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                                                                   EXHIBIT 10(b)


                                AMENDMENT NO. 4
                                      TO
                        AMERICAN DENTAL PARTNERS, INC.
                  AMENDED AND RESTATED 1996 STOCK OPTION PLAN
                  -------------------------------------------


     The American Dental Partners, Inc. Amended and Restated 1996 Stock Option
Plan, as previously amended by Amendment No. 1 dated February 27, 1998,
Amendment No. 2 dated November 6, 1998, and Amendment No. 3 dated February 26,
1999 (collectively, the "Plan"), is hereby amended pursuant to the following
provisions:

     1.   Definitions
          -----------

     All capitalized terms used in this amendment which are not otherwise
defined herein shall have the respective meanings given such terms in the Plan.

     2.   Option Price
          ------------

     Section 7 of the Plan is hereby deleted from the Plan in its entirety and
replaced with the following:

     7.   Option Price.
          ------------

          The exercise price per share of Common Stock issuable upon exercise of
     an option shall be determined by the Board at the time of grant and set
     forth in the applicable Agreement; provided that such exercise price shall
     not be less than the fair market value per share on the date the option is
     granted. For purposes of the Plan, the fair market value of the Common
     Stock shall mean, as of any given date, whichever of the following is
     applicable: (i) the last reported sale price on the New York Stock Exchange
     ("NYSE") on that date, or, if none, the last reported sale price on the
     NYSE on the most recent previous trading day; (ii) the last reported sale
     price on the NASDAQ National Market System ("NASDAQ") on that date, or, if
     none, the last reported sale price on the NASDAQ on the most recent
     previous trading day; (iii) the mean between the high and low bid and ask
     prices, as reported by the National Association of Securities Dealers, Inc.
     ("NASD") on that date, or, if none, the mean between the high and low bid
     and ask prices, as reported by the NASD on the most recent previous trading
     day; or (iv) the last reported sale price on any other stock exchange on
     which the Common Stock is listed on that date, or, if none, the last
     reported sale price on any other stock exchange on which the Common Stock
     is listed on the most recent previous trading day, whichever is applicable;
     provided that if none of the foregoing is applicable, then the fair market
     value of the Common Stock shall be the value determined by the Board, in
     its sole discretion.

     3.   Effective Date; Construction
          ----------------------------

          The effective date of this amendment is July 1, 1999, and this
amendment shall be deemed to be a part of the Plan as of such date; provided
that this amendment shall not modify the exercise price of any options granted
under the Plan prior to such date.  In the event of any inconsistencies between
the provisions of the Plan and this amendment, the provisions of this amendment
shall control.  Except as modified by this amendment, the Plan shall continue in
full force and effect without change.

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