FOURTH AMENDMENT TO LOAN DOCUMENTS

Exhibit 10.8A

FOURTH AMENDMENT

TO

LOAN DOCUMENTS

This Fourth Amendment to Loan Documents is entered into as of March  7, 2007 (the “Amendment”), by and between COMERICA BANK (“Bank”), and ALIGN TECHNOLOGY, INC. (“Borrower”).

RECITALS

Borrower and Bank are parties to that certain Amended and Restated Loan and Security Agreement dated as of December 16, 2005 as amended from time to time, including without limitation by that certain First Amendment to Amended and Restated Loan and Security Agreement dated as of November 15, 2006, that certain Second Amendment to Amended and Restated Loan and Security Agreement dated as of December 1, 2006 and that certain Third Amendment to Amended and Restated Loan and Security Agreement dated as of December 22, 2006 (collectively, the “Agreement”) and that certain LIBOR Addendum to Amended and Restated Loan and Security Agreement dated as of December 1, 2006 (the “LIBOR Addendum”). The parties desire to amend the Agreement and the LIBOR Addendum in accordance with the terms of this Amendment.

NOW, THEREFORE, the parties agree as follows:

1.             The following defined terms are hereby amended or added to Section 1.1 of the Agreement to read as follows:

“Cash Equivalents” means investments with (i) a weighted average maturity of the total portfolio not exceeding 360 days, (ii) a maximum two (2) year maturity on any one security, and (iii) no more that 25% of the portfolio invested or having a tenor of more than two (2) years.

“Committed Revolving Line” means a Credit Extension of up to (i) beginning on the Closing Date through January 1, 2008, Twenty Million Dollars ($20,000,000), and (ii) beginning on January 2, 2008 and thereafter, Twenty Five Million Dollars ($25,000,000).

“Current Liabilities” means, as of any applicable date, all amounts that should, in accordance with GAAP, be included as current liabilities on the consolidated balance sheet of Borrower and its Subsidiaries, as at such date, plus, to the extent not already included therein, all Indebtedness owing by Borrower to Bank but excluding non-refundable deferred revenue.

“Quick Assets” means, at any date as of which the amount thereof shall be determined, the unrestricted cash and Cash Equivalents, plus net accounts receivable (with a minimum of $20,000,000 in domestic unrestricted cash during 2007 and a minimum of $25,000,000 in domestic unrestricted cash beginning March 31, 2008 and thereafter) of Borrower determined on a consolidated basis in accordance with GAAP.

“Revolving Maturity Date” means December 31, 2008.

2.             The reference to “5%” a subsection (g) of the defined term “Permitted Indebtedness” is amended to be “10%”.

3.             Subsection (e) of the defined term “Permitted Investment” is amended to read in its entirety as follows: “(e) Investments of Subsidiaries in or to other Subsidiaries or Borrower and Investments by Borrower in Subsidiaries not to exceed Three Million Dollars ($3,000,000) in the aggregate in any fiscal year provided however that (i) such Investments in Costa Rica in an aggregate amount exceeding $25,000,000 shall be deemed “Permitted Investments” if Bank is granted and maintains a first priority perfected security interest in the stock, units or other evidence of ownership of each Subsidiary (not to exceed sixty-six percent (66%) of such stock, units or other evidence of ownership of any such Subsidiary) on terms satisfactory to Bank.

1

4.             The following new Subsection (h) of the defined term “Permitted Transfer” is added to the Agreement to read as follows: “; or (h) Transfers of net fixed assets between Juarez, Mexico and Costa Rica”.

5.             The reference to “0.0125%” in Section 2.6 of the Agreement is amended to be “0.05%”.

6.             Section 6.2 of the Agreement is amended in its entirety to read as follows:

6.2           Financial Statements, Reports, Certificates. Borrower shall deliver to Bank: (i) as soon as available, but in any event within forty five (45) days after the end of each calendar quarter, a company prepared consolidated and consolidating balance sheet and income statement covering Borrower’s consolidated operations during such period, in a form reasonably acceptable to Bank and certified by a Responsible Officer, together with a Compliance Certificate signed by a Responsible Officer in substantially the form of Exhibit D hereto; (b) as soon as available, but in any event within ninety (90) days after the end of Borrower’s fiscal year, audited consolidated financial statements of Borrower prepared in accordance with GAAP, consistently applied, together with an opinion which is unqualified or otherwise consented to in writing by Bank on such financial statements of an independent certified public accounting firm reasonably acceptable to Bank; (c) copies of all statements, reports and notices sent or made available generally by Borrower to its security holders or to any holders of Subordinated Debt and all reports on Forms 10-K (which shall be delivered within ninety (90) days after the end of each fiscal year of Borrower) and 10-Q (which shall be delivered within forty-five (45) days after the end of each fiscal quarter of Borrower ) filed with the Securities and Exchange Commission; (d) promptly upon receipt of notice thereof, a report of any legal actions pending or threatened against Borrower or any Subsidiary that could reasonably be expected to result in damages or costs to Borrower or any Subsidiary of Five Million Dollars ($5,000,000) or more; and (e) such budgets, sales projections and pipelines, operating plans or other financial exhibits and information generally prepared by Borrower in the ordinary course of business as Bank may reasonably request from time to time.

(a)           Within fifteen (15) days after the end of each calendar quarter, aged listings of accounts receivable and accounts payable by invoice date.

(b)           Within 45 days after the last day of each quarter, Borrower shall deliver to Bank with the quarterly financial statements a Compliance Certificate certified as of the last day of the applicable quarter and signed by a Responsible Officer in substantially the form of Exhibit E hereto.

7.             Section 6.6(a) of the Agreement is amended to read as follows:

(a)           Quick Ratio. Borrower shall maintain, measured quarterly as of the last day of each calendar quarter, a ratio of Quick Assets to Current Liabilities, excluding deferred revenue from Current Liabilities, of at least 1.25 to 1.00.

8.             Section 6.7 of the Agreement is deleted to read as follows:

6.7           [Intentionally Omitted.]

9.             The reference to “2,000,000” in Section 8.6 of the Agreement is hereby amended to be “5,000,000”.

10.           Exhibit D to the Agreement is hereby amended and replaced in its entirety with Exhibit D attached hereto.

11.           Amendment to LIBOR Addendum: The reference to “a 3 month or 12 month period” in Section 1(e)(1) and Section 1(e)(2) of the LIBOR Addendum are each amended to read “a 30, 60, 90 or 360 day period”.

12.           Unless otherwise defined, initially capitalized terms in this Amendment shall be as defined in the Agreement. The Agreement, as amended hereby, shall be and remain in full force and effect in accordance with its respective terms and hereby is ratified and confirmed in all respects. Borrower ratifies and reaffirms the

2

continuing effectiveness of all instruments, documents and agreements entered into in connection with the Agreement. As a condition to the effectiveness of this Amendment, Borrower shall pay Bank an amount equal to the Bank Expenses incurred in connection with the preparation of this Amendment.

13.           Borrower represents and warrants that the representations and warranties contained in the Agreement are true and correct as of the date of this Amendment, and that no Event of Default has occurred and is continuing. This Amendment may be executed in two or more counterparts, each of which shall be deemed an original, but all of which together shall constitute one instrument.

14.           This Amendment may be executed in two or more counterparts, each of which shall be deemed an original, but all of which together shall constitute one instrument.

15.           As a condition to the effectiveness of this Amendment, Bank shall have received, in form and substance satisfactory to Bank, the following:

(i)            this Amendment, duly executed by Borrower;

(ii)           Corporate Resolutions to Borrow;

(iii)          an amount equal to all Bank Expenses incurred through the date of this Amendment; and

(iv)          such other documents, and completion of such other matters, as Bank may reasonably deem necessary or appropriate.

IN WITNESS WHEREOF, the undersigned have executed this Amendment as of the first date above written.

3

EXHIBIT D

COMPLIANCE CERTIFICATE

TO: COMERICA BANK

FROM: ALIGN TECHNOLOGY, INC.

The undersigned authorized officer of Align Technology, Inc. hereby certifies that in accordance with the terms and conditions of the Amended and Restated Loan and Security Agreement between Borrower and Bank (the “Agreement”), (i) Borrower is in complete compliance for the period ending              with all required covenants, including without limitation Section 6.6 and 6.7, except as noted below and (ii) all representations and warranties of Borrower stated in the Agreement are true and correct in all material respects as of the date hereof. Attached herewith are the required documents supporting the above certification. The Officer further certifies that these are prepared in accordance with Generally Accepted Accounting Principles (GAAP) and are consistently applied from one period to the next except as explained in an accompanying letter or footnotes.