STATE OF THE ART So called rubber dam laying is used in the dental field especially in connection with root treatments where an aseptic work area is needed, and when a dry work area is necessary, such as e. g. in connection with work with different so called bonding or composite techniques. Rubber dam laying is performed by an elastic rubber sheet being provided with a hole/holes for a tooth/teeth which is/are to be treated. The sheet is passed over the teeth, whereafter the rubber dam clamp keeps the sheet in place and the sheet is stretched by a so called rubber dam holder. When the sheet is stretched, the rubber dam clamp is exposed to large tensile forces, why it is of the greatest importance that it is securely attached around the tooth.

The problem is that all teeth are different. According to previously known techniques, this problem has been solved by production of a number of different clamp types, according to a given standard model type. There is a number of clamps for molars (large cheek-teeth), a number of clamps for pre-molars (small cheek-teeth) and similar for canines (eye-teeth) and incisives (front teeth). A standard assortment today covers some thirty different clamp models. Despite this it is hard to find a clamp that fits every specific tooth perfectly. This depends on the contact points or surfaces of the clamps of today being static and not adaptable to the surface of the tooth. The problem is intensified by many teeth, due to fractures on the crown substance, offering a very limited retention substance. Sometimes it is even necessary to remove tooth flesh in order to obtain the adequate retention. In other cases different types of cement or glue has to be used in order to attach the clamp to the remaining tooth substance.

ACCOUNT OF TE INVENTION It is an object of the present invention to solve the above problems, and therefore the present invention provides a rubber dam clamp which adapts automatically to the tooth surface, independent of its shape. This is achieved by a rubber dam clamp which exhibits the features specified in claim 1.

Accordingly, the rubber dam clamp has, according to the invention, been designed so that at least one of the contact parts is designed as a pivot part, which is connected with the arched part and arranged to move about a connection shaft for the connection of the arched part to the pivot part. The pivot part further comprises two or more contact tips on the side thereof which is intended to abut the tooth, whereby the pivot part is arranged to move about the connection shaft in such a way that at least two of these contacts tips, in a rubber dam clamp for a certain given tooth size, always is in contact with the surface of the tooth, if the clamp is of a size adapted for the tooth. Between the contact tips, the pivot part is preferably equipped with an edge-like surface.

Preferably, both the contact parts of the clamp consists of pivot parts, but it is also conceivable that only one of them consists of a pivot part, while the other consists of a conventional, stationary contact part. If one of the contact parts consists of a stationary part, the stationary part of the clamp, with its two contact points, is first brought into contact with the tooth. Thereafter, the pivot part adjusts itself so that also the two contact points of the pivot part are brought into contact with the tooth.

When the clamp is brought into contact with the tooth, or the tooth neck, one contact tip of the pivot part will always reach the tooth surface first. Since the contact part may rotate freely, or preferably within a certain limited area, it will rotate until the other contact tip is brought into contact with the tooth surface, due to the forces on the tips striving to be levelled. This will take place independent of the shape and surface of the tooth, provided that the correct size of rubber dam clamp is chosen. It may namely be an advantage to design rubber dam clamps according to the invention in four to six different sizes, for different tooth sizes independent of their location and shape. This should be compared to the need today of some thirty different models.

Thanks to the ability to pivot/rotate of the pivot part of the rubber dam clamp according to the invention, the retention to the tooth is considerably improved, since all four contact points, i. e. two on each side, always abut the tooth with a maximum force.

According to one aspect of the invention, the arched part is equipped with a recess which is adapted to a stop head on the pivot part. The stop head and the recess prevent the pivot part from rotating too much, which otherwise may lead to the clamp sliding off the tooth. The possibilities to attach the clamp to a defect or fractured tooth are also considerably increased when the contact points are flexibly arranged. The pivot parts, in the part thereof which is intended to face the tooth, are moreover preferably curved in

the direction of the connection shaft, away from the arched part. This makes it easier to reach with the contact parts behind the rim of the tooth flesh.

DESCRIPTION OF TE FIGURES The invention will in the following be described in greater detail with reference to the figures, of which: Fig. 1 is showing a preferred rubber dam clamp according to the invention, as seen from above, Fig. 2 is showing the clamp of Fig. 1, as seen in a side view, Fig. 3 is showing the clamp of Fig. 1 and 2, as seen from the front, Fig. 4a-c is showing two different types of pivot part, Fig. 5a-d is showing different rubber dam clamps according to the invention, arranged on four different teeth, Fig. 6 is showing a clamp according to the invention, arranged on a tooth with a rubber dam sheet and a rubber dam holder, Fig. 7a-b is showing a rubber dam clamp according to known technique, arranged on two different teeth.

Referring first to Fig. 7a-b, there is shown a rubber dam clamp according to known technique, which has been arranged on two different teeth. Despite the clamp being correctly chosen in terms of size, there is, as is shown, only achieved one contact point on each side of the tooth, when it is arranged on the tooth. Thereby, the retention to the tooth is bad.

In Fig. 1-3 there is shown a preferred rubber dam clamp according to the invention. The clamp comprises an arched part 1, the stiffness/elasticity of which gives the force which is applied on the tooth. The arched part 1 is thereby performed in a material with a suitable stiffness/elasticity, e. g. stainless steel or a composite based plastic material. The chosen elasticity of the arched part is depending on the width which the clamp should be clamped over. The dimension of the arched part must be adapted in order to generate a sufficient retention force when the clamp is arranged on the tooth. In different rubber dam clamps according to the invention, the width of the arched part 1 is adapted to the size of different teeth.

The arched part also exhibits two shanks la, at the inside of which the arched part is movably joined with two contact parts 2, which are constituted of pivot parts. Each

pivot part 2 is arranged to be able to rotate/pivot in relation to the shank la of the arched part 1, via a connection member 3, which is constituted of a connection shaft about which the pivot part may rotate. The connection shaft 3 is suitably arranged to be movably attached in a hole in the shank 1 a of the arched part and in a corresponding hole 23 in the pivot part 2 (see Fig. 4). The connection shaft is thereby equipped with an end stop/stop head in each end. As an alternative, the connection shaft 3 may be fixedly integrated with the shank la or the pivot part 2 in one end thereof, and exhibit an end stop/stop head 3a only in the opposite end.

In each of the shanks la of the arched part 1, there is moreover arranged a hole or recess 4 for the applying of the shanks of a rubber dam forceps, in connection with the mounting on a tooth. The arched part 1 may also be equipped with contact parts, which preferably are constituted of retention tips 7, suitably arranged in the transition part between the arched part 1 and the shanks la.

The pivot part 2 exhibits at least two contact tips 22, on the side thereof which is intended to abut the tooth, for contact with the tooth. Between the contact tips 22, the pivot part 2 exhibits a thin, concave, edge-like surface 24, which improves the retention to the tooth, especially in the extreme cases where all the tips 22 do not reach all the way to the tooth surface, depending on a tooth that is relatively seen too small for the chosen clamp size. Alternatively, or in combination with the edge-like surface 24, the pivot part 2, at least in the part thereof which is intended to abut the tooth, may be provided with a retention enhancing coating, e. g. a diamond coating.

The pivot part further exhibits, in the part thereof which is opposite to the contact tips 22, a stop head 6 (see also Fig. 4), which delimits the angular area within which the pivot part 2 may rotate. Accordingly, this means that the deflection of the pivot part is controlled. The deflection should namely not be too big, in any case not if the clamp is only provided with a pivot part on one side thereof, since the clamp in that case risks to slide off from the tooth. The stop head 6 is suitably arranged with a main extension which is parallel or essentially parallel with the connection shaft 3, and perpendicular or essentially perpendicular to the part of the pivot part 2 which is intended to abut the tooth. In the shank la of the arched part 1, on its outer side, there is arranged a corresponding recess 5, which is adapted to accommodate the stop head 6 and to provide two limiting surfaces for the stop head 6, for delimiting the ability to pivot of the pivot part, in two directions.

The pivot part 2 may be mounted on the top side of the shank la, or as is most clearly shown in Fig. 2, on its bottom side. The part of the pivot part 2 which is intended to abut the tooth, i. e. the contact tips 22 and the part 24 between them, is preferably arranged to be slightly bent in a direction which corresponds to the direction of the connection shaft 3, away from the arched part 1. This is most clearly shown in Fig. 3, and in Fig. 4c. The pivot part 2, or at least the part of it that faces the tooth, is moreover preferably narrow/thin, which, together with its bent shape, facilitates gripping behind the rim of the tooth flesh. The pivot part is preferably made in stainless steel and suitably exhibits a dull surface in order to avoid reflections.

From Fig. 4b it is clear that the point, in the shown case the hole 23, for the joining of the shank la and the pivot part 2, may be asymmetrically arranged in relation to a symmetry line A-A for the pivot part. Hereby, the force on the distal (rear) tip 22 may be increased, when the connection point 23 is displaced towards the distal tip. This may be desirable since the rubber dam sheet, when applied to teeth in the rear regions exerts a greater tensile force here, when it is stretched by the rubber dam holder. This force acts to heave over the clamp from the tooth, but may accordingly be counteracted by the asymmetric position of the connection point 23, shown in Fig. 4b.

In Fig. 5a-d there is shown different rubber dam clamps according to the invention, mounted on four different teeth. In the embodiment shown in Fig. 5 a, the clamp exhibits pivot parts 2 on both sides of the tooth, while the other embodiments exhibit pivot parts 2 only on one side and a stationary contact part, which is constituted by the shank la, comprising contact tips, on the other side of the tooth.

In Fig. 6 there is shown a rubber dam clamp 30 according to the invention, mounted on a tooth 31 with a rubber dam sheet 32 and a rubber dam holder 33.

The invention is not limited to the embodiments shown above, but may be varied within the scope of the following claims. Thus, it is realised e. g. that the pivot part as a whole, as well as the contact tips, may be given a different design, the essential feature being that the contact surfaces of the pivot part, against a tooth, are arranged to be able to pivot for a maximum contact with the tooth.