T 1025/10 05-06-2014

Reasons for the Decision

Status of the opponent

1. In line with the case law the opponent, which was the respondent to the appeal of the patent proprietor, by virtue of the withdrawal of the opposition ceased to be party to the appeal proceedings in respect of the substantive issues. However, the status of the opponent as a party to the proceedings is unaffected as far as the question of apportionment of costs under Article 104 EPC is at issue (see T 789/89, OJ 1994, 482).

Admission of documents D11 to D14

2. After the Board indicated in the communication sent in preparation of the oral proceedings that no evidence was available on the side of the appellant to show that improvements with respect to the closest prior art represented by document D2 were achieved, the appellant filed documents D11 to D14 in order to provide the missing evidence.

2.1 Documents D11 to D14 indeed concern the central issue of hydrolysis stability for compositions comprising bisacrylamides. The Board has no difficulty in understanding the tests provided therein and there is no other party to the proceedings which would require further time to provide counter-arguments.

2.2 On that basis the Board finds it appropriate to exercise its discretion under Article 13 RPBA by admitting documents D11 to D14 into the proceedings.

Main request - amendments

3. The issue under Article 123(2) EPC on which the main request fell in opposition proceedings does not need to be decided upon, because the main request is not allowable for the reasons set out below (points 4 to 6).

Main request - inventive step

4. Closest prior art

4.1 Document D2 was chosen as the closest prior art both in the decision under appeal and in the arguments of the appellant. The Board has no reason to choose a different starting point.

4.2 Document D2 discloses a dental resin cement material comprising a filler, a polymerizable resin, a polymeric handling modifier and a polymerization initiator (claim 1). If desired, the composition can contain adjuvants such as pigments (page 19, lines 12 to 14) and optionally it may contain stabilizers (page 19, lines 14 and 15).

4.3 As to the polymerizable component several compounds are disclosed (page 10, line 7 to page 16, line 13). Preferred polymerizable components can be substituted acryl amides and methacrylamides, examples of which are methylene bisacrylamide and methylene bismethacrylamide (page 12, lines 6 to 8). Mixtures of polymerizable material are also contemplated (page 16, lines 11 to 13).

4.4 On that basis the dental composition of claim 1 of the main request differs from the disclosure in D2 in that the bisacrylamides are substituted at the two nitrogen positions (R1 is a substituted or unsubstituted C1 to C18 alkyl, but not a hydrogen as in the bisacrylamides mentioned in D2) and that in addition to the bisacrylamide, the filler and the initiator, a second monomer, a stabilizer and pigments are necessarily present (all ingredients are mentioned individually in D2, but not necessarily in the combination as claimed in claim 1 of the main request).

4.5 This analysis has been agreed by the appellant.

5. Technical problem solved

5.1 The patent focuses on the problems of the conventional methacrylates used for dental applications, whose hydrolysis under acidic or basic conditions frequently leads to long-term failure (paragraph [0002] of the granted patent). Indeed it has been the central argument of the appellant in the analysis of inventive step that the use of bisacrylamides in the claimed composition leads to improved hydrolysis stability.

5.2 As the closest prior art already discloses the use of bisacrylamides, it needs to be determined whether the evidence on file permits an improvement in hydrolysis stability to be acknowledged as a consequence of the replacement of the bisacrylamides mentioned in D2 (not substituted at the nitrogen atoms) with the bisacrylamides in claim 1 of the main request (substituted at both nitrogen atoms). The evidence cited in this respect by the appellant is constituted by documents D11 to D14.

5.2.1 Document D11 analyses the hydrolysis stability of several dental compositions (abstract and table 1) and compares the storage stability of commercial products (page 8, second column, "Storage Stability"), including AdheSE One F and Xeno V, both containing bisacrylamides (table 1, composition). According to D11, the results of the test show that methacrylamide-based adhesives are stable to aqueous acid and exhibit much superior storage stability than conventional methacrylate-based adhesives (abstract, "Conclusions").

5.2.2 Document D11, however, does not give any detail on the chemical structure of the bisacrylamides used in the tested commercial products and does not provide a comparison between bisacrylamides with different structures (in particular substituted at the nitrogen and unsubstituted). Even assuming, as alleged by the appellant, that the bisacrylamides in the commercial product Xeno V (produced by the appellant) fall under the chemical formula given in claim 1 of the main request, no conclusion over D2 can be reached without a comparison between the bisacrylamides disclosed in D2 and those indicated in the claim, which is entirely missing in D11.

5.2.3 Documents D12, D13 and D14 concern experiments undertaken to analyse the hydrolysis stability of several bisacrylamides stored for several days in bottles opaque to light at 37° under acidic conditions.

5.2.4 D12 concerns methylene bisacrylamide (one of the bisacrylamides mentioned in D2) and shows that after 4 weeks the purity has decreased by 11.6% (page 2, table 2 and first paragraph). According to D2 this is due to the length of the chain between the two nitrogen atoms (R2 in the formula of claim 1), as it is stated that methylene bisacrylamide has a lower hydrolysis stability than analogous bisacrylamides with longer spacer groups (page 2, last sentence).

5.2.5 Indeed, this consideration is confirmed by the results in D13. Ethylene bisacrylamide (compound V-398, according to D13, table 1), which differs from methylene bisacrylamide only in that the spacer is an ethylene instead of a methylene (a chain with two carbon atoms instead of a chain with a single one), has a decrease in purity of only 1.5% after 20 days (table 3 in D13) and no hydrolysis products are identified after this period (table 4 in D13).

5.2.6 In D13 a comparison is also offered between two bisacrylamides which differ only in the presence of alkyl substituents at the nitrogen atoms, namely ethylene bisacrylamide (compound V-398, according to D13, table 1) and di-isopropyl ethylene bisacrylamide (compound V-724, according to D13, table 1). While V-398 has a decrease in purity of 1.5% after 20 days at storage conditions, the decrease in purity is of 3% for V-724, showing that the unsubstituted bisacrylamide is better than the substituted one in this respect. According to D13 no hydrolysis products were identified after 20 days in both cases (Table 4).

5.2.7 No other comparison between bisacrylamide unsubstituted at the nitrogen atoms and the corresponding substituted ones is offered by D13. Indeed other substituted bisacrylamides are tested (V-439, V-392, V-440 in table 1), all including a longer spacer group (C3 or C6), but there is no information on the corresponding unsubstituted bisacrylamides, so that a comparison is not possible. If at all, these tests can only confirm that all bisacrylamides with a spacer longer than a simple methylene are more storage stable than the methylene bisacrylamide (tables 3 and 4).

5.2.8 D14 includes the same results as D13 in term of hydrolysis stability (see D13 and D14, pages 1 and 2).

5.2.9 The evidence in D12 to D14 therefore does not support the allegation of the appellant that the introduction of alkyl substituents at the nitrogen atoms improves the hydrolysis stability of the bisacrylamide. On the contrary, the only comparison which is available shows that the decrease in purity after 20 days is lower for the unsubstituted bisacrylamide than for the substituted one (see point 5.2.6, above). Moreover, the tests show that the crucial parameter for the storage stability is the length of the spacer group and that unsatisfactory results are obtained with a methylene spacer.

5.2.10 As the bisacrylamides comprised in the claimed composition include those with a methylene group (R2 can be a C1 alkylene) and differ from those of D2 only in the presence of an alkyl substituent at the nitrogen atoms, it cannot be acknowledged in view of the evidence on file that their hydrolysis stability is improved or even maintained with respect to the bisacrylamides of D2.

5.3 As to the specific combination of ingredients of claim 1 of the main request, no effect or advantage was claimed to be present by virtue of it. Indeed the appellant acknowledged that, while in the case of the presence of an amine in appropriate amounts a Micheal type polymerization takes place, the claim includes embodiments with an initiator and without an amine, in which a free radical polymerization takes place, as is the case for the composition of D2.

5.4 In the absence of effects or advantages which can be acknowledged over the composition known from the closest prior art, the problem solved by the subject-matter of claim 1 of the main request with respect to the disclosure of D2 is the provision of a further dental composition.

6. Obviousness of the solution

6.1 The skilled person starting from the compositions of D2 and looking for further dental compositions would find the addition of optional ingredients explicitly mentioned in D2 in all possible combinations as an obvious measure to solve the posed problem.

6.2 Similarly the arbitrary choice of slightly different bisacrylamides (i.e. those with an alkyl substituent at the nitrogen atoms) with respect to the ones mentioned in D2 would be an obvious measure while looking for further dental compositions. In this respect it is relevant to note that the appellant never claimed that the substituted bisacrylamides were not known, as is confirmed for instance by document D6 (table 1, last two chemical formulas).

6.3 On that basis the subject-matter of claim 1 of the main request does not involve an inventive step.

Admission of the auxiliary request

7. After the Board indicated in the communication sent in preparation of the oral proceedings that the Board had difficulties in accepting the amendment of the term "alkylene" to "alkyl", as there were two possible corrections of the mistake in the original application which were not equivalent, the appellant filed an auxiliary request in which the definition of R1 was limited to a substituted C1 to C18 alkyl with the argument that this was covered by the two possible corrections of the obvious mistake.

7.1 The filing of the request was done as soon as possible after the appellant understood the reasons why the Board was inclined not to accept the amendment of the term "alkylene" to "alkyl" and included only a clear limitation of the definition of R1 (from "a substituted or unsubstituted C1 to C18 alkyl" to "a substituted C1 to C18 alkyl"). Moreover, the Board has no difficulty in analysing the amended request.

7.2 On that basis the Board finds it appropriate to exercise its discretion under Article 13 RPBA by admitting the auxiliary request into the proceedings.

Auxiliary request - inventive step

8. No additional arguments were provided by the appellant for the inventiveness of claim 1 of the auxiliary request with respect to claim 1 of the main request, as the only amendment which was introduced was related to the objection under Article 123(2) EPC which formed the basis of the decision of the opposition division and which had been preliminarily maintained in the communication of the Board.

8.1 The same analysis of inventive step as detailed for the main request (points 4 to 6) equally applies to claim 1 of the auxiliary request, whose subject-matter does not involve therefore an inventive step.

Apportionment of costs

9. While the notice of opposition contained an objection of lack of inventive step for granted claim 1 with respect to document D2 as the closest prior art and acknowledged the difference therefrom in the bisacrylamides used in granted claim 1 in view of the presence of substituents at the nitrogen atoms which were not hydrogen atoms, there were no tests on file analysing the effects related to such a difference until one month before the oral proceedings before the opposition division. At that point the opponent filed some test results in the form of document D5 to show that the presence of the substituents did not have any impact on the hydrolysis stability of the claimed composition (D5, page 3, section 3). The reproducibility of these tests was put into question by further tests included in document D7 filed by the appellant at the oral proceedings before the opposition division (D7, last paragraph, "Feststellung"). Further evidence regarding the reproducibility of the tests in D5 was filed by the parties in appeal (the opponent filed D8, see point VIII, above; the appellant filed D9 and D10, see point IX, above).

9.1 The analysis of inventive step undertaken in the current decision (see points 4 to 6, above) shows that the availability of tests meant to show possible effects and advantages related to the replacement of hydrogen with alkyl substituents at the nitrogen atoms was the decisive point in the determination of inventive step (see point 5.2, above). This was the case since the beginning of the opposition proceedings, since the current analysis takes as starting point the document used for lack of inventive step in the notice of opposition (document D2) and identifies the presence of the substituents at the nitrogen atoms as the crucial difference (see points 4.4 and 5.1, above) as was the case in the notice of opposition.

9.2 As alleged advantages to which the patent proprietor merely refers without offering sufficient evidence to support the comparison with the closest prior art, cannot be taken into consideration in determining the problem effectively solved by the claimed subject-matter (Case Law of the Boards of Appeal of the EPO, 7th edition 2013, I.D.4.2), the onus had been on the appellant since the start of the opposition proceedings to show that improvements were achieved by means of the difference in structure, in the absence of which the problem with respect to D2 was simply that of providing a further composition. In this respect the filing of D5 by the opponent, which was meant to show that no improvement was present, did not change the situation with respect to the absence of tests, in that also before the availability of these tests no improvement could be acknowledged, nor did it shift the burden of proof, which already lay with the appellant.

9.3 Under these circumstances it was not necessary for the appellant to show that the opponent's experiments were not reworkable, but it was necessary to file tests which showed the occurrence of the effects the appellant alleged to be present. Reworking the opponent's tests was not a necessary means of defence, because D5 had no bearing on the case, as long as the appellant had not shown any advantage.

9.4 Moreover, the fact that the experts of the two parties did not agree on what happened while performing these tests corresponds to the not uncommon situation in which technicians of the opposing parties come to apparently contradictory results. This cannot however be considered as conclusive evidence of a malicious or abusive nature of the tests of the opponent.

9.5 As a consequence the Board fails to see any reason of equity which would justify a different apportionment of costs (Article 104(1) EPC). For these reasons the request that the opponent be apportioned the costs incurred for the experimental efforts undertaken by the appellant is rejected.