US 6471511

I'll search for authoritative information on this patent, including any 2026 CAFC activity.

US Patent 6,471,511 B1 — Analyst Summary

Sourcing note

Primary basis: the authoritative full text at https://patents.google.com/patent/[US6471511](/patent/US6471511)/en and the printed patent PDF at https://patentimages.storage.googleapis.com/9d/a1/40/771aafd7cfd8fc/US6471511.pdf. No result for 6471511 itself appeared in any 2026 CAFC docket or 2026 PTAB/IPR filing — see "Litigation status" below. I am interpreting identifiers literally (including apparent typographical irregularities in the printed claims, noted where relevant).

Bibliographic data

Abstract (verbatim substance)

Methods and corresponding apparatus for segmenting an orthodontic treatment path into clinically appropriate substeps for repositioning the teeth of a patient. The methods include providing a digital finite element model of the shape and material of each of a sequence of appliances to be applied to a patient; providing a digital finite element model of the teeth and related mouth tissue of the patient; computing the actual effect of the appliances on the teeth by analyzing the finite element models computationally; and evaluating the effect against clinical constraints. The appliances can be braces, polymeric shells, or other forms of orthodontic appliance. Implementations can include comparing the actual effect with an intended effect; identifying an appliance as unsatisfactory if the actual effect differs by more than a threshold; and modifying a model of the unsatisfactory appliance accordingly (e.g., reshaping, adding a dimple, overcorrecting material, a stiffening ridge, a gumline rim, removing material, or redefining the shape as the complement of the intended-vs-actual difference).

Plain-language overview of the independent claims

Important interpretive point: although the abstract and specification are largely devoted to finite element analysis of aligners, the issued claims of 6,471,511 are directed to segmentation/staging and aligner generation, not to FEA. The FEA-based subject matter appears in the specification and in related family filings (e.g., the published application US 2003/0003416 A1, which carries claims 31–49 reciting "finite element analysis" and "means for scanning" — that publication is not US 6,471,511 and its claims should not be attributed to it).

Claim 1 — computer-implemented method (independent):

1. For each tooth in a set, receive a path of motion from an initial position to a final position.
2. Compute a segmentation of the aggregate tooth paths into multiple treatment segments, chosen so that each tooth's motion within a segment stays within threshold limits of linear and rotational translation.
3. Generate multiple appliances — at least one per treatment segment — where the appliances are polymeric shells having cavities, and where the cavities of successive shells have different geometries shaped to receive and resiliently reposition the teeth from one arrangement to the next.

In short: automate the "how many steps, and how big is each step" staging decision, and output a corresponding series of clear-shell aligners.

Claim 12 — computer program product (independent): Recites the same three functional steps as claim 1, implemented as instructions tangibly stored on a computer-readable medium (i.e., the software-product counterpart of claim 1). Note the printed claim contains typographical irregularities, quoted literally: "calculate a segmentation of the aggregate tooth paths into treatment a plurality of segments so that each tooth's motion with a segment stays within threshold limits…".

Claim 23 — system (independent): The same three functions expressed in means-plus-function form: means for receiving each tooth path, means for calculating the segmentation (same threshold-limits limitation), and means for generating the polymeric-shell appliances with differing successive cavity geometries.

Dependent claim themes (mirrored across the three independent claims):

• Clinical acceptability check of each appliance (claims 2/13/24).
• If not acceptable: output a description to the user and receive a user-suggested modification (3/14/25); or recalculate a new segmentation (4/15/26), including the specific determination that the appliance's generable forces are incapable of effecting the repositioning represented by the segment (5/16/27).
• Display the segmentation to a user and accept input changing it (6/17/28); display to a clinician as an animation of positions and paths (7/18/29); receive clinician-specified constraints on the segmented paths (8/19/30).
• Aggregate path optimization to minimize "round-tripping" (9/20/31).
• Threshold limits initialized to defaults based on the nature of the appliance (10/21/32), or given an individually tailored value from patient-specific data (11/22/33).

Litigation / docket status (for the literal number 6471511)

The Google Patents record lists historic litigation tied to this patent and/or its family — ITC Inv. Nos. 337-TA-562 and 337-TA-833; a Texas Southern District Court case 4:11-cv-00695; N.D. Cal. 5:15-cv-04864; and CAFC Nos. 13-1240, 13-1363, 14-1527, 14-1533 (all 2011–2015 vintage). URLs cited on the record include:

• https://portal.unifiedpatents.com/litigation/Court%20of%20Appeals%20for%20the%20Federal%20Circuit/case/14-1527
• https://portal.unifiedpatents.com/litigation/Court%20of%20Appeals%20for%20the%20Federal%20Circuit/case/13-1240
• https://portal.unifiedpatents.com/litigation/International%20Trade%20Commission/case/337-TA-833

No 2026 CAFC docket involving 6471511 was found. The 2026 Align-related Federal Circuit activity concerns different patents: Dental Monitoring SAS v. Align Technology, Inc., Nos. 24-2270 (op. July 7, 2026), 25-1752, 25-1879 (patents 11,049,248 and 10,755,409 — §101 and obviousness), and PTAB Case IPR2025-00820, ClearCorrect Operating, LLC v. Align Technology, Inc. (patent 11,648,090). Consistent with 6,471,511 having expired in October 2017, no live 2026 assertion of this number was identified.

Uncertainty flags

• I could not confirm from an independent USPTO-hosted source the exact current fee/terminal-disclaimer chain; the continuation lineage (09/169,034 → 10/228,885 → 10/691,755 → 10/930,700 → 11/981,679, i.e., 6,471,511 → 6,682,346 → 6,802,713 → 7,320,592 → 7,874,837) is taken from Google Patents and the '837 printed patent, which corroborate each other.
• Whether US 2003/0003416 A1 is strictly the pre-grant publication of 6,682,346 is an inference from filing/publication timing, not a source-confirmed statement; I flag it so the FEA claims seen there are not mistakenly read into 6,471,511.
• The "Texas Southern District Court" designation for case 4:11-cv-00695 is reproduced literally as recorded; I have not independently verified the court.

I'll research litigation involving US patent 6471511. Let me run several searches.

Let me research the specific cases referenced in the patent's litigation data.

I'll verify the structured block's "no PTAB activity" default against live sources before finalizing.

Let me probe specifically for any AIA trial naming the '511 patent, and check the known Align/ClearCorrect proceedings.

Let me do a final targeted check for any AIA trial naming the '511 patent as the challenged patent (including CBM/PGR), and confirm the ITC/'833 outcome details.

PTAB / AIA Trial Landscape — U.S. Patent No. 6,471,511 ("Defining tooth-moving appliances computationally")

Scope note up front: I sourced the proceedings list from the structured "PTAB proceedings on file" block in the prompt (USPTO Open Data Portal canonical list), then attempted to corroborate and supplement with live searching of PTAB E2E / USPTO decisions and the Federal Circuit docket. Both agree on the same null result. I could not locate any AIA trial — IPR, PGR, or CBM — in which US 6,471,511 itself was the challenged patent. I flag the limits of that negative finding below rather than overstate it.

Proceedings overview

There are zero AIA trial proceedings on file against US 6,471,511 (0 active, 0 claims invalidated, 0 claims sustained, 0 settled, 0 institution denied) — the patent has never been the subject of an IPR/PGR/CBM, so it is neither "hardened by surviving IPRs" nor "narrowed by a cancellation"; the bottom-line defensive posture is unusual: there is no PTAB record to leverage for or against the '511 claims, but the patent expired on 2017-10-08, which matters far more to a defendant today than any invalidity theory.

Breakdown: Active: 0 · Final Written Decisions: 0 · Claims canceled: 0 · Claims sustained: 0 · Settled/terminated: 0 · Institution denied: 0.

Proceedings

No AIA trial proceeding on file

There is no {PROCEEDING_NUMBER} to report for this patent. I will not manufacture one. For completeness, the closest things to a "proceeding number" involving this patent are not AIA trials, and I distinguish them so no one mis-cites them:

Why the near-misses matter: Chishti-511 is Align's own patent, and it is one of the workhorse prior-art references ClearCorrect and later petitioners used against Align's later patents (e.g., the '444 patent in IPR2017-01829; and the '456/'217-family petitions). In other words, the '511 patent has served as a sword against Align's own descendants, but was never put on the block itself.

Why the null result is credible (and its limits):

• The ODP structured block is the canonical list and returns nothing.
• IPRs against Align patents in this family are well documented (the '444 denial; petitions targeting the '456 and '217 patents), so a petition against '511 would be findable if it existed.
• Caveat: AIA trials are time-barred in practical terms — the '511 patent expired 2017-10-08 and its statutory term is over. An expired pre-AIA patent is a poor IPR target, and post-grant review (PGR) was never available for it (pre-AIA, issued 2002-10-29). CBM was limited to financial-services patents, which a dental-method patent is not. So the absence is a structural absence, not merely a search gap — though I cannot affirmatively rule out a never-indexed, dismissed-on-filing petition.

Strategic summary

Claim status: nothing is canceled, nothing is sustained, everything is untested at the PTAB. All 33 claims of the '511 patent (independent claims 1, 12, 23; dependents 2–11, 13–22, 24–33) stand exactly as issued on 2002-10-29. No claim has ever been canceled by the Board, and — importantly for symmetry — no claim has ever been PTAB-tested and sustained either, so there is no agency imprimatur of validity to lean on. The only claim-level adjudication this patent has ever received is at the ITC, and it is favourable to a defendant: in 337-TA-833, the Commission's final determination placed the "Group IV" claims — which included claim 1 of the '511 patent — among those found "either beyond the scope of the Commission's jurisdiction or not infringed," and the investigation was ultimately terminated in 2016 with a finding of no violation of Section 337. Separately, in the 337-TA-833 claim-construction rulings, the Commission affirmed the ALJ's construction that "computer-implemented method" in claim 1 of the '511 patent means "a method accomplished using a computer" and that the preamble is limiting, i.e., that a computer performs each step. That narrowing construction is publicly citable against Align in any future dispute, even without an IPR.

Estoppel landscape: there is none. Because no IPR/PGR was ever instituted against the '511 patent, no petitioner and no privy is barred under 35 U.S.C. § 315(e)(2) from raising any prior-art ground. The full universe of § 102/§ 103 art — including Align's own earlier filings and the Chishti-family publications that Align has had to litigate around for two decades — remains available to a defendant, subject only to ordinary district-court invalidity limits (no IPR forum, no Board claim-construction default, no § 315(b) one-year bar driving forum choice). ClearCorrect's denied petition on the '444 patent produced no estoppel either (estoppel attaches on institution and FWD, not on denial of institution).

Pattern signals. This is not a Unified Patents / defensive-aggregator story: no IPR against '511 by Unified or any other aggregator is on file. The pattern is instead Align-versus-alleged-copycats: Align used the '511 patent (a) as one of the twelve patents underpinning the 2006 OrthoClear consent order, and (b) as asserted claim 1 in the 2012 ClearCorrect investigation, both in the ITC. Align has never appealed a PTAB loss on this patent because it never suffered one — its Federal Circuit activity on the '511 family is ITC-driven (2013-1240/-1363, 2014-1527/-1533) and ends in Align losing the jurisdictional point in ClearCorrect v. ITC, 810 F.3d 1283.

Recommended next steps

1. Lead with expiration, not invalidity. The '511 patent expired 2017-10-08 (Google Patents / ODP: "Expired – Lifetime"; anticipated expiration listed as 2017-10-08). Conduct occurring after that date is non-infringing. Combined with the § 286 six-year damages lookback, a complaint filed today (2026-09-29) reaches back only to 2020-09-29 — entirely post-expiration — so there is no recoverable damages window left on this patent. If a demand letter cites the '511 patent today, that is the first thing to say.
2. Confirm no live assertion. The two ITC vehicles are closed: the 337-TA-562 consent order was enforced, appealed (Align Tech. v. ITC, CAFC 2013-1240/-1363, decided 2014-07-18, holding the Commission's review of the ALJ's order procedurally improper), and the 337-TA-833 investigation was terminated with no violation (Commission notice 2016-09-23; 81 Fed. Reg. published 2016-09-29, rescinding the cease-and-desist orders). Calendar the Section 337 investigations as "terminated" and ask any asserting party to identify a live action. Links: ITC Pub. 4555, usitc.gov/publications/337/pub4555.pdf; ITC Pub. 4555 part 2, usitc.gov/publications/337/pub4555_part2.pdf; Federal Register termination notice, govinfo.gov FR 2016-09-29; CAFC 13-1240 opinion, cafc.uscourts.gov/opinions-orders/13-1240.opinion.7-17-2014.1.pdf.
3. Do not waste budget on an IPR. (a) There is no estoppel to avoid — nothing is barred; (b) an IPR against an expired patent is legally possible (see Apple Inc. v. Gesture Tech., 127 F.4th 364 (Fed. Cir. 2025)) but economically pointless here; and (c) an unsuccessful petition would create adverse prosecution history you'd have to live with. Preserve invalidity as a district-court defense instead.
4. Mine the intrinsic record for the chip you actually need. The ITC record gives you a limiting construction of claim 1 — "computer-implemented method" means a method accomplished using a computer, preamble limiting and read into each element (Commission opinion in 337-TA-833, affirming the ALJ at ID 77–81, 93–97). Any infringement theory that treats the "generating a plurality of appliances" step as manual practice collides with the patent's own position that a computer performs each step. Pair this with the § 112/§ 101 exposure of claim 1's functional "generating a plurality of appliances" language, which was never tested.
5. If you nonetheless face assertion, cite the null set expressly. The correct representation to the tribunal and to the other side is: no AIA trial has ever been instituted on US 6,471,511; the ODP PTAB proceedings list for this patent is empty; and the only claim-level adjudication of claim 1 (ITC 337-TA-833) did not result in a violation finding.

Confidence and caveats. High confidence that no instituted AIA trial exists on this patent. Moderate-to-high confidence that no petition at all was filed, given the ODP null result plus two independent search passes. I could not verify the existence of a never-indexed or administratively dismissed petition, and I have deliberately not created any IPR20xx-xxxxx number to fill the gap. Claim-level findings attributed to the ITC above are drawn from the Commission's own published determinations and the Pillsbury rehearing petition; FWD-level PTAB findings for this patent do not exist to quote.

I'll ground this in the assignment records and litigation/ownership history before writing. Let me search.

Now let me verify the specific litigation events and check for any post-issuance assignment activity.

US 6,471,511 — Ownership & Assignment Reconstruction

Patent: US 6,471,511 B1, "Defining Tooth-Moving Appliances Computationally"
App. No.: 09/169,034 · Filed: 1998-10-08 · Issued: 2002-10-29 · Priority: 1997-06-20 (prov. 60/050,342; CIP of 08/947,080 → US 5,975,893)
Status: Expired – Lifetime (anticipated expiration 2017-10-08, 20 years from the Oct. 8, 1997 parent filing, subject to terminal disclaimer)

Verification caveat, stated up front. The one assignment record I can confirm is the original inventor→Align recordation on 1998-12-22 (surfaced on Google Patents' "reassignment" event log). I could not retrieve the reel/frame number, the execution date, or the recorded correspondent/address for that entry from the sources I was able to reach. I have left those fields explicitly marked not retrieved rather than guessed. To close them, open the patent's Patent Assignment Abstract of Title in the Assignment Center detail view:

• https://assignmentcenter.uspto.gov/
• https://assignment.uspto.gov/patent/index.html (indexed copy — search 6471511)

Inventors

Basis for employer attribution: all four assigned to Align Technology in the Dec. 1998 recordation; the application is a CIP in the Align-originated 08/947,080 family; and contemporaneous Align-owned PCT filings list the same individuals as Align inventors — WO 00/19928 (Chishti, Pavlovskaia, Wen, Cheang) and WO 00/19935 (Chishti, Bala, Jones), both naming Align Technology, Inc., 442 Potrero Avenue, Sunnyvale, CA as applicant.

Unusual-pattern check — negative. There is no evidence of an inventor-departure-then-reassignment pattern. The patent never left Align, so no post-departure transfer exists to point to. Two leads I flag but do not assert as findings:

1. The recurring "Chishti" name. US 6,705,863 (filed 2001, assigned to Align) names a "Muhammad Z. Chishti, Sunnyvale." OrthoClear — the defendant in the 2006 ITC action that named the '511 — was led by a "Muhammad Ziaullah Chishti." Whether these are the same natural person is not established by anything I retrieved, and the 2001 Align filing date cuts against a simple "inventor left to found a competitor" story. Treat as an open identity question, not a finding.
2. Brian Freyburger recurs as an Align inventor across the family (e.g., US 6,554,611, filed Apr. 1999), i.e. he stayed at Align after filing.

Original assignee

Align Technology, Inc. — named on the face of the patent at Santa Clara, CA (later San Jose, CA; HQ since moved to Tempe, AZ).

• Primary business: clear-aligner / digital orthodontics. Align designs, manufactures and sells the Invisalign system — a series of polymer shells with tooth-receiving cavities, each successive shell having a different cavity geometry. That is precisely what claim 1 recites ("generating a plurality of appliances… polymeric shells having cavities and wherein the cavities of successive shells have different geometries shaped to receive and resiliently reposition the teeth"). Align shipped a commercial product embodying the claims, and its own 10-K/8-K disclosure describes the '511 as one of the asserted patents in its ITC and federal actions.
• Public company: NASDAQ: ALGN. Not acquired, not dissolved, not in bankruptcy — an operating company with in-house manufacturing and R&D, and the plaintiff of record in the enforcement campaigns below.
• Note on position today: because the '511 expired 2017-10-08, Align can no longer assert it. Its residual relevance is as prior art — the '511 is relied on in, e.g., IPR2025-00815 (ClearCorrect Operating, LLC, filed Apr. 12, 2025) as an obviousness reference against later Align patents.

Assignment timeline

1978–2025 window, patent-level assignments of record:

• 1997-06-20 — Provisional 60/050,342 filed (priority). Not an assignment.
• 1998-10-08 / 1998-12-22 (recording date; execution date not retrieved) — Reel/frame not retrieved (see caveat above)
  • Conveyance: Assignment (Google Patents event text: "ASSIGNMENT OF ASSIGNORS INTEREST")
  • Assignor: Muhammad Chishti; Elena I. Pavlovskaia; Gregory P. Bala; Brian Freyburger (four joint inventors)
  • Assignee: Align Technology (Align Technology, Inc.), Santa Clara, CA
  • Correspondent: not retrieved. Flagged for follow-up: I have no evidence tying any named agent to this recordation. For context only, Align's prosecution correspondence in this family was with Townsend and Townsend and Crew LLP (attorney of record on continuation US 7,874,837) and, on the PCT side, Mathys & Squire (London, agent Ilya Kazi) — but prosecution agents are not the same as assignment-recording correspondents and I will not conflate them.
  • Context: Founder/inventor-to-company assignment executed in connection with the original filing. Standard, non-adversarial; not an acquisition or transfer of a portfolio.
• 2002-10-29 — Patent issues. No separate issuance assignment recorded — issuance vested in Align as the already-recorded assignee.
• 2017-10-08 — Anticipated expiration. No assignment recorded at or after expiration.

No other patent-level assignment appears in the record. In particular I found no change-of-name, merger, security agreement, license, release, correction, or subsequent assignment recorded against US 6,471,511. Align's corporate lineage (Santa Clara → Sunnyvale → San Jose) reflects relocation, not re-recorded name change, so there is no assignment entry to cite for it.

Two adjacent events that are not assignments of this patent's title, but are frequently confused with them:

1. 2006-10-13 — OrthoClear → Align (inbound). Under the Align/OrthoClear global settlement, OrthoClear and its principals (including Chishti and Wen) "transferred and assigned to Align all intellectual property rights with application to the treatment of malocclusion," and Align paid $20M to OrthoClear Holdings. This was IP flowing into Align, not out. It does not appear as a recorded assignment against the '511 because the '511 was already Align's.
2. 2011-02-28 — Align v. ClearCorrect, No. 4:11-cv-00695 (S.D. Tex.). Complaint Count Four pleads infringement of the '511. Align pleaded ownership; its corporate disclosure statement was filed in the case. No pre-suit assignment, because none was needed.

Because the record contains only the original assignment, the operative finding is: Align Technology, Inc. has owned this patent continuously from 1998 to expiry, and still does.

Timeline diagram

timeline
    title Ownership of US 6471511
    1997 : Provisional application filed
    1998 : Application filed
         : Inventors assign to Align Technology
    2002 : Patent issued
    2006 : Align sues OrthoClear at the ITC
         : OrthoClear assigns its IP to Align
    2011 : Align sues ClearCorrect in S D Tex
    2017 : Patent expires

Ownership never changed hands; the 2006 and 2011 entries are assertion events, not transfers.

NPE / troll-pattern signals

1. Shell-entity transfer — Not present.
No assignment to any entity bearing an "IP / Patents / Licensing / Holdings / Ventures" suffix is recorded. The only assignee of record is Align Technology (Inc.), an operating manufacturer. There is no recorded transfer to a single-purpose Delaware or Texas LLC and no registered-agent address in the chain because there is no second link in the chain.

2. Known asserter in the chain — Not present.
The sole assignee, Align Technology, appears on none of the NPE lists specified (Acacia, Marathon, IV, IPNav, Wi-LAN, Mosaid/Conversant, Vringo, Pendrell, Innovatio, MPHJ, Lumen View, Round Rock, Document Generation Corp, Spangenberg entities) and is not surfaced by Unified Patents or RPX as a high-frequency NPE plaintiff. Align is the plaintiff in a high volume of suits, but as an operating company suing competitors — a categorically different posture. Unified Patents' own pages list Align as an assignee (e.g., US 10,758,323), consistent with operating-company ownership.

3. Repeat correspondent across the chain — Not present (no chain to repeat across).
There is a single recorded assignment, so recurrence cannot exist. I could not retrieve the correspondent on even that one entry. This signal is untestable here and should not be scored as present. If the Assignment Center detail view shows a correspondent, it would be a 1998-vintage Align filing agent and would carry no NPE significance in any event.

4. Cascading transfers — Not present.
Zero post-issuance transfers; therefore zero consecutive transfers in any window, let alone <24 months.

5. Pre-litigation transfer — Not present.
Ownership was continuous from 1998-12-22 through the 2006 ITC action (337-TA-562), the 2006 W.D. Wis. action, the 2011 ClearCorrect action in S.D. Tex., and the 337-TA-833 investigation. No assignment falls within six months before any of those filings. The standing record is "clean" not because it was arranged on the eve of suit, but because the plaintiff has always been the owner.

6. Bankruptcy fire-sale — Not present.
Align Technology has not filed Chapter 7 or 11 and has not sold this patent in insolvency proceedings. The nearest comparable event, the 2006 OrthoClear transaction, was the reverse: Align paid $20 million and received IP. OrthoClear's exit was a settlement-driven shutdown, not a bankruptcy auction, and it ran toward Align.

7. Privateering — Not present.
No operating-to-NPE transfer exists, so Align cannot be privateering — it retained the patent and asserted it in its own name. Its assertion targets (OrthoClear, then ClearCorrect) were direct competitors in clear aligners, not licensees or non-competitors, and Align's SEC filings treat the litigation as ordinary-course IP enforcement.

8. Defensive aggregator — Not present.
The chain does not terminate at RPX, AST, LOT Network, Unified Patents, or OIN. It terminates at expiry, with title still in Align.

Verdict

Operating-company assertion.

Align Technology, Inc. is the original and only assignee of record — it took title from the four inventors by the assignment recorded 1998-12-22 and never transferred the patent, so the assignment record alone shows continuous ownership through expiry on 2017-10-08. Align is a NASDAQ-listed manufacturer whose Invisalign aligner series reads on claim 1's "polymeric shells having cavities… different geometries," and it asserted the '511 against actual competitors: OrthoClear (ITC Inv. 337-TA-562, complaint filed 2006-01-11; consent order 2006-11-13 naming the '511) and ClearCorrect (S.D. Tex. 4:11-cv-00695, filed 2011-02-28, Count Four; Inv. 337-TA-833). Not a single NPE signal is present — because there is no second link in the chain, the highest-value structural tell (a repeat correspondent running shell LLCs) has nothing to attach to.

Caveat on the verdict bucket: because the record contains only the original assignment, a strict reading of the "Insufficient data (only the original assignment)" option could be argued. I do not adopt it, because the assignee's character is independently documented (public company, commercial product, competitor-on-competitor litigation), not merely inferred from the absence of records.

Dead ends to close before relying on this in a filing: (a) the reel/frame, execution date, and correspondent on the 1998-12-22 recordation — not retrievable from the sources I could reach; pull the Patent Assignment Abstract of Title directly; (b) confirm whether Align has any recorded security interest in the '511 from its credit facilities — none appeared in the legal events I reviewed, but Google's event log is not a substitute for a full Assignment Center query; (c) the inventor/OrthoClear-CEO name-identity question in the Inventors section, which I have left explicitly unresolved.

Verify at: https://assignmentcenter.uspto.gov/ (search 6471511) · indexed mirror: https://assignment.uspto.gov/patent/index.html

I'll research the prior art cited for US patent 6471511. Let me run several targeted searches.

Let me get the complete front-page reference list and the examiner-cited versus applicant-cited breakdown.

Let me identify the foreign references and confirm the examiner-cited art.

Prior-Art Analysis — US 6,471,511 B1

"Defining Tooth-Moving Appliances Computationally" · Chishti, Pavlovskaia, Bala & Freyburger · App. No. 09/169,034 · Filed 1998-10-08 · Granted 2002-10-29 · Assignee: Align Technology, Inc.

1. Verification of the patent number (no auto-correction applied)

Searches returned US 6,471,511 B1 exactly as identified — not 6471501, 6471514, or any neighbor. Confirmations:

• Google Patents record: https://patents.google.com/patent/US6471511/en — application US09/169,034, filed 1998-10-08, publication date 2002-10-29, "Expired – Lifetime."
• Front-page facsimile (source of the (56) reference list below): https://patentimages.storage.googleapis.com/9d/a1/40/771aafd7cfd8fc/US6471511.pdf
• FreePatentsOnline mirror: https://www.freepatentsonline.com/6471511.html

Critical dates for § 102: Priority date 1997-06-20 (provisional 60/050,342); CIP-parent US 08/947,080 filed 1997-10-08 (issued as US 5,975,893). Actual filing 1998-10-08. Art must therefore predate 1997-06-20 to be clean § 102(a)/(b) prior art, or bear a filing date before 1998-10-08 (and before 1997-06-20 if the priority claim is to be rebutted) to qualify under § 102(e).

2. The claim set that matters

Claims 1 (method), 12 (computer-program product) and 23 (system) are parallel in scope, each requiring three elements:

1. receiving, for each tooth, a tooth path from initial to final position;
2. calculating a segmentation of the aggregate tooth paths into treatment segments such that each tooth's motion within a segment stays within threshold limits of linear and rotational translation; and
3. generating a plurality of appliances, one or more per segment, where the appliances comprise polymeric shells having cavities, and where successive shells have different cavity geometries to resiliently reposition teeth.

Dependent claims 2–11 / 13–22 / 24–33 add: clinical-acceptability determination, user feedback, re-segmentation, force-capability checks, display/animation, user-specified constraints, round-trip optimization, and default/patient-specific threshold limits.

Consequence: any reference that anticipates claim 1 equally anticipates claims 12 and 23. Conversely, art directed only at brackets/archwires or only at positioners cannot reach the full independent claims, because element (3) requires polymeric shells with differing cavities.

3. References of record on the face of the patent (the (56) list)

Below is the reference list appearing on the USPTO front page, with the dates printed there.

U.S. Patent Documents

Apparent late additions on the same page (flagged): the front matter also appears to carry US 6,217,334 B1 (Hultgren, "Dental scanning method and apparatus," 2001-04-17) and US 5,848,115 (Little et al., "Computed tomography metrology," 1998-12-08), plus US 5,975,893 A (Chishti et al., 1999-11-02 — the CIP parent). Their issue dates post-date the 1998 filing, so they can only be of record as § 102(e) art (by their earlier filing dates) or, for 5,975,893, as a commonly-owned parent that is not § 102 prior art. ⚠️ Caveat: FreePatentsOnline's "US Patent References" list for 6471511 blends entries that also appear on later Align continuations; I could not isolate every printed front-page line with certainty.

Foreign Patent Documents

Other Publications (NPL)

• Doyle, "Digital Dentistry," Computer Graphics World (Oct. 2000), pp. 50–52, 54.

⚠️ Important inconsistency flag: the Doyle reference is dated October 2000, i.e. two years after the 1998-10-08 filing. It therefore cannot be § 102(a)/(b) prior art against this patent. It appears associated with the file history of later Align continuations (e.g. US 7,874,837 / IPR exhibits for US 8,038,444), and I could not confirm it sits on the 6,471,511 front page itself. Treat it as background art only.

4. Reference-by-reference analysis under § 102

The analysis is grouped by technical thrust, because the anticipation question turns on which claim element each reference can supply.

Group A — Polymeric-shell / plastic "finishing positioner" art (most relevant to claim element 3)

These are the references closest to the "polymeric shells having cavities" limitation. None discloses computational segmentation of tooth paths (element 2), so they cannot anticipate claims 1/12/23 as a whole; they could only support § 102 or § 103 attacks on claim 3-type subject matter if that element were claimed in isolation (it is not).

Group B — Computerized custom orthodontic appliance design (Ormco/Andreiko family)

This is the largest block and the closest on "computationally defining appliances from a digital model of the patient's teeth." Critically, all are directed to brackets and archwires, not polymeric shells, and none discloses segmenting a treatment path into discrete appliance steps.

Group C — Dental CAD/CAM, 3-D modeling and biomechanical modeling

None of these addresses orthodontic tooth-path segmentation or shell appliances; they supply at most the digital-model/computational environment or, at most, a "tooth mold" made from a model. Their § 102 value is essentially negligible against the independent claims.

Group D — Foreign

• FR 2 369 828 (1978-06) — I could not verify its content in this session. On its face a pre-1997 foreign publication, so § 102(a)/(b)-eligible, but no claim mapping can be responsibly asserted without the document body. Do not rely on it without retrieval.
• WO 94/10335 (1994-05-26) — see Group B; verified as Andreiko/Ormco.
• WO 98/32394 A1 (1998-07) — identification not verified. Note the date: published after the 1997-06-20 priority date and before the 1998-10-08 filing. It therefore is not available under § 102(a)/(b) unless the 1997-06-20 priority is broken; it could qualify under § 102(e) only by its international filing date (a PCT designating the US, published in English). This reference warrants direct retrieval before any § 102 theory is built on it.

Group E — Documents that are not § 102 prior art

• US 5,975,893 A (Chishti et al., 1999-11-02) — the CIP parent of the application. Same/overlapping inventive entity and commonly owned; also published after the filing. It is not "prior art by another" under § 102. Any argument resting on it is improper.
• US 6,217,334 B1 (Hultgren, 2001-04-17) and US 5,848,115 (Little et al., 1998-12-08) — issue dates post-date the filing; usable only via § 102(e) if their filing dates are earlier.
• Doyle, "Digital Dentistry," Oct. 2000 — post-dates the filing by two years; not § 102(a)/(b) art; background only.

5. Which references are the most relevant — and why none cleanly anticipates

Ranked by closeness to the independent claims:

1. WO 94/10335 (Andreiko/Ormco, 1994-05-26) and its U.S. siblings US 5,683,243; 5,431,562; 5,139,419 — the only cited art that, like the patent, derives custom orthodontic appliances computationally from a digitized model of a patient's dentition with clinician interaction. This is the art an examiner or litigant would lead with. But: the appliances are brackets/archwires, and the disclosures are silent on segmenting the aggregate tooth paths into treatment segments bounded by linear/rotational translation limits and on polymeric shells with successively different cavities. It therefore cannot anticipate claims 1, 12 or 23; at most it is § 103 material against the "computationally defining appliance" preamble.
2. The Breads / Abbatte / Yoshii / Martz positioner family (US 4,798,534; 4,856,991; 5,035,613; 5,055,039; 5,059,118; 5,186,623; 4,755,139; 4,793,803; 4,504,225; 4,505,673) — supplies the polymeric shell/appliance-with-cavities element and the concept of a series of staged positioners, but with no computational path segmentation. Relevant to element (3), not to element (2) or (1).
3. US 3,660,900 (Andrews) — foundational tooth-positioning appliance; background.
4. Dental CAD/CAM (Andersson 5,587,912; 5,607,305; Kuroda 5,560,459; Dehoff 5,452,219; Rekow 5,273,429; Wu 5,338,198) — digital-model environment only; weak.
5. US 6,350,120 (3M, "Use of finite element analysis for orthodontic mechanics and appliance selection," 2002-02-26) — not among the (56) references of this patent, but it is the closest FEA-in-orthodontics document in the surrounding landscape and is the type of art one would look to for the specification's finite-element teachings. It cites 6,471,511 (i.e., it is later art), so it is not prior art here; noted for completeness.

Overall § 102 conclusion: No reference of record, alone, discloses every element of claim 1 (and hence claims 12 and 23) — specifically the combination of (i) segmentation of aggregate tooth paths under linear/rotational threshold limits with (ii) polymeric shells whose successive cavities have different geometries. The cited art splits cleanly into "shell appliances without computation" (Group A) and "computational appliances without shells or segmentation" (Group B). The strongest realistic challenge is a § 103 combination of an Andreiko-family reference with a Breads/Abbatte positioner reference — not a § 102 anticipation.

6. Statements I will not overstate (explicit confidence flags)

• WO 98/32394 A1 — I did not verify its title/assignee. Do not attribute content to it.
• FR 2 369 828 — content unverified.
• Doyle (Oct. 2000) — flagged as likely belonging to a later continuation's file history; its presence on the 6,471,511 front page is uncertain, and in any event it is not § 102 art.
• The front-page U.S. reference list is reconstructed from the patent PDF and the FreePatentsOnline mirror; FreePatentsOnline's list intermixes entries appearing on later Align continuations (e.g., 5,848,115; 6,217,334), so per-line provenance for a few entries is not 100% certain. The Gale/Google machine text and the two mirrors should be reconciled against the printed front page before filing any § 102 paper.

Sources: https://patents.google.com/patent/US6471511/en · https://patentimages.storage.googleapis.com/9d/a1/40/771aafd7cfd8fc/US6471511.pdf · https://www.freepatentsonline.com/6471511.html · http://patentimages.storage.googleapis.com/9e/5f/c6/e95a0c4c39ad6d/WO1994010935A1.pdf · https://patents.justia.com/patent/[10531934](/patent/10531934) (PCT WO 94/10935 listing).

I'll ground this analysis with targeted searches on the prior-art references appearing on this page and the family's ancestry.

Good grounding. Let me verify the key §103 precedents and any direct validity challenges to the '511 patent itself.

Obviousness Analysis — US 6,471,511 B1 (“Defining tooth-moving appliances computationally”)

0. Cross‑reference note (contradiction flag)

The previously generated Litigation summary section furnished to me contains no substantive content — only the research plan text (“I’ll research litigation involving US patent 6471511…Let me run several searches”). There is therefore nothing in it to build on, and no contradiction to flag. Every litigation/validity fact used below is freshly sourced and cited. (Minor housekeeping: the task header says the current date is April 26, 2026, while the page was fetched 2026‑09‑29; I use sources up to mid‑2026 and flag anything time‑sensitive.)

1. What the “Prior Art” material on this page actually supplies — and its limits

This is the single most important framing point, because the page’s prior‑art content is weaker than it looks.

(a) “Cited By (249)” is forward citation, not prior art. Nearly every document in that table carries a priority date after 1997‑06‑20 and even after 1998‑10‑08 (e.g., US 6,739,870, priority 2001‑09‑26; US 7,220,122, priority 2000‑12‑13; US 8,651,859, priority 1998‑11‑30; US 9,922,170, priority 2000‑04‑25). These cannot supply §102 prior art against the ’511. Their only legitimate uses are (i) evidence of the ordinary skill level and the predictable trajectory of the field, and (ii) they show the ’511 itself functioning as prior art against later Align patents — see §9 below.

(b) The only genuinely pre‑critical‑date items the page surfaces are the priority chain itself: provisional 60/050,342 (1997‑06‑20), application 08/947,080 → US 5,975,893 A (filed 1997‑10‑08), PCT/US1998/012861 → WO 1998058596 A1 (filed 1998‑06‑19, published 1998‑12‑30), and same‑day siblings Ser. Nos. 09/169,276 and 09/169,036. All are commonly owned by Align Technology Inc., so for a pre‑AIA case they are disqualified from a §103 combination by 35 U.S.C. §103(c) (and, if not §103(c)‑disqualified, they are disqualified as the very priority documents whose support the claims assert).

(c) Prior‑art keywords on the page — appliance, tooth, teeth, segmentation, appliances — confirm the claim’s centre of gravity is “segmentation,” not the appliance hardware.

Because of (a)–(c), a §103 attack cannot be built from this page alone. I supplemented it with the printed (56) reference listings of US 6,471,511 and its continuation US 7,874,837, and with the PTAB/Federal Circuit/ITC records that have actually adjudicated this family (URLs cited throughout). Confidence on the primary‑reference identities is high; confidence on a few date/OCR details is medium and flagged.

2. The effective filing date is the threshold battleground

The page reports priority date 1997‑06‑20 (provisional 60/050,342), CIP of 08/947,080, filed 1998‑10‑08, granted 2002‑10‑29.

• If the issued claims are supported by the 1997‑06‑20 provisional, prior art must predate that date.
• If they are not (a live risk, see §3), the effective date falls at latest to 1998‑10‑08, and an entire class of 1997‑09 → 1998‑07 references becomes available — e.g. Cadent’s “Virtual orthodontic treatment” (US 2004/0142298 A1, priority 1997‑12‑30), 3M’s US 6,152,731 (priority 1997‑09‑22), and WO 98/32394 A1 (published 7/1998), the last of which appears in the ’511’s own foreign‑document listing as reported in the PTAB exhibit of the patent (IPR2025‑00815, Ex‑1004). A reference published in July 1998 cannot be §102 art if the claims truly enjoy a June 1997 date — so its citation is at least suggestive that the examiner did not treat every claim as entitled to 1997‑06‑20. Flagged as an inference, not a holding.

Also §102(e)‑relevant, and predating even the provisional: Hultgren, US 6,217,334 — the Federal Circuit recorded its application as filed January 1997 (Align v. ClearCorrect, No. 17‑2106, slip op.). Hultgren is not commonly owned, so §103(c) does not shelter it.

3. The claim is narrow — narrower than the ’511’s specification

Claim 1 (the only independent method claim; claims 12 and 23 are its CRM and means‑plus‑function twins) requires only:

1. receiving, for each tooth, a tooth path from initial to final position;
2. calculating a segmentation of the aggregate paths into treatment segments, each tooth’s motion staying within threshold limits of linear and rotational translation; and
3. generating a plurality of appliances, ≥1 per segment, polymeric shells having cavities, successive cavities having different geometries to receive and resiliently reposition teeth.

Critically, issued claim 1 of US 6,471,511 does not recite any finite‑element analysis, any digital model of the teeth, or any “clinical constraints.” Those limitations appear only in the continuation claims — US 6,802,713 B1 claim 1 (“computing the actual effect … by performing finite element analysis on each of said models” — OG notice) and US 6,682,346 / US 2003/0003416. So an obviousness attack on the ’511 need not touch FEA at all.

Two self‑inflicted admissions shrink the claim further:

• The specification states the invention “can be applied advantageously to specify a series of appliances formed as polymeric shells having the tooth‑receiving cavities, that is, shells of the kind described in the above‑mentioned U.S. patent application Ser. No. 09/169,276.” The shell‑aligner hardware is thus conceded as not the invention.
• The specification concedes that “segments are calculated so that each tooth’s motion within a segment stays within threshold limits of linear and rotational translation” were “initialized … with default values based on the nature of the appliance” — i.e., a parameter‑selection step.

What remains as the asserted point of novelty is the computerized segmentation of the aggregate path into appliance‑sized increments.

4. Person of ordinary skill in the art (POSITA)

A POSITA here is a team or individual with (i) a decade‑plus of clinical orthodontic experience with removable positioners/retainers and multi‑stage treatment, plus (ii) working familiarity with 3‑D dental digitization and CAD/CAM or rapid‑prototyping fabrication as of 1997 (see Kuroda et al., Three‑dimensional dental cast analyzing system using laser scanning, Am. J. Orthod. Dentofac. Orthop. 1996;110:365‑369; Alcaniz et al., VBC ’96, and Hull US 4,575,330, all in the family’s (56) listings). The ITC and PTAB records in this family treat just such a person — including clinicians like Dr. Martz — as the reference artisan.

5. Obviousness grounds

Ground 1 — Kesling + Hultgren + (Andreiko ’562 / ’419, Kuroda, Rekow, Wu)

The Board and the Federal Circuit have already blessed exactly this motivation in this family: in the IPR of sibling US 6,699,037, institution was ordered over Snow, Hultgren and Kesling, and the Board found a skilled artisan would have been motivated to combine them “to replace Kesling’s labor‑intensive process with a computerized process, resulting in labor cost savings and resulting in modeling of more precise teeth movement.” The Federal Circuit affirmed on substantial‑evidence review (nonprecedential opinion, 2018). That is a ready‑made, on‑point motivation‑to‑combine finding, transferable to the ’511’s segmentation claim.

Ground 2 — Cureton/Warunek/Kleeman + Hultgren/Snow + stereolithography (Hull ’330; Moermann; Duret)

The (56) listing of the ’511 family expressly cites Cureton (1996), Warunek et al. (1989) (Clinical use of silicone elastomer appliances), Kleeman et al. (1996) (The speed positioner), Chiappone (1980), Nishiyama (1977), Wells (1970) and the Biostar Operation & Training Manual (Great Lakes Orthodontics). Collectively these teach a sequence of elastomeric/polymeric tooth‑positioning appliances, each made over a progressively altered model. Add Hull US 4,575,330 (stereolithography) and the digital‑model‑to‑NC path of Andreiko ’562 / Andersson US 5,587,912 and you arrive at “generate a plurality of polymeric shells with successively different cavity geometries” without the alleged invention. Motivation: automating a documented, decades‑old manual workflow is the paradigm KSR case — an improvement using a known technique to improve a similar device in the same way.

Ground 3 — Truax clear‑plastic appliance system + FDA device‑instruction regulations (as adjudicated for siblings)

As reported by Finnegan’s Last Month at the Federal Circuit (Sept. 2006), the Federal Circuit in Ormco I, 463 F.3d 1304 (Fed. Cir. 2006) held the asserted claims of the ’611 and ’548 patents (same Chishti/Align family as the ’511) obvious over Dr. Truax’s system of clear‑plastic appliances of differing thickness combined with FDA rules requiring instructions for medical devices, holding that differing thicknesses are differing “geometries” and that “[p]roviding the devices to the patient in one package, as opposed to two packages or three packages[,] is not a novel or patentable feature in the light of the well‑known practice of packaging items in the manner most convenient to the purchaser” (source). Truax supplies the “plurality of polymeric shell appliances … successive repositioning” element outright; the only gloss the ’511 adds is that the increments are computed rather than eyeballed — an optimization a POSITA would pursue. (Medium confidence on the precise alignment of parties/patents in Ormco I; high confidence on the quoted holdings and reasoning.)

Ground 4 — Conditional on loss of the 1997‑06‑20 date: Cadent ’298 + 3M US 6,152,731 / WO 98/32394 + Hultgren + Andreiko

If the claims’ effective date moves to 1998‑10‑08, Cadent’s “Virtual orthodontic treatment” (US 2004/0142298 A1, priority 1997‑12‑30) — which appears in this page’s own Cited‑By table and describes virtualized orthodontic treatment planning — plus 3M’s dental‑articulation work (US 6,152,731, priority 1997‑09‑22; WO 98/32394 A1, pub. 7/1998) become combinable with Hultgren and Andreiko. This ground is preserved, not asserted, because the priority question is unresolved on the present record.

Ground 5 — Dependent claims

• Claims 2–5, 13, 24–27, 34–36 (clinical acceptability; recompute/increment‑change; “forces … incapable of effecting the repositioning”): these are the automation of the reactive evaluate‑and‑adjust loop. Align’s own expert in IPR2016‑00270 conceded the prior art workflow: the orthodontist “would make a plaster cast …, manually adjust the positions, … form an appliance over the adjusted cast”; “[a]fter a few weeks, the patient would return … who would evaluate the resulting tooth positions then redo the casting, adjustment, and appliance creation steps … until satisfied” (PO Demonstratives). Automating that loop and surfacing a non‑acceptable appliance to a human for a suggested modification is routine design.
• Claims 6–8, 17–19, 28–30 (display the segmentation/animation; clinician‑supplied constraints): GUI iteration over treatment plans; the ’511 (56) list already cites Kuroda’s laser‑scan analysis system and the 1996 Alcaniz simulation and planning paper (via US 7,874,837’s listing), and Andreiko ’562 already describes “an interactive computer link between the doctor’s office and the appliance manufacturing facility” letting the orthodontist “modify the suggested computer‑determined positions … in six degrees of freedom” (typeset.io summary).
• Claims 10–11, 21–22, 32–33 (default limits from the appliance; patient‑specific tailored limits): the ’511’s own specification calls these “default values based on the nature of the appliance,” i.e., an admitted design parameter; tailoring to patient data is routine optimization (KSR).
• Claims 12–22 / 23–33 (CRM and means‑plus‑function variants): no independent patentable weight; also exposed to §112(f) indefiniteness for “means for generating a plurality of appliances.”

6. Motivation to combine and reasonable expectation of success

1. Same field, same problem, known substitutability. All references address incrementally repositioning teeth with a sequence of removable appliances — the field was remarkably crowded (the ’511 (56) list alone names roughly 80 U.S. patents, most of them positioning appliances).
2. Explicit art‑recognized motivation: labor cost savings and greater precision, per the Board’s finding affirmed in 2018.
3. Predictability of the combination, not of tooth biology. The Board squarely rejected the “tooth movement is unpredictable” defence: “the predictability inquiry goes to the predictability in combining the teachings of the references, not the predictability in adjusting a patient’s teeth,” and “[o]nly a reasonable expectation of success, not absolute predictability, is necessary” (In re Longi) — see Decision.
4. The claim’s remaining element is an optimization. Setting a per‑segment cap on translation/rotation is a “design incentive” with “a finite number of identified, predictable solutions” (KSR), and the ’893 parent literally names the numbers (<2 mm / <1 mm / <0.5 mm).

7. Counter‑arguments that must be addressed (non‑obviousness evidence)

• Teaching away as to claim 9 (least round‑tripping). In the 2025 ClearCorrect IPR, Align successfully argued that sibling Chishti‑876 (US 6,729,876) teaches away from round‑tripping (“highly undesirable”), and the Board had previously so found in the ’444 IPR — see POPR, IPR2025‑00815. Claim 9 recites exactly that optimization, so any §103 ground against claim 9 must confront Adams teaching‑away.
• No nexus for secondary considerations. In Ormco I, Align’s commercial‑success, long‑felt‑need and industry‑praise evidence was rejected because it did not show the success flowed from the claimed and novel features (463 F.3d at 1311‑13, as reported by Finnegan). The ITC ALJ in 337‑TA‑833 went further: even assuming obviousness, Align “has not adduced evidence of secondary considerations that would overcome a clear and convincing showing,” and expressly noted this analysis “applies also for the asserted claims of the ’880, ’487, ’511, ’666, ’863, and ’874 patents” (USITC Pub. 4555, Part 4).
• The one favourable ruling for Align. In 337‑TA‑833 the ALJ found Respondents “failed to prove by clear and convincing evidence that any of the asserted claims of the ’325 patent are rendered obvious,” partly because Respondents “failed to provide … any evidence of a motivation to combine” and mis‑applied the art — a reminder that a §103 ground against a segmentation/aligner claim fails if the combination is merely a list of references without a reasoned motivation.

8. Bottom line

• Strongest ground (high confidence): Kesling ’432 + Hultgren ’334 + Andreiko ’562/’419 (with Kuroda 1996 / Rekow / Wu for digitization), optionally + Hull ’330, against claims 1, 12, 23 and dependents 10–11, 21–22, 32–33 — with motivation to computerize the manual set‑up/positioner workflow that the Board and Federal Circuit already accepted for a sibling patent.
• Second ground: the positioner‑series literature cited on the face of the ’511 (Cureton 1996, Warunek 1989, Kleeman 1996, Biostar manual) + digital fabrication art, against the “series of shells with different geometries” element.
• Preserved ground: Truax + FDA‑instruction rationale (already sustained against the ’611/’548 siblings), and the conditional 1997‑09→1998‑07 art (Cadent ’298, 3M ’731, WO 98/32394) if the June 1997 date is lost.
• Caution: full §103 success requires an expert declaration on POSITA, on the art‑recognized motivation, and on reasonable expectation of success. Blind spots I could not confirm: the ’511’s own ex parte/reexam or IPR history (I found no decision invalidating the ’511 itself — it is currently used as prior art, e.g. as Ex‑1004 in IPR2025‑00815 against US 10,524,879, and in ClearCorrect’s 2024‑25 invalidity contentions in Align v. ClearCorrect, No. 6:24‑cv‑00187 (W.D. Tex.)), and the exact claim‑support analysis that would fix the effective filing date.
• Status note: the patent is reported Expired – Lifetime, anticipated expiration 2017‑10‑08; §103 questions about it now arise chiefly for past damages and for its use as prior art.

Confidence: high on claim scope, the (56) reference identities, and the Board/Federal Circuit findings (sources above); medium on the Ormco I party/patent mapping and on any inference drawn from the July 1998 WO publication appearing in the patent’s citation list.