DCT

2:24-cv-00138

Tosoh Corporation v. Dental Direkt GmbH

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Key Events
Complaint

I. Executive Summary and Procedural Information

  • Parties & Counsel:
  • Case Identification: 2:24-cv-00138, E.D. Tex., 02/26/2024
  • Venue Allegations: Venue is alleged to be proper on the basis that the defendant is a foreign corporation and may therefore be sued in any judicial district.
  • Core Dispute: Plaintiff alleges that Defendant’s yttria-stabilized zirconia products for dental restorations infringe two U.S. patents directed to the composition and physical properties of such materials.
  • Technical Context: The technology at issue is yttria-stabilized zirconia, a high-strength ceramic material widely used in the dental industry for crowns, bridges, and other prosthetics due to its combination of durability and aesthetic qualities like translucency.
  • Key Procedural History: The complaint alleges Defendant had knowledge of the asserted patents and their infringement since at least February 2022. It further alleges that in or around December 2022, Defendant entered into an exclusive U.S. distributorship agreement with VITA North America, Inc.

Case Timeline

Date Event
2008-04-09 ’157 Patent Priority Date
2010-09-28 ’157 Patent Assigned to Tosoh
2011-07-29 ’056 Patent Priority Date
2014-01-28 ’056 Patent Assigned to Tosoh
2016-02-02 ’056 Patent Issue Date
2016-04-12 ’157 Patent Issue Date
2022-02-01 Alleged Pre-Suit Knowledge of Patents by Defendant
2022-12-01 Defendant Enters Exclusive U.S. Distributorship with VITA
2024-02-26 Complaint Filing Date

II. Technology and Patent(s)-in-Suit Analysis

U.S. Patent No. 9,249,056 - "COLORED TRANSLUCENT ZIRCONIA SINTERED BODY AND ITS USE"

  • Patent Identification: U.S. Patent No. 9,249,056, "COLORED TRANSLUCENT ZIRCONIA SINTERED BODY AND ITS USE," issued February 2, 2016.

The Invention Explained

  • Problem Addressed: The patent’s background section describes the difficulty in creating a zirconia sintered body for dental use that possesses both high strength and aesthetic properties (e.g., color tone, translucency) similar to natural teeth (Compl. ¶27; ’056 Patent, col. 1:12-20). Prior art solutions often involved laminating weaker, aesthetic materials onto a strong zirconia core, which compromised the overall strength of the dental restoration (’056 Patent, col. 1:21-28).
  • The Patented Solution: The invention claims a specific composition for a "colored translucent zirconia sintered body" that achieves the desired balance of strength and aesthetics in a monolithic structure. The solution is defined by specific quantitative ranges for an iron compound (as a coloring agent), yttria (as a stabilizer), and alumina, which together result in a final product with a claimed range of lightness (L*) and a high relative density (’056 Patent, Abstract; col. 2:17-21).
  • Technical Importance: This technology sought to enable the creation of strong, monolithic dental prosthetics that could mimic the appearance of natural teeth without requiring additional, strength-compromising layers of porcelain or glass (Compl. ¶27).

Key Claims at a Glance

  • The complaint asserts infringement of at least Claim 1 (Compl. ¶¶15, 37).
  • Independent Claim 1 requires:
    • A colored translucent zirconia sintered body, comprising at least one iron compound selected from the group consisting of iron chloride, iron nitrate, iron oxide and iron oxide hydroxide,
    • yttria in the amount of from 2 to 4 mol %,
    • alumina in the amount of 0 wt % to less than 0.25 wt %,
    • wherein the colored translucent zirconia sintered body has a lightness L* of from 51 to 80 in L*a*b* color system,
    • and has a relative density of at least 99.80%.

U.S. Patent No. 9,309,157 - "TRANSLUCENT ZIRCONIA SINTERED BODY, PROCESS FOR PRODUCING THE SAME, AND USE OF THE SAME"

  • Patent Identification: U.S. Patent No. 9,309,157, "TRANSLUCENT ZIRCONIA SINTERED BODY, PROCESS FOR PRODUCING THE SAME, AND USE OF THE SAME," issued April 12, 2016.

The Invention Explained

  • Problem Addressed: The patent addresses the challenge of producing a zirconia sintered body that is highly translucent—a key aesthetic property for dental materials—while maintaining high strength and high density. The background notes that achieving sufficient translucency often required specialized, high-pressure sintering processes like Hot Isostatic Pressing (HIP), as conventional normal-pressure sintering was insufficient (’157 Patent, col. 1:63-68).
  • The Patented Solution: The patent discloses a translucent zirconia sintered body with a specific composition and physical properties that can be achieved through normal-pressure sintering. The solution is defined by a specific range of yttria content, a low maximum alumina content, a minimum relative density, and a minimum total light transmittance. The claim also explicitly defines the formula for calculating the relative density, a critical parameter for the invention (’157 Patent, Abstract; col. 2:40-50).
  • Technical Importance: The invention aimed to allow for the manufacture of high-strength, highly translucent zirconia dental materials using more common and cost-effective normal-pressure sintering methods, thereby avoiding the need for expensive HIP equipment (Compl. ¶32).

Key Claims at a Glance

  • The complaint asserts infringement of at least Claim 1 (Compl. ¶¶16, 70).
  • Independent Claim 1 requires:
    • A translucent zirconia sintered body characterized by comprising zirconia which contains 2-4 mol % yttria as a stabilizer and has an alumina content of lower than 0.1 wt %,
    • and by having a relative density of 99.8% or higher and a total light transmittance, as measured at a thickness of 1.0 mm, of 35% or higher;
    • wherein relative density means the value obtained by measuring an actual density ρ by the Archimedes method, determining a theoretical density ρo using a specific equation, converting these values, and using specified theoretical densities for alumina and zirconia in that equation.

III. The Accused Instrumentality

Product Identification

  • The accused instrumentalities include Defendant's zirconia products for dental applications (Compl. ¶15, ¶16). Specifically identified products are DDBioZX² (A2 and white versions), Nacera Pearl Shaded A2, DDcubeONE (white), and Nacera Pearl 1 (Compl. ¶15, ¶16).

Functionality and Market Context

  • The accused products are yttria-stabilized zirconia powders or blocks intended for the fabrication of dental restorations such as artificial teeth and orthodontic brackets (Compl. ¶3, ¶15-16). Their function is to provide a material that can be milled or processed into a final dental prosthetic that possesses both high strength and aesthetic properties, such as realistic translucency and shading, to match natural teeth (Compl. ¶3).
  • The complaint alleges Defendant markets these products in the United States through an exclusive distributorship with VITA North America, Inc., which was established to provide the U.S. market with an "expansive and advance [sic] zirconia portfolio" (Compl. ¶6).

IV. Analysis of Infringement Allegations

No probative visual evidence provided in complaint.

The complaint references claim chart exhibits that are not provided. The narrative infringement theory is summarized below in prose.

  • 9,249,056 Infringement Allegations
    The complaint alleges that sintered bodies prepared from the accused DDBioZX² (A2) and Nacera Pearl Shaded A2 products meet all limitations of at least Claim 1 of the ’056 Patent (Compl. ¶37). It specifically alleges that these products, when sintered, contain an iron compound, have a yttria content between 2 and 4 mol %, an alumina content between 0 wt % and less than 0.25 wt %, a lightness L* between 51 and 80, and a relative density of at least 99.80% (Compl. ¶¶39-43).

  • 9,309,157 Infringement Allegations
    The complaint alleges that sintered bodies prepared from the accused DDBioZX² (white), DDcubeONE (white), and Nacera Pearl 1 products meet all limitations of at least Claim 1 of the ’157 Patent (Compl. ¶70). The allegations state that these products comprise zirconia with 2-4 mol % yttria, an alumina content below 0.1 wt %, a relative density of 99.8% or higher, and a total light transmittance of 35% or higher at a 1.0 mm thickness (Compl. ¶¶72-75). The complaint further alleges that the relative density meets the claimed threshold when measured and calculated according to the specific formula recited in the claim (Compl. ¶74).

  • Identified Points of Contention:

    • Scope Questions: Claim 1 of the ’157 Patent defines "relative density" with a detailed, multi-part definition that includes a specific mathematical formula. A potential point of contention may be whether the defendant’s accused products satisfy the "99.8% or higher" limitation when their density is calculated using the precise formula and constants mandated by the claim.
    • Technical Questions: The infringement theories for both patents rely on specific, quantitative measurements of chemical composition (e.g., yttria mol %, iron compound presence) and physical properties (e.g., lightness L*, relative density, total light transmittance). A primary technical question will be whether independent testing of the accused products confirms the precise values required by the claims and alleged in the complaint.

V. Key Claim Terms for Construction

  • The Term: "a lightness L* of from 51 to 80 in L*a*b* color system" (’056 Patent, Claim 1)

  • Context and Importance: This term is a critical limitation defining the aesthetic properties of the final sintered body. The infringement analysis will depend on factual evidence showing the accused products fall within this specific numerical range. Practitioners may focus on the methodology and conditions for measuring L*, as these can influence the outcome.

  • Intrinsic Evidence for Interpretation:

    • Evidence for a Broader Interpretation: The claim language provides a straightforward numerical range, which may suggest that any product falling within that range infringes, regardless of the specific measurement protocol used, so long as it is scientifically valid. The patent’s objective is to achieve aesthetic properties "equivalent to those of natural teeth" (’056 Patent, col. 1:43-44), potentially supporting any interpretation consistent with that goal.
    • Evidence for a Narrower Interpretation: The specification provides detailed examples with specific L* values measured under specific conditions (’056 Patent, Table 1, col. 15-18). A defendant might argue that the claim term should be construed in light of these examples and the measurement standards referenced in the patent, such as JIS Z8729 (’056 Patent, col. 10:25-33).

  • The Term: "total light transmittance, as measured at a thickness of 1.0 mm, of 35% or higher" (’157 Patent, Claim 1)

  • Context and Importance: This is the central claim limitation defining the "translucent" character of the invention. The dispute will likely turn on factual measurements of the accused products. Practitioners may focus on the precise methodology for measuring transmittance, as sample preparation and instrument settings can affect the result.

  • Intrinsic Evidence for Interpretation:

    • Evidence for a Broader Interpretation: The claim sets a clear numerical floor ("35% or higher"), which could suggest that any scientifically valid measurement meeting this threshold is sufficient to show infringement.
    • Evidence for a Narrower Interpretation: The specification describes a specific measurement method according to JIS K 7361, using a spectrophotometer and an integrating sphere to capture both direct and diffuse light (’157 Patent, col. 8:26-38). A defendant may argue that the term should be limited to values obtained using this specific standard and equipment configuration.

VI. Other Allegations

  • Indirect Infringement: The complaint alleges both inducement and contributory infringement for both patents. The inducement theory is based on allegations that Defendant instructs customers on how to use the products for infringing purposes, provides technical assistance, and promotes these uses through marketing and its website (Compl. ¶¶44-46, 76-78). The contributory infringement theory is based on allegations that the accused products are specially designed for an infringing use, constitute a material part of the patented compositions, and have no substantial non-infringing uses (Compl. ¶¶48-55, 80-87).
  • Willful Infringement: Willfulness is alleged based on pre-suit knowledge. The complaint asserts that Defendant had knowledge of both the ’056 and ’157 Patents and their alleged infringement "since at least as early as February 2022" (Compl. ¶57, ¶89). It also alleges continued infringement after receiving notice of its infringement, although the date of such notice is not specified (Compl. ¶66, ¶98).

VII. Analyst’s Conclusion: Key Questions for the Case

  • A central issue will be one of empirical verification: will independent laboratory analysis of the accused zirconia products confirm they possess the specific, quantitative chemical compositions (e.g., yttria mol %, alumina wt %) and physical properties (e.g., relative density, total light transmittance) required by the asserted claims when measured under appropriate conditions?
  • A key question for enhanced damages will be one of pre-suit knowledge: what evidence can the plaintiff produce to substantiate its allegation that the defendant knew of the asserted patents and their alleged infringement as early as February 2022, approximately two years before the complaint was filed?
  • For the ’157 Patent, the dispute may turn on methodological compliance: does the measurement of the accused products' "relative density" conform to the specific mathematical formula and constants explicitly recited in Claim 1, and does the resulting value meet the claimed "99.8% or higher" threshold?