PTAB

IPR2018-00941

GC Corporation v. Ardent, Inc.

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1. Case Identification

2. Patent Overview

  • Title: Lithium Disilicate Glass-Ceramic
  • Brief Description: The ’451 patent is directed to lithium disilicate (Li₂Si₂O₅) based glass-ceramic compositions and methods for making them. The compositions are described as useful for fabricating single and multi-unit dental restorations, such as crowns and bridges.

3. Grounds for Unpatentability

Ground 1: Obviousness over Beall - Claims 1 and 3 are obvious over Beall.

  • Prior Art Relied Upon: Beall (Patent 5,219,799).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Beall, which discloses lithium disilicate-containing glass-ceramics, teaches broad compositional ranges that entirely overlap or are very close to the ranges recited in claims 1 and 3 of the ’451 patent. For claim 1, Petitioner asserted that selecting a narrow compositional range from within Beall’s broader disclosed range is prima facie obvious. For claim 3, Petitioner argued that Beall's Example 7 teaches a composition that is either within or, considering the term "about," rendered obvious by the closeness to the claimed ranges. The argument hinged on the legal principle that a prima facie case of obviousness exists when claimed ranges overlap with or are close to ranges disclosed in the prior art.
    • Expectation of Success: A person of ordinary skill in the art (POSITA) would expect a composition with component percentages close to those in the prior art to have similar properties.

Ground 2: Obviousness over Petticrew in view of Beall - Claims 2, 4, and 57-61 are obvious over Petticrew in view of Beall.

  • Prior Art Relied Upon: Petticrew (International Publication No. WO 95/32678) and Beall (Patent 5,219,799).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner asserted that while Beall discloses the core glass-ceramic compositions, it does not explicitly teach their use as "pressable" dental restorations. Petticrew was argued to supply these missing elements. Petticrew discloses methods for molding dental restorations (e.g., crowns, bridges) from lithium disilicate glass-ceramic materials by pressing them into a mold. This combination allegedly taught the limitations of a "dental restoration" (claims 57-61) and a "pressable" glass-ceramic (claims 2 and 4). For claim 59's "blank for machining," Petitioner argued that forming a blank is an obvious, conventional step for preparing materials for dental CAD/CAM systems, a known practice at the time.
    • Motivation to Combine: The motivation was argued to be explicit. Petticrew directly and specifically cited the Beall patent as disclosing "lithium disilicate glass-ceramic materials which may be used in this invention."
    • Expectation of Success: A POSITA would have a reasonable expectation of success because Petticrew teaches that lithium disilicate materials, such as those in Beall, are "particularly suited" for use in its process for forming dental restorations.

Ground 3: Obviousness over Echeverria - Claim 3 is obvious over Echeverria.

  • Prior Art Relied Upon: Echeverria (a 1992 article in Journal of the Spanish Ceramic and Glass Society).
  • Core Argument for this Ground:
    • Prior Art Mapping: This ground presented an argument parallel to Ground 1, but using Echeverria instead of Beall. Petitioner contended that Echeverria, a publication by one of Beall's co-inventors, discloses lithium disilicate glass-ceramic compositions that are even closer to the ranges recited in claim 3 than those in Beall. Petitioner’s analysis showed that Echeverria's Example E falls almost entirely within the explicit ranges of claim 3, with only one component (CaO at 1.01%) falling just outside the claimed "up to about 0.9%" range. Petitioner argued this minor difference would have been obvious to a POSITA.
    • Expectation of Success: A POSITA would expect Echeverria's Example E composition to have the same properties as a composition falling within the claimed ranges due to the significant compositional similarity.

Ground 4: Obviousness over Petticrew in view of Echeverria - Claims 4, 57-59, and 61 are obvious over Petticrew in view of Echeverria.

  • Prior Art Relied Upon: Petticrew (International Publication No. WO 95/32678) and Echeverria (a 1992 article).
  • Core Argument for this Ground:
    • Prior Art Mapping: This ground mirrored the logic of Ground 2, substituting Echeverria for Beall as the source of the base composition. Petitioner argued that Echeverria discloses a suitable lithium disilicate glass-ceramic (specifically Example D for claim 57 and Example E for claim 61), and Petticrew teaches the application of such materials for creating pressable dental restorations. The combination was alleged to render obvious the product-by-process and dental restoration claims. Echeverria's disclosure of compositions amenable to "diverse forming techniques" was argued to further support the obviousness of pressing or machining them for dental use.
    • Motivation to Combine: While Petticrew does not explicitly name Echeverria, Petitioner argued a POSITA would have been motivated to combine them. Petticrew teaches the general suitability of lithium disilicate glass-ceramics, and Echeverria discloses compositions that are fundamentally similar to those in Beall (which Petticrew does cite). A POSITA would thus recognize Echeverria's materials as suitable for Petticrew's method.
    • Expectation of Success: A POSITA would reasonably expect success for the same reasons as in Ground 2: Petticrew teaches that lithium disilicate materials are "particularly suited" for its methods, and Echeverria's compositions are of that type.

4. Key Claim Construction Positions

  • Consisting Essentially Of: Petitioner proposed this term should be defined according to the patent’s prosecution history, where the applicants explicitly defined it to overcome prior art. The proposed construction is "consisting of SiO₂, Al₂O₃, Li₂O, K₂O and P₂O₅ as main ingredients with the following components also permitted—[list of 17 optional oxides]." This construction was central to arguing that prior art which included unlisted components (like MgO or La₂O₃) was distinguished by the patentee, but that the cited art in the petition (Beall, Echeverria) does not contain such unlisted components.
  • Dental Restoration: Proposed as "a dental appliance shaped for placement into a patient's mouth." This construction, drawn from the specification, was used to map teachings of crowns, bridges, and inlays in the prior art to the claim term.
  • Pressable: Proposed as "able to be formed into dental articles by heat pressing or injection molding using commercially available equipment." This definition, taken from the ’451 patent's specification, was key to linking the methods in Petticrew to the "pressable" limitation.
  • About: Proposed to mean "approximately," and further noted that Patent Owner had previously asserted it should be construed as "±2 units in the least significant figure position." This construction was used to argue that certain prior art examples with compositions just outside the literal claimed ranges (e.g., Beall's Example 7, Echeverria's Example E) actually fall within the scope of the claims.

5. Relief Requested

  • Petitioner requested institution of an inter partes review and cancellation of claims 1-4 and 57-61 of Patent 6,455,451 as unpatentable.