WO2007053084A1

WO2007053084A1 - Device designed for a dental prosthetic or prosthetic component

Info

Publication number: WO2007053084A1
Application number: PCT/SE2006/001230
Authority: WO
Inventors: Mattias Iverhed; Petrus Brännvall
Original assignee: Nobel Biocare Services Ag
Priority date: 2005-11-03
Filing date: 2006-10-31
Publication date: 2007-05-10

Abstract

A device designed for a dental prosthetic or prosthetic component such as a cap, crown, dental bridge, implant bridge, implant, etc., shows a color tone that is similar or corresponds to the outer color tone of a real normal tooth. The prosthetic/prosthetic component is manufactured from zirconium oxide powder and praseodymium oxide Pr6O11 powder mixed and distributed therein with a maximum content in mole percent (mol%) of 0.1, and preferably 0.0001-0.03.

Description

Device designed for a dental prosthetic or prosthetic component .

The present invention concerns a device in the form of a dental prosthetic or prosthetic component, such as a spacer, cap, crown, dental bridge, implant bridge, implant, etc., which is designed to achieve a color tone that is similar or corresponds to the outer color tone of a real normal tooth.

Ceramic products of said type designed to achieve a color tone that corresponds to the color tone of the average real tooth are known in prior art. Examples _.include U.S. Patents 5,219,805 and 5,263,858 and WO Patents 00 46168, 01 12097, and 01 12132.

The known products and processes for the manufacture thereof disclosed in said patents and patent documents have the common characteristics of being relatively complex and often making use of a number of dopants that are to be included in solutions of various types. This gives rise to difficulties in achieving the desired uniform color tone composition in the product in question.

Moreover, the aforementioned known processes and products are best suited for smaller equipment to be set up on the user's premises, with said user then being responsible for the determining the appropriate amounts used.

There is a need for a simpler process and more precise determination of color tone compositions. A process is also needed in which only minor adjustments are necessary in order to select the components included in the products, thus making it possible to vary the color tone composition within a narrow desired range without sacrificing the requirement of precision. It should be possible to maintain the strength of products of this type and meet the need for reducing or eliminating toxicity. The device should also be suitable for centralized manufacturing. 5

The purpose of the present invention is to solve some or all of the aforementioned problems, and the main characteristic of the prosthetic/prosthetic component/product according to the invention can be 10 considered to be that it is manufactured from zirconium oxide powder with praseodymium oxide Pr₆On powder thoroughly mixed and distributed in it as a dopant with a maximum content of 0.1 mole percent (mol%).

15 In further embodiments of the concept of the invention, the mixed powders in the dental prosthetic or prosthetic component may be based on a suspension obtained by means of wet milling and spray drying. Alternatively, the mixed powders in the dental prosthetic or prosthetic component

20 may be based on dry-mixed, ready-to-press zirconium powder and said dopant. In a further embodiment, the mixed powders in the dental prosthetic or prosthetic component may be based on coprecipitation of zirconium and praseodymium chlorides, as well as washing,

25 filtration, drying, etc. The content in mol% should be selected in the working example within the range of 0.0001-0.03, and preferably within the range of 0.005- 0.01 mol%.

30 By means of the method proposed above, the ZrO₂ powder used by the applicant of the present invention in other contexts can be advantageously used together with Pr₆On

^'; or another compatible Pr powder in the present invention as well. The content may be kept low in order to meet the

35 standard ISO 13356:1997 (said standard specifies that the content of "other oxides" shall be lower than 0.5%). It is also possible, for reasons relating purely to production technology, to carry out mixing in two steps, using a powder concentrate as step 1, and then carrying out final mixing to achieve the "right" content as step 2. This doped/dyed powder is then used as a conventional non-dyed powder. Factors that may affect the final content of the composition are the color tone that the product owner/user prefers, as well as effects on strength. However, preliminary data indicate that there are no major differences in strength. Products that can be advantageously manufactured from dyed ZrO₂ include spacers, as well as caps and bridges. Spacers and caps are currently produced, among other processes, by pressing powder onto individual dies, which are then milled. Thus blanks are not used in this production.

A provisional proposed embodiment of the invention will be described below with reference to the attached drawings, in which:

Fig. 1 is a schematic diagram of various types of suitable dental products/prosthetics/ prosthetic components,

Fig. 2 is a schematic flow chart of the manufacture of a dental cap, and

Fig. 3 is a table showing data for light yellow color tones.

In the figure, 1 shows an example of a connecting spacer designed to be used in a known manner in a dental prosthetic. 2 indicates a cap, 3 an implant, 4 a crown, and 5 components of a dental bridge. The crown may include a prosthetic tooth 4a applied to a tooth remnant 4b. The gum is indicated by 4c and the jawbone by 4d. The dental bridge may be applied in a known manner to two .or more implants that are not shown and may be supported in a known manner by prosthetic teeth, also not shown.

As shown in Fig. 2, a user site 6, e.g. a dental clinic, dental laboratory, dental technician, etc., orders a relevant dental prosthetic component, such as a cap, from a centralized manufacturing unit 7 of the PROCERA® type. The unit receives orders in the known manner via a receiving site 8. Zirconium oxide 9 and praseodymium oxide 10 are selected in appropriate amounts and transferred to a shaking machine 11, which goes into operation as indicated by arrow 12. The directions of transfer of information from the unit 8 to the powders 9, 10 are indicated by arrows 13, 14, and the directions of transfer of the powders 9, 10 to the shaking machine are indicated by arrows 15, 16. Shaking is carried out in such a manner that a highly uniform distribution of the dopant in the zirconium powder is achieved. When shaking of the powder is completed, it is transferred in the direction indicated by arrow 17 to a schematically shown pressing tool 18 with a die 19 and a tool component 20. A space 21 between components 19 and 20 is filled with shaken powder 22, which is pressed together by the components with pressing forces F at 100-300 MPa. The die 19 with the powder pressed onto it in this manner, which forms a body 22' , is milled using a milling tool, which is symbolically indicated by 24. Milling takes place under simultaneous rotation in the direction shown by arrow 25 around the rotation axis 26. In the figure, the milling function is shown only schematically in order to show that the milled outer form 22' ' forms the inner surface of the cap, while the outer form of the die forms the inner surface of the cap. The milled cap is transferred in the direction indicated by arrow 27 to a schematically shown sintering furnace 28 into which the milled cap 29 Is introduced, where is exposed to a sintering temperature of 1400-1700°C for 1-2 hours. During this time, the cap 29 shrinks to its final dimensions and is transferred in the direction shown by arrow 30 to a final processing site 31, where the cap is given its final finish. The process described may be supplemented with additional processing steps.

The applicant of the present patent supplies aluminum oxide (AI₂O₃) products on the general market that have a light yellow color and, according to the invention, it will also become possible to offer a similar color in zirconium oxide (ZrO₂) products. Zirconium oxide, in the form of yttrium-stabilized zirconium oxide YTZP, is present in powder form, and praseodymium (Pr), also in powder oxide form, is to be mixed with the zirconium oxide so that the aforementioned completely uniform mixing of the dopant powder with the zirconium oxide powder is achieved. For example, powder processing may be carried out as described in the following three examples. The maximum content of PrsOn is 0.1 mol%, and preferably 0.0001-0.01 mol%, which provides a particularly advantageous touch of yellow color that closely matches that of a normal tooth.

Example 1:

Dry mixing

Ready-to-press ZrO₂ (e.g. Tosoh TZ-3YSB-E) powder is mixed with a praseodymium oxide, Pr₆On.

Mixing may take place in powder mixing equipment (e.g., the Turbula T2F, Willy A. Bachofen AG).

Mixing may take place in powder mixing equipment with milling bodies/cylpebs . Mixing may take place in a rotary mill.

Mixing may take place in a rotary mill with milling bodies/cylpebs .

Example 2 :

Wet milling and spray drying

A suspension of Pr₆On (e.g. Tosoh TZ-3YS-E) and Pr₆On (same contents as above) is manufactured and spray-dried in the usual manner. The suspension may be prepared by means of:

Wet milling in a rotary mill with milling bodies/cylpebs

Wet milling in a grinding mill with milling bodies/cylpebs (e.g. Sweco M18)

Example 3 : Coprecipitation

Zr and Pr chlorides are slowly added to an ammonia solution, after which the precipitate is washed, filtered, and dried. After calcining, the precipitate is mixed with a binder and spray-dried.

The powder produced may be used to manufacture caps, spacers, bridges, implants, etc. that show a more natural basic color tone or a basic color tone that closely resembles the external color composition of a real normal tooth. By means of the invention, one can achieve yellow color tones that closely resemble the color tones of said normal tooth.

The samples were manufactured by mixing yttrium- stabilized zirconium dioxide (Tosoh TZ-3YSB-C) with an individual dopant in the form of praseodymium oxide (PrβOn from Sigma-Aldrich) in the amounts shown in the table of Fig. 3. Pressing of the sample units was carried out at 250 MPa using a tool having a diameter of 12.7 mm and a thickness of 2 mm. Sintering was carried out as follows:

Ramping 10°C/min.

Holding time 1 h at 500°C

Ramping 30°C/min

Holding time 2 h at 1600°C.

Color measurements were determined according to CIELAB parameters (L^*a^*b) using the Minolta Spectrophotometer CM-503i, with the following settings:

2° Standard Observer Standard Illuminant D₆₅-

On assessing the color compositions, it was found that the dopants with concentrations of 0.010 and 0.030 mol% yielded particularly favorable results, so values within this range are preferred. The table of Fig. 3 shows various values for luminosity, red-green chromaticity, and yellow-blue chromaticity.

The invention is not limited to the embodiments described above as examples, but may be subjected to modifications within the framework of the following claims and the scope of the invention.

Claims

1. A device designed for a dental prosthetic or prosthetic component such as a cap, crown, dental bridge, implant bridge, implant, etc., in order to impart to said prosthetic or prosthetic component a color tone that is similar or corresponds to the external color tone of a real normal tooth, characterized in that the prosthetic or prosthetic component' is manufactured from zirconium oxide powder and praseodymium oxide PrβOn powder mixed and distributed therein as a dopant with a maximum concentration in mole percent (mol%) of 0.1.

2. The device as claimed in claim 1, characterized in that the mixed powders in the dental prosthetic or prosthetic component are based on a suspension produced by wet milling and spray-drying.

3. The device as claimed in claim 1, characterized in that the mixed powders in the dental prosthetic or prosthetic component are based on dry-mixed, ready-to- press zirconium powder and said powdered dopant.

4. The device as claimed in claim 1, characterized in that the mixed powders in the dental prosthetic or prosthetic component are based on coprecipitation of zirconium and praseodymium chlorides, as well as washing, filtering, drying, etc.

5. The device as claimed in claims 1, 2, 3, or 4, characterized in that the content in mol% is selected within the range of 0.0001-0.03.

6. The device as claimed in any of the preceding claims, characterized in that the dopant is distributed in a highly uniform manner in the zirconium oxide.

7. The device as claimed in any of the preceding claims, characterized in that the prosthetic or prosthetic component is manufactured in a central system (PROCERA®) .

8. The device as claimed in any of the preceding claims, characterized in that the prosthetic or prosthetic component is composed of powder pressed together at a pressure of 100-300 MPa.

9. The device as claimed in any of the preceding claims, characterized in that the prosthetic or prosthetic component shows a milled and polished outer surface.

10. Device as claimed in any of the preceding claims, characterized in that the prosthetic or prosthetic component is sintered at a sintering temperature of 1400- 1700°C for 1-2 h.