dental instrument is inserted further into the root canal, as shown at step 112, and the method then returns to step 106. At step 114, an electric pulse is transmitted via the dental instrument, thereby sterilizing the root canal and drying any matter present in the root canal. Then at step 116, the dental instrument is removed from the root canal. At step 118, any remaining matter present within the root canal is removed. The working tip of the dental instrument is replaced with a second working tip, as shown at step 120, and the dental instrument is again inserted into the beginning of the root canal, as shown at step 122. A pulsed signal is transmitted from the dental instrument, via the root canal, to the apex of the root canal, at step 124, and the signal is converted to a digital signal indicative of the distance between the second working tip of the dental instrument and the apex of the root canal, at step 126. At step 128, the apex locator

determines whether the second working tip of the dental instrument has reached a predetermined distance from the apex of the root canal. If so then the method proceeds with step 132; otherwise the dental instrument is inserted further into the root canal, as shown at step 130, and the method then returns to step 124. At step 132, an electric pulse is transmitted via the dental instrument, thereby sterilizing the root canal.

The present embodiments thus provide a method 100 which is relatively simple to carry out, and may achieve substantially 99% sterilization of a dental root canal, as compared with as little as 50% effectiveness, using known methods.

It is expected that during the life of this patent many relevant apex locator devices will be developed and the scope of the term "apex locator" is intended to include all such new technologies a priori.

As used herein the term "about" refers to +/- 10 %.

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.