DCT
1:25-cv-01123
Guidance Endodontics LLC v. Dentsply Sirona Inc
I. Executive Summary and Procedural Information
- Parties & Counsel:
- Plaintiff: Guidance Endodontics, LLC (New Mexico)
- Defendant: Dentsply Sirona Inc. (Delaware)
- Plaintiff’s Counsel: Morris, Nichols, Arsht & Tunnell LLP
- Case Identification: 1:25-cv-01123, D. Del., 09/09/2025
- Venue Allegations: Venue is alleged as proper in the District of Delaware because Defendant is a Delaware corporation.
- Core Dispute: Plaintiff alleges that Defendant’s endodontic files and obturators infringe two patents related to the geometric design of such instruments, focusing on variable taper rates and cutting-edge angles.
- Technical Context: The technology concerns instruments used in endodontics (root canal therapy) to clean, shape, and fill the root canal of a tooth, where precise instrument geometry is critical for clinical success.
- Key Procedural History: The complaint alleges Defendant had pre-suit knowledge of the patents-in-suit. Specifically, it alleges a notice letter regarding the ’605 Patent was sent on August 24, 2020. It further alleges Defendant was aware of the ’173 Patent because its own patent application was rejected by the U.S. Patent and Trademark Office as anticipated by the published application for the ’173 Patent, after which Defendant abandoned its application.
Case Timeline
| Date | Event |
|---|---|
| 2004-03-16 | ’605 and ’173 Patents Priority Date |
| 2011-06-28 | U.S. Patent No. 7,967,605 Issued |
| 2016-01-01 | Article published describing Accused WOG Files |
| 2018-08-21 | U.S. Patent No. 10,052,173 Issued |
| 2019-06-19 | Defendant files its own related patent application ('762 application) |
| 2020-08-24 | Plaintiff sends notice letter to Defendant regarding ’605 Patent |
| 2022-07-22 | USPTO rejects Defendant's '762 application over '173 patent family prior art |
| 2023-02-06 | Defendant abandons its '762 application |
| 2025-09-09 | Complaint Filing Date |
II. Technology and Patent(s)-in-Suit Analysis
U.S. Patent No. 7,967,605 - "Endodontic Files and Obturator Devices and Methods of Manufacturing Same"
The Invention Explained
- Problem Addressed: The patent’s background section describes problems with conventional endodontic files, including their propensity to break within a patient's tooth due to frictional and torque forces, their inefficient removal of tissue, and their tendency to undesirably remove portions of the root canal wall because of their limited flexibility (ʼ605 Patent, col. 1:43-2:14).
- The Patented Solution: The invention is an endodontic file with a specific geometry designed to overcome these problems. Its key features include a taper configuration with at least two different rates of taper, where the taper rate closer to the handle (shank) is smaller than the rate closer to the tip, and a cutting edge with a rake angle that continuously increases along the working length of the file from the tip to the shank ('605 Patent, Abstract; col. 11:50-56). This geometry is intended to reduce friction and torque during operation, thereby minimizing the likelihood of breakage ('605 Patent, col. 11:18-24).
- Technical Importance: This design approach sought to improve the safety and efficiency of root canal procedures by creating a more flexible file that cuts more effectively as it advances into the canal. (ʼ605 Patent, col. 11:62-12:2).
Key Claims at a Glance
- The complaint asserts independent claim 1 (Compl. ¶25, 55).
- Claim 1 requires:
- An endodontic file comprising a tip, a shank, and a working length between them.
- The working length has a helical cutting edge defining a rake angle that varies between the tip and shank.
- The file has a taper configuration with at least two different rates of taper.
- The taper configuration is arranged so a rate of taper closer to the shank is smaller than a rate of taper closer to the tip.
- The rake angle continuously increases along the working length from the tip to the shank.
U.S. Patent No. 10,052,173 - "Endodontic Files and Obturator Devices and Methods of Manufacturing Same"
The Invention Explained
- Problem Addressed: The patent describes a problem with conventional obturators—the instruments used to fill a root canal after it has been cleaned. These obturators typically have a constant taper, which does not match the variable-taper shape created by modern endodontic files, leading to binding at the top of the canal and an incomplete seal ('173 Patent, col. 2:15-24).
- The Patented Solution: The invention is an obturator designed to precisely match the shape of a canal prepared by a variable-taper file. The claimed obturator has at least three adjacent, tapered portions of equal length. The rate of taper decreases from the first portion (near the tip) to the second, and again from the second portion to the third portion (near the shank) ('173 Patent, Abstract; Claim 1). This graduated taper is intended to allow the obturator to fit the prepared canal more accurately ('173 Patent, col. 7:25-34).
- Technical Importance: This innovation aimed to improve the quality of the root canal seal by creating a filling instrument whose shape corresponds to the shape of the prepared canal, reducing voids and improving long-term clinical outcomes. ('173 Patent, col. 2:25-34).
Key Claims at a Glance
- The complaint asserts independent claim 1 (Compl. ¶35, 63).
- Claim 1 requires:
- An endodontic obturator with a tip region, a shank region, and an obturator portion between them.
- The obturator portion has a body defining a taper and a material layer (e.g., gutta-percha).
- The obturator portion includes a first, a second, and a third tapered obturator portion arranged sequentially from tip to shank.
- These three portions are tapered, have a solid cross-section, and are of equal length.
- Each of the three portions has only one rate of taper.
- The rate of taper of the first portion is greater than the second, and the rate of taper of the second portion is greater than the third.
III. The Accused Instrumentality
Product Identification
- The complaint accuses Dentsply’s “WaveOne Gold Reciprocating Files” (“WOG Files”) of infringing the ’605 Patent and the corresponding “WaveOne Gold Conform Fit Gutta-Percha Points” (“WOG Obturator Cones”) of infringing the ’173 Patent (Compl. ¶1).
Functionality and Market Context
- The complaint presents the accused products as an integrated system for performing root canal procedures (Compl. ¶48). The WOG Files are described as having a "variable taper" and a "progressively decreasing percentage tapered design" (Compl. ¶29). An annotated image of a WOG File in the complaint identifies its tip, shank, and working length (Compl. p. 6). The WOG Obturator Cones are described as being "reformulated to match the precise shapes created by the WaveOne Gold instruments" and are also alleged to have a "Variable taper" (Compl. ¶42). A diagram in the complaint shows an obturator being placed into a prepared root canal (Compl. p. 13).
IV. Analysis of Infringement Allegations
’605 Patent Infringement Allegations
| Claim Element (from Independent Claim 1) | Alleged Infringing Functionality | Complaint Citation | Patent Citation |
|---|---|---|---|
| An endodontic file comprising: a tip; a shank; and a working length disposed between the tip and the shank... | The WOG Files are endodontic files possessing a tip, a shank, and working lengths. | ¶26-29 | col. 10:15-25 |
| ...the working length having a helical cutting edge defining a rake angle, wherein the rake angle varies between the tip and the shank... | The WOG Files are alleged to have a "reverse helix design" and a "parallelogram cross-section." The complaint alleges this geometry results in a rake angle that varies. | ¶29 | col. 11:32-43 |
| ...wherein the taper configuration of the file includes at least two different rates of taper, the taper configuration of the file arranged such that a rate of taper closer to the shank is smaller than a rate of taper closer to the tip... | The WOG Files are alleged to have a "variable taper" and a "progressively decreasing percentage tapered design," as depicted in a diagram showing taper rates of 7.0%, 6.0%, and 3.0% at different points along the file (Compl. p. 8). | ¶29 | col. 12:1-6 |
| ...wherein the rake angle continuously increases along the working length from the tip to the shank. | The complaint alleges this element is met by the file's "alternating offset and transitioning parallelogram-shaped cross-section," which allegedly results in an acute angle that "is larger at the tip and decreases as it approaches the shank." | ¶29 | col. 11:50-56 |
- Identified Points of Contention:
- Scope Questions: A central dispute may arise over whether the accused file’s "alternating offset and transitioning parallelogram-shaped cross-section" constitutes a "rake angle" as that term is used in the patent. The complaint's infringement theory appears to equate the geometric "acute angle" of the parallelogram with the claimed "rake angle" (Compl. ¶29).
- Technical Questions: The complaint alleges the rake angle "continuously increases" based on a statement from an exhibit that the acute angle of the cross-section "decreases as it approaches the shank" (Compl. ¶29). This apparent contradiction raises a factual question as to how the accused file's geometry actually functions and whether it meets the claim limitation.
’173 Patent Infringement Allegations
| Claim Element (from Independent Claim 1) | Alleged Infringing Functionality | Complaint Citation | Patent Citation |
|---|---|---|---|
| An endodontic obturator, comprising: a tip region...; a shank region...; at least one obturator portion between the tip region and the shank region... comprising a body defining a taper; and a material layer containing gutta-percha, rubber, or resin... | The accused WOG Obturator Cones are endodontic obturators made of gutta-percha with a tip, a shank, and a tapered body. | ¶36-40 | col. 7:4-24 |
| ...wherein the at least one obturator portion includes, in a direction from the tip region towards the shank region, a first tapered obturator portion, a second tapered obturator portion, and a third tapered obturator portion, | The complaint alleges the WOG Obturator Cones have this structure because they are "system-matched" to the WOG Files, which have a decreasing taper design. | ¶41-42 | col. 24:61-64 |
| ...wherein the first tapered obturator portion, the second tapered obturator portion, and the third tapered obturator portion are of equal length... | The complaint alleges this structure is present based on diagrams depicting the multiple taper rates of the corresponding WOG Files (Compl. p. 15). | ¶41-42 | col. 25:16-19 |
| ...and the rate of taper for the first tapered obturator portion is greater than the rate of taper for the second... and the rate of taper for the second... is greater than the rate of taper for the third... | The complaint alleges the WOG Obturator Cones have this decreasing taper profile because they are designed to match the WOG Files, which are marketed as having a "decreasing percentage tapered design." | ¶41-42 | col. 25:20-27 |
- Identified Points of Contention:
- Evidentiary Questions: The complaint's allegations for the ’173 Patent rely heavily on inference. It argues that because the obturators are "system-matched" to the files, they must have the claimed structure (Compl. ¶42). A key question will be what direct evidence Plaintiff can produce to show the accused obturators actually have three adjacent, equal length portions with the specific decreasing taper rates required by the claim. The complaint provides diagrams of the files, not the obturators, to support these structural allegations (Compl. pp. 14-15).
V. Key Claim Terms for Construction
The Term: "rake angle continuously increases" (’605 Patent, Claim 1)
Context and Importance: The definition of "rake angle" and the requirement that it "continuously increases" are central to the infringement analysis for the ’605 Patent. Practitioners may focus on this term because the complaint advances a theory that a changing cross-sectional shape (a parallelogram) satisfies this functional limitation, a point that will likely be contested.
Intrinsic Evidence for Interpretation:
- Evidence for a Broader Interpretation: The specification defines "rake angle" with reference to a diagram as "an angle between the first side 1110 of the cutting edge 110 and the radius of circle 120" ('605 Patent, col. 11:34-38). A party could argue that any file geometry that alters this angle along its length in an increasing manner falls within the claim scope.
- Evidence for a Narrower Interpretation: The specification describes an embodiment where the rake angle increases from "approximately 5 degrees" at the tip to "approximately 20 degrees at the shank region" ('605 Patent, col. 11:52-55). A party might argue this specific example limits the interpretation of "rake angle" to a more conventional definition that may not encompass the effect of the accused product's "alternating offset" cross-section.
The Term: "of equal length" (’173 Patent, Claim 1)
Context and Importance: This term imposes a precise structural requirement on the three tapered portions of the claimed obturator. Infringement will depend on whether the accused products literally meet this geometric constraint. Practitioners may focus on this term because it is a clear, quantitative limitation that could be dispositive.
Intrinsic Evidence for Interpretation:
- Evidence for a Broader Interpretation: A party arguing for infringement might contend that "equal length" should be interpreted to mean functionally or substantially equal, particularly if arguing under the doctrine of equivalents.
- Evidence for a Narrower Interpretation: The plain language of the claim is specific. The patent also discusses embodiments with both "equal or unequal portions" ('173 Patent, col. 4:52-53), suggesting that when the patentee claimed "equal length," it was a deliberate choice to exclude "unequal" or "substantially equal" lengths from the scope of this particular claim.
VI. Other Allegations
- Indirect Infringement: The complaint alleges both induced and contributory infringement for both patents. Inducement is based on allegations that Defendant provides "advertising, marketing, sales, customer support, and other materials instructing customers" on how to use the products in an infringing manner (Compl. ¶57, 65). Contributory infringement is based on allegations that the products are especially made for infringement and are not staple articles of commerce (Compl. ¶58, 66).
- Willful Infringement: Willfulness is alleged based on Defendant’s purported knowledge of the patents. For the ’605 Patent, knowledge is alleged from at least August 24, 2020, via a notice letter (Compl. ¶52-53). For the ’173 Patent, knowledge is alleged based on the familial relationship to the ’605 Patent and, notably, a USPTO Office Action rejecting Defendant’s own patent application over the ’173 Patent family, which was subsequently abandoned by Defendant (Compl. ¶49-50, 53).
VII. Analyst’s Conclusion: Key Questions for the Case
- A core issue will be one of claim scope versus accused technology: can the term "rake angle," as defined and used in the ’605 Patent, be construed to read on the functional effect of the accused file’s "alternating offset parallelogram cross-section"? This will likely involve a significant dispute over both the legal definition of the claim term and the technical operation of the accused product.
- A key challenge for the plaintiff will be one of evidentiary proof: does direct evidence confirm that the accused WOG Obturator Cones possess the precise geometric structure required by Claim 1 of the ’173 Patent—specifically, three adjacent portions of equal length with decreasing rates of taper—or does the infringement theory rely solely on the inference that they are "system-matched" to the files?
- A third central question will concern willfulness: what was the extent of Defendant’s knowledge of the patents and intent to infringe, particularly in light of the allegations involving a prior notice letter and the prosecution history of Defendant's own abandoned patent application?