T 1718/18 12-08-2020

I. The opponent (appellant) filed an appeal against the opposition division's interlocutory decision finding that, on the basis of the main request, the patent in suit (hereinafter "the patent") met the requirements of the EPC.

II. Oral proceedings before the Board were held by video conference - as requested by both parties - on 12 August 2020.

III. At the end of the oral proceedings, the relevant requests were as follows:

The appellant (opponent) requested that the decision under appeal be set aside and that the European patent No. 2 528 536 be revoked.

The respondent (patent proprietor) requested that the appeal be dismissed and the patent maintained as upheld by the opposition division (main request) or that the patent be maintained on the basis of one of auxiliary requests 1 to 3 from the first-instance proceedings, or auxiliary request 4 submitted with the reply to the grounds of appeal dated 15 January 2019, in combination with the adapted description filed during the oral proceedings.

IV. Independent claims

Claim 1 of the main request, with the feature designations of the impugned decision, reads:

A1|"A dental strip (10) comprising: |

A2|a film backing, and |

A3|an adhesive layer on one surface of the film backing, |

A4|wherein the film backing is detachable from the adhesive layer, |

|characterised in that |

A5|the adhesive layer comprises a water-swellable polymer and at least one active agent."|

V. Claim 1 of the first auxiliary request differs from claim 1 of the main request in that the following wording has been added:

"... , wherein the adhesive layer is capable of expanding and infiltrating spaces between teeth on contact with saliva."

VI. Claim 1 of the second auxiliary request differs from claim 1 of the main request in that the following wording has been added:

"..., wherein the active agent comprises a plaque-reducing agent."

VII. Claim 1 of the third auxiliary request combines the amendments made in the first and second auxiliary requests.

VIII. Claim 1 of the fourth auxiliary request differs from claim 1 of the second auxiliary request in that the following wording has been added:

"..., and wherein the water-swellable polymer further includes an effervescent substance that effervesces on contact with water or saliva."

IX. The following documents are of relevance to the decision:

D4 |US 6,343,932 B1 |

D6 |WO 2006/085017 A2 |

D7 |WO 98/55079 |

D8 |WO 2007/076396 |

D12|US 6,153,222 A |

D15|H. Omidian et al. "Swelling and Crosslink Density Measurements for Hydrogels", Iranian Journal of Polymer Science and Technology, Vol. 3 No. 2, 1994, pages 115-119 |

D16|S. Durmaz et al. "Swelling and Mechanical Properties of Solution-Crosslinked Poly(isobutylene) Gels", Macromolecular Chemistry and Physics, Vol. 203, 2002, pages 663-72 |

D17|A. Martínez-Ruvalcaba et al. "Swelling characterisation and drug delivery kinetics of polyacrylamide-co-itaconic acid/chitosan hydrogels", eXPRESS Polymer Letters Vol. 3 No. 1, pages 25 to 32, 2009 |

D18|J. Metz et al., Abstract of "Effect of crosslinking density of swelling and mechanical properties of PEGDA400/PCLTMA900 hydrogels", 43rd Annual Rocky Mountain Bioengineering Symposium and 43rd International ISA Biomedical Sciences Instrumentation Symposium Vol. 464, 2006|

D20|Lubrizol Technical Data Sheet, 16 September 2009 |

D21|P. J. Flory, "Principles of polymer chemistry", Ithaca; Cornell University Press, 1953, pages 584 to 588 |

D22|Dr T. Englin, Experimental Report of "Carbopol 981 NF Gel Formation and Water Uptake Experiment" dated 9 November 2017 |

X. The appellant argued essentially the following:

Sufficiency of disclosure

The patent did not set out any test for the skilled person to determine whether a given polymer was water-swellable or not. This was exemplified when trying to distinguish between a water-swellable or a water-swollen polymer, which described the same material. The patent did not define any parameters by which the skilled person could tell if a polymer was swellable, partially swollen or fully swollen. There was no agreement on a standard test either.

Furthermore, the patent did not state the properties of the film backing and the adhesive layer which rendered the film backing layer detachable. Additionally, according to paragraph [0033] of the patent in suit, in one embodiment the film backing remained attached to the adhesive layer.

The invention was thus not sufficiently disclosed for it to be carried out by the skilled person.

Main request - novelty

The subject-matter of claim 1 was not novel over the dental strip disclosed in D4.

Feature A5 did not require the adhesive layer to be homogeneous or to have the same properties across its thickness. The core 12 and the gel 16, which contained an active agent, together formed a layer having substantially the same thickness over the entire width of the dental strip, both where the gel was present and where it was not. The gel and the core were both described as being somewhat tacky. They thus formed an adhesive layer within the meaning of claim 1 of the patent in suit, in particular since paragraph [0024] of the patent described that the adhesive layer could be coated with the active agent; the claim thus covered an essentially two-layer construction of the adhesive layer.

Both the core and the gel comprised Carbopol, which was listed in the patent as an example of a water-swellable polymer. This term could not be read as being limiting since the patent did not contain any qualification or test for what qualified as a water-swellable polymer. D15 to D18 showed that there was no standard definition of water-swellability.

The experiment described in D22 showed that, even in a diluted state, the gel used in D4 had the capacity to take up water and swell further. As shown in D20, it was known to the skilled person that an over-neutralisation led to a rapid drop in viscosity, which they would make sure to avoid. The peroxide used as the whitening agent in the gel did not neutralise the polymer and thus did not influence its water-swellability. Finally, since the gel had high viscosity and was tacky, it could not be fully saturated with water. It was therefore implicit that the gel in D4 could take up water and expand during use.

Furthermore, the core - which was freeze-dried - contained Carbopol, which would take up water and swell during use.

The adhesive layer formed by the combination of the core and the gel thus formed an adhesive layer according to feature A5.

In conclusion, the subject-matter of claim 1 of the main request was not novel.

First auxiliary request - novelty

Since the adhesive layer of the dental strip in D4 absorbed water during use, it would inevitably expand and infiltrate the spaces between the teeth upon contact with saliva.

The subject-matter of claim 1 of the first auxiliary request was thus not novel either.

Second and third auxiliary requests - inventive step

The subject-matter of claim 1 of the second and third auxiliary requests differed from the dental strip in D4 in that the active agent comprised a plaque-reducing agent.

This difference solved the problem of providing an alternative dental strip or the problem of providing a strip which reduces plaque.

D4 itself suggested that other active agents could be substituted for the whitening agent.

Plaque-reducing agents were among the most common active agents for dental strips, as shown in e.g. D7, page 13.

It would thus be obvious for the skilled person to substitute the whitening agent of the dental strip in D4 for a plaque-reducing agent in order to solve the problem posed.

Consequently, the subject-matter of claim 1 of the second and third auxiliary requests did not involve an inventive step.

Fourth auxiliary request - added subject-matter, inventive step and adaptation of the description.

Claim 1 of the fourth auxiliary request combined features of two unrelated and distinct embodiments found in paragraphs [0025] and [0028] of the original application, thus leading to an extension of the subject-matter of claim 1 beyond the content of the application as originally filed.

The subject-matter of claim 1 did not involve an inventive step either.

The subject-matter of claim 1 of the fourth auxiliary request differed from the dental strip in D4 in that the active agent was a plaque-reducing agent and possibly in that the polymer further included an effervescent substance.

The patent did not provide any evidence of an improved, more effective or deeper delivery due to this combination. These differences therefore had no synergistic effect and only solved partial problems. The substitution of a plaque-reducing agent for the whitening agent was obvious to the skilled person for the reasons set out with respect to the second and third auxiliary requests.

The inclusion of an effervescent substance solved the problem of providing an alternative dental strip. The use of such substances in oral products comprising water-swellable polymers was known from D12, column 2, lines 13 to 20, which described the effect of the effervescent substance in the same wording as the patent. It would therefore have been obvious for the skilled person to include effervescent substances in the polymer in D4 in order to solve the problem posed.

The skilled person would thus arrive at the claimed dental strip without any inventive skill.

Alternatively, the skilled person would replace some, but not all, of the peroxide of the dental strip D4 with a plaque-reducing agent, or they would simply add the plaque-reducing agent. While D4 did not disclose a combination of active agents, it did not discourage it either. It was generally known that mixtures of active agents could be used, as evidenced by e.g. D7. The respondent did not demonstrate prejudice against combining hydrogen peroxide with plaque-reducing agents. For the reasons already given, it would be obvious for the skilled person to use a plaque-reducing agent in the dental strip in D4. The remaining peroxide was an effervescent substance, and so the skilled person would also arrive at the claimed subject-matter without any inventive skill.

The description was not adapted to the claims. Paragraph [0023] should explicitly exclude the possibility of the effervescent substance being hydrogen peroxide since this had been argued by the respondent in the inventive-step discussion; without that exclusion the subject-matter was not inventive. Furthermore, all paragraphs mentioning the active agent should be amended to state that the active agent was a plaque-reducing agent.

XI. The respondent argued essentially the following:

Sufficiency of disclosure

Water-swelling polymers were well known (see e.g. D21) and could be clearly identified by the skilled person. The patent described the properties and behaviour of swellable materials in paragraph [0021]. The skilled person could therefore identify whether or not a polymer was water-swellable without undue burden. Additionally, paragraph [0022] provided a list of suitable materials.

Furthermore, the skilled person could easily verify whether a film backing was detachable or not simply by handling the dental strip. Suitable film backings were mentioned in paragraphs [0012] to [0015]. The editorial inconsistency between the claims and paragraph [0033] was, if anything, an issue of Article 84 EPC and not a ground for opposition.

The invention was therefore sufficiently disclosed for it to be carried out by the skilled person.

Main request - novelty

The coating used in the manufacturing method described in paragraph [0024] of the patent in suit did not form a separate element since it was absorbed by the adhesive, in contrast with the solution used for forming the film backing as described in paragraph [0016] of the patent. The strip disclosed in D4 had a core and a gel which were two separate physical elements. The gel could even be supplied separately in a tube and be applied to the core by the user. The core and the gel of D4 thus could not be one adhesive layer within the meaning of the claim.

Furthermore, the gel of the dental strip in D4 was not water-swellable in the correct interpretation of the term, which should take the whole disclosure of the patent in suit into account. Paragraph [0001] of the specification described the disadvantage of the prior-art substrates as being that the treatment was generally limited to the tooth surface and did not infiltrate between the teeth. Paragraphs [0004], [0005] and [0034] described that the adhesive layer of the dental strip of the patent in suit did expand and infiltrate between the teeth. On the other hand, paragraph [0031], which concerned a non-claimed oral treatment method, was not relevant for construing the term water-swellable. The water-swellability depended on conditions such as solvent and pH. These were known and discussed in e.g. D21. Therefore, the term water-swellable should be understood as meaning adhesive layers which were capable of taking up water and of swelling to infiltrate between the teeth under the use conditions of the dental strip.

It was, however, not disclosed that the gel of the dental strip in D4 could absorb water and expand to infiltrate between the teeth during use - it was in fact flowable. The gel was neutralised with sodium hydroxide and further contained a whitening agent. As described in D15 to D17, the neutralisation reduced the viscosity and thus the swelling. The experiment described in D22 was not carried out with the same polymer. Moreover, it was carried out in water and the viscosity was only estimated, not tested. The polymer in the experiment did not comprise the whitening agent (hydrogen peroxide) either. The experiment did therefore not demonstrate that the gel in D4 was water-swellable under the conditions of use. The gel, which, additionally, was not on the surface of the backing layer as claimed, was therefore not an adhesive layer according to feature A5.

The core did not contain an active agent, was not shown to be swellable and was therefore not an adhesive layer within the meaning of feature A5 either.

The subject-matter of claim 1 of the main request was therefore novel.

First auxiliary request - novelty

The amendment made to the first auxiliary request explicitly defined how the term water-swellable was to be understood.

As set out with respect to the main request, neither the gel nor the core of the dental strip in D4 was water-swellable within the correct, now explicitly defined understanding of the term.

The subject-matter of claim 1 of the main request was therefore novel.

Second and third auxiliary requests - inventive step

The subject-matter of claim 1 of these requests differed from the dental strip in D4 at least in that the active agent was a plaque-reducing agent.

The problem formulated by the appellant, i.e. to provide a dental strip that reduced plaque, was incorrect since it contained a pointer to the solution.

Instead, the problem to be solved was to provide a dental strip which treated interdental spaces more effectively.

D4 concerned a cosmetic treatment - whitening - where treatment of interdental spaces was not important. The system disclosed in document D7 had another purpose, namely to protect the oral care substance from erosion and interaction with saliva for a time sufficient for the active [agent] to provide a therapeutic benefit. The skilled person thus had no incentive to choose a plaque-reducing agent from the long list of possible active agents disclosed in D7 for use in the strip according to D4.

Consequently, the subject-matter of claim 1 of the second and third auxiliary requests involved an inventive step.

Fourth auxiliary request - added subject-matter, inventive step and adaptation of the description

The combination of a plaque-reducing agent and a polymer further including an effervescent substance did not extend beyond the content of the original application.

Paragraph [0010] described that features of different embodiments were not mutually exclusive and could be combined. Paragraphs [0025] and [0028] used open language which also encompassed the combination of an effervescent substance and an active agent in the form of a plaque-reducing agent, especially since original claim 2 already specified that a plaque-reducing agent was a preferred active agent.

Furthermore, the subject-matter of claim 1 differed from the dental strip in D4 on account of both the plaque-reducing agent and the effervescent substance. These differences had a synergistic effect since the effervescence forced the plaque-reducing agent into the areas between the teeth which were hardest to brush - exactly where it was most needed. This relied on a physical effect which was plausible from the patent without the need for any further evidence.

The problem to be solved was thus to provide a dental strip with an improved capacity to deliver the plaque-reducing agent to interdental spaces.

D4 did not mention interdental delivery. It explicitly mentioned substituting - not combining - the whitening agent peroxide in the specific gel with another active agent, thus teaching away from a combination of active agents. D12 did not mention anything about delivery of plaque-reducing agents to the interdental spaces either, and concerned a dentifrice rather than a dental strip. It also taught away from using film backings. D7 was a patent document and as such not evidence of the common general knowledge. Furthermore, none of the cited prior art discussed the compatibility of various active agents. D2 and D8, which were mentioned in this context, had never been used in the appeal proceedings before the oral proceedings and should be disregarded for that reason alone.

The description filed during the oral proceedings did not contradict the claims, but rather supported them. The question of whether peroxide as such could act as an effervescent substance was not relevant to the outcome of the discussion on inventive step; the decisive factors were whether it was acting as an effervescent substance in the particular dental strip in D4 and whether it would have been obvious to combine the peroxide in D4 with a plaque-reducing agent. The amendments to paragraph [0023] suggested by the appellant were thus not necessary.