BACKGROUND

1. The Field of the Invention

The invention generally relates to devices for locating the apex of a root canal. 2. The Relevant Technology

When a root canal of a living tooth becomes infected or abscessed, discomfort and, in many cases, severe pain can result. In the early days of dentistry the only solution was to pull the tooth. More recently, however, dental practitioners have learned to successfully remove the pulp material that forms the nerve of a tooth that has become infected. After careful preparation of the canal that contained the nerve material, the canal is refilled with an inert filling material, such as gutta percha, and a sealer. This process allows the patient to retain the tooth.

To achieve a successful root canal restoration, the dental practitioner must carefully and as completely as possible remove the infected pulp material. The removal process typically includes shaping the root canal so that it can be effectively and successfully filled and sealed with an inert material to reduce the possibility of further infection.

Cleaning and shaping the root canal in preparation for receiving a sealing and/or filling material is achieved by the use of metal endodontic instruments that include cutting surfaces for removing tissue in the root canal. Since root canals are seldom straight, often having bends and twists, at least some endodontic instruments are flexible so as to allow the instrument to follow the curvature of the root canal.

One difficulty in effectively preparing the root canal is when removing infected and/or necrotic tissue in the vicinity of the apex, or terminus of the root canal. Specially configured files, known as apical files, are typically used to prepare the deepest portion of the root canal adjacent to the apex. Often, however, it can be difficult for the practitioner to know how close the tip of the endodontic instrument (e.g., an apical file) is to the apex. It is important for a practitioner to know the working length of the canal so that he or she does not perforate the apex during the process of instrumentation, which would allow treatment agents, tooth debris, infected pulp, and rinsing solutions to escape past the apex into the bone. Were such materials to exit the apex of the tooth and enter the bone, the chance of re-infection is greatly increased. On the other hand, at the end of the instrumentation process the clinician can make a slight opening at the apex to ensure complete elimination of the pulp and nerve tissue.

Devices for aiding the practitioner in determining where the endodontic instrument is in relation to the apex have been proposed, although each has its attendant drawbacks. As such, there continues to be a need for alternative devices.

SUMMARY

Disclosed herein are hand-held endodontic apex locator devices for use in locating the apex of a root canal, more particularly for determining a distance between the distal tip of an endodontic instrument positioned within a root canal of a tooth and an apex of the root canal. Also disclosed are methods of manufacturing the hand-held endodontic apex locator devices and methods for determining a distance between the tip of an endodontic instrument inserted within a root canal of a tooth and an apex of the root canal.

According to one embodiment, a hand-held endodontic apex locator device is provided that communicates to a practitioner a distance between an endodontic instrument inserted within a root canal of a tooth and an apex of the root canal. The hand-held device includes (1) an elongate housing extending between a proximal gripping end and a distal end and configured to be gripped by a hand; (2) electronic circuitry disposed within the elongate housing; (3) a display disposed on or in the elongate housing for displaying a distance between an endodontic instrument inserted within a root canal of a tooth and an apex of the root canal during use; (4) an apex locator electrode extending from the distal end of the housing for contacting an electrically conductive endodontic instrument when inserted within a root canal of a tooth during use; and (5) a grounding electrode flexibly extending from the housing so that the grounding electrode can be electrically coupled to a patient.

According to one embodiment, the hand-held endodontic apex locator device includes an elongate housing having a generally straight configuration that extends along a longitudinal axis. The elongate housing can be essentially pen-shaped so that the elongate housing is tapered towards the distal end so that the proximal end has a larger diameter than the distal end. The apex locator electrode can include a proximal end that is adjacent to and substantially flush with the distal end of the housing. It can be tapered towards a distal end or it can have a forked distal end with a pair of spaced- apart prongs. According to one embodiment, the device may include a removable core assembly disposed within the elongate housing for holding the electronic circuitry and at least one battery.

An auxiliary apex locator electrode can be provided and can be extend from the housing. In one embodiment, the grounding electrode and auxiliary apex locator electrode can be connected by corresponding wires to a common bipolar jack that mates with a corresponding receptacle disposed at the proximal end of the housing. According to one embodiment, the auxiliary apex locator includes a file clip. The grounding electrode may comprise a lip hook or grounding pad.

The elongate housing can be formed of one or more pieces of machined aluminum or molded plastic. According to one embodiment, the housing comprises two sections, a proximal housing section for holding the electronic circuitry and display and a selectively detachable distal section attached to the apex locator electrode that permits sterilization of the distal housing section and apex locator electrode when detached from the proximal section (e.g., by autoclaving).

According to one embodiment, the hand-held endodontic apex locator device includes a display comprised of a plurality of display lights that are selectively illuminated to indicate a distance between an endodontic instrument inserted within a root canal of a tooth and an apex of the root canal during use. The display lights (e.g. , LEDs) may be positioned on a board with the electronic circuitry. A display frame can be rigidly disposed within the housing for holding the display lights or windows in a desired orientation relative to the housing. In the case where the housing has a substantially circular cross-section, the display frame provides a stop that prevents free rotation of the removable core assembly when inserted in the housing.

A hand-held endodontic apex locator can be manufactured by (1) providing an elongate housing extending between a proximal gripping end and a distal end and configured to be gripped by a hand; (2) positioning a display on or in the elongate housing for displaying a distance between an endodontic instrument inserted within a root canal of a tooth and an apex of the root canal during use; (3) placing electronic circuitry within the elongate housing; (4) placing an apex locator electrode at the distal end of the housing for contacting an electrically conductive endodontic instrument when inserted within a root canal of a tooth during use; and (5) attaching a grounding electrode to the housing so that the grounding electrode can be electrically coupled to a patient.

The length of a root canal of a patient's tooth can be determined by (1) providing a hand-held endodontic apex locator device; (2) inserting an endodontic instrument into a root canal of the patient's tooth; (3) electrically coupling attaching the grounding electrode to the patient's body; (4) contacting the apex locator electrode to an exposed metal portion of the endodontic instrument; (5) the electrical circuitry determining a distance between a distal tip of the endodontic instrument and an apex of the root canal of the patient's tooth; and (6) the display providing visual indicator of the distance between a distal tip of the endodontic instrument and the apex of the root canal. The position of the endodontic instrument within the root canal of the patient's tooth can be altered and the modified distance between a distal tip of the endodontic instrument and the apex of the root canal can be determined in the same way. According to one embodiment, the hand-held endodontic apex locator may be configured to provide an aural sound at least partially corresponding to the distance between a distal tip of the endodontic instrument and the apex of the root canal.

These and other advantages and features of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the manner in which the above recited and other benefits, advantages and features of the invention are obtained, a more particular description of the invention briefly described above will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. Understanding that these drawings depict only typical embodiments of the invention and are not therefore to be considered limiting of its scope, the invention will be described and explained with additional specificity and detail through the use of the accompanying drawings, in which:

Figures 1A and IB are perspective view of exemplary hand-held endodontic apex locator devices shown resting in a holder; Figure 2 is an exploded view of an exemplary hand-held endodontic apex locator device;

Figure 3 is a perspective view of a partially disassembled exemplary handheld endodontic apex locator device showing a removable core assembly for holding the electronic circuitry of the hand-held endodontic apex locator device and one or more batteries;

Figure 4 is a cross sectional view taken along line 4—4 of the housing of the exemplary hand-held endodontic apex locator device shown in Figure 3;

Figure 5 is an exploded view of a proximal end of an exemplary hand-held endodontic apex locator device, a grounding electrode, an auxiliary apex locator electrode, and a coupling wire assembly;

Figure 6 is a perspective view of an exemplary one-piece housing of hand-held endodontic apex locator device;

Figure 7 is a perspective view of an exemplary two-piece housing of handheld endodontic apex locator device comprising proximal and distal housing sections;

Figure 8 is an exploded view of a two-piece housing of an exemplary handheld endodontic apex locator device and an apex locator electrode;

Figures 9A and 9B illustrate exemplary methods of using a hand-held endodontic apex locator device in which an apex locator electrode at the distal end is contacted with an endodontic instrument positioned in a root canal of a tooth;

Figure 10 illustrates an exemplary alternative method of using a hand-held endodontic apex locator device in which an auxiliary apex locator electrode is clipped onto a shank of an endodontic instrument positioned in a root canal of a tooth;

Figures 11A-11D depict different embodiments of exemplary apex locator electrode tips;

Figure 12 illustrates an exemplary grounding lip hook for placement over a patient's lip to complete an electrical circuit during use of a hand-held endodontic apex locator device according to the disclosure; and

Figures 13A-13C illustrate an exemplary endodontic file clip of an auxiliary apex locator electrode for clipping onto a shank of an endodontic instrument during use of a hand-held endodontic apex locator device according to the disclosure. 5 DETAILED DESCRIPTION

The present invention is directed to hand-held endodontic apex locator devices for use in communicating to a practitioner the distance, if any, that remains between the tip of an endodontic instrument inserted within a root canal of a tooth and an apex of the root canal. The invention also relates to methods of manufacturing the handle* held endodontic apex locator devices. The invention also relates to methods for determining the distance, if any, that remains between the tip of an endodontic instrument inserted within a root canal of a tooth and an apex of the root canal.

In one embodiment, the hand-held device includes an elongate housing extending between a proximal gripping end and a distal end. Advantageously, a 15 display for displaying a distance between an endodontic instrument inserted within a root canal and the canal apex is provided on the hand-held device itself. The device further includes an apex locator electrode at the distal end of the elongate housing. The apex locator electrode is configured for contacting an electrically conductive endodontic instrument (e.g., an endodontic file such as an apical file) that is inserted 20 within the root canal of a tooth during use.

According to one embodiment, the apex locator electrode is connected to a removable distal sleeve that separates the electrode from electronic components contained in the elongate housing and the display portion. This permits the electrode and sleeve to be sterilized separately from the electronic components and display, 25 such as by autoclaving and/or immersing in a sterilizing liquid. Alternatively, the electrode may be removably attached to the elongate housing so as to be removable for sterilization by itself. In yet another embodiment, the entire unit, including the elongate housing, electronics and display, can be configured to be autoclavable. In another embodiment, an auxiliary apex locator electrode attached to a flexible lead 30 wire can extend from the device for attachment to an endodontic instrument without having to place the elongate housing inside a person's mouth.

The device also includes a grounding electrode or port for receiving such a grounding electrode. The grounding electrode may be configured for electrical connection to the body of the patient (e.g., a lip hook). The grounding electrode may 35 flexibly extend from the housing (e.g., through a corded type connection). This provides flexibility in orientation between the hand-held device and the grounded electrode, which is attached to the patient (e.g., through a lip hook). The grounding electrode may comprise any suitable configuration. For example, in one embodiment, it may include gripping means for touching the lip or other tissue of the patient. In another embodiment, the grounding electrode may comprise a pad which is electrically coupled to the patient. Other suitable grounding electrode configurations will be apparent to one of skill in the art in light of the present disclosure.

Reference is now made to the drawings, which show illustrative and non- limiting embodiments of the disclosed invention.

Figure 1A illustrates a first exemplary hand-held endodontic apex locator device 100 shown resting in a cradle 1 10 for convenience in storage and use. Apex locator device 100 includes a hollow elongate housing 102 configured to be gripped by a hand and that extends between a proximal gripping end and a distal end. The elongate housing has a generally straight configuration that extends along a longitudinal axis and is approximately pen-shaped (e.g., the elongate housing is tapered towards the distal end so that the proximal end has a larger diameter than the distal end). According to one embodiment, housing 102 is formed of a single piece of machined aluminum or molded plastic. The proximal end of housing 102 can have a diameter in a range of about 10 mm to about 40 mm, preferably in a range of about 1 mm to about 30 mm.

Extending from a distal end of elongate housing 102 is an apex locator electrode 104, which is substantially flush with the distal end of the housing and is designed for making contact with an electrically conductive endodontic instrument inserted within a root canal of a tooth during use. Apex locator electrode 104 is tapered towards a distal end. Alternatively, the apex locator electrode can include a forked distal end with a pair of spaced-apart prongs (not shown). When housing 102 is metal, the device may further include insulation (not shown) between the distal end of housing 102 and apex locator electrode 104 to keep them electrically isolated.

Elongate housing 102 encloses electronic components (not shown) for controlling operation of the device. Elongate housing 102 may also enclose a portable power source (not shown), such as one or more batteries and/or capacitors. A grounding electrode (not shown) can flexibly extend from housing 102 for electrically coupling and grounding to a patient. Display lights 106 are disposed on or illuminate through housing 102 in a display region 108 (e.g., recess) for indicating to a user the distance between the distal tip of an endodontic instrument inserted within a root canal of a tooth and the apex of the root canal. In use display lights 106 can be selectively illuminated to indicate the distance between the tip of the endodontic instrument and the apex of the root canal. For example, illumination of a first light 106 can indicate a first distance (e.g., 3.0 mm) between the endodontic instrument tip and the root canal apex. Illumination of a second light 106 (e.g., alone or in combination with illumination of the first light) can indicate a second distance (e.g., 2.5 mm) between the endodontic instrument tip and the root canal apex. Illuminations of third, fourth, fifth, or sixth lights 106 (alone or in combination with other lights) can indicate third, fourth, fifth, or sixth distances (e.g., 2.0 mm, 1.5 mm, 1.0 mm, or 0.5 mm) between the endodontic instrument tip and the root canal apex. Illumination of a seventh light 106 (alone or in combination with other lights) can indicate that the apex has been reached (e.g. , distance - 0.0 mm). Finally, illumination of an eighth light 106 can indicate that the endodontic instrument has perforated the apex and extends out of the apex. As the distance between the endodontic instrument tip and apex shortens, the color of subsequently illuminated lights may change an a signal or warning to the practitioner (e.g., from blue to amber). A special light color (e.g., green) may be illuminated when the apex has been reached but is not perforated. A warning light color (e.g., red) may be illuminated if the endodontic instrument tip extends beyond the apex (i.e., has performated the apex).

Figure IB illustrates another exemplary embodiment of a hand-held endodontic apex locator device 120 that is similar to hand-held endodontic apex locator device 100 shown in Figure 1A. Device 120 is also shown resting in a cradle 130 for convenience of storage and use. One difference is that the elongate housing 122 of device 120 shown in Figure IB is a multi-part housing that includes proximal housing section 122a and a distal housing section 122b from which the apex locator electrode 124 extends. This permits distal housing section 122b carrying apex locator electrode 124 to be selectively removed from proximal housing section 122a for separate cleaning (e.g., by autoclaving and/or use of liquid disinfectants, which might cause harm to the electronic components and/or display lights). Nevertheless, it is within the scope of the disclosure to provide a single piece housing 102 as in Figure 1A that is fully autoclavable or sterilizable using liquid disinfectant without damage to the electronic components and display lights.

Proximal housing section 102a carries electronic components (not shown) for controlling operation of the device. Proximal housing section 102a may also carry a portable power source (not shown), such as one or more batteries and/or capacitors. A grounding electrode (not shown) can flexibly extend from housing 102 (e.g., proximal housing portion 102a) for electrically coupling and grounding to a patient. Display lights or windows 126 are disposed on or in proximal housing section 122a. The electronic circuitry and display lights of the embodiment shown in Figure IB can operate in similar fashion as in the embodiment shown in Figure 1A.

Figure 2 is an exploded view of an exemplary hand-held endodontic apex locator device 200, such as the device depicted in Figure IB. Endodontic apex locator device 200 includes a multi-part elongate housing 202 composed of proximal housing section 202a and distal housing section 202b. Distal housing section 202b comprises a hollow sleeve having a shape at a proximal portion that corresponds to and is slidable attachable over a complementary shaped distal portion of proximal housing section 202a. An apex locator electrode 204 includes a proximal stem portion 204a, which is inserted into a passage through distal end distal housing section 202b in order to be in electrical communication with electronic circuitry (discussed below), and a distal tip portion 204b that extends from distal housing section 202b and can be placed into contact with an endodontic instrument during use. A hollow coupling tube 205 is attachable to a distal end of distal housing section 202b for receiving proximal stem portion 204a of apex locator electrode 204. Corresponding threads can be included to thrcadably engage apex locator electrode 204 to coupling tube 205 when assembled.

Proximal housing section 202a further includes a plurality of recesses 206 for receiving therein corresponding display lights or windows 208. A display frame 210 that carries display lights or windows 208 can be fixedly disposed within proximal housing section 202a for holding display lights or windows 208 in a desired orientation relative to proximal housing section 202a. As in other embodiments, the ability to selectively attach or remove distal housing section 202b from proximal housing section 202a permits separate autoclaving and sterilization of distal housing section 202b and apex locator electrode 204.

Hand-held endodontic apex locator device 200 further includes a removable core assembly 212 that can be selectively inserted into and removed from multi-part elongate housing 202 (e.g., proximal housing section 202a). This permits a user to replace or service the power source as needed (e.g., replacement of batteries) and also perform other maintenance as needed. Core assembly 212 includes first core section 212a and second core section 212b, which, when assembled together, houses and/or support electronic circuitry board 214 and one or more batteries and/or capacitors (not shown). According to one embodiment, first and second core sections 212a, 212b can be held together by a screw 216 at or near a distal end and by an end ring 218 at a proximal end. A swivel bar 220 attached to end ring 21 8 provides for easy grasping of core assembly 212 when selectively inserting or removing core assembly 212 from housing 202. End ring 218 may include threads, protrusions, recesses, or other mating structure(s) 222 that correspond to complementary mating structure(s) 224 at the proximal end of proximal housing section 202a. Rotation of end ring 218 relative to proximal housing section 202a permits selective locking or unlocking of end ring 218 relative to proximal housing section 202a in order to selectively lock and unlock core assembly 212 relative to housing 202.

Electronic circuitry board 214 can support or include any desired electronic circuitry, such as one or more processors, one or more memory chips, and programmed and/or programmable instructions (e.g., firmware), and the like for processing electrical signals produced during use in order to determine the distance between the tip of the endodontic instrument disposed within a root canal and the apex of the root canal. Electronic circuitry board 214 may also support or include lights, such as light emitting diodes (LEDs) 228, which can be selectively illuminated during use in order to indicate a distance between an endodontic instrument tip and a root canal apex.

Figure 3 illustrates a partially disassembled exemplary hand-held endodontic apex locator device 300, which includes an elongate housing 302 (e.g., composed of proximal housing section 302a and distal housing section 302b). An apex locator electrode 304 extends from a distal end of elongate housing 302. Elongate housing 302 includes recesses 306 for receiving therein corresponding display windows (not shown). This holds a display frame (not shown) in a fixed orientation relative to housing 302. A removable core assembly 312 is shown removed from housing 302 and loaded with batteries 313. On the side opposite the batteries are disposed a plurality of LEDs (not shown) that can be selectively illuminated and seen through corresponding display windows when assembled during use.

Core assembly 312 includes first core section 312a and second core section 312b held together by a screw 316 near the distal end and by end ring 318 at the proximal end. A swivel bar 320 attached to end ring 318 facilitates grasping of core assembly 312 when selectively inserting and removing it from housing 302. End ring 318 includes mating structure 322 corresponding to complementary mating structure 324 at the proximal end of housing 302. Rotation of end ring 318 relative to housing 302 permits selective locking and unlocking of end ring 318 relative to housing 302 in order to selectively lock and unlock core assembly 312 relative to housing 302.

Figure 4 shows a cross section of the exemplary hand-held endodontic apex locator device 300 of Figure 3 (renumbered as 400), which includes a hollow housing 402 having a substantially cylindrical interior cavity in the portion that receives core assembly 412 (including batteries 413). A display frame 410 that carries display windows 408 is fixedly disposed within housing 402. Not only is display frame 410 able to hold display windows 408 in a desired orientation relative to housing 402, display frame 410 also forms a non-cylindrical key-way that has a size and shape that permits selective insertion and withdrawal of core assembly 412 but which prevents free rotation of core assembly 412 within housing 402. This facilitates manufacture, disassembly, and reassembly of the hand-held endodontic apex locator device. It also maintains proper alignment between the LEDs of core assembly 412 and display windows 408 when assembled.

Figure 5 is an exploded view of an electrical coupling assembly 500 including proximal housing end 502 of an exemplary hand-held endodontic apex locator device, a grounding electrode 504, an auxiliary apex locator electrode 506, and coupling wire assembly 508. Proximal housing end 502 includes a female receptacle 510 for receiving and electrically coupling with corresponding bipolar male plug 512 of coupling wire assembly 508. When plug 512 is received in receptacle 510 grounding electrode 504 and auxiliary apex locator electrode 506 are in electrical communication with electronic circuitry of the hand-held endodontic apex locator device.

The grounding electrode 504 in this embodiment is a lip hook designed to hook or clip over the over a patient's lip during use. Alternatively, grounding electrode 504 can include other configurations known in the art for grounding an electrosurgical device to a patient, such as a grounding patch (not shown). A portion of grounding electrode 504 can be received within and electrically coupled to a female receptacle 514 at the end of first wire branch 516a of coupling wire assembly 508. Alternatively, the grounding electrode can be electrically coupled to coupling wire assembly 508 using any coupling means known in the art.

Auxiliary apex locator electrode 506 in this embodiment includes a file clip assembly 520 that includes a biased hooked wire portion 522 that is selectively extendable from and retractable within wire housing 524 by selectively depressing and releasing button 526 at a proximal end 528 of file clip assembly 520. Auxiliary apex locator electrode 506 includes a plug member 530 (e.g., female plug) designed to be mechanically and electrically coupled to a corresponding plug member 532 (e.g., male plug) at the end of second wire branch 516b of coupling wire assembly 508. Alternatively, the auxiliary apex locator electrode can be coupled to coupling wire assembly 508 using any coupling means known in the art.

Figure 6 illustrates an exemplary one-piece housing 600 of a hand-held endodontic apex locator device. One-piece housing 600 includes a proximal end 602 that is substantially flat and circular, which advantageously permits it to fit within a corresponding cradle (not shown) during use. Housing 600 further includes a hollow distal end 604 for receiving therein a portion of an apex locator electrode (not shown). Housing 600 further includes recesses 606 for receiving therein corresponding display lights or windows (not shown). A recessed section 608 can be provided, such as for aesthetic appeal and/or to receive a decal or printing with display information.

Figure 7 illustrates an exemplary multi-piece housing 700 of a hand-held endodontic apex locator device composed of a proximal housing section 702a and a distal housing section 702b. Proximal housing section 702a can have a substantially flat and circular proximal end, which advantageously permits it to fit within a corresponding cradle (not shown) during use. Distal housing section 702b includes a hollow distal opening 704 for receiving therein a portion of an apex locator electrode (not shown). Proximal housing section 702a further includes recesses 706 for receiving therein corresponding display lights or windows (not shown). Distal housing section 702b also includes a mating depression 708 that protrudes inwardly for mating with a corresponding mating depression (not shown) of proximal housing section 702a in order to hold the two sections together during use in a releasable locking relationship.

Figure 8 is an exploded view of an exemplary multi-piece housing 800 of a hand-held endodontic apex locator device composed of a proximal housing section 802a and a distal housing section 802b. Proximal housing section 802a can have a substantially flat and circular proximal end, which advantageously permits it to fit within a corresponding cradle (not shown) during use. Distal housing section 802b includes a hollow distal opening 804 for receiving therein an insertion portion 812 of an apex locator electrode 814. Proximal housing section 802a further includes recesses 806 for receiving therein corresponding display lights or windows (not shown). Distal housing section 802b includes a includes a mating depression 808 that protrudes inwardly for mating with a corresponding mating depression 810 in proximal housing section 802a in order to hold the two sections together during use in a releasable locking relationship.

Figures 9A and 9B illustrate exemplary methods of using a hand-held endodontic apex locator device. In Figure 9A hand-held endodontic apex locator device 900 is held by the hand of a person and a pointed apex locator electrode 904a is contacted with a distal end of an endodontic instrument 906 positioned in a root canal of a tooth 908. The distal end of endodontic instrument 906 is advantageously made of an electrically conductive material (e.g., metal) and is electrically coupled with a metallic shaft portion of endodontic instrument 906 positioned within the root canal of tooth 908. Apex locator electrode 904a applies a desired electronic signal to the endodontic instrument 906 in order to assist in determining the distance between a distal tip of endodontic instrument 906 and the apex of the root canal. Typically a grounding electrode (not shown) is attached to the patient in an appropriate location in order to complete the electrical circuit with apex locator device 900. In Figure 9B hand-held endodontic apex locator device 900 is held by the hand of a person and a forked apex locator electrode 904b is contacted with an endodontic instrument 906 positioned in a root canal of a tooth 908, more particularly a portion of the metal shaft or shank below the head portion. The apex locator electrode 904b applies a desired electronic signal to the endodontic instrument 906 in order to assist in determining the distance between a distal tip of endodontic instrument 906 and the apex of the root canal. Agrounding electrode (not shown) is attached to the patient in an appropriate location to complete the electrical circuit with apex locator device 900.

Figure 10 illustrates an exemplary alternative method of using a hand-held endodontic apex locator device in which an auxiliary apex locator electrode 1004 coupled to a housing of the device (not shown) is clipped onto a conductive shank of an endodontic instrument 1006 positioned in a root canal of a tooth 1008. The apex locator electrode 1004 applies a desired electronic signal to the endodontic instrument 1006 in order to assist in determining the distance between a distal tip of endodontic instrument 1006 and the apex of the root canal. Typically a grounding electrode (not shown) is attached to the patient in an appropriate location in order to complete the electrical circuit with the apex locator device.

Figures 11A-1 1D illustrate different embodiments of exemplary apex locator electrode tips 1100. Figure 1 1A illustrates a first electrode tip 1 100a having a proximal stem portion 1 102a, which is placed in electrical communication with electronic circuitry of a hand-held endodontic apex locator device as disclosed herein, and a distal tip portion 1 104a that can extend from a housing of the locator device (not shown) and for placement in contact with an endodontic instrument during use. The proximal stem portion 1102a has a first diameter size that corresponds to a complementary receptacle (not shown) of a hand-held endodontic apex locator. The distal tip portion 1 104a is shown as conical in order to provide desired functionality and performance during use. It will be understood, however, that the distal tip portion can have any desired shape to provide a desired functionality and performance during use.

Figure 1 IB illustrates a second electrode tip 1 100b similar to first electrode tip

1 100a and having a second proximal stem portion 1102b, which is placed in electrical communication with electronic circuitry of a second hand-held endodontic apex locator device as disclosed herein, and a distal tip portion 1 104b that can extend from a housing of the locator device (not shown) and for placement in contact with an endodontic instrument during use. Second proximal stem portion 1102a has a second diameter size that corresponds to a second complementary receptacle (not shown) of a second hand-held endodontic apex locator.

Figure 1 1 C illustrates a third electrode tip 1100c having a proximal stem portion 1 102c, which is placed in electrical communication with electronic circuitry of a hand-held endodontic apex locator device as disclosed herein, and a distal tip portion 1 104c that can extend from a housing of the locator device (not shown) and for placement in contact with an endodontic instrument during use. The distal tip portion 1104c includes a pair of spaced-apart prongs 1106a that form a space therebetween that can receive the shank or other portion of an endodontic instrument during use. Prongs 1 106a can advantageously be engaged with an endodontic instrument in a semi-restricted relationship in order to more securely hold electrode tip 1100c in contact with the endodontic instrument during the procedure.

Figure 11D illustrates a fourth electrode tip HOOd having a proximal stem portion 1 102d, which is placed in electrical communication with electronic circuitry of a hand-held endodontic apex locator device as disclosed herein, and a distal tip portion 1 104d that can extend from a housing of the locator device (not shown) and for placement in contact with an endodontic instrument during use. Distal tip portion 1104d includes a pair of diverging prongs 1106b that form a space therebetween that can receive the shank or other portion of an endodontic instrument during use. Prongs 1106b can advantageously be engaged with an endodontic instrument in a semi- restricted relationship in order to more securely hold electrode tip 1100c in contact with the endodontic instrument during the procedure.

Figure 12 illustrates an exemplary grounding lip hook 1200 placed over a patient's lip 1202 in order to complete an electrical circuit during use of a hand-held endodontic apex locator device according to the disclosure.

Figures 13A-13C illustrate an exemplary endodontic file clip 1300 for use in clipping onto a shank 1302 of an endodontic instrument during use of a hand-held endodontic apex locator device according to the disclosure. Figure 13A shows file clip 1300 in a closed configuration in which a hooked electrode wire 1304 is retracted within a housing 1306 prior to deployment. A biasing mechanism, such as for example an internal spring (not shown) within proximal end 1308 of endodontic file clip 1300, biases hooked electrode wire 1304 toward and into the retracted position. As illustrated in Figure 13B, depressing a release button 1310 extending from proximal end 1308 of endodontic file clip 1300 causes hooked electrode wire 1304 to extend beyond housing 1306 during deployment. As illustrated in Figure 13C, removing force from release button 1310 permits the biasing mechanism (not shown) to at least partially retract hooked electrode wire 1304 back into housing 1306 in order to reliably attach to and grip shank 1302 of an endodontic instrument during use. When it is desired to remove hooked electrode wire 1304 from shank 1302 of an endodontic instrument, release button 13 10 is depressed and hooked electrode wire 1304 is removed from shank 1302.

According to the exemplary embodiments disclosed herein, the hand-held device may have an elongate, generally pen shape (e.g., much like a pen for writing), having a substantially round cross-section (e.g., generally circular or ellipsoid) that tapers from the proximal end (which has the greatest transverse dimension thickness) towards the distal end, where the apex locator electrode is. In one embodiment, the proximal end of the device may be substantially flattened and may include a female plug for attachment of cords (e.g., a grounding electrode and/or auxiliary apex locator electrode flexibly coupled to the proximal end of the device). The auxiliary apex locator electrode may be used instead of the main apex locator electrode at the distal end of the housing depending on practitioner preference.

The device may include a power cord for providing power to the device or, as shown in the drawings, it may include a battery compartment within the housing (e.g., for holding 2 AA or AAA batteries). A battery powered device may be preferred as it is not tethered to a power outlet but permits the hand held-device to be easily carried and maneuvered without the limitations associated with a power cord.

As illustrated in the drawings, the hand-held device includes a display for indicating distance between a distal tip of an endodontic file or other instrument and the apex of a root canal. The display may include color coded LEDs or other lights associated with the display that indicate to the practitioner how close the distal tip of the file is to the apex. For example, the distance may be communicated to the practitioner in 0.5 mm increments (e.g., 3.0 mm, 2.5 mm, 2.0 mm, 1.5 mm, 1.0 mm, 0.5 mm or 0.0 mm). Apex out means the apex has been perforated. A display light may illuminate as each 0.5 mm increment is passed. For example, at 3 mm a first blue light is illuminated, at 2.5 mm a second blue light illuminates, at 2 mm a third blue light illuminates, at 1.5 mm a fourth blue light illuminates, at 1 mm a first yellow light illuminates, at 0.5 mm a second yellow light illuminates, at 0.0 mm a green light illuminates indicating the apex has been reached, and beyond the apex a red warning light illuminates. The series of blue, yellow, green, and red lights is illustrative, although it will be understood that other colors may be employed. In addition, one or more of the threshold values (e.g., each 1 mm or each 0.5 mm) may be accompanied by an audible marker (e.g., a beep) for the practitioner. Of course, in other embodiments, distances may be communicated in increments other than 0.5 mm (e.g. 1 mm, 0.25 mm, or 0.1 mm). In addition, in one embodiment, the increments may change as the apex is approached (e.g., 0.5 mm increments up to 0.5 mm and then 0.1 mm increments between 0.5 mm and the apex).

Providing the display on the hand-held device is very convenient for the practitioner as he or she is not required to look away from the vicinity of the apex locator electrode tip when contacting the tip with the endodontic instrument in order to read the display, which indicates how far from the apex the distal end of the instrument is. Other display configurations that may be disposed directly on the handheld device will be apparent to one of skill in the art. For example, the display may alternatively provide a simple digital or analog display of the distance remaining between the distal end of the endodontic instrument inserted within the root canal of the tooth and the apex of the canal. In addition, other colored lights, other sounds, and/or other increments (e.g., 1 mm, 0.25 mm, 0.1 mm, etc.) could alternatively be employed.

Measurement of the distance between the distal end of the inserted endodontic instrument and the apex may be calculated according to any suitable algorithm known in the art. According to one embodiment, a measured electrical impedance or resistance can be correlated to the distance between the distal end of the endodontic instrument and the apex of the root canal (or radicular canal). Exemplary algorithms and methods for calculating such a distance are disclosed in PCT Publication WO 2007/028217, and U.S. Patent Publication Number 2009/0142726, which are herein incorporated by reference in their entirety.

The housing may be formed of any suitable material, such as plastic or metal. In one embodiment, the housing may be a single piece or it may contain multiple pieces. In one embodiment the housing comprises an aluminum alloy. Aluminum alloys provide a housing that is sufficiently sturdy for use in the dental practice where instruments are often subjected to conditions or situations that might damage, blemish or otherwise cause deformations. Aluminum alloys typically include alloying metals that increase the toughness and other properties of the material. Examples of metals that can be alloyed with aluminum or other base metals include, but are not limited to, zinc, magnesium, copper, titanium, zirconium, and combinations of these. In one embodiment, the aluminum alloy is an alloy selected from the ANSI 6000 or 7000 aluminum alloy series. In one embodiment, the aluminum alloy may be ANSI aluminum alloy 6061, 6033, 6013, 6020, 7075, 7068, and/or 7050 or any alloy having sufficient strength. In yet another embodiment, the device body may comprise a ceramic fiber (e.g., carbon fiber, boron fiber, or boron nitride fiber). Machining the body as a single piece of aluminum material provides excellent strength and durability so that the housing will not easily crack, chip, or otherwise be degraded during normal use, or even what might be considered abuse.

The housing may include a threaded coupling at the distal end (e.g., a female threaded opening) for receiving a correspondingly threaded coupling on the proximal end of the apex locator electrode. An insulating o-ring (e.g., of rubber, silicone, or other elastomeric material) may be positioned between the housing and the apex locator electrode to electrically isolate the electrode from the housing, particularly where the housing is formed of an electrically conductive material. The apex locator electrode may present a substantially flush, tapering interface when assembled onto the distal end of the housing. The distal end of the housing may be tapered and the apex locator electrode is tapered in a similar manner so that, when assembled together, the tapered apex locator electrode continues the tapered configuration of the proximally disposed distal portion of the hand-held housing. The distal end of the apex locator electrode may comprise a tapered generally conical configuration, which portion of the electrode is on the exterior of the device when assembled as shown.

According to one embodiment, the apex locator electrode may be of a different color than the adjacent hand-held housing. For example, the apex locator electrode may be gold colored (e.g., as in copper or brass) while the adjacent housing can be finished aluminum (e.g., generally silver in color), providing a color contrast between the tip of the device (i.e., the apex locator electrode) and the adjacent portion of the housing. Such a color contrast can make aid the practitioner in knowing where the electrode ends relative to the housing and in ensuring that the electrode, not the housing, is contacted with the proximal end of an endodontic instrument inserted within a root canal during use.

The proximal end of the housing may be generally cylindrical and have a thickness in the gripping portion that is in a range of about 10 mm to about 40 mm, preferably in a range of about 15 mm and about 30 mm.

Although the tip of the device including the apex locator electrode is shown as being substantially straight, in an alternative embodiment a bend (e.g., 30° or 45° or 60° from the longitudinal axis of the device) may be provided. Similarly, although the entire device as shown as being substantially straight, an alternative "gun" type configuration could be provided in which a proximal gripping handle is provided at an angle (e.g., 30° or 45° or 60°) relative to the distal end including the apex locator electrode.

As further shown in the figures, the hand-held device may be provided with a docking stand as shown for supporting the hand-held device in a generally up-right orientation. The stand may further include a lateral extension around which may be wrapped a cord associated with the hand-held device (e.g., a cord attached to a grounding electrode and/or a cord for an auxiliary apex locator electrode).

It will be appreciated that the present claimed invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative, not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes that come within the meaning and range of equivalency of the claims are to be embraced within their scope.