ADPI American Dental Partners, Inc. (MM)

CUSIP No. 025353103 13G Page 2 of 11 Pages


--------------------------------------------------------------------------------
 (1) NAMES OF REPORTING PERSONS

 Highbridge International LLC
--------------------------------------------------------------------------------
 (2) CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
 (see instructions)
 (a) [X]
 (b) [ ]
--------------------------------------------------------------------------------
 (3) SEC USE ONLY
--------------------------------------------------------------------------------
 (4) CITIZENSHIP OR PLACE OF ORGANIZATION

 Cayman Islands, British West Indies
--------------------------------------------------------------------------------
NUMBER OF (5) SOLE VOTING POWER
 0
SHARES -----------------------------------------------------------------

BENEFICIALLY (6) SHARED VOTING POWER
 115,500 shares of Common Stock
OWNED BY -----------------------------------------------------------------

EACH (7) SOLE DISPOSITIVE POWER
 0
REPORTING -----------------------------------------------------------------

PERSON WITH (8) SHARED DISPOSITIVE POWER
 115,500 shares of Common Stock
--------------------------------------------------------------------------------
 (9) AGGREGATE AMOUNT BENEFICIALLY OWNED
 BY EACH REPORTING PERSON
 115,500 shares of Common Stock
--------------------------------------------------------------------------------
 (10) CHECK BOX IF THE AGGREGATE AMOUNT
 IN ROW (9) EXCLUDES CERTAIN SHARES (see instructions)
 [ ]
--------------------------------------------------------------------------------
 (11) PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
 0.89%
--------------------------------------------------------------------------------
 (12) TYPE OF REPORTING PERSON (see instructions)
 OO
--------------------------------------------------------------------------------

CUSIP No. 025353103 13G Page 3 of 11 Pages


--------------------------------------------------------------------------------
 (1) NAMES OF REPORTING PERSONS

 Highbridge Capital Management, LLC
--------------------------------------------------------------------------------
 (2) CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
 (see instructions)
 (a) [X]
 (b) [ ]
--------------------------------------------------------------------------------
 (3) SEC USE ONLY
--------------------------------------------------------------------------------
 (4) CITIZENSHIP OR PLACE OF ORGANIZATION

 State of Delaware
--------------------------------------------------------------------------------
NUMBER OF (5) SOLE VOTING POWER
 0
SHARES -----------------------------------------------------------------

BENEFICIALLY (6) SHARED VOTING POWER
 115,500 shares of Common Stock
OWNED BY -----------------------------------------------------------------

EACH (7) SOLE DISPOSITIVE POWER
 0
REPORTING -----------------------------------------------------------------

PERSON WITH (8) SHARED DISPOSITIVE POWER
 115,500 shares of Common Stock
--------------------------------------------------------------------------------
 (9) AGGREGATE AMOUNT BENEFICIALLY OWNED
 BY EACH REPORTING PERSON
 115,500 shares of Common Stock
--------------------------------------------------------------------------------
 (10) CHECK BOX IF THE AGGREGATE AMOUNT
 IN ROW (9) EXCLUDES CERTAIN SHARES (see instructions)
 [ ]
--------------------------------------------------------------------------------
 (11) PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
 0.89%
--------------------------------------------------------------------------------
 (12) TYPE OF REPORTING PERSON (see instructions)
 OO
--------------------------------------------------------------------------------

CUSIP No. 025353103 13G Page 4 of 11 Pages


--------------------------------------------------------------------------------
 (1) NAMES OF REPORTING PERSONS

 Glenn Dubin
--------------------------------------------------------------------------------
 (2) CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
 (see instructions)
 (a) [X]
 (b) [ ]
--------------------------------------------------------------------------------
 (3) SEC USE ONLY
--------------------------------------------------------------------------------
 (4) CITIZENSHIP OR PLACE OF ORGANIZATION

 United States
--------------------------------------------------------------------------------
NUMBER OF (5) SOLE VOTING POWER
 0
SHARES -----------------------------------------------------------------

BENEFICIALLY (6) SHARED VOTING POWER
 115,500 shares of Common Stock
OWNED BY -----------------------------------------------------------------

EACH (7) SOLE DISPOSITIVE POWER
 0
REPORTING -----------------------------------------------------------------

PERSON WITH (8) SHARED DISPOSITIVE POWER
 115,500 shares of Common Stock
--------------------------------------------------------------------------------
 (9) AGGREGATE AMOUNT BENEFICIALLY OWNED
 BY EACH REPORTING PERSON
 115,500 shares of Common Stock
--------------------------------------------------------------------------------
 (10) CHECK BOX IF THE AGGREGATE AMOUNT
 IN ROW (9) EXCLUDES CERTAIN SHARES (see instructions)
 [ ]
--------------------------------------------------------------------------------
 (11) PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
 0.89%
--------------------------------------------------------------------------------
 (12) TYPE OF REPORTING PERSON (see instructions)
 IN
--------------------------------------------------------------------------------

CUSIP No. 025353103 13G Page 5 of 11 Pages


--------------------------------------------------------------------------------
 (1) NAMES OF REPORTING PERSONS

 Henry Swieca
--------------------------------------------------------------------------------
 (2) CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
 (see instructions)
 (a) [X]
 (b) [ ]
--------------------------------------------------------------------------------
 (3) SEC USE ONLY
--------------------------------------------------------------------------------
 (4) CITIZENSHIP OR PLACE OF ORGANIZATION

 United States
--------------------------------------------------------------------------------
NUMBER OF (5) SOLE VOTING POWER
 0
SHARES -----------------------------------------------------------------

BENEFICIALLY (6) SHARED VOTING POWER
 115,500 shares of Common Stock
OWNED BY -----------------------------------------------------------------

EACH (7) SOLE DISPOSITIVE POWER
 0
REPORTING -----------------------------------------------------------------

PERSON WITH (8) SHARED DISPOSITIVE POWER
 115,500 shares of Common Stock
--------------------------------------------------------------------------------
 (9) AGGREGATE AMOUNT BENEFICIALLY OWNED
 BY EACH REPORTING PERSON
 115,500 shares of Common Stock
--------------------------------------------------------------------------------
 (10) CHECK BOX IF THE AGGREGATE AMOUNT
 IN ROW (9) EXCLUDES CERTAIN SHARES (see instructions)
 [ ]
--------------------------------------------------------------------------------
 (11) PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
 0.89%
--------------------------------------------------------------------------------
 (12) TYPE OF REPORTING PERSON (see instructions)
 IN
--------------------------------------------------------------------------------

CUSIP No. 025353103 13G Page 6 of 11 Pages


Item 1.

(a) Name of Issuer

 American Dental Partners, Inc. (the "Company")

(b) Address of Issuer's Principal Executive Offices
 401 Edgewater Place, Suite 430
 Wakefield, Massachusetts 01880


Item 2(a). Name of Person Filing
Item 2(b). Address of Principal Business Office
Item 2(c). Citizenship


 HIGHBRIDGE INTERNATIONAL LLC
 c/o Harmonic Fund Services
 The Cayman Corporate Centre, 4th Floor
 27 Hospital Road
 Grand Cayman, Cayman Islands, British West Indies
 Citizenship: Cayman Islands, British West Indies

 HIGHBRIDGE CAPITAL MANAGEMENT, LLC
 9 West 57th Street, 27th Floor
 New York, New York 10019
 Citizenship: State of Delaware

 GLENN DUBIN
 c/o Highbridge Capital Management, LLC
 9 West 57th Street, 27th Floor
 New York, New York 10019
 Citizenship: United States

 HENRY SWIECA
 c/o Highbridge Capital Management, LLC
 9 West 57th Street, 27th Floor
 New York, New York 10019
 Citizenship: United States


Item 2(d) Title of Class of Securities

 Common Stock, $0.01 par value per share ("Common Stock")

Item 2(e) CUSIP Number

 025353103


Item 3. If this statement is filed pursuant to Rules 13d-1(b), or 13d-2(b) or
 (c), check whether the person filing is a:

(a) [ ] Broker or dealer registered under Section 15 of the Act (15 U.S.C. 78o).

(b) [ ] Bank as defined in Section 3(a)(6) of the Act (15 U.S.C. 78c).

CUSIP No. 025353103 13G Page 7 of 11 Pages


(c) [ ] Insurance company as defined in Section 3(a)(19) of the Act
 (15 U.S.C. 78c).

(d) [ ] Investment company registered under Section 8 of the Investment
 Company Act of 1940 (15 U.S.C. 80a-8).

(e) [ ] An investment adviser in accordance with Rule 13d-1(b)(1)(ii)(E);

(f) [ ] An employee benefit plan or endowment fund in accordance with
 Rule 13d-1(b)(1)(ii)(F);

(g) [ ] A parent holding company or control person in accordance with
 Rule 13d-1(b)(1)(ii)(G);

(h) [ ] A savings association as defined in Section 3(b) of the Federal
 Deposit Insurance Act (12 U.S.C. 1813);

(i) [ ] A church plan that is excluded from the definition of an investment
 company under Section 3(c)(14) of the Investment Company Act of 1940
 (15 U.S.C. 80a-3);

(j) [ ] Group, in accordance with Rule 13d-1(b)(1)(ii)(J).

If this statement is filed pursuant to Rule 13d-1(c), check this box. [X]


Item 4. Ownership

 Provide the following information regarding the aggregate number and
percentage of the class of securities of the issuer identified in Item 1.

 (a) Amount beneficially owned:

 As of April 1, 2009, (i) Highbridge International LLC beneficially owned
817,390 shares of Common Stock and (ii) each of Highbridge Capital Management,
LLC, Glenn Dubin and Henry Swieca may have been deemed the beneficial owner of
the 817,390 shares of Common Stock beneficially owned by Highbridge
International LLC.

 As of the date of this filing, (i) Highbridge International LLC
beneficially owns 115,500 shares of Common Stock and (ii) each of Highbridge
Capital Management, LLC, Glenn Dubin and Henry Swieca may be deemed the
beneficial owner of the 115,500 shares of Common Stock beneficially owned by
Highbridge International LLC.

 Highbridge Capital Management, LLC is the trading manager of Highbridge
International LLC. Glenn Dubin is the Chief Executive Officer of Highbridge
Capital Management, LLC. Henry Swieca is the Chief Investment Officer of
Highbridge Capital Management, LLC. The foregoing should not be construed in and
of itself as an admission by any Reporting Person as to beneficial ownership of
shares of Common Stock owned by another Reporting Person. In addition, each of
Highbridge Capital Management, LLC, Glenn Dubin and Henry Swieca disclaims
beneficial ownership of shares of Common Stock held by Highbridge International
LLC.

 (b) Percent of class:

CUSIP No. 025353103 13G Page 8 of 11 Pages


 The Company's annual report for the fiscal year ended December 31, 2008
filed on Form 10-K on March 16, 2009, indicates that as of March 4, 2009, there
were 12,948,575 shares of Common Stock outstanding. Therefore, based on the
Company's outstanding shares of Common Stock, (A) as of April 1, 2009 (i)
Highbridge International LLC may have been deemed to beneficially own 6.31% of
the outstanding shares of Common Stock of the Company and (ii) each of
Highbridge Capital Management, LLC, Glenn Dubin and Henry Swieca may have been
deemed to beneficially own 6.31% of the outstanding shares of Common Stock of
the Company and (B) as of the date of this filing (i) Highbridge International
LLC may be deemed to beneficially own 0.89% of the outstanding shares of Common
Stock of the Company and (ii) each of Highbridge Capital Management, LLC, Glenn
Dubin and Henry Swieca may be deemed to beneficially own 0.89% of the
outstanding shares of Common Stock of the Company. The foregoing should not be
construed in and of itself as an admission by any Reporting Person as to
beneficial ownership of shares of Common Stock owned by another Reporting
Person.

 (c) Number of shares as to which such person has:

 (i) Sole power to vote or to direct the vote

 0

 (ii) Shared power to vote or to direct the vote

 See Item 4(a)

 (iii) Sole power to dispose or to direct the disposition of

 0

 (iv) Shared power to dispose or to direct the disposition of

 See Item 4(a)


Item 5. Ownership of Five Percent or Less of a Class

 If this statement is being filed to report the fact that as of the date
hereof the reporting person has ceased to be the beneficial owner of more than
five percent of the class of securities, check the following: [X]


Item 6. Ownership of More than Five Percent on Behalf of Another Person

 Not applicable.


Item 7. Identification and Classification of the Subsidiary Which Acquired
 the Security Being Reported on by the Parent Holding Company or
 Control Person

 Not applicable.

CUSIP No. 025353103 13G Page 9 of 11 Pages


Item 8. Identification and Classification of Members of the Group

 See Exhibit I.


Item 9. Notice of Dissolution of Group

 Not applicable.


Item 10. Certification

 By signing below each of the undersigned certifies that, to the best of
its knowledge and belief, the securities referred to above were not acquired and
are not held for the purpose of or with the effect of changing or influencing
the control of the issuer of the securities and were not acquired and are not
held in connection with or as a participant in any transaction having that
purpose or effect.


Exhibits:

Exhibit I: Joint Filing Agreement, dated as of April 13, 2009, by and among
Highbridge International LLC, Highbridge Capital Management, LLC, Glenn Dubin
and Henry Swieca.

CUSIP No. 025353103 13G Page 10 of 11 Pages


 SIGNATURES

 After reasonable inquiry and to the best of its knowledge and belief,
each of the undersigned certifies that the information with respect to it set
forth in this statement is true, complete, and correct.

Dated: April 13, 2009

HIGHBRIDGE CAPITAL MANAGEMENT, LLC HIGHBRIDGE INTERNATIONAL LLC

 By: Highbridge Capital Management, LLC
 its Trading Manager

By: /s/ John Oliva
------------------------------
Name: John Oliva By: /s/ John Oliva
Title: Managing Director ----------------------------------
 Name: John Oliva
 Title: Managing Director



/s/ Henry Swieca /s/ Glenn Dubin
------------------------------ ----------------------------------
HENRY SWIECA GLENN DUBIN

CUSIP No. 025353103 13G Page 10 of 11 Pages


 EXHIBIT I

 JOINT FILING AGREEMENT

This will confirm the agreement by and among the undersigned that the Schedule
13G filed with the Securities and Exchange Commission on or about the date
hereof with respect to the beneficial ownership by the undersigned of the shares
of Common Stock, $0.01 par value per share, of American Dental Partners, Inc.,
is being filed, and all amendments thereto will be filed, on behalf of each of
the persons and entities named below in accordance with Rule 13d-1(k) under the
Securities Exchange Act of 1934, as amended. This Agreement may be executed in
two or more counterparts, each of which shall be deemed an original, but all of
which together shall constitute one and the same instrument.

Dated as of April 13, 2009


HIGHBRIDGE CAPITAL MANAGEMENT, LLC HIGHBRIDGE INTERNATIONAL LLC

 By: Highbridge Capital Management, LLC
 its Trading Manager

By: /s/ John Oliva
------------------------------
Name: John Oliva By: /s/ John Oliva
Title: Managing Director ----------------------------------
 Name: John Oliva
 Title: Managing Director



/s/ Henry Swieca /s/ Glenn Dubin
------------------------------ ----------------------------------
HENRY SWIECA GLENN DUBIN