Dentistry – Apparatus – Having static product shaping surface
Reexamination Certificate
2000-02-23
2002-05-28
Manahan, Todd E. (Department: 3732)
Dentistry
Apparatus
Having static product shaping surface
Reexamination Certificate
active
06394802
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a device for producing tooth impressions with a tray that can cover a plurality of adjacent tooth positions of a jaw, the contour of the tray roughly matching the contour of the jaw.
Such a device is described in DE 41 30 701 A1.
In practice no completely satisfactory tooth impressions are obtained with such a known device.
SUMMARY OF THE INVENTION
The present invention is therefore intended to provide an improved device for producing tooth impressions with a tray that can cover a plurality of adjacent tooth positions of a jaw, the contour of the tray roughly matching the contour of the jaw, so that extremely accurate impressions can be obtained.
This objective is achieved according to the invention by a device that has the following features: The free edges of the tray walls run so that they can form together with soft tissues of a patient's mouth a sealing point, which tray is provided with at least one impression material connection element communicating with the interior of the tray, and with a source for liquid hardenable impression material that is connected to the impression material connection element, wherein the tray has at least one vacuum connection element communicating with the interior of the tray and that is connected to a reduced pressure source.
The following functions and advantages are achieved with a device according to the invention for producing tooth impressions:
The tray can be accurately positioned and firmly secured when used either on the upper jaw or on the lower jaw, and more specifically independently of mucous membrane activity or tongue movements. The tray does not need to be held by the dentist or by a dental assistant. Accordingly, not only are handling and manipulation substantially simplified, but the production of an impression is also less uncomfortable for the patient.
The tray is tightly sealed at the edge, so that no liquid impression material can escape from the tray and reach, for example, the throat.
On account of the fact that the impression space, which is bounded on the one hand by the tray and on the other hand by the patient's teeth and the gums surrounding the teeth, is according to the invention subjected to a reduced (sub-atmospheric) pressure, the edges of the gums are retracted slightly from the neck of the teeth, so that the initially liquid impression material also forms a good impression of the region of the teeth lying adjacent to the edge of the gums.
The device according to the invention employs the closed impression space already referred to above. This space may, before being filled with an impression material or also in application situations not connected with making impressions, also be used for the selective application of therapeutic agents, especially in the form of liquids, aerosols or gases. Such agents may for example include haemostatics, wetting agents, astringents disinfectants, fluoride solutions, desensitizing substances, deodorants, flavouring agents, substances for periodontal treatment, substances for caries prophylaxis, substances preventing plaque formation, wetting agents such as sodium lauryl sulphate, anitadhesives in the form of liquid solutions or aerosols, for example Delmopinol or Triclosan solutions, agents for dealing with salivary gland secretions, or physical therapeutic agents such as water, warm air and the like.
The device according to the invention involves a directed flow of liquids, for example of the aforementioned therapeutic agents or of the impression compound, from the impression material connection element via a predetermined flow pathway to the vacuum connection element. These added liquids flush out any liquids such as saliva and blood that may be present on the aforedescribed flow pathway. In this way a complete filling of the impression space is ensured. The relative movement between the liquids and the longitudinal axes of the teeth takes place at an angle other than zero, preferably at an angle of
90
°. In this way preferred flow directions can be established, from distal to mesial or vice versa, or from buccal to oral or vice versa. With the conventional impression techniques the tray filled with the impression material is mounted on the jaw in a direction perpendicular to the plane of the jaw, which means that the relative movement between the impression material and the teeth occurs parallel to the longitudinal axis of the teeth.
When using the device according to the invention the production of the tooth impression can also be combined with a therapeutic effect by for example adding a therapeutic agent to the impression material itself.
Also, various steps in the production of the impression can be combined, for example by adding, the wetting agent to the impression material itself instead of applying the wetting agent in a preparatory step to the surfaces of which an impression is to be made, or in the preparation of the material, thereby avoiding the need for this preparatory step.
The liquid hardenable impression materials that are used in the device according to the invention have a relatively high viscosity compared to water, typically that of the so-called “thin-bodied” impression or correcting compounds that are used for intraoral impression work (in contrast to kneadable impression compounds). For this reason they arc added under a positive pressure to the impression material connection element, and the reduced pressure generated in the impression space is chosen so that, on the one hand, the desired good edge sealing of the tray and the desired good positioning of the tray is ensured, but on the other hand no haematomas are formed in the tissues cooperating with the edges of the tray and the patient is not subjected to severe discomfort or pain.
The applied reduced pressure and the feed pressure for the impression material as well as the filling amount per unit time and the viscosity of the impression compound are matched to one another. While the impression space is being filled the reduced pressure and the feed pressure are maintained substantially constant, so that the impression material fills the impression space at a uniform rate (and thus in particular without any interruption), the front of the impression material displacing forwardly any liquids (water, saliva, blood) present in the impression space. These liquids are then sucked out through the vacuum connection element. This continuous filling of the impression space ensures that no enclosed bubbles on “shadow” regions formed by teeth against the filling direction are obtained in the impression.
Alternatively, during the continuous filling of the impression space the reduced pressure may first of all be lowered and then raised somewhat towards the end of the filling procedure, the reduced pressure and/or the conveying pressure being controlled overall in such a way as to ensure a continuous flow of the impression material. Care is preferably taken to ensure that the impression material does not come to a stop within the tray.
The filling of the impression space under a vacuum, which in the device according to the invention preferably takes place perpendicularly to the longitudinal axis of the teeth, ensures in particular that full impressions can be made without any delay also of undercuts lying underneath the tooth equator and of gaps between the teeth. Also, impressions of the tooth surfaces are made in a largely pressure-free manner, thereby avoiding errors due to elastic reverse movement of the impression material or due to any eddy formations on sharp tooth edges, for example in the region of preparation edges.
Tooth impressions using the device according to the invention are produced with a high certainty of success, with savings in time, and in a way that is more pleasant for the patient. More precise tooth impressions are obtained than is the case with conventional techniques. This does not only mean that the impressions have smaller tolerances, but also that there is a better wetting of more surfaces, even of surf
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