Method for molding dental restorations and related apparatus

ES 2 235 698 T3 description

Dental restorations.

Related requests

This application is a divisional of application No. 0711133A (WO 95/32678).

Scope of the invention

The present invention relates to dental restorations such as crowns, bridges, inlays, superimposed prostheses, etc. from glass-ceramic materials.

Background of the invention

In the state of the art, various methods have been used to form metal-free dental restorations from glass-ceramic materials. Due to their resistance, their translucency, their non-toxicity and other physical properties, glass-ceramic materials are ideal materials to be used in the formation of dental restorations. Due to their suitability, glass-ceramic materials have been used to form dental restorations for at least eighty years. In the state of the art, the most widely used means for forming dental restorations from mixtures of vitreous materials and ceramic materials is a process in which a grout of vitreous and ceramic particles is used. In this procedure, a mold is formed that is an exact replica of the remaining part of the tooth to which the restoration must be attached. One skilled in the art understands that the remaining part of the tooth has been adequately prepared by the dentist to facilitate the bonding of the restoration. To start the process, the dentist takes an impression of the prepared tooth to create a negative impression of the prepared tooth or prepared teeth. This negative impression is then filled with a material to form a positive impression of the prepared tooth or teeth. This positive impression is called a mold. Platinum foil is then pressed onto the mold to form a matrix that essentially constitutes a base on which the dental restoration is built. In order to form the dental restoration, many layers of a slurry of a particulate glass-ceramic material are applied to the matrix formed by the platinum foil. As multiple layers of the grout are successively applied over each other and dried, a semi-solid structure is formed that can be carved into the shape of the desired dental restoration. Once the desired shape is achieved, the structure is then removed from the mold. At this stage the framework is called the uncooked framework. The structure is then fired, and during the fire-cooking process the particulate glass-ceramic material undergoes a fusion, becoming a homogeneous mass. Due to the fact that the uncooked structure is formed from multiple layers of the dried glass-ceramic material, non-uniform melting can occur as a result of said process. As a result of this non-uniform fusion, the physical properties of the finished restoration can be adversely affected. This results in obtaining a low-quality dental restoration. Furthermore, as can be seen in the light of the above description, the whole process consumes a large amount of labor.

In the state of the art, other methods to form the unfired restoration have been considered, and thus, for example, in US Patent No. 2,196,258 a flexible mold is filled with a mixture of vitreous and particulate ceramic materials that incorporates a binder. to form an unbaked structure which is then fired to form a finished structure. Also in this case, since the process involves the fusion of the particulate material, a non-uniform fusion can be obtained as a result thereof, which consequently can result in obtaining a weakened and inferior quality dental restoration.

To overcome the problems that have been described above, it has been recognized in the art that in order to produce metal-free dental restorations that are translucent and strong it would be desirable to form these restorations directly from a homogeneous fused glass-ceramic material. It was appreciated that it may be possible to produce a satisfactory restoration by pressing a molten glass-ceramic material or plastic into a mold having a cavity having the shape of the desired dental restoration. It has also been recognized in the state of the art that the glass-ceramic material could be introduced into the cavity when the glass-ceramic material is in a liquid state or in a plastic state.

As described, it has been an end incessantly pursued in the state of the art to carry out the molding process quickly and efficiently and in such a way that a dental restoration having excellent definition and excellent fit is produced. In dental restorations, definition is extremely important, since in order to achieve a satisfactory restoration, the smallest details of the original tooth must be reproduced. For example, for a dental restoration to be successful, the margins must be cleanly executed and well defined. It is in this field that the molding processes of the state of the art are deficient in that it was not possible to achieve the desired degree of definition with them.

It is further desirable to produce a dental restoration in a short period of time in order to take good advantage of the dental laboratory overhead and in order to minimize the amount of labor consumed to produce the dental restoration.

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Dental labs are not typically well-funded establishments. Therefore, in order to keep costs as low as possible it is highly desirable to have a suitable procedure for forming dental restorations using equipment that is relatively inexpensive. While the procedure described above satisfies this requirement, the DICOR procedure that will be described later does not.

As discussed above, there are several processes in the state of the art for the manufacture of dental restorations from glass-ceramic materials. A recent addition to the state of the art is the DICOR procedure sold by Dentsply International, Inc., of York, Pennsylvania. In this procedure, a dental restoration is formed by centrifugal casting of a fused glass-ceramic material. This procedure is further described in US Patent No. 4,431,420, issued February 14, 1984 and in related patents. Centrifugal casting has been widely used in metal casting mainly by lost wax casting process. Furthermore, this procedure has been considered for hundreds of years as a successful procedure to be used in conjunction with metals. This success stems from the fact that molten metals have very low viscosity and high density in the molten state, and therefore perform very well in centrifugal casting processes. This means that due to the fact that molten metals have a high density and a very low viscosity in the molten state, centrifugal force is adequate for the purpose of injecting molten metal into a preformed mold cavity. In an attempt to produce dental restorations that have high definition, the aforementioned DICOR procedure uses centrifugal force to form the desired dental restorations from a fused glass-ceramic material. Molten glass-ceramic materials have a much higher viscosity and a much lower density compared to molten metals. For this reason, it is not possible to consistently introduce a molten glass-ceramic material into a mold only by centrifugal force in order to produce a satisfactory dental restoration. This means that a molten glass-ceramic material cannot be centrifugally driven into a mold cavity with sufficient force to always obtain the required definition that is necessary to form a satisfactory dental restoration. One skilled in the art is well aware that in order to obtain a satisfactory dental restoration, excellent definition must be achieved in order to recreate the desired margins that are necessary for the correct fit of a dental restoration in the human mouth.

Furthermore, the DICOR procedure is deficient in terms of the coloration of the glass-ceramic material used. The resulting DICOR dental restoration had an undesirable white color, and must be enameled in order to produce a satisfactory human coloration. As a result, the staining is only on the surface of the dental restoration. If an adjustment by grinding is necessary in the final installation of the restoration in the human mouth, the enamel is removed by said operation, thereby exposing the whitish base that contrasts with the enamel. This contrast is very unsatisfactory from an aesthetic point of view.

In contrast to this deficiency, the restoration of the present application is adapted to use glass-ceramic materials in which the coloration of the resulting dental restoration approximates the coloration of the human tooth throughout. Therefore, if grinding is required on the final socket, no contrast is observed between the surface of the dental restoration and the underlying base.

Undesirable contrast can also occur as a result of normal wear in which, as a result of the rubbing action of one tooth against another, the enamel is worn away. This is not a problem in the case of the present invention either, since the preferred glass-ceramic material has a uniform natural coloration throughout. It should be noted that the restoration of the present invention can be glazed to achieve the exact desired shade.

In contrast to the prior art methods discussed above, the method of the present invention can utilize a mechanically applied positive force in order to inject the fused dental glass-ceramic material into the cavity of the preformed mold.

For a dental glass-ceramic material to be satisfactory for use in the formation of dental restorations, the material must incorporate many or all of the following properties:

1. It must be inert and non-toxic in an oral environment.

two. It must have sufficient structural integrity to resist chewing forces, and it must generally have a MOR (MOR = modulus of rupture = unit flexural load at break) over 3 points of at least 30,000 psi (psi = pounds / inch).²).

3. It should be capable of being shaped into shapes that are compatible with human anatomy using simple equipment.

Four. It should have aesthetic qualities (a coloration similar to that of human teeth with a slightly translucent appearance) that are compatible with human teeth, and therefore should be monolithic or enamelable.

ES 2 235 698 T3

5. Furthermore, the glass-ceramic material should not absorb moisture or stain, and should be resistant to stress corrosion.

6. Similarly, the glass-ceramic material should have wear characteristics that are similar to those of natural human teeth, and should be compatible with other dental materials.

7. The glass-ceramic material must also have dimensional stability, and must withstand thermal shock during processing, and in particular it must have dimensional stability during subsequent heat treatment processes in which recrystallization is carried out.

8. Furthermore, from the point of view of thermal expansion, the glass-ceramic material must be compatible with metals, coloring materials, enamels, etc. that are conventionally used to form dental restorations.

9. In order to create an aesthetically pleasing dental restoration, it may be necessary to alter the final dental restoration to give it the exact shape and shade desired. In order to effect these alterations, the dental restoration must be heated to a temperature of approximately 950 ° C for each operation. Accordingly, a satisfactory glass-ceramic material should be capable of withstanding multiple heating cycles up to a temperature of about 950 ° C.

10. A suitable glass-ceramic material must be able to preserve its structural integrity during heat treatment.

eleven. In summary, a suitable glass-ceramic material should have:

A. A coefficient of thermal expansion (CTE) of 5 to 145 x 10 ⁷/ ° C

B. A translucency of 2.5 to 4.0 on a visibility scale of 0 (transparent) to 5 (opaque), and overall beauty.

C. A MOR (MOR = modulus of rupture = unit flexural breaking load) of at least 30 KSI (KSI = kilopounds / inch²)

D. The ability to be heat treated at a temperature of 925-950 ° C

E. Structural integrity during heat treatment

F. Fusibility and formability

G. Chemical durability in an oral environment.

The present invention includes glass-ceramic materials that satisfy the criteria listed above.

Brief presentation of the invention

According to the present invention, a dental restoration is provided from glass-ceramic materials that essentially has the following constituents (in percentages by weight), the percentages of which add up to approximately 100%:

<td>Li2O</td><td> 8 -</td><td> 15</td>

<td>^{To the}2^OR3</td><td> 1,5 -</td><td> 5,0</td>

<td>SiO2</td><td> 60 -</td><td> 85</td>

<td>Na2O</td><td> 0-</td><td> 2</td>

<td>K2O</td><td> 0-</td><td> 2</td>

<td>P2O₅</td><td> 1,5 -</td><td> 5</td>

<td>ZrO2</td><td> 0-</td><td> 3</td>

<td>CaO</td><td> 0-</td><td> 1</td>

BaO and / or SrO and / or La₂OR₃ 0 - 12 (total proportion)

Coloring oxides 0 - 5

In preferred embodiments, the following constituents are present in glass-ceramic materials in the following proportions (in percentages by weight), the percentages of which add up to approximately 100%:

ES 2 235 698 T3

<td>Li2O</td><td> 10 -</td><td> 13,5</td>

<td>^{To the}2 ^OR3</td><td> 2-</td><td> 3</td>

<td>SiO2</td><td> 70 -</td><td> 84</td>

<td>Na2O</td><td> 0-</td><td> 2</td>

<td>K2O</td><td> 0-</td><td> 1</td>

<td>P2O₅</td><td> 1,5 -</td><td> 4,0</td>

<td>ZrO2</td><td> 0-</td><td> 1</td>

<td>CaO</td><td> 0-</td><td> 1</td>

<td>BaO and / or SrO and / or La₂OR₃</td><td> 0,5 -</td><td>4.0 (total proportion)</td>

<td>Coloring oxides</td><td> 0-</td><td> 5</td>

In other preferred embodiments, the following constituents are present in glass-ceramic materials in the following proportions (in percentages by weight), the percentages of which add up to approximately 100%:

<td>Li2O</td><td> 9</td><td> - 13</td>

<td>^{To the}2 ^OR3</td><td> 1,5</td><td> - 4,0</td>

<td>SiO2</td><td> 65</td><td> - 84</td>

<td>Na2O</td><td> 0</td><td> -1</td>

<td>K2O</td><td> 0</td><td> -1</td>

<td>P2O₅</td><td> 1,5</td><td> - 4,0</td>

<td>ZrO2</td><td> 0</td><td> -1</td>

<td>CaO</td><td> 0</td><td> -1</td>

<td>BaO and / or SrO and / or La2O3</td><td> 0</td><td> - 12</td>

<td>Coloring oxides</td><td> 0</td><td> -5</td>

In a particularly preferred embodiment, the following constituents are present in glass-ceramic materials in the following proportions (in percentages by weight), the percentages of which add up to approximately 100%:

Li₂OR ^{To the}2 ^OR3

SiO2

K2O

P2O₅

ZrO2

CaO

Beam

10.5

2.5

78.5 0,5 2,0 0,5 0,4 3,0

Coloring oxides, including:

TiO2 0.1

CeO 0.35

NiO2 0.02

The preferred compositions of the present invention incorporate Na2O in a range between 0.2 and 2.0 in percent by weight, K₂Or in a range between 0.5 and 2.0 in percent by weight, ZrO₂ in a range between 0.5 and 3.0 in percent by weight, CaO in a range between 0.4 and 1.0 in percent by weight, and / or a softening temperature of at least 850 ° C, and preferably about 950 ° C.

The preferred compositions of the present invention are widely advantageous in that they produce aesthetically pleasing dental restorations that are chemically inert in the mouth and have outstanding strength qualities. Furthermore, such compositions are advantageous in that they maintain their structural integrity even when dental restorations from these compositions are heat treated. Additionally, said dental restorations are capable of withstanding multiple heating cycles of approximately 950 ° C, and have thermal expansions compatible with existing porcelains, so that these dental restorations can be easily altered using conventional porcelain materials.

In addition, these dental restorations have an acceptable coloration after heat treatment and can be used at that stage, without additional cosmetic treatment, in the mouth. In order to enhance the aesthetic properties of the resulting dental restoration, the dental restoration can be easily altered using porcelain materials to achieve any desired effect.

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Glass-ceramic compositions are suitable for the formation of dental restorations that have a high degree of microstructural control during crystal development, thereby allowing great flexibility in the formation of said dental restorations.

Said preferred compositions are intended to maintain their structural integrity during heat treatment, so that, in particular, they do not sag or loosen out of the mold during heat treatment. Preferably, such compositions are capable of maintaining their translucency over multiple cook cycles of about 950 ° C.

Lastly, preferred compositions have excellent chemical durability and therefore will not deteriorate on exposure to fluids in the mouth.

In order that the invention may be more clearly understood, reference is made, by way of example, to the accompanying drawings, in which:

Figure 1 is a flow chart showing the steps followed in the manufacture of the preferred embodiment of this invention.

Figure 2 shows a sectional lost wax mold intended to be used in said manufacture.

Figure 3 shows a sectional structure illustrating the heating step of this procedure.

Figure 4 shows a sectional structure illustrating the initial contact of the crucible with the mold.

Figure 5 shows a sectional structure illustrating the partial sealing of the crucible against the mold.

Figure 6 shows a sectional structure illustrating the complete sealing of the crucible against the mold and the injection of the molten glass-ceramic material into the mold cavity.

Figure 7 is a sectional side view showing the combined apparatus used in such manufacture.

Figures 7a and 7b are sectional side views showing the preferred combination apparatus.

Figure 8 shows an alternative mold in section.

Figure 9 shows an alternative mold in section.

Figure 10 shows the mold of Figure 9 when it is being filled with a molten glass-ceramic material.

It should be noted that Figures 2 to 10 are schematic representations of apparatus that may be useful in this invention.

Figure 1 generally describes the entire process by which dental restorations are formed according to the present invention, by molding a glass-ceramic material. As can be seen in Figure 1, the first step is the formation of a mold that has a suitable mold cavity in it. To initiate the process by which the mold cavity is formed, the tooth or teeth of the human mouth are prepared or prepared by the dentist by procedures that are in the public domain in the state of the art. Using impressions that are obtained by the dentist, a positive wax model of the desired dental restoration is produced. This positive wax model is then placed in a mold that is commonly referred to as a ring. A semi-liquid refractory material is then poured around the positive wax pattern. Once the refractory material has settled and cured, the resulting mold is placed in an oven and heated, which causes the wax to melt and exit through a sprue that is an integral part of the mold. The finished mold is then finished. This constitutes the formation of a mold by the lost wax process.

In the second step of Figure 1, a button made of a glass-ceramic material is placed in the deformable crucible 8, as illustrated in Figure 3. The button made of glass-ceramic material constitutes a small cylinder of glass-ceramic material that usually weighs about six grams and has a diameter of approximately two cm and a thickness of approximately one cm. These glass ceramic buttons are made in a convenient way that these materials can be manufactured, sold and used. One skilled in the art will understand that in order to form the desired dental restoration a sufficient quantity of the glass-ceramic material must be used.

In the third step of Figure 1, the crucible 8 and the glass-ceramic button 7 are uniformly heated. The glass-ceramic material is heated to a temperature above its liquid temperature as will be described in more detail below. The crucible 8 deformable by subjecting to heat and pressure will also be described in greater detail later.

In this procedure the preformed mold may incorporate multiple cavities so that more than one dental restoration can be produced during one cycle of the present procedure.

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In steps four, five and six of Figure 1 the heated crucible and glass-ceramic material are moved by being brought into contact with the mold by mechanical means and in a manner that will be described in more detail in relation to the discussion of Figures 3 to 6 later.

According to steps 7 and 8 of Figure 1, the mold is cooled, and the solidified glass-ceramic casting is removed from the refractory material by mechanical means. The dental restoration is then cut away from the sprue burr, and is finished by heat treatment and polishing and / or enamelling in order to achieve the desired aesthetic effect.

Both vitreous and glass-ceramic materials can be used in the procedure to form the desired dental restoration.

For reasons of strength and aesthetics, it is preferred that a glass-ceramic material is used. When a glass-ceramic material is used, the glass-ceramic button 7 is initially placed in the crucible 8 in a glassy phase. As heat is applied to the crucible 8, the glass-ceramic material 7 is heated. As the glass-ceramic material 7 continues to heat, the crystalline formation is affected, whereby the glass-ceramic material 7 becomes a ceramic through the formation of a crystalline phase. As heating continues, the glassy matrix slowly dissolves the crystalline phase thereby causing the glass-ceramic material 7 to re-enter the glass phase. The temperature at which the crystalline phase completely dissolves in the glassy matrix is ​​defined as the liquid temperature of the glass-ceramic material. According to this invention, it is desirable to heat the glass-ceramic material to a temperature above the liquid temperature in order to eliminate any possibility of a crystalline phase in the molten material. Furthermore, at this temperature the glass-ceramic material has a viscosity of from about log 3 to about log 4 P which is adequate to allow the molten glass-ceramic material to be easily injected into the cavity 5 of the mold. Viscosity at this temperature is defined as the range of working viscosities.

Throughout this application, the viscosity of the melted glass-ceramic materials and the softening crucible will be defined as the log of the respective viscosity in poises. In addition, the poise unit will be abbreviated with a P. For example, if the viscosity of a molten glass-ceramic material is 10⁴ poises, the viscosity will be indicated as log 4P.

While Figure 1 roughly illustrates the process for fabricating dental restorations according to the present invention, the individual steps that are illustrated in Figure 1 are further defined in the description of Figures 2 to 10.

In Figure 2 it can be seen that the mold 4 has been formed by putting a refractory material 10 in the ring

12. Before placing the refractory material 10 in the ring 12, the ring 12 is positioned around the wax model 14, the upper end of which is conformed to the shape of the desired dental restoration 16. The wax model 14 is only illustrated in shaped like a profile, since Figure 2 illustrates a finished mold 4 after the wax model 14 has been melted away.

The process according to which the mold 4 is formed is in the public domain in the state of the art, and has been used for centuries to form lost wax molds intended to be used in metal casting manufacturing processes. As indicated above in the preparation of mold 4, the wax model 14 is positioned in the ring 12, and the refractory slurry 10 is then slowly poured into the ring 12 usually with the aid of vibratory techniques to ensure that the refractory material 10 completely fills the ring 12 and in particular completely surrounds the wax model 14. These procedures are also in the public domain in the state of the art.

Figures 3, 4, 5 and 6 show the general procedure for manufacturing dental restorations according to the present invention in a schematic way.

With reference to Figure 3, it can be seen in it that the mold 4 having the cavity 14 is positioned in the vicinity of the crucible 8. A glass-ceramic material 7 is positioned in the crucible 8, the details of which will be described herein. The crucible 8 is furthermore located on a ceramic base 21 which is located on the piston 22, whereby the crucible 8 can be displaced relative to the mold 4. An electric heating element 24 is further provided by means of which heat can be applied to the crucible 8. Details of the heating of the glass-ceramic material 7 will be discussed later herein.

During the heating of the crucible 8 the glass-ceramic material 7 is converted from a solid state to a liquid state, and the crucible 8 is converted from a brittle solid state to a plastic state in which it is deformable under heat and pressure. Once the glass-ceramic material 7 reaches the desired range of working viscosities, the piston 22 is actuated as illustrated in Figure 4, thereby causing the crucible 8 to move up and into contact with the lower end of the mold. 4. Actuation of piston 22 is effected by a power source that is not illustrated.

As can be seen in Figure 5, as the piston 22 continues to move upwards, the crucible 8 continues to deform against the mold 4 causing the upper end of the crucible 8 to form a hermetic seal against the mold.

ES 2 235 698 T3 mold 4 on contact surface 28. It can further be seen that molten glass-ceramic material 7 has begun to flow into mold cavity 14.

Referring to Figure 6, as the piston 22 continues to move, the deformation of the crucible 8 against the mold 4 is completed, and furthermore the cavity 14 is completely filled with glass-ceramic material 7 as a result of the pressure applied by the piston 22.

Following the operations that are illustrated in Figures 3 to 6, the mold 4 is then cooled, and the desired dental restoration is removed from the refractory material 10. Once the dental restoration has been removed from the refractory material 10, the restoration dental is cut away from the sprue burr, and is then heat treated and finished by polishing and enamelling in order to achieve the desired aesthetic effect.

Furthermore, after dental restoration 26 has been formed it is heat treated such that its strength and other properties are enhanced by the formation of crystals in a glassy matrix. Details of the heat treatment are described below.

Figure 7 illustrates an apparatus 32 that can be used to execute the combined process that is illustrated in the diagram of the cycle of operations of the manufacturing process of Figure 1. This apparatus generally comprises the support frame 30, the heat source 33, the mold clamping means 34, and a piston 36. The support frame 30 generally comprises the outer frame of the apparatus 32.

The mold clamping means 34 comprise a bar 50 into which the mold clamping press 35 is screwed. As can be seen, the bar 50 allows the mold 4 to be fixed to the support bar 44. The support bar 44 further incorporates an opening 56 that is slightly narrower than the diameter of the mold 4 and slightly larger than the diameter of the crucible. 8. By actuation of the piston 36, the crucible 8 is moved upward to come into contact with the mold 4 in a manner that is similar to that previously described in conjunction with Figures 4, 5 and 6. The Figure 7 further incorporates a heat source 33, which in the illustrated embodiment comprises an electrical resistance heating element 37. In the preferred embodiment, the heating element is molybdenum disilicide. The heat source 33 is controlled by a power control source 58.

As illustrated in Figures 3 and 7, an electrical resistance heater can be used to effect the heating of the crucible 8 and consequently of the glass-ceramic material 7. In addition to the electrical resistance heating that is illustrated, the heating can be effected by heating by induction, gas torch heating, or by any other appropriate means.

The apparatus may further incorporate rotating means, not illustrated, by which the piston 36 may be rotated during the heating process in order to effect a more uniform heating of the crucible 8 and the glass-ceramic material contained therein. The rotating means can be an electric, pneumatic or hydraulic motor. The piston 36 is further provided with means for effecting its upward movement, which means are in the preferred embodiment a pneumatic cylinder 39.

Referring further to Figure 7, it can be seen therein that the apparatus 32 incorporates a plurality of structural insulation elements 41, 43, 45, 47 and 49 that support and contain the heating element 37 and contain the heat that is generated during the operation of the element 37. These structural insulation elements are formed from ceramic fiber cardboard.

It can likewise be seen that the support bar 44 incorporates an opening 56 having a notched section 55. The notched section 55 is advantageous in that when the crucible 8 is deformed against the mold 4 in the constriction of the notched portion 55 it is prevented from the deformed upper end part of the crucible 8 moves downwards, whereby the molten glass-ceramic material is efficiently injected into the preformed cavity 14 made in the mold 4. This means that due to the fact that the upper end part of the crucible 8 is made to solidify in the vicinity of the notched part 55, the downward movement of the molten glass-ceramic material is prevented, thereby causing the glass-ceramic material to be injected into the interior. of the mold cavity 14.

Figures 7a and 7b depict apparatus 31 preferred to be used to fabricate dental restorations in accordance with this invention. The components of the preferred apparatus 31 are for the most part identical or similar to the components of the apparatus 32 discussed hereinabove. The apparatus 31 differs from the apparatus 32 mainly in that a movable arm 38 is provided in which a preheated mold 4 can be brought into position for the molding process and can be positioned against the base 41 of the furnace. The movable arm 38 can be connected to a central pivot point by means of which said arm can be rotated to be put into position, or it can be laterally moved to be put into position.

Before putting the arm 38 in position, as illustrated in Figure 7a, the piston 22 is extended in order to put the crucible 8 in the heat source 33, with which the glass-ceramic material 7 can be melted. fusion, the piston 22 is withdrawn, and the movable arm 38 is rotated being put in position as illustrated in Figure 7b. In this position the training sequence can be completed as illustrated in Figures 2 to 6.

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In relation to the apparatuses 31 and 32, one skilled in the art will understand that the crucible 8 can be positioned on the ceramic base 21 either manually or by automatic means.

Figures 1 to 7b described above illustrate the formation of a dental restoration. In addition to being useful in the formation of essentially complete dental restorations, the composition and procedure described above can be used to form crowns on which porcelain materials can be applied to alter the dental restoration and give it the desired shade.

Metallic crowns are widely used in the state of the art. These crowns are covered with layers of porcelain materials that are applied to the metal crowns in order to form a composite dental restoration comprising a metal base and a porcelain exterior. Composite frameworks are advantageous in that metal crowning significantly increases the strength of the resulting dental restoration. Metallic crowns are disadvantageous in that they are opaque and have a color that contrasts with the color of a natural tooth, and in addition they pose toxicity problems in some cases. The application of the present invention in a fully glass-ceramic dental restoration is advantageous in that the crown is essentially the same color as the natural tooth, and in particular it is essentially the same color as that of the porcelain from which the tooth is formed. outer part of the dental restoration. Furthermore, the all-ceramic structure is advantageous in that it eliminates the problems that occur in certain patients who are allergic to certain metals. With this procedure, metal-free crowns and bridges are achieved with excellent resistance and excellent aesthetic properties. The excellent aesthetic properties derive from the fact that these glass ceramic toppings can be used as a base on which a variety of different porcelains can be applied to the fire in order to achieve the most exquisite coloration and the most exquisite aesthetic properties.

As indicated above, both glass and glass-ceramic materials can be used in the described process. In Tables I to IV the glass-ceramic compositions that are preferred to be used according to the invention are listed. The amounts of all the components are indicated in Tables I to IV in percentages by weight.

Any suitable glass-ceramic materials can be used in the present invention. As indicated in Tables I to IV, the glass-ceramic materials that are preferred for use in this invention are lithium disilicate glass-ceramic materials. In these materials the Li₂O 2 (SiO₂) constitutes the crystalline phase of the heat-treated glass-ceramic material. Lithium disilicate glass-ceramic materials are particularly suitable for use in the invention in that they are non-toxic, resist thermal shock, have excellent strength, are resistant to corrosion, and produce dental restorations that approximate human staining. and they are translucent and aesthetically pleasing. Furthermore, lithium disilicate glass-ceramic materials are advantageous in that they retain their structural integrity during heat treatment, not collapsing or sagging during proper heat treatment.

Other lithium disilicate glass-ceramic materials that can be used in this invention are described in US Patent 5,219,799, issued June 15, 1993.

In lithium disilicate glass-ceramic materials, P₂OR₅ as a nucleating agent. Other nucleating agents are TiO2 and ZrO2.

The glass-ceramic compositions that may be useful in this invention are as indicated in Table

I. The percentages in Table I and the other tables that appear herein are percentages by weight.

TABLE I

<td>Li2O</td><td> 8</td><td> - 15</td>

<td>^{To the}2 ^OR3</td><td> 1,5</td><td> - 5,0</td>

<td>SiO2</td><td> 60</td><td> - 85</td>

<td>Na2O</td><td> 0</td><td> -2</td>

<td>K2O</td><td> 0</td><td> -2</td>

<td>P2O₅</td><td> 1,5</td><td> -5</td>

<td>ZrO2</td><td> 0</td><td> -3</td>

<td>CaO</td><td> 0</td><td> -1</td>

<td>BaO + SrO + LaO</td><td> 0</td><td> - 12</td>

<td>Coloring Oxides</td><td> 0</td><td> -5</td>

More specific glass-ceramic compositions that may be useful in the invention are as indicated in Table II. In particular, the compositions of Table II are useful in conjunction with high or low melting point porcelains that can be used to alter, tint or glaze the dental restorations of this invention.

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TABLE II

<td>Li2O</td><td> 10 -</td><td> 13,5</td>

<td>^{To the}2^OR2</td><td> 2-</td><td> 3</td>

<td>SiO2</td><td> 70 -</td><td> 84</td>

<td>K2O</td><td> 0-</td><td> 1</td>

<td>P2O₅</td><td> 1,5 -</td><td> 4</td>

<td>ZrO2</td><td> 0-</td><td> 1</td>

<td>BaO + SrO + LaO</td><td> 0,5 -</td><td> 4</td>

<td>CaO</td><td> 0-</td><td> 1</td>

<td>Coloring Oxides</td><td> 0-</td><td> 5</td>

In some cases it is desirable to form a dental restoration that can be altered or enameled with a low melting point porcelain. For the purposes of this application, a low melting point porcelain is defined as a porcelain that melts at a temperature of about 700 ° C.

Specific glass-ceramic compositions that are useful in conjunction with low melting point porcelains are as indicated in Table III.

TABLE III

Li2O ^{To the}2^OR3

SiO2

Na2O

K2O

P2O₅

ZrO2

BaO + SrO + LaO CaO

Coloring Oxides

- 13

1,5 - 4

- 84

0-1 0-1 1,5 - 4 0-1 0 - 12 0-1 0-5

Specific glass-ceramic compositions that may be useful in this invention are as indicated in Table IV.

(Table goes to next page)

ES 2 235 698 T3

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ES 2 235 698 T3

With respect to a general range of compositions that are preferred to be used in conjunction with this invention, the glass-ceramic compositions that are defined in Table II are preferred.

The most preferred glass-ceramic composition to be used in accordance with this invention is the glass-ceramic composition which is defined as composition 18 of Table IV.

The glass-ceramic compositions defined by the above Tables I to IV are particularly advantageous compared to those of the state of the art in that:

1. They are stronger than the glass-ceramic compositions of the state of the art.

two. Compositions incorporating barium and cerium oxides fluoresce in ultraviolet light.

3. The coefficients of expansion of many of these glass-ceramic compositions are compatible with the coefficients of expansion of existing alteration porcelain materials.

Four. They retain their structural integrity at higher temperatures compared to the state of the art, thereby allowing alterations to be carried out at higher temperatures.

As listed in Tables I to IV, staining oxides can be added to the glass-ceramic material in order to achieve the desired staining of the glass-ceramic dental restoration.

Coloring oxides that are suitable for use in glass-ceramic compositions that can be used in this invention, some of which are illustrated in Tables I to IV, are SnO₂, Mno, CeO, Fe₂OR₃, Neither₂O, V₂OR₃, Cr₂OR₃, Uncle₂, etc. These coloring oxides can be used alone or in combination.

Following the formation of a glass-ceramic restoration according to this invention, the resulting dental restoration is heat treated in order to effect crystal formation on the dental restoration. This crystal formation is generally referred to as heat treatment, and it serves to improve the physical and aesthetic properties of the dental restoration. A heat treatment sequence that is suitable for use with the glass-ceramic compositions of Tables I to IV is a sequence such as that indicated in Table V below.

For the glassy compositions that can be used in this invention, the best nucleation temperatures are those that are about 25 ° to 50 ° C higher than the upper anneal point of the glass-ceramic material. It has also been determined that a slow increase in temperature from a temperature just above the upper anneal point to a temperature about 50 ° C higher produces the best results for achieving maximum nucleation. It is also well known that the temperature must then be increased to a higher temperature to carry out the crystallization, this temperature being dependent on the composition of the concrete glass-ceramic material that is used.

If the heating sequence in the heat treatment stage is incorrect or improperly controlled, the dental restoration may sag or deform. One skilled in the art will understand that a heat treatment procedure must be developed that is optimal for each specific glass-ceramic material in order to allow the dental restoration to retain its structural integrity during the heat treatment process.

In the preferred embodiment, the heat treatment cycle is such that in the crystalline phase the glass-ceramic material incorporates a large number of fine crystals that are uniformly dispersed throughout the glass matrix. It has been found that when the crystalline phase is very fine and evenly dispersed, a maximum strength dental restoration is obtained as a result. Furthermore, a fine crystalline structure tends to produce translucent dental restorations.

From the foregoing it is obvious that dental restorations produced according to this invention can be heat treated after the dental restoration has been removed from the refractory material and after the burr has been cut away from the sprue.

According to an alternative preferred embodiment of this invention, the heat treatment of the dental restoration can be carried out while the dental restoration is still in the refractory material. This means that the heat treatment can be carried out while the dental restoration is still in and surrounded by the refractory material.

According to yet another embodiment, the dental restoration can be removed from the refractory material in which it was formed, and can be finished or partially finished before carrying out the heat treatment. For heat treatment, the material is then coated again with a coating material that supports the heat treatment process. After the dental restoration has been recoated with a veneering material, the heat treatment is carried out according to the procedure described above.

ES 2 235 698 T3

As long as the dental restoration is heat treated while being coated with a veneering material, shrinkage of the dental restoration is minimized, if not removed.

In heat treatment, and in particular in the formation of a crystalline phase, shrinkage of the dental restoration takes place. This shrinkage can be as high as 3 percent. Naturally, this shrinkage is undesirable since it adversely affects the fit of the dental restoration in the patient's mouth.

As a way of overcoming the problem of shrinkage, it is within the scope of this invention to accommodate the wax pattern in a refractory material that expands as it hardens and is heated. This means that the refractory material expands as it hardens, thus producing an oversized mold cavity. Naturally, this oversized mold cavity produces an oversized dental restoration. This oversized dental restoration is then shrunk back to the correct size during the heat treatment process.

For example, since the glass-ceramic material shrinks approximately 3 percent during the heat treatment process, the original wax pattern can be surrounded by the refractory material using a refractory material that expands approximately 3 percent upon hardening and being heated. Using this procedure, a dental restoration is obtained that is 3 percent oversized. This oversized dental restoration is then heat treated, which shrinks approximately 3 percent, thus becoming a finished dental restoration of the correct size.

In order to achieve a correct fit, if the restoration must be heat-treated after being removed from the refractory material, a veneering material must be used that, when hardened and heated, expands approximately 3 percent. Coating materials that are useful with metals are not particularly suitable for use in the invention, since they swell only about 1.75 percent. Coating materials that expand approximately 3 percent when hardened and heated and thereby allow this type of procedure to be performed are manufactured by the Whipmix Corporation of Louville, Ky, and are sold under the designation GIJM 3-23 -94; 1

The heat treatment process that is preferred to be used with the glass-ceramic compositions of Tables I to IV is as indicated in Table V

TABLE V

Heat the restoration up to 500 ° C

Increase or standardize temp. at 500-600 ° C for 2-6 hours

Increase temp. at 600-925 ° C for 2-3 hours

Standardize temp. at 950 ° C for 1-2 hours

Cool down to room temperature

After heat treatment, the resulting dental restoration can be subjected to additional finishing operations. This finish may include a step in which the dental restoration is altered with one or more porcelains in order to achieve the exact shape, tone and shade desired. For those glass-ceramic materials from Tables I to IV that have a CTE (Coefficient of Thermal Expansion) from about 135 to about 145 at the solidification point temperature, the CTE of the alteration porcelain material is desired to be about 125 to about 135 and always less than the CTE of the glass-ceramic material. The procedure by which the CTE is measured is defined in the description of the Examples hereinafter.

The deformable crucible 8 is a decisive part of the apparatus used. The crucible has in its preferred embodiment a circular base, and is therefore generally cylindrical. However, one skilled in the art will understand that the crucible may have configurations other than circular. The crucible is formed by heat sintering a particulate mixture of components such as fused silica, aluminum oxide, zirconium oxide, magnesium oxide with a glass such as borosilicate glass, lime glass and caustic soda, bottle glass, glass of windows, etc., clay, or other materials that those skilled in the art of crucibles can use to form a crucible that is suitable for use with a glass-ceramic material. In a broad sense, the crucible is formed from a mixture of materials such that at the temperature at which the glass-ceramic material is in the range of working viscosities of approximately log 3 to log 4 P the crucible has a viscosity of approximately log 5 to log 7 P.

The crucibles to be used in this process are formed by slip molding. The formation of crucibles by slip casting is well known to those skilled in the art, and is described in greater detail in the Examples below.

In the above description, the compositions that are used to form crucibles that are useful in this process can use a wide range of materials. While many glasses can be used to form

ES 2 235 698 T3 crucibles that are useful in the process, due to their toxicity, glasses containing heavy metals such as lead, cadmium, etc. should not be used.

An alternative method of forming crucibles for use in this process is pressing the powder material followed by sintering.

The composition from which the crucible is formed contains materials that are such that said crucible will be deformable by subjecting it to heat and pressure at the desired temperature, that is, at a working temperature of the glass-ceramic material corresponding to approximately log 3 to log 4. P. The properties of deformation due to heat and pressure of the crucibles that are used in this procedure are in contrast to the crucibles of the state of the art, which are designed to be rigid at the working temperature of the glass-ceramic material that is contained in the same.

In the alternative structure that is illustrated in Figures 8, 9 and 10, the sealing of the deformed crucible against the mold is favored. In the illustrated structure, mold 64 incorporates a circular depression 66 having vertical walls 68 and 70 with which crucible 8 can form a seal. The vertical walls 72 and 74 of the mold 65 may further incorporate a plurality of annular grooves 76. As further illustrated in Figure 10, the sealing of the crucible 8 against the mold 65 is aided by deformation of the upper end portion of the crucible 8 into the annular grooves 76 during the deformation process.

Examples

The present invention is illustrated by the following Examples, although these examples should not be construed as limiting the invention in any way.

Dental restorations were prepared according to the examples given below. In these examples, wax models of a tooth were prepared. A sprue burr was then attached to the wax model. The wax pattern with the sprue burr attached to it was then placed in a liner ring. A refractory material was then prepared by mixing 90 grams of Kerr's Thermovest with 17 ml of a mixture of 2 parts of liquid Thermovest with 1 part of water. The resulting mixture was then mixed to a uniform consistency. The mixed refractory material was then vibrated inside the investment ring and around the wax pattern. The mold was allowed to dry and harden overnight. The lining ring was then placed in a wax removal oven at room temperature, and the temperature was increased to 600 ° C, at which time the wax pattern was removed and thus removed from the refractory material.

The crucibles used in these examples were prepared by slip casting. In this procedure, a plaster of paris female mold was prepared by mixing 1247.4 grams of plaster of paris with 946 ml of water until a uniform consistency was obtained. The resulting mold was allowed to harden for 36 hours. A slurry of a mixture of the particulate crucible formulation identified in the following examples was then placed in the preformed plaster of paris mold. The uncooked crucible was removed from the mold and fired in an oven for 15 minutes at 1100 ° C to sinter the crucible leaving it in a hardened and more durable shape.

The slurry that was used to form the crucible was formed by mixing 1 pound of particulate material with 160 ml of water.

Due to the hydroscopic nature of the plaster of paris mold, the slurry of the particulate formulation from the crucible coagulates in the plaster of paris mold. Once the desired crucible wall thickness was reached, the remainder of the slurry was poured out of the mold, resulting in an uncooked crucible structure that was allowed to dry.

In the examples listed and in this application, the coefficient of thermal expansion (CTE) was measured within a temperature variation ranging from room temperature to 250 ° C, and said coefficient of thermal expansion is indicated in units of x 10 ⁷/ ° C.

The translucency of the resulting dental restoration was measured by visual inspection, giving it a value from 0 to 5, considering the value of 0 corresponding to a perfectly transparent dental restoration, and considering the value of 5 corresponding to an opaque dental restoration.

In the Examples that follow, in order to inject the vitreous material and the melted glass-ceramic material into the mold, a pressure of 206.8 KPa (30 PSI) was used, with the exception of Examples 26 and 27, in which was used a pressure of approximately 345 KPa (50 PSI).

The cited sequence of heat treatment for all Examples, except Examples 26 and 27, is according to Table IV above.

In the following Examples, glass-ceramic cylindrical test tubes were formed together with colored test tubes for the measurement of modulus of rupture (MOR) and thermal expansion (CTE). These cylindrical specimens and

ES 2 235 698 T3 colored specimens were subjected to the heat treatment process of Table VI, whereby the glasses were crystallized in situ, becoming glass-ceramic materials. The cylindrical specimens were 0.3 cm x 3.18 cm (0.120 "x 1.25"). The Examples also indicate the visual appearance of each glass-ceramic test piece and the values ​​of the different properties that the glass-ceramic test piece presents, such as the coefficient of linear thermal expansion (CTE), indicated in x 10^-7/ ° C, and the modulus of rupture (MOR), indicated in KSI (thousands of pounds per square inch) and determined according to measurement techniques that are conventionally used in the industry. Values ​​in KSI can be converted to their metric equivalents in MPa by dividing KSI by 0.145.

The components used in these Examples are as follows:

Thermovest and liquid Thermovest sold by Kerr Manufacturing Co. Romulus, Mi. 48174.

Fused Silica 3I sold by the Harbison Walker Refactories Division of Indresco Inc., Pittsburg, Pa. 15223.

SP921 TF (borosilicate glass) sold by Specialty Glass Inc. of Oldsmar, Florida, and having the following composition in percentages by weight.

TABLE VI

<td>SiO2</td><td> 78</td>

<td>B2O3</td><td> 15</td>

<td>^{To the}2 ^OR3</td><td> 2,5</td>

<td>Na2O</td><td> 4,5</td>

Example 1

An attempt was made to form a glass ceramic dental restoration according to the following procedure. A mold was prepared according to the procedure that has been described above.

Using slip casting techniques, a crucible was prepared according to the procedure described above by mixing 90.8 grams of SP921TF glass in 363.2 grams of 3I fused silica with 160 ml of water. After slip casting and drying, the crucible was sintered at a temperature of 1100 ° C. A glass button weighing 6 grams was then placed in the crucible, and it was preheated to a temperature of 650 ° C.

The composition of the glass-ceramic material used conforms to composition No. 1 of Table IV.

The preheated crucible and glass-ceramic material were then placed in an apparatus similar to that illustrated in Figure 7, and heated to a temperature of 1400 ° C for a period of 10 minutes. The piston was then actuated, and the crucible was brought into contact with the mold according to the general procedure illustrated in Figures 3 to 6. The crucible broke, and consequently no dental restoration was formed.

Example 2

A glass ceramic dental restoration was prepared according to the procedure outlined below. A mold was prepared according to the procedure that has been described above.

Using slip casting techniques, a crucible was prepared according to the procedure described above by mixing 136.2 grams of SP921TF glass and 317.8 grams of 3I fused silica with 160 ml of water. After slip casting and drying, the crucible was sintered at a temperature of 1100 ° C. A glass button weighing 6 grams was then placed in the crucible, and it was preheated to a temperature of 650 ° C.

The composition of the glass-ceramic material used conforms to composition No. 1 of Table IV.

The preheated crucible and glass-ceramic material were then placed in an apparatus similar to that illustrated in Figure 7, and heated to a temperature of 1400 ° C for a period of 10 minutes. The piston was then actuated, and the crucible was brought into contact with the mold according to the general procedure illustrated in Figures 3 to 6.

The dental restoration was then removed from the refractory material, cut away from the sprue burr, and subjected to heat treatment.

The resulting dental restoration had excellent definition and a MOR of 282 MPa (41 KSI), a CTE of 148, a translucency of 3.5, and a softening temperature of 975 ° C.

During the formation process, the crucible retained its structural integrity and formed an effective seal.

ES 2 235 698 T3 with the mold. Furthermore, during the heat treatment process the finished dental restoration retained its structural integrity and did not collapse or deform during heat treatment.

Additional tests were carried out in which it was determined that the crucible of this Example exhibited good performance when deforming and forming the seal at 1375 and 1425 ° C.

Example 3

A mold was prepared according to the procedure that has been described above.

Using slip casting techniques, a crucible was prepared according to the procedure described above by mixing 181.6 grams of SP921TF glass and 272.4 grams of 3I fused silica with 160 ml of water. After slip casting and drying, the crucible was sintered at a temperature of 1100 ° C. A glass button weighing 6 grams was then placed in the crucible, and it was preheated to a temperature of 650 ° C.

The preheated crucible without glass-ceramic material was then placed in an apparatus which is similar to that illustrated in Figure 7, and was heated to a temperature of 1400 ° C for a period of 10 minutes.

During the heating process, the crucible lost its structural integrity and was not able to seal with the mold. Consequently, no molding process was carried out.

Example 4

A mold was prepared according to the procedure described above.

Using slip casting techniques, a crucible was prepared according to the procedure described above by mixing 227 grams of SP921TF glass and 227 grams of 3I fused silica with 160 ml of water. After slip casting and drying, the crucible was sintered at a temperature of 1100 ° C. A glass button weighing 6 grams was then placed in the crucible, and it was preheated to a temperature of 650 ° C.

The preheated crucible and glass-ceramic material were then placed in an apparatus similar to that illustrated in Figure 7, and were heated to a temperature of 1400 ° C for a period of 10 minutes.

During the heating process, the crucible melted, and consequently it was not able to form an effective seal with the mold. Consequently, no molding process was carried out.

Example 5

A glass ceramic dental restoration was prepared according to the procedure outlined below. A mold was prepared according to the procedure described above.

Using slip casting techniques, a crucible was prepared according to the procedure described above by mixing 118 grams of SP921TF glass and 336 grams of 3I fused silica with 160 ml of water. After slip casting and drying, the crucible was sintered at a temperature of 1100 ° C. A glass button weighing 6 grams was then placed in the crucible, and it was preheated to a temperature of 650 ° C.

The composition of the glass-ceramic material used conforms to composition No. 1 of Table IV.

The preheated crucible and glass-ceramic material were then placed in an apparatus similar to that illustrated in Figure 7, and heated to a temperature of 1400 ° C for a period of 10 minutes. The piston was then actuated, and the crucible was brought into contact with the mold according to the general procedure illustrated in Figures 3 to 6.

The dental restoration was then removed from the refractory material, cut away from the sprue burr, and subjected to heat treatment.

The resulting dental restoration had excellent definition and the physical properties that are indicated in Example 2.

During the formation process, the crucible retained its structural integrity and formed an effective seal with the mold. In addition, during the heat treatment process the finished dental restoration retained its structural integrity and did not collapse or deform.

Additional tests were carried out on the crucibles having the above composition, determining that the crucible broke and was therefore not functional at 1375 ° C. Further testing demonstrated that the crucible of this example deformed and formed the seal at 1425 ° C.

ES 2 235 698 T3

Example 6

A glass ceramic dental restoration was prepared according to the procedure outlined below. A mold was prepared according to the procedure described above.

Using slip casting techniques, a crucible was prepared according to the procedure described above by mixing 127.1 grams of SP921TF glass and 336.9 grams of 3I fused silica with 160 ml of water. After slip casting and drying, the crucible was sintered at a temperature of 1100 ° C. A glass button weighing 6 grams was then placed in the crucible, and it was preheated to a temperature of 650 ° C.

The composition of the glass-ceramic material used conforms to composition No. 1 of Table IV.

The preheated crucible and glass-ceramic material were then placed in an apparatus similar to that illustrated in Figure 7, and heated to a temperature of 1400 ° C for a period of 10 minutes. The piston was then actuated, and the crucible was brought into contact with the mold according to the general procedure illustrated in Figures 3 to 6.

The dental restoration was then removed from the refractory material, cut away from the sprue burr, and subjected to heat treatment.

The resulting dental restoration had excellent definition and physical properties conforming to Example 2.

During the formation process, the crucible retained its structural integrity and formed an effective seal with the mold. In addition, during the heat treatment process the dental restoration retained its structural integrity and did not collapse or deform.

Additional tests were carried out with the crucible of this example, determining that the crucible deformed and formed a seal at both 1375 and 1425 ° C.

Example 7

A glass ceramic dental restoration was prepared according to the procedure outlined below. A mold was prepared according to the procedure described above.

Using slip casting techniques, a crucible was prepared according to the procedure described above by mixing 145.3 grams of SP921TF glass and 308.7 grams of 3I fused silica with 160 ml of water. After slip casting and drying, the crucible was sintered at a temperature of 1100 ° C. A glass button weighing 6 grams was then placed in the crucible, and it was preheated to a temperature of 650 ° C.

The composition of the glass-ceramic material used conforms to composition No. 1 of Table IV.

The preheated crucible and glass-ceramic material were then placed in an apparatus similar to that illustrated in Figure 7, and heated to a temperature of 1400 ° C for a period of 10 minutes. The piston was then actuated, and the crucible was brought into contact with the mold according to the general procedure illustrated in Figures 3 to 6.

The dental restoration was then removed from the refractory material, cut away from the sprue burr, and subjected to heat treatment.

The resulting dental restoration had excellent definition and the physical properties that are indicated in Example 2.

During the formation process, the crucible retained its structural integrity and formed an effective seal with the mold. In addition, during the heat treatment process the dental restoration retained its structural integrity and did not collapse or deform. Additional tests were carried out with the crucible of this Example, determining that the crucible operated at 1375 ° C. However, at 1425 ° C the crucible collapsed, and therefore could not be used in the process of this invention.

Example 8

A glass ceramic dental restoration was prepared according to the procedure outlined below. A mold was prepared according to the procedure described above.

Using slip molding techniques, a crucible was prepared according to the procedure that has been described above in connection with Example 2 and with the description that has been given above in connection with that example. A glass button weighing 6 grams was then placed in the crucible, and it was preheated to a temperature of 650 ° C.

ES 2 235 698 T3

The composition of the glass-ceramic material used is in accordance with composition No. 2 of Table IV.

The preheated crucible and glass-ceramic material were then placed in an apparatus similar to that illustrated in Figure 7, and heated to a temperature of 1400 ° C for a period of 10 minutes. The piston was then actuated, and the crucible was brought into contact with the mold according to the general procedure illustrated in Figures 3 to 6.

The dental restoration was then removed from the refractory material, cut away from the sprue burr, and subjected to heat treatment.

The resulting specimens and dental restoration had excellent definition with a MOR of 322 MPa (46.7 KSI), a CTE of 138, a translucency of 2.75, and a softening temperature of 975 ° C.

During the formation process, the crucible retained its structural integrity and formed an effective seal with the mold. Furthermore, during the heat treatment process the finished dental restoration retained its structural integrity and did not collapse or deform during heat treatment.

Example 9

A glass ceramic dental restoration was prepared according to the procedure outlined below. A mold was prepared according to the procedure described above.

Using slip casting techniques, a crucible was prepared according to the procedure described above in connection with Example 2 and according to the description given above in connection with that example. A glass button weighing 6 grams was then placed in the crucible, and it was preheated to a temperature of 650 ° C.

The composition of the glass-ceramic material used conforms to composition No. 3 of Table IV.

The preheated crucible and glass-ceramic material were then placed in an apparatus similar to that illustrated in Figure 7, and heated to a temperature of 1400 ° C for a period of 10 minutes. The piston was then actuated, and the crucible was brought into contact with the mold according to the general procedure illustrated in Figures 3 to 6.

The dental restoration was then removed from the refractory material, cut away from the sprue burr, and subjected to heat treatment.

The resulting specimens and dental restoration had excellent definition with a MOR of 296 MPa (43 KSI), a CTE of 141, a translucency of 3.0, and a softening temperature of 975 ° C.

During the formation process, the crucible retained its structural integrity and formed an effective seal with the mold. Furthermore, during the heat treatment process the finished dental restoration retained its structural integrity and did not collapse or deform during heat treatment.

Example 10

A glass ceramic dental restoration was prepared according to the procedure outlined below. A mold was prepared according to the procedure described above.

Using slip molding techniques, a crucible was prepared according to the procedure that has been described above in connection with Example 2 and according to the description that has been given above in connection with said example. A glass button weighing 6 grams was then placed in the crucible, and it was preheated to a temperature of 650 ° C.

The composition of the glass-ceramic material used conforms to composition No. 4 of Table IV.

The preheated crucible and glass-ceramic material were then placed in an apparatus similar to that illustrated in Figure 7, and heated to a temperature of 1400 ° C for a period of 10 minutes. The piston was then actuated, and the crucible was brought into contact with the mold according to the general procedure illustrated in Figures 3 to 6.

The dental restoration was then removed from the refractory material, cut away from the sprue burr, and subjected to heat treatment.

The resulting specimens and dental restoration had excellent definition with a MOR of 331 MPa (48 KSI), a CTE of 133, a translucency of 2.5, and a softening temperature of 975 ° C.

During the formation process, the crucible retained its structural integrity and formed an effective seal.

ES 2 235 698 T3 with the mold. Furthermore, during the heat treatment process the finished dental restoration retained its structural integrity and did not collapse or deform during heat treatment.

Example 11

A glass ceramic dental restoration was prepared according to the procedure outlined below. A mold was prepared according to the procedure described above.

Using slip molding techniques, a crucible was prepared according to the procedure and composition that have been described above in connection with Example 2. A glass button weighing 6 grams was then placed in the crucible, and was preheated to a temperature 650 ° C.

The composition of the glass-ceramic material used conforms to composition No. 5 of Table IV.

The preheated crucible and glass-ceramic material were then placed in an apparatus similar to that illustrated in Figure 7, and heated to a temperature of 1400 ° C for a period of 10 minutes. The piston was then actuated, and the crucible was brought into contact with the mold according to the general procedure illustrated in Figures 3 to 6.

The dental restoration was then heat treated.

The resulting specimens and dental restoration had excellent definition and a MOR of 290 MPa (42 KSI), a CTE of 140, a translucency of 2.5, and a softening temperature of 975 ° C.

During the formation process, the crucible retained its structural integrity and formed an effective seal with the mold. Furthermore, during the heat treatment process the finished dental restoration retained its structural integrity and did not collapse or deform during heat treatment.

Example 12

A glass ceramic dental restoration was prepared according to the procedure outlined below. A mold was prepared according to the procedure described above.

Using slip molding techniques, a crucible was prepared according to the procedure and composition previously described in connection with Example 6. A glass button weighing 6 grams was then placed in the crucible, and was preheated to a temperature 650 ° C.

The composition of the glass-ceramic material used conforms to composition No. 6 of Table IV.

The preheated crucible and glass-ceramic material were then placed in an apparatus similar to that illustrated in Figure 7, and heated to a temperature of 1400 ° C for a period of 10 minutes. The piston was then actuated, and the crucible was brought into contact with the mold according to the general procedure illustrated in Figures 3 to 6.

The dental restoration was then heat treated.

The resulting specimens and dental restoration had excellent definition with a MOR of 286 MPa (41.5 KSI), a CTE of 162, a translucency of 4, and a softening temperature of 950 ° C.

During the formation process, the crucible retained its structural integrity and formed an effective seal with the mold. Furthermore, during the heat treatment process the finished dental restoration retained its structural integrity and did not collapse or deform during heat treatment.

Example 13

A glass ceramic dental restoration was prepared according to the procedure outlined below. A mold was prepared according to the procedure described above.

Using slip molding techniques, a crucible was prepared according to the procedure and composition previously described in connection with Example 6. A glass button weighing 6 grams was then placed in the crucible, and was preheated to a temperature 650 ° C.

The composition of the glass-ceramic material conforms to composition No. 7 of Table IV.

The preheated crucible and glass-ceramic material were then placed in an apparatus similar to that illustrated in Figure 7, and heated to a temperature of 1400 ° C for a period of 10 minutes. The piston was then actuated, and the crucible was brought into contact with the mold according to the general procedure illustrated in Figures 3 to 6.

ES 2 235 698 T3

The dental restoration was then removed from the refractory material, cut away from the sprue burr, and subjected to heat treatment.

The resulting specimens and dental restoration had excellent definition and a MOR of 369 MPa (53.5 KSI), a CTE of 136, a translucency of 4.0, and a softening temperature of 950 ° C.

During the formation process, the crucible retained its structural integrity and formed an effective seal with the mold. Furthermore, during the heat treatment process the finished dental restoration retained its structural integrity and did not collapse or deform during heat treatment.

Example 14

A glass ceramic dental restoration was prepared according to the procedure outlined below. A mold was prepared according to the procedure described above.

Using slip molding techniques, a crucible was prepared according to the procedure and composition that have been described above in connection with Example 2. A glass button weighing 6 grams was then placed in the crucible, and was preheated to a temperature 650 ° C.

The glass-ceramic material used was Di-Cor, which is sold by the Densply Corporation and which is as described above. Di-Cor is thought to be a fluorinated mica glass-ceramic material.

The preheated crucible and glass-ceramic material were then placed in an apparatus similar to that illustrated in Figure 7, and heated to a temperature of 1400 ° C for a period of 10 minutes. The piston was then actuated, and the crucible was brought into contact with the mold according to the general procedure illustrated in Figures 3 to 6.

The dental restoration was then heat treated in the refractory material.

While the glass-ceramic material correctly filled the mold, the resulting dental restoration broke as a result of shrinkage during the heat treatment process. This failure is thought to be a consequence of the fact that the forming refractory material was not suitable for use in the heat treatment sequence.

Example 15

A glass ceramic dental restoration was prepared according to the procedure outlined below. A mold was prepared according to the procedure described above.

Using slip molding techniques, a crucible was prepared according to the procedure and composition that have been described above in connection with Example 2. A glass button weighing 6 grams was then placed in the crucible, and was preheated to a temperature 650 ° C.

The composition of the glass used was the following in percentages by weight:

TABLE VII

<td>Yes₂</td><td> 50,2</td>

<td>b₂or₃</td><td> 8,6</td>

<td>^{To the}2^F3</td><td> 0,7</td>

<td>^{To the}2^OR3</td><td> 16,0</td>

<td>Beam</td><td> 4,75</td>

<td>ZnO</td><td> 19,75</td>

The preheated crucible and glass-ceramic material were then placed in an apparatus similar to that illustrated in Figure 7, and heated to a temperature of 1400 ° C for a period of 10 minutes. The piston was then actuated, and the crucible was brought into contact with the mold according to the general procedure illustrated in Figures 3 to 6.

A satisfactory dental restoration was obtained which was then removed from the refractory material and cut away from the sprue burr.

The resulting specimens and dental restoration had excellent definition and a MOR of 27.6 MPa (4KSI), a CTE of 56, and a translucency of 0.

During the formation process, the crucible retained its structural integrity and formed an effective seal.

ES 2 235 698 T3 with the mold. Due to the fact that the material used was glass, the resulting dental restoration was not heat treated.

Example 16

A glass ceramic dental restoration according to this invention was prepared and heat treated. The composition of glass-ceramic material conforms to composition No. 8 of Table IV. After melting, the specimens were prepared according to the procedure described above. The resulting specimens had a MOR of 209 MPa (30 KSI), a CTE of 157, a translucency of 40, and a softening temperature of 925 ° C.

The specimens cracked during heat treatment, so the composition was considered unsuitable as a material for use in the fabrication of dental restorations. Consequently, no further tests were performed and the dental restoration did not form.

Example 17

A glass ceramic dental restoration according to this invention was prepared and heat treated. The composition of glass-ceramic material conforms to composition No. 9 of Table IV. After melting, the specimens were prepared according to the procedure described above. The resulting specimens had a MOR of 165 MPa (24 KSI), a CTE of 145, and a softening temperature of 975 ° C.

As the specimens had a MOR of only 24 and it took a long time for the glass-ceramic material to melt and form, the composition was considered unsuitable as a material for use in the fabrication of dental restorations. Consequently, no further tests were performed and the dental restoration did not form.

Example 18

A glass ceramic dental restoration according to this invention was prepared and heat treated. The composition of the glass-ceramic material conforms to the composition No. 10 of Table IV. After preparation of the dental restoration, the specimens were prepared according to the procedure described above. The resulting specimens had a MOR of 285 MPa (41.4 KSI), a CTE of 129, a translucency of 2.5, and a softening temperature of 975 ° C.

As the specimens had a CTE of less than 130, the composition could not be suitable as a material for use in the fabrication of dental restorations. Consequently, no further tests were performed and the dental restoration did not form.

Example 19

A glass ceramic dental restoration according to this invention was prepared and heat treated. The composition of glass-ceramic material conforms to composition No. 11 of Table IV. After preparation of the dental restoration, the specimens were prepared according to the procedure described above. The resulting specimens had a MOR of 214 MPa (35 KSI), a CTE of 80, a translucency of 3.5, and a softening temperature of 975 ° C.

As the specimens had a CTE of 80, the composition was considered unsuitable as a material for use in the fabrication of dental restorations. Consequently, no further tests were performed and the dental restoration did not form.

Example 20

A glass ceramic dental restoration according to this invention was prepared and heat treated. The composition of the glass-ceramic material conforms to the composition No. 12 of Table IV. After preparation of the dental restoration, the specimens were prepared according to the procedure described above. The resulting specimens had a MOR of 214 MPa (31 KSI), a CTE of 127, and a translucency of 2.5.

As the specimens had a CTE of 127, the composition could not be suitable as a material for use in the fabrication of dental restorations. Consequently, no further tests were performed and the dental restoration did not form.

Example 21

A glass ceramic dental restoration according to this invention was prepared and heat treated. The composition of the glass-ceramic material conforms to the composition No. 13 of Table IV. After preparation of the dental restoration, the specimens were prepared according to the procedure described above. The resulting specimens had a MOR of 221 MPa (32 KSI), a CTE of 256, and a translucency of 5.

As the specimens had a CTE of 256, the composition was considered unsuitable as a material for use in the fabrication of dental restorations. Consequently, no further tests were performed and the dental restoration did not form.

ES 2 235 698 T3

Example 22

A glass ceramic dental restoration according to this invention was prepared and heat treated. The composition of the glass-ceramic material conforms to the composition No. 14 of Table IV. After preparation of the dental restoration, the specimens were prepared according to the procedure described above. The resulting specimens had a MOR of 89.6 MPa (13 KSI), a CTE of 126, and a translucency of 4.5.

As the specimens had a low CTE and MOR, the composition was considered unsuitable as a material for use in the fabrication of dental restorations. Consequently, no further tests were performed and the dental restoration did not form.

Example 23

A glass ceramic dental restoration was prepared and augmented according to this invention. The composition of the glass-ceramic material conforms to the composition No. 15 of Table IV. After preparation of the dental restoration, the specimens were prepared according to the procedure described above. The resulting specimens had a translucency of 5.0.

As the specimens became opaque during heat treatment, the composition was considered unsuitable as a material for use in the fabrication of dental restorations. Consequently, no further tests were performed and the dental restoration did not form.

Example 24

A glass ceramic dental restoration was prepared according to the procedure outlined below. A mold was prepared according to the procedure described above.

Using slip molding techniques, a crucible was prepared according to the procedure and composition previously described in connection with Example 6. A glass button weighing 6 grams was then placed in the crucible, and was preheated to a temperature 650 ° C.

The composition of the glass-ceramic material used conforms to composition No. 16 of Table IV.

The preheated crucible and glass-ceramic material were then placed in an apparatus similar to that illustrated in Figure 7, and heated to a temperature of 1425 ° C for a period of 10 minutes. The piston was then actuated, and the crucible was brought into contact with the mold according to the general procedure illustrated in Figures 3 to 6.

The dental restoration was then removed from the refractory material, cut away from the sprue burr, and heat treated.

The resulting specimens and dental restoration had excellent definition with a MOR of 241 MPa (35 KSI), a CTE of 148, a translucency of 3.5, and a softening temperature of 950 ° C.

During the formation process, the crucible retained its structural integrity and formed an effective seal with the mold. Furthermore, during the heat treatment process the finished dental restoration retained its structural integrity and did not collapse or deform during heat treatment.

The refractory material used was Whipmix GTJM 3-23-94, which has been previously described herein. The refractory material had a percent expansion of about 3%. As a result of this percentage of dilation, the resulting dental restoration presented an excellent fit.

Example 25

A glass ceramic dental restoration was prepared according to the procedure outlined below. A mold was prepared according to the procedure described above.

Using slip molding techniques, a crucible was prepared according to the procedure and composition previously described in connection with Example 6. A glass button weighing 6 grams was then placed in the crucible, and was preheated to a temperature 650 ° C.

The composition of the glass-ceramic material used conforms to composition No. 17 of Table IV.

The preheated crucible and glass-ceramic material were then placed in an apparatus similar to that illustrated in Figure 7, and heated to a temperature of 1425 ° C for a period of 10 minutes. The piston was then actuated, and the crucible was brought into contact with the mold according to the general procedure illustrated in Figures 3 to 6.

ES 2 235 698 T3

The dental restoration was then heat treated in the refractory material.

The resulting specimens and dental restoration had excellent definition with a MOR of 276 MPa (40 KSI), a CTE of 138, a translucency of 3.5, and a softening temperature of 950 ° C.

During the formation process, the crucible retained its structural integrity and formed an effective seal with the mold. Furthermore, during the heat treatment process the finished dental restoration retained its structural integrity, and did not collapse or deform during heat treatment.

The refractory investment material used was the Thermovest material, and after the heat treatment it was removed, and the resulting dental restoration presented an excellent fit.

Example 26

A glass ceramic dental restoration was prepared according to the procedure outlined below. A mold was prepared according to the procedure described above.

Using slip molding techniques, a mold was prepared according to the procedure and composition described above in connection with Example 6. A glass button weighing 6 grams was then placed in the crucible.

The composition of the glass-ceramic material used conforms to composition 18 of Table IV.

The crucible and the glass-ceramic material were then placed in an apparatus similar to that illustrated in Figures 7a and 7b, and were heated to a temperature of 1425 ° C for a period of 5 minutes. The piston was then actuated, and the crucible was brought into contact with the mold according to the general procedure illustrated in Figures 3 to 6.

The dental restoration was then removed from the refractory material, cut away from the sprue burr, and subjected to heat treatment.

The resulting specimens and dental restoration had excellent definition and a MOR of 324 MPa (47 KSI), a translucency of 4.0, and a softening temperature of 950 ° C.

During the formation process, the crucible retained its structural integrity and formed an effective seal with the mold. Furthermore, during the heat treatment process the finished dental restoration retained its structural integrity and did not collapse or deform during heat treatment.

The refractory material used was the Whipmix GTJM 3-23-94 material, which has been previously described herein. The refractory material had a percent expansion of about 3%. As a result of this percentage of dilation, the resulting dental restoration had an excellent fit.

Example 27

A glass ceramic dental restoration was prepared according to the procedure outlined below. A mold was prepared according to the procedure described above.

Using slip casting techniques, a crucible was prepared according to the procedure and composition that have been described above in connection with Example 6. A glass button weighing 6 grams was then placed in the crucible, and was not preheated.

The composition of the glass-ceramic material used conforms to composition 19 of Table IV.

The crucible and the glass-ceramic material were then placed in an apparatus that is similar to that illustrated in Figures 7a and 7b, and were heated to a temperature of 1425 ° C for a period of 5 minutes. The piston was then actuated, and the crucible was brought into contact with the mold according to the general procedure illustrated in Figures 3 to 6.

The dental restoration was then removed from the refractory material, cut away from the sprue burr, and subjected to heat treatment.

The resulting specimens and dental restoration had excellent definition and a MOR of 359 MPa (52 KSI), a translucency of 3.5, and a softening temperature of 950 ° C.

During the formation process, the crucible retained its structural integrity and formed an effective seal with the mold. Furthermore, during the heat treatment process the finished dental restoration retained its structural integrity and did not collapse or deform during heat treatment.

ES 2 235 698 T3

The refractory material used was the Whipmix GTJM 3-23-94 material, which has been described hereinabove. The refractory material had a total percent expansion of approximately 3%. As a result of this percentage of dilation, the resulting dental restoration had an excellent fit.

Examples 26 and 27 represent the preferred glass-ceramic process and compositions according to this invention. As mentioned, the dental restorations resulting from these Examples were heat treated, and the heat treatment procedure used for Examples 26 and 27 is as indicated in Table VIII.

TABLE VIII

Heat Dental Restoration to Increase or standardize temp. a Increase temperature a Maintain temperature a Increase temp. to

Uniform temperature to Cool to

450 ° C at oven speed 450-550 ° C for 6 hours 550-850 ° C for 2 hours 850 ° C for 45 minutes 850-900 ° C at speed. oven 900 ° C for 15 minutes at room temperature

After heat treatment, the dental restorations of Examples 26 and 27 were further finished by altering the shape and tone with a high-melting porcelain that is sold under the brand name Ceramco II and with a low-melting porcelain. which is sold under the Final Touch brand. Both in terms of application to fire and in terms of adhesion, the performances of both the high-melting point porcelain and the low-melting point porcelain were good. Similarly, both porcelains had thermal expansions that were compatible with the glass-ceramic materials from which the dental restorations had been formed.

The Ceramco II and Final Touch porcelains used herein are manufactured and sold by Ceramco, Inc., of six Terri Lane, Burlington, NJ 08016.

In relation to the dental restorations that were produced according to Examples 26 and 27 above, it should be noted that these restorations turned out to be exceptionally strong as they had MORs of approximately 345 MPa (50 KSI).

It should be noted that the MORs of Examples 26 and 27 do not correlate with the MORs specified in relation to the other examples, since a different test protocol was used for the measurement of the MORs of Examples 26 and 27. The tests for the determination of the MOR for Examples 26 and 27 were carried out on a Lloyd Instrument material testing apparatus type No. TG 18, manufactured by John Chatillon &amp; Sons Inc. of Greensboro, NC These measurements were made according to the ISO 6872 test using cylindrical specimens of 0.318 cm (0.125 ") in diameter with bending over 3 points with a distance between supports of 2.54 cm (1") and with a head speed of 1 mm per minute.

In contrast to this, the MOR measurements of the other Examples were carried out on equipment that was manufactured by the Applicant. This equipment has characteristics that are similar to those of the previously described Lloyd type N ° TG 18 material testing apparatus, and the same specimens were used in it. It could be said in general that the MORs of Examples other than Examples 26 and 27 appear to be low.

For a correlation between the MOR test protocol of Examples 26 and 27 and the test protocol of the other Examples, reference should be made to Table IX.

TABLE IX

<td>Example No.</td><td>MOR indicated according to test used for Examples 1-25</td><td>MOR according to ISO test N ° 6872</td>

<td> 26</td><td>290 MPa (42 KSI)</td><td>324 MPa (47 KSI)</td>

<td> 27</td><td>310 MPa (45 KSI)</td><td>359 MPa (52 KSI)</td>

Example 28

A glass ceramic dental restoration was prepared according to the procedure outlined below. A mold was prepared according to the procedure described above.

Using slip molding techniques, a crucible was prepared according to the procedure and composition that have been described above in conjunction with Example 6. A glass button weighing 6 grams was then placed in the crucible, and was preheated to a temperature 650 ° C.

ES 2 235 698 T3

The composition of the glass-ceramic material used is in accordance with composition 10 of Table IV.

The preheated crucible and glass-ceramic material were then placed in an apparatus similar to that illustrated in Figure 7, and heated to a temperature of 1425 ° C for a period of 10 minutes. The piston was then actuated, and the crucible was brought into contact with the mold according to the general procedure illustrated in Figures 3 to 6.

The dental restoration was then heat treated.

The resulting specimens and dental restoration had excellent definition and a CTE of 111 KSI, a translucency of 3.5, and a softening temperature of 850 ° C.

During the formation process, the crucible retained its structural integrity and formed an effective seal with the mold. Furthermore, during the heat treatment process the finished dental restoration retained its structural integrity and did not collapse or deform during heat treatment.

It should be understood that the invention is not limited to the embodiment illustrated and described in Figures 1-10 and in Examples 1 to 28, since the parameters of the process and the compositions can be varied and the configuration of the apparatus can be altered without therefore, it is outside the scope of the invention.

The above description and drawings are illustrative only, since modifications could be incorporated without departing from the scope of the present invention, the scope of which should be limited only by the following claims.