Oral care device and method

Abstract

The oral care device has an electric field generator configured to generate an electric field in the user's oral cavity based on an input control signal. The electric field is for applying a force to particles forming the biofilm or cleaning agent particles to be removed by the oral care device. A periodic control signal is generated to intermittently generate the electric field at a first RF frequency. Intermittently generating the RF electric field means that the force applied by the electric field to the particles (especially polarized particles) is itself periodic. It has been found that the periodicity of this applied force makes the breakdown of the biofilm to be removed more effective, thereby facilitating subsequent mechanical removal, for example by brushing.

Description

[Technical field]

[0001] The present invention relates to oral care devices and methods, and more particularly to devices for removing biofilm from the oral cavity. [Background technology]

[0002] It is known that radio frequency (RF) electromagnetic radiation can be used to provide cleaning functionality within the oral cavity. In particular, an oral cleaning device can include a cleaning unit, such as a head or mouthpiece portion for insertion into a user's oral cavity, the cleaning unit portion including two or more electrodes coupled to an RF signal generator. The signal generator drives the electrodes with an RF signal, which causes RF radiation to be emitted around and between the electrodes.

[0003] It is also known to deliver mouthwash to the oral cavity as part of an oral care regimen.

[0004] US10 / 201701B2 describes a prior art electric toothbrush. The toothbrush has a platen, an RF generator, two RF electrodes, and a dielectric barrier in the form of a silicone strip located between the two RF electrodes. The toothbrush also includes bristles. The dielectric barrier has a height that extends to the level of the distal ends of the bristles. The barrier ensures that the RF waves traveling between the electrodes pass over the barrier and reach the area where the bristles contact the surfaces of the teeth and gums in use.

[0005] When the RF field interacts with the surfaces of the teeth and gums, it provides a cleaning function by loosening the bonds between the surfaces and impurities in the oral cavity. In particular, the RF field thus generated can remove plaque and tartar. Tooth staining can also be reduced. Summary of the Invention [Problem to be solved by the invention]

[0006] It is known that bioparticles in biofilms to be removed (e.g. plaque and tartar), and indeed other polarizable particles such as the aforementioned detergent particles, are moved under the influence of bielectrophoretic forces. A given RF drive frequency results in a force on the particles in a particular direction. However, this direction may not be the one that optimally removes plaque, for example if it is towards the teeth, or does not result in the desired movement of the detergent particles.

[0007] Plaque usually consists of microcolonies of bacteria embedded in an exopolysaccharide (EPS) matrix. Moreover, biofilms such as dental plaque are known to be difficult to remove due to their different viscosities. For example, the adhesive strength of plaque varies greatly from place to place. In areas that are easy to reach with the bristles of a toothbrush, such as the buccal and lingual tooth surfaces, plaque is difficult to remove and the bristles must apply sufficient force to break and erode the plaque layer. In proximal and subgingival areas such as periodontal pockets, the plaque is softer. However, these areas are not cleaned because the bristles cannot reach them. Thus, these so-called hard-to-reach areas require the application of additional physical tools and principles to break and move the plaque.

[0008] There is therefore a need for means to more efficiently disrupt formed biofilms and / or to deliver detergent to the biofilm, thereby aiding in the mechanical removal of the biofilm.

[0009] EP3104807 discloses a tooth whitening device in which an AC activation signal is applied to ordinary toothpaste, for example an AC field of 300 kHz to 40 MHz is applied. The AC field can be continuous or pulsed. [Means for solving the problem]

[0010] The invention is defined by the claims.

[0011] According to an embodiment of the present invention there is provided an oral care device comprising: an electric field generator configured to generate an electric field within the oral cavity of a user based on an input control signal; a controller configured to generate an input control signal and control generation of an electric field, the electric field for applying a force to biofilm forming particles or cleaning particles to be removed by the oral care device; The controller is configured to generate a periodic control signal for intermittently generating an electric field at a first RF frequency.

[0012] This device utilizes the intermittent generation of an RF electric field. Thus, the force exerted by the electric field on the particles (especially polarized particles) is itself periodic. The periodic nature of this applied force has been found to be more effective in disrupting the biofilm to be removed, either by direct interaction of the biofilm with the particles, or by a controlled supply of detergent particles, or by controlled interaction of detergent particles with the biofilm. This facilitates subsequent mechanical removal, for example by brushing.

[0013] The detergent particles may comprise polarizable particles, or one or more non-polarizable detergent particles may be carried by a polarizable transport medium, such as a capsule.

[0014] The periodic control signal controls the timing of the generation of the RF field, and therefore the frequency of the periodic control signal is much lower than the RF frequency itself.

[0015] The electric field generator creates a field with a certain field pattern within the oral space. The field pattern depends on the control signal and the geometry of the electric field generator (e.g., the geometry or arrangement of the electrodes or coils). The field pattern includes a field strength gradient or electric field lines that, when acting on polarizable particles, define a pattern of force paths through the space. Biofilm particles or detergent particles are electrically polarizable particles and a force is applied based on the field lines and gradient.

[0016] The controller is configured to generate a periodic control signal to generate an electric field alternately at a first RF frequency and a second RF frequency.

[0017] Different RF frequencies exert different forces, and a selection of these forces can be used to create effective disruption or controlled movement or vibration of the cleaning agent particles.

[0018] There may be switching between the first and second frequencies. Alternatively, the controller may be configured to generate a periodic control signal to generate a frequency sweep between the first and second RF frequencies.

[0019] Thus, a switch or sweep of available forces and force directions can be produced.

[0020] The first RF frequency is, for example, a frequency below a threshold and the second RF frequency is a frequency above a threshold, whereby opposing dielectrophoretic forces on the particles can be generated. The dielectrophoretic effect is frequency dependent, and thus forces of opposite directions can be applied alternately. This provides an efficient collapse solution.

[0021] The threshold frequency is, for example, 1 MHz, so that at least one frequency is below 1 MHz and at least one frequency is above 1 MHz.

[0022] The frequency of the periodic control signal is in the range of, for example, 0.1 Hz to 1 kHz, for example, in the range of 1 Hz to 100 Hz.

[0023] In an alternative set of examples, the controller may be configured to generate a periodic control signal to turn on and off the generation of the electric field at the first RF frequency, such that only one frequency is used, but it is applied periodically to alternate periods of application of force with the RF electric field and periods of no application of force.

[0024] In all embodiments, the oral care device comprises: The brush head and and a motor that vibrates the brush head at a vibration frequency.

[0025] It combines the disruption of biofilms (such as plaque) and / or the delivery of cleaning agents with mechanical stripping and removal.

[0026] The frequency of the periodic control signal is, for example, equal to the vibration frequency or a subharmonic of the vibration frequency, such that the combined effect of the mechanical vibration and the electromagnetic force of the RF field exert opposing forces on the biofilm particles.

[0027] When the periodic control involves on-off periods of one RF frequency, when the RF field is turned on, a force in one direction can be generated to complement the force due to the mechanical vibration. When the RF field is turned off, a force in the opposite direction is generated by the mechanical vibration alone. Thus, even with one RF frequency, forces of alternating directions are applied to the particles.

[0028] This method can also be used to generate a net force in a preferred direction, which can be used to direct cleaning particles to a desired location or in a desired pattern of locations.

[0029] When the periodic control includes two RF frequencies or a sweep of RF frequencies, the positive and negative forces caused by the RF field can be enhanced by synchronizing with the vibration of the brush head. For example, the force due to the RF field changes from positive to negative (i.e., changes direction) at the same time that the brush head movement changes direction. With proper synchronization, the force resulting from the RF field and the force imparted to the particles from the brush movement always coincide with the direction of the brush head movement.

[0030] This drive method is more efficient at vibrating and loosening the particles within the biofilm.

[0031] The vibration frequency is, for example, in the range of 50 Hz to 1 kHz.

[0032] The electric field generator may be coupled to the brush head for movement therewith, such that particles subjected to a force from the RF electric field are effectively trapped by the force and move with the movement of the brush head.

[0033] The electric field generator may, for example, be configured to generate a non-uniform electric field having a field strength gradient in one or more directions to generate a force on the polarizable particle along the direction of the gradient.

[0034] Such a non-uniform electric field can be utilized to move electrically polarized or polarizable particles. Polarized or polarizable particles move along the direction of the electric field strength gradient due to the non-uniform force on each pole of the particle's electric dipole. Thus, the field can be configured to exhibit a field strength gradient that defines one or more gradient paths corresponding to the direction in which the force is desired to be applied. This non-uniform electric field can be utilized to move electrically polarizable or polarized particles due to the dielectrophoretic (DEP) effect.

[0035] Thus, a force can be applied to the biofilm particles to be removed, but also to the detergent particles that are delivered to the oral cavity. Thus, the field can be configured to exhibit a field strength gradient that defines one or more gradient paths towards where it is desired that those detergent particles be delivered.

[0036] In this case, the system can use an electrically polarizable capsule containing an oral therapeutic agent. The electrically polarizable capsule constitutes cleaning agent particles that are susceptible to an electric field. The capsule can be moved to desired locations in the oral cavity by a non-uniform electric field. The active agent can be deposited at those locations. This can occur without further interaction from the device. For example, the capsule is water-soluble and disintegrates upon interaction with saliva, or it can be triggered by an activation stimulus generated by the device.

[0037] The electric field generator may, for example, include one or more conductive elements electrically coupled to a controller, and the control signal may be an electrical drive signal for charging the one or more conductive elements.

[0038] For example, the oral care device may be controlled by a method, the method comprising: generating a control signal to control generation of an electric field in the oral cavity of a user, the electric field being for applying a force to biofilm forming particles or cleaning particles to be removed by the oral care device; The control signal includes a periodic control signal for generating an electric field alternately at a first RF frequency and a second RF frequency, the periodic control signal comprising: to generate a frequency switch between the first RF frequency and the second RF frequency; or for generating a frequency sweep between the first RF frequency and the second RF frequency.

[0039] The invention also provides a computer program comprising computer program code, executable on a processor or computer, the code being configured to cause the processor to carry out the method as defined above, when the processor or computer is operatively coupled to the electric field generator.

[0040] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter. [Brief description of the drawings]

[0041] [Figure 1] FIG. 2 shows a schematic diagram of elements of a first exemplary apparatus. [Diagram 2] FIG. 1 illustrates an exemplary pair of electrodes for inducing an electric field between them to achieve the dielectrophoretic (DEP) effect. [Diagram 3]FIG. 13 is a diagram showing the relationship between a force in a specific direction and a logarithmic frequency. [Figure 4] FIG. 2 shows a first embodiment of the oral care device in more detail. [Diagram 5] FIG. 2 shows a second example of an oral care device in greater detail. [Figure 6] FIG. 13 shows a third example of an oral care device in greater detail. [Figure 7] FIG. 13 illustrates a drive system for another example of an oral care device. [Figure 8] FIG. 13 shows a periodic control signal for synchronizing the operation of the vibrating brush head. [Figure 9] FIG. 13 illustrates the forces and movement directions of synchronized DEPs. [Figure 10] FIG. 7 shows a brush head having a set of bristles that lift particles in the manner depicted in FIG. 6. [Figure 11] FIG. 8 illustrates a modification to the system of FIG. 7 to implement synchronization with the vibration of the brush head. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0042] For a better understanding of the present invention, and in order to more clearly show how it may be carried into effect, reference will now be made to the accompanying drawings, which are given by way of example only, in which:

[0043] The invention will now be described with reference to the figures.

[0044] It should be understood that the detailed description and specific examples, while illustrating exemplary embodiments of the devices, systems, and methods, are for purposes of illustration only and are not intended to limit the scope of the invention. These and other features, aspects, and advantages of the devices, systems, and methods of the present invention will be better understood from the following description, the appended claims, and the accompanying drawings. It should be understood that the figures are merely schematic and are not drawn to scale. It should also be understood that the same reference numbers are used throughout the figures to indicate the same or similar parts.

[0045] The present invention provides an oral care device having an electric field generator for generating an electric field in a user's oral cavity based on an input control signal. The electric field is for exerting a force on the particles forming the biofilm or cleaning particles to be removed by the oral care device. A periodic control signal is generated for intermittently generating an electric field at a first RF frequency (i.e. the first frequency is applied in a duty cycle, with periods during which an RF field is generated at that frequency and periods during which an RF field of a different frequency or no RF field is present). This means that the force on the particles is itself periodic, which results in more effective breakdown of the biofilm to be removed.

[0046] Thus, the present invention relates to the use of the force provided by the RF electric field to assist in loosening biofilm in the oral cavity, either directly or by cleaning particles, thereby assisting in the removal of the biofilm. This application of the RF electric field may be used alone by the oral care device (e.g., it may be a pure RF treatment device or may be followed by conventional brushing), or the oral care device may achieve a combination with physical brushing. For example, the RF-based oral care device may be integrated into an electric toothbrush or mouthpiece brush device. The oral care device may also be used in combination with the delivery of oral treatment substances, such as active agents such as fluoride, whitening solutions, mouthwashes and specialized toothpastes or gels.

[0047] The invention is particularly concerned with controlling the forces resulting from the use of RF electric fields acting on biofilm particles or controlling the movement of cleaning agent particles, and therefore other functions of the oral care device, such as power brushing, will not be described in detail.

[0048] FIG. 1 illustrates generally elements of a first exemplary apparatus according to one or more embodiments.

[0049] The apparatus 8 comprises an electric field generator 16 configured to generate a first electric field 20 in space based on an input control signal.

[0050] The device further includes a controller 10 configured to generate a control signal to control the generation of an electric field 20 in the space. The electric field is for exerting a force on biofilm particles or other polarizable particles susceptible to the electric field, such as detergent particles.

[0051] The electric field generator 16 is for operation in the mouth of a user. When the electric field exerts a force on particles of the biofilm itself, the direction of the force exerted on the particles of the biofilm preferably includes at least a component that is non-normal with respect to the tooth surface, thereby providing a lateral force.

[0052] In this example, the electric field generator has two electric field generating arrangements or portions 16a, 16b, each including a first conductor 18a and a second conductor 18b configured to receive control signals from the controller 10. Each generates a respective local electric field 20 between the respective conductors for exerting a force on particles in a localized region. However, this is not required and in other examples a single electric field generating arrangement configured to generate an electric field over a single region may be provided.

[0053] In this example, device 8 has a support 12 that carries or integrates electric field generators 16a, 16b. For example, the electric field generators are carried on or integrated beneath a support surface 13 of the support. Controller 10 may be carried by or integrated into support 12, or it may be separate from the support and electrically coupled or coupleable to electric field generators 16 of the support. For example, in some cases device 8 may further include a handle or body portion to which support 12 is coupled or attached and which integrates controller 10.

[0054] 1, each electric field generating arrangement 16a, 16b of the electric field generator 16 has a separate pair of electrodes 18a, 18b separated by a space and is configured to receive a voltage supply from the controller 10 that causes charging of the electrodes. This results in an electric field 20 between the electrodes.

[0055] When the electric field 20 is generated by the field generator 16, particles that are susceptible to the electric field have a force applied to them.

[0056] There are various options based on the application regarding the shape and structure of the device 8. For example, the present invention can be embodied in a variety of different oral care devices, such as mouthpiece devices, toothbrushes, interdental cleaning devices, flossing devices, and oral irrigator devices.

[0057] FIG. 1 shows an example in the form of a mouthpiece device having an arc-shaped support 12 with a support surface 13. The arc-shaped shape allows the mouthpiece to be received in the oral cavity of a user. It can be shaped to fit the geometry or contour of the user's mouth (e.g., a particular user or a typical user). It can have an upper surface and a lower surface. The conductive elements of the electric field generator 16 can be carried by the support surface 13 of the support 12.

[0058] As will be described in more detail below, the control signal generated by the controller 10 can be dynamically varied as a function of time to dynamically control the force exerted on the susceptible particle. The control signal can be varied in time to dynamically control the manner in which the particle is polarized in the generated electric field. In particular, the polarization is frequency dependent. For example, the frequency can be controlled to vary the magnitude and sign of the force. The electric field generator 16 is thereby configured to generate a non-uniform electric field 20 (non-uniform field strength) with a field strength gradient in one or more directions to exert a force on the particle along the direction of the gradient.

[0059] Such a non-uniform electric field can exert a force on an electrically polarizable or polarized particle. A polarized particle has a force applied along the direction of the electric field strength gradient due to the non-uniform force on each pole of the particle's electric dipole. Thus, a non-uniform electric field can be used to exert a force on an electrically polarizable or polarized particle due to the dielectrophoretic (DEP) effect.

[0060] In the example of Figure 1, the electrodes 18 of each pair are different in size to facilitate a non-uniform electric field 20. This is one way to create a non-uniform electric field pattern. For example, the first electrode 18a in Figure 1 is longer than the second electrode. For example, the dimension perpendicular to the direction of separation of the pair of electrodes may be longer.

[0061] Thus, an asymmetric pair of electrodes is provided: by providing one electrode 18a that spans a greater distance along a direction perpendicular to their separation than the other electrode 18b, this results in an electric field that is more spatially widespread on one side of the separation space than the other, so that there is a net force toward the smaller electrode.

[0062] More generally, each electrode 18a, 18b of a pair may have a distinct chargeable or active area for generating an electric field 20 in the space between the pair when charged, where the chargeable or active areas of the two electrodes may differ in size. Thus, the portions of the electrodes 18a, 18b that are charged and contribute to the electric field may differ in area between the electrodes. Additionally or alternatively, the dimensional extension along a direction perpendicular to the separation between the electrodes may also differ.

[0063] It should be noted that providing electrodes of different lengths or areas is not the only way to create a spatially non-uniform electric field. Alternative means are, for example, a pair of electrodes of the same length spaced apart from each other but at an angle to each other. More generally, any electrode arrangement in which the potential gradient between the electrodes varies spatially can be used, rather than a simple parallel plate arrangement that produces a uniform electric field.

[0064] The electrodes may be plate electrodes, but one electrode of a pair of electrodes may be flat and the other may be rounded, so that the electrically active area extends around the sides of the electrodes.

[0065] The DEP effect is illustrated in FIG. 2, which shows an example of a pair of electrodes 18a, 18b separated by a space D. One electrode 18a is negatively charged and the other electrode 18b is positively charged, which induces an electric field between them. The first electrode 18a is longer than the second electrode 18b in the dimension perpendicular to the separation direction D between the electrodes. This has the effect that for a polarized or polarizable particle 22 located in the electric field, there is a net force on the particle along the separation direction between the electrodes towards the smaller electrode 18b. This is because in a non-uniform electric field, the particle is not polarized uniformly, and different parts of the particle are in fields of different field strengths.

[0066] Here, the particles are electrically polarizable particles and a pair of electrodes are driven with alternating potentials to create an alternating electric field, an effect known as the dielectrophoretic (DEP) effect.

[0067] In this effect, the electric field 20 polarizes the particles 22 so that the poles experience a force along the field lines, which can be either attractive or repulsive based on their orientation on the dipole. Since the electric field 20 is non-uniform and at this frequency the particles are polarized in phase with the RF field (positive DEP), the pole experiencing the greatest electric field will dominate the others and the particles will move in that direction. At other frequencies where negative DEP is present the particles will of course move in the opposite direction.

[0068] Bioparticles in a biofilm or other polarizable particles such as detergent particles may have a force applied to them and may therefore move (if they are free to move) under the influence of this dielectrophoretic force. However, if a single RF drive frequency is used, the force on the particles will always be in the same direction. If this direction is towards the teeth, for example, plaque will not be optimally removed.

[0069] Dental plaque usually consists of bacterial microcolonies embedded in an exopolysaccharide (EPS) matrix. Furthermore, dental biofilms or dental plaque are known to exhibit different viscosities, which make the biofilms difficult to remove. Therefore, there is a need to find a means to more efficiently degrade the formed biofilms and to aid mechanical biofilm removal.

[0070] The adhesive strength of plaque varies greatly from one area to another. In areas that are easy to reach with the bristles of a toothbrush, such as the buccal and lingual tooth surfaces, plaque is difficult to remove and the bristles must apply sufficient force to break down and erode the plaque layer. In the proximal and subgingival areas, such as the periodontal pockets, the plaque is soft but cannot be reached by the bristles, and thus these areas are not cleaned either. These so-called hard-to-reach areas therefore require the application of additional physical tools and principles to break down and displace the plaque.

[0071] The net dielectrophoretic force is known to change direction based on frequency. This is illustrated in FIG. 3, which shows the relationship between force in a given direction (Y-axis, arbitrary units) and logarithmic frequency (X-axis, Hz). For a typical biological cell-like particle, the switch occurs in the RF frequency band, for example around 1 MHz.

[0072] Reference is made to "Dielectrophoresis as a Tool to Characterize and Differentiate Isogenic Mutants of Escherichia coli" by M. Castellamau et al., Biophysical Journal Volume 91, Issue 10, 15 November 2006, Pages 3937-3945. This paper shows that for the bacteria studied there are in fact two crossovers of the direction of the dielectric force with frequency, which may also apply to biofilms with bacterial bodies. These crossovers are called transition frequencies and they are different for different particle types, e.g. different bacteria.

[0073] The present invention is based on the realization that these properties of dielectrophoretic forces can be utilized in oral care devices such as toothbrushes using RF electric field generation to improve particle movement or biofilm disruption for tooth cleaning or oral health promotion.

[0074] The present invention utilizes intermittent generation of an electric field at at least a first RF frequency. There can also be a combination of RF frequencies, which can optionally be additionally synchronized with the movement frequency and amplitude of the electric vibratory toothbrush head. One possible purpose is to facilitate the removal of plaque by breaking the bond between particles (cells or colonies) and EPS. Particles (cells or colonies) can additionally be moved from hard-to-reach areas such as periodontal pockets. The movement of cleaning agent particles can also be controlled.

[0075] The controller 10, for example, provides an alternating drive signal between the electrodes 18a, 18b in each pair of electrodes, which induces a (non-uniform) alternating electric field between each pair of electrodes. The RF field can be used to perform an oral irrigation function and / or it can be used to perform a particle movement inducing function.

[0076] The RF electric field may be used at any frequency within the range of, for example, 10 kHz to 100 MHz. A preferred frequency range may be 500 kHz to 30 MHz. RF electric fields at frequencies of the order of 1 MHz, for example 0.5 MHz to 1.5 MHz, have been found to be particularly effective for moving polarizable particles using the dielectrophoretic (DEP) effect.

[0077] FIG. 4 shows an exemplary device in the form of a mouthpiece in more detail than the schematic example of FIG.

[0078] The device again comprises a support 12 having a support surface 13, which is intended to be received in the oral cavity of a user. The support is coupled to a handle portion 34 which houses the controller 10. The handle portion in this example is shown with the optional additional feature of a local reservoir 32 for holding cleaning agent particles containing an active agent or substance to be delivered into the oral cavity, which is fluidly connected to the deployment surface of the device, for example via one or more fluid passages, to enable the particles to be received on the surface in use ready for delivery.

[0079] Additionally or alternatively, the device may be configured to releasably couple or dock with an external reservoir 36, such as a bottle or other receptacle. Once docked, particles can be loaded from the reservoir onto the support surface 13, ready to be delivered into the oral cavity.

[0080] In the example of Figure 4, the device has a first arcuate electrode 18a and a second arcuate electrode 18b, the electrodes being radially spaced apart from each other (along the radial dimension of the arcuate or semi-annular support). The first electrode 18a extends adjacent to the outer periphery of the body 12 and follows its contour. The second electrode 18b extends adjacent to and conforms to the inner periphery of the body 12.

[0081] The two electrodes are connected to a voltage source 11 and supplied with voltages of opposite polarity. An alternating voltage is used to generate the RF field.

[0082] 4 shows an alternative voltage source 11 and controller 10. For example, the controller controls the driving scheme of the voltage source. However, in other embodiments, the controller 10 may provide the voltage source. A pair of electrodes 18a, 18b in combination with the voltage source provide an electric field generator 16.

[0083] When the electrodes 18a, 18b are driven with an AC voltage supply to generate an RF electric field in a manner described in more detail below, the electrically polarizable particles 22 can be driven to move along the electric field gradient lines, for example towards the smaller, inner electrode 18b. The electric field gradient direction in this case is radial towards the second electrode and the gradient is uniform along the circumferential direction. As a result, a force is directed towards the second electrode. Alternatively, a force can be applied to electrostatic particles in the biofilm to be removed, which disrupts the biofilm.

[0084] Fig. 5 shows a further exemplary oral cleaning device 8. This embodiment may be the same in all respects as that of Fig. 4, except for the additional provision of radially projecting electrode nodes 21 on each of the first electrode 18a and second electrode 18b. The first electrode 18a has a first set of nodes 21a spaced apart along its length facing the second electrode 18b, and the second electrode 18b has a second set of nodes 21b spaced apart facing the first electrode. The first and second sets of nodes are circumferentially offset from each other, such that each node faces radially into a node-free space on the other opposing electrode.

[0085] This pattern results in a non-uniform electric field, but the field strength gradient directs the particles towards the location of the nodes 21 a, 21 b. The nodes thus allow different force directions to be defined, for example including a lateral component. Alternatively, more localized particle collection points can be defined across the support surface 13, allowing for directing the particles to more specific locations within the oral cavity in use.

[0086] Figure 6 shows a further exemplary oral irrigation device 8, which is again similar in all respects to the embodiment of Figures 4 and 5, except for the configuration of the first and second electrodes. In this embodiment, the first electrode 18a and the second electrode 18b are provided in the form of an arc-shaped comb electrode. The first electrode 18a and the second electrode 18b each have a set of protruding electrode fingers 19a, 19b. These effectively perform the same function as the node 21 of Figure 5, in that they provide a more spatially defined particle collection point. When the electrodes 18a, 18b are driven with an alternating drive signal to create an alternating electric field, a field strength gradient is directed towards the electrode fingers 19a, 19b.

[0087] Similar to the node of Figure 5, a first electrode 18a has a first set of fingers 19a spaced apart along the length of the electrode facing a second electrode 18b, and the second electrode 18b has a second set of spaced apart fingers 19b facing the first electrode. The first and second sets of electrode fingers are circumferentially offset from each other, with each finger facing radially into the open space on the other opposing electrode.

[0088] The advantage of the electrode fingers is that the electric field strength gradient is directed towards the distal (free) ends of the electrode fingers and the finger elements 19 can be made to any desired length (in the radial direction), thus allowing more flexibility in defining the force pattern (e.g. positions for particle collection).

[0089] 7 shows an oral care device 8 in the form of a toothbrush, showing an RF electric field generator 16 and its controller 10 for generating an input control signal "Control" for controlling the generation of the electric field by application to electrodes 18. The electric field exerts a force on the biofilm forming particles or detergent particles that are removed by the oral care device.

[0090] The oral care device of this example includes an electric toothbrush with a brush head 72 and a motor and drive train 74 for driving the brush head into vibration at an oscillating frequency. The controller 16 has suitable control electronics (such as a Schmitt trigger) to switch between at least two different frequencies or to apply a duty cycle to a single frequency. In either case, there is a periodic control signal to intermittently generate a field at a first frequency, which can additionally control the generation at one or more further frequencies.

[0091] In a first example, the controller 16 applies RF fields of two different frequencies on both sides of the above-mentioned DEP switching point, thereby adapting to a conventional RF driving method (single-frequency RF driving) and making more effective use of the DEP.

[0092] In this example, the RF electrodes are driven using two RF frequencies, one on each side of a threshold that is the transition point between the attractive and repulsive forces of the polarized or polarizable particles.

[0093] For example, the DEP drive shown in Figure 3 was described above as having a transition frequency of around 1 MHz. Suitable drive frequencies are 0.5 MHz and 5 MHz, or 100 kHz and 10 MHz, etc.

[0094] In addition to discrete frequencies, it is also possible to perform a frequency sweep between two extreme frequencies, where the extremes again straddle a switching frequency between positive and negative DEP.

[0095] Switching between frequencies can occur fairly quickly, such as once every few seconds, a few times per second, or even hundreds of times per second, and the frequencies can therefore be between 0.1 Hz and 1 kHz.

[0096] This reversal of force direction is particularly noticeable when applying a force directly to biofilm particles, such that the direction of the force on the bioparticles of an oral biofilm reverses at this switching frequency, thereby vibrating and loosening the particles more effectively than if the force was maintained in the same direction.

[0097] Plaque contains a mixture of bacteria of different sizes and characteristics, resulting in different transition frequencies between bacteria, as described above in "Dielectrophoresis as a Tool to Characterize and Differentiate Isogenic Mutants of Escherichia coli." When using the frequency sweep described above, there are many cases where, especially near the transition frequency of a particular bacterial species, one bacterium is attracted, while the next bacterium is repelled, causing the plaque to be locally separated.

[0098] In a second example, the controller 16 applies only one frequency of the RF field, but applies the field intermittently, and the frequency of the periodic control signal that provides this intermittent field generation is preferably tied to the brush vibration to better utilize the DEP.

[0099] Specifically, a single RF frequency may be used, but it is turned on and off in a cycle synchronized to the frequency (or a sub-harmonic of the frequency) of the brushhead's movement.

[0100] 8 shows a periodic control signal with a 50% duty cycle (one possible example, other duty cycles can be used), where one period corresponds to one vibration period of the vibrating brush head's motion. While the RF field is activated, there is a force on the polarizable particles (DEP force), and when the RF field is deactivated by the duty cycle, this force goes to zero.

[0101] In the case of a system that deploys cleaning particles, this can be used to control the movement of the particles. For example, as the brush vibrates, the RF field is displaced in space (following the movement of the brush due to electrodes attached to the brush head). As a result, the forces experienced by the particles (e.g. from the DEP) are effectively captured by the force and move with the movement of the brush head.

[0102] When the RF is on continuously, some vibration (in the direction of brush movement) occurs, but this does not result in a net movement of particles. However, with this intermittent drive scheme, particles may be captured and moved during parts of the duty cycle (when the brush head moves in one direction) and released during other parts (when the brush head moves in the opposite direction). As a result, particles may be moved repeatedly in the same direction, rather than being moved back and forth.

[0103] This situation is depicted in Figure 9. The DEP force from the RF field is shown as arrow 90 and the direction of movement is shown as arrow 92. Here, the DEP force is acting in the same direction as the brushing motion imparted by the vibration system. The bristles experience bending and sliding motions. Reaction and friction forces are represented, which are in the order of mN.

[0104] FIG. 10 shows a brush head 72 with a set of bristles 100 for moving particles in the manner depicted in FIG.

[0105] Due to the high vibration frequency (on the order of several hundred Hz), this results in very fast particle movement in one direction. This is effective in removing bacteria from the subgingival area, especially from deep periodontal pockets. Such pockets can be as deep as 5 mm, for example, and bacteria are often loosely attached or floating in the pocket fluid. In certain pocket cleaning embodiments, DEP forces can be used in synchrony with the brush sweep to draw bacterial cells out of the pocket.

[0106] Based on the position and orientation of the brush (eg, upper or lower jaw), the DEP force can be synchronized to alternate with a sweep down or a sweep up.

[0107] In a third example, the controller implements a drive scheme that switches between two RF frequencies or applies a frequency sweep (as described above for the first example), but is synchronized with the vibration frequency of the brush (as described above for the second example).

[0108] Thus, a known RF drive scheme is adapted in a manner that not only provides periodic control but also synchronization with the brush vibration to better utilize DEP. The drive switches between at least two RF frequencies to provide positive and negative DEP at the frequency (or sub-harmonics of the frequency) of the brush head movement.

[0109] This causes the DEP force on a particle to change from positive to negative at the moment the brush head changes direction of motion: if this is properly synchronized, the DEP force, and the force imparted to the trapped particle by the brush movement, are always in the direction of the brush head motion.

[0110] Figure 11 shows the necessary modifications to the system of Figure 7. The drive train current or voltage or amplitude signal is used as the synchronization and control signal 110 for the controller 10.

[0111] As explained above, the present invention is particularly concerned with the control of RF electric fields and the resulting forces which can be used to act directly on biofilm particles to disrupt the biofilm, or which can be used to control the delivery of detergent particles.

[0112] The cleaning particles may comprise oral cleaning or treatment agents, such as fluoride, whitening agents, mouthwash or antibacterial particles. The delivered agents may also include catalytic antibacterial robots (CARs) in polarizable carrier capsules. These utilize catalytic iron oxide nanoparticles to (i) generate bactericidal free radicals, (ii) degrade the exopolysaccharide (EPS) matrix of biofilms, and (iii) remove fragmented biofilm debris in a controlled manner via an electric field gradient-driven robotic assembly, preventing biofilm regrowth. Any other substance intended for cleaning or treatment of the oral cavity may also be envisaged.

[0113] To be effective, these agents need to be distributed evenly across the areas of the oral cavity where they are needed. For example, whitening agents need to be spread evenly across the tooth surface, and antimicrobial particles need to be spread evenly across the gum area. However, delivering agents to the required areas of the oral cavity is difficult and inefficient, reducing efficacy and causing inconvenience to the user.

[0114] Thus, the electric field can additionally be used to manipulate the distribution of particles, including oral therapeutic agents, within the oral cavity.

[0115] The particles manipulated by the electric field may themselves be particles of an oral therapeutic agent, or may be carrier particles that contain the therapeutic agent therein to be deployed. For example, the particles may be capsules that contain the therapeutic agent therein. The force induced on the particles by the electric field may induce the particles to move. For example, the particles may be induced to move, in some cases, along or across the surface 13 of the support 12, thereby delivering the particles to the required location in the oral cavity.

[0116] The present invention may be used in systems that use RF for controlled delivery of detergent particles, or alternatively, in systems that use RF fields to apply forces directly to particles of a biofilm.

[0117] In a system that provides for both delivery of detergent particles using an RF electric field and application of a force to the biofilm itself using an RF electric field, the controller may be selectively controllable between at least two different modes, the modes including: a particle delivery mode in which the controller provides a control signal to the electric field generator to generate an electric field to direct particles sensitive to the electric field to a desired location in space; and a cleaning mode in which the controller provides the intermittent control signal to the electric field generator to generate an RF electric field in the space to perform an oral cleaning function, which may be performed simultaneously with a vibration brushing function.

[0118] The device may be configured with a function to trigger the activation of the delivered particles. This activation may be a chemical or physical reaction process, or a process of breaking the particles to release their contents. This step may be performed, for example, after moving the particles to a desired location in the oral cavity. Thus, the device may further include a particle activation device configured to generate a physical stimulus to stimulate an activation event of the drug particles. The particle activation device may be composed of the same or different elements as the electric field generator. Thus, the particle activation device may in some examples be provided by the electric field generator or may be formed by a separate set of one or more elements.

[0119] The stimuli may include, by way of non-limiting examples, at least one of a generated electric field (electrical and / or magnetic stimulation), a thermal stimulation, and an acoustic stimulation.

[0120] Examples of tooth brushing mouthpieces and electric toothbrushes have been given above, however the present invention can also be applied to other oral hygiene devices such as irrigators or flossing devices.

[0121] As described above, the embodiments utilize a controller. The controller can be implemented in various ways using software and / or hardware to perform the various functions required. The processor is one example of a controller employing one or more microprocessors that can be programmed using software (e.g., microcode) to perform the functions required. The controller may or may not employ a processor, and may be implemented as a combination of dedicated hardware to perform some functions and a processor (e.g., one or more programmed microprocessors and associated circuitry) to perform other functions.

[0122] Examples of controller elements that may be employed in various embodiments of the present application include, but are not limited to, conventional microprocessors, application specific integrated circuits (ASICs), and field programmable gate arrays (FPGAs).

[0123] In various implementations, a processor or controller may be associated with one or more storage media, such as volatile and non-volatile computer memories, such as RAM, PROM, EPROM, and EEPROM. The storage media may be encoded with one or more programs that, when executed by the one or more processors and / or controllers, perform the required functions. The various storage media may be fixed within a processor or controller, or may be transportable such that one or more programs stored thereon can be loaded into a processor or controller.

[0124] Variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the figures, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other steps or elements, and the indefinite article "a" or "an" does not exclude a plurality.

[0125] The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

[0126] The computer program may be stored / distributed on a suitable medium, such as an optical storage medium or a solid-state medium, supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless communication systems.

[0127] Please note that when the term "adapted for" is used in the claims or specification, the term "adapted for" is intended to be equivalent to the term "configured for."

[0128] Any reference signs in the claims should not be construed as limiting the scope of the invention.

Claims

1. An oral care device comprising: an electric field generator that generates an electric field in the oral cavity of a user based on an input control signal; a controller generating the input control signal and controlling generation of the electric field, the electric field being for applying a force to biofilm forming particles or cleaning agent particles to be removed by the oral care device; the controller generating periodic control signals to alternately generate electric fields at a first RF frequency and a second RF frequency; The oral care device, wherein the periodic control signal is for generating a frequency switch between the first RF frequency and the second RF frequency, or for generating a frequency sweep between the first RF frequency and the second RF frequency.

2. 10. The oral care device of claim 1, wherein the first RF frequency is below a threshold frequency and the second RF frequency is above the threshold frequency to generate an opposing dielectrophoretic force on particles.

3. The oral care device of claim 2 , wherein the threshold frequency is 1 MHz.

4. An oral care device according to any one of claims 1 to 3, wherein the frequency of the periodic control signal is in the range of 0.1 Hz to 1 kHz.

5. The brush head and The oral care device of claim 1 , further comprising a motor for vibrating the brush head at a vibration frequency.

6. The oral care device of claim 5 , wherein the frequency of the periodic control signal is equal to the vibration frequency or a subharmonic of the vibration frequency.

7. The oral care device of claim 6, wherein the vibration frequency is in the range of 50 Hz to 1 kHz.

8. 8. The oral care device of claim 5, 6 or 7, wherein the electric field generator is coupled to the brush head for movement therewith.

9. 9. The oral care device of claim 1, wherein the electric field generator generates a non-uniform electric field having a field strength gradient in one or more directions, and a force is generated along the direction of the gradient.

10. 10. The oral care device of claim 1, wherein the electric field generator comprises one or more conductive elements electrically coupled to the controller, and the control signal is an electrical drive signal for charging the one or more conductive elements.

11. A computer program executable on a processor or computer, when the processor or computer is operatively coupled to an electric field generator of the oral care device of claim 1, the program causing the processor to execute a method of controlling the oral care device, the method comprising: generating a control signal to control generation of an electric field in the oral cavity of a user, the electric field being for applying a force to biofilm forming particles or cleaning particles to be removed by the oral care device; the control signal includes a periodic control signal for generating an electric field alternately at a first RF frequency and a second RF frequency; the periodic control signal is for generating a frequency switching between the first RF frequency and the second RF frequency or for generating a frequency sweep between the first RF frequency and the second RF frequency.

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