Dentistry – Method or material for testing – treating – restoring – or... – Crown
Reexamination Certificate
1999-10-27
2001-06-26
Lucchesi, Nicholas D. (Department: 3732)
Dentistry
Method or material for testing, treating, restoring, or...
Crown
C433S219000, C433S226000
Reexamination Certificate
active
06250926
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to method for producing dental replacements wherein a pre-shaped ceramic part is applied to a dental support structure or a tooth stump model by a ceramic paste. The invention also relates to the dental replacement having a pre-shaped ceramic part that is connected by a ceramic paste to a dental support structure or a tooth stump model.
Such a method and such a dental replacement are known from German Offenlegungsschrift 36 04 059. A dental crown according to this publication is produced by first manufacturing a hollow cap and placing the hollow cap with the aid of a mineral dentin replacement material onto a tooth stump, i.e., a tooth stump model. The excess material which is pressed out by pressing the cap onto the tooth stump is removed or shaped and, subsequently, the assembly is fired. This solution is based on the known method of producing porcelain hollow crowns which are connected by tooth cement to the tooth stump model whereby instead of the tooth cement the mineral dentin replacement material is used for connecting the hollow cap to the tooth stump. This is designed to reduce the layer thickness of the hollow cap and to thus improve the esthetic appearance.
The manufacture of hollow caps according to German Offenlegungsschlinfs 36 04 059, however, has been difficult and has shown to be disadvantageous in practice. For example, a plurality of hollow caps with respective color, size, and shape of the desired tooth replacement must be premanufactured and stored so that it is necessary to have an extensive hollow cap supply in storage. On the other hand, the esthetic result is not satisfactory because the external shape of the replacement tooth is always a standard result. The coloration can not accommodate the differentiation of natural teeth even when, for example, the supply of 100 different hollow caps is provided which is necessary for five different colors, five different shapes and four different front teeth.
In contrast, pre-shaped ceramic parts have the advantage that the shaping of the tooth replacement can be individualized while, in contrast, it is essentially predetermined for hollow caps.
Since the hollow cap method has not found acceptance, it has also been suggested to apply multiple ceramic support layers onto a dental support structure or a tooth stump model in sequence in order to allow for an individualized esthetic appearance that closely resembles a natural tooth. The layers can be produced in the dental lab according to an impression. This, for example, known from U.S. Pat. No. 4,473,353 according to which a corresponding layer is applied with an acrylic adhesive after a respective impression has been prepared.
A similarly adhesively connected hollow cap is also known from U.S. Pat. No. 4,813,874. This method also includes producing an impression and does not employ premanufacture so that the work expenditure is relatively great.
It is therefore an object of the present invention to provide a method for producing dental replacements as well as a dental replacement of the aforementioned kind which provides an esthetically pleasing inexpensive tooth restoration which can be produced quickly.
SUMMARY OF THE INVENTION
This object is inventively solved by applying a fired, pre-shaped ceramic part onto the labial or buccal side of the tooth replacement so that it is at least partially embedded or enveloped by a ceramic paste.
The invention provides the advantage of using an embedded fired pre-shaped ceramic part. This is applied to the labial or buccal side of the tooth stump and is embedded at least partially by a ceramic paste. This inventive solution insures that individualization that is made possible by modeling and coloration of a ceramic paste, is realizable despite premanufacture of the ceramic part. On the other hand, it is no longer required to apply a plurality of ceramic layers in a sequential order and to fire each ceramic layer separately so that the work expenditure in the dental lab is greatly reduced.
In this context it is especially favorable when one or multiple, preferably two-layer, ceramic parts are used. Such a two-layer ceramic part is very similar to the translucence of natural teeth and is partly visible since it is at least partially embedded by the ceramic paste. This allows for a great simplification of the generally required layer technique on the visible labial or buccal side, which, has usually a curved (bulging) exterior shape, i.e., instead the application of the pre-shaped fired ceramic part is possible. It is understood that, in principle, a matching fired and pre-shaped ceramic part can also be used at the lingual side, whereby, on the one hand, the esthetic requirements in this area are less stringent and, on the other hand, since the exterior shape for molars is slightly convex and in the incisor area even concave, less material is required.
Inventively, it is suggested that the support structure which is comprised of a metal alloy is covered by an opaquing agent, and the support structure together with the opaquing agent are fired together. The opaquing agent has a higher melting temperature than the ceramic part and the ceramic paste so that it remains solid at the firing temperatures for the ceramic part as well as for the ceramic paste.
Onto the opaquing agent, which has a surface that has good adhesive properties, the ceramic paste is applied in excess and then the pre-shaped ceramic part is pressed onto the labial or the buccal side. Onto the pre-shaped ceramic part the same ceramic paste is then applied and shaped or modeled whereby this additional application already corresponds to the application of the last layer in the layering technique.
The finish-modeled dental replacement is then fired. Accordingly, with the inventive method the manufacture and individual firings of the first, second, and third ceramic layers can be produced with one single firing. It is understood that it may be expedient to employ the conventional painting technology, in the same manner as in the layering technique, whereby the coloration is individualized and, subsequently, a further firing process is undertaken.
Inventively, it is especially advantageous that the employed ceramic materials for the ceramic paste as well as for the pre-shaped ceramic part are compatible. Accordingly, there is hardly any difference or no difference at all in the heat expansion coefficient of the pre-shaped ceramic part and the ceramic paste so that there is no risk of crack formation.
Furthermore, the dental technician must not be especially trained for use of the inventive ceramic parts. The application of individual layers, is has been used in the past, requires considerable experience, while the method of the present invention can be easily performed by a less experienced dental technician which in the end is beneficial in regard to the quality of the dental replacement.
It is especially advantageous that the ceramic part is industrially pre-manufactured of two or more layers. It is only necessary to provide sets of small numbers, for example, three each for the incisor and the molar area of the jaw. These ceramic parts can be integrated anatomically and esthetically such into the ceramic paste that after firing a transition between the fired ceramic paste and the pre-shaped fired ceramic part can no longer be detected. The ceramic part is inventively partially imbedded in the ceramic paste and is thus integrated into the dental support structure. Its surface is preferably such that the surrounding ceramic paste will adhere well thereto which is also beneficial with regard to the stability of the dental replacement part.
At a firing temperature between 660° and 950° c., the ceramic pastes and the ceramic parts can be fired together such that no special requirements with regard to the selection of the firing furnace must be complied with. It is instead possible to employ the conventional furnaces for producing metal ceramics.
REFERENCES:
patent: 3761728 (1973-09-01), Kochavi
patent: 4879
Foser Hanspeter
Ubassy Gerard
Ivoclar Vivadent AG
Korman Alan S.
Lucchesi Nicholas D.
Thompson John C.
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