PROCESS FOR PROVIDING A DENTAL ARTICLE

Abstract

A process for providing a sterilized dental article, at least a portion of the surface of which exhibiting a contact angle of less than 45. The process includes the subsequent steps of a) providing a dental article and b) subjecting the initial dental article to a hydrogen peroxide plasma treatment. It is characterized in that the hydrogen peroxide plasma sterilization treatment of step b) is carried out in the presence of a carbon-containing compound, which during treatment is converted to form a carboxylic group attached to the surface of the dental article.

Claims

1. A process for providing a dental article, at least a portion of the surface of which exhibiting a contact angle of less than 45, the process comprising the subsequent steps of a) providing an initial dental article and b) subjecting the initial dental article to a hydrogen peroxide plasma treatment, wherein the hydrogen peroxide plasma treatment of step b) is carried out in the presence of a carbon-containing compound, which during treatment is converted to form a carboxylic group attached to the surface of the dental article.

2. The process according to claim 1, wherein in step b) the initial dental article is sterilized.

3. The process according to claim 1, wherein step a) includes the sub-step of a) placing the initial dental article in a holding container which is open in a manner such to allow hydrogen peroxide gas and plasma to get in contact with at least a part of the surface of the initial dental article.

4. The process according to claim 1, wherein in a further step c) the dental article obtained in step b) is packed in a packaging enclosing an interior space, said interior space being sealed from the outside space surrounding the packaging in a gas-tight manner.

5. The process according to claim 4, wherein the packing according to step c) is performed immediately after sterilizing according to step b).

6. The process according to claim 4, wherein step b) includes prior to the hydrogen peroxide plasma sterilization treatment the further sub-step of b) arranging the initial dental article, optionally placed in a holding container, in a sterilization container, which is closed and which comprises a membrane material that is permeable to hydrogen peroxide gas and plasma.

7. The process according to claim 6, wherein after the hydrogen peroxide plasma sterilization treatment the dental article is stored in the sterilization container.

8. The process according to claim 1, wherein the surface of the dental article obtained in step b) has a contact angle of less than 20.

9. The process according to claim 1, wherein the dental article is made of metal or ceramic.

10. The process according to claim 1, wherein the dental article is made of zirconia.

11. The process according to claim 1, wherein before step a) the surface of the dental article is subjected to a surface roughening treatment.

12. The process according to claim 11, wherein the surface roughening treatment comprises the steps of sandblasting the surface, followed by acid etching the sandblasted surface using an etching solution containing hydrofluoric acid.

13. The process according to claim 1, wherein the carbon-containing compound is present on the surface of the dental article.

14. The process according to claim 13, wherein the carbon-containing compound is present in the form of an adventitious contamination layer.

15. A dental article obtainable by the process according to claim 1, the surface of the dental article being at least partially functionalized with carboxylic groups attached thereto.

16. The dental article according to claim 15, the dental article being a component of a dental implant system.

17. The dental article system comprising A) a dental article according to claim 15, and B) packaging enclosing a packaging interior space in which the dental article is contained, said interior space being sealed from the outside space surrounding the packaging in a gas-tight manner.

18. The dental article system according to claim 17, wherein the packaging is at least partially made of transparent material.

19. A method of applying a hydrogen peroxide plasma treatment to improve the hydrophilicity of a dental article.

Description

EXAMPLES

[0093] Experiment 1

[0094] Disc-shaped samples of yttria-stabilized zirconia (MZ 111 of CeramTec GmbH) having a diameter of 5 mm and a thickness of 1 mm were treated according to the process described in EP-A-1 982 670 resulting in a surface of a structured topography and of a high hydrophilicity.

[0095] The samples were cleaned using oxygen plasma and packed in a sterilization container in the form of a peel bag, whereby Teflon rings were used as spacers for preventing a contact of the samples with the peel bag. The packed samples were then subjected to hydrogen peroxide plasma sterilization.

[0096] The samples (packed in the gas-permeable sterilization container) were not subjected to further packaging. After pre-determined periods of storage in the sterilization container, the contact angle of the samples was assessed.

[0097] The contact angles were determined using pure water according to the sessile drop method (EasyDrop DSA20E, Krss GmbH) using a drop size of 0.3 l. For each time point, three samples were assessed; per sample, one contact angle measurement was made. The contact angles were calculated by the so-called Circle Fitting method, i.e. by fitting a circular segment function to the contour of the droplet placed on the surface.

[0098] The contact angles determined as a function of the storage time are listed in Table 1.

TABLE-US-00001 TABLE 1 Contact angle of samples stored in sterilization container Mean Standard Sample 1 Sample 2 Sample 3 value deviation Storage Contact Contact Contact Contact Contact time [d] angle [] angle [] angle [] angle [] angle [] 10 2.5 4.7 3.5 3.6 1.1 38 4.1 5.1 4.0 4.4 0.6 76 3.9 4.6 5.1 4.5 0.6 117 5.3 4.3 6.5 5.4 1.1 187 6.4 5.2 5.5 5.7 0.6 278 9.9 0 0 3.3 5.7 376 15.8 0 0 5.3 9.1 556 22 31.3 72.8 42.0 27.0

[0099] As shown in Table 1, the samples sterilized with hydrogen peroxide plasma exhibited a superhydrophilicity with a contact angle of less than 10 even after a storage time of more than 1 year.

[0100] A first sub-set of samples was taken from the peel bag after 10 days of storage and subsequently stored in a well plate where it was exposed to air (sub-set A), whereas for a second sub-set storage in the well plate under air exposure started after 76 days instead of 10 days (sub-set B).

[0101] The respective contact angles measured after specified periods of storage in the well plate are given in Table 2 (for sub-set A) and Table 3 (for sub-set B).

TABLE-US-00002 TABLE 2 Contact angle of samples according to sub-set A Mean Standard Sample 1 Sample 2 Sample 3 value deviation Storage Contact Contact Contact Contact Contact time [d] angle [] angle [] angle [] angle [] angle [] 42 59.2 47.3 13.5 40.0 23.7 67 111.8 76.3 76 88.0 20.6 149 125.9 107.3 106.8 113.3 10.9

TABLE-US-00003 TABLE 3 Contact angle of samples according to sub-set B Mean Standard Sample 1 Sample 2 Sample 3 value deviation Storage Contact Contact Contact Contact Contact time [d] angle [] angle [] angle [] angle [] angle [] 12 8.7 7.9 10.5 9.0 1.3 39 72.4 54.2 72.5 66.4 10.5 69 86.6 74.9 90.1 83.9 8.0 111 114.8 99 108.7 107.5 8.0

[0102] Thus, after taking the samples from the sterilization container and exposing them to air, a fast increase in the contact angle (and, therefore, a decrease in the hydrophilicity) was determined after relatively short periods of storage.

[0103] Experiment 2

[0104] In further experiments, the samples described above were packaged in sterilization containers of different volumes.

[0105] For a first set (sample 2a), a sterilization container of smaller volume was used than for a second set (sample 2b). In addition, a set of machined samples was assessed (sample 2m), in contrast to the first two sets of samples (sample 2a and 2b), which have been treated according to the technology of EP-A-1 982 670.

[0106] After hydrogen peroxide plasma sterilization, the contact angles were determined after several periods of storage, using the same methods as for Experiment 1 above. The results are given in Table 4 below.

TABLE-US-00004 TABLE 4 Storage Sample 2a Sample 2b Sample 2m time Contact Contact Contact [weeks] angle [] angle [] angle [] 2 12.4 20.6 40.9 6 12.9 30.7 47.4

[0107] As shown in Table 4, the samples that have been treated and stored in the smaller sterilization container exhibit lower contact angles at relatively short storage times.

[0108] Experiment 3

[0109] Zirconia implants made of the material specified in the context of Experiments 1 and 2 above were placed in a sterilization container and were subjected to a hydrogen peroxide plasma sterilization treatment according to the present invention.

[0110] For three samples, the chemical composition of the thread portion was analysed by means of XPS after three months of storing.

[0111] For comparative reasons, samples, which have not been subjected to a hydrogen peroxide plasma treatment, but which apart from that correspond to the ones mentioned above, have been analysed using XPS (samples 3.1c.sub.1, 3.2c.sub.1 and 3.3c.sub.1). Further comparative examples (samples 3.1c.sub.2, 3.2c.sub.2 and 3.3c.sub.2) were prepared by subjecting samples to an ethylene oxide (EO) treatment instead of a hydrogen peroxide plasma treatment, but which apart from that correspond to the ones mentioned above.

[0112] XPS spectra were acquired on a PHI500 VersaProbe spectrometer (ULVAC-PHI INC.) equipped with a focused scanning monochromatic AlK.sub. source (1486.6 eV). The photoelectrons were detected at an angle of 45 to the surface normal. The measurements were performed with a spot size of 0.2 mm.

[0113] The results are given in Table 5.

TABLE-US-00005 TABLE 5 Atomic percentage of elements present on the surface of the samples determined by XPS Zr Y C O Si F Sample 3.1; H.sub.2O.sub.2-plasma treated 27.6 1.1 19.1 52.1 0.0 0.0 Sample 3.2; H.sub.2O.sub.2-plasma treated 26.5 1.1 21.5 50.3 0.0 0.6 Sample 3.3; H.sub.2O.sub.2-plasma treated 27.3 1.1 20.3 51.3 0.0 0.0 Sample 3.1c.sub.1; non-treated (comp.) 22.5 0.8 34.7 41.2 0.9 0.0 Sample 3.2c.sub.1; non-treated (comp.) 27.0 1.1 23.0 48.9 0.0 0.0 Sample 3.3c.sub.1; non-treated (comp.) 27.7 1.1 20.8 50.4 0.0 0.0 Sample 3.1c.sub.2; EO-treated (comp.) 26.3 1.1 21.3 51.3 0.0 0.0 Sample 3.2c.sub.2; EO-treated (comp.) 25.6 0.9 24.8 48.7 0.0 0.0 Sample 3.3c.sub.2; EO-treated (comp.) 25.8 1.0 27.7 45.5 0.0 0.0

[0114] Also, the contact angles of both the samples treated according to the present invention and the comparative samples have been determined using DCA measurements.

[0115] To this end, the advancing water contact angle was tensiometrically examined by the Wilhelmy method by means of a tensiometer (Lauda TE 3, Lauda Dr. R. Wobser GmbH & Co. KG). The resulting contact angles are given in Table 6.

TABLE-US-00006 TABLE 6 Contact angle measurement Contact angles [] Sample 3.1; H.sub.2O.sub.2-plasma treated 0.0 Sample 3.2; H.sub.2O.sub.2-plasma treated 0.0 Sample 3.3; H.sub.2O.sub.2-plasma treated 0.0 Sample 3.1.sub.C1; non-treated 100.1 (comp.) Sample 3.2.sub.C1; non-treated 114.7 (comp.) Sample 3.3.sub.C1; non-treated 115.3 (comp.) Sample 3.1.sub.C2; EO-treated 87.8 (comp.) Sample 3.2.sub.C2; EO-treated 77.4 (comp.) Sample 3.3.sub.C2; EO-treated 86.1 (comp.)

[0116] As shown in Table 6, the process of the present invention leads to superhydrophilic samples, whereas the comparative samples remain hydrophobic.

[0117] Table 7 shows the proportion of functional groups, in which the carbon atoms are present, for the samples according to the present invention in comparison to the non-treated samples:

TABLE-US-00007 TABLE 7 C1s C1s C1s CC CO COO Sample 3.1; H.sub.2O.sub.2-plasma treated 67.8 14.2 18.0 Sample 3.2; H.sub.2O.sub.2-plasma treated 67.4 16.3 16.4 Sample 3.3; H.sub.2O.sub.2-plasma treated 62.7 17.6 19.7 Sample 3.1.sub.C1; non-treated 78.3 14.8 6.9 (comp.) Sample 3.2.sub.C1; non-treated 74.6 15.8 9.5 (comp.) Sample 3.3.sub.C1; non-treated 72.7 16.0 11.3 (comp.)

[0118] As shown in Table 5, the content of carbon in the samples according to the present invention and in the samples according to the comparative example are comparable. However, the content of carboxyl groups is much higher for the samples of the present invention compared to the non-treated samples, as shown in Table 7. This higher content of carboxyl groups has been shown to go along with a higher hydrophilicity.

[0119] The higher proportion of carboxyl groups in the samples of the present invention is at the cost of the proportion of alkane groups, the proportion of carbonyl groups being comparable for the samples according to the present invention and the non-treated comparative samples.

[0120] Experiment 4

[0121] In further experiments, the influence of a typical holding container of a dental article, specifically of a blister of a dental implant, on the dental article's hydrophilicity was assessed.

[0122] To this end, six samples (4.1 to 4.6) of the same material and topography as specified in Experiment 1 above were, after oxygen plasma cleaning, arranged in a Teflon insert and placed in a blister used for SLA implants (from Institut Straumann AG) before being packaged in a sterilization container in the form of a Tyvek bag under laminar flow. The samples were then subjected to hydrogen peroxide plasma sterilization.

[0123] The development of the contact angle as a function of the storage time is given in Table 8.

TABLE-US-00008 TABLE 8 Sample Sample Sample Sample Sample Sample Mean 4.1 4.2 4.3 4.4 4.5 4.6 value Standard Storage Contact Contact Contact Contact Contact Contact Contact deviation time angle angle angle angle angle angle angle Contact (weeks) [] [] [] [] [] [] [] angle [] 3 0.0 9.6 20.9 0.0 14.0 0.0 7.4 8.9 6 10.4 0.0 0.0 27.8 0.0 6.2 7.4 10.9 11 16.8 0.0 0.0 0.0 13.5 0.0 5.1 7.9 18 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

[0124] As shown in Table 8, the samples treated according to the present invention were superhydrophilic exhibiting a contact angle of less than 10 even after storage for 18 weeks.

[0125] Experiment 5

[0126] For comparative reasons, a further set of samples was treated using plasma techniques other than hydrogen peroxide plasma sterilization. Specifically, sample discs of the same material and surface topography as mentioned, but having a diameter of 15 mm and a thickness of 1.2 mm were placed in a sterilization container in the form of a Tyvek bag. A first set of samples was treated using an 02 plasma device generating a harsh plasma with a high kinetic input (Tepla) and a second set was treated using an ArH.sub.2 plasma device generating a moderate plasma (UCP).

[0127] The characteristics of the devices used are given in Table 9 below.

TABLE-US-00009 TABLE 9 Flux Power Time Device Gas [sccm] [W] [min] Tepla O.sub.2 100 200 25 UCP ArH.sub.2 100 500 25

[0128] After 3 weeks and 6 weeks of storage, the contact angle was measured using the methods given above. The mean values of the measurements (ten samples for each the first and the second set) as well as the standard deviation are given in Table 10.

TABLE-US-00010 TABLE 10 O.sub.2 Plasma ArH.sub.2 Plasma Mean Standard Mean Standard value of deviation value of deviation Storage contact of contact contact of contact [weeks] angle [] angle [] angle [] angle [] 3 84.0 48.2 80.0 29.5 6 108.9 14.3 98.9 18.1

[0129] As evidenced in Table 10, all the samples that were treated using O.sub.2 plasma or an ArH.sub.2 plasma became hydrophobic within a relatively short storage period, exhibiting contact angles of about 100 or higher after 6 weeks. Thus, the effect achievable by the hydrogen peroxide plasma sterilization treatment, namely an improved hydrophilicity and a high storage stability of the hydrophilicity, were not achieved using the alternative plasma sterilization treatments.

[0130] Experiment 6

[0131] Samples as described in Experiment 1 were after the treatment according to the technology of EP-A-1 982 670 stored in a glass dish with a cover.

[0132] After 4.5 months of storage, the contact angles were measured using the sessile drop method described in the context of Experiment 1.

[0133] The samples were then packed in a Tyvek bag and subjected to hydrogen peroxide plasma sterilization.

[0134] Twelve days after hydrogen peroxide plasma sterilization, the contact angles were again measured.

[0135] With regard to the contact angle measurements, 5 samples (6.1 to 6.5) were analysed before sterilization and 10 samples (6.1 to 6.10) were analysed after sterilization (i.e. the 5 samples that were analysed prior to sterilization and 5 further samples). For the measurements before sterilization, a drop size of 0.3 l was used, while for the measurements after sterilization a drop size of 0.1 l was used. In both cases, the contact angles were calculated by the Circle Fitting method (see Experiment 1).

[0136] The results of the contact angle measurement are shown in Table 11.

TABLE-US-00011 TABLE 11 Contact Contact angle before angle after sterilization sterilization [] [] Sample 6.1 125.3 6.6 Sample 6.2 136.2 7.9 Sample 6.3 124.6 5.7 Sample 6.4 118.2 5.9 Sample 6.5 127.1 9.5 Sample 6.6 13.0 Sample 6.7 6.4 Sample 6.8 5.1 Sample 6.9 7.4 Sample 6.10 13.5 Mean value 126.3 8.1 Standard 6.5 3.0 deviation

[0137] As shown in Table 11, the process of the present invention led to a considerable increase in the hydrophilicity of the samples. Specifically, hydrophobic surfaces were transformed into superhydrophilic surfaces by the process of the invention.

[0138] Regarding the sterile dental article system of the present invention, the concept is further illustrated by means of attached

[0139] FIG. 1 showing a dental article system comprising a dental article and a packaging enclosing an interior space, in which the dental article is arranged.

[0140] As shown in FIG. 1, a dental article 10 in the form of a dental implant 100 is placed in a holding container 12 and, in this form, arranged in a sterilization container 14. The sterilization container 14 containing the dental implant 100 arranged in the holding container 12 is again arranged in a packaging 16 enclosing an interior space 18, which is sealed from the outside space surrounding the packaging in a gas-tight manner.

[0141] When carrying out the process of the present invention, an initial dental implant 100 is in a first step placed in the holding container 12, allowing the initial dental article to be held safely in place. In a second step, the holding container 12 with the dental implant 100 placed therein is enclosed in the sterilization container 14 and, in this form, is subject to hydrogen peroxide plasma treatment. In order for the hydrogen peroxide gas and plasma get into contact with the dental implant's surface, the sterilization container 14 is at least partially made of a gas-permeable membrane material.

[0142] Due to the adventitious contamination layer formed on the initial dental implant, carbon-containing compounds are present, which during the hydrogen peroxide plasma treatment are converted to form a carboxylic group attached to the surface of the dental implant 100, ultimately giving rise to a high long-term hydrophilicity.

[0143] Finally, the sterilizing container 14 enclosing the holding container 12 with the treated dental implant 100 is enclosed in the packaging 16 whichowed to the fact that it is sealed in a gas-tight mannerprevents the sterilizing container 14 and ultimately the dental implant 100 from being contaminated, which further contributes to the high hydrophilicity to be maintained over a long term.

[0144] Alternatively to packing the sterilizing container 14 in a separate packaging, a gas-tight interior space can also be achieved by covering the permeable parts of the sterilization container 14 using e.g. a gas-impermeable foil or sheet.