WO1994003123A1

WO1994003123A1 - Power-driven rotary toothbrush

Info

Publication number: WO1994003123A1
Application number: PCT/IT1992/000092
Authority: WO
Inventors: Vincenzo De Cicco
Original assignee: Vincenzo De Cicco
Priority date: 1992-08-04
Filing date: 1992-08-04
Publication date: 1994-02-17
Also published as: AU2441692A

Abstract

A power-driven rotary toothbrush comprising a hollow handle (1), a reversible motor housed within the handle (1) and carrying a shaft substantially coaxial therewith, a three-positions switch (4) accessible from the exterior of the handle (1) for actuating the motor in either one of the two possible directions, an electrical power source connected to the said reversible motor, a substantially cylindrical exchangeable brush (2) with a plurality of radially extending bristle tufts (8), and an elongated protective shield (3) detachably connected to the handle (1) and extending parallel to the cylindrical brush (2) so as to cover part of the outer surface thereof, wherein the bristle tufts (8) are arranged in two or more spirals wound around a bristle-carrying cylindrical core (7), and wherein the protective shield (3) comprises a terminal L-shaped portion (10) which detachably engages the tip (9) of the cylindrical brush (2) while allowing the free rotation thereof.

Description

POWER-DRIVEN ROTARY TOOTHBRUSH

The present invention relates to a power-driven rotary toothbrush. Specifically, the invention concerns an electrically motor-driven toothbrush, whose bristle-carrying head is provided with radially extending bristles, and is made to rotate about its longitudinal axis either clockwise or counter-clockwise by operation of a switch. It is well-known that, in order to maintain a proper oral hygiene, the outer surfaces of teeth should be cleaned by brushing them exclusively from the gum margins towards the dental crown. As a matter of fact, it is extremely important to remove the bacterial plaque from the surfaces at and below the free gingival groove, and from the tooth-gum interfaces, where the said plaque naturally tends to hide.

Cleaning the teeth with a proper brushing movement is particularly difficult, when employing a conventional toothbrush, especially at those places in the oral cavity where there is no easy access.

In some of the lately developed power-driven toothbrushes this problem is dealt with by providing a rotary brushing head that, instead of vibrating or oscillating, rotates about its longitudinal axis, and is provided with radial bristles.

The reversible motor provided within the hollow handle of one such toothbrush is actuated by a three-positions switch, and may drive the brushing head in either one of the two directions. Thus, the user may choose the correct direction of operation in order to obtain a brushing movement of the bristles always from the

5 gingival groove area towards the crown area.

A number of patent documents disclose motor-driven rotary toothbrushes, among which, e.g., Italian utility models No. 181183 and No. 198470. The first one of the -said documents concerns a rotary ₀ toothbrush comprising a reversible motor powered by a battery, both these elements being housed in the cylindrical plastic handle of the toothbrush, and a rotatable brush coaxially coupled with the motor shaft. Said brush is simply said to be a cylindrical brush ₅ with radial bristles, and no further details are given about the arrangement of the bristles on the bristle-carrying head.

The second one of said documents discloses a rotary toothbrush very similar to the previous one but _Q equipped, additionally, with^" a curved protective shield, connected to the toothbrush body and extending parallel to the brush axis, so as to cover part of the outer surface thereof. The said shield is designed to prevent the inner surface of the cheek from coming into contact with the rotating brush.

Neither this document discloses the actual arrangement of the bristles on the brush head, as it simply teaches a substantially cylindrical brush. As a characterizing feature, the said brush has parallel rows of bristles projecting off its shape, transversal to the brush axis and spaced apart from each other so as to correspond to the interdental spaces. Italian utility models No. 196488 and No. 204773 disclose two electrically powered rotary toothbrushes quite similar to the above ones, both provided with a protective shield for the inner surface of the cheek, in which the bristles are arranged in a plurality of discrete tufts, embedded in a cylindrical carrier core and aligned on straight lines parallel to the rotation axis.*

The same teaching may be drawn, as concerns the arrangement of the bristle tufts, from EP-A-0 254 460. The latter discloses a motor-powered rotary toothbrush in which the only feature substantially different from the previous ones appears to be in the arcuate protective shield being rotatably mounted on the toothbrush stem, instead of being fixedly connected to the body of the device. The said shield is held stationary by contact with the mouth or tongue while the brush rotates. The radial bristle bundles are embedded in the cylindrical carrier and are aligned on straight lines parallel to the axis thereof. Such an arrangement of the bristles results in an unpleasant vibration of the toothbrush when applied to the user's denture, as rows of bristle bundles alter¬ nate with empty spaces while the device rotates in contact with the teeth surfaces. Moreover, the brushing action is not continuous, and the bacterial plaque and food residues are not pushed away from the gingival groove in a continuous manner. These drawbacks can be only partially reduced by increasing the number of parallel rows of bristle tufts around the carrier core, as it is evident that increasing such number would require an unacceptable increase of the core diameter. As an alternative to the above bristle-carrying heads swab-like heads have been used, of the same kind as those, much thinner and manually operated, convent¬ ionally employed for cleaning the interdental spaces. Examples of the latter are disclosed in EP-A-0326677 and in EP-A-0361120. In such devices the bristle carrier is a twisted wire loop wherein the bristles are trapped, at a central position thereof, between the turns of two inter-t¬ wisted wire sections. As a consequence, the bristles are uniformly arranged along a spiral winding. Although they overcome the above-mentioned drawbacks, the rotary toothbrushes with swab-like head are quite delicate, as they are easily damaged and quickly worn out when employed for the every-day care of the dentu¬ re. The wire loop is readily deformed, especially in view of the fact that the bristle-carrying head is repeatedly exchanged with other fittings, such as, e.g., some rotary interdental cleaning devices. Moreo¬ ver, the arrangement of the bristles in a continuous winding, as opposed to bristle bundles, results in a higher weakness of the bristles and in their being prone to break. Accordingly, the object of the present invention is to provide an electrically driven rotary toothbrush with a bristle-carrying head that overcomes the drawbacks mentioned above while allowing to maintain a proper oral hygiene, and having a reasonable cost of manufac¬ ture. To that aim, there is proposed to modify the rotary toothbrushes with aligned bristle tufts of the prior art by displacing the said tufts along a plurality of helical lines winding around the central cylindrical core of the bristle-carrying head. In order to prevent any bending or deformation of the bristle-carrying head in use while maintaining a stable spacing between the said head and the protective shield for the inner surface of the cheek, the said shield is rigidly secured to the toothbrush body at its base, while its distal end engages with the tip of the bristle-carrying head.

Accordingly, the present invention specifically provi¬ des a power-driven rotary toothbrush comprising an at least partially hollow handle, a reversible motor housed within said handle and carrying a shaft subst¬ antially coaxial with said handle, a three-positions switch accessible from the exterior of said handle for actuating the said motor in either one of the two possible directions, an electrical power source conne¬ cted to the said reversible motor, a substantially cylindrical exchangeable brush with a plurality of radially extending bristle tufts, said brush being detachably coupled to said shaft, and an elongated protective shield detachably connected to the said handle and extending parallel to the said brush so as to cover part of the outer surface thereof, charact¬ erized in that the said bristle tufts are arranged in two or more spirals wound around a bristle-carrying cylindrical core, and in that said protective shield comprises a terminal L-shaped portion which detachably engages the tip of the said brush while allowing the free rotation thereof.

Further preferred features of the toothbrush according to the invention are recited in the appended dependent claims.

The said features, as well -as the advantages of the invention, will become more apparent when reference is made to the accompanying drawings, in which: Figure 1 is a perspective view of a toothbrush embod¬ ying a preferred solution of the present invention; Figure 2 is a perspective view of a first additional bristle-carrying head for use in alternative to the head of the invention; and

Figure 3 is a perspective view of a second additional bristle-carrying head for use as an alternative to the head of the invention. As shown in Figure 1, the rotary toothbrush according to the invention includes a main body in the form of a handle (1) , a cylindrical brush (2) and a protective shield (3) for preventing the bristles of the brush (2) from coming into contact, in use, with the inner surface of the cheek.

The handle (1) is hollow and houses therein a reversi¬ ble direct current motor (not shown) , equipped with speed-reduction gear and pole reverser. The motor is actuated by means of a three-positions switch (4) accessible from the outside of the handle (1) , in either one of the two directions of rotation, as shown by the arrows marked on the handle shell. The handle (1) also houses a rechargeable battery (not shown) , as a power source for the motor, and carries at its bottom a plug for connection with the electrical power supply via a transformer. The led (5) in the handle (1) shows when the battery needs to be recharg¬ ed. The motor shaft is substantially coaxial with the handle (1) , and projects off the top of the handle (1) for being coupled with the cylindrical brush (2) at a location corresponding to the tapered section (6) thereof. The latter is prolonged in the bristle- carrying cylindrical core (7) , whose diameter is preferably 4 mm. The tapered section (6) and the bristlecarrying cylindrical core (7) are made of an integral plastic piece, in which the bristle tufts (8) are embedded.

The cylindrical core (7) ends in a pin (9) for engag¬ ement with a guiding hole provided in the terminal section (10) of the shield (3) . The latter is releasa- bly connected to the handle (1) at its base. As it may be understood from Figure 1, the bristle tufts (8) are arranged on four spirals wound around the cylindrical core (7) ; for an optimal performance of the toothbrush, the free length of the bristles is about 5 mm, their thickness is about 0.06 mm and the rotation speed is about 250 r.p.m.

Figure 2 shows a εwab-like brush (11) of the kind conventionally employed in the prior art, which is proposed as an additional fitting for the rotary toothbrush of the invention. The brush (11) comprises a plastic body with a tapered section (12) for connection with the handle (1), and a cylindrical section (13), in which the ends of the twisted wire (14) are embedded. The bristles (15) are trapped between the windings of the wire (14) , in the bristle-carrying portion of the brush (11) .

In order to allow the insertion and the free rotation of the brush (11) , in place of the brush (2) of Figure 1, a terminal portion of 3 mm length of the brush (11) is bristle-less, and a plastic or rubber cap (16) is provided on top of the brush (11) . The cap (16) , which could be provided, if necessary, also for use with the - -

brush (2) according to the invention, serves to help the brush in maintaining a perfect axial asset while rotating, in cooperation with the L-shaped section (10) of the shield (3) . For an optimal performance, the diameter of the wire (14) should be about 0.67 mm, and the bristles (15) should be about 10 mm long and 0.15-0.17 mm thick. It has been shown by several tests that the brush (11) of Figure 2 may be advantageously employed instead of the brush according to the invention in cases where the gums are particularly inflamed and painful, as its action is more gentle than that of the brush of the invention. When the mucous membrane of the gum is reddened and swollen, owing, e.g., to periodontosis, it is advisable to employ the εwab-like brush of Figure 2 until the general conditions of the oral mucous membr¬ anes show a visible improvement, and then, after some days, turn to the brush (2) of the invention, for the ordinary maintenance. Figure 3 shows a thin εwab-like brush (17) of the kind conventionally employed in the prior art for cleaning the interdental spaces, comprising a plastic body with a tapered section (18) and a cylindrical section (19) , both identical to those of the brush shown in Figure 2. The twisted wire (20) is preferably of 0.35 mm diame¬ ter, and the bristles (21) are preferably 3 mm long and 0.4 mm thick. The brush of Figure 3 could be advantageously included in a kit for oral hygiene, together with the brush (2) of this invention and with the brush (11) of Figure 2. Differently from the previous two, the brush of Figure 3 is used without the shield (3) , in order to be introduced between the interproximal surfaces of the teeth for cleaning the interdental spaceε. Another proposed use for this brush is for the maintenance of orthodontic brackets. Indeed, it is well-known that keeping the oral cavity clean when carrying an ortho¬ dontic device is practically impossible with the conventional toothbrushes, as the bacterial plaque is left undisturbed all around the contact area between tooth and bracket.

The effectiveness of the rotary toothbrush according to the invention has been investigated by means of several tests, some of which are reported below. A first subject examined did not show any particular pathology but an unpleasant cold feeling at the neck of the 7th lower right tooth. The free gingival margin was not inflamed, and the periodontal probe did not pene¬ trate more than 1.5 mm. Therefore, the sensitivity at the collet was to ascribe to an improper use of the conventional toothbrush in view of the remote location of the concerned tooth. After 5 days of use, 3 times a day, of the toothbrush according to the invention, the sensitivity had completely disappeared, and after 12 days the gingival margin had migrated towards the - -

crown, thus covering that zone of the collet which was responsible for the said sensitivity.

Another patient, aged thirtyfive, had problems with the gum margin in all sections of his mouth, owing to an incorrect oral hygiene. The interdental papillae were ipertrophic, and showed edema and bleeding; the peri¬ odontal probe penetrated for 3-4 mm at all locations and the central lower right incisive showed a V-shaped gingival recession of about 4 mm in the apical dire¬ ction and 3.5 mm in the mesio-distal direction. After 2 days of treatment with the toothbrush according to the invention the gums bleeded only upon the action of the probe, the gum margin was less inflated and less reddened, and the bacterial plaque was completely absent, as shown by employing the plaque detecting solution. After 7 dayε the normal conditions were completely restored, and the periodontal probe pene¬ trated for not more than 2.5 mm. After 15 days of treatment the V-shaped retraction of the gum margin was reduced to one half, both in the mesial and in the apical direction; the collet zone was sensitive only to strong thermal shocks.

The above test shows that when the bacterial plaque is prevented from resting in the gingival groove there not only is a reconstitution of the tooth-gum interfacial epithelium but also of the connective collagen fibres, which thus reform the physiological barrier which blocks the access to toxic substances to the zone below the gum margins.

A further case concerned a patient aged twentyfive, who had been implanted, 16 months before, a porcelain crown on the 4th upper right tooth. The patient showed a retraction of 1 mm of the free gingival groove, which resulted in exposure of the crown edge, with obvious aesthetic and hygienic problems. The periodontal probe did not penetrate more than 1 mm, and the mucous membranes were not inflamed. The only possible reason for the observed retraction was an improper use of the toothbrush. After 15 days of everyday use of the toothbrush according to the invention the gingival margin had migrated well beyond the crown edge, and the oral cavity had recovered the normal physiological conditions.

The particular arrangement of the bristle tufts brings about not only a perfect hygiene of the dental crown but also a deep cleaning of the gingival groove, also because any simple tuft of bristles acts on the mouth εurface by both a rotational and a translational movement. Considering a single tuft in rotation about the toothbrush axis, three cleaning phases may be evidenced, namely a first translational phase in which the tuft approaches the gums and crown at an acute angle with respect to the teeth surface, a second rotational phase in which the tuft passes by the position at 90° to the tooth surface, and a third translational phase in which the tuft slides on the crown surface again at an acute angle thereto. Thanks to the displacement of the bristle tufts on a plurality of spiral lines, as opposed to straight lines parallel to the rotation axis, the toothbrush according to the invention completely removes the bacterial plaque from both the teeth surfaces and the gingival groove, thus promoting a quick recovery of any path¬ ologic conditions affecting the free gingival groove and the junctional epithelium.

Claims

1. A power-driven rotary toothbrush comprising an at least partially hollow handle (1) , a reversible motor housed within said handle (1) and carrying a shaft substantially coaxial with said handle (1), a three-positions switch (4) accessible from the exterior of said handle (1) for actuating the said motor in either one of the two possible directions, an electrical power source connected to the said reversible motor, a substantially cylindrical exchangeable brush (2) with a plurality of radially extending bristle tufts (8), the said brush (2) being detachably coupled to the said shaft, and an elongated protective shield (3) detachably connected to the said handle (1) and extending parallel to the said brush (2) so as to cover part of the outer surface thereof, characterized in that the said bristle tufts (8) are arranged in two or more spirals wound around a bristle-carrying cylindrical core (7) , and in that said protective shield (3) comprises a terminal L-shaped portion (10) which detachably engages the tip (9) of the said brush (2) while allowing the free rotation thereof.

2. A power-driven rotary toothbrush according to claim 1, wherein the said cylindrical core (7) is made of plastic and the said bristle tufts (8) are embedded therein.

3. A power-driven rotary toothbrush according to claims 1 or 2, wherein the said spirals are from four to six.

4. A power-driven rotary toothbrush according to any one of claims 1 to 3, having a rotation speed of from 220 to 280 r.p. ..

5. A power-driven rotary toothbrush according to claim 4, having a rotation speed of 250 r.p.m..

6. A power-driven rotary toothbrush according to any one of claims 1 to 3, wherein the said cylindrical core

(7) has a diameter of from 3 to 5 mm.

7. A power-driven rotary toothbrush according to claim 6, wherein the free length of the bristles of said bristle tufts (8) is of from 4 to 7 mm.

8. A power-driven rotary toothbrush according to claim 6, wherein the thickness of the bristles of said bristle tufts (8) is of from 0.06 to 0.25 mm.

9. A power-driven rotary toothbrush according to any one of claims l to 8, wherein the said terminal L-shaped portion (10) is provided with a hole for engaging the said tip (9) .

10. A power-driven rotary toothbrush according to claim 9, wherein the said tip (9) is a cylindrical pin integral with the said cylindrical brush (2) and coaxial thereto.

11. A power-driven rotary toothbrush according to claim 9, wherein the said tip (9) is provided with a removable cylindrical cap (16) for engagement with the said hole.