A LIGHT- ACTIVATED DENTIFRICE AND ASSOCIATED LIGHT IRRADIATING TOOTHBRUSH

This invention relates generally to dentifrices and more specifically concerns a light- activated dentifrice for killing oral bacteria and the combination of such a dentifrice with a light irradiating toothbrush.

The use of photocatalyst material activated by ultraviolet light for killing of bacteria, including oral bacteria, is well known. Titanium Oxide (TiO ₂ ) is one example of such a material. However, the use of ultraviolet (UV) light inside the mouth is seriously restricted due to safety concerns. Accordingly, it is desirable to have a light-activated dentifrice which is capable of killing bacteria but which can be activated by light in the visible spectrum which is safe for use in the mouth of a human user.

An oral care combination is disclosed which comprises: a treatment device having a source of light in the visible spectrum, safe for use in the mouth, and capable of activating photocatalysts to kill oral bacteria; and a dentifrice for use with the treatment device, comprising as one ingredient thereof photoactive particles comprising a core substantially of titanium nitride (TiN) and a shell of titanium oxide (TiO ₂ ), wherein the relative amounts of TiN and TiO ₂ in the active particles are such that the light activates the TiO ₂ to the extent that substantially more than 50% of the oral bacteria coming into contact with the dentifrice and exposed to the light for a selected time are killed.

A dentifrice is disclosed which comprises: a mixture comprising a liquid medium and a powder comprising particles having a core of titanium nitride (TiN) and an outer shell of titanium oxide (TiO ₂ ), the particles responding to light in the visible spectrum to kill oral bacteria when the mixture is used in the mouth.

A method is disclosed for making a powder for use in a dentifrice for killing oral bacterial irradiated by light in the visible spectrum, longer in wavelength than ultraviolet light, comprising the steps of: oxidizing a particle of original TiN material sufficiently to produce an end particle comprising a core of TiN and a shell of

TiO ₂ , wherein the relative amounts of TiN and TiO ₂ in the end particle are such that oral bacteria are killed when exposed to a dentifrice which includes said end particles and irradiated by said light.

Figure 1 is an elevational view of a treatment device/toothbrush capable of emitting visible light in combination with a particular dentifrice in a conventional dentifrice tube.

Figure 2 is an elevational view showing a treatment device/toothbrush arrangement capable of emitting visible light for activating a particular dentifrice which is stored in the device/toothbrush itself.

Figure 3 is a diagram illustrating the effectiveness of two dentifrice embodiments in killing oral bacteria.

Figure 4 is a top plan view of a portion of a mouthguard using the particular dentifrice and visible light sources.

Figure 5 is a diagram of a particle used in the dentifrice.

Titanium Oxide (TiO ₂ ) is known to function as a photocatalyst under ultraviolet light (UV). Under UV irradiation, it acts as a strong oxidant and can oxidize organic material directly. Further, as TiO ₂ is exposed to UV light, it becomes increasingly hydrophilic and can be used in a number of general cleaning applications, as well as for killing bacteria, including oral bacteria. Hence, TiO ₂ could be used as a component in oral care compositions such as toothpaste, mouthwash and whitening coatings for teeth. However, the actual use of TiO ₂ in oral care is extremely limited, because, as noted above, it requires the use of ultraviolet light, which is subject to safety concerns, including the possibility of inducing oral cancers with extended use. Heretofore, visible light, which is safe for use in the mouth, could not be used to activate TiO ₂ .

In the present embodiment, a dentifrice powder is used for oral care applications which comprises particles 13 which have a titanium nitride (TiN) core 15 and a TiO ₂ shell 17 around the TiN core. Such a particle can be readily produced by partially oxidizing a TiN particle to produce an outer shell of TiO ₂ around a remaining inner core of TiN. A number of different TiN core/TiO ₂ shell arrangements have been discovered to be useful and safe in oral care applications as set forth below. In one embodiment, the individual particles comprise 4% TiN and 96% TiO ₂ by weight. The particles of this embodiment absorb light having wavelengths less than 550nm, which is higher than the wavelength of ultraviolet light, which is less than 400nm.

The particles of another embodiment comprise 84% TiN and 16% TiO ₂ which absorb visible light having wavelengths less than 850nm. Both of the above particles, but especially the higher TiN content embodiment, absorb a wide range of visible light having wavelengths greater than 400nm. Both of the above powder particles, when used in a dentifrice, have been shown to be effective in killing bacteria when irradiated with visible light at the wavelengths noted above. In one dentifrice arrangement, the powder particles are used in a water suspension with a powder concentration of 5-100mg/l. Different powder mixtures can, however, be used. Applying the dentifrice to biofilms on teeth containing bacteria and then exposing the dentifrice to light in a safe wavelength spectrum produces results shown in Figure 3, in which the powder embodiment (line 30) comprising 96% TiO ₂ results in close to 90% of the bacteria being killed using 190 j/cm ² of light exposure (dose), while the 16% TiO ₂ powder (line 32) killed close to 100% of the bacteria at the same light exposure. Figure 3 also shows that a 100% TiO ₂ powder only produced a 40% killing level, which is about the level of killing produced by the light alone. The data shows the effectiveness of a dentifrice powder/water mixture using a TiN core/TiO ₂ shell arrangement in killing oral bacteria.

Figure 1 shows an oral treatment device 10. Treatment device 10 includes a light source 12 which can be located in a head portion 14, or in a handle portion 16. In the handle embodiment, light proceeds through a light pipe to and then out from head portion 14. On-off button 24 controls the operation of light source 12. Treatment device 10 can include bristles 18 for scrubbing of the teeth, if desired. Bristles, however, are not necessary for effective operation of the treatment device. Device 10 can be a manual toothbrush, or it could be a power toothbrush which provides a desired motion to the toothbrush head portion, including, for instance, lateral

(side-to-side) motion, longitudinal motion or more complex movements. Motor/drivers 23 to produce such various motions are well known and are thus not disclosed in detail herein. One such arrangement is shown in U.S. Patent No. 5,378,153, owned by the assignee of the present invention. Motion actuation is controlled by a separate button 25.

In the embodiment of Figure 1, dentifrice 21, which includes the desired TiNVTiO ₂ particles, is applied to the teeth by a user from a separate storage member, such as a dentifrice tube 20. Light source 12 in one embodiment shown is an LED powered by a battery 22. The light source 12 is controlled by user-operated on-off switch 24. In one example, the wavelength of the LED is between 400-500nm. Dental LEDs are presently available in wavelengths in that range. Furthermore, the existing dental LEDs have been designed for power outputs of up to lW/cm ² , which is sufficient to provide the desired activation for the TiNVTiO ₂ particles.

In operation, the user applies a desired amount of dentifrice to a section of teeth. The user can use the brush to scrub the teeth, if desired. The light source is then actuated by operation of switch 24. The light irradiates the dentifrice to kill the oral bacteria. The visible light produced by the light source is advantageously absorbed by the TiN core and then transferred to the TiO ₂ shell, activating the TiO ₂ material, which produces the desired killing effect on the oral bacteria. The present particle arrangement results in the TiO ₂ being activated by the use of visible light. Since the light is in the visible spectrum, using dental approved LEDs, no harm is done to the user.

Figure 2 shows another treatment device embodiment 30, in which a source of dentifrice 32 is contained within handle 34 of the device. By means of a pump 36 or similar member, the dentifrice is directed to the teeth through openings 38 in the head portion 40 of the treatment device. The embodiment of Figure 2 can use light activation alone, or bristles could be provided on the head portion for scrubbing of the teeth, with the toothbrush being manually or power operated. The light source is actuated by on-off button switch 42. Motion can be provided to the head portion 40 by a motor/driver 44, controlled by a button witch 46.

In operation of the embodiments of Figures 1 and 2, the time of light exposure to produce the desired killing rates could be 2 seconds per tooth, and several minutes, up to 10 or even 15 minutes, for the whole mouth, although 2-5 minutes would be more typical. Although Figures 1 and 2 show hand-held treatment device embodiments, another useful embodiment could be in the form of a fully illuminating mouthguard, which treats all of the teeth at the same time. The dentifrice composition

with the TiNVTiO ₂ particles could be positioned in the mouthguard before use. This embodiment is illustrated in Figure 4, which shows a mouthguard portion 50, i.e. a lower half of a full mouthguard, with a light source 52 and an on-off control button 54. The light source 54 is connected via a light pipe or similar element 56 to a plurality of light outlets 58-58 in the body of the mouthguard. With the mouthguard embodiment, the entire mouth could be treated in a very short time, e.g. 2 minutes or less, depending on the arrangement of light sources in the mouthguard. The light source could also be located away from the mouthguard itself, with the light proceeding through a flexible light tube to the mouthguard. Although a preferred embodiment of the invention has been disclosed here for the purposes of illustration, it should be understood that various changes, modifications and substitutions may be incorporated in the embodiment without departing from the spirit of the invention, which is defined by the claims which follow.