Dentistry – Apparatus – Work support
Patent
1990-10-01
1992-03-31
Wilson, John J.
Dentistry
Apparatus
Work support
433 54, A61C 1100
Patent
active
051003171
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a device designed to be used when making dental prostheses from an impression taken in the mouth of the patient. It also relates to the method for using this device.
As is known, the production of a dental prosthesis involves first obtaining the exact replica of the dental arches to be reconstituted and/or restored. This replica, generally designated by the term "model" or "cast", is obtained by simple casting of a mold called an "impression". The impression is taken in the mouth of the patient directly by the dental surgeon, using a material of the alginate or silicone type.
Various types of impression-taking are carried out nowadays, namely, first of all, the so-called "total" impressions, which enable a complete model to be obtained for each of the two dental arches, then the so-called "partial" impressions, giving a partial model of one arch; finally, the partial impressions also called "bites", corresponding to a double partial impression, respectively the upper part and lower part simultaneously, both in the occlusion relation.
In a general manner the casting of the impressions is effected by simple filling, generally using plaster. The reproduction of the teeth and of the gingiva is first carried out. This reproduction is then placed on a plaster base with a view to producing a stable model. Once the upper and lower models corresponding to a given bite are cast for one and the same mouth, the dental prosthesist positions them in accordance with their occlusion relation, and this in as representative a manner as possible relative to the actual situation in the mouth. To do this, he uses an "occlusion device" or "articulator", that is to say an apparatus on which there are articulated two substantially parallel branches receiving the two upper and lower models.
European Patent EP-A0,151,086 describes, for example, a device permitting the preparation and the positioning of elements formed by reproducing the partial dentition of a patient and its gingival contour, extended by any positioning system called a "die" in the profession, in the field of dental prostheses. This device is employed using an occlusion device or articulator.
U.S. Pat. No. 4,496,320 also describes an occlusion device or articulator of the type in question, designed to permit the production of prostheses from impressions. This articulator consists of two plates fixed on the actual articulation device itself, the two plates each receiving one of the two impressions, upper or lower.
Similarly, British Patent GB-A-2,169,548 describes a device designed to permit the production of impressions, consisting of a serrated base. The impressions are cast directly on the serrated base. The prosthesist can then cut off the plaster and incorporate the various elements of the impression (dies) in accordance with the actual position in the mouth, without using pins.
All these devices present major disadvantages. First, their use necessitates a complex and generally expensive articulator. Moreover, and in particular, they do not take into account the natural expansion of the plaster during its solidification. It should be noted that even when a plaster of low expansion is used, which is moreover very expensive, the results obtained are not satisfactory. Indeed, the re-use of a solidified cast to represent again the impression in the articulator results in a different positioning from the initial positioning, on account precisely of the deformations observed by the expansion during the solidification of the plaster. In other words, deviations on the order of one to five tenths of a millimeter are commonly observed with this type of device, these being incompatible with the required quality and accuracy for the work of the prosthesist, and often being prejudicial as regards the resulting comfort of the patient. These deviations may in fact be at the origin of so-called overbite phenomena, that is to say that the bite of the artificial teeth does not correspond to that of the natural teeth.
SUMMARY OF THE INVENTION
The inven
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Cherichetti Cindy A.
Wilson John J.
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