UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13D/A

Amendment No. 4

Under the Securities Exchange Act of 1934

Biolase, Inc.

(Name of Issuer)

Common Shares, $0.001 par value

(Title of Class of Securities)

090911108

(CUSIP Number)

(Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications)

March 12, 2014

(Date of Event which requires Filing of this Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition which is the subject of this Schedule 13D, and is filing this schedule because of §§ 240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box ¨

Item 1. Security and Issuer.

This Amendment No. 4 (the “Amendment”) amends the Schedule 13D originally filed with the Securities and Exchange Commission on November 22, 2013, as previously amended by Amendment No. 1, filed on December 20, 2013, Amendment No. 2, filed on February 13, 2014 and Amendment No. 3, filed on March 11, 2014 (the “Original Schedule 13D,” and collectively with the Amendment, the “Statement”) with respect to the shares of common par value $0.001 per share (“Common Stock” or the “Shares”) of Biolase, Inc. (the “Issuer”), whose principal executive offices are located at 4 Cromwell, Irvine, CA 92618.

Item 4. Purpose of Transaction

Item 4 of the Statement is hereby amended by the addition of the following:

On March 12, 2014, Oracle Partners, L.P. (“Oracle”) issued a press release announcing it has commenced legal action in the Delaware Court of Chancery against the Issuer seeking to enjoin action in violation of the Issuer’s Bylaws and Delaware law. Oracle’s action in Delaware seeks: a declaratory judgment that the resignations of each of Dr. Alexander K. Arrow and Dr. Sam Low were effective on February 28, 2014, when those resignations were communicated to the Issuer or its Board, and that neither Dr. Arrow nor Dr. Low is currently a member of the Board; a declaratory judgment that the Board currently consists of only six members, not eight; and an Order temporarily, preliminarily and permanently enjoining the Issuer and its Board from taking any actions unless they are approved by at least four of the Issuer’s directors, excluding any votes of Drs. Arrow or Low.

The press release is attached to this Amendment as Exhibit 99.1 and is incorporated herein by reference.

Item 7.  Material to be Filed as Exhibits.

After reasonable inquiry and to the best of their knowledge and belief, the undersigned certify that the information set forth in this Schedule 13D is true, complete and correct.

Dated: March 12, 2014

Oracle Partners Commences Legal Action Against Biolase, Inc.

Seeks to Enjoin Unlawful Action

GREENWICH, Conn., March 12, 2014 /PRNewswire/ -- Oracle Partners, L.P. ("Oracle"), Biolase, Inc.'s ("Biolase" or the "Company") (Nasdaq: BIOL) largest shareholder, announced that it has commenced legal action in the Delaware Court of Chancery against the Company seeking to enjoin action in violation of the Company’s Bylaws and Delaware law. The unlawful action occurred when the Company, without approval of the Board, purportedly expanded the Company’s Board of Directors from six to eight directors and reappointed two directors who had previously resigned from the Board. Specifically:

Larry Feinberg, the Managing Member of Oracle’s general partner stated: “What seems to have occurred is a manipulation of the Board at the behest of the Chairman and CEO in an effort to protect his positions at the Company. We therefore have taken action against the Company in Delaware Court to prevent this unlawful activity.”

Oracle’s action in Delaware seeks the following relief:

Oracle Partners previously announced its nomination of four independent directors for election to the Biolase Board in response to these unlawful actions in furtherance of management and Board entrenchment, as well as the poor operating and financial performance of the Company.

Mr. Feinberg added: “Unlawful actions regarding Board composition cannot stand. We have brought our action in Delaware court for the benefit of all shareholders and intend to vigorously pursue and enforce shareholders’ rights.”

About Oracle Partners, L.P.

Oracle Partners is a fundamental-research driven investment fund that is exclusively focused on the global healthcare and bioscience industries.

Additional Information and Where to Find It

Oracle Partners, L.P., Oracle Institutional Partners, L.P., Oracle Ten Fund Master, L.P., Oracle Associates, LLC, Oracle Investment Management, Inc. and Larry N. Feinberg (collectively, "Oracle"), together with Paul N. Clark, Jeffrey M. Nugent, Frederic H. Moll and Eric Varma, are participants in the solicitation of proxies from stockholders in connection with the 2014 Annual Meeting of Stockholders (the "Annual Meeting") of Biolase, Inc. (the "Company"). Oracle intends to file a proxy statement (the "2014 Proxy Statement") with the Securities and Exchange Commission (the "SEC") in connection with the solicitation of proxies for the Annual Meeting.

Oracle may be deemed to beneficially own 6,105,383 shares of the Company's common stock, representing approximately 16.4% of the Company's outstanding common stock. None of the other participants owns in excess of 1% of the Company's common stock. Additional information regarding such participants, including their direct or indirect interests, by security holdings or otherwise, will be included in the 2014 Proxy Statement and other relevant documents to be filed with the SEC in connection with the Annual Meeting.

Promptly after filing its definitive 2014 Proxy Statement with the SEC, Oracle intends to mail the definitive 2014 Proxy Statement and an accompanying proxy card to some or all stockholders pursuant to applicable SEC rules. STOCKHOLDERS ARE URGED TO READ THE 2014 PROXY STATEMENT (INCLUDING ANY AMENDMENTS OR SUPPLEMENTS THERETO) AND ANY OTHER RELEVANT DOCUMENTS THAT THE COMPANY WILL FILE WITH THE SEC WHEN THEY BECOME AVAILABLE BECAUSE THEY WILL CONTAIN IMPORTANT INFORMATION. Stockholders may obtain, free of charge, copies of the definitive 2014 Proxy Statement and any other documents filed by Oracle with respect to the Company with the SEC in connection with the Annual Meeting at the SEC's website (http://www.sec.gov) or by writing to Oracle Partners, L.P., 200 Greenwich Avenue, Greenwich, CT 06830.