Patent Application
20080286714
The invention relates to an impression tray with a concave tray body for taking an impression of at least one jaw part, in which at least one implant body is situated, which body has a receiving aperture into which an impression post may be inserted, it being possible to fill the impression tray with a free-flowing hardenable impression material to produce a mould for a model of the jaw part.
As is known, when one or more teeth are lost replacement roots, what are known as implants, are implanted into the jaw. These supports that are anchored in the jaw form the stable base for new, secure teeth. The size and shape of an implant is guided by the individual preconditions of the jaw of the patient being treated. One precondition for tooth implantation is a minimum jaw bone substance.
Since implants are osseo-integrated (anchored to a bone) and, in contrast to natural teeth, do not—ideally—have even the slightest inherent movement, when constructing a plurality of implants an optimally exact three-dimensional reproduction of the position of the individual implants is particularly important.
The replacement produced in a dental laboratory can only be successfully incorporated in the oral cavity without stress if the clinical situation is transferred exactly to a model. While a precise impression is not a sufficient condition it is a necessary one for implantological-prosthetic care.
The aim of any impression is thus the exact dental model. It is used for diagnosis, planning and treatment purposes as well as a work basis for the dental technician and should be an exact copy of the structures that are in the oral cavity.
The part of an implant system that is countersunk into the bone is either called an implant body or simply an implant. Once it has been introduced into the bone the hollow implant body is provided with a cover screw. The gums are then stitched over the implant body. Following a healing phase of several months' duration, the doctor then exposes the implant body again, removes the cover screw and temporarily screws or inserts an impression post in its place.
After a healing period of 10 to 14 days, the impression may be taken over the impression post by means of an individually shaped impression tray in order to subsequently produce the crown, bridge or prosthesis. The impression post is then replaced for a few days by healing abutments. The definitive new teeth are not secured directly to the implant bodies, but to implant superstructures, however. Implant superstructures bridge the thickness of the gums, so the gums cannot be squashed between implant body and prosthesis. The healthy gums attach to these implant superstructures as to a natural tooth. The prosthesis accordingly supported by the implant abutment and implant body is called a superconstruction and is secured by filling screws or other fastening principles to the individual implant bodies.
To determine the three-dimensional position of the implant body and to transfer this to the final laboratory model, the following steps are carried out:
1. Taking a negative impression of a jaw, or jaw part, by means of a standardised impression tray, a cover screw, arranged inside the impression tray, being screwed into the implant body,
2. a) Producing a first laboratory model using the negative impression,
The repositioning technique may be used as an alternative. The major advantage is that the patient is spared a treatment appointment for production of the individual impression tray. A further advantage is also that the costs that occur during production of the individual impression tray with respect to expenditure of material and time do not apply in the case of the repositioning technique with ready-made trays.
However, a drawback of this technique is that its application is error-prone and has also been proven to be less precise compared with the above-described “pick-up” technique since, inter alia, the channel-like impression of the impression post required for the three-dimensional repositioning of the position of the implant body in the impression material may only be replaced by shallow and imprecise impressions of impression elements and hence leads to unsatisfactory results for the doctor and primarily the patient. Repositioning of the impression tray also leads to significant movements in the impression material, so the precision of the subsequent model decreases.
Guillaume et al disclose in U.S. Pat. No. 6,468,078 B2 a ready-made tray comprising a plurality of removable segment seals. Depending on the position of the impression post—which is constructed as a sleeve—it is proposed that the segment seal located thereabove be removed and the material, which is still covering the impression post and a screw fixing the post to the implant body, subsequently be removed until at least the screw head is completely exposed. After the impression material in the ready-made tray has hardened the screw should be detached. The impression post remains in the impression material moreover and is used to fix the laboratory implant using the impression screw.
When using the proposed impression tray however the process of removing impression material over the screw, which process on its own is already complex but, owing to hardening of the impression material, is also limited in terms of time, may lead to considerable problems. The exact position of the screw must also firstly be ascertained and then the screw head freed of the impression material, at least to the extent that the screw may be engaged using a screwdriver or the like. A further drawback is that the interplay between impression post and positioned impression tray may no longer be checked and corrected if necessary since the impression post can no longer be seen in its position relative to the impression tray.
The object of the invention is to propose an impression tray which when used reduces the time spent in the dentist's chair, increases the precision of an implant model and finally reduces the material and labour costs.
The object is achieved according to the invention in that, at least in one portion, the tray body has a wall which can be penetrated by an impression post inserted into the implant body if the impression tray is placed onto the jaw part.
The advantages of the respective known impression taking techniques are combined by the invention. On the one hand production of an individual impression tray may be omitted in that the impression tray according to the invention is produced as a ready-made “disposable or reusable serial tray” in appropriate standard sizes. On the other hand, implant impression taking may still be carried out using the precise pick-up technique that is much favoured, since the walls of the impression tray, usually the base wall, can easily be penetrated by the impression post. This is advantageous because, as a result, the impression post can be removed again after the impression material has cured and the finished impression can be removed from the mouth. Impression material is also effectively prevented from escaping with the adverse effects associated therewith.
As a result of simple handling and safety the impression tray according to the invention results in a time saving which is of benefit to both the dentist and the patient.
In addition, a cost reduction therefore already results due to the fact that previously hand-made unique copies are replaced by serial products.
And not least of all, dental procedures that are harmful to health, as occur in the production of individual impression trays as a result of the production of silica dust, are avoided.
One development of the invention is that the impression tray comprises struts, which form a frame, and a membrane located therebetween to thus allow the greatest possible variability with respect to the possible implant placements and the implant orientation while still having a stabilising frame.
Another development of the invention is that for an improved penetrating capacity of the impression material and the wall of the impression tray, the impression post comprises a final shape that is beneficial to penetration, for example tapers or cutting edges, or a removable cap with a corresponding final shape. Obviously the scope of the invention also extends without any limitations to the field of veterinary medicine since all illustrated advantages benefit animals and their owners equally as well.
The invention shall be described hereinafter with reference to an embodiment.
In the drawings:
The one-piece impression tray 1 illustrated in
In alternatives according to the invention (not shown here) different material is provided for the impression tray 1 and the film 7. The impression tray 1 may therefore also be made of metal which comprises apertures in the region of the wall 6, 6′ that is still covered by film 7, non-woven fabric or laminated woven fabric. For this reason a conventional metal, ready-made tray, if it has a recess which is covered with conventional adhesive tape, for example single-sided tape, obviously also falls within the scope of the invention.
Alternatives in which the penetrable wall 6, 6′ can take up a complete wall region of the impression tray 1, such as the base region of the impression tray 1, are not shown either.
A further alternative (not shown) is that curved coverings or penetrable walls 6, 6′ are used in the case of an extremely oblique position of the implants 18. Alternatives that relate to variations in joining the penetrable wall 6, 6′ and impression tray 1 are not shown either. Thus for example the penetrable wall 6, 6′ can be secured to the impression tray 1 from the inside and from the outside using overlapping regions of different widths. Securing may be achieved here for example by gluing or by mechanical fixing and/or jamming.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2004 022 066.2 | May 2004 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2005/04794 | 5/3/2005 | WO | 00 | 1/17/2007 |
