EP 3 013 306 B1 relates to nanocrystalline zirconia and methods of processing thereof, used in dental restorations.
Brief outline of the case
The proprietor and the joint opponents appealed maintenance on the basis of AR 4.
The bord revoked the patent for lack of sufficiency of all requests on file.
The opponents’ point of view
Regarding the grain size distribution, claim 1 contained no hint which measurement method should be used. The description suggested several options, namely ASTM E112, SEM or XRD. The values reported in Table 2 using SEM or XRD varied by a factor of about 2. ASTM E112 mentioned different methods for determining the average grain size, and stated that the test methods shown therein referred to the characterization of two-dimensional grain size sections, whereas in claim 1 a grain size by volume was claimed. This feature was thus not enabled.
The patent did not teach how to determine the theoretical density and thus the relative density for materials other than 3 mol% yttria containing zirconia. Considering that paragraph [0041] belonged to the example section of the patent, the person skilled in the art would understand that the density of 6.08 g/cm3 cited therein was to be used only for the materials used in the examples. The use of this fixed value for the theoretical density would lead to results which did not technically make sense. Different kinds of zirconia materials have different theoretical densities, depending on e.g. crystal phase content, additives, or stabiliser content.
Accordingly, the criteria of sufficiency of disclosure were not met.
The proprietor’s point of view
Having regard to grain size, the patent indicated that the intercept method according to ASTM E112-12 was used to determine the average grain size and the grain size distribution. The claimed grain size per volume could be inferred from the ASTM E112-12 measurement, or determined by measuring several planar sections.
For the proprietor, the planar method must allow to infer a three-dimensional size and therefore also a volume distribution.
Regarding relative density, the patent clearly indicated that relative density of claim 1 was calculated on the basis of a theoretical density value of 6.08 g/cm3.
The board’s decision
The Board came to the conclusion that both the grain size distribution and the relative density are essential for the achievement of the claimed effect of opalescence, and that the indetermination of the measurement/calculation methods for both parameters leads to a lack of sufficient disclosure.
Grain size
Several methods for the determination of average grain sizes are mentioned in the patent, namely the intercept method according to ASTM E112-12, ASTM E112 or EN 623-3.
Firstly, the method proposed by the proprietor, ASTM E112-12 is only mentioned in the patent as a method for measuring an average grain size, i.e. a single value for the sample.. In contrast, claim 1 defines a grain size distribution, i.e. the proportion of grains whose individual sizes are within the claimed range.
An average grain size provides no information on grain size distribution. The proprietor did not substantiate their claim that the same ASTM E112 method can also be used for grain size distribution.
Secondly, the ASTM E112 standard states explicitly that its test methods “deal only with determination of planar grain size, that is, characterization of the two-dimensional grain sections revealed by the sectioning plane.
Determination of spatial grain size, that is, measurement of the size of the three-dimensional grains in the specimen volume, is beyond the scope of these test methods. In contrast, claim 1 does not define a planar grain size, but a distribution of grain sizes by volume.
Relative density
Claim 1 requires the zirconia to have a density of at least 99.5% of theoretical density. The calculation of this parameter thus requires a determination of the theoretical density of the zirconia at hand.
In spite of pending referral G 1/24, the board however considered that, irrespective of the answer to be given in G 1/24, the present description does in any case not contain a generally applicable definition, or similar information, for the expression “theoretical density“.
There is no indication in the patent that the density of 6.08 g/cm3cited in paragraph [0041] is destined to apply to materials other than the examples and be generally applicable to all zirconia materials covered by claim 1.
Furthermore, the use of this fixed value would lead to the surprising outcome that materials with high density have relative densities over 100%, and negative porosities, which is an essential parameter for obtaining the claimed opalescence.
Consequently, the board considered that, even if the skilled person were to turn to the description to interpret “theoretical density“, this would not help because this passage of the description is not of general application and leads to inconsistent results for some materials.
Claims 1 and 15 in each of AR 1-10 contain the same features pertaining to grain size distribution by volume, relative density and opalescence. The same conclusion applies.
Comments
It is not infrequent that some boards consider that, in the absence of a measurement method for a parameter, it is a mere problem of clarity which cannot be raised in opposition, other than under G 3/14.
Other boards consider that the absence of a measurement method for a parameter is a problem of lack of sufficiency.
A list of decisions showing the divergent case in this matter, is to be found in the comments section on my blog on T 1530/22.
The present decision is in line with T 1845/14.
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