US 3924333

US Patent 3,924,333 — Verification Summary

Search scope note: I searched for the exact identifier. Results confirm the record below (Google Patents, Justia, FreePatentsOnline, and USPTO-derived document listings). I found no CAFC 2026 docket, PTAB proceeding, or district-court litigation involving US 3,924,333. Given the patent expired in 1992, absence of litigation is expected, not surprising — but I want to be explicit that I could not query PACER/CAFC docket systems directly, so this is a negative search result rather than a certified "no litigation exists" statement.

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Bibliographic Data (high confidence)

Abstract (as published): A dental appliance for collecting solid debris and evacuating liquid from a patient's mouth during dental operations. Left and right tongue guards are connected to a bite block by a scoreline structure, so either guard can be broken off to work on one side of the mouth. The bite block attaches to a tongue guard member bearing against the lingual tissue of the lower arch; the guard has channels on its front face communicating with an evacuation tube, so fluids injected by drills are drawn out through the channels. A flexible collector is removably connected to the tongue guard and extends through the retromolar space and vestibule, lies against tissue over the ascending ramus, and extends over the palate conforming to the lingual gingiva of the maxillary teeth and palate.

Three claimed components: (1) semi-rigid bite block 10, (2) combination anchoring/evacuating "tongue guard" member 12/12a, (3) flexible collector 14 (fluid-impervious paper).

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Independent Claims in Plain Language

Claim 1 — The three-part isolated-field appliance

A dental evacuation appliance comprising:

• A semi-rigid bite block gripped between the molars on either side of the mouth. Key functional limitation: it deforms on the patient's initial bite to mold itself to the mouth for secure placement, then resists further deformation so the patient can bite hard without dislodging it. (The spec explains the mechanism: polystyrene compresses and densifies locally, becoming rigid.)
• A combination anchoring-and-evacuating member connected to the bite block and captured in the mouth, bearing against the lingual gingiva. Channels are formed in both the evacuating member/bite block (for fluid from the forward compartment) and in the bite block (for fluid from the back compartment).
• A resilient, removably connected collector that extends from the evacuating member through the retromolar space into the vestibule, rests on tissue overlying the ascending ramus, and extends over the palate to conform to and lie on the maxillary gingiva — separating the mouth into a forward (working) compartment and a rear compartment and diverting collected fluid/saliva back to the evacuating member.

Practical reading: One device that simultaneously acts as a bite prop, a tongue barrier, a two-compartment dam, and a suction manifold. Note claim 1 recites "linqual" (sic) — I am reading the term literally as it appears.

Claim 7 — The left/right convertible kit

A dental appliance formed as a combination left-and-right-side device: a bite block gripped by the last molars on one side or the other, initially carrying a pair of combination evacuating members — one for work on the left side, one for the right — where the evacuating members are removable from the bite block so the appliance can be placed on whichever side is being worked on.

Practical reading: A single molded part that a dentist configures chairside by snapping off the unneeded side, giving one product SKU that serves both quadrants. The abstract and spec describe this as a frangible scoreline arrangement (recited in dependent claim 8).

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Dependent Claim Map

Depending from claim 1:

• 2 — collector contoured to circumferentially seal the mouth into the two compartments
• 3 — evacuating member is unitary with the bite block
• 4 — evacuating conduit seated in the bite block, in fluid communication with the channels
• 5 — collector is adhesively coated for ready attachment
• 6 — collector may be gathered into a cup-like contour to collect solid debris and divert fluids

Depending from claim 7:

• 8 — evacuating members attached by a frangible scoreline structure
• 9 — adds the flexible removable collector (retromolar space, ascending ramus, palate; separates forward/rear compartments)
• 10 — bite block is semi-rigid, molds on initial bite, resists further deformation without losing placement
• 11 — channels in the front face of the evacuating members communicating with an evacuator
• 12 — adhesive coating on the collector's back face, forming a longitudinal closure for the channels
• 13 — collector gather-able into a cup-like contour

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Points of Uncertainty / Caveats

1. Assignee: No assignee is recorded; the patent issued to the inventor as an individual. I did not independently verify the USPTO Assignment database for any post-issuance assignment.
2. No CAFC 2026 activity found. The only 2026 Federal Circuit material surfaced in search concerned unrelated patents (e.g., U.S. 11,208,029 B2). I cannot rule out a docket entry invisible to web search.
3. False-positive identifier matches that must NOT be conflated (per the literal-identifier rule, these are distinct from the patent):
   • JP 3924333 B2 — a Japanese patent (General Electric, "複合ブレード" / composite blade, registered 2007) — a completely different document that merely shares a numeric string.
   • FEI/EIN 88‑3924333 and 38‑3924333 — Florida LLC corporate filing numbers (ANY'S WAYUU LLC; W.D.L. INVESTMENTS, INC.) — unrelated administrative identifiers.
   • Astronomy catalog entry 3924333 in a NASA Kepler K2 data release notes document — unrelated.
4. Two later patents cite this patent: US 4,192,071 (Erickson, 1980 — a related but distinct dental appliance) and US 4,281,986 (Erickson, 1979/1981). The '986 specification expressly characterizes US 3,924,333 as "having merit" but "too complex" and subject to the deficiencies of saliva-pump appliances — useful inventor's own-admission prior art if you are building a prosecution history or invalidity narrative around the Erickson family.

I'll search litigation-focused sources for any cases involving US Patent 3924333.

The first pass returned only an unrelated Ford case and a prior-art citation list. Let me search litigation-specific databases.

Let me check CourtListener and any litigation database records for this specific patent.

Answer: No litigation known involving U.S. Patent 3,924,333

I searched litigation-oriented sources (including the Unified Patents litigation case list, Justia/Justia dockets, CourtListener, Docket Alarm, PTAB/USPTO filings, and general web searches keyed to the exact number "3924333" and "3,924,333"). I found no record of any civil action — filed, pending, or terminated — in which U.S. Patent 3,924,333 was asserted or challenged in a U.S. district court, the ITC, or the Federal Circuit.

What the searches actually returned (and why each is a false positive)

Case-by-case table

Because no cases exist, there is nothing to populate for plaintiff, defendant, jurisdiction, case number, filing date, or status:

• Plaintiff(s): None found
• Defendant(s): None found
• Jurisdiction: N/A
• Case number: N/A
• Filing date: N/A
• Outcome/status: N/A

Important caveats and corroborating context

1. This is a single-inventor, 1974 patent to Norman Erickson of Escondido, California, which was granted December 9, 1975 and reached its anticipated expiration on December 9, 1992 (per the Google Patents legal-status record: "Expired – Lifetime"). Any enforcement action would predate 1993, when electronic docketing coverage was sparse — so my search cannot rule out a pre-1993 suit, only that none appears in indexed, searchable sources.
2. The patent's own family is small. Its forward citations are almost entirely patent citations, not litigation: later Erickson patents (US 4,192,071; US 4,281,986; EP 0 026 992) and third-party patents (Schubert US 4,167,814; Dyfvermark US 4,975,057; Kanas US 5,232,362; Duggan US 5,152,686; the Ultradent and Ascentcare/Solmetex families) that cite it as background art.
3. The only proceedings anywhere near it are PTAB/IPR-style matters in which it was cited as prior art against other people's patents — which is the opposite of litigation involving 3,924,333.

Conclusion: Based on the sources searched, no litigation is known involving US Patent 3,924,333. If you need a definitive negative, I would recommend running a paid litigation-history search (Westlaw KeyCite / Lexis CourtLink "patent history," or a Docket Alarm / Unified Patents Patent Litigation search limited to pre-1993 records), since those databases have deeper historical coverage than the free sources available here. I should also flag that I could not complete every planned query before my search budget ran out, so this is a strong but not exhaustive negative.

I'll verify the structured data with a quick search before writing up.

Let me confirm whether 3924333 was ever a challenged patent (as opposed to being cited as prior art inside someone else's IPR).

Proceedings overview

Zero AIA trial proceedings have ever been filed against US 3924333 — the structured "PTAB proceedings on file" block returns no AIA trials, and my independent web searches surface no IPR/PGR/CBM naming this patent as the challenged patent, so the breakdown is 0 active / 0 claims invalidated / 0 claims sustained / 0 settled / 0 institution denials; the bottom line for a defendant is that all 13 claims are untested, not hardened — the reason there is no PTAB record is that the patent expired on 1992-12-09 (per the anticipated-expiration entry in the patent's own Google Patents record), roughly 20 years before the first IPR was even filable (AIA trial practice began 2012-09-16), so there was never a window in which an AIA petition could have existed.

No proceedings to report

There is no ### {PROCEEDING_NUMBER} entry to write because there is no proceeding. I will not fabricate a docket number to fill the template. The four search passes I ran returned only:

• US 3924333 appearing as prior art / an IDS-style citation inside other parties' PTAB papers and later patents, never as a challenged patent (e.g., it appears in a prior-art search exhibit filed in a PTAB proceeding at ptacts.uspto.gov petition 1558007, and in the prior-art listing of a 3Shape Medical A/S proceeding record at ptacts.uspto.gov petition 1463399 — in both instances as a "document identifier" reference in a search/IDS exhibit, not as an instituted ground I can confirm).
• Unrelated coincidental hits ("3924333" as a Florida FEI number, as a NASA K2 target ID) — not the patent.

Every place US 3924333 shows up in the AIA-trial corpus, it is on the prices-in side of the ledger: a 1975 dental-evacuation reference that later practitioners had to distinguish. That includes the examiner-driven citation chains to it in later dental patents (e.g., US 6,244,866 and the inventor's own follow-on US 4,192,071, which lists "3924333 | Dental appliance | 1975-12-09 | Erickson" in its Patent References).

Verification note / confidence level: I could not have found a proceeding for this patent even if one existed but were captured in a paywalled docket (Docket Alarm, Lex Machina). My confidence that none exists is nonetheless high, for structural reasons independent of search completeness:

Strategic summary

Claim status. All 13 claims stand exactly as issued on 1975-12-09. Nothing is canceled, nothing is confirmed in an AIA trial, nothing has been narrowed by certificate. That means claims 1–13 are UNTESTED, including independent claims 1 and 7 and dependents 2–6 and 8–13. There is no FWD to point at, no claim-level verdict to quote, and — importantly — no statutory disclaimer or adverse judgment that would let a defendant say a claim is already gone. If you are being accused under this patent today, the PTAB record gives you nothing.

Estoppel landscape. § 315(e)(1) and § 315(e)(2) estoppel have never attached to anyone for this patent, because estoppel is triggered only by a final written decision under § 318(a), and none exists. Practically this is academic: the patent's term ended 1992-12-09, so under 35 U.S.C. § 286 any damages recovery is limited to six years before filing suit — a window that closed decades ago. There is no set of prior-art grounds a defendant needs to preserve, because there is no proceeding in which to preserve or lose them.

Pattern signals. No petitioner has ever filed; there is therefore no serial-petitioner pattern, no General Plastic issue, no Unified Patents-style defensive-aggregator challenge in the chain, and no PTAB→CAFC appeal path for this patent. The inventor, Norman Erickson, did pursue a family around this disclosure — US 4,192,071 (filed 1978-01-30, granted 1980-03-11), US 4,281,986 (granted 1981-08-04), and EP 0 026 992 A1 (published 1981-04-15) — all of which appear in the "Cited By" list, but those are separate patents with separate expiration dates and are outside the scope of this analysis. If a demand letter you received cites "the Erickson dental appliance patents" plural, verify patent numbers individually; a letter built on 3924333 is a letter built on a patent that has been dead since 1992-12-09.

The absence signal — read this correctly. The usual heuristic ("well-asserted patents eventually attract IPRs") does not apply here. The zero count is not evidence that the claims are strong; it is evidence that the claims are old and expired. A sophisticated counterparty should not argue "no IPR = valid patent." The correct inference is "no AIA trial was legally and economically possible during the patent's enforceability window."

Recommended next steps

1. If you have received a demand letter asserting US 3924333, the threshold response is not an invalidity position — it is a term/expiration position. Confirm the expiration date (the Google Patents record shows application 05/504435, filed 1974-09-09, granted 1975-12-09, with an anticipated expiration of 1992-12-09) and confirm there is no reissue, reexamination certificate, or statutory disclaimer in the file wrapper that could have altered claim scope. Pull the public file at USPTO Patent Center for application 05/504435 and check for any post-issuance papers.
2. Preserve the record that no PTAB activity exists. Snapshot the PTAB E2E / PTAB public information search results for patent 3,924,333, and the "no proceedings" result. If opposing counsel represents otherwise, the burden flips to them to produce a docket number.
3. Do not budget for an IPR. No institution decision deadline, oral hearing, or FWD due date exists to track — because no trial was ever instituted and none can be meaningfully filed against an expired 1974-priority patent. Spending IPR dollars here is misallocation; spend them on the expiration/laches/§ 286 analysis instead.
4. If your real exposure runs through the Erickson family rather than this patent (e.g., US 4,192,071 / US 4,281,986 / related continuation practice), note that those are different patents and require a separate PTAB-activity pull — this report covers only 3,924,333.

Sources consulted: the patent's own record at patents.google.com/patent/US3924333/en (claims 1–13, cited-by and citation lists, legal status "Expired – Lifetime," anticipated expiration 1992-12-09); USPTO PTAB public petition documents at ptacts.uspto.gov (3924333 appearing only as prior-art/IDS subject matter in third-party proceedings); and the structured "PTAB proceedings on file" block supplied in the prompt (zero AIA trials). No FWD, institution decision, or CAFC opinion citing this patent as the challenged patent was located.

I'll research the assignment record for US 3,924,333.

Ownership & Assignment Analysis — US 3,924,333 ("Dental appliance," Norman Erickson)

Methodological note before the findings: I could not query the USPTO Assignment Center search endpoint directly with the tools available to me (no authenticated/direct API access to assignmentcenter.uspto.gov; the web-search index returns only USPTO boilerplate pages and unrelated records, e.g. the Feb. 2, 2026 retirement of the older assignments.uspto.gov / assignment.uspto.gov URLs). The findings below therefore rest on (a) the face of the patent, (b) Google Patents' Legal Events / Current Assignee fields for US 3,924,333, and (c) the family record for the related Erickson filings. No reel/frame number appears anywhere in the record for this patent, and I will not invent one. Treat the "no assignments" call as a well-supported negative result, not a certified one.

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Inventors

Pattern observations:

• Sole inventor, no co-inventors across a ~25-year filing arc: US 2,937,445 (filed 1956, issued 1960), US 3,090,122 (filed 1961, issued 1963), GB 1,017,515 (1963), US 3,924,333 (1974), US 4,192,071 (filed 1978), US 4,281,986 (filed 1979), and EP 0 026 992 A1 (filed 1979). Each is individually owned.
• No "inventor departure" signal. The fire-sale tell you asked me to watch for (all inventors leaving the original assignee within 12 months of filing) is structurally inapplicable here — there was no assignee to leave. The observed pattern is the opposite: the same sole inventor kept filing improvements on the same appliance concept for two decades.
• The spec of US 4,281,986 (the inventor's own later filing) characterizes US 3,924,333 as "having merit" but "too complex," which is inventor's-own-admission prior art about the commercial practicality of this specific embodiment — but it is a technical criticism, not an ownership event.

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Original assignee

None. This patent issued to the inventor as an individual.

• The printed patent lists only [76] Inventor: Norman Erickson, Rte. 3, Box 551, Escondido, Calif. 92025 with no [73] Assignee field.
• Google Patents records Original Assignee: Individual and Current Assignee: Individual — i.e., the same status at grant and at the time of the record snapshot.
• Product / line of business: No corporate entity, so no "primary line of business" and no SEC-reportable operating company. The specification is expressly drafted around disposability ("materials and processes inexpensive enough to permit the finished product to be classed as disposable or consumable"), and the inventor continued to develop and file on the concept through 1979, which is circumstantial evidence of continued personal development but not evidence of a commercial product. I found no verifiable record that a product embodying claims 1 or 7 was ever sold by a named company.
• Current status: The patent is Expired – Lifetime, anticipated expiration 1992-12-09. Whether the inventor is living, and the disposition, if any, of his unrecorded personal rights, is not determinable from the sources available to me. Important legal point: because no assignment was ever recorded, any transfer of rights in this patent would have been unrecorded — meaning it would be ineffective against subsequent purchasers or mortgagees under 35 U.S.C. § 261, and invisible in the public record.

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Assignment timeline

The USPTO Assignment Center has no recorded assignment records for US 3,924,333. I am stating that plainly.

Every legal event associated with this patent in the public record is a prosecution or term event, not a conveyance:

• 1974-09-09 — Application US 504,435 filed (no assignment on file at filing; no [73] assignee)
• 1975-12-09 — Patent granted and published as US 3,924,333 A
• 1975-12-09 — Google Patents "Current Assignee: Individual"
• 1992-12-09 — Anticipated expiration (Expired – Lifetime)

There is no reel/frame to cite, no assignor, no assignee, no correspondent, and no conveyance type, because no document was ever recorded. Per the constraint you set, I am not fabricating entries to fill the section. Note for the chain-of-title file: the same is true of the sibling patents — US 4,192,071 and US 4,281,986 each list Assignee: Erickson, Norman (again the inventor personally, not a company).

Because the "no records" condition is met, the remaining sections are provided in condensed form strictly as a negative-signal audit rather than as an affirmative chain reconstruction.

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Timeline diagram

timeline
    title Ownership of US 3924333
    1974 : Filed by Norman Erickson as individual
    1975 : Patent issued with no assignee recorded
    1992 : Patent expired for lack of maintenance

The chain is a single node. There is no transfer, no corporate entity, and no termination at a defensive aggregator — the patent simply ran its term in the inventor's name.

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NPE / troll-pattern signals

Cross-reference note (per your instruction): The related-post-art set I surfaced includes the well-known modern intraoral-isolation assertion family (Solmetex / Dryshield / Incept line — US 8,911,232; US 9,788,924; US 11,576,764; US 11,589,969; US 11,589,970; US 11,744,686; US 11,826,217; US 12,011,329; US 12,090,418; US 12,167,948). Those patents cite US 3,924,333 as prior art; they do not claim priority to it and they are not in its chain of title. Do not conflate citation with succession — that is precisely the false-positive trap in this family.

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Verdict

Insufficient data — and I want to be precise about why that label is the correct one rather than a "no NPE" all-clear.

There is no recorded assignment chain to assess: the patent issued to Norman Erickson as an individual with no [73] assignee, Google Patents records Original and Current Assignee = Individual, and the only events on the record are the 1974-09-09 filing, 1975-12-09 grant, and 1992-12-09 expiration. Zero of the eight NPE signals is present, and none can be present, because signals 1 through 8 are all functions of a recorded transfer that never occurred. The practical finding for your diligence file is therefore: this patent was never part of any assertion program, was never securitized, and was never sold — it simply expired in the inventor's own name, which means any purported later transfer of rights in it would necessarily be unrecorded and, under 35 U.S.C. § 261, unenforceable against a subsequent purchaser.

Verification routes (please confirm before relying on this):

• Assignment Center: https://assignmentcenter.uspto.gov/ — search by patent number 3924333 (note: since Feb. 2, 2026 the legacy assignments.uspto.gov and assignment.uspto.gov URLs are retired and redirect here; a redirect or indexing failure is a plausible reason for the empty result I obtained, so a direct manual query is the single most important confirmation step).
• Google Patents legal events: https://patents.google.com/patent/US3924333/en
• USPTO Patent Center / PEDS for the prosecution record and any paper assignment never entered in the electronic system.

Explicit caveat: My conclusion is a negative search result obtained without direct access to the Assignment Center's search application. If a manual query returns a reel/frame for this patent, that record supersedes the analysis above — send it and I will rebuild the timeline and re-score the signals accordingly.

I'll verify each cited reference against live sources before analyzing anticipation.

Prior-Art Analysis — US 3,924,333 (Erickson, "Dental appliance")

Scope note. I searched the specific number 3924333 and no other. Every substantive hit resolved to the same document — US 3,924,333 A, appl. 504,435, filed 1974-09-09, issued 1975-12-09 — and I excluded same-numeric-string false positives already identified in the verification section (JP 3924333 B2, the two Florida EIN filings, the Kepler catalog entry). Bibliographic data in the prior summary is not repeated here. I also did not retrieve the prosecution file history (the Office actions themselves), so I cannot report what §102/§103 rejections were or were not made; the analysis below is on the issued claims against the references of record.

⚠️ Date inconsistency to flag: this task header states "Current Date: April 26, 2026," while the working environment and the fetched patent page date to 2026-09-26/28. Immaterial here (all relevant events closed in 1992), but noted per the no-auto-correction rule.

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1. The governing legal frame (why it matters here)

US 3,924,333 was filed 1974-09-09 — pre-AIA. The operative statute is therefore 35 U.S.C. §102 (pre-AIA), first-to-invent, where:

• §102(b) critical date = 1973-09-09 (one year before U.S. filing).
• A reference that issued before 1973-09-09 is a statutory bar regardless of who the inventor is — including the applicant's own earlier patents.
• Anticipation under §102 requires a single reference disclosing every claimed element, arranged as in the claim. Disclosure of fewer than all elements, or of elements that must be assembled from two documents, is a §103 question, not §102.

That framing produces the single most important conclusion of this memo: all three examiner-cited references, and both references the applicant himself discusses in the specification, issued before the §102(b) critical date. Their status as prior art is not contestable. Only their scope is.

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2. The references of record

Google Patents lists exactly three references under "Patent Citations (3)," all footnoted as cited by the examiner (asterisk): US 1,122,086 (Dunlop); US 2,672,143 (Gold); US 3,722,101 (Via). Source: https://patents.google.com/patent/US3924333/en

R4 and R5 are not in the examiner's citation list — they appear only in the applicant's Background of the Invention. That asymmetry (the examiner cited Via but not the applicant's own two structurally closer patents) is itself analytically significant and is developed in §5 below.

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3. Reference-by-reference

R1 — US 1,122,086 (Dunlop, "Combined mouth prop and illuminator"), filed 1914-09-22, issued 1914-12-22

Confidence flag — important. My searches for this specific number returned only third-party citation tables (it appears in the reference lists of US 7,153,131, US 7,611,354 and US 2015/0272693 as US1122086A * 1914-09-22 | 1914-12-22 | William F Dunlop | Combined mouth prop and illuminator), not the document's own text. The description below is therefore inferred from title and citation context, not read from the specification. Canonical location to verify: https://patents.google.com/patent/[US1122086A](/patent/US1122086A)/en

What it appears to disclose. A combination mouth prop (bite-block-type body held between the teeth to hold the mouth open) with an illuminator (self-contained light source for intraoral illumination).

Anticipation analysis. Nothing in the title or citation context suggests evacuation, suction, channels, a collector sheet, or frangibility.

Bottom line: R1 cannot anticipate any of claims 1–13. Its evidentiary value is as early proof that a bite prop is a notoriously old element — useful only to strip the bite-block limitation of any independent weight in a §103 combination.

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R2 — US 2,672,143 (Gold, "Spraying device"), filed 1952-12-05, issued 1954-03-16

Full text read (https://patents.google.com/patent/US2672143). The specification is quoted at length in the search results.

What it discloses. A flexible tube bent to form two loops, "placed in the human mouth and disposed partly on one and partly on the other side of a row of teeth," with longitudinally spaced perforations (8) in the confronting walls of the loops "whereby liquid supplied to the ends of the tube may be emitted in a series of sprays directed against the teeth." A clasp (5) of molded plastic frictionally retains the parallel tube portions and permits slidable adjustment of loop size "to fit the mouth of the particular patient." An external longitudinal rib (14) running in grooves in the clasp prevents twisting. Liquid is fed in from a faucet/coupling (18/19) via a mixing casing (18) — i.e., the tube is a supply line, not a suction line.

Anticipation analysis. R2 is a fluid-delivery device, not an evacuation device. That inversion matters:

• The perforations emit spray outward to the teeth; there is no lumen communicating to a vacuum source, so the "channels … communicating with an evacuator" language of claim 11 is not met.
• There is no bite block, no member bearing on lingual gingiva, no collector, no compartments.
• The clasp's adjustability is a size accommodation, not a left/right convertibility.

Bottom line: no claim is anticipated by R2. Its presence in the citation list is best explained as the examiner placing of record a tube carrying longitudinally spaced openings along the dental arch, on both sides of a row of teeth, with a clasp — i.e., background for "channels" and the two-sided aspect. Because the examiner's reasons are not in the record I retrieved, I label this an inference, not a finding.

Caveat: one Espacenet citation listing pairs "GOLD JOSEPH K" with "RICKLESS HAROLD D" (https://pl.espacenet.com/...). I could not confirm whether that reflects a co-inventor, assignee, or an Espacenet indexing artifact. Do not assert it either way.

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R3 — US 3,722,101 (Via, Jr., "Dentistry bite or prop block"), filed 1971-03-01, issued 1973-03-27

Full text read (PDF: https://patentimages.storage.googleapis.com/93/cb/a9/515c67a7c771ea/US3722101.pdf ; https://patents.google.com/patent/US3722101). 7 claims, 5 figures. Primary Examiner: Robert Peshock — the same examiner named on US 3,924,333.

What it discloses.

• "A disposable bite or prop block … made from a non-elastic foam plastic material into which the cusps on the bicuspid and molar teeth at one side of the mouth can indent to prop open the mouth."
• The block is "constructed to have different cross sectional dimensions" (polygonal with sides of different lengths, or arcuate variants) "so that the mouth can be retained opened to different degrees."
• "When the teeth indent into the foam plastic material, the block is locked in place against any slippage and is disposable after use."
• Material: non-toxic foamable plastic, "similar identity and properties to that of 'Dylite' … polyurethane, foamed polyethylene, foamed epoxy and the like," preferably white to reflect light.
• Critically: the suction is external — "the use of a continuous high-flow suction tube. The tube is used by an assistant to free the mouth of the collecting saliva, debris and wash spray."

Anticipation analysis — this is the closest of the three cited references, but only element-by-element.

Doctrinal caveat that favors the patentee: Via's material deforms by crushing/indenting a foam — the cell walls collapse locally. The '333 specification claims a distinct mechanism: the polystyrene "compress[es] the cells in the immediate vicinity of the pressure to, in effect, render the material denser in that immediate vicinity. Consequently, continued or additional deformation is resisted inasmuch as the denser material is more rigid." Whether foam-crush and cell-densification are the same thing is a factual dispute (expert-testimony territory). Via also teaches away from integration, expressly relegating suction to an assistant-held tube — a strong non-obviousness point for the integrated evacuating-member-plus-collector architecture of claims 1 and 9.

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4. The references the applicant put on the record himself (R4, R5) — the actually dangerous art

These are not in the examiner's citation list, yet they are (a) §102(b) statutory bars, (b) the same inventor's own work, and (c) on the face of it structurally closer to claims 1 and 9 than anything the examiner cited.

R4 — US 2,937,445 (Erickson, "Dental appliance"), S.N. 616,987, filed 1956-10-19, issued 1960-05-24, 16 claims

Full text: https://patentimages.storage.googleapis.com/2f/9b/52/39edd13b58a4d4/US2937445.pdf ; https://patents.google.com/patent/[US2937445A](/patent/US2937445A)/en

Disclosure, quoted where it bears on the claims:

• Member 1 "with portion 3 overlying the roof of the mouth … and the peripheral edge thereof in sealing engagement with the hard palate 8 inside the upper teeth 9. The lingual portion 4 is adapted to overlie the tongue 10 and have its peripheral edge in sealing engagement with the floor 11 of the mouth."
• "Buccal portions 5, 6 are adapted to extend between the distal surface of the last molars and the anterior border of the ascending ramus 13 of the mandible … portions 5, 6 are formed to a narrow neck, as at 14, where they pass through this space … and are provided with longitudinally extending ears 15, 16 projecting oppositely behind said last molars in the vestibule of the mouth."
• "All of the peripheral edges … are adapted to seal in sealing engagement with relatively insensitive tissues."
• A thickened portion 18 with bore 19 and apertures 20 draining the pocket, plus a drain pipe 22 "attached to a suitable aspirating device."
• The Figure 6–8 embodiment (member 41) is for the lower mouth: buccal pocket 42, lingual pocket 43, connecting portion 44 extending behind the last lower molar, forward of the ramus.

Anticipation analysis. R4 reads remarkably well onto the collector limitation of claim 1 and claim 9 — the palatal/lingual/buccal sheet, the passage through the retromolar space into the vestibule, the rest on tissue over the ascending ramus, the peripheral sealing engagement with soft tissue, and the channeling of fluid to an evacuating bore.

R5 — US 3,090,122 (Erickson, "Dental appliance"), filed 1961-01-18, issued 1963-05-21

Full text: https://patentimages.storage.googleapis.com/18/a0/e6/89a2c0a0e7e5a7/US3090122.pdf ; https://patents.google.com/patent/US3090122

Disclosure: a soft, flexible waterproof receptacle 10 supported at the end of a drain tube 11, with a bite block 12 mounted on the tube; "An aperture through block 12 firmly receives tube 11 therein"; the receptacle is "symmetrical about the axis of tube 11 and it may therefore be placed in either side of the mouth"; palatal portion 17 over the hard palate, lingual portion 18 over the tongue/floor 23, and buccal portion 27 extending "between the distal surface of the last molars and the anterior border of ascending ramus 28," with a narrow neck 30 and ears 31, 32 projecting behind the last molars in the vestibule; openings 41 in the depressed portion 14 and lateral apertures 42 adjacent channel 47 between the tongue and periodontium, both draining to tube 11 under aspiration.

Anticipation analysis — this is where the claim-4 limitation nearly falls.

Key takeaway on R4/R5: these two are the reason the §102(b) exposure of US 3,924,333 is real at the element level and near-zero at the claim level. Every independent claim requires the semi-rigid, bite-impression-deformable bite block (a Via/Erickson-'333 feature absent from both '445 and '122), and claim 7/8 additionally require the frangible pair of evacuating members. Those two features are the load-bearing novelty of the patent, and neither is disclosed by any reference located.

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5. Anticipation matrix — every claim, every reference

Legend: — no disclosure of the claim's distinguishing element · ~ element-level disclosure only · ✗ cannot anticipate as a whole (misses at least one element)

No claim of US 3,924,333 is anticipated by any single reference of record, or by either self-disclosed Erickson patent. The three examiner-cited references collectively reach only the bite-block element (Via), a tube-with-spaced-openings element (Gold), and a mouth-prop element (Dunlop). The two references the applicant disclosed reach the collector geometry and the arch-engagement geometry. Nothing reaches the frangible left/right pair, the adhesive-coated removable collector, or the "adhesive back face forms a longitudinal closure for said channels" feature.

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6. Closest prior art — ranked, with the reason each falls short

1. US 2,937,445 (Erickson, 1960) — closest overall. Discloses the palatal/lingual/buccal sheet, the retromolar passage into the vestibule, the rest on tissue over the ascending ramus, soft-tissue sealing, and a collection pocket drained to an aspirator. Falls short on: no bite block at all; unitary rather than removably-connected collector; no forward/rear compartment division; no scoreline.
2. US 3,722,101 (Via, 1973) — closest on the bite block. Discloses a molded disposable block locked in place by tooth-cusp indentation, gripped on one side of the mouth. Falls short on: everything relating to evacuation, any evacuating member, any collector, and any left/right pair; and it expressly assigns suction to an assistant's separate tube.
3. US 3,090,122 (Erickson, 1963) — closest on the evacuating conduit in a bite block and on either-side usability (via symmetry, not convertibility). Falls short on: removability of the evacuating member, the pair, the scoreline, the adhesive collector.
4. US 2,672,143 (Gold, 1954) — tube with longitudinally spaced openings looped around both sides of a dental arch, size-adjustable. Falls short on: it supplies rather than evacuates; no block, no collector.
5. US 1,122,086 (Dunlop, 1914) — mouth prop + illuminator. Background only.

Why the claims plausibly survived. The issued claims are anchored on (i) a bite block whose material mechanics (initial deformation → local densification → resistance to further deformation) produce automatic, ligature-free fixation, and (ii) a chairside-convertible left/right architecture in which one of a frangible pair of evacuating members is snapped off and a flexible, adhesively attached, gather-able collector is fitted to it — with the adhesive bond simultaneously capping the evacuation channels (claim 12). Point (i) is only partially met by Via and point (ii) is met by nothing.

⚠️ Drafting defect worth flagging (affects claim 12's exposure): claim 12 depends from claim 7 but recites "said collector," a term introduced only in claim 9, from which claim 12 does not depend. Under the broadest reasonable interpretation one might read in claim 9's collector; a stricter reading (e.g., Phillips-style construction in litigation) leaves "said collector" without antecedent basis. Either way, no reference located discloses an adhesive-coated collector forming "a longitudinal closure for said channels," so the defect does not presently create anticipation exposure — but it does make claim 12 harder to rely on for validity purposes. The same "said collector" antecedent issue appears in the '333 specification's internal claim summary, confirming it is in the original text rather than a transcription error.

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7. Art I did not find cited, but that a challenger would likely pull

• US 4,192,071 (Erickson, 1980-03-11) and US 4,281,986 (Erickson, 1981-08-04), plus EP 0 026 992 A1 (priority 1979-09-14) — these all list US 3,924,333's inventor/applicant and are later-filed, so they are not prior art to US 3,924,333. Their utility is contextual: the '986 specification characterizes the '333 appliance as "having merit" but "too complex," and criticizes saliva-pump appliances generally — a documented, self-authored admission usable in an obviousness (not anticipation) narrative about the family and about the state of the art as of 1979, not 1974.
• A lead requiring verification: US Patent 3,802,081 ("Rogers") surfaced in a PTAB exhibit (IPR2025-01059, Ascentcare Dental Products v. Solmetex) quoting a "pivoted … plate-like generally oval tongue protector member 17" assembled with "a flexible perforated tubular member 23" to act as "a saliva ejector" — i.e., tongue guard + integrated suction. Source: https://gaeflexstaging-dot-docketupdate.appspot.com/cases/PTAB/IPR2025-01059/... I could not verify its filing/issue dates in this session and must not assert them; if it issued on or before 1973-09-09 it would be a §102(b) bar and is, on its face, closer to claims 1/9/11 than anything the examiner cited. Treat strictly as a lead to confirm against the USPTO database before relying on it.
• The 44–71 documents listed under "Cited By" on the Google Patents page (e.g., US 4,167,814; US 4,975,057; US 5,232,362; Solmetex/Dryshield patents) are all later than 1974 and cannot be prior art to '333. They are useful only as evidence of the commercial trajectory of the isolated-field appliance art, not as references.

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8. Confidence statement

I'll ground this obviousness analysis in the actual prior-art references cited on the face of US 3,924,333 and in its specification.

Obviousness Analysis — U.S. Patent 3,924,333 (Erickson), under 35 U.S.C. § 103

Scope note. This analysis uses the prior art identified on the face of US 3,924,333 and in its specification (the "Prior Art section" of the record provided): US 1,122,086 (Dunlop), US 2,672,143 (Gold), US 3,722,101 (Via), and the two references the specification itself discusses — US 2,937,445 (Erickson, 1960) and US 3,090,122 (Erickson, 1963). I supplemented the record with the published text of Via, Gold, and the two Erickson patents via Google Patents/FreePatentsOnline. I did not retrieve the '333 file wrapper (no Office actions or reasons for allowance were found), so I cannot state what the examiner actually relied on beyond the citation list.

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1. Bottom line up front

Net assessment: Claims 1–6, 9–11, and 13 are, in my view, more likely than not invalid under § 103 on the record art. Claims 7 and 8 (the paired left/right guards joined by a frangible scoreline) and 12 are the most defensible, and I would not expect the art of record to carry them without additional secondary references or a common-knowledge/design-choice showing.

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2. Governing law and framing assumptions

1. Pre-AIA § 103 applies. The application was filed 1974-09-09 and issued 1975-12-09 (https://patents.google.com/patent/US3924333/en). The validity inquiry is the first paragraph of § 103 as enacted in 1952, assessed under the Graham v. John Deere framework (scope/content of prior art, differences, level of ordinary skill, secondary considerations).
2. *A post-2007 challenge would be decided under KSR.* KSR Int'l v. Teleflex was decided 2007-04-30 and applies to any case decided after that date regardless of filing date. That matters here: the "design choice / predictable variation / known work-around" rationales that carry claims 7–8 and 12 are far more available today than they were under the CCPA's 1975-era teaching-suggestion-motivation practice. I flag where the two standards diverge.
3. The two Erickson patents are § 102(b) statutory-bar art. US 2,937,445 (filed 1956-10-19, issued 1960-05-24) and US 3,090,122 (filed 1961-01-18, issued 1963-05-21) were both printed more than one year before the 1974-09-09 filing date. The "by others" qualifier in § 102(a) does not appear in § 102(b), so the fact that the inventive entity is the same (Norman R. Erickson / Norman R. Erickson) does not exempt them. There is no pre-1984 "commonly owned" exception to § 103 — § 103(c) was not enacted until 1984. (Caveat: this is a legal nuance I state with high but not absolute confidence; confirm against current authority on use of an inventor's own § 102(b) prior patents in a § 103 combination before filing a brief on it.)
4. Crucially, neither '445 nor '122 appears in the "Patent Citations (3)" list on the '333 record — only Dunlop, Gold, and Via do. That strongly suggests the examiner never applied the inventor's own two closest prior patents, which is the central "reference not before the examiner" narrative for this patent.
5. Dunlop's full text was not retrieved; I know it only from the '333 citation list (title/date/inventor) and from its appearance in third-party citation tables. Treat any Dunlop-specific assertion below as tier-2 evidence.

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3. Person having ordinary skill in the art (PHOSITA)

A designer of dental appliances holding (a) a bachelor's degree in mechanical engineering or industrial design, or a D.D.S., plus (b) 2–3 years of experience designing or specifying intraoral mouth props, saliva ejectors, and rubber-dam/field-isolation hardware, and (c) working familiarity with disposable thermoformed and foam-molded plastic dental disposables. This is a low-to-moderate skill level in a mature mechanical arts field — a fact that cuts against the patentee, because the asserted advance is a rearrangement of known mechanical parts rather than an unpredictable technology.

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4. What each reference discloses (grounded)

US 2,937,445 — Erickson, "Dental appliance" (1960) — https://patents.google.com/patent/US2937445 · https://www.freepatentsonline.com/[2937445](/patent/2937445).html

The single most damaging reference. Its claims recite a "soft, flexible, waterproof member of relatively thin cross section adapted to fit within the mouth and providing a depressed central pocket portion adapted to extend across the oral cavity forward of the oral pharynx, with longitudinally oppositely projecting palatal and lingual portions respectively adapted to fit in sealing engagement with the roof and floor of the mouth adjacent the teeth, and with transversely oppositely projecting buccal portions adapted to extend between the distal surface of the last molars and the anterior border of the ascending ramus of the mandible." Claim 6 adds "longitudinally extending ears… adapted to fit in sealing engagement with the soft tissues in the vestibule of the mouth behind the parotid duct openings." Claim 9 adds a "thickened portion… providing an elongated bore therethrough, apertures… communicating between said pocket portion and said bore, and an elongated, hollow, rigid drain pipe received in said bore."

The specification adds: the member "shields the highly sensitive areas of the oral cavity and oral pharynx from any foreign matter"; it "allows a patient to be positioned with his head generally horizontal"; it "help[s] hold the tongue out of the way"; and "a conventional saliva ejector may be positioned to withdraw the liquid."

Read on the '333 claim chart: '445 expressly discloses the collector's claimed anatomical path (retromolar/ascending ramus, vestibule, palate), the compartmentalizing and debris-blocking function, the conforming/sealing engagement, and the integral evacuation manifold (bore + apertures + rigid pipe).

US 3,090,122 — Erickson, "Dental appliance" (1963) — https://patents.google.com/patent/US3090122

A "flexible, waterproof receptacle adapted to fit within the side of the mouth and having a central depressed portion on the upper side thereof for receiving liquid and debris from above," with drain means and "apertures at the underside of said receptacle communicating with said drain means for draining liquid from the mouth beneath said receptacle." Its third independent claim recites that the "receptacle [is] substantially symmetrical about an axis for fitting either side of the mouth." Its fourth independent claim recites a soft receptacle with "oppositely extending palatal and lingual portions… adapted to fit in sealing engagement with portions of the roof and floor of the mouth," and a buccal portion "adapted to extend between the distal surfaces of the [molars]." The description adds a rigid support member (tube 11) received through a block 12, and apertures 42 draining the channel 47 formed between the tongue and the periodontium.

Read on the claim chart: '122 supplies (i) dual-level evacuation — above the receptacle via openings 41 and below/side via apertures 42, which maps onto '333's separate "forward compartment" and "back/side" evacuation paths; (ii) the circumferential sealing limitation of claim 2 ("substantially sealing engagement with the soft tissues of the mouth"); (iii) a rigid evacuating conduit seated in a block (claim 4); and (iv) a one-piece reversible design for either side of the mouth — directly relevant to claim 7, and, as I discuss below, potentially a teaching away from claims 7–8.

US 3,722,101 — Via, "Dentistry bite or prop block" (1973) — https://patents.google.com/patent/US3722101 · PDF: https://patentimages.storage.googleapis.com/93/cb/a9/515c67a7c771ea/US3722101.pdf

"A disposable bite or prop block… made from a non-elastic foam plastic material into which the cusps on the bicuspid and molar teeth at one side of the mouth can indent to prop open the mouth and provide a fixed cavity… When the teeth indent into the foam plastic material, the block is locked in place against any slippage and is disposable after use." It also acknowledges the very problem '333 addresses: "as the high flow suction devices are used in what is called 'four-handed dentistry'…" The block "has a thickness of approximately the width of a molar tooth and… different cross sectional dimensions so that the mouth can be retained opened to different degrees."

Read on the claim chart: Via reads almost verbatim on claim 1's bite-block limitation and on claim 10, and it supplies the disposability motivation. Critically, claim 1 does not recite polystyrene or any material — it recites the functional behavior "deforming upon the initial bite… so as to form a mold… and which bite block resists further deformation." Via's non-elastic foam that retains its shape after cusp indentation does exactly that. The patentee's only lifeline on this element is the assertion that the specific cell-densification behavior of polystyrene is a critical and unexpected mechanism — but the claim isn't limited to it, and the specification's mechanism description is not in the claims.

Corroborating third-party characterizations of Via (useful for demonstrating the art's common understanding, though post-dating '333): US 6,241,521 describes Via as "disposable, polygonal-shaped bite block made from a non-elastic foam material whereby the force of the teeth on the block causes the teeth to indent into the material and lock the block in place" — https://www.freepatentsonline.com/[6241521](/patent/6241521).html

US 2,672,143 — Gold, "Spraying device" (1954) — https://patents.google.com/patent/US2672143

A flexible tube "bent to form two loops, which may be placed in the human mouth and disposed partly on one and partly on the other side of a row of teeth and which has longitudinally-spaced perforations for directing sprays of liquid," plus a molded-plastic clasp and an anti-twist longitudinal rib. Gold is a sprayer, not an evacuator, so it is not a § 102 anticipation of the channels. It is, however, competent § 103 art for the proposition that a perforated/slotted flexible tube seated against a dental arch and communicating with the exterior of the mouth was a known intraoral fluid-handling structure — useful as a secondary reference for claims 4 and 11, and for defeating any argument that putting a plenum/channel array in an intraoral molded body was inventive.

US 1,122,086 — Dunlop, "Combined mouth prop and illuminator" (1914) — cited on the face of '333; full text not retrieved. Tier-2 evidence for the generic "mouth prop" element only.

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5. Element-by-element mapping (independent claims)

The mapping is close enough that the only material gap in claim 1 is the word "removably." That is a substitution-of-parts argument, not a structural advance — see Ground I.

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6. Grounds of rejection

Ground I — '445 in view of Via (and Dunlop); further in view of '122

Against claims 1, 2, 3, 4, 5, 6, 9, 11, 12, 13.

Why combinable. Both are analogous art in the same field (A61C), address the identical problem (keeping coolant spray, saliva, and debris out of the working field and the pharynx during high-speed restorative dentistry), and are structurally compatible: '445 is a sealing, pocket-forming, fluid-evacuating dam that lacks any bite prop; Via is a bite prop that lacks any isolation or evacuation capability. A skilled artisan seeking to keep a patient's mouth open and the field dry would look precisely to these two references, and each supplies what the other lacks. The combination requires no change in the function of either part — the classic "combination of known elements, each performing its own function" case.

'333's own specification supplies the motivation in its own words. The Background states the art's goal: "maintaining the patient's mouth in a fixed open position and at the same time collecting and removing the coolants and natural fluids." An applicant's own recitation of the problem is an admission of the state of the art and of the articulated need. This is an admission-based motivation independent of any reference.

The "removably connected" limitation. The '445 member is integral; '333's collector is an adhesively-applied, replaceable element. The motivation to make it removable comes from the same reference and from the specification's own stated purpose: patient-to-patient sizing and disposability. '333 itself says collectors "may be provided in a variety of sizes and shapes to permit choice of the one that most effectively conforms to the profile and contour of the patient's mouth." That is a recognition of a design need that a modular one-piece/shielded appliance would satisfy, and it justifies the substitution of a replaceable adhesively-backed shield for '445's integral shield without any change in function. Practical effect: the collector element of claim 1 becomes a change in a known structure (integral → attached) with no new result.

Ground II — '122 in view of Via

Against claims 1, 2, 4, 11 (and as a secondary reference everywhere).

'122 already discloses the substitute mechanism for claim 4 ("evacuating conduit received in said bite block and in fluid communication with said channels") — tube 11 passing through block 12 into the mouth. And '122's dual-level evacuation (openings 41 above; apertures 42 below draining channel 47) is the closest thing in the record to '333's recitation of channels servicing both a forward compartment and a back/side region. Combine that with Via's prop block gripped on one side and the resulting appliance reads on claim 1 except for the specifically recited retromolar/palatal path, which '445 supplies.

Ground III — '445 + '122 + Via (+ Dunlop), potentially with common-knowledge evidence

Against claims 7, 8, 10 — the disposability/single-SKU architecture.

• Claim 10 is straightforwardly obvious over Via alone (functionally identical bite block behavior) and over Via in view of Dunlop.
• Claim 7 (a "combination left and right side appliance" with a pair of evacuating members, one removable for the side to be worked) has no express counterpart in the record references. The bridge is: (i) '122's express teaching that the appliance may be made "substantially symmetrical about an axis for fitting either side of the mouth" — i.e., the art had already recognized the left/right problem and solved it by reversibility; and (ii) the documented commercial/design incentive (single molded disposable; one SKU; no left hands vs. right hands inventory). Under KSR, "a structure… that has been made to work for one side, and the desirability of using it on the other side" supports "predictable variation" and "known work-around" rationales. Under strict 1975-era TSM practice, the rejection is weaker, because '122's solution (symmetry) is a different solution from the claimed one (two guards, break one off).
• Claim 8 (frangible scoreline) is the single most exposed-to-failure and simultaneously most-defensible claim. The record references do not teach a frangible connection between two evacuating members and a bite block. A rejection here would rest on common-knowledge evidence that snap-off/frangible joints in molded medical and dental disposables were conventional by 1974 (e.g., frangible ampoules, break-off tabs, snap-apart packaging) plus the rationale that the number of parts and the manner of separation is an obvious design choice given both sides must be moldable from a single tool. This is a factual predicate I have not verified on this record, and I would not assert it without a supporting secondary reference or declaration evidence.

Ground IV — Gold as secondary art

Against claims 4 and 11 (and claim 7's tube-connected assemblies). Gold is only useful as cumulative evidence that intraoral perforated/slotted flexible tubes communicating with the mouth exterior were known. Do not build a primary rejection on Gold; it is a fluid delivery device and the art would have to be flipped end-for-end into a suction manifold, which invites an "improper hindsight / change in principle of operation" attack.

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7. Enumerated motivations to combine (for the rejection's rationale section)

1. Same field of endeavor and same problem — all references are dental mouth-opening/fluid-management art (Via is classified A61C 3/00; '333 is A61C 17/06, 17/08; '445's and '122's own classification lists include A61C 5/14 and A61C 17/08).
2. Complementary, not overlapping, disclosures — '445/'122 give isolation + evacuation but no occlusion prop; Via/Dunlop give an occlusion prop but no isolation or evacuation. Neither reference "teaches away" from the other's contribution.
3. Explicit articulated need in the prior art — '445 states the goal of shielding the oral pharynx and permitting the head-horizontal (supine) posture; Via expressly frames the invention against "high flow suction devices… 'four-handed dentistry'"; '333's own Background repeats the same need. There is a documented, unsatisfied need for a single article that props, isolates, and evacuates.
4. Predictable, non-critical combination — the parts retain their respective functions; no parameter is asserted as critical in the claims; no comparative data of record.
5. Design incentives toward the specific claimed architecture — disposability (Via); eliminating retainers/ligatures and readjustment (expressly stated in '333 as an advantage and implicitly sought throughout the art); sizing and modularity of the collector (expressly stated in '333's own specification); reduced part count and single-SKU left/right utility (commercial common sense).
6. Reasonable expectation of success — molded polystyrene/foam/flexible-sheet dental disposables were a mature, predictable technology by 1974.

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8. Anticipated rebuttals and how they fare

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9. Cross-reference to the prior sections (and one flag)

• Consistent with the earlier summary, the record art applied on the face of the patent was only Dunlop, Gold, Via — all prop/spray art. None of them discloses the collector geometry, the tongue-guard channel manifold, or the compartmentalization. That fully explains why claim 1 was allowed in 1975. The invalidity thesis therefore does not depend on re-reading the examiner's three references; it depends on two references the examiner appears not to have applied: Erickson's own US 2,937,445 and US 3,090,122.
• Contradiction flag / verification needed: the earlier-generated sections state that US 4,281,986 characterizes US 3,924,333 as having "merit" but being "too complex." I did not verify that quotation in this pass. If accurate, it is an inventor admission about the patented appliance's complexity and is useful context for a "the prior art already solved this more simply" narrative — but I would not put it in a brief without pulling the '986 text and confirming the exact language and page.
• Claim-drafting observations relevant to claim construction: (a) claim 1's recitation of channels "in said bite block… for the removal of fluid generated in the back compartment" is not clearly described in the '333 specification, which mentions only the "interior terminus 41 of the bore 26… effective to evacuate fluid forming in the side of the mouth." Expect either a narrow reading or a § 112 indefiniteness challenge on that limitation. (b) Claims 12 and 13 depend from claim 7 but refer to "said collector," which has antecedent basis only in claim 9 — expect a § 112 ¶ 2 argument, and expect the patentee to read them as incorporating claim 9. (c) Claim 3 ("unitary with said bite block") is in tension with claim 7's "removable" members; the patentee's own treatment of a frangible scoreline as still being "unitary" (claim 3 filed alongside claim 8) means "unitary" must be read broadly — which broadens claim 3 toward the one-piece molded body of '445/'122 and makes it easier to invalidate.

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10. Caveats, confidence, and what to verify before relying on this

1. I did not obtain the '333 file wrapper. The actual grounds of allowance are unknown. The whole analysis assumes the examiner did not have '445 and '122 before him — supported by the citation list, but not confirmed.
2. All quotations from '445 and '122 are drawn from the Google Patents full-text as surfaced in web search results, not from a line-by-line reading of the PDFs. Before using any quote in a validity contention, pull US 2,937,445 and US 3,090,122 from patentimages/FreePatentsOnline and verify column and line cites.
3. Dunlop's text was not retrieved; assertions about its scope are limited to its title and citation appearances.
4. Claim 8 (frangible scoreline) is not carried by the record art alone. It requires either (a) a secondary reference disclosing a break-off/frangible dental or dental-disposable structure, or (b) a declaration establishing that frangible separation of molded dental disposables was routine by 1974. Without one of those, claim 8 survives on the art actually cited in this record, and claim 7 is close to surviving with it.
5. Legal-standard sensitivity is material. These claims are much stronger against a 1975-era TSM analysis than under KSR's flexible standard. If you are testing a hypothetical post-KSR challenge, claims 7–8 fall more readily; if you are reconstructing the 1975 prosecution, they hold.
6. I could not run a definitive pre-1993 litigation search. Consistent with the prior sections, no litigation, PTAB proceeding, or CAFC appeal involving US 3,924,333 was found, so these conclusions rest on the intrinsic record and the art, not on any adjudicated validity finding.
7. This is a technical invalidity analysis, not legal advice, and no assertion here reflects a legal conclusion of invalidity.