Dental implant or abutment comprising a ceramic body covered with a monomolecular phosphate layer

Abstract

The present invention refers to a dental implant or abutment including a ceramic body having a surface, the ceramic body including zirconia as the main component. At least a first surface area of the ceramic body is covered with an at least essentially monomolecular phosphate layer having a thickness of less than 1.0 nm. The phosphate layer contains phosphates selected from the group consisting of ortho-phosphate, poly-phosphates, cyclo-phosphates, and mixtures thereof. Furthermore, a kit including a gas- and liquid-tight container, with the dental implant or abutment being stored inside the container, and a method for the preparation of the dental implant or abutment are disclosed.

Claims

1. A dental implant or abutment comprising a ceramic body comprising zirconia as the main component, the ceramic body having a surface, wherein: at least a first surface area of the ceramic body is covered with a phosphate layer having a thickness in a range of from 0.7 to 1.3 phosphate molecules, the phosphate layer contains phosphates selected from the group consisting of ortho-phosphate, polyphosphates, cyclo-phosphates, and mixtures thereof, and the phosphate layer does not change a surface morphology of the ceramic body.

2. The dental implant or abutment according to claim 1, wherein the ceramic body is covered with a monomolecular phosphate layer.

3. The dental implant or abutment according to claim 1, wherein the phosphate layer has a thickness of about 0.5 nm.

4. The dental implant or abutment according to claim 1, wherein the phosphates in the phosphate layer are selected from the group consisting of ortho-phosphate, di-phosphate, tri-phosphate, trimeta-phosphate, and mixtures thereof.

5. The dental implant according to claim 1, wherein the dental implant comprises a bone contact surface area and optionally also a soft tissue contact surface area, and wherein at least the bone contact surface area is covered with the phosphate layer.

6. The dental implant according to claim 5, wherein the soft tissue contact surface area is also covered with the phosphate layer.

7. The dental implant according to claim 1, wherein the dental implant comprises an anchoring part for anchoring the dental implant in a jaw bone and a mounting part for attaching a suprastructure, and at least the anchoring part is covered with the phosphate layer.

8. The dental implant or abutment according to claim 1, wherein an entirety of the surface of the ceramic body is covered with the phosphate layer.

9. The dental implant or abutment according to claim 1, wherein the ceramic body is made of stabilized zirconia.

10. The dental implant or abutment according to claim 9, wherein the ceramic body is made of yttria-stabilized zirconia, ceria-stabilized zirconia, magnesium oxide stabilized zirconia, or alumina-stabilized zirconia.

11. The dental implant or abutment according to claim 1, wherein the dental implant or abutment is stored in water optionally containing one or more additives.

12. The dental implant or abutment according to claim 11, wherein the dental implant or abutment is stored in an aqueous phosphate solution.

13. The dental implant or abutment according to claim 12, wherein the aqueous phosphate solution is an aqueous phosphate buffer solution.

14. The dental implant or abutment according to claim 1, wherein the phosphate layer does not change a topography of the surface of the ceramic body.

15. The dental implant or abutment according to claim 1, wherein the phosphates occupy at least 10% of adsorption sites on the surface of the ceramic body.

16. A kit comprising a gas- and liquid-tight container and the dental implant or abutment of claim 1, wherein the dental implant or abutment is stored in the container.

17. The kit according to claim 16, wherein at least part of the remaining volume of the container is filled with an aqueous phosphate buffer solution and/or an inert gas.

18. A method for preparing the dental implant or abutment according to claim 1, comprising: treating the ceramic body of the dental implant or abutment with an aqueous phosphate buffer solution, and subsequently rinsing the ceramic body with water or an aqueous, phosphate-free solution.

19. The method according to claim 18, further comprising subjecting the dental implant or abutment to a thermal or hydrothermal treatment prior to or after the rinsing.

20. The method according to claim 18, further comprising roughening and/or rendering hydrophilic the surface of the ceramic body prior to the treatment with the aqueous phosphate buffer solution.

Description

EXAMPLE 1

Preparation of a Thick Phosphate Coating (State of the Art)

(1) Preparation of Samples

(2) Smooth ZrO.sub.2 discs (Tosoh from Ceramtec) with a diameter of 14 mm having a polished surface were cleaned with a basic, phosphate-free cleaning agent (Deconex 15PF from Max F. Keller GmbH, Mannheim) and subjected to ultra sonication for 5 min and to oxygen plasma cleaning (using an apparatus of the type Femto by Diener Electronics GmbH+Co. KG, Ebhausen, Germany; 35 W, 6 sccm (standard cubic centimeter per minute; 1 cm.sup.3 per minute at normal pressure, i.e. 1013 mbar) O.sub.2 gas flow, p0.1 mbar, time=2.5 minutes).

(3) The cleaned discs were immersed in 10 ml of 0.5 M Na-phosphate buffer (pH=7.2) in glass test tubes and subjected to hydrothermal treatment (121 C., 20 min) in the autoclave.

(4) Without rinsing, the discs were dried by heating to 60 C. for 1 h.

(5) Surface Morphology

(6) The surface morphology of the discs was investigated with an optical microscope. Images were taken with 50 magnification. FIGS. 1a, 1b, and 1c show the surface of three different discs treated in the above described way.

(7) As can be clearly seen from these images, a relatively thick, inhomogeneous phosphate coating has formed on the ceramic surface and completely covers this surface.

(8) Thickness of Phosphate Layer

(9) The thickness of the phosphate coatings was determined as being in the micrometer range. Determination was performed for three samples using confocal microscopy and the following results were obtained: Sample 1:4 to 5 m Sample 2:20 to 25 m Sample 3:15 m

EXAMPLE 2

Preparation of an Essentially Monomolecular Ortho-Phosphate Layer (Rinsing by Immersion)

(10) Preparation of Samples

(11) Smooth ZrO.sub.2 discs (Tosoh from Ceramtec) with a diameter of 14 mm having a polished surface were cleaned with a basic, phosphate-free cleaning agent (Deconex 15PF from Max F. Keller GmbH, Mannheim) and subjected to ultra sonication for 5 min and to oxygen plasma cleaning (using an apparatus of the type Femto by Diener Electronics GmbH+Co. KG, Ebhausen, Germany; 35 W, 6 sccm O.sub.2 gas flow, p0.1 mbar, time=2.5 minutes).

(12) The cleaned discs were immersed in 10 ml of 0.5 M Na-phosphate buffer (pH=7.2) in glass test tubes and subjected to hydrothermal treatment (121 C., 20 min) in the autoclave.

(13) The treated discs were then rinsed with ultrapure water: Two glass beakers were filled with water (300 ml each) and the discs were immersed for about 5 s in each of the beakers while performing slow swirling movements.

(14) The surface was then blown dry in a stream of Ar.

(15) Surface Morphology

(16) The surface morphology of the discs was investigated with an optical microscope. Images were taken with 50 magnification. FIGS. 2a, 2b, and 2c show the surface of three different discs treated in the above described way.

(17) In these images, the phosphate layer on the ceramic surface is invisible and the morphology of the ceramic surface is essentially unchanged.

(18) Surface Composition

(19) The chemical composition of the surface was determined by XPS and is represented below:

(20) TABLE-US-00001 Zr P Y C N O Si Al # [%] [%] [%] [%] [%] [%] [%] [%] 3 23.4 2.7 1.5 14.7 0.3 54.4 2.0 0.9 4 23.7 2.8 1.4 18.6 0.9 50.7 0.8 0.8
Thickness of Phosphate Layer

(21) Based on the above atomic concentrations, the thickness of the phosphate layers was calculated based on the following assumptions: Tetragonal structure of ZrO.sub.2, (101) surface (unit cell 3.6 3.6 5.18 ; 2 Zr, 4 O) .fwdarw.n.sub.Zr,101=7.58 atoms/nm.sup.2; interlayer distance d.sub.Zr,101=0.254 nm Number of phosphate binding sites equal to number of Zr atoms on the surfaces .fwdarw.n.sub.P,101=7.58 atoms/nm.sup.2 (number of binding sites equal to number of Zr atoms on the surface) Electron mean free path: =3.47 nm

(22) The thickness of the phosphate layer was then calculated using the following equation:

(23) $z=.Math.\cos .Math.\ln \left(\frac{I_{\mathrm{overlayer}}.Math.n_{\mathrm{substrate}}}{I_{\mathrm{substrate}}.Math.n_{\mathrm{overlayer}}}+1\right).Math.\frac{1}{d_{\mathrm{Zr},101}}$
( being the electron emission angle; in the present case =45)

(24) Based on the average values of the above two samples, the thickness of the phosphate layer was determined as 1.1 monolayers.

EXAMPLE 3

Preparation of an Essentially Monomolecular Ortho-Phosphate Layer (Rinsing under Running Water)

(25) Preparation of Samples

(26) Smooth ZrO.sub.2 discs (Tosoh from Ceramtec) with a diameter of 14 mm having a polished surface were cleaned with a basic, phosphate-free cleaning agent (Deconex 15PF from Max F. Keller GmbH, Mannheim) and subjected to ultra sonication for 5 min and to oxygen plasma cleaning (using an apparatus of the type Femto by Diener Electronics GmbH+Co. KG, Ebhausen, Germany; 35 W, 6 sccm O.sub.2 gas flow, p0.1 mbar, time=2.5 minutes).

(27) The cleaned discs were immersed in 10 ml of 0.5 M Na-phosphate buffer (pH=7.2) in glass test tubes and subjected to hydrothermal treatment (121 C., 20 min) in the autoclave.

(28) The treated discs were then rinsed under running water for about 30 s and blown dry in a stream of Ar.

(29) Surface Composition

(30) The chemical composition of the surface was determined by XPS and is represented below:

(31) TABLE-US-00002 Zr P Y C N O Si Al # [%] [%] [%] [%] [%] [%] [%] [%] 5 23.8 2.6 1.4 19.4 1.2 49.9 0.7 1.0 6 22.7 2.1 1.2 19.4 0.1 51.4 2.0 0.7
Thickness of Phosphate Layer

(32) The thickness of the phosphate layer was calculated according to the method described in example 2. Based on the average values of the above two samples, the thickness of the phosphate layer was determined as 0.9 monolayers.

EXAMPLE 4

Preparation of an Essentially Monomolecular Ortho-Phosphate Layer (Rinsing and Ultra Sonification)

(33) Preparation of Samples

(34) Smooth ZrO.sub.2 discs (Tosoh from Ceramtec) with a diameter of 14 mm having a polished surface were cleaned with a basic, phosphate-free cleaning agent (Deconex 15PF from Max F. Keller GmbH, Mannheim) and subjected to ultra sonication for 5 min and to oxygen plasma cleaning (using an apparatus of the type Femto by Diener Electronics GmbH+Co. KG, Ebhausen, Germany; 35 W, 6 sccm O.sub.2 gas flow, p0.1 mbar, time=2.5 min).

(35) The cleaned discs were immersed in 10 ml of 0.5 M Na-phosphate buffer (pH=7.2) in glass test tubes and subjected to hydrothermal treatment (121 C., 20 min) in the autoclave.

(36) The treated discs were then rinsed with ultrapure water: Two glass beakers were filled with water (300 ml each) and the discs were immersed for about 5 s in each of the beakers while performing slow movements. Subsequently, the discs were subjected to ultra sonification for 5 min in water at room temperature, followed by a further round of rinsing as before.

(37) Surface Composition

(38) The surface was then blow dried in a stream of Ar.

(39) The chemical composition of the surface was determined by XPS and is represented below:

(40) TABLE-US-00003 Zr P Y C N O Si Al # [%] [%] [%] [%] [%] [%] [%] [%] 7 24.6 2.1 1.6 18.8 0.4 50.4 0.9 1.0 8 25.0 2.2 1.6 17.0 0.1 52.6 0.8 0.7
Thickness of Phosphate Layer

(41) The thickness of the phosphate layer was calculated according to the method described in example 2. Based on the average values of the above two samples, the thickness of the phosphate layer was determined as 0.80 monolayers.

EXAMPLE 5

Contact Angle Measurement of Samples Having a Thin Phosphate Layer (HF Etching of Ceramic Substrate Prior to Phosphate Coating)

(42) ZrO.sub.2 discs (MZ111 from Ceramtec) with a diameter of 15 mm were cleaned according to Examples 1 to 4. The cleaned samples were then treated as follows:

(43) A (According to the Present Invention):

(44) etching with HF followed by rinsing with pure water and I) immersion in test glass in 0.5 M Na-phosphate buffer (pH=7.2) or II) immersion in test glass in 0.1 M Na-phosphate buffer (pH=7.2)
B (Reference):

(45) etching with HF followed by rinsing with pure water and storage in pure water

(46) Surface Composition

(47) For XPS characterization, the samples were stored in the phosphate buffer for 2 days and then rinsed in ultrapure water followed by blow drying in a stream of Ar.

(48) For the samples according to the present invention (two samples for each concentration), the following surface composition has been determined by XPS:

(49) TABLE-US-00004 Zr P Y C N O F # [%] [%] [%] [%] [%] [%] [%] A.I, 01 31.5 2.3 1.4 7.0 0.3 56.8 0.8 A.I, 02 31.4 2.2 1.2 6.9 0.7 56.7 0.8 A.II, 01 28.6 2.1 1.2 16.4 0.7 50.4 0.6 A.II, 02 29.8 2.2 1.3 12.6 0.4 53.0 0.8
Thickness of Phosphate Layer

(50) The thickness of the phosphate layer was calculated according to the method described in example 2. Based on the average values of the above samples, the thickness of the phosphate layer was determined as 0.7 monolayers for sample A.I and 0.7 monolayers sample A.II.

(51) Contact Angle

(52) The contact angle measurements were performed using a sessile drop test with ultrapure water (EasyDrop DSA20E, Krss GmbH). The samples were analysed after different immersion times of 1 day and 22 days in phosphate buffer. The samples analysed after 1 day were afterwards stored dry and remeasured at later time points (6 d, 13 d, 21 d storage in air). The samples stored in liquid were rinsed with ultrapure water (two glass beakers filled with water, about 5 seconds rinsing in each by immersing the samples and performing slow movements) and blown dry in a stream of Ar right before analysis.

(53) The results of the contact angle measurements are shown below. The reference samples were kept in water up to the first analysis (0 d) in order to avoid air exposure and to have the same starting point as for the samples having a phosphate layer according to the present invention.

(54) TABLE-US-00005 Sample Storage period Contact angle 1 Contact angle 2 B (ref) 0 d 0 0 B (ref) 6 d; air 4.6 5.4 B (ref) 13 d; air 17.6 11.6 B (ref) 21 d; air 65 24.7 A. II 22 d; liquid 0 0 A. I 1 d; liquid 0 0 A. I 22 d; liquid 0 0 A. I 6 d; air 0 0 A. I 13 d; air 0 2 A. I 21 d; air 1.6 1.5

(55) For each treatment method and time point, the contact angles of two different samples have been measured (contact angles 1 and 2, respectively).

(56) All samples were hydrophilic right after preparation; they showed complete wetting and thus contact angles of 0.

(57) The contact angles of the reference samples increased with additional storage time in air.

(58) In comparison, the samples according to the present invention, which were covered with a phosphate layer, remained super-hydrophilic with contact angles below 5, even after a storage period of 21 d in air.

EXAMPLE 6

Preparation and Initial Surface Contact Angles of an Essentially Monomolecular Ortho-Phosphate Layer (Sand-Blasted and Acid Etched)

(59) Preparation of Samples

(60) Smooth ZrO.sub.2 discs (Y-TZP, Yttria stabilized zirconia) with a diameter of 5 mm having a machined surface were cleaned with a basic, phosphate-free cleaning agent (Deconex 15PF from Max F. Keller GmbH, Mannheim) and subjected to ultra sonication for 5 min (no oxygen plasma cleaning).

(61) The discs were then subjected to sand-blasting with corundum and acid treatment with HF in order to roughen the surface.

(62) The treated discs were immersed in 20 ml of 0.1 M Na-phosphate buffer (pH=7.2; 3.37 ml 85% H.sub.3PO.sub.4, 3.4 g NaOH, pH adjustment with 1 M NaOH) in a 25 ml Schott Glass (Duranglas) and subjected to hydrothermal treatment (121 C., 20 min).

(63) The treated discs were then rinsed under running water and blown dry in a stream of N.sub.2.

(64) Surface Composition

(65) The chemical composition of the surface was determined by XPS and is represented below:

(66) TABLE-US-00006 Zr P Y C N O Na Al Mg Cl F Ca # [%] [%] [%] [%] [%] [%] [%] [%] [%] [%] [%] [%] 9 26.1 3.8 0.9 11.3 0.6 54.6 0.0 1.9 0.1 0.0 0.5 0.2 10 25.0 3.9 0.9 11.3 0.5 55.1 0.6 1.6 0.0 0.0 1.1 0.0 11 26.0 3.6 0.9 9.5 1.2 54.8 0.5 1.7 0.2 0.0 0.8 0.8
Thickness of Phosphate Layer

(67) The thickness of the phosphate layer was calculated according to the method described in example 2. Based on the average values of the above three samples, the thickness of the phosphate layer was determined as 1.3 monolayers.

(68) Initial Surface Contact Angles

(69) The contact angles measurements were performed with the EasyDrop DSA20E (Krss GmbH) using a sessile drop test with ultrapure water. Three samples were measured for each surface type. The samples stored in liquid were blown dry in a stream of Ar prior to the measurement. After the measurement of the contact angle, all samples were properly rinsed under running water, blown dry with Ar and remeasured. The droplet size for the contact angle measurements was 0.1 l for all samples. The contact angles were determined using the circle fitting procedure (fitting of a circular segment function to the contour of the droplet placed on the surface) implemented in the software.

(70) The samples Phosphate were prepared as described above (present example); the samples Comparison were ZrO.sub.2 discs from the same source, which were sandblasted and acid etched but not treated with a phosphate buffer.

(71) The results of the contact angle (CA) measurements are compiled in the following table. The left part of the table presents the results of the contact angle measurements after blowing dry those samples stored in liquid. The right part of the table presents the results after rinsing all the samples with water and blowing dry with Ar.

(72) TABLE-US-00007 Sample Sample Sample Sample Sample Sample 1 2 3 1 2 3 CA [] CA [] CA [] CA [] CA [] CA [] Phosphate 0 0 0 0 0 0 Comparison 53.5 66.7 8.7 20.3 30.0 7.6

EXAMPLE 7

Preparation and Surface Contact Angles of an Essentially Monomolecular Ortho-Phosphate Layer (Sand-Blasted and Acid Etched)

(73) Preparation of Samples

(74) Smooth ZrO.sub.2 discs (Y-TZP, yttria stabilized zirconia) with a diameter of 5 mm having a machined surface were cleaned with a basic, phosphate-free cleaning agent (Deconex 15PF from Max F. Keller GmbH, Mannheim) and subjected to ultra sonication for 5 min (no oxygen plasma cleaning).

(75) The discs were then subjected to sand-blasting with corundum and acid treatment with HF in order to roughen the surface.

(76) The cleaned discs were immersed in 20 ml of 0.1 M Na-phosphate buffer (pH=7.2; 3.37 ml 85% H.sub.3PO.sub.4, 3.4 g NaOH, pH adjustment with 1 M NaOH) in a 25 ml Schott Glass (Duranglas) and subjected to hydrothermal treatment (121 C., 20 min).

(77) Surface Contact Angles

(78) The contact angles measurements were performed with the EasyDrop DSA20E (Krss GmbH) using a sessile drop test with ultrapure water. Two samples were measured for each surface type. The samples stored in liquid were blown dry in a stream of Ar prior to the measurement. After the measurement of the contact angle, all samples were properly rinsed under running water, blown dry with Ar and remeasured. The droplet size for the contact angle measurements was 0.1 l for all samples. The contact angles were determined using the circle fitting procedure (fitting of a circular segment function to the contour of the droplet placed on the surface) implemented in the software.

(79) The samples Phosphate were prepared as described above (present example); the samples Comparison were ZrO.sub.2 discs from the same source, which were sandblasted and acid etched but not treated with a phosphate buffer.

(80) The results of the initial contact angle (CA) measurements are compiled in the first table below. The left part of the first table presents the results of the contact angle measurements after blowing dry those samples stored in liquid. The right part of the table presents the results after rinsing all the samples with water and blowing dry with Ar.

(81) TABLE-US-00008 Sample 1 Sample 2 Sample 1 Sample 2 CA [] CA [] CA [] CA [] Phosphate 0 0 0 0 Comparison 45.2 50.2 32.2 12.2

(82) The contact angles of the same samples were measured once again after storing the rinsed and blown dry samples in air for 19 days. The results of the contact angle measurements after 19 days of air storage are shown in the second table below:

(83) TABLE-US-00009 Sample 1 Sample 2 CA [] CA [] Phosphate 31.4 18.9 Comparison 99 103.7

(84) As can be seen from the above results, the surface of the zirconium oxide discs covered with an essentially monomolecular phosphate layer is not only significantly more hydrophilic in the initial stage, but this hydrophilicity is somewhat conserved even during prolonged storage in air. The zirconium oxide discs without phosphate coating turn completely hydrophobic within these 19 days.

(85) Figures

(86) FIGS. 1a, 1b, and 1c show the surface morphology of zirconia discs with a phosphate coating of several micrometers (state of the art).

(87) FIGS. 2a, 2b, and 2c show the surface morphology of zirconia discs with an essentially monomolecular phosphate layer according to the present invention.