BIOL Biolase Inc

Filed Pursuant to Rule 424(b)(5)
Registration No. 333-266852

Prospectus Supplement

(to Prospectus dated August 24, 2022)

331,000 Shares of Common Stock

Pre-Funded Warrants to Purchase 779,940 Shares of Common Stock

779,940 Shares of Common Stock Underlying the Pre-Funded Warrants

BIOLASE, Inc.

We are offering 331,000 shares of our common stock, $0.001 par value per share (the “Common Stock”), and pre-funded warrants (the “Pre-Funded Warrants”) to purchase 779,940 shares of our common stock, directly to a single institutional investor pursuant to this prospectus supplement and the accompanying prospectus. The per share offering price of the shares is $1.23 and the offering price per Pre-Funded Warrant is $1.229 (and each share of common stock and Pre-Funded Warrant shall be coupled with two Common Warrants (as defined below), each to purchase one share of our common stock).

We are offering to the institutional investor, with respect to the purchase of shares of common stock that would otherwise result in the purchaser’s beneficial ownership exceeding more than 4.99% (or, upon election of the holder, 9.99%) of our outstanding common stock immediately following the consummation of this offering, the opportunity to purchase one Pre-Funded Warrant in lieu of one share of our common stock. Subject to limited exceptions, a holder of Pre-Funded Warrants will not have the right to exercise any portion of its Pre-Funded Warrants if the holder, together with its affiliates, would beneficially own in excess of 4.99% (or, upon election of the holder, 9.99%) of the number of shares of common stock outstanding immediately after giving effect to such exercise. Each Pre-Funded Warrant will be exercisable for one share of our common stock. The purchase price of each Pre-Funded Warrant will be equal to the price per one share of common stock ($1.23), minus $0.001, and the remaining exercise price of each Pre-Funded Warrant will equal $0.001 per share. The Pre-Funded Warrants will be immediately exercisable and may be exercised at any time until all of the Pre-Funded Warrants are exercised in full. This prospectus supplement also relates to the offering of shares of our common stock issuable upon exercise of such Pre-Funded Warrants.

In a concurrent private placement, we are also offering to the institutional investor common warrants to purchase an aggregate of up to 2,221,880 shares of our common stock (the “Common Warrants”) at an exercise price of $1.23 per share. The Common Warrants will become exercisable on the effective date of the stockholder approval for the issuance of the shares of common stock issuable upon exercise of the Common Warrants (the “Stockholder Approval Date”) and will expire on the date that is fifth anniversary of the Stockholder Approval Date. The Common Warrants and the shares of common stock issuable upon the exercise of such warrants are not being registered under the Securities Act of 1933, as amended (the “Securities Act”), and are not being offered pursuant to this prospectus supplement and the accompanying prospectus and are being offered pursuant to an exemption from the registration requirements of the Securities Act provided in Section 4(a)(2) of the Securities Act and Rule 506(b) promulgated thereunder.

Our common stock is listed on The Nasdaq Capital Market under the symbol “BIOL.” On December 6, 2023, the last reported sale price of our common stock on The Nasdaq Capital Market was $1.24 per share.

As of the date of this prospectus supplement, the aggregate market value of our outstanding common stock held by non-affiliates is approximately $5,674,595, which is calculated based on 3,084,019 shares of our outstanding common stock held by non-affiliates and a price of $1.84 per share, the closing price of our common stock on October 10, 2023, which is the highest closing sale price of our common stock on the Nasdaq Capital Market within the prior 60 days of this prospectus supplement. During the prior twelve calendar month period that ends on and includes the date hereof, we have not offered or sold any shares of our common stock pursuant to General Instruction I.B.6 to Form S-3.

Investing in our common stock involves a high degree of risk. Before buying any of our securities, you should carefully read “Risk Factors” on page S-5 of this prospectus supplement, and under similar headings in the other documents that are incorporated by reference into this prospectus supplement and the accompanying prospectus.

We have engaged Maxim Group LLC to act as our exclusive placement agent in connection with this offering to use their reasonable best efforts to place the shares of common stock and Pre-Funded Warrants offered by this prospectus supplement. We have agreed to pay the placement agent the fees set forth in the table below.

Delivery of the shares of our common stock and Pre-Funded Warrants is expected to be made on or about December 8, 2023.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or passed upon the adequacy or accuracy of this prospectus supplement or the accompanying base prospectus. Any representation to the contrary is a criminal offense.

MAXIM GROUP LLC

The date of this prospectus supplement is December 6, 2023

TABLE OF CONTENTS

Prospectus Supplement

Prospectus

No dealer, salesperson or other person is authorized to give any information or to represent anything not contained in this prospectus supplement or the accompanying prospectus. You must not rely on any unauthorized information or representations. This prospectus supplement and the accompanying prospectus are an offer to sell only the securities offered hereby, but only under circumstances and in jurisdictions where it is lawful to do so. The information contained in this prospectus supplement and the accompanying prospectus is current only as of their respective dates.

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ABOUT THIS PROSPECTUS SUPPLEMENT

On August 12, 2022, we filed with the SEC a registration statement on Form S-3 (File No. 333-266852) utilizing a shelf registration process relating to the securities described in this prospectus supplement, which registration statement was declared effective on August 24, 2022. Under this shelf registration process, we may, from time to time, sell up to $50 million in the aggregate of shares of common stock, shares of preferred stock, debt securities, warrants, rights and units.

This document consists of two parts. The first part is the prospectus supplement, including the documents incorporated by reference herein, which describes the specific terms of this offering. The second part, the accompanying prospectus, including the documents incorporated by reference therein, provides more general information. In general, when we refer only to the prospectus, we are referring to both parts of this document combined. Before you invest, you should carefully read this prospectus supplement, the accompanying prospectus, all information incorporated by reference herein and therein, as well as the additional information described under the heading “Where You Can Find More Information.” These documents contain information you should carefully consider when deciding whether to invest in our securities.

This prospectus supplement may add, update or change information contained in the accompanying prospectus. To the extent there is a conflict between the information contained in this prospectus supplement and the accompanying prospectus, you should rely on information contained in this prospectus supplement, provided that if any statement in, or incorporated by reference into, one of these documents is inconsistent with a statement in another document having a later date, the statement in the document having the later date modifies or supersedes the earlier statement. Any statement so modified will be deemed to constitute a part of this prospectus only as so modified, and any statement so superseded will be deemed not to constitute a part of this prospectus.

You should rely only on the information contained in this prospectus supplement, the accompanying prospectus, any document incorporated by reference herein or therein, or any free writing prospectuses we may provide to you in connection with this offering. Neither we nor the placement agent have authorized anyone to provide you with any different information. We take no responsibility for, and can provide no assurance as to the reliability of, any other information that others may provide to you. The information contained in this prospectus supplement, the accompanying prospectus, and in the documents incorporated by reference herein or therein is accurate only as of the date such information is presented. Our business, financial condition, results of operations and prospects may have changed since that date.

This prospectus supplement and the accompanying prospectus do not constitute an offer to sell or the solicitation of an offer to buy any securities other than the shares of common stock and Pre-Funded Warrants to which it relates, nor does this prospectus supplement and the accompanying prospectus constitute an offer to sell or the solicitation of an offer to buy securities in any jurisdiction to any person to whom it is unlawful to make such offer or solicitation in such jurisdiction.

Securities offered pursuant to the registration statement to which this prospectus supplement relates may only be offered and sold if not more than three years have elapsed since August 24, 2022, the initial effective date of the registration statement, subject to the extension of this period in compliance with applicable SEC rules.

We note that the representations, warranties and covenants made by us in any agreement that is filed as an exhibit to any document that is incorporated by reference herein were made solely for the benefit of the parties to such agreement, including, in some cases, for the purpose of allocating risk among the parties to such agreement, and should not be deemed to be a representation, warranty or covenant to you. Moreover, such representations, warranties or covenants were accurate only as of the date when made. Accordingly, such representations, warranties and covenants should not be relied on as accurately representing the current state of our affairs.

References in this prospectus to “BIOL”, “the Company”, “we”, “us”, “our” or “its”, unless the context otherwise requires, refer to BIOLASE, Inc., a Delaware corporation, together with its consolidated subsidiaries.

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CAUTIONARY NOTE REGARDING FORWARD LOOKING STATEMENTS

This prospectus includes “forward-looking statements”, as such term is used within the meaning of the Private Securities Litigation Reform Act of 1995. These “forward-looking statements” are not based on historical fact and involve assessments of certain risks, developments, and uncertainties in our business looking to the future. Such forward-looking statements can be identified by the use of terminology such as “may”, “will”, “should”, “expect”, “anticipate”, “estimate”, “intend”, “continue”, or “believe”, or the negatives or other variations of these terms or comparable terminology. Forward-looking statements may include projections, forecasts, or estimates of future performance and developments. Forward-looking statements contained in this prospectus are based upon assumptions and assessments that we believe to be reasonable as of the date of this prospectus. Whether those assumptions and assessments will be realized will be determined by future factors, developments, and events, which are difficult to predict and may be beyond our control. Actual results, factors, developments, and events may differ materially from those we assumed and assessed. Risks, uncertainties, contingencies, and developments, including those identified in the “Risk Factors” section of this prospectus and in our most recent Annual Report on Form 10-K, subsequent Quarterly Reports on Form 10-Q and other filings we make with the SEC pursuant to Section 13(a), 13(c), 14 or 15(d) of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), incorporated by reference herein, could cause our future operating results to differ materially from those set forth in any forward-looking statement. There can be no assurance that any such forward-looking statement, projection, forecast or estimate contained can be realized or that actual returns, results, or business prospects will not differ materially from those set forth in any forward-looking statement. Given these uncertainties, readers are cautioned not to place undue reliance on such forward-looking statements. We disclaim any obligation to update any such factors or to publicly announce the results of any revisions to any of the forward-looking statements contained herein to reflect future results, events or developments.

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RISK FACTORS

Investing in our securities involves a high degree of risk You should carefully consider the risks described below and all of the information contained or incorporated by reference in this prospectus, including the risk factors described in our Annual Report on Form 10-K for the year ended December 31, 2022, any subsequent Quarterly Reports on Form 10-Q, and all other information contained or incorporated by reference into this prospectus supplement and the accompanying base prospectus before deciding whether to purchase the securities offered hereby. Our business, financial condition, results of operations and prospects could be materially and adversely affected by these risks.

Risks Related to This Offering

Our management will have broad discretion over the use of the net proceeds from this offering, you may not agree with how we use the proceeds and the proceeds may not be invested successfully.

Our management will have broad discretion as to the use of the net proceeds from this offering and could use them for purposes other than those contemplated at the time of commencement of this offering. Accordingly, you will be relying on the judgment of our management regarding the use of these net proceeds, and you will not have the opportunity, as part of your investment decision, to assess whether the proceeds are being used appropriately. It is possible that, pending their use, we may invest the net proceeds in a way that does not yield a favorable, or any, return for us. The failure of our management to use such funds effectively could have a material adverse effect on our business, financial condition, operating results and cash flows.

You will experience immediate and substantial dilution in the net tangible book value per share of the common stock you purchase.

Since the price per share of our common stock being and Pre-Funded Warrants offered is substantially higher than the net tangible book value per share of our common stock, you will suffer immediate and substantial dilution in the net tangible book value of the common stock you purchase in this offering or the common stock underlying the Pre-Funded Warrants you purchase in this offering. Based on an offering price of $1.23 per share and $1.229 per Pre-Funded Warrant, if you purchase shares of common stock or Pre-Funded Warrants in this offering, you will suffer immediate and substantial dilution of $0.26 per share with respect to the net tangible book value of the common stock. See the section entitled “Dilution” below for a more detailed discussion of the dilution you will incur if you invest in this offering.

You may experience future dilution as a result of future equity offerings and other issuances of our common stock or other securities. In addition, this offering and future equity offerings and other issuances of our common stock or other securities may adversely affect our common stock price.

In order to raise additional capital, we may in the future offer additional shares of our common stock or other securities convertible into or exchangeable for our common stock at prices that may not be the same as the price per share in this offering. We may not be able to sell shares or other securities in any other offering at a price per share that is equal to or greater than the price per share paid by the investor in this offering, and investors purchasing shares or other securities in the future could have rights superior to existing stockholders. The price per share at which we sell additional shares of our common stock or securities convertible into common stock in future transactions may be higher or lower than the price per share or Pre-Funded Warrant in this offering. In addition, we are issuing Common Warrants to purchase 2,221,880 shares of common stock in a concurrent private placement. You will incur dilution upon exercise of any outstanding stock options, warrants or upon the issuance of shares of common stock under our stock incentive programs. In addition, the sale of shares and Pre-Funded Warrants in this offering and any future sales of a substantial number of shares of our common stock in the public market, or the perception that such sales may occur, could adversely affect the price of our common stock. We cannot predict the effect, if any, that market sales of those shares of common stock or the availability of those shares for sale will have on the market price of our common stock.

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There is no public market for the Pre-Funded Warrants to purchase shares of our common stock being offered in this offering.

There is no established public trading market for the Pre-Funded Warrants being offered in this offering, and we do not expect a market to develop. In addition, we do not intend to apply to list the Pre-Funded Warrants on any national securities exchange or other nationally recognized trading system, including The Nasdaq Capital Market. Without an active trading market, the liquidity of the Pre-Funded Warrants will be limited.

The Pre-Funded Warrants purchased in this offering do not entitle the holder to any rights as common stockholders until the holder exercises the warrant for shares of our common stock.

Until you acquire shares of our common stock upon exercise of your Pre-Funded Warrants purchased in this offering, such warrants will not provide you any rights as a common stockholder, except as set forth therein. Upon exercise of your Pre-Funded Warrants purchased in this offering, you will be entitled to exercise the rights of a common stockholder only as to matters for which the record date occurs on or after the exercise date.

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USE OF PROCEEDS

We estimate that the net proceeds from this offering will be approximately $1.1 million, after deducting the placement agent’s fees and the estimated offering expenses payable by us.

The precise amount and timing of the application of such net proceeds will depend upon our funding requirements and the availability and cost of other funds. Our Board and management will have considerable discretion in the application of the net proceeds from this offering, and it is possible that we may allocate the proceeds differently than investors in the offering may desire or that we may fail to maximize the return on these proceeds. You will be relying on the judgment of our management with regard to the use of proceeds from this offering, and you will not have the opportunity, as part of your investment decision, to assess whether the proceeds are being used appropriately.

We intend to use the proceeds of this offering for working capital.

We may temporarily invest the net proceeds in short-term, interest-bearing instruments or other investment-grade securities.

DIVIDEND POLICY

We have not declared or paid dividends to holders of our common stock since inception and do not plan to pay cash dividends in the foreseeable future. We currently intend to retain earnings, if any, to finance our growth. In addition, the terms of our outstanding Series H and Series J convertible preferred stock provide that we pay dividends in kind (PIK dividends) under certain circumstances.

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DILUTION

Purchasers of shares of our common stock or Pre-Funded Warrants in this offering will experience an immediate dilution of the net tangible book value per share of our common stock. Our net tangible book value as of September 30, 2023 was approximately $3.0 million or $1.31 per share of our common stock (based upon approximately 2.3 million shares of our common stock outstanding as of that date). Net tangible book value per share is equal to our total tangible assets less our total liabilities, divided by the number of shares of our outstanding common stock.

Dilution per share of common stock equals the difference between the amount paid by purchasers of common stock in this offering (ascribing no value to the Common Warrants) and the net tangible book value per share of our common stock immediately after this offering.

Our pro forma net tangible book value as of September 30, 2023 was approximately $3.0 million or $0.96 per share of our common stock (based upon approximately 3.1 million shares of our common stock outstanding as of that date). Pro forma net tangible book value per share represents the amount of our total tangible assets less our total liabilities, after giving effect to the issuance of 816,435 shares of common stock upon conversion of preferred stock.

After taking into account the pro forma adjustments set forth above and the sale by us in this offering of 331,000 shares of common stock at an offering price of $1.23 per share and Pre-Funded Warrants to purchase up to 779,940 shares of our common stock at an offering price of $1.229 per Pre-Funded Warrant (assuming the Pre-Funded Warrants have been exercised and assuming no exercise of the Common Warrants issued in the concurrent private placement), after deducting estimated offering expenses and placement agent’s fees and expenses payable by us, our pro forma as adjusted net tangible book value as of September 30, 2023 would have been approximately $4.1 million, or $0.97 per share of our common stock. This represents an immediate increase in pro forma net tangible book value to existing stockholders of $0.01 per share of our common stock and an immediate dilution to purchasers in this offering of $0.26 per share of our common stock.

The information above is as of September 30, 2023 and excludes, as of that date (vested and unvested):

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DESCRIPTION OF PRE-FUNDED WARRANTS

The following summary of certain terms and provisions of the Pre-Funded Warrants that are being offered hereby is not complete and is subject to, and qualified in its entirety by the provisions of, the Pre-Funded Warrants. You should carefully review the terms and provisions of the form of the Pre-Funded Warrant for a complete description of the terms and conditions of the Pre-Funded Warrants.

The term “pre-funded” refers to the fact that the purchase price of our common stock in this offering includes almost the entire exercise price that will be paid under the Pre-Funded Warrants, except for a nominal remaining exercise price of $0.001. The purpose of the Pre-Funded Warrants is to enable investors that may have restrictions on their ability to beneficially own more than 4.99% (or, upon election of the holder, 9.99%) of our outstanding common stock following the consummation of this offering the opportunity to invest capital into our company without triggering their ownership restrictions, by receiving Pre-Funded Warrants in lieu of our common stock which would result in such ownership of more than 4.99% (or 9.99%), and receive the ability to exercise their option to purchase the shares underlying the Pre-Funded Warrants at such nominal price at a later date.

Duration and Exercise Price. The Pre-Funded Warrants offered hereby will entitle the holder thereof to purchase up to an aggregate of 779,940 shares of our common stock at a nominal exercise price of $0.001 per share, commencing immediately on the date of issuance, expected to be December 8, 2023 until exercised in full. In lieu of making the cash payment otherwise contemplated to be made to us upon the exercise of a Pre-Funded Warrant in payment of the aggregate exercise price, the holder may, in its sole discretion, elect to exercise the Pre-Funded Warrant through a cashless exercise, in which case the holder would receive upon such exercise the net number of common shares determined according to the formula set forth in the Pre-Funded Warrant. If we do not issue the shares in a timely fashion, the Pre-Funded Warrant contains certain damages provisions. No fractional common shares will be issued in connection with the exercise of a Pre-Funded Warrant. The Pre-Funded Warrants will be issued separately from the common stock and may be transferred separately immediately thereafter.

Exercise Limitation. The holder will not have the right to exercise any portion of the Pre-Funded Warrant if the holder (together with its affiliates) would beneficially own in excess of 4.99% (or, upon election of the holder, 9.99%) of the number of shares of our common stock outstanding immediately after giving effect to the exercise, as such percentage ownership is determined in accordance with the terms of the Pre-Funded Warrants. However, the holder may increase or decrease such percentage, provided that any increase will not be effective until the 61st day after such election.

Exercise Price Adjustment. The exercise price of the Pre-Funded Warrants is subject to appropriate adjustment in the event of certain stock dividends and distributions, stock splits, stock combinations, reclassifications or similar events affecting our common stock and also upon any distributions of assets, including cash, stock or other property to our stockholders.

Transferability. Subject to applicable laws, the Pre-Funded Warrants may be offered for sale, sold, transferred, or assigned without our consent.

Exchange Listing. There is no established trading market for the Pre-Funded Warrants, and we do not expect a market to develop. in addition, we do not intend to apply for the listing of the Pre-Funded Warrants on any national securities exchange or other trading market. Without an active trading market, the liquidity of the Pre-Funded Warrants will be limited.

Fundamental Transactions. Subject to certain exceptions, if a fundamental transaction occurs, then the successor entity will succeed to, and be substituted for us, and may exercise every right and power that we may exercise and will assume all of our obligations under the Pre-Funded Warrants with the same effect as if such successor

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entity had been named in the pre-funded warrant itself. If holders of our common stock are given a choice as to the securities, cash or property to be received in a fundamental transaction, then the holder shall be given the same choice as to the consideration it receives upon any exercise of the pre-funded warrant following such fundamental transaction.

Rights as a Stockholder. Except as otherwise provided in the Pre-Funded Warrants or by virtue of such holder’s ownership of shares of our common stock, the holder of a Pre-Funded Warrants does not have the rights or privileges of a holder of our common stock, including any voting rights, until the holder exercises the Pre-Funded Warrant.

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PRIVATE PLACEMENT TRANSACTION

Concurrently with the sale of common stock in this offering, we will issue and sell to the investor in this offering Common Warrants to purchase up to an aggregate of 2,221,880 shares of common stock at an exercise price equal to $1.23 per share.

The Common Warrants and the shares of common stock issuable upon the exercise of such warrants are not being registered under the Securities Act, are not being offered pursuant to this prospectus supplement and the accompanying prospectus and are being offered pursuant to the exemption provided in Section 4(a)(2) under the Securities Act and Rule 506(b) promulgated thereunder. Accordingly, purchasers may only sell shares of common stock issued upon exercise of the Common Warrants pursuant to an effective registration statement under the Securities Act covering the resale of those shares, an exemption under Rule 144 under the Securities Act or another applicable exemption under the Securities Act.

Exercisability. Common Warrants are exercisable for a period of five years commencing on the Stockholder Approval Date and expiring on the five year anniversary of the Stockholder Approval Date. The Common Warrants will be exercisable, at the option of each holder, in whole or in part by delivering to us a duly executed exercise notice and, at any time a registration statement registering the issuance of the shares of common stock underlying such warrants under the Securities Act is effective and available for the issuance of such shares, or an exemption from registration under the Securities Act is available for the issuance of such shares, by payment in full in immediately available funds for the number of shares of common stock purchased upon such exercise. If at any time after the six month anniversary of the closing of the offering a registration statement registering the issuance of the shares of common stock underlying the Common Warrants under the Securities Act is not effective or available, the holder may, in its sole discretion, elect to exercise the Common Warrants through a cashless exercise, in which case the holder would receive upon such exercise the net number of shares of common stock determined according to the formula set forth in such warrant.

Exercise Limitation. A holder will not have the right to exercise any portion of the Common Warrants if the holder (together with its affiliates) would beneficially own in excess of 4.99% (or, upon election of the holder, 9.99%) of the number of shares of our common stock outstanding immediately after giving effect to the exercise, as such percentage ownership is determined in accordance with the terms of such warrants. However, any holder may increase or decrease such percentage, provided that any increase will not be effective until the 61st day after such election.

Exercise Price Adjustment. The exercise price of the Common Warrants is subject to appropriate adjustment in the event of certain stock dividends and distributions, stock splits, stock combinations, reclassifications or similar events affecting our common stock and also upon any distributions of assets, including cash, stock or other property to our stockholders as well as if we are deemed to have issued securities at a price below the exercise price of the Common Warrants.

Exchange Listing. There is no established trading market for Common Warrants and we do not expect a market to develop. In addition, we do not intend to apply for the listing of the Common Warrants on any national securities exchange or other trading market.

Fundamental Transactions. If a fundamental transaction occurs, then the successor entity will succeed to, and be substituted for us, and may exercise every right and power that we may exercise and will assume all of our obligations under the Common Warrants with the same effect as if such successor entity had been named in the warrant itself. If holders of our common stock are given a choice as to the securities, cash or property to be received in a fundamental transaction, then the holder shall be given the same choice as to the consideration it receives upon any exercise of the Common Warrants following such fundamental transaction. In addition, the successor entity, at the request of warrant holders, will be obligated to purchase any unexercised portion of the Common Warrants in accordance with the terms of such warrants. Notwithstanding the foregoing, in the event of

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a fundamental transaction, the holders of the Common Warrants have the right to require us or a successor entity to redeem the common warrants for cash in the amount of the Black Scholes Value (as defined in each warrant) of the unexercised portion of the common warrants concurrently with or within 30 days following the consummation of a fundamental transaction.

However, in the event of a fundamental transaction which is not in our control, including a fundamental transaction not approved by our board of directors, the holders of the Common Warrants will only be entitled to receive from us or our successor entity, as of the date of consummation of such fundamental transaction the same type or form of consideration (and in the same proportion), at the Black Scholes Value of the unexercised portion of the Common Warrant that is being offered and paid to the holders of our common stock in connection with the fundamental transaction, whether that consideration is in the form of cash, stock or any combination of cash and stock, or whether the holders of our common stock are given the choice to receive alternative forms of consideration in connection with the fundamental transaction.

Rights as a Stockholder. Except as otherwise provided in the Common Warrants or by virtue of such holder’s ownership of shares of our common stock, the holder of a Common Warrants will not have the rights or privileges of a holder of our common stock, including any voting rights, until the holder exercises such warrant.

Resale/Registration Rights. We are required within 30 days of the offering to file a registration statement providing for the resale of the shares of common stock issued and issuable upon the exercise of the Common Warrants. We are required to use commercially reasonable efforts to cause such registration to become effective within 121 days of the date of issuance (or within 181 days following the closing date of the offering if the SEC has informed us that it intends to review such registration statement), subject to certain exceptions, and to keep such registration statement effective at all times until no investor owns any Common Warrants or shares issuable upon exercise thereof.

Right of Participation. In addition, from the date of the securities purchase agreement until the date that is twelve (12) months after the Stockholder Approval Date (as defined in the securities purchase agreement), upon any issuance by us or any of our subsidiaries of common stock, common stock equivalents or preferred stock for cash consideration, Indebtedness (as defined in the securities purchase agreement) or a combination of securities hereof (a “Subsequent Financing”), the investor in the offering shall have the right to participate in up to an amount of the Subsequent Financing equal to 33% of the Subsequent Financing on the same terms, conditions and price provided for in the Subsequent Financing.

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PLAN OF DISTRIBUTION

Maxim Group LLC has agreed to act as the exclusive placement agent for us in connection with this offering, subject to the terms and conditions of the placement agency agreement dated December 6, 2023. We refer to Maxim Group LLC as the placement agent. The placement agent is not purchasing or selling any of the shares of our common stock or Pre-Funded Warrants offered by this prospectus supplement, nor are they required to arrange the purchase or sale of any specific number or dollar amount of shares of our common stock or Pre-Funded Warrants but the placement agent has agreed to use its reasonable best efforts to arrange for the sale of all of the shares of our common stock and Pre-Funded Warrants offered hereby. Therefore, we have entered into a securities purchase agreement directly with investors in connection with this offering and we may not sell the entire amount of shares of our common stock or Pre-Funded Warrants offered pursuant to this prospectus supplement. We made offers only to a limited number of institutional accredited investors. Maxim Group LLC is also acting as the placement agent for the private placement transaction and is being paid a fee related to the placement of the Common Warrants.

We have agreed to indemnify the placement agent against specified liabilities, including liabilities under the Securities Act, and to contribute to payments the placement agent may be required to make in respect thereof.

Fees and Expenses

We have agreed to pay the placement agent a placement agent fee equal to 7.0% of the aggregate purchase price of the shares of our common stock and Pre-Funded Warrants sold in this offering. The following table shows the per share and total cash placement agent fees we will pay to the placement agent in connection with the sale of the shares of our common stock and Pre-Funded Warrants offered pursuant to this prospectus supplement and the accompanying prospectus, assuming the purchase of all of the shares and Pre-Funded Warrants offered hereby.

In addition, we have agreed to reimburse the actual out-of-pocket expenses of the placement agent up to $40,000.

We estimate that the total expenses of the offering payable by us, excluding the placement agent’ fees, will be approximately $100,000.

The placement agent may be deemed to be underwriters within the meaning of Section 2(a)(11) of the Securities Act, and any commissions received by them and any profit realized on the resale of the shares sold by them while acting as principals might be deemed to be underwriting discounts or commissions under the Securities Act. As an underwriter, each placement agent would be required to comply with the requirements of the Securities Act and the Securities Exchange Act of 1934, as amended (the “Exchange Act”), including, without limitation, Rule 415(a)(4) under the Securities Act and Rule 10b-5 and Regulation M under the Exchange Act. These rules and regulations may limit the timing of purchases and sales of shares by the placement agent acting as principal. Under these rules and regulations, each placement agent:

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This prospectus supplement and the accompanying prospectus may be made available in electronic format on websites or through other online services maintained by any of the placement agent or by an affiliate of such placement agent. Other than this prospectus supplement and the accompanying prospectus, the information on a placement agent’s website and any information contained in any other website maintained by a placement agent is not part of this prospectus supplement and the accompanying prospectus or the registration statement of which this prospectus supplement and the accompanying prospectus form a part, has not been approved and/or endorsed by us or the placement agent, and should not be relied upon by investors.

Our directors and officers have entered into lock-up agreements. Under these agreements, these individuals have agreed, subject to specified exceptions, not to sell or transfer any shares of common stock or securities convertible into, or exchangeable or exercisable for, our common stock during a period ending 30 days after the date of this prospectus supplement, without first obtaining the written consent of Maxim Group LLC. Specifically, these individuals have agreed, in part, not to:

Notwithstanding these limitations, these shares of common stock may be transferred under limited circumstances, including, without limitation, by gift, will or intestate succession.

Additionally, pursuant to the terms of the securities purchase agreement, subject to certain exceptions, from the date hereof until 30 days after the closing date of this offering, we may not issue, enter into any agreement to issue or announce the issuance or proposed issuance of any shares of common stock or Common Stock Equivalents (as defined in the securities purchase agreement), or, subject to certain exceptions, file any registration statement. We have also agreed, subject to certain exceptions, not to enter into a Variable Rate Transaction (as defined in the securities purchase agreement) for 180 days after the closing date of this offering.

The foregoing does not purport to be a complete statement of the terms and conditions of the placement agency agreement and the securities purchase agreement. A copy of the securities purchase agreement with the purchasers will be included as an exhibit to our Current Report on Form 8-K to be filed with the SEC and incorporated by reference into the registration statement of which this prospectus supplement and the accompanying prospectus form a part. See “Incorporation of Certain Information By Reference” and “Where You Can Find More Information.”

No action has been or will be taken in any jurisdiction (except in the United States) that would permit a public offering of the securities offered by this prospectus supplement and accompanying prospectus, or the possession, circulation or distribution of this prospectus supplement and accompanying prospectus or any other material relating to us or the securities offered hereby in any jurisdiction where action for that purpose is required. Accordingly, the securities offered hereby may not be offered or sold, directly or indirectly, and neither of this prospectus supplement and accompanying prospectus nor any other offering material or advertisements in connection with the securities offered hereby may be distributed or published, in or from any country or jurisdiction except in compliance with any applicable rules and regulations of any such country or jurisdiction. The placement agent may arrange to sell securities offered by this prospectus supplement and accompanying

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prospectus in certain jurisdictions outside the United States, either directly or through affiliates, where they are permitted to do so.

Relationships

The placement agent and their respective affiliates may provide from time to time in the future certain commercial banking, financial advisory, investment banking and other services for us in the ordinary course of their business, for which they may receive customary fees and commissions. In addition, from time to time, the placement agent and their affiliates may effect transactions for their own accounts or the account of customers, and hold on behalf of themselves or their customers, long or short positions in our debt or equity securities or loans, and may do so in the future. Except as disclosed in this prospectus supplement, we have no present arrangements with the placement agent for any further services.

The underwriters and their affiliates may in the future provide various investment banking and other financial services for us and our affiliates for which they may in the future receive customary fees.

In connection with an underwritten offering that closed in May 2023 (the “May 2023 Offering”), we issued 175,000 Series H Units, with each Series H Unit consisting of one share of Series H Convertible Preferred Stock and one Series H Warrant to purchase one-half of one (0.50) share of Series H Convertible Preferred Stock at an exercise price of $2,600.00 per whole share. We received aggregate gross proceeds from the May 2023 Offering of approximately $4.5 million, before deducting underwriting discounts and commissions and other transaction expenses payable by us. Maxim Group LLC and Lake Street Capital Markets, LLC acted as joint bookrunners in the May 2023 Offering. In connection with the May 2023 Offering, we entered into an underwriting agreement, dated May 24, 2023, with Lake Street, as the representative of the underwriters named therein, and on the closing of such offering on May 26, 2023, the underwriters received compensation of 6.5% of the $4.5 million of gross proceeds of the offering, as well as payment of certain expenses.

In September 2023, we entered into an underwriting agreement (the “Underwriting Agreement”) with Lake Street Capital Markets, LLC and Maxim Group LLC, as representatives of the several underwriters named therein (the “Underwriters”), pursuant to which we agreed to sell to the Underwriters, in a firm commitment underwritten public offering, 75,000 units (each a “Unit” and collectively, the “Units”), with each Unit consisting of (A) one share of our Series J Convertible Redeemable Preferred Stock, par value $0.001 per share (the “Series J Convertible Preferred Stock”), and (B) one warrant (each, a “Warrant” and collectively, the “Warrants”) to purchase one-half of one (0.50) share of Series J Convertible Preferred Stock, at a price to the public of $60.00 per Unit, less underwriting discounts and commissions. We apaid the Underwriters underwriting discounts totaling $315,000 and agreed to reimburse the underwriters for certain of their expenses in an amount up to $125,000,

Transfer Agent and Registrar

The transfer agent and registrar for our common stock is Computershare Trust Company NA. The Transfer Agent’s address is 250 Royall Street, Canton, Massachusetts 02021.

Listing

Our common stock is traded on the Nasdaq Capital Market under the symbol “BIOL.”

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LEGAL MATTERS

The validity of the securities being offered by this prospectus supplement will be passed upon for us by Blank Rome LLP, New York, New York. Ellenoff Grossman & Schole LLP, New York, New York, is acting as counsel for the placement agent in connection with the securities offered hereby.

EXPERTS

The consolidated financial statements and schedule of BIOLASE, Inc. as of December 31, 2022 and 2021 and for each of the two years in the period ended December 31, 2022 incorporated by reference into this prospectus and in the registration statement have been so incorporated in reliance upon the report of BDO USA, LLP (n/k/a BDO USA, P.C.), an independent registered accounting firm, incorporated herein by reference, given on the authority of said firm as experts in auditing and accounting.

WHERE YOU CAN FIND MORE INFORMATION

We have filed with the SEC a registration statement on Form S-3 under the Securities Act with respect to the securities offered by this prospectus supplement. This prospectus supplement and the accompanying prospectus, which are part of the registration statement, omits certain information, exhibits, schedules and undertakings set forth in the registration statement, as permitted by the SEC. For further information pertaining to us and the securities offered in this prospectus supplement, reference is made to that registration statement and the exhibits and schedules to the registration statement. Statements contained in this prospectus supplement and the accompanying prospectus as to the contents or provisions of any documents referred to in this prospectus are not necessarily complete, and in each instance where a copy of the document has been filed as an exhibit to the registration statement, reference is made to the exhibit for a more complete description of the matters involved.

We file annual, quarterly and current reports, proxy statements and other information with the SEC. Our SEC filings are available to the public on a website maintained by the SEC at www.sec.gov.

General information about our company, including our Annual Report on Form 10-K, Quarterly Reports on Form 10-Q and Current Reports on Form 8-K, as well as any amendments and exhibits to those reports, are available free of charge through our website at www.biolase.com as soon as reasonably practicable after we file them with, or furnish them to, the SEC. Information on any BIOLASE, Inc. website, any subsection, page, or other subdivision of any BIOLASE, Inc. website, or any website linked to by content on any BIOLASE, Inc. website, is not part of this prospectus and you should not rely on that information unless that information is also in this prospectus or incorporated by reference in this prospectus.

INCORPORATION OF CERTAIN INFORMATION BY REFERENCE

The SEC allows us to incorporate by reference into this prospectus supplement the information contained in other documents we file with the SEC, which means that we can disclose important information to you by referring you to those documents. Any statement contained in any document incorporated or deemed to be incorporated by reference in this prospectus supplement shall be deemed to be modified or superseded, for purposes of this prospectus, to the extent that a statement contained in or omitted from this prospectus supplement, or in any other subsequently filed document that also is or is deemed to be incorporated by reference in this prospectus supplement, modifies or supersedes such statement. Any such statement so modified or superseded shall not be deemed, except as so modified or superseded, to constitute a part of this prospectus supplement. We incorporate by reference the documents listed below which have been filed by us and any future filings we make with the SEC under Sections 13(a), 13(c), 14 or 15(d) of the Exchange Act (other than current reports furnished under

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Item 2.02 or Item 7.01 of Form 8-K and exhibits filed on such form that are related to such items unless such Form 8-K expressly provides to the contrary) subsequent to the date of this prospectus supplement and before the termination or completion of the offering of the securities covered by this prospectus. We incorporate by reference into this prospectus and the registration statement of which this prospectus supplement is a part the information or documents listed below that we have filed with the SEC (Commission File No. 001-36385):

Any statement contained in a document incorporated or deemed to be incorporated by reference into this prospectus supplement will be deemed to be modified or superseded for purposes of this prospectus supplement to the extent that a statement contained in this prospectus supplement or any other subsequently filed document that is deemed to be incorporated by reference into this prospectus supplement modifies or supersedes the statement. Any statement so modified or superseded will not be deemed, except as so modified or superseded, to constitute a part of this prospectus supplement.

We will provide each person to whom a prospectus supplement is delivered a copy of all of the information that has been incorporated by reference in this prospectus supplement but not delivered with the prospectus supplement. You may obtain copies of these filings, at no cost, through the “Investor Relations” section of our website (www.biolase.com) and you may request a copy of these filings (other than an exhibit to any filing unless we have specifically incorporated that exhibit by reference into the filing), at no cost, by writing or telephoning us at the following address:

BIOLASE, Inc.

27042 Towne Centre Drive, Suite 270

Lake Forest, California 92610

(949) 361-1200

Information on, or that can be accessed through, our website is not incorporated into this prospectus supplement or other securities filings and is not a part of these filings.

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PROSPECTUS

BIOLASE, INC.

$50,000,000 Aggregate Offering Price of

COMMON STOCK, PREFERRED STOCK, DEBT SECURITIES, WARRANTS, RIGHTS AND UNITS

BIOLASE, Inc., a Delaware corporation, may offer and sell from time to time, in one or more offerings, common stock, preferred stock, debt securities, warrants, rights and units for an aggregate initial offering price up to $50,000,000 in amounts, at prices and on terms that BIOLASE, Inc. will determine at the time of the offering.

This prospectus describes general terms that apply to these securities. When we decide to sell a particular class or series of these securities, we will provide specific terms of the securities, including the initial offering price and the aggregate amount of the offering, in one or more supplements to this prospectus. Any prospectus supplement may also add, update or change information contained in this prospectus. You should carefully read this prospectus and the applicable prospectus supplement, as well as the documents incorporated or deemed to be incorporated by reference in this prospectus, before you invest in our securities.

We may offer and sell these securities in the same offering or in separate offerings; to or through underwriters, dealers or agents; or directly to purchasers. The names of any underwriters, dealers or agents involved in the sale of our securities, their compensation and any over-allotment options held by them will be described in the applicable prospectus supplement. For a more complete description of the plan of distribution with respect to the securities covered by this prospectus, see the section entitled “Plan of Distribution” beginning on page 16 of this prospectus.

Our common stock trades on The Nasdaq Capital Market under the symbol “BIOL.” On August 18, 2022, the last reported sale price for our common stock on The Nasdaq Capital Market was $4.34 per share. As of August 18, 2022, the aggregate market value of our common stock held by our non-affiliates, as calculated pursuant to the rules of the Securities and Exchange Commission, was $29,466,170. Pursuant to General Instruction I.B.6 of Form S-3, in no event will we sell securities in a public offering with a value exceeding more than one-third of our “public float” (the market value of our common stock held by our non-affiliates) in any 12-month period so long as our public float remains below $75,000,000. We have sold $6,500,000 of securities in reliance on General Instruction I.B.6 of Form S-3 during the 12 calendar months prior to and including the date of this prospectus.

Investing in our securities involves substantial risks. You should consider the “Risk Factors” on page 2 of this prospectus, in the documents that are incorporated by reference into this prospectus and, if applicable, in risk factors described in any accompanying prospectus supplement before buying any of our securities.

NEITHER THE SECURITIES AND EXCHANGE COMMISSION NOR ANY STATE SECURITIES COMMISSION HAS APPROVED OR DISAPPROVED OF THESE SECURITIES OR PASSED UPON THE ADEQUACY OR ACCURACY OF THIS PROSPECTUS. ANY REPRESENTATION TO THE CONTRARY IS A CRIMINAL OFFENSE.

The date of this prospectus is August 24, 2022.

TABLE OF CONTENTS

This prospectus is part of a registration statement on Form S-3 that we filed with the Securities and Exchange Commission (the “SEC”) using a “shelf” registration process. Under this shelf registration process, we may, from time to time, sell any combination of the securities described in this prospectus in one or more offerings up to the aggregate amount of $50,000,000.

This prospectus provides you with a general description of the securities we may offer. A prospectus supplement may add to, update or change information contained in this prospectus, and, accordingly, to the extent inconsistent, information in this prospectus is superseded by the information in any prospectus supplement.

A prospectus supplement may describe, as applicable: the terms of the securities; the initial public offering price; the price paid for the securities; net proceeds; and the other specific terms related to the offering of the securities.

You should rely only on the information that we have provided or incorporated by reference in this prospectus, any applicable prospectus supplement, any related free writing prospectus that we may authorize to be provided to you and the other information to which we refer you. We have not authorized anyone to provide you with different or additional information. No dealer, salesperson or other person is authorized to give any information or to represent anything not contained in this prospectus or any applicable prospectus supplement or any related free writing prospectus that we may authorize to be provided to you. If anyone provides you with different or additional information, you should not rely on it. You should assume that the information in this prospectus, any applicable prospectus supplement or any related free writing prospectus is accurate only as of the date on the cover of the document and that any information we have incorporated by reference is accurate only as of the date of the document incorporated by reference, regardless of the time of delivery of this prospectus, any applicable prospectus supplement or any related free writing prospectus, or any sale of a security. Our business, financial condition, results of operations and prospects may have changed since those dates.

We urge you to carefully read this prospectus and any applicable prospectus supplement, together with the information incorporated in this prospectus by reference as described under the heading “Where You Can Find Additional Information.”

In this prospectus, unless otherwise specified or the context requires otherwise, we use the terms “Company,” “we,” “us” and “our” or similar references to refer to BIOLASE, Inc., a Delaware corporation, together with its consolidated subsidiaries.

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RISK FACTORS

We face a variety of significant and diverse risks, many of which are inherent in our business. You should carefully consider the risks described under the caption “Risk Factors” in our most recent annual report on Form 10-K, subsequent quarterly reports on Form 10-Q and other filings we make with the SEC pursuant to Section 13(a), 13(c), 14 or 15(d) of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), incorporated by reference in this prospectus, before making an investment decision. Additional risk factors may be included in any prospectus supplements relating to the offering of securities described in this prospectus. The occurrence of any of those risks could materially and adversely affect our business, prospects, financial condition, results of operations or cash flow. Other risks and uncertainties that we do not now consider to be material or of which we are not now aware may become important factors that affect us in the future.

CAUTIONARY STATEMENTS REGARDING FORWARD-LOOKING STATEMENTS

This prospectus, any prospectus supplement and the documents that we incorporate herein or therein by reference contain “forward-looking statements,” as defined in Section 27A of the Securities Act of 1933, as amended (the “Securities Act”), and Section 21E of the Exchange Act that involve risks, uncertainties and assumptions, which could cause actual results to differ materially from management’s expectations. Such forward-looking statements include statements, predictions or expectations regarding market opportunities, our plans for future products and services and enhancements of existing products and services, future market growth and our anticipated growth strategies, future demand for improved dental care and dental laser equipment, expansion of our international operations, compliance with laws and regulatory requirements, the impact of cost-saving measures and future decreases in expenses, statements regarding the effects of seasonality on revenue, anticipated cash needs, capital requirements and capital expenditures, needs for additional financing, anticipated use of proceeds from debt or equity financing, use of working capital, plans to explore potential collaborations, potential acquisitions of products and technologies, effects of engineering and development efforts, plans to expand our field sales force, the development of distributor relationships, our ability to attract customers, the adequacy of our facilities, products and solutions from competitors, our ability to maintain product quality standards, protection of patents and other technology, the ability of third-party payers to pay for costs of our products, limitations on capital expenditures, critical accounting policies and the impact of recent accounting pronouncements, recording tax benefits or other financial items in the future, plans, strategies, expectations or objectives of management for future operations, our financial condition or prospects and any other statement that is not historical fact. Forward-looking statements are identified by the use of words such as “may,” “might,” “will,” “intend,” “should,” “could,” “can,” “would,” “continue,” “expect,” “believe,” “anticipate,” “estimate,” “predict,” “outlook,” “potential,” “plan,” “seek,” and similar expressions and variations or the negatives of these terms or other comparable terminology.

Forward-looking statements are based on the expectations, estimates, projections, beliefs and assumptions of our management based on information available to management as of the date on which such forward-looking statement was made, all of which are subject to change. Forward-looking statements are subject to risks, uncertainties and other factors that are difficult to predict and could cause actual results to differ materially from those stated or implied by our forward-looking statements. Factors that could cause or contribute to such differences include, but are not limited to:

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Further information about factors that could materially affect the Company, including our results of operations, financial condition and stock price, is contained under the heading “Risk Factors” in this prospectus, under the heading “Risk Factors” contained in the applicable prospectus supplement and in the documents incorporated by reference into this prospectus and any prospectus supplement. Except as required by law, we undertake no obligation to revise or update any forward-looking statements to reflect changed assumptions, the occurrence of anticipated or unanticipated events, new information, changes to future results over time or otherwise.

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USE OF PROCEEDS

Unless otherwise indicated in the applicable prospectus supplement, we will use the net proceeds from the sale of securities offered by this prospectus for working capital, including new product development, launch and subsequent scale-ups, to potentially pay down the principal balance of term loans, as well as other general corporate purposes. The timing and amount of our actual expenditures will be based on many factors, including cash flows from operations and the anticipated growth of our business. As a result, unless otherwise indicated in the applicable prospectus supplement, our management will have broad discretion to allocate the net proceeds of the offerings. Pending their ultimate use, we intend to invest the net proceeds in short-term, investment-grade, interest-bearing instruments.

DESCRIPTION OF CAPITAL STOCK

The following summary description sets forth some of the general terms and provisions of our capital stock. Because this is a summary description, it does not contain all of the information that may be important to you. For a more detailed description of our capital stock, you should refer to the applicable provisions of the General Corporation Law of the State of Delaware (the “DGCL”) and our charter and bylaws as in effect at the time of any offering. Copies of our Amended and Restated Certificate of Incorporation, as amended (our “Charter”), and our Eighth Amended and Restated Bylaws (our “Bylaws”) are included as exhibits to the registration statement of which this prospectus forms a part.

Our Authorized Capital Stock

Under our Charter, we are authorized to issue 180,000,000 shares of our common stock, par value $0.001 per share, and 1,000,000 shares of preferred stock, par value $0.001 per share. As of August 15, 2022, there were 6,856,574 shares of our common stock issued and 6,854,771 shares of outstanding. In addition, as of August 15, 2022, 2,820,480 shares were subject to outstanding warrants to purchase shares of our common stock, 71,671 shares were subject to outstanding options to purchase shares of our common stock, 30,311 shares were subject to outstanding stock appreciation rights, 431,138 shares were subject to settlement of unvested restricted stock units and 404,814 shares were subject to outstanding phantom restricted stock units. As of August 15, 2022, no shares of our preferred stock were issued or outstanding.

Common Stock

Voting Rights. Holders of our common stock are entitled to one vote per share. Each of our directors is elected by the affirmative vote of a majority of the votes cast with respect to such director in uncontested elections. In a contested election, each of our directors is elected by an affirmative vote of a plurality of the votes cast by the shares represented and entitled to vote with respect to the election of such director. A “contested election” is defined in our Bylaws as an election with respect to which, as of the record date for the meeting at which directors are to be elected, the number of nominees exceeds the number of directors to be elected at such meeting. Vacancies on the BIOLASE board of directors (our “Board”) may be filled by an affirmative vote of two-thirds of the remaining members of our Board or at a meeting of the stockholders in the manner set forth in the second preceding sentence.

Dividend Rights. Subject to any preferential rights of any outstanding shares of our preferred stock to receive dividends before any dividends may be paid on our common stock, the holders of our common stock will be entitled to share ratably in any dividends that may be declared by our Board out of funds legally available for the payment of dividends. Our ability to pay dividends on our common stock will be limited by restrictions on our ability to pay dividends or make distributions to our stockholders and on the ability of our subsidiaries to pay dividends or make distributions to us, in each case, under the terms of our current, and any future, agreements governing our indebtedness.

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Other Rights. Each holder of our common stock is subject to, and may be adversely affected by, the rights of the holders of any series of preferred stock that our Board may designate and we may issue in the future. Holders of our common stock have no preemptive, conversion or other rights to subscribe for additional shares. Our common stock does not carry any redemption rights or any preemptive rights enabling a holder to subscribe for, or receive shares of, any class of our common stock or any other securities convertible into shares of any class of our common stock.

Liquidation Rights. Subject to any preferential rights of any outstanding shares of our preferred stock, in the event of our liquidation, dissolution or winding up, holders of our common stock are entitled to share ratably in the assets remaining after payment of liabilities and the liquidation preferences of any outstanding preferred stock. Standstill Agreements. Pursuant to (1) a standstill agreement with Jack W. Schuler, Renate Schuler and the Schuler Family Foundation (collectively, the “Schuler Parties”), dated November 10, 2015 (as amended on August 1, 2016 and November 9, 2017, the “Schuler Standstill Agreement”), and (2) a standstill agreement with Larry N. Feinberg, Oracle Partners, L.P., Oracle Institutional Partners, L.P., Oracle Ten Fund Master, L.P., Oracle Associates, LLC and Oracle Investment Management, Inc. (collectively, the “Oracle Parties”) dated November 10, 2015 (as amended on August 1, 2016 and November 9, 2017, the “Oracle Standstill Agreement” and, together with the Schuler Standstill Agreement, the “Standstill Agreements”), each of the Schuler Parties and the Oracle Parties agreed with respect to itself and its associates and affiliates (i) not to purchase or acquire any shares of our common stock if such a purchase would result in aggregate beneficial ownership by it and its affiliates and associates in excess of 41% of the issued and outstanding shares of our common stock and (ii) not to sell, transfer or otherwise convey shares of our common stock (or warrants or other rights to acquire shares of our common stock) to anyone who will immediately thereafter beneficially own shares in excess of 20% of the issued and outstanding shares of our common stock, as a result of such transfer and other transfers from third parties.

Preferred Stock

Our Charter authorizes our Board to provide for the issuance of shares of up to 1,000,000 shares of preferred stock in one or more series without further authorization from stockholders. Prior to issuance of shares of each series, our Board is required by the DGCL and our Charter to fix the designation, powers, preferences and rights of the shares of such series and the qualifications, limitations or restrictions thereof.

Warrants

As of August 15, 2022, 2,820,480 shares of our common stock were subject to outstanding warrants to purchase shares of our common stock. We may issue additional warrants to purchase shares of common stock or shares of preferred stock. We will issue warrants under one or more warrant agreements between us and a warrant agent we will name in the applicable prospectus supplement.

The prospectus supplement relating to any warrants we are offering will include specific terms relating to the offering. These terms will include some or all of the following:

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Rights

We may issue rights for the purchase of shares of our common stock, shares of our preferred stock or units (as described below). Each series of rights will be issued under a separate rights agreement which we will enter into with a bank or trust company, as rights agent, all as set forth in the applicable prospectus supplement. The rights agent will act solely as our agent in connection with the certificates relating to the rights and will not assume any obligation or relationship of agency or trust with any holders of rights certificates or beneficial owners of rights. We will file the rights agreement and the rights certificates, if any, relating to each series of rights with the SEC and incorporate them by reference as an exhibit to the registration statement of which this prospectus is a part on or before the time we issue a series of rights.

The applicable prospectus supplement will describe the terms of any rights we issue, including as applicable:

Rights will be exercisable for U.S. dollars only and will be in registered form only.

Units

We may issue securities in units, each consisting of two or more types of securities. For example, we might issue units consisting of a combination of common stock and warrants to purchase common stock. If we issue units, the prospectus supplement relating to the units will contain information with regard to each of the securities that is a component of the units. In addition, the prospectus supplement relating to the units will describe the terms of any units we issue, including as applicable:

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Anti-Takeover Provisions of Delaware Law and Our Governing Documents

Delaware Law

We are subject to Section 203 of the DGCL (“Section 203”). In general, Section 203 prohibits a publicly held Delaware corporation from engaging in “business combination” transactions with any “interested stockholder” for a period of three years following the time that the stockholder became an interested stockholder, unless:

A “business combination” is defined to include, in general and subject to exceptions, a merger of the corporation with the interested stockholder; a sale of 10% or more of the market value of the corporation’s consolidated assets to the interested stockholder; certain transactions that result in the issuance of the corporation’s stock to the interested stockholder; a transaction that has the effect of increasing the proportionate share of the corporation’s stock owned by the interested stockholder; and any receipt by the interested stockholder of loans, guarantees or other financial benefits provided by the corporation. An “interested stockholder” is defined to include, in general and subject to exceptions, a person that (1) owns 15% or more of the outstanding voting stock of the corporation or (2) is an “affiliate” or “associate” (as defined in Section 203) of the corporation and was the owner of 15% or more of the corporation’s outstanding voting stock at any time within the prior three year period.

A Delaware corporation may opt out of Section 203 with an express provision in its original certificate of incorporation or by an amendment to its certificate of incorporation or bylaws expressly electing not to be governed by Section 203 and approved by a majority of its outstanding voting shares. We have not opted out of Section 203. As a result, Section 203 could delay, deter or prevent a merger, change of control or other takeover of our Company that our stockholders might consider to be in their best interests, including transactions that might result in a premium being paid over the market price of our common stock and may also limit the price that investors are willing to pay in the future for our common stock.

Undesignated Preferred Stock

The ability to authorize undesignated preferred stock makes it possible for our Board to issue one or more series of preferred stock with voting or other rights or preferences. Thus, our Board could authorize the issuance

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of shares of preferred stock that have priority over our common stock with respect to dividends or rights upon liquidation or with terms and conditions that could have the effect of delaying, deferring or preventing a transaction or a change of control of our Company that might involve a premium price for holders of our common stock or otherwise be in their best interests.

Requirements for Advance Notification of Stockholder Nominations and Proposals

Our Bylaws establish advance notice procedures with respect to stockholder proposals and the nomination of candidates for election as directors, other than nominations made by or at the direction of the Board or a committee of the Board.

Stockholder Action by Written Consent; Special Meetings of Stockholders

Our stockholders may take action by written consent in lieu of a meeting as provided in our Bylaws. Our Bylaws provide that certain procedures, including notifying the Board and awaiting a record date, must be followed for stockholders to act by written consent. A special meeting of our stockholders may be called only by our Board, the Chairman of the Board, the Chief Executive Officer or the President. A special meeting may also be called at the request of stockholders holding a majority of the aggregate number of shares of capital stock of the Company issued and outstanding and entitled to vote at that meeting (subject to certain timeliness and content requirements of the demand).

Amendment of Charter and Bylaws

Our Charter may be amended by the affirmative vote of a majority of the aggregate number of shares of each class of our capital stock issued and outstanding after a resolution of our Board declaring the advisability of such amendment has been adopted in accordance with Delaware law. Our Bylaws may be amended by the affirmative vote of a majority of the aggregate number of shares of each class of our capital stock issued and outstanding (and entitled to vote on the subject matter) present in person or represented by proxy at a meeting of stockholders provided that notice thereof is stated in the written notice of the meeting. Our Bylaws may also be amended by a majority of the Board in accordance with Delaware law and our Charter, except that certain sections of our Bylaws (including but not limited to certain provisions regarding special meetings, voting, officers and approval of securities issuances) require either the affirmative vote of two-thirds of the persons then serving as directors on the Board or our stockholders.

Forum Selection

Unless the Board acting on behalf of the Company selects an alternative forum, the Court of Chancery of the State of Delaware (or, if the Court of Chancery does not have jurisdiction, another state court located within the State of Delaware or, if no court located within the State of Delaware has jurisdiction, the federal district court for the District of Delaware) shall be the sole and exclusive forum for (i) any derivative action or proceeding brought on behalf of the Company, (ii) any action asserting a claim of breach of a fiduciary duty owed by any of our directors, officers or other employees to the Company or our stockholders, (iii) any action asserting a claim against the Company or any of our directors, officers or other employees arising pursuant to any provision of the DGCL, our Charter or our Bylaws or (iv) any action asserting a claim against the Company or any of our directors, officers or other employees governed by the internal affairs doctrine of the State of Delaware.

Stock Exchange Listing

Our common stock trades on The Nasdaq Capital Market under the symbol “BIOL.”

Transfer Agent and Registrar

The transfer agent and registrar for our common stock is Computershare Trust Company, N.A.

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DESCRIPTION OF DEBT SECURITIES

This section describes the general terms and provisions of the debt securities that we may issue from time to time in the form of one or more series of debt securities. We may offer secured or unsecured debt securities which may be senior or subordinated and which may be convertible. The applicable prospectus supplement and/or other offering materials will describe the specific terms of the debt securities offered through that prospectus supplement as well as any general terms described in this section that will not apply to those debt securities. To the extent the applicable prospectus supplement or other offering materials relating to an offering of debt securities are inconsistent with this prospectus, the terms of that prospectus supplement or other offering materials will supersede the information in this prospectus. In this “Description of Debt Securities,” unless otherwise indicated, the “Company,” “we,” “our” and similar words refer to BIOLASE, Inc. and not any of its subsidiaries.

The debt securities will be issued under one or more indentures to be entered into between us and one or more trustees. References in this prospectus to the “indenture” and the “trustee” refer to the applicable indenture and the applicable trustee pursuant to which any particular series of debt securities is issued. The terms of any series of debt securities will be those specified in or pursuant to the applicable indenture and in the certificates evidencing that series of debt securities and those made part of the indenture by the Trust Indenture Act of 1939, as amended (the “Trust Indenture Act”). We may issue senior, subordinated and convertible debt securities under the same indenture.

The following summary of selected provisions of the indenture and the debt securities is not complete, and the summary of selected terms of a particular series of debt securities included in the applicable prospectus supplement also will not be complete. You should review the applicable form of indenture and the applicable form of certificate evidencing the debt securities, which forms have been or will be filed as exhibits to the registration statement of which this prospectus is a part or as exhibits to documents which have been or will be incorporated by reference in this prospectus. To obtain a copy of the indenture or the form of certificate for the debt securities, see “Where You Can Find More Information” in this prospectus. The following summary and the summary in any applicable prospectus supplement are qualified in their entirety by reference to all of the provisions of the indenture and the certificates evidencing the debt securities (including any amendments or supplements we may enter into from time to time which are permitted under the debt securities or any indenture), which provisions, including defined terms, are incorporated by reference in this prospectus.

Unless otherwise specified in a prospectus supplement, the debt securities will be direct unsecured obligations of the Company and will rank junior in right of payment to any of our secured indebtedness to the extent of the value of the assets securing such indebtedness, and will be structurally junior to all existing and future indebtedness incurred by our subsidiaries. Any debt securities designated as senior will rank equally with any of our other senior and unsubordinated debt. Any debt securities designated as subordinated will be subordinate and junior in right of payment to any senior indebtedness. There may be subordinated debt securities that are senior or junior to other series of subordinated debt securities.

The applicable prospectus supplement will set forth the terms of the debt securities or any series thereof, including, if applicable:

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This prospectus is part of a registration statement that provides that we may issue debt securities from time to time in one or more series under one or more indentures, in each case with the same or various maturities, at par or at a discount. Unless otherwise indicated in a prospectus supplement, we may issue additional debt securities of a particular series without the consent of the holders of the debt securities of such series outstanding at the time of the issuance. Any such additional debt securities, together with all other outstanding debt securities of that series, will constitute a single series of debt securities under the applicable indenture.

We intend to disclose any restrictive covenants for any issuance or series of debt securities in the applicable prospectus supplement.

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PLAN OF DISTRIBUTION

We may sell the securities offered through this prospectus in one or more of the following ways (or in any combination) from time to time:

If underwriters or dealers are used in the sale, the securities will be acquired by the underwriters or dealers for their own account and may be resold from time to time in one or more transactions, including:

The prospectus supplement will include the following information:

Sale Through Underwriters or Dealers

If underwriters are used in the sale of any securities, the underwriters will acquire the securities for their own account, including through underwriting, purchase, security lending or repurchase agreements with us. The underwriters may resell the securities from time to time in one or more transactions, including negotiated transactions. Underwriters may sell the securities in order to facilitate transactions in any of our other securities (described in this prospectus or otherwise), including other public or private transactions and short sales. Underwriters may offer securities to the public either through underwriting syndicates represented by one or more managing underwriters or directly by one or more firms acting as underwriters. Unless otherwise indicated in the prospectus supplement, the obligations of the underwriters to purchase the securities will be subject to certain conditions, and the underwriters will be obligated to purchase all the offered securities if they purchase any of them. The underwriters may change from time to time any initial public offering price and any discounts

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or concessions allowed or reallowed or paid to dealers. The prospectus supplement will include the names of the principal underwriters, the respective amount of securities underwritten, the nature of the obligation of the underwriters to take the securities and the nature of any material relationship between an underwriter and us.

If dealers are used in the sale of securities offered through this prospectus, we will sell the securities to them as principals. They may then resell those securities to the public at varying prices determined by the dealers at the time of resale. The prospectus supplement will include the names of the dealers and the terms of the transaction.

We may authorize underwriters, dealers or agents to solicit offers by certain purchasers to purchase our securities from us at the public offering price set forth in the prospectus supplement pursuant to delayed delivery contracts providing for payment and delivery on a specified date in the future. The contracts will be subject to those conditions set forth in the prospectus supplement, and the prospectus supplement will set forth any commissions paid for solicitation of these contracts.

Underwriters, dealers and agents may contract for or otherwise be entitled to indemnification by us against certain civil liabilities, including liabilities under the Securities Act, or to contribution with respect to payments made by the underwriters, dealers or agents, under agreements between us on one hand, and the underwriters, dealers and agents, on the other hand.

We may grant underwriters who participate in the distribution of our securities an option to purchase additional securities to cover over-allotments, if any, in connection with the distribution.

Underwriters, dealers or agents may receive compensation in the form of discounts, concessions or commissions from us or our purchasers, as their agents in connection with the sale of our securities. These underwriters, dealers or agents may be considered to be underwriters under the Securities Act. As a result, discounts, commissions or profits on resale received by the underwriters, dealers or agents may be treated as underwriting discounts and commissions. The prospectus supplement for any securities offered by us will identify any such underwriter, dealer or agent and describe any compensation received by them from us. Any public offering price and any discounts or concessions allowed or re-allowed or paid to dealers may be changed from time to time.

Underwriters, broker-dealers or agents who may become involved in the sale of our securities may engage in transactions with and perform other services for us for which they receive compensation.

Direct Sales and Sales Through Agents

We may sell the securities offered through this prospectus directly. In this case, no underwriters or agents would be involved. Such securities may also be sold through agents designated from time to time. The prospectus supplement will name any agent involved in the offer or sale of the offered securities and will describe any commissions payable to the agent by us. Unless otherwise indicated in the prospectus supplement, any agent will agree to use its reasonable best efforts to solicit purchases for the period of its appointment.

We may sell the securities directly to institutional investors or others who may be deemed to be underwriters within the meaning of the Securities Act, with respect to any sale of those securities.

At-the-Market Offerings

To the extent that we make sales through one or more underwriters or agents in at-the-market offerings, we will do so pursuant to the terms of a sales agency financing agreement or other at-the-market offering arrangement between us, on one hand, and the underwriters or agents, on the other hand. If we engage in at-the-market sales pursuant to any such agreement, we will issue and sell our securities through one or more

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underwriters or agents, which may act on an agency basis or a principal basis. During the term of any such agreement, we may sell securities on a daily basis in exchange transactions or otherwise as we agree with the underwriters or agents. Any such agreement will provide that any securities sold will be sold at prices related to the then prevailing market prices for our securities. Therefore, exact figures regarding proceeds that will be raised or commissions to be paid cannot be determined at this time. Pursuant to the terms of the agreement, we may agree to sell, and the relevant underwriters or agents may agree to solicit offers to purchase, blocks of our common stock or other securities. The terms of any such agreement will be set forth in more detail in the prospectus supplement.

Market Making, Stabilization and Other Transactions

In connection with an offering through underwriters, an underwriter may, to the extent permitted by applicable rules and regulations, purchase and sell securities in the open market. These transactions, to the extent permitted by applicable rules and regulations, may include short sales, stabilizing transactions and purchases to cover positions created by short sales. Short sales involve the sale by the underwriters of a greater number of securities than they are required to purchase in the offering. “Covered” short sales are short sales made in an amount not greater than the underwriters’ option to purchase additional securities from us in the offering, if any. If the underwriters have an over-allotment option to purchase additional securities from us, the underwriters may consider, among other things, the price of securities available for purchase in the open market as compared to the price at which they may purchase securities through the over-allotment option. “Naked” short sales, which may be prohibited or restricted by applicable rules and regulations, are any sales in excess of such option or where the underwriters do not have an over-allotment option. The underwriters must close out any naked short position by purchasing securities in the open market. A naked short position is more likely to be created if the underwriters are concerned that there may be downward pressure on the price of the securities in the open market after pricing that could adversely affect investors who purchase in the offering.

Accordingly, to cover these short positions or to otherwise stabilize or maintain the price of the securities, the underwriters may bid for or purchase securities in the open market and may impose penalty bids. If penalty bids are imposed, selling concessions allowed to syndicate members or other broker-dealers participating in the offering are reclaimed if securities previously distributed in the offering are repurchased, whether in connection with stabilization transactions or otherwise. The effect of these transactions may be to stabilize or maintain the market price of the securities at a level above that which might otherwise prevail in the open market. The imposition of a penalty bid may also affect the price of the securities to the extent that it discourages resale of the securities. The magnitude or effect of any stabilization or other transactions is uncertain.

Derivative Transactions and Hedging

We, the underwriters or other agents may engage in derivative transactions involving the securities. These derivatives may consist of short sale transactions and other hedging activities. The underwriters or agents may acquire a long or short position in the securities, hold or resell securities acquired and purchase options or futures on the securities and other derivative instruments with returns linked to or related to changes in the price of the securities. In order to facilitate these derivative transactions, we may enter into security lending or repurchase agreements with the underwriters or agents. The underwriters or agents may effect the derivative transactions through sales of the securities to the public, including short sales, or by lending the securities in order to facilitate short sale transactions by others. The underwriters or agents may also use the securities purchased or borrowed from us or others (or, in the case of derivatives, securities received from us in settlement of those derivatives) to directly or indirectly settle sales of the securities or close out any related open borrowings of the securities.

Trading Market and Listing of Securities

Any common stock sold or resold pursuant to a prospectus supplement will be listed on The Nasdaq Capital Market or on such other national securities exchange as our common stock may then be listed. The securities

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other than common stock may or may not be listed on a national securities exchange. It is possible that one or more underwriters may make a market in a class or series of securities, but the underwriters will not be obligated to do so and may discontinue any market making at any time without notice. We cannot give any assurance as to the liquidity of the trading market for any of the securities.

General Information

Agents, underwriters and dealers may be entitled, under agreements entered into with us, to indemnification by us against certain liabilities, including liabilities under the Securities Act.

SELECTED FINANCIAL INFORMATION

At the 2022 annual meeting of our stockholders (the “2022 Annual Meeting”), our stockholders approved an amendment to our certificate of incorporation to effect a reverse stock split of our common stock at a ratio ranging from one-for-two (1:2) to one-for-twenty-five (1:25), with the final ratio to be determined by our Board. Immediately after the 2022 Annual Meeting, our Board approved a one-for-twenty-five (1:25) reverse stock split of the outstanding shares of our common stock (the “Reverse Stock Split”). On April 28, 2022, we filed an amendment to our certificate of incorporation with the Secretary of State of the State of Delaware (the “Amendment”) to effect the Reverse Stock Split, effective as of 11:59 p.m. on April 28, 2022. The Amendment did not change the number of authorized shares of our common stock.

Net loss per share attributable to common stockholders, basic and diluted, has been derived from our audited financial statements contained in our Annual Report on Form 10-K for the years ended December 31, 2021, 2020 and 2019, except that the net loss per share attributable to common stockholders, basic and diluted, has been revised to reflect the new shares issued based on the reverse stock split ratio discussed above, as shown below.

The historical financial information set forth below may not be indicative of our future performance and should be read together with “Management’s Discussion and Analysis of Financial Condition and Results of Operations” and our historical financial statements and notes to those statements included in our Annual Report on Form 10-K for the year ended December 31, 2021, and any future filings or other reports we may file with the SEC.

As Reported

As Adjusted for the 1:25 Reverse Stock Split (unaudited)

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LEGAL MATTERS

Sidley Austin LLP will pass upon the validity of the securities being registered by the registration statement of which this prospectus is a part. Michael A. Gordon, a stockholder of the Company, is a partner at such firm. As of August 15, 2022, Mr. Gordon beneficially owned securities representing less than one percent of the outstanding common stock of the Company. Additional legal matters may be passed upon for us, or any underwriters, dealers or agents, by counsel that we will name in the applicable prospectus supplement.

EXPERTS

The consolidated financial statements and schedule of BIOLASE, Inc. as of December 31, 2021 and 2020 and for each of the three years in the period ended December 31, 2021 incorporated by reference into this prospectus have been so incorporated in reliance upon the report of BDO USA, LLP, an independent registered accounting firm, incorporated herein by reference, given upon the authority of said firm as experts in accounting and auditing.

INCORPORATION OF CERTAIN INFORMATION BY REFERENCE

The SEC allows us to incorporate by reference into this prospectus the information contained in other documents we file with the SEC, which means that we can disclose important information to you by referring you to those documents. Any statement contained in any document incorporated or deemed to be incorporated by reference in this prospectus shall be deemed to be modified or superseded, for purposes of this prospectus, to the extent that a statement contained in or omitted from this prospectus, or in any other subsequently filed document that also is or is deemed to be incorporated by reference in this prospectus, modifies or supersedes such statement. Any such statement so modified or superseded shall not be deemed, except as so modified or superseded, to constitute a part of this prospectus. We incorporate by reference the documents listed below which have been filed by us and any future filings we make with the SEC under Sections 13(a), 13(c), 14 or 15(d) of the Exchange Act (other than current reports furnished under Item 2.02 or Item 7.01 of Form 8-K and exhibits filed on such form that are related to such items unless such Form 8-K expressly provides to the contrary) subsequent to the date of the initial filing of the registration statement of which this prospectus forms a part until the offering of the securities covered by this prospectus is completed:

Upon written or oral request, we will provide without charge to each person, including any beneficial owner, to whom a copy of the prospectus is delivered a copy of the documents incorporated by reference in this prospectus (other than exhibits to such documents unless such exhibits are specifically incorporated by reference in this prospectus). You may request a copy of these filings, at no cost, by writing or telephoning us at the following address: BIOLASE, Inc., 27042 Towne Centre Drive, Suite 270, Lake Forest, California 92610, Attention: Investor Relations, telephone: (949) 361-1200.

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WHERE YOU CAN FIND MORE INFORMATION

We are subject to the informational requirements of the Exchange Act and in accordance therewith file reports, proxy statements and other information with the SEC. Our filings are available to the public over the Internet at the SEC’s website at www.sec.gov, as well as at our website at ir.biolase.com/sec-filings.

Information on any BIOLASE, Inc. website, any subsection, page or other subdivision of any BIOLASE, Inc. website, or any website linked to by content on any BIOLASE, Inc. website, is not part of this prospectus, and you should not rely on that information unless that information is also in this prospectus or incorporated by reference in this prospectus.

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331,000 Shares of Common Stock

Pre-Funded Warrants to Purchase 779,940 Shares of Common Stock

779,940 Shares of Common Stock Underlying the Pre-Funded Warrants

BIOLASE, Inc.

PROSPECTUS

MAXIM GROUP LLC

December 6, 2023