Exhibit 10.4

ALIGN TECHNOLOGY, INC.

SIXTH AMENDMENT
TO CREDIT AGREEMENT

This SIXTH AMENDMENT TO CREDIT AGREEMENT (this "Amendment") is dated as of July
24, 2017 and entered into by and among Align Technology, Inc., a Delaware
corporation ("Borrower") and Wells Fargo Bank, National Association ("Bank").

RECITALS

WHEREAS, Borrower is currently indebted to Bank pursuant to the terms and
conditions of that certain Credit Agreement dated as of March 22, 2013 (as
amended, the "Credit Agreement"), by and between Borrower and Bank. Capitalized
terms used herein without definition shall have the same meanings herein as set
forth in the Credit Agreement.

WHEREAS, Bank has delivered to Borrower (i) that certain consent letter dated as
of July 18, 2016 (the “First Consent”) consenting to a loan to SMILEDIRECTCLUB,
LLC (“SDC”) in an amount not to exceed $15,000,000 (the “SDC Loan”) and an
equity investment in SDC in an amount not to exceed $50,000,000 (the “SDC Equity
Investment”, (ii) that certain consent letter dated as of July 25, 2016 (the
“Second Consent”) consenting to the SDC Loan, the SDC Equity Investment, and the
Supply Agreement (as defined in the Second Consent), (iii) that certain consent
letter dated as of December 13, 2016 (the “Third Consent”) consenting to the
Borrower’s making of up to $90,000,000 of Capital Expenditures in the fiscal
year ended December 31, 2016, and (iv) that certain consent letter dated as of
January 31, 2017 (the “Fourth Consent”, and together with the First Consent, the
Second Consent, and the Third Consent, the “Consents”) consenting to an increase
of the maximum amount permitted to be outstanding under the SDC Loan from
$15,000,000 to $30,000,000.

WHEREAS, Borrower has requested that Bank consent to an increase of the SDC
Investment from a maximum amount of $50,000,000 to a maximum amount not to
exceed $60,000,000.

WHEREAS, Bank and Borrower have agreed to certain changes in the terms and
conditions set forth in the Credit Agreement and have agreed to amend the Credit
Agreement to reflect said changes as set forth below.

NOW, THEREFORE, for valuable consideration, the receipt and sufficiency of which
are hereby acknowledged, the parties hereto agree that the Credit Agreement
shall be amended as follows:

Section 1.    AMENDMENTS TO THE CREDIT AGREEMENT

A.The Section entitled “NEGATIVE COVENANTS: CAPITAL EXPENDITURES” is hereby
amended by deleting it in its entirety and substituting the following therefor:

Doc: 12449293    Version: 4

--------------------------------------------------------------------------------

“CAPITAL EXPENDITURES. Make any additional investment in fixed assets ("Capital
Expenditures") In excess of an aggregate of (i) for the fiscal year ended
December 31, 2016, $90,000,000, (ii) for the fiscal year ending December 31,
2017, $225,000,000.00 and (iii) for the fiscal year ending December 31, 2018 and
each fiscal year thereafter, $70,000,000.00 during any fiscal year; provided,
that the foregoing shall not apply to (x) expenditures of insurance proceeds to
rebuild or replace any asset after a casualty loss or (y) leasehold improvement
expenditures for which Borrower or a Subsidiary is reimbursed promptly by the
related lessor. Notwithstanding the foregoing, the maximum amount of Capital
Expenditures permitted by this Section in any fiscal year shall be increased by
the amount of Capital Expenditures that were permitted to be made under this
Section in the immediately preceding Fiscal Year (without giving effect to any
carryover amount from prior fiscal years) over the amount of Capital
Expenditures actually made during such preceding fiscal year In an amount not to
exceed $10,000,000.00; provided that Capital Expenditures in such fiscal year
shall be counted last against any amount so carried forward.”

B.The Section entitled “NEGATIVE COVENANTS: GUARANTIES” is hereby amended by
deleting it in its entirety and substituting the following therefor:

“GUARANTIES. Guarantee or become liable in any way as surety, endorser (other
than as endorser of negotiable instruments for deposit or collection in the
ordinary course of business), accommodation endorser or otherwise for, nor
pledge or hypothecate any assets of Borrower or its Subsidiaries as security
for, any liabilities or obligations of any other person or entity, except (i)
any of the foregoing in favor of Bank, (ii) if the underlying obligations
constitute Indebtedness permitted to be incurred pursuant to clauses (a), (b),
(c), (d), (j) and (m) of the section entitled “Negative Covenants – Other
Indebtedness” above or payables arising in the ordinary course of business,
(iii) if any such pledge or hypothecation constitutes a Permitted Lien, (iv) if
such transaction is permitted pursuant to the Section entitled “Loans, Advances,
Investments” below, (v) a guaranty of the obligations of ALIGN TECHNOLOGY DE
COSTA RICA, S.R.L (“Align CR”) a lease agreement to be entered into on or about
July 24, 2017, together with a tenant improvement agreement, a construction
management agreement, and other ancillary documents related thereto (each a “CR
Agreement”, and collectively, the “CR Agreements”), each between ZONA FRANCA LA
LIMA, S. R. L. and ALIGN CR, provided, however, that (A) the final terms and
conditions of each of the CR Agreements must have been approved by Bank in
writing prior to execution and effectiveness thereof in order for the guaranty
thereof to be permitted hereunder, and (B) any amendment or modification of any
kind to any of the CR Agreements that is materially adverse to the interests of
either Borrower or Bank (for the avoidance of doubt, an increase in the guaranty
obligations of Borrower in excess of $10,000,000.00 shall be deemed materially
adverse to Bank) must have been approved by Bank in writing prior to execution
and effectiveness thereof in order for the guaranty thereof to be permitted
hereunder, and (vi) indemnification obligations arising in the ordinary course
of business or in connection with any transaction permitted by this Agreement,
in each case to which such guarantor is a primary party.”

C.The Section entitled “NEGATIVE COVENANTS: LOANS, ADVANCES, INVESTMENTS” is
hereby amended by deleting clause c) thereof in its entirety and substituting
the following therefor:

- 2 -

--------------------------------------------------------------------------------

“c) (i) other Investments, provided that (x) no Event of Default or Potential
Event of Default shall have occurred and be continuing or would be caused by the
incurrence of such Investment, and (y) the aggregate amount of such Investment
made after the Closing Date shall not at any time exceed $10,000,000 in the
aggregate, and (ii) investments consisting of (1) loans to SMILEDIRECTCLUB, LLC
(“SDC”) in an amount not to exceed $30,000,000 at any time outstanding (the “SDC
Loan”), (2) equity investments in SDC in an aggregate amount not to exceed
$50,000,000 made prior to December 31, 2016 (the “2016 SDC Equity Investment”),
and (3) equity investments in SDC in an aggregate amount not to exceed
$13,000,000 made after December 31, 2016, but prior to August 1, 2017 (the “2017
SDC Equity Investment”, and together with the 2016 SDC Equity Investment, the
“SDC Equity Investments”);”.

D.The Section entitled “NEGATIVE COVENANTS: TRANSACTIONS WITH AFFILIATES” is
hereby amended by deleting it in its entirety and substituting the following
therefor:

“TRANSACTIONS WITH AFFILIATES. Directly or indirectly enter into any
transaction, including, without limitation, any purchase, sale, lease or
exchange of property, the rendering of any service or the payment of any
management, advisory or similar fees, with (a) any officer, director, holder of
any capital stock in, or other affiliate of Borrower or any of its Subsidiaries
or (b) any Subsidiary of Borrower that is not a Loan Party, other than (i)
payments to Subsidiaries of Borrower for royalty agreements and manufacturing
agreements in the ordinary course of business and consistent with past
practices, (ii) reasonable and customary fees paid to members of the board of
directors (or similar governing body) of Borrower or any of its Subsidiaries,
(iii) compensation arrangements and benefit plans for officers and other
employees of Borrower and its Subsidiaries entered into or maintained or
established in the ordinary course of business, (iv) transactions between or
among Loan Parties otherwise permitted hereunder, (v) transfers of fixed assets
at book value or inventory at cost from a Loan Party to any Subsidiary of
Borrower that is not a Loan Party, (vi) transactions between or among any
Subsidiary of Borrower that is not a Loan Party and any other Subsidiary of
Borrower that is not a Loan Party, (vii) the SDC Loan, the SDC Equity
Investments, and transactions pursuant to that certain Strategic Supply
Agreement, dated as of July 26, 2016, by and between SDC and Borrower, as
amended from time to time in a manner not materially adverse to the interests of
either Borrower or Bank, (viii) the guaranty permitted under subsection (v) of
NEGATIVE COVENANTS: GUARANTIES, and (ix) other transactions in the ordinary
course of business on terms as favorable as would be obtained by it on a
comparable arm’s length transaction with an independent, unrelated third.”

Section 2.    CONDITIONS TO EFFECTIVENESS

Section 1 of this Amendment shall become effective only upon the satisfaction of
all of the following conditions precedent (the date of satisfaction of such
conditions being referred to herein as the "Sixth Amendment Effective Date"):

- 3 -

--------------------------------------------------------------------------------

A.    On or before the Sixth Amendment Effective Date, Borrower shall deliver to
Bank executed copies of this Amendment, dated the Sixth Amendment Effective
Date.

B.    Bank shall have executed this Agreement.

C.    On or before the Sixth Amendment Effective Date, all corporate and other
proceedings taken or to be taken in connection with the transactions
contemplated hereby and all documents incidental thereto not previously found
acceptable by Bank and its counsel shall be satisfactory in form and substance
to Bank and such counsel, and Bank and such counsel shall have received all such
counterpart originals or certified copies of such documents as Bank may
reasonably request.

Section 3. BORROWER'S REPRESENTATIONS AND WARRANTIES

In order to induce Bank to enter into this Amendment and to amend the Credit
Agreement in the manner provided herein, Borrower represents and warrants to
Bank that the following statements are true, correct and complete:

A.    Legal Status. Borrower has all requisite corporate power and authority to
enter into this Amendment and to carry out the transactions contemplated by, and
perform its obligations under, the Credit Agreement as amended by this Amendment
(the "Amended Agreement")

B.    Authorization and Validity. The execution and delivery of this Amendment
and the performance of the Amended Agreement have been duly authorized by all
necessary corporate action on the part of Borrower, and this Amendment and the
Amended Agreement are the legally valid and binding agreements and obligations
of Borrower or the party which executes the same, enforceable against Borrower
or the party which executes the same in accordance with their respective terms.

C.    No Violation. The execution and delivery by Borrower of this Amendment and
the performance by Borrower of the Amended Agreement do not and will not violate
any provision of any law or regulation, or contravene any provision of the
Articles of Incorporation or By-Laws of Borrower, or any of its Subsidiaries or
result In any breach of or default under any contract, obligation, indenture or
other instrument to which Borrower is a party or by which Borrower or any of its
Subsidiaries may be. bound.

D.    Incorporation of Representations and Warranties From Loan Documents. The
representations and warranties contained in the Credit Agreement and in the
other Loan Documents are and will be true and correct in all material respects
(except for any such representation or warranty that is qualified by materiality
or reference to a Material Adverse Effect, which such representation and
warranty shall be true and correct in all respects) on and as of the Sixth
Amendment Effective Date with the same effect as though such representations and
warranties were made on and as of that date, except to the extent such
representations and warranties specifically relate.to an earlier date, in which
case they were true, correct and complete in all material respects on and as of
such earlier date (except for any such representation or warranty that is
qualified by materiality or reference to a Material

- 4 -

--------------------------------------------------------------------------------

Adverse Effect, which such representation and warranty shall be true and correct
in all respects as of such earlier date).

E.    Absence of Default. No Event of Default and no Potential Event of Default
has occurred and is continuing or exists or will result from the consummation of
the transactions contemplated by this Amendment.

Section. 4. MISCELLANEOUS

A.     Reference to and Effect on the Credit Agreement and the Other Loan
Documents.

(i)
On and after the Sixth Amendment Effective Date, each reference in the Credit
Agreement to "this Agreement", "hereunder", "hereof', "herein" or words of like
import referring to the Credit Agreement, and each reference in the other Loan
Documents to the "Credit Agreement", "thereunder", "thereof' or words of like
import referring to the Credit Agreement shall mean and be a referenced to the
Amended Agreement.

(ii)
Except as specifically amended by this Amendment, the Credit Agreement and the
other Loan Documents shall remain in full force and effect and are hereby
ratified and confirmed.

(iii)
The execution, delivery and performance of this Amendment shall not, except as
expressly provided herein, constitute a waiver of any provisions of, or operate
as a waiver of any right, power or remedy of Bank under, the Credit Agreement or
any of the other Loan Documents.

B.    Termination of Consents. Except as set forth in the Credit Agreement as
amended by this Amendment, each of the Consents are hereby terminated as of the
Sixth Amendment Effective Date, and from and after the Sixth Amendment Effective
Date, Borrower agrees and acknowledges that it may not rely on any of the
Consents or seek to enforce the Consents against Bank.

E.
Fees and Expenses. Borrower acknowledges that all costs, fees and expenses as
described in the Section of the Credit Agreement entitled "MISCELLANEOUS: COSTS,
EXPENSES AND ATTORNEYS' FEES" incurred by Bank and its counsel with respect to
this Amendment and the documents and transactions contemplated hereby shall be
for the account of Borrower.

D.    Headings. Section and subsection headings in this Amendment are included
herein for convenience of reference only and shall not constitute a part of this
Amendment for any other purpose or be given any substantive effect.

- 5 -

--------------------------------------------------------------------------------

E.    Applicable Law. This Agreement shall be governed by and construed in
accordance with the laws of the State of California.

F.    Counterparts; Effectiveness. This Amendment may be executed in any number
of counterparts, each of which when executed and delivered shall be deemed to be
an original, and all of which when taken together shall constitute one and the
same Amendment. This Amendment (other than the provisions of Section 1 hereof,
the effectiveness of which is governed by Section 2 hereof) shall become
effective upon the execution of a counterpart hereof by Borrower and Bank and
each of the Loan Parties and receipt by Borrower and Bank of written or
telephonic notification of such execution and authorization of delivery thereof.

- 6 -

--------------------------------------------------------------------------------

IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be duly
executed and delivered by their respective officers thereunto duly authorized as
of the date first written above.

        
ALIGN TECHNOLOGY, INC.
 
By: /s/ ROGER E GEORGE
Name: Roger E George
Title: Vice President, Legal and Corporate Affairs, Corporate Secretary and
General Counsel
 
WELLS FARGO BANK, NATIONAL ASSOCIATION
 
By: /s/ CHARLES M. GOLDBERG
Name: Charles M. Goldberg
Title: Senior Vice President

- 7 -

--------------------------------------------------------------------------------

GUARANTORS' CONSENT AND REAFFIRMATION

Each undersigned guarantor of all indebtedness of ALIGN TECHNOLOGY, INC. to
WELLS FARGO BANK, NATIONAL ASSOCIATION hereby: (i) consents to the foregoing
Amendment; (ii) reaffirms its obligations under its respective Continuing
Guaranty; (iii) reaffirms its waivers of each and every one of the defenses to
such obligations as set forth in its respective Continuing Guaranty; and (iv)
reaffirms that Its obligations under its respective Continuing Guaranty are
separate and distinct from the obligations of any other party under the Credit
Agreement (as defined in said Amendment) and the other Loan Documents (as
defined in the Credit Agreement).

GUARANTORS:

CADENT HOLDINGS, INC.
 
By: /s/ ROGER E GEORGE
Name: Roger E George
Title: Secretary
 
CADENT, INC.
 
By: /s/ ROGER E GEORGE
Name: Roger E George
Title: Vice President and Secretary

- 8 -