Dental paste-like porcelain

Details Dental paste-like porcelain Dental paste-like porcelain

2000-09-14

2002-09-03

Koslow, C. Melissa (Department: 1755)

Compositions: ceramic

Ceramic compositions

Glass compositions, compositions containing glass other than...

C106S035000

Reexamination Certificate

active

06444597

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a dental paste-like porcelain that is suitably used as a dental porcelain, such as a porcelain for laminated veneers, a porcelain for metal-ceramic restorations, and a porcelain for all ceramics, which are used for the preparation of artificial teeth and prosthetic restoration and in particular, require a special application technique by manual works of a dental technician.
2. Description of the Conventional Art
As the current of dental materials that have been put on the market in recent years, there are made various devices for shortening the time of an operation of the dental remedy or dental technique and making the operation easy. Further, machines for preparing metallic or ceramic tooth crowns, inlays, and veneers (one of techniques of the esthetic dentistry in which they are used upon being stuck onto a facial surface of a tooth) without needs of manual works through cutting processing by computer control typified by CAD/CAM (computer-aided design/computer-aided manufacturing) have begun to be put on the market. Thus, the dental technical works are being surely shortened in terms of time and made simple.
However, with respect to a porcelain application, which a dental technician who is mainly engaged in the dental laboratory works carries out, since a porcelain powder is in a sand-like state, it is poor in shaping properties. In addition to this, since water is used as a temporary binder with the porcelain powders, the buildup procedure is more difficult. And, in order to remove an excess of the water used as the binder during the buildup procedure, a condensation is carried out by imparting vibration. In the case where a person who is engaged in the dental laboratory works (the person being sometimes referred to as “person engaged,” hereinafter) is a beginner, the fired porcelain is liable to be deformed.
In particular, in the case where a long-span bridge or the like is prepared as a large-sized prosthesis, the porcelain application range is wide, and therefore, a possibility of occurrence of deformation of the fired prosthesis is high. Thus, it has been said that careful dental laboratory works for an excess of time are necessary. For this reason, of the persons engaged, only skilled seniors called as “ceramist” have been engaged in the application of the porcelain.
While such circumstances have continued, there is recently made an attempt to overcome the foregoing problems. In this attempt, a forming liquid containing a small amount of an organic material as the temporary binder with the porcelain powders, which imparts a predetermined shape more easily than distilled water, i.e., is good in shaping properties, is used, thereby making the porcelain application works easy to a slight extent. However, even in this attempt, there is no change in the matter that a condensation procedure is necessary for making the porcelain densely packed and removing the excess water after the buildup procedure in a later stage. And it is considered that the long-span porcelain application still requires a high-grade skillful technique.
In the case where a beginner undergoes the porcelain application with a commercially available porcelain, one of problems to be encountered is shade matching. That is, in the beginning stage, the buildup works themselves are considerably difficult. And, even when the buildup is carried out, in many cases, a color of the resulting prosthesis does not become an intended one. On the other hand, a paste-like resin material for crown and bridge that is used for the same purpose as a tooth-color crown material is easy for the buildup, whereby even a beginner can carry out the buildup including shade matching without any difficulty. This is because, although, in the porcelain application work, a step for firing at a high temperature of from about 650 to 1,000° C. after the buildup is included, the resin material for crown and bridge can be used as it stands without including such a firing procedure.
In other words, the porcelain considered to be put under desired conditions at the present stage is a porcelain that does not require a condensation procedure during the buildup in which a high-degree technique is required in the preparation of a prosthesis and which is easy in handling even by a beginner. And, this porcelain is a porcelain capable of providing a prosthesis that can be seemed to be comparable to or better than a prosthesis fabricated from the conventional porcelain that is provided in powder form and is mixed with either water or the like as a temporary binder just before the use, in terms of the shape and shade. This means that not only the operability as a porcelain is improved, but also, in comparison of the quality after firing, the physical characteristic and chemical durability are comparable to or better than those of the commercially available porcelains.
The above-described points will be specifically explained below. First of all, with respect to the shade, influences (such as blackening) by a residue, such as carbon, after the firing should not be visually observed; with respect to the influences by the residue, the surface properties should not be adversely affected, and unevennesses of the surface can be visually confirmed to be equivalent to those in the conventional products; due to the matter that the condensation procedure is not employed, porosity incorporated into the porcelain during the preparation or the buildup should not be present after the firing; and, with respect to the physical characteristic, the ISO standards as international standards must be met.
Then, in order to develop a porcelain meeting the above-described requirements, the present inventors made trials and errors only for a powder of the porcelain but could not obtain a satisfactory effect for which all of the above-described requirements are met. Thus, they did something new and paid attention to a liquid for mixing the porcelain. As the liquid that can be used for such utilization, for example, Japanese Patent Laid-Open No. 101818/1995 discloses one containing a photopolymerization initiator. However, such a liquid containing a photopolymerization initiator is problematic with respect to preservative properties. This is because, in not only the case where it is preserved over a long period of time or the case where it has been subjected to irradiation with an intensive light during the preservation, but also the case where it takes a long time for the buildup, the liquid itself and the porcelain during the buildup are hardened, whereby it becomes difficult to undergo forming. Further, since the reaction is commenced upon irradiation with a light, the step becomes complicated.
On the other hand, as an attempt to ensure the operability of a porcelain without necessity for paying attention to the preservative properties of the liquid as described above, for example, Japanese Patent Laid-Open No. 199853/1986 discloses an attempt in which the porcelain is formulated into a paste-like state by using glycerin. While this attempt is proper with respect to the directionality, it has become clear that it has difficulties in homogenizing the dispersion of the porcelain powder in glycerin, coming out of an ash as a residue (e.g., residual carbon), and regulating the viscosity.
The above-described glycerin is used as a binder for formulating an opaque porcelain (sometimes simply referred to as “opaque,” hereinafter) into a paste-like state, which is fused to a surface of a prosthesis made of a dental alloy to shield a metallic color of the ground. It is understood that this is low in viscosity according to the measurement results of the viscosity measured at a constant temperature of 23° C. by using a B type viscometer as described below. That is, when the revolution number is 1 rpm, the viscosity is so low that the measurement is impossible; and in the case where a conversion constant is set to be 1.61×10
4
, the viscosity is 1,932 cps at 10 rpm and 4,491 cps at 100 rpm, respec

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