Tosoh Corporation v. Dental Direkt GmbH

I. Executive Summary and Procedural Information

• Case Name: TOSOH CORPORATION v. DENTAL DIRECKT GMBH
• Plaintiff’s Counsel: LABGOLD LAW; NAGASHIMA HASHIMOTO & YASUKUNI; GILLAM & SMITH, LLP
• Case Identification: 2:24-cv-00138, E.D. Tex., 06/03/2024
• Venue Allegations: Venue is alleged as proper under 28 U.S.C. § 1391(c) on the basis that the defendant is a foreign corporation and may be sued in any judicial district.
• Core Dispute: Plaintiff alleges that Defendant’s yttria-stabilized zirconia products for dental restorations infringe four U.S. patents directed to the chemical composition, physical properties, and layered structure of such ceramic materials.
• Technical Context: The case concerns 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 that Defendant entered into an exclusive U.S. distributorship agreement with VITA North America in or around December 2022. It also alleges Defendant had pre-suit knowledge of two of the asserted patents since at least February 2022, which forms the basis for willfulness allegations regarding those patents.

Case Timeline

Date	Event
2008-04-09	U.S. Patent No. 9,309,157 Priority Date
2011-07-29	U.S. Patent No. 9,249,056 Priority Date
2013-12-24	U.S. Patent No. 9,737,383 Priority Date
2016-02-02	U.S. Patent No. 9,249,056 Issues
2016-04-12	U.S. Patent No. 9,309,157 Issues
2017-08-22	U.S. Patent No. 9,737,383 Issues
2019-03-04	U.S. Patent No. 11,548,825 Priority Date
2022-02-01	Alleged knowledge of ’056 and ’157 Patents by Defendant (approx.)
2022-12-01	Defendant enters exclusive distribution agreement with VITA (approx.)
2023-01-10	U.S. Patent No. 11,548,825 Issues
2024-06-03	Complaint Filed

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

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 describes a need for zirconia sintered bodies that serve as dental materials possessing not only high strength but also aesthetic properties, such as color and translucency, that are "quite similar to those of natural teeth" (Compl. ¶34; ’056 Patent, col. 1:11-16). Prior art materials allegedly required lamination with other materials to achieve a natural look, which could compromise strength (Compl. ¶34; ’056 Patent, col. 1:21-28).
• The Patented Solution: The invention is a specific formulation for a colored zirconia sintered body that achieves the desired aesthetic and strength characteristics monolithically. The solution combines an iron compound for color, a specific range of yttria (2 to 4 mol %) as a stabilizer, and a controlled amount of alumina (less than 0.25 wt %), which together yield a final product with a specified lightness (L*) and a high relative density of at least 99.80% (’056 Patent, Abstract; Compl. ¶35).
• Technical Importance: This approach sought to create a single, uniform dental material that could be used for prosthetics without requiring additional aesthetic layering, thereby simplifying the manufacturing of durable, natural-looking dental restorations (Compl. ¶34).

Key Claims at a Glance

• The complaint asserts at least independent Claim 1 (Compl. ¶55).
• The essential elements of Claim 1 are:
  • A colored translucent zirconia sintered body
  • Comprising at least one iron compound (from a specified group)
  • Comprising yttria in the amount of from 2 to 4 mol %
  • Comprising alumina in the amount of 0 wt % to less than 0.25 wt %
  • Wherein the 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”

Issued April 12, 2016

The Invention Explained

• Problem Addressed: The patent identifies the challenge of producing zirconia sintered bodies that possess high sintered-body density and high strength while also having excellent translucency, a key aesthetic requirement for dental applications (Compl. ¶39; ’157 Patent, col. 1:18-24).
• The Patented Solution: The patent claims a translucent zirconia sintered body defined by a specific composition and a set of resulting physical properties. The composition requires 2-4 mol % yttria as a stabilizer and an alumina content below 0.1 wt %. This formulation is claimed to result in a body with a relative density of 99.8% or higher and, critically, a total light transmittance of 35% or higher at a 1.0 mm thickness (’157 Patent, Abstract; Compl. ¶40). The patent provides a specific, explicit formula within Claim 1 for calculating the required "relative density" (’157 Patent, col. 1:33-46).
• Technical Importance: The invention provides a specific recipe and property profile for creating a highly translucent yet strong zirconia material suitable for dental prosthetics where appearance is a primary concern (Compl. ¶39).

Key Claims at a Glance

• The complaint asserts at least independent Claim 1 (Compl. ¶88).
• The essential elements of Claim 1 are:
  • A translucent zirconia sintered body
  • Comprising zirconia that contains 2-4 mol % yttria as a stabilizer
  • And has an alumina content of lower than 0.1 wt %
  • Having a relative density of 99.8% or higher, where relative density is defined by a specific formula and set of constants provided in the claim
  • And having a total light transmittance of 35% or higher, as measured at a thickness of 1.0 mm

U.S. Patent No. 9,737,383 - “TRANSLUCENT ZIRCONIA SINTERED BODY AND ZIRCONIA POWDER, AND USE THEREFOR”

Issued August 22, 2017

• Technology Synopsis: The patent discloses zirconia sintered bodies intended to have both "excellent translucency and bending strength" for dental applications (Compl. ¶44). The claimed solution specifies a composition with a higher yttria content (more than 4.0 mol % and at most 6.5 mol %) and low alumina (< 0.1 wt %), along with a narrow range for total light transmittance (37% to less than 40%) and minimum bending strength (at least 500 MPa) (Compl. ¶45).
• Asserted Claims: At least Claim 1 (Compl. ¶120).
• Accused Features: Defendant's DDcubeX² products are accused of meeting the compositional and physical property limitations of the patent when processed into a sintered body (Compl. ¶¶ 123-128).

U.S. Patent No. 11,548,825 - “ZIRCONIA LAYERED BODY”

Issued January 10, 2023

• Technology Synopsis: This patent describes a layered zirconia body suitable for dental prosthetics, designed to mimic the natural gradation of a tooth (Compl. ¶50). The invention is a calcined body comprising at least two layers containing zirconia and a stabilizer, where the stabilizer content differs between the layers by at least 0.5 mol %, with one layer having a stabilizer content of at least 4 mol % (Compl. ¶51).
• Asserted Claims: At least Claims 1 and 18 (Compl. ¶¶ 158, 165).
• Accused Features: Defendant's Nacera Pearl Natural (A2) product is accused of being a "layered body having a structure comprising two or more layers of stabilized zirconia" with different stabilizer contents as claimed (Compl. ¶¶ 160-163).

III. The Accused Instrumentality

Product Identification

• The accused products are yttria-stabilized zirconia materials sold for dental applications, collectively referred to as the "Accused Instrumentalities" (Compl. ¶24). Specific product lines named include DDBioZX², Nacera Pearl Shaded A2, DDcubeONE, Nacera Pearl 1, DD Cube X², and Nacera Pearl Natural (A2) (Compl. ¶¶ 20, 21, 22, 23).

Functionality and Market Context

• The complaint alleges these products are zirconia powders or blocks designed and promoted for use in producing dental restorations like artificial teeth and orthodontic brackets (Compl. ¶¶ 34, 57, 90). They are manufactured outside the U.S. and allegedly imported and sold throughout the U.S. via an exclusive distributor, VITA North America (Compl. ¶¶ 25, 31). The infringement theory is that when these products are used as instructed by customers (e.g., sintered in a dental lab), they form sintered bodies that meet the limitations of the asserted patents (Compl. ¶¶ 57-62).
• No probative visual evidence provided in complaint.

IV. Analysis of Infringement Allegations

’9,249,056 Infringement Allegations

Claim Element (from Independent Claim 1)	Alleged Infringing Functionality	Complaint Citation	Patent Citation
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...	Sintered bodies prepared from the accused DDBioZX² (A2) and Nacera Pearl Shaded A2 products allegedly comprise at least one of these iron compounds.	¶58	col. 2:16-18
yttria in the amount of from 2 to 4 mol %...	The sintered bodies allegedly comprise yttria within the 2 to 4 mol % range.	¶59	col. 2:18-19
and alumina in the amount of 0 wt % to less than 0.25 wt %...	The sintered bodies allegedly comprise alumina within the 0 to less than 0.25 wt % range.	¶60	col. 2:48-49
wherein the colored translucent zirconia sintered body has a lightness L* of from 51 to 80 in L*a*b* color system...	The sintered bodies allegedly exhibit a lightness L* value between 51 and 80.	¶61	col. 2:19-20
and has a relative density of at least 99.80%.	The sintered bodies allegedly have a relative density of at least 99.80%.	¶62	col. 2:20-20

• Identified Points of Contention:
  • Evidentiary Questions: The complaint's allegations regarding the specific chemical compositions and physical properties of the final sintered bodies are made "on information and belief." A central point of contention may be whether discovery and expert testing will substantiate that the accused products, when sintered, consistently meet all five quantitative limitations (iron compound, yttria %, alumina %, lightness L*, and relative density) of Claim 1.
  • Scope Questions: The claims cover a "sintered body," which is the final product created by a dental lab or manufacturer. Defendant sells the precursor material. The dispute will therefore involve theories of indirect infringement, raising the question of whether Defendant's instructions and marketing materials specifically intend for its customers to create a product that meets every limitation of the asserted claim.

’9,309,157 Infringement Allegations

Claim Element (from Independent Claim 1)	Alleged Infringing Functionality	Complaint Citation	Patent Citation
A translucent zirconia sintered body characterized by comprising zirconia that contains 2-4 mol % yttria as a stabilizer...	Sintered bodies prepared from the accused DDBioZX² (white), DDcubeONE (white), and Nacera Pearl 1 products allegedly comprise yttria within the 2-4 mol % range.	¶91	col. 1:29-30
and has an alumina content of lower than 0.1 wt %...	The sintered bodies allegedly have an alumina content lower than 0.1 wt %.	¶92	col. 1:30-31
and by having a relative density of 99.8% or higher, wherein relative density means the value obtained by measuring an actual density p... [and using a specified formula and constants]	The sintered bodies allegedly have a relative density of 99.8% or higher when measured according to the specific method, formula, and constants recited in the claim.	¶93	col. 1:31-46
and a total light transmittance, as measured at a thickness of 1.0 mm, of 35% or higher...	The sintered bodies allegedly exhibit a total light transmittance of 35% or higher when measured at a 1.0 mm thickness.	¶94	col. 1:32-33

• Identified Points of Contention:
  • Technical Questions: The infringement analysis for the '157 Patent will turn on highly specific measurements. A key question will be whether testing of the accused products confirms they meet the "relative density" limitation precisely as defined by the patentee's explicit formula in Claim 1. Any variation in the theoretical density of the accused zirconia from the specific value of 6.0956 g/cm3 recited in the claim for zirconia with 3 mol % yttria could be a basis for a non-infringement argument.
  • Scope Questions: Similar to the '056 patent, the dispute will involve whether Defendant possessed the specific intent to induce its customers to create a final product that meets all limitations, including the highly specific measurement protocol for relative density outlined in Claim 1.

V. Key Claim Terms for Construction

• The Term: "sintered body" (from ’056 Patent, Claim 1 and ’157 Patent, Claim 1)

  • Context and Importance: This term is critical because Defendant sells the precursor materials (e.g., zirconia blocks or powders), not the final "sintered body" that is the subject of the claims. The infringement case rests on a theory of indirect infringement, where Defendant's customers are the direct infringers who create the claimed "sintered body." The construction of this term will determine the scope of the direct infringement that Plaintiff must prove.
  • Intrinsic Evidence for Interpretation:
    • Evidence for a Broader Interpretation: The patents' titles and detailed descriptions focus on the properties and use of the final product, suggesting the term should be understood in its ordinary sense in materials science—a densified ceramic body formed by heating a powder compact (’056 Patent, col. 1:11-16; ’157 Patent, col. 1:18-24).
    • Evidence for a Narrower Interpretation: The specifications describe specific processes for creating the sintered body from a powder, including molding, sintering temperatures, and times (’056 Patent, col. 7:4-col. 8:12; ’157 Patent, col. 7:59-col. 8:23). A defendant may argue that "sintered body" should be limited to bodies created by these specific processes, potentially creating a non-infringement argument if its customers use different parameters.

• The Term: "wherein relative density means..." (definitional clause from ’157 Patent, Claim 1)

  • Context and Importance: This is an instance where the patentee has acted as their own lexicographer by explicitly defining a claim term. The construction of this clause is central to the infringement analysis for the relative density limitation. Practitioners may focus on this term because infringement requires not just achieving a certain density, but achieving it as measured by the precise, multi-step process, including a specific formula and constants, recited in the claim itself.
  • Intrinsic Evidence for Interpretation:
    • Evidence for a Broader Interpretation: A party might argue that the formula is exemplary and that other scientifically valid methods for determining relative density should be considered equivalent. However, the use of the word "means" strongly cuts against such an interpretation.
    • Evidence for a Narrower Interpretation: The claim language itself is the strongest evidence for a narrow, binding definition. The phrase "wherein relative density means..." signals a clear intent to define the term. The specification supports this by providing detailed measurement protocols that align with the claim's definition (’157 Patent, col. 10:59-col. 11:23). This suggests the definition is not merely illustrative but is a strict limitation on the claim scope.

VI. Other Allegations

• Indirect Infringement: The complaint broadly alleges both induced and contributory infringement for all asserted patents. Inducement is primarily based on allegations that Defendant provides instructions, technical assistance, marketing, and promotional materials that encourage and instruct customers to use the accused precursor products to create the claimed final sintered bodies (Compl. ¶¶ 64-65, 96-97, 130-131, 166-167). Contributory infringement is alleged on the basis that the products are especially made for an infringing use, are not staple articles of commerce, and lack substantial non-infringing uses (Compl. ¶¶ 69-73, 101-105, 135-139). For the ’825 Patent, the complaint also alleges inducement of the method of Claim 18 (Compl. ¶165).
• Willful Infringement: Willfulness is alleged for all four patents. For the ’056 and ’157 Patents, the claim is based on alleged pre-suit knowledge since "at least as early as February 2022" (Compl. ¶¶ 76, 108). For the ’383 and ’825 Patents, willfulness is based on knowledge "at least as early as the filing of this Complaint," supporting a theory of post-suit willfulness (Compl. ¶¶ 142, 174).

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

• A central issue will be one of evidentiary proof: Can Plaintiff demonstrate through testing that the accused precursor materials, when processed according to Defendant’s instructions, consistently result in "sintered bodies" that meet every quantitative chemical and physical limitation recited in the asserted claims? The outcome may depend heavily on the methodologies and results of competing expert analyses.
• The case will also involve a core question of definitional precision: For the ’157 Patent, can infringement of the "relative density" limitation be established only by strict adherence to the explicit formula and constants provided in Claim 1, or is there scope for arguing that alternative measurement techniques are legally equivalent?
• A third key question will be one of intent for indirect infringement: Can Plaintiff prove that Defendant, through its marketing and instructions, possessed the specific intent to encourage its customers to create products that infringe the patents, or can Defendant successfully argue that its products have substantial non-infringing uses or that its customers' final products do not necessarily practice the claimed inventions?