Laser disinfection and / or sterilization device and nanostructured light guide

Abstract

Systems, devices, and methods for more efficacious delivery and application of blue laser light for disinfection and / or sterilization in dental procedures are provided. In one example, a dental disinfection and / or sterilization device uses high peak power and energy density delivery of structured blue light into a root canal via a nanostructured light guide at irradiance levels that are expected to achieve better than disinfection (and even sterilization) levels in the main root canal, but also in the physically poorly accessed areas, since the tooth absorbs and scatters the blue light into such areas.

Description

LASER DISINFECTION AND / OR STERILIZATION DEVICE AND NANOSTRUCTURED LIGHT GUIDEBACKGROUNDCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority of US Provisional Application No. 63 / 629,164, filed September 23, 2023; US Provisional Application No. 63 / 629,458, filed October 26, 2023; US Provisional Application No. 63 / 630,045, filed December 22, 2023; and US Provisional Application No. 63 / 630,564, filed February 12, 2024. The contents of each of the foregoing provisional applications are hereby incorporated by reference in their entirety for all purposes.Field

[0002] Various embodiments of the present disclosure generally relate to the use of antimicrobial blue light (aBL) to aid in disinfection and / or sterilization. In particular, some embodiments relate to the use of a nanostructured light guide having a tapered design to uniformly scatter blue light at adequate irradiance levels within a root canal and into the dentin to achieve more efficacious disinfection and reduce root canal procedure failure rates.Description of the Related Art

[0003] Many invasive dental and medical treatments require disinfection of the area before closing, commonly defined as a greater than 99.9% reduction of bacterial infection (“log3 kill”). Desirably, sterilization would be achieved, commonly defined as a greater than 99.999% reduction of bacterial infection (“log5 kill”). Where disinfection is not achieved, reinfection of the closed area can result and may necessi tate reopening and / or further treatment.

[0004] In some endodontal and periodontal dental procedures, such as root canals, current mechanical and chemical disinfection procedures (e.g., filing, cleaning and irrigating with usually 5% sodium hypochlorite in water solution) prove inadequate in the short or long term at failure rates that can be in the 8% to 20% range or greater over time. This is reasonably believed, in large part, to be due to the inability of such disinfection procedures to adequatelytreat physically inaccessible areas, such as tubules, accessory canals and the apex anatomy (e.g., the apical foramen, which is a small opening at the tip of the root).BRIEF DESCRIPTION OF THE DR AWINGS

[0005] In the Figures, similar components and / or features may have the same reference label. Further, various components of the same type may be distinguished by following the reference label with a second label that distinguishes among the similar components. If only the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label irrespective of the second reference label.

[0006] FIG. 1A is a high-level block diagram illustrating major components of a laser disinfection device in accordance with an embodiment of the present disclosure.

[0007] FIG. IB is an example of a physical representation of laser disinfection device in accordance with an embodiment of the present disclosure.

[0008] FIG. 2 illustrates a quad-tip for use in disinfecting and / or sterilizing the root canals of a molar, for example, including multiple individual tapered micro -structured light guides coupled with an optional monolithic shared base in accordance with an embodiment of the present disclosure.

[0009] FIG. 3 illustrates light guides having a rounded bend in accordance with an embodiment of the present disclosure.

[0010] FIG. 4 illustrates an ultrasonic root canal cleaner in accordance with an embodiment of the present disclosure.

[0011] FIG. 5 illustrates a clamp-mounted version of a disposable endpiece in accordance with an embodiment of the present disclosure.

[0012] FIGs. 6A-B illustrates a glue-mounted version of a disposable endpiece in accordance with an embodiment of the present disclosure.

[0013] FIGs. 7A-B illustrates views of an example light guide with light extraction features in accordance with an embodiment of the present disclosure.

[0014] FIGs. 8A-B illustrate views of an example light guide with light extraction features in accordance with another embodiment of the present disclosure.

[0015] FIG. 9A-B illustrates examples of a light extraction feature that may be formed in the surface of a light guide in accordance with an embodiment of the present disclosure.

[0016] FIG. 10 shows measurements made by an atomic force microscope (AFM) of a chicane of a three-dimensional (3D) printed light guide molding part that may be used in connection with a manufacturing process in accordance with an embodiment of the present disclosure.

[0017] FIG. 11A is a table illustrating the parameter values for an example that takes into consideration constraints described herein and uses 19 five watt diode lasers as the source in accordance -with an embodiment of the present disclosure.

[0018] FIGs. 11B is a table illustrating the parameter values for an example that takes into consideration constraints described herein and uses 7 five watt diode lasers as the source in accordance with an embodiment of the present disclosure.

[0019] FIGs. 12A-F illustrates a molding process beginning with a 3D printed positive mold that includes orthogonal alignment V-grooves in accordance with an embodiment of the present disclosure.

[0020] FIG. 13A illustrates an electroformed mold insert after machining to a square in accordance with an embodiment of the present disclosure.

[0021] FIG. 13B is a solid wireframe drawing of a mold insert within a mold base with four alignment pins shown in accordance with an embodiment of the present disclosure.

[0022] FIG. 13C is a transparent wi reframe drawing of a mold insert, within a mold base with four alignment pins shown in accordance with an embodiment of the present disclosure.

[0023] FIG. 13D illustrates a mold insert inside the mold base in accordance with an embodiment of the present disclosure.

[0024] FIGs. 14A-K illustrate depictions of a molded light guide part before and after trimming of an LSR molded part down to its final size in accordance with an embodiment of the present disclosure.DETAILED DESCRIPTION

[0025] Systems, devices, and methods are described for the more efficacious delivery and application of blue laser light for disinfection and / or sterilization in dental procedures. As discussed above, due to the inability of current mechanical and chemical disinfection procedures to adequately address certain inaccessible areas, such as tubules, accessory canals and the apex anatomy, root canal procedures have failure rates approaching 20% or more over time.

[0026] It is well established in the literature that bacterial absorption of blue light, typically in the 400 to 450 nanometer (nm) region (or even in the range of 360 nm to 550 nm), can result in bacterial infection reduction, shown to be due to photochemical effects and suspected photophysical disruption (e.g., due to high peak power and irradiance), and consequent elimination of infecting bacteria. Photochemical effects involve blue light absorption into the bacterial cell’s chromophores (porphyrin, flavins, etc.) and that promotes further disruption of the cell, largely through reactive oxygen species (ROS). Both the effects and the required dose varies between bacteria, for example, 405 nm is appropriate for porphyrins, whereas 445 nm is more appropriate for flavins. Photochemically induced breakdown products can themselves become chromophores and further absorb blue light, perhaps in between these wavelength ranges, and cause bacterial cell death.

[0027] The dental disinfection and / or sterilization approach described herein generally uses high peak power and energy density delivery of structured blue light into the root canal at irradiance levels that are expected to achieve better than disinfection (or even sterilization) levels in the main root canal, but also in the physically poorly accessed areas, since the tooth absorbs and scatters the blue light into such areas.

[0028] In the context of a dental procedure, such as a root canal, there are a number of constraints to be considered, including the following:• Treatment Duration. While never an absolute thing, twenty minutes or less seems an appropriate time for a patient to spend immobilized during the infection reduction phase of a dental procedure. The inventor contemplates treatment times as short as approximately two minutes. • Tooth Temperature. In order to avoid damage to the periodontal ligament (or periodont), it is preferable to avoid temperatures above 47 degrees Celsius (C); however, there aresome FDA approved devices that may heat paras of the tooth structure to above 47 degrees for a short period of time. A general assumption in various examples described herein is that the mean power absorbed into the tooth under treatment is generally about 1 watt (W), and should probably not exceed approximately 3 W, though this is not a limit. For example, assuming the use of cooling by irrigation the tooth could be exposed to higher power.• Minimum Peak Power for Bacterial Destruction. Despite the tooth temperature constraint, in general, the higher the power the better. Published literature indicates that short repetitive high-power pulses are more effective than continuous wave (CW) for the same total dose in Joules (J). Effective dose energy levels reported for achieving at least disinfection and preferably sterilization for a range of bacteria encountered in dentistry are generally in the range of between about 200 J per square centimeter (cm) (J / cm2) to about 3,500 J / cm2. However, many measurements in the literature (which contain many contradictions) are being performed at the aperture and not at the surface.• Available source technology. Light-emitting diodes (LEDs), diode lasers or non-diode lasers might be considered, but current diode laser technology, efficiency, cost and lifetimes favors blue diode lasers, which are available front a number of different suppliers, for example, including OSRAM GmbH, Kyocera Corporation, Panasonic Corporation, Sharp Corporation, Nichia Corporation, and others. While generally designed for CW operation, such diodes may be overdriven in low duty cycle pulse conditions. For example, a 5 W CW laser may be overdriven by a factor up to ten in such pulse conditions, of course, with greatly reduced lifetime. In various examples described herein, a proposed application involving dental disinfection may be performed with only intermittent use of the diode laser(s). In addition, in some embodiments, multiple fiber output diode lasers (at the same or differing wavelengths) may be efficiently combined to create a single fiber source using fiber fusion technology, for example, to create an effective single fiber source with high peak power. To the extent there is available reserved power, this bundling may provide for built-in redundancy should any individual diode laser fail or degrade prematurely.

[0029] While various examples described herein are described in the context of dental procedures (e.g., a root canal procedure), the proposed laser disinfection device and novel light guide design are relevant in a diverse range of areas, including, but not limited to other medical,veterinary, photodynamic therapy, and dental disinfection and / or sterilization applications (e.g., disinfection of periodontal pockets and tooth caries).

[0030] In the following description, numerous specific details are set forth in order to provide a thorough understanding of embodiments of the present disclosure. It will be apparent, however, to one skilled in the art that embodiments of the present disclosure may be practiced without some of these specific details. In other instances, well-known structures and devices are shown in block diagram form.Terminology

[0031] Brief definitions of terms used throughout this application are given below.

[0032] The terms “connected” or “coupled” and related terms are used in an operational sense and are not necessarily limited to a direct connection or coupling. Thus, for example, two devices may be coupled directly, or via one or more intermediary media or devices. As another example, devices may be coupled in such a way that information can be passed there between, while not sharing any physical connection with one another. Based on the disclosure provided herein, one of ordinary skill in the art will appreciate a variety of ways in which connection or coupling exists in accordance with the aforementioned definition. One example of connecting or coupling two components is butt-coupling.

[0033] If the specification states a component or feature “may”, “can”, “could”, or “might” be included or have a characteristic, that particular component or feature is not required to be included or have the characteristic.

[0034] As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.

[0035] The phrases “in an embodiment,” “according to one embodiment,” and the like generally mean the particular feature, structure, or characteristic following the phrase is included in at least one embodiment of the present disclosure, and may be included in more than one embodiment of the present disclosure. Importantly, such phrases do not necessarily refer to the same embodiment.

[0036] As used herein, a ‘'light guide,” a “probe,” or a “tip” generally refers to a device used to direct light from a light source to a place where the light is needed. In various examples described herein, a light, guide receives optical input from a fiber coupled laser with associated drive electronics and controls. The light guide couples the laser light to the area to be disinfected and / or sterilized, and then distributes the laser light in that area. As described further below, in some examples, the light guide may be part of a single-use, disposable endpiece of a laser disinfection device. The light guide may comprise a nanostructured or fiber probe including a proximal portion though which light is carried and a distal portion (or tip) that produces an isotropic distribution of irradiance, light, and / or dose energy. Alternatively, the light guide may provide a configurable degree of energy along a sideemitting portion, a lower (distal or apical) portion or end, and / or, an upper (proximal or coronal) portion or end of the light guide. For example, more light may be emitted from the apical end or the coronal end or anywhere in between based on the inclusion, distribution, and / or spacing of light extraction features on the surface of the light guide.

[0037] As used herein, “light extraction features" generally refer to surface features of a light guide that cause light to be extracted from the light guide. In some embodiments, for example, in which the material from which the light guide is formed includes thermoplastics (e.g., polymethyl methacrylate (PMMA) or other acrylics, including hybrids), liquid silicone resin (LSR), or the like, the light extraction features may be in the form of steps or step-downs, giving the light guide a conical tapered shape. In other examples, the light extraction features may be surface perturbations (e.g., in the form of rings or grooves having a semi hemispherical shape).

[0038] As used herein, a “fused fiber bundle” generally refers to multiple fibers combined so as to create a single fiber source by way of a fiber fusion technology. Fiber fusion bundling is an example of such a fiber fusion technology (e.g., melting of the individual fibers together) that allows multiple fiber output diode lasers (at the same or differing wavelengths) to be efficiently combined to create a single fiber source. Fiber fusion technology provides the ability to create an effective single fiber source with high peak power, and has the advantage of redundancy should any individual diode laser fail or degrade prematurely. A fused fiber bundle may be drawn and tapered. A non-limiting example of a company performing fiber fusion bundling is 3SAE Technologies, in Franklin, TN, USA. Depending on the particular implementation, a fused fiber array may include 7, 9, 10, or 19 optical fibers (e.g., made of silica) each preferably coupled with a blue laser diode (and / or other wavelengths) and the laserdisinfection / sterilization device may include 1 to 4 bundled fiber arrays. Within a fused fiber bundle, for example, several of the fibers could individually be themselves fused (e.g., via a fused fiber coupler) and coupled to other types of laser diodes (e.g., red and / or infrared). In this manner, the laser disinfection / sterilization device could emit red and / or infrared light without diminishing the number of fibers available for carrying blue light. In addition, any or all laser diodes may be coupled to a fiber within the fused fiber bundle (e.g., via a NanoPlug fiber coupler available from Sumitomo Electric of Japan), for example, to allow field replaceability.

[0039] As used herein, a " nanostructure'' is a structure of intermediate size between microscopic and molecular structures.Example Laser Disinfection Device

[0040] FIG. 1A is a high-level block diagram illustrating major components of a laser disinfection / sterilization device 100 in accordance with an embodiment of the present disclosure.

[0041] According to one embodiment, the laser disinfection device 100 may be used to illuminate the root canal and the interior of a tooth being treated effectively distributing light at one or more wavelengths (e.g., 405 nm and 445 nm or more generally, between 390 nm to 500 nm) which has been shown to have a disinfection and / or sterilization effect on infections in root canals, accessory canals, dentin tubules, etc.

[0042] In the context of the present example, the laser disinfection device 100 includes a base station 110, a non-disposable portion, (e.g., a wand 120) and a single-use, disposable endpiece 130 that includes an interface that mates with the wand 120.

[0043] In one embodiment, the base station 110 may represent an enclosure that remains at a fixed position during treatment and is coupled to the wand 120 via a cable (not shown). In this example, the base station 110 is shown including a power supply 1 1 1 , laser diodes 112, a driver 113, a monitor 114, and a fused fiber bundle 115. Those skilled in the art will appreciate the base station 110 would typically also include other computing components (not shown) and would generally have one or more mechanical buttons or keys (e.g., to start and / or stop laser treatment). Additionally, such a base station 1 10 would generally present some form of a user interface (not shown) to provide feedback and / or receive input from the end user (e.g., a dentist,an endodontist, dental technician, or other dental professional). Such additional components are well-known in the art and outside the scope of the present disclosure.

[0044] The power supply 1 11 (and a battery (not shown)) provides power to components of the base station 110 and components of the wand 120. The power supply 1 1 1 could have laser diode drivers (e.g., driver 113) that incorporate Gallium Nitride field effect transistors (FETS) that could allow sub-nanosecond rise and fall times and nanosecond (ns) pulse widths. Other pulse rise time, pulse width, and pulse repetition frequencies, and pulse energy are contemplated.

[0045] In one embodiment, the laser diodes 112. may include one or more sets of 7, 9, 10, or 19 blue laser diodes coupled to individual optical fibers of a given fused fiber bundle of I to 4 fused fiber bundle(s) 1 15. In one example, the laser diodes comprise Gallium Nitride laser diodes, for example, 5 W CW with robust, facet passivation technology to enable 10x peak power overdrive. The longer the stripe width is, the lower the peak power on the facet will be. In some examples, optical fibers coupled to red and / or infrared laser diodes may also be fused to one or more of the optical fibers of a fused fiber bundle to facilitate selectable use of different laser light treatment.

[0046] In one embodiment, the monitor 114 may monitor temperature and / or photo diodes to detect failing laser diodes. Making use of the monitor 114, the base station 110 could then notify the factory or an end user of impending failure of a given laser diode and thus allow time for replacement without going offline. In one example, field replaceability is designed into the laser disinfection device 100.

[0047] In the context of the present example, the wand 120 contains and carries the fused fiber bundle 115 for coupling with one or more light guides 135 associated with the disposable endpiece 130. The disposable endpiece 130 is preferably a rigid or semi-rigid mounting for the fiber optic, other light guiding means, and / or root canal illumination elements. In some examples, a base or mounting portion of the disposable endpiece 130 may be mounted to the tooth being treated or an adjacent tooth, either directly, or to a dental clamp.

[0048] As described further below with reference to FIG. IB, a proximal end of the light guides 135 may be butt-coupled to the fused fiber bundle 115.

[0049] As shown, the wand 120 may also include an optional sonic transducer 121 (e.g., subsonic, ultrasonic, or megasonic), for example, to concurrently apply sonic energy to thecoupled one or more light guides 135. The application of sonic energy may enhance the ability of the light guide to remove hard and soft tissue debris and smear layer in the root canal.

[0050] The wand 120 may represent a hand-held, portable portion of the laser disinfection device 100 that may be positioned and / or held in place by the end user during treatment of the patient. As described further below, alternatively, the wand 120 may be used in a hands-free manner to allow the end user to perform other tasks (e.g., irrigation and / or cooling of the tooth at issue) during the course of laser disinfection / slerilization treatment.

[0051] In some examples, the light guides 135 may comprises an array of one or more flexible, tapered, molded, structured surface PMMA optical filaments and / or fibers that enter the root canal(s). The light emitted by the laser diodes 112 and carried via the light guides 135 may be modulated at around between 10 to 50% duty cycle with pulse widths typically in the range between about 0.5 to 30 milliseconds (ms), and more preferably at about 1-1,000 ns at 10 to 30 KHz. Many other modulation regimes are contemplated. In some examples, the pulses could be in packets with varying off times in between.

[0052] The power, irradiance, energy density, pulse duration levels, and pulse repetition frequency should not induce (or minimize to the extent possible) “photo-bleaching” of the targeted chromophores (e.g., flavins, porphyrins, and the like) as well as other targeted chromophores. As those skilled in the art will appreciate, it is desirable to avoid a bi-phasic response, for example, as described in Ahmed O. El-Gendy, Sarah Ezzat. Fatrna Abdel Sarnad, Ola Ali Dabbous, Jonathan Dahm, Michael R. Hamblin. Tarek Mohamed, “Studying the viability and growth kinetics of vancomycin-resistant Enterococcus faecalis V583 following femtosecond laser irradiation (420-465 nm),” published in Lasers in Medical Science (2024) 39: 144 and available al https: / / doi.org / 10.1007 / sl0103-024-04080-5, which is hereby incorporated by reference in its entirety for all purposes (see. also Appendix C). Similarly, the power, irradiance, energy density, pulse duration levels, and pulse repetition frequency should not overheat the periodontal ligament, while providing a dose energy density, power density, time and temperature that is both efficacious and clinically reasonable.

[0001] Various potential physical embodiments of the laser disinfection device 100 and light guides 135 that delivers laser light at adequate irradiance levels in a substantially isotropic manner are described further below.

[0002] FIG. IB is an example of a physical representation of laser disinfection / sterilization device 150 (which may be analogous to laser disinfection / slerilizationdevice 110) in accordance with an embodiment of the present disclosure. In this example, a wand 153 (which may be analogous to wand 120) is a hand-held wand, including a fused fiber bundle (not shown) (e.g., one of fused fiber bundle(s) 1 15) in which a tip 155 (which may be analogous to one of light guide(s) 135) is part of a disposable endpiece (e.g., disposable endpiece 130), coupled to the wand 153 via a tip proximal mount 154. The tip (or light guide) 155 may have a tapered nanoslructured distal portion with a metal (e.g., silver) reflector, for example, perhaps by ion plating or ion implantation means to make the back-reflected irradiation more uniform and prevent the light from being directed at sensitive portions of the area near the apex of the root canal. A proximal portion of the light guide may be substantially straight (or may be curved) and may have a smooth surface. The distal portion (that would be within the root canal during laser light treatment) of the light guide may be tapered and may include light extraction features on its surface to extract light (e.g., uniformly or in an isotropic manner) from the light guide so as to illuminate the interior of a tooth (e.g., a root canal) being treated as described further below.Example Light Guides

[0003] FIG. 2 illustrates a quad-tip 200 for use in disinfecting and / or sterilizing the root canals of a molar, for example, including multiple individual tapered micro-structured light guides 235a-d (which may be analogous to light guide(s) 135) coupled with an optional monolithic shared base 270 in accordance with an embodiment of the present disclosure. In this example, laser light 280 may be delivered in an isotropic manner by light extraction features (not shown) of the light guides 235a-d. In one embodiment, the end user may cut off one or more of the light guides 235a-d of the quad-tip 200 if fewer root canals are required to be treated. In this example, a given light guide may be in the form of tapered silicon, the surface of a portion of which (e.g., a proximal tip portion) may include surface perturbations (e.g., semi hemispherical-shaped rings or grooves) that are used to facilitate extraction of light from the light guide..

[0004] In one embodiment, the light guide terminates in a structure that, is tapered and structured. For use in connection with disinfection and / or sterilization of root canals, the portion of the light guide having light extraction features may be approximately 16 mm to 20 mm (e.g., 16.5 rnm or 16.7 mm) long, and may be conically shaped. This length allow's for multiple shaped scattering nanostructures: in the form of steps, step-downs, grooves orpreferably “chicanes.” Using curved structures, radiused or otherwise curved, facilitates not only light distribution, but also both mold production and subsequent injection molding.

[0005] In one embodiment, each of 10 to 40 nanostructure chicanes comprises two complimentary curves (e.g. 90 degrees one way followed by 90 degrees the other way). As described further below, in one example, the curves represent a 1.25 micron radius so as to create a 2.5 micron per nanostructure total ‘step’. These steps may create a tapering from a major diameter of the light guide at a proximal end, for example, from approximately between 200 to 500 microns (e.g., 300 microns) to a minor diameter at a distal end approximately between 50 to 300 microns (e.g., 100 microns).

[0006] After each chicane, the wall of the light guide taper may continue in the same conical direction. These step-downs facilitate coupling light out of the otherwise total internally reflecting light guide and allow the creation of a very uniform external light distribution (e.g., in a substantial isotropic manner) from the taper over its length, wherein (depending on the input power) the power density on the inside surface of a dental root canal is at least approximately 750 W / cm2at all distances down the taper length. For example, at a 1 ,000 W of peak power input, the radiant energy density is approximately 750 J / cm2but this is only in one example, which can be further optimized as desired. So, the range is actually from about 10 to 1,000 J / cm2.

[0007] FIG. 3 illustrates light guides 335a-d having a rounded bend (e.g., 31 1 ) in accordance with an embodiment of the present disclosure. In this example, the light guides 335a-d include a bend (e.g., 311 ) directed toward the coronal root canal opening to allow the light guides 335a-d to be independently inserted into respective root canals (not shown).

[0008] FIG. 4 illustrates a tip 400 of an ultrasonic root canal cleaner in accordance with an embodiment of the present disclosure. In one example, the tip 400 may be analogous to disposable endpiece 130 and may be screwed onto a wand (e.g., wand 120). The tip 400 may be of transparent nylon and is shown including a light guide (e.g., an insert molded optical fiber) for carrying blue light received from a fused fiber bundle 405 (which may be analogous to one of fused fiber bundle(s) 115) to the root canal (not shown) to be treated.

[0009] A tapered portion 420 of the light guide 410 may include light extraction features, for example, in the form of nanostructured curved steps as described herein. The light guide 410 may terminate or stop just after the curve 425 and the light, emits out the proximal portion (e.g., the last 16 mm to 20 mm) of the tip 400 (e.g., having a length of about 40 mm). By combining the light guide 410 with the tip 400, blue light may be synergistically incorporated for disinfection and / or sterilization in conjunction with sonic motion / agitation.

[0010] FIG. 5 illustrates a clamp-mounted version 500 of disposable endpiece 530 of a laser disinfection device in accordance with an embodiment of the present disclosure. In the context of the present example, a wand 520 (which may be analogous to wand 120) may be inserted into the disposable endpiece 530 (which may be analogous io disposable endpiece 130), so as to facilitate a hands-free method of applying aBL to a tooth (not shown) being treated, for example, when a rubber dam (not shown) is employed during the dental procedure at issue. As described above, the disposable endpiece 530 may include multiple light guides (e.g., light guide 535) for treating root canals with aBL

[0011] In this example, a pair of arms (e.g., arm 515a and arm 515b) engage forceps holes of a dental clamp 580 (e.g., a metal dam clamp) that may be used to secure the rubber dam in place. The arms 515a-b may be biased so as to provide an inward or outward retention force. The arms 515a-b may be bent open or shut (as the case may be) to slot into the forceps boles to retain the disposable endpiece 530 in place and subsequently to remove the disposable endpiece 530. If no dam is used, in an alternative mounting example, a glue-mounted version of a disposable endpiece may be glued directly to an adjacent tooth as described below with reference to FIGs. 6A-B.

[0012] FIGs. 6A-B illustrates a glue-mounted version 600 of a disposable endpiece 630 in accordance with an embodiment of the present disclosure. FIG. 6A is a front perspective view of the glue-mounted version 600 of the disposable endpiece 630 and FIG, 6B is a back perspective view of the glue-mounted version 600 of the disposable endpiece 630. In this example, the disposable endpiece 630 (which may be analogous to disposable endpiece 130) may facilitate a hands-free method of applying aBL to a tooth (not shown) being treated by gluing a base 631 (e.g., having corrugated regions on the under surface to facilitate glue engagement) to the surface of an adjacent tooth (not shown). Once secured in place, a wand(not show), analogous to wand 120 or 520, may be coupled with the disposable endpiece 630 by inserting a distal end of the wand into a receptacle or recess 632 formed within the backside of the disposable endpiece 630.10013] In this example, the light guides 635a-d (which may be analogous to light guide(s)135) are shown including a rounded bend (e.g., bend 655) so as to provide a downward bias. The light guides 635 a-d may be individually placed, for example, with tweezers into respective root canals and the bias may accommodate grea ter variability in depths of the root canals.

[0014] FIGs. 7A-B illustrates views of an example light guide with light extraction features in accordance with an embodiment of the present disclosure. In this example, the light guide may be made of plastic optical fiber (POF) and include light extraction features in the form of circumferential hemispherical-shaped grooves. In one example, the grooves may be designed with square cross-sections to facilitate machining with an electrical discharge machining (EDM) process, for example. FIG. 7B illustrates a zoomed in view of section B of FIG. 7A. In one example, each groove represents a 20-micron radius light extraction feature and such light extraction features may be spaced apart uniformly (e.g., at 80 microns apart), for example, over a 20 mm length of the light guide. In other examples, the light extraction features are non-uniformly distributed as shown in FIG. 7B.

[0015] FIGs. 8A-B illustrate views of an example light guide with light extraction features in accordance with another embodiment of the present disclosure. In this example, the light guide may be made of silicone and may include light extraction features in the form of inward steps (or step-downs) as described further herein. FIG. 8B illustrates a zoomed in view of section A of FIG. 8A. In one example, a pattern of light extraction features may be distributed uniformly throughout a 20 mm length of the light guide. In other examples, the light extraction features are non-uniformly distributed as shown in FIG. SB. Example Light Extraction Feature (e.a "(Chicane" )

[0016] FIGs. 9A-B illustrate examples of a light extraction feature that may be formed in the surface of a light guide in accordance with an embodiment of the present disclosure. In the context of the present example, the light extraction feature 900 is an inward step (or step-down) and is shown having two radii (e.g., R1 and R2) that are reversed. In one example, both Ri and R2 represent a 1.25 micron radius. Multiple such light extraction features may be repeated above and below at a distance of Y and X, respectively. X and Y may be uniform or may decrease toward the distal end of the light guide. In some examples, the two radii are spaced apart by a distance of Z, which may be 0 to 1 micron. Notably, the two radiuses could almost be perfectly reversing (potentially, truncated) radiuses with a slope at the intersection (e.g., when there is no Z).

[0017] In one embodiment, the light guide is manufactured with a mold having male features so the molded part ends up with female features as described further below.

[0018] As light traverses the light guide, the radii disturb the total internal reflection (TIR), thereby causing light to be emitted from the light guide.

[0019] In one example, the light guide has a length of about 40 mm, has a straight section, and then is tapered running from the proximal end to the distal end once the light extract features begin. For example, in one embodiment, before stepping down the proximal end may have a diameter of 200 to 500 microns (preferably, about 300 microns). In one example, the light extraction features start at about 23.3 mm from the proximal end and 30 to 50 light extraction features are employed over the course of the last 16 mm to 20 mm (e.g., 16.5 mm or 16.7 mm). After stepping down to the distal end with the light extraction features, a smaller diameter of 25 to 300 microns and preferably, 50 to 100 microns may be the result. More or fewer light extraction features may be used as desired depending on the application and the length of the light guide at issue.

[0020] Depending on the particular implementation, the steps may be substantially straight steps or may have curvature at the corners of the steps. The use of curvature advantageously provides extraction of light in a variety of broad angles.Example Constraint-Related Calculations

[0021] For purposes of illustration, the following input / output parameters are used in the context of various calculations described herein and in FIGs. 11 A-B.• PD = 1 W = Max average power allowed into the whole tooth.• Peak Power (PP) ~ 250 to 500 W = Estimated instantaneous pulse power needed to kill bacteria in a root canal.• Time (T) = 100 ns = 1e-7 s = Pulse duration (an estimate of optimum duration)• Pulse repetition frequency (PRF) - to be calculated• Duty Cycle (DC) = T / ( 1 / PRF) = T * PRF (A Valid approximation for low duty cycles)

[0022] For purposes of illustration, the following calculations may be used to solve forPRF and DC:• PD = PP * T * PRF• For PD = 1 W & T = 1e-7 s, PP * PRF = 1e7• For PP = 1000 W, PRF = 1 e4 = 10 kHz, DC = 1e-7 * 1e4 = 1e-3 = 0.1%• For PP = 500 W, PRF = 2e4 = 20 kHz, DC = 1e-7 * 2e4 = 2e-3 = 0.2%• For PP = 2.50 W, PRF = 4e4 - 40 kHz, DC = 1e-7 * 4e4 = 4e-3 = 0.4%

[0023] In one example, in order to determine a number (N) of lasers satisfying the following parameters the following calculations may be used:• PL = CW laser power in Watts• N = number of lasers required• ODF - OverDrive Factor• PP = PL * ODF * N• N = PP / (PL * ODF)• For PP = 2,50 W, PL = 5 W & ODF = 10, N = 5

[0024] It is to be noted that depending on the particular implementation pulses could be at regular intervals or in spaced pulse trains. Additionally, regardless of the timing, the constraints are PD and PP described above.

[0025] FIG. 11A is a table 1100 illustrating the parameter values for an example that takes into consideration constraints described herein and uses 19 five W diode lasers as the source in accordance with an embodiment of the present disclosure. In the example with 19 lasers, there may be a mix of laser diodes having different wavelengths. For example, there may be ten 405 nm lasers and nine 440 nm. Alternatively, there may be a combination of X laser diodes of one type, Y laser diodes of another type, and Z laser diodes of yet another selected from 380 nm to 470 nm depending on the particular needs considering 405 nm is generally more effective for porphyrins and 440 nm is generally more effective for flavins.

[0026] FIGs. 11B is a table 1150 illustrating the parameter values for an example that takes into consideration constraints described herein and uses 7 five W diode lasers as the source in accordance with an embodiment of the present, disclosure. The inventor contemplates that laser diodes will become more efficient and higher power with more robust facets, which would allow for higher peak power.High-Level Overview of Tooling Manufacturing Process for a Light Guide

[0027] This brief manufacturing overview describes the manufacturing steps to achieve molding of an example fiber optic silicone nanostructured light guide. In one example, the light guide has a conical tapered shape created by gradual step-downs (forming light extraction features within the surface of the light guide). Prior to the point at which the light extraction features are introduced on the surface of the light guide, it is desirable to have high optical clarity within the part, as well as a smooth surface along the length to ensure good internal reflection and low light leakage. In one embodiment, simply being of a conical shape creates natural light extraction from the light guide as the angles are getting steeper (exceeding the acceptance angle for TIR) as light travels through the light guide; however, this light extraction is generally not sufficient for dental disinfection and / or sterilization applications. In various examples described herein, desired light extraction is introduced in a programmable manner by defining the size of the light extraction features, the number of the light extraction features, and the distance between the light extraction features.

[0028] In one example, a positive mold of the desired silicone part is first 3D laser nanoprinted onto a glass wafer (e.g., 4 inch diameter by 170 micron-thick glass wafer with submicron surface roughness), which is then metallized and thickened by electroforming to create a metal mold (e.g., 3 mm thick) that may be attached to tooling. A non-limiting example of a company that may perform 3D two-photon laser printing is Nanoscribe (located in Germany) and their current model is called Shape.

[0029] The printed part and glass substrate is then dissolved away to leave the metal mold. This is then soldered or screwed to bar stock, and then machined to create a standard holding piece (e.g., a mold base) for mounting in the injection molding machine to be used. A non-limiting example of such an injection molding machine is manufactured by Sodick of Japan.

[0030] Finally, the molded silicone part may be trimmed, for example, as shown in FIGs. 14A-K. Further details regarding an example mold creation and injection molding process are described below with reference to FIGs. 12A-14K.

[0031] While in the context of some examples described herein, silicone is described as the material from which the light guide is molded, in other examples a variety of other materials may be used (e.g., thermoplastics). A particular example of a desirable silicone is Lumisil 7601 / 70 manufactured by Wacker of Germany.Example Molding Process

[0032] FIGs. 12A-F illustrates a molding process beginning with a 3D printed positive mold 1200 that includes orthogonal alignment V-grooves 1210a and 1210b in accordance with an embodiment of the present disclosure. The mold 1200 may be 3D printed onto a 4- inch diameter wafer with 100 nm print resolution with today’s technology. In one example, in addition to traditional vertical pins (not shown) that would typically perform macro alignment of respective mold halves, in this example, the mold 1200 may include 3D printed and electroformed orthogonal locating v-grooves ( 1210a-b) that are 3D printed the same time the light guide is 3D printed. In one embodiment, locating sub-micron tolerance pins are placed within a mold half. These high precision in-mold locating pins may be used to accurately position the mold halves with respect to each other at a micro-level. This high- precision locating to sub-micron tolerance in combination with high pressure mold halve compression together reduce the potential for production of flash as part of the injection molding process.

[0033] In the context of the present example, a metalized coating (e.g., 100 nm chromium, followed by 50 nm gold) is then applied to the 3D printed positive mold 1200. For example, the mold 1200 may be metallized and electroformed to create a metal mold (e.g., 3 mm thick). In one example, a sub-micron (e.g., 5- 10 nm) chromium coating may be deposited (e.g., by Vapor Tech of Colorado, USA) onto the mold surface by cathodic arc deposition to facilitate part extraction without tearing or deformation. In some examples, additional nickel cobalt metal is electroformed onto the mold 1200 to increase total metal thickness (e.g., to 3 mm). At this point, the original printed positive and glass waiter may be dissolved out, leaving behind a metal negative. Hot sodium hydroxide or hydrofluoric acid are considered.

[0034] The next step may involve soldering the nickel-cobalt side of the mold 1200 to a piece of copper tungsten bar stock. The solder layer may be approximately 12.5 microns of tin-silver solder. Alternatively, the two pieces may be screwed together.

[0035] At this point, insert post-machining may now be performed.

[0036] FIG. 13A illustrates an electrofornied mold insert 1300 after machining to a square in accordance with an embodiment of the present disclosure. In one example, the wafer may be cut into an insert in the form of a rounded square that is approximately 50 mm x 50 mm. Additionally, mounting screw counterbores may be added in as well as any other mounting features to facilitate mounting of the insert within a larger tool body.Final Tool Assembly

[0037] After insert post-machining, the insert may be mounted into a larger tool base as depicted in FIGs. 13B-D so that it can be loaded into an injection molding machine. The larger tool base may be 150x150 mm with 3 mm diameter channels machined into it to allow for injector insertion.Example Trimming of Fiber Ends

[0038] FIGs. 14A-K illustrate depictions of a molded light guide part before and after trimming of a molded part (e.g., LSR molded) down to its final size in accordance with an embodiment of the present disclosure. It is desirable to have the entry face (of the proximal end of the light guide) be very smooth to reduce light reflection when coupling in light from the laser system, for example, via butt-coupling with a fused fiber bundle.

[0039] FIG. 14D is a 1000x view of a step-down feature depicted within section C of FIG. 14C which shows the light guide with a straight TIR portion and a tapered, stepped nanostructured portion.Appendices

[0040] Also attached herewith are three appendices. Appendix A is a non-limiting example of Axisymmetric Finite Element Modeling of Laser-Irradiated Root. Canal Temperature Response for a particular experimental model. Appendix B is a non-limiting example of optical models of various potential embodiments and configurations of a laser disinfection device utilizing one or more light guides. Appendix C has been incorporated by reference herein above.

[0041] The drawings and the forgoing description give examples of embodiments. Those skilled in the art will appreciate that one or more of the described elements may well be combined into a single functional element. Alternatively, certain elements may be split into multiple functional elements. Elements from one embodiment may be added to another embodiment. For example, orders of processes described herein may be changed and are not limited to the manner described herein. Moreover, the actions in any flow diagram need not be implemented in the order shown; nor do all of the acts necessarily need to be performed. Also, those acts that are not dependent on other acts may be performed in parallel with the other acts. The scope of embodiments is by no means limited by these specific examples. Numerous variations, whether explicitly given in the specification or not, such as differences in structure, dimension, and use of material, are possible. The scope of embodiments is at least as broad as given by the following claims.

[0042] All examples and illustrative references are non-limiting and should not be used to limit the applicability of the proposed approach to specific implementations and examples described herein and their equivalents. For simplicity, reference numbers may be repeated between various examples. This repetition is for clarity only and does not dictate a relationship between the respective examples. Finally, in view of this disclosure, particular features described in relation to one aspect or example may be applied to other disclosed aspects or examples of the disclosure, even though not specifically shown in the drawings or described in the text.

[0043] The foregoing outlines features of several examples so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and / or achieving the same advantages of the examples introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure,and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure.APPENDIX AAxisymmetric Finite Element Modeling of Laser-Irradiated Root Canal Temperature ResponseOverview• Generated axisymmetric model for root canal irradiated by fiber to assess thermal response of dentin and bone— Simple truncated conical geometryConstant propertiesHeating profile provided by LTI Optics• Attempted to calibrate the model to several experiments reported in the literature— Model agreed fairly well with analytic studies— Model overpredicted temperatures by large amounts in experimental studies, but agrees with hand calculations. Overprediction may be due to:• Assumption of no reflection or scattering• Simplified geometry of axisymmetric model & poorly characterized geometries in experiments• Poor characterization of heating and heat loss modes in experiments• Use of water in some experiments, which absorbs some laser wavelengths strongly (Er:YAG), as well as providing some cooling benefit• Total input heating was varied from 1W to 60W to cover likely range of actual net heating scenarios— Pulse length varied from 0.5 msec to 50 msec— Duty cycle held constant at 30% (so actual absorbed power was 0.3W to 18W)Discrepancy in Heating Inputs?• 60 W irradiance profile was integrated to verify total heating• Both a discrete summation method and an integral method were used— Discrete summation approximated midpoints between zones as cylinders and evaluated the average heating at that station• Significant differences in the heating were found with both methods— 181W using discrete summation— 169W using integral method• Roughly a 3X discrepancy in heatingShort-Term Response• Results of FEA runs at 3 pulse durations w / 30% duty cycle— Power given is laser power (Laser Power x Duty Cycle = Absorbed Power)— As pulse length is reduced, dentin surface temperature variations are reduced- Steady-state heating gives a good approximation to short-pulse temperature response• Subsequently used for long-term response calculations— Bone temperature rises monotonically: peak bone temperature reaches 47.1°C @25ms pulse length at end of 5 cyclesLong-Term Response• Steady state calculation used for long-term response— Amplitude of pulsed solutions can be superposed on long-term results• Heating values here are absorbed power; they should be divided by duty cycle to get laser power• Boundary conditions on bottom and right-hand surfaces of computational domain are T = 37°C— These boundary conditions do not affect short-term results, but do influence long-term results— Least conservative assumption that can be made• However, effect of blood flow in peridontal ligament was found to be negligible - I could have underestimated its magnitudeDESCRIPTION OF ANALYSISAxisymmetric FEA Model With Heating GradientAlong Root Canal WallMaterial RegionsMesh Used In AnalysisAbsorption Coefficient Derivation• Absorption coefficient was derived to model heating distribution through tissue— Sofia et al. measured absorption through dentin at various wavelengths for a variety of teeth - absorption depth @445nm ~ 1mm- Lusche et al. measured the transmission through 0.5 mm and 1.0 mm dentin samples @445 nm, estimating 30% absorption through 0.5 mm and 67% absorption through 1 mm- Lusche et al. estimates were compared with Sofia et al. absorption coefficient with good agreement— Scattering was ignored due to 2D assumption• Absorption coefficients for other materials were estimated- Cementum: 1,1 mm absorption depth- Periodontal Ligament: 0,1 mm absorption depth- Bone: 0,83 mm absorption depthCHECK CASES (NOT UPDATED WITH NEW ABSORPTION COEFFICIENTS)• Finite element study modeling laser radiation on cylindrical section (1 mm high, 150 μm radius) of actual root geometry• Heating (1.04 MW / m2) applied on surface of dentin for 0.5 s• Fair agreement between Stanusi et al. and axisymmetric model:— Peak temperature predicted by Stanusi et al. was ~ 250°C— Peak temperature of simple axisymmetric model was 296°C• Evaluated temperature rise on exterior surface of dentin during irradiation- 150 mJ / pulse @10Hz60s exposure• Measured coronal, midroot and apical temperatures— Midroot taken here as least likely to have heating influenced by entrance or end effects— Control values used since they had no irrigation• Poorly characterized geometry, external convective environment• Large scater in dataCheck Case 3Imbedded premolars in acrylic, filled the canals with water, and measured the exterior temperature of the dentin with thermocouples Heated root canal with two lasers- Nd:YAG; Er:YAG- 1W, 1.5W, & 2W- 5s ExposureNo difference between responses to the two lasersAxisymmetric FEA Analysis overpredicts temperature rise on dentin reducing absorbed heating by 62.5% matches data fairly wellCheck Case 4:• Dentin disks cut from molars- Thicknesses: 0.5 mm, 1 mm, 1.5 mm, 2. mm— 8 mm diameter• Heated disc with Er:YAG laser— 12.7 J / cm2pulse energy density applied for 0.23 msec— 0.7854 mm2spot rastered over 6 mm diameter— 10, 15, & 2.0 Hz pulse frequencies• 5 mL / min water irrigation, but no description of application• Temperature increases are non-linear with pulse rate, suggesting temperature-dependence of material properties (unlikely due to small temperature changes) or a flaw in the test• Heating reduced to 5% of reported heating to match temperaturesSummary of Check Cases• Case 1: Romanian FEA study and this FEA study agree reasonably well, given the differences in the geometries analyzed• Case 2: Matching Israeli experimental data required ~25X reduction in input power• Case 3: Matching data from Indian researchers required 63% reduction in input power• Case 4: Matching data from Turkish study required 20X reduction in input power

Claims

CLAIMSWhat is claimed is:

1. A dental disinfection or sterilization device comprising: a plurality of laser diodes; a fused fiber bundle coupled to the plurality of laser diodes; and a nanostructured light guide having: a proximal end and a distal end, the proximal end being larger in diameter than said distal end, wherein the nanostructured light guide is coupled with the fused fiber bundle, wherein the proximal end is larger in diameter than the distal end, wherein proximal end has a substantially straight portion towards the distal end that substantially totally internally reflects photons; and a stepped tapered nanostructured feature portion that steps down in diameter towards and terminates substantially at the distal end, wherein the stepped tapered nanostructured feature portion contains a plurality of stepped chicanes that curve in substantially opposite directions to create perturbations that couple incident photons from a broad range of angles out of the stepped tapered nanostructured feature portion in a substantially isotropic manner along a length of the stepped tapered nanostructured featured portion.

2. The dental disinfection or sterilization device of claim 1, wherein the distal end has a photon reflecting coating that reflects a substantial portion of incident photons back towards the proximal end.

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