I Device for treating a tooth

The present invention relates to a device for performing a filling operation on a tooth, comprising a bearing part for bearing on a tooth and a band fitted around this, and an adjoining transition part that is/can be connected to a handle, wherein said bearing part and transition part are elongated and each delimit a longitudinal axis, which longitudinal axes are arranged at an obtuse angle with respect to one another, wherein the external cross- section of said bearing part is a polygon.

Such a device is disclosed in WO 02/15812 in the name of Tandarts Praktijk P.G. HeesenB.V.

In this PCT application a novel method and device are proposed for filling cavities in teeth and more particularly molars. In this case a band is used that provides the separation between the open end part of the cavity to be filled and an adjacent tooth. Preferably, the shape of the filling should be such that the adjacent teeth are in contact with one another close to the free top end, but that there is an appreciable distance between them at a lower level. In order to achieve this, according to the publication WO 02/15812 it is proposed that the dispensing end of the dispenser head is provided with a bearing part, the curvature of which corresponds to the desired curvature of the tooth at the location where this has to touch the other tooth. After introducing filling material into the cavity to be filled, the device is pressed against the band. Hardening of the filling material is then carried out with the aid of exposure to light and when the device is subsequently removed further material is filled into the residual cavity and then hardened, again by exposure to light The hardened filling material present around the dispensing head gives adequate stability to leave the band in the desired position and by filling the opening thus obtained with further filling material when the device is withdrawn and hardening said material a shape can be obtained for the filling that corresponds to the optimum shape of the filling described above, as a result of which contact of the teeth at the free top end thereof is ensured.

In the construction according to WO 02/15812 the dispensing head is provided at the free end with two diametrally opposite bearing surfaces. The plane that passes through the axes of the reservoir and the bearing part delimited by the bearing surfaces intersects the cross-section of the bearing part formed by the bearing surfaces. At that location the bearing surfaces (lines) extend both distally and proximally approximately perpendicular to the line of intersection of said plane with the

cross-sectional plane.

Although such a device is found to be eminently suitable in practice, it is not possible, or is possible only with very great dexterity, for a single device to suffice hi all positions of cavities in teeth. Li this context it must, in particular, be taken into consideration that it is important that sufficient room remains to be able to position the tool in a simple manner for exposure to light. Therefore, various devices are used. Furthermore, it has been found that problems arise as a result of the shrinking filling material. When the device disclosed in WO 02/15812 is positioned a firm material bridge is obtained that joins opposing sides of the cavities. If this material hardens, there is a risk that the material shrinks away from the walls of the cavity, with all the associated consequences.

Furthermore, the device according to the abovementioned PCT application is provided with a lateral cut-out of elongated shape. As a result it is necessary to use another device for filling front teeth.

The aim of the present invention is to provide a device with which it is possible to provide optimum positioning under all circumstances, hi this context it is, on the one hand, important that there is sufficient room for exposure to light, but, on the other hand, it is important that the band can be pushed away in a suitable manner by the device.

This aim is realised with a device as described above in that the corner point of said polygon is essentially located in the plane determined by said axes, said corner point comprising the most distal part of said cross-section.

According to the present invention a pressure in the direction of the adjacent tooth is exerted on the band with the device according to the invention. The device will be positioned depending on the position of the tooth concerned. Furthermore, the various aspects are dependent on the manner of hardening. If exposure to light is used for this purpose, this must also be taken into account. In general this means that if a contact point is formed at the back of a tooth the device is positioned at an angle with respect to the dental arch. In this case some degree of pushing is applied. If the front of the tooth has to be filled, the device is aligned roughly in the direction of the dental arch and pulled with some force. In contrast to the state of the art, the surface adjacent to the front corner point will be pressed against the band. Because two surfaces extend from the corner point the device can be used on both sides. Because these bearing surfaces extend at an angle to the abovementioned plane determined by the two axes, the device and any syringe gun coupled thereto will be positioned at an angle, as a result of which the back teeth can also be

reached and if necessary exposed to light in a simple manner. That is to say the device can be used universally both on the left and on the right, both at the front and at the back and both by left-handed and right-handed persons.

According to the present invention the bearing surfaces that determine the outer limit of the filling and thus of the tooth close to the cavity are no longer diametrally opposite one another. The lines that join the ends of the bearing surfaces are positioned at an angle to one another. According to the invention this angle is greater than 15° and smaller than 180° and preferably greater than 30° and more particularly approximately 80°.

The bearing surfaces can be made straight, but according to an advantageous embodiment of the invention are made arched. In the first case the lines that join the ends of the bearing surfaces are coincident with the end limit of the bearing surfaces and in the second case the lines are formed by the chords.

With this arrangement two, three, four or more bearing surfaces can be used. According to an advantageous embodiment of the invention, three bearing surfaces are used. In the case of a particular embodiment of the triangle, the base extends perpendicularly to the abovementioned plane that is defined the axes through the bearing part and the transition part. There is always a linking part between the base and the adjoining line, which linking part extends perpendicularly thereto. As a result a polygon is in fact produced. As a result of the preferably triangular, rectangular or polygonal shape of the bearing surfaces a large surface area of the cavity can be covered by the device.

The device according to the invention can either be used in combination with a syringe gun or can be solid. If the various features are used in combination with a syringe gun, the transition part and the bearing part are, of course, made hollow. Furthermore, in such a case a dispensing head is provided with a dispensing opening for introducing the filling material. With this arrangement when the device is positioned in the cavity after the first introduction of filling material (and after any sculpting the relatively solid material bridge that is known firom the state of the art is no longer produced. As a result, the risk of shrinking away from the boundary of the cavity is reduced when the filling material shrinks and in that case filling material will break away at another location directly adjoining the cavity covered by the device. When the device is removed and the cavity thus produced filled with further material, such gaps can easily be filled.

Under certain circumstances the composite material used can be highly viscous. In

particular, highly viscous material is used because such a material shrinks less than material of low viscosity. Li such a case it is important that the outflow opening of the dispensing head has as large as possible an effective cross-section. According to a particular variant of the invention this is obtained in that there is a rounded transition part between two bearing surfaces. As a result the composite material can easily move out of the outlet of the dispensing head.

It is also possible to choose a circular or oval outflow opening. As indicated above, it is important that the filling extends further outwards close to the free end of the tooth, such as a molar, than close to the "root end". According to an advantageous embodiment of the invention, to this end the end of the dispensing head is made tapering towards the "root end". Furthermore, for the most extreme part of the free end of the dispensing head it is not necessary that the band is pushed outwards by this. In theory, this can have a somewhat different shape to the shape that has been described above. However, it is also possible to make the shape described above extend over the full height of the dispensing end of the dispensing head, there being a transition region for reducing the size. As a result of the tapering shape of the bearing part described above it is possible to press a bearing surface with a larger or smaller width against the band by positioning the device more or less deeply. As a result the desired shape of the tooth can be obtained. The device described above can optionally be provided with lateral cut-outs close to the outlet opening. If these are not present, it is possible also to use the device according to the invention for applying filling material only. That is to say the device can be used when filling teeth such as front teeth.

The invention also relates to a filling tip that can be used in combination with the device described above. This can easily be interchangeable as a unit and made disposable. Under certain conditions and more particularly when filling back teeth there can still be a problem with exposure to light despite the improvement described above.

This problem can be overcome by using a, preferably transparent, instrument (aid) with the same or a larger shape. After forming the contact point by means of exposure to light though this instrument the filling tip fits in the cavity and it is still possible to finish the filling easily, without air inclusions.

More particularly, this is of importance with the device described above because this is suitable for reaching a tooth in a wide variety of positions and filling said tooth.

The method for filling the tooth is then carried out as follows.

After producing the relevant cavity this is filled in some way or other with filling material and sculpted. This sculpting can be carried out with the auxiliary device described above. The auxiliary device is then introduced in a position similar to the position of the device according to the invention. The opening that is made using the auxiliary device is preferably at least as large as the opening which the device according to the invention will make. The material is then hardened by exposure to light. The auxiliary device is then removed and further material is introduced using the device described above, followed by hardening. With this procedure the formation of air inclusions is counteracted as Jar as possible.

The present invention also relates to an instrument comprising a syringe gun, the end of which is designed for coupling to a filling tip, as well as a filling tip comprising a cartridge with a dispensing head, wherein said coupling comprises a first, relatively deep seat in the coupling end of the syringe gun followed in the distal direction by a second, shallower seat, wherein said cartridge is provided with corresponding projections, wherein said coupling contains means counteracting rotation. Preferably a mechanism that at least partially encloses the cartridge is made on the syringe gun. By this means it is possible that with a combination of a syringe gun and a filling tip substantial lateral pressure on the filling tip can be exerted by the dentist without the filling tip turning with respect to the syringe gun or being pushed out of the syringe gun as a result.

The invention will be explained in more detail below with reference to an illustrative embodiment shown in the drawings. In the drawings:

Fig. 1 shows, diagrammatically, the device according to the invention;

Fig. 2 shows, in perspective view and in more detail, a dispensing head fitted on the device according to Fig. 1 ;

Figs 3a - d show, in detail, in a number of cross-sections the dispensing end or outlet end of the dispensing head;

Figs 4a, b show the positioning of the device when filling various sides of teem;

Fig. 5 shows, partially in cross-section, positioning of the dispensing end of the dispensing head during filling;

Fig. 6 shows a plan view of the positioning in Fig. 5;

Fig. 7 shows further positioning of the dispensing end;

Fig. 8 shows part of an alternative device with dispensing head according to the

invention and

Fig. 9 shows a variant of the construction shown in Fig. 7. A so-called composite syringe is indicated by 1 in Fig. 1. This consists of a filling tip 2 and a handle 3. There is a part 4 which acts as pressure rod and can be moved by operating the handles 3. The filling tip 2 consists of a tubular part or transition part 6 with a piston, which is not shown, in which rod 4 can move back and forth. A bearing part 11 adjoins tubular part 6 and, in turn, a dispensing head 9 provided with an outlet opening 7 adjoins said bearing part 11. The tubular part 6 is provided with an inlet for the rod 4. As can be seen from Fig.2 there is a rim 8. As a result of the shape of rim 8 and tubular section 6 the filling tip 2 can be removed from 1he handle 3 in an easily removable manner. That is to say the filling tip 2 is a disposable product for single use, whilst the handle 3 can be used several times.

It can be seen from Figs 2 and 3 that the externally circular dispensing head 9 gradually merges into the bearing part 11. The bearing part 11 , in turn, merges at an angle into the transition part 6. The axis of said transition part is indicated by 50 and the axis of the bearing part 11 by 51. An angle φ is delimited between them. This is an obtuse angle and this is preferably approximately 130°. Surprisingly, it has been found that when such an angle is chosen optimum movement of filling material from the transition part to the dispensing head 9 is possible with the terasition from a circular cross-section to a triangular cross-section. The bearing surfaces of the bearing part 11 are indicated by 13, 14 and 15 in Figs 3a - c. These are triangular, the sides or surfaces 13, 14 and 15 acting as bearing part. These sides are somewhat arched. It must be understood that these can also have a different shape, such as rectilinear. Roundings 56 are made between the sides in each case. Chords a, b and c, respectively, can in each case be drawn between the ends of the arched sides 13, 14 and 15. These chords intersect one another at an angle α, β, γ. In the present illustrative embodiment this angle is always approximately 60°. It will be understood that this angle can have other values depending on the design of the parts 10-12. However, according to the present invention this is between approximately 15° and approximately 90°. The line of intersection 53 of the plane defined by the axes 50 and 51 with the cross-section shown here is also shown in Fig. 3 in each case. It can be seen from this that the most remote part of the instrument is the corner point between the two surfaces 13 and 14.

A variant is shown in Fig. 3d. In flu ^' s variant the angle between the sides 63 and 64 has been chosen to be larger than 60° and more particularly is approximately 80°. The

various features are possible by making linking parts 59 which extend from the base 58. It is clear that, like the base 6 shown in Figs 3a and 3b, this base 58 is perpendicular to the line of intersection with the plane defined by the two axes 50 and 51.

The use of the device described above is shown in Fig.4. A set of teeth is indicated by 23, the teeth 24 and 25 both having been provided with a cavity 27 to be filled, which cavity is in each case open in two directions. A band 26 that is positioned between two adjacent teeth is used for filling such cavities. This band 26 serves to delimit the shape for the tooth that has to be filled. This is shown more clearly in Figs 5 and 6.

The first step is filling the cavity 27 concerned in the conventional manner. Preferably this is carried out using the device described above. However, it is also possible to provide filling of the cavity in some other way. A sculpting step can then optionally be carried out.

Because it is important that the teeth touch one another at the top, but are some distance apart at the root end, according to the present invention it is proposed that, after introducing the filling material, the device described above, and more particularly dispensing head 9 thereof, is re-introduced into the cavity, displacing filling material already present. The dispensing head is pressed against the top of the band and the composite material is exposed to light while this position of the device according to the invention is maintained, as a result of which hardening takes place. It can be seen in particular from Fig.6 that at the back of the tooth either surface 13 or surface 14 or surface 63 or surface 64 is pressed outwards against the band in the direction of the arrow. That is to say, with the correct choice, the instrument according to the present invention is at an angle of less than 90° to the axis of symmetry drawn in Fig, 4. As Fig. 7 shows, when treating the front of the tooth, surface 15 is used, the pulling force being exerted about in the direction of the dental arch (in the direction of the arrow). Subsequently, optionally when the remaining cavity is filled with further material immediately, the device according to the present invention can be removed without the band 26 springing back to a substantial extent. This additional material in the residual cavity can then be hardened. As can be seen from the combination of Fig. 5 and Fig 3, the contact surface with the band will be narrower when the dispensing head 9 is positioned higher, because of the tapering of the dispensing head. That is to say, the "width" of the bearing part can be chosen by selecting the position of the dispensing head with respect to the filling band or the rest of the tooth, respectively.

An auxiliary device is used with one variant of the invention. This auxiliary device has a dispensing head that essentially corresponds to the dispensing head 9 that has been described above. However, this is not provided with an outlet opening and this consists of a material that allows radiation to pass through. After introducing and sculpting the filling material, optionally using the auxiliary device, such an auxiliary device, and more particularly the dispensing head thereof, is positioned in the same way as indicated above. The material is then exposed to light, this being promoted because light is able to pass thorough the dispensing head and is able to reach the filling material. The auxiliary device is then removed and the device that has just been discussed is inserted and withdrawn from the cavity concerned while additional filling material is dispensed.

Because of the particular shape according to the present invention it is possible to work in various positions using one device, as can be seen from the positions shown hi broken lines hi Fig.4a and Fig.4b. In each case a different side 13, 14, 15 is used to press the band against the adjacent tooth. As a result of the particular shape of the parts 10-12, Ae desired contour of the filling over the height of the tooth is obtained.

As can be seen from Fig. 5, portion X, in particular, is of importance for positioning the band 26. Portion Y, that is to say the bottom portion of part 10, is less important and is relevant mainly as an outflow opening. If, in particular, a relatively viscous filling material is used (which is desirable in order to prevent shrinkage as far as possible), the aim is for as large as possible an outflow surface area with as small as possible a circumference (circle). The size of portion Y is between 1 and 4 mm. The length of portion X is approximately 7 mm.

It will be understood that using the present invention it is possible both to create contact points between molars in the most difficult position and also to provide other teeth with filling material using a single device, hi addition it is, moreover, still possible to apply sufficient force to push away the band used, whilst, moreover, there is sufficient room to harden the filling material introduced with the aid of light in an effective manner whilst maintaining the position of the device according to the invention. Part of a modified embodiment of the handle according to the invention is shown in

Fig. 8. More particularly, the end part thereof, which has to be coupled to a filling tip 32, is shown by 30. This handle can enclose any filling tip according to the prior art. As in the case of the previous embodiments, this filling tip 32 is provided with a rim 38, whilst the

end concerned is provided with a corresponding groove 33. The filling tip 32 can be introduced into the opening 35 of end part 30 along the direction of arrow 34. During introduction the ring 37 is in the position shown by a continuous line. The position shown by fihe broken line is obtained by rotation of the ring 37 in the direction of the arrow 41. In this position it is no longer possible for the filling tip 32 to be removed from the end 30.

The opening 35 can also optionally be provided with means which increase engagement wim the filling tip 32, such as ribs 39.

40 indicates a stop that restricts the rotation of ring 37. It must be understood that such a locking device, either in combination with the present invention or independently thereof, can be used in the combination of a handle with any other filling tip. As a result of this construction turning of the filling tip with respect to the syringe gun is precluded.

In Fig. 9 a variant of the construction described above is shown where the filling tip is provided with a single raised rib and the syringe gun is provided with a number of grooves. As a result the filling tip can be locked in a number of discrete positions with respect to the syringe gun.

Afler reading the above variants will be immediately apparent to those skilled in the art. These fall within the scope of the appended claims.