Background of the invention Tooth picks or dental sticks are well known in the art and have been used for cleaning teeth for centuries. The basic tooth pick is a wooden stick which is small enough to penetrate between the teeth and remove bits of food from meals etc. Normally, this kind of tooth pick is a straight piece with a pointed end or ends.

The problems with this basic tooth pick are many. The pick will very easily lose its rigidity and become frayed or even break between the teeth. Wood also limits the possibility of forming the pick into more advanced shapes without increasing the production costs beyond the acceptable limit.

A modernized dental stick is described in US-A 3,101,727.

The stick is made of plastic and has a holding portion, a flexible straight-pointed end and a flexible hook-like end. Because of the shape and the flexibility, the stick can reach almost any portion or side of the teeth. To further improve the function of the stick, it has a surface with different kind of patterns which makes it able massage the gums.

A problem with this know dental stick is the lack of rigidity which weakens the stick's ability to penetrate between teeth in close proximity. The stick's ability to

remove coatings or tartar from the teeth is also rather poor because of the lack of rigidity at the end portions.

Summary of the invention When, as stated in claim 1, said at least one end portion has means for strengthening the rigidity of said at least one end, and where said strengthening means projects outwardly from the central portion toward the end of the at least one end portion, it is possible to obtain a tooth cleaning device with the necessary rigidity to rinse teeth for bits of food.

It is understood that the tooth cleaning device can comprise one central portion and only one real end portion. The other end portion will then only be a short termination of the central portion.

When, as stated in claim 2, said at least one end portion has means for strengthening the rigidity of said at least one end, where said strengthening means projects outwardly from the central portion toward the end of the at least one end portion, and said cleaning device has an uneven surface, it is also possible to remove coatings or tartar from the teeth in a preferable manner while also massaging the gums. To control the rinsing and massage process it is very important that the user has a firm grip on the tooth cleaning device which is ensured by an uneven surface on the holding portion. Combined with the rigidity of the end portion or portions, this results in a tooth cleaning device that may be used with precision against given point while also preventing damage to teeth or gums.

At the same time, the tooth cleaning device will be easy and cheep to manufacture due to the entire surface being uneven.

When, as stated in claim 3, at least one of the end portions has a pointing shape, it is easier to clean between teeth in close proximity and in areas difficult to access in the mouth in general. This is due to the fact that the triangular shape combined with a thin cross section and the strengthening means provide a pointy but rigid tooth cleaning device.

When, as stated in claim 4, the strengthening means is an elevated central portion on at least one side of said at least one end portion, it is possible to obtain the necessary rigidity of the end portion or portions. At the same time, the manufacture of the tooth cleaning device with the strengthening means does not complicate the manufacturing process and the production costs can hereby be kept low.

When, as stated in claim 5, each of the strengthening means has a V shape along a central line from the central portion to the end of said end portion, it is possible to provide the tooth cleaning device with improved rigidity properties, especially in the transverse direction of the central line.

When, as stated in claim 6, the strengthening means has a triangular shape, the ratio between strength and size of the strengthening means is optimised.

When, as stated in claim 7, the end portion has a V shape along said central line, it is possible to increase the strength of the end portion in more than one direction, especially when combined with another strengthening means, such as e. g. the elevated central portion on one side of the end portion. The strength will be increased in the direction of the end and in the cross direction.

When, as stated in claim 8, the cross section of said cleaning device has an end pointing in one direction, the ability to penetrate between teeth is increased and especially when applied in a downwards or upwards motion.

When, as stated in claim 9, one end portion has a non- linear shape along said central line, it is possible to create hook-like shapes or the like. The combination of the rigidity and the uneven surface with an end portion of non-linear shape is particular advantageous, since the operation of reaching and cleaning the portions of the mouth which are difficult to access, require a precise, rigid instrument and a firm grip.

When, as stated in claim 10, said cleaning device has two end portions, each having a mainly rectilinear shape along said central line, a very simple version of the invention is obtained. This makes the tooth cleaning device particularly inexpensive to manufacture.

When, as stated in claim 11, said cleaning device is made of a plastic material, it is possible to manufacture a particularly inexpensive version and exploit the advantages of plastic in general which are known by a skilled person within the art. Other materials can be

used instead of plastic such as different kinds of metal and pressed cellulose fibres, but with a less successful result.

The drawing The invention will be described below with reference to the drawings in which fig. 1 illustrates a tooth cleaning device according to the invention, fig. 2 illustrates the invention seen from the bottom, fig. 3 illustrates the tooth cleaning device seen from the rear, fig. 4a-4c illustrates different cross sections of the invention.

Detailed description Referring to fig. 1, a front view of a preferred embodiment of a tooth cleaning device according to the invention is shown. The cleaning device comprises a rectangular holding portion 1 and two end portions 2,3 projecting out in the opposite direction of the holding portion 1. On one side of the end portion 2,3, a strengthening means 4,5 projects outwardly from the holding portion 1 toward the end. The strengthening means 4,5 will normally only extend beyond half of the end portion but any ratio between zero and one is possible.

In one embodiment, the holding portion 1 and the end portions 2,3 will normally have a central line 6 which is mainly a symmetrical line of the holding portion, the pointing portion 2,3 and the strengthening means 4,5 dividing them into mainly identical halves. The central

line can also be a line with no symmetrical relation to the portions e. g. an altitude line of a triangular end portion. The central line is, however, used to define the central point of the strengthening means seen in the transverse direction of the central line. The strengthening means may form a mainly symmetrical shape along the central line but can also be wider on one side of the central line than on the other. The strengthening means will normally have an inverted V shape or a more round"tongue"shape with a drop toward the end portion.

In fig. 1, one end portion 3 is shown as a hook like portion and the other as a pointing portion 2 but it is also possible to have tooth cleaning devices with only one end portion. A tooth cleaning device with two rectilinear, triangular end portions or two hook-like portions is also possible as are end portions with other shapes e. g. trapezoid or rectangular. In the illustrated embodiment, the angle of the hook X is between 90 and 165 degrees and preferably 130 degrees.

Even though not illustrated in fig. 1, the entire surface of the tooth cleaning device is preferably uneven. The uneven surface can partly be one kind of roughness and partly another or even have a partly smooth surface. The uneven surface will normally be a standard rough surface but can also be in a pattern e. g. parallel lines or any other polishing or massaging surface.

Referring to fig. 2, the tooth cleaning device is seen from the bottom illustrating the slim nature of the tooth cleaning device.

Referring to fig. 3, the tooth cleaning device is shown from the rear where no strengthening means is used on the end portions. In another embodiment of the invention, strengthening means on both sides can be used to ensure a very rigid construction of the end portions or with two smaller strengthening means ensuring the same rigidity as in the preferred embodiment of the invention.

Referring to fig. 4a, a cross section of the triangular end portion is illustrated at a point where the strengthening means has ended. The cross section illustrates the triangular end portion having a V shape in the opposite direction of the strengthening means.

Fig. 4b illustrates a cross section of the holding portion and indicates the oval shape with an end pointing downwards.

Referring to fig. 4c, a cross section of the hook-like end portion is illustrated at a point where the strengthening means has ended.

One of the characteristics of the invention is the end of the tooth cleaning device pointing downwards which is illustrated by the cross sections of figs. 4a to 4c.