<PAGE>


                            AMENDMENT AGREEMENT NO. 1
                                       TO
                      AMENDED AND RESTATED CREDIT AGREEMENT

     AMENDMENT AGREEMENT NO. 1 dated July 30, 1999 (this "AGREEMENT"), to
AMENDED AND RESTATED CREDIT AGREEMENT dated as of June 15, 1999 (the "CREDIT
AGREEMENT"), among GENTLE DENTAL SERVICE CORPORATION, a Washington corporation
("DENTAL SERVICE"), GENTLE DENTAL MANAGEMENT, INC., a Delaware corporation
("DENTAL MANAGEMENT") and DENTAL CARE ALLIANCE, INC., a Delaware corporation
("DCA"; DCA, Dental Service and Dental Management, each a "BORROWER" and
collectively, the "BORROWERS"), the Guarantors named therein, the financial
institutions from time to time party thereto (collectively, the "LENDERS"),
UNION BANK OF CALIFORNIA, N.A., as administrative agent for the Lenders (in such
capacity, the "ADMINISTRATIVE AGENT") and THE CHASE MANHATTAN BANK, as
syndication agent for the Lenders (in such capacity, the "SYNDICATION AGENT").


     WHEREAS, the Borrowers, the Guarantors and the Lenders desire to increase
the Total Revolving Credit Commitment (as defined in the Credit Agreement) from
$70,000,000 to $75,000,000;

     WHEREAS, First National Bank ("FNB") desires to become a Lender under the
Credit Agreement and to have a Revolving Credit Commitment of $5,000,000;

     NOW, THEREFORE, the Borrowers, the Guarantors, the Lenders, the
Administrative Agent and the Syndication Agent hereby agree as follows:

     SECTION 1 CAPITALIZED TERMS. Capitalized terms used herein and not defined
shall have the respective meanings assigned to such terms in the Credit
Agreement.

     SECTION 2 AMENDMENTS TO THE CREDIT AGREEMENT. Upon the fulfillment of the
conditions set forth in Section 5 hereof the Credit Agreement is hereby amended
as follows:

           2.1 The amount "$70,000,000" as it appears in the preamble of the
     Credit Agreement is hereby deleted and the amount "$75,000,000" is
     hereby substituted therefor.

           2.2 Schedule 2.01(a) to the Credit Agreement is hereby amended in
     its entirety as set forth on Schedule 2.01(a) attached hereto.

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           2.3 Schedule 2.02 to the Credit Agreement is hereby amended in its
     entirety as set forth on Schedule 2.02 attached hereto.

           2.4 Schedule 2.03 to the Credit Agreement is hereby amended in its
     entirety as set forth on Schedule 2.03 attached hereto.

     SECTION 3 ADDITIONAL LENDER. By its signature below FNB shall become a
party to and be bound by the provisions of the Credit Agreement as a Lender
and shall have the rights and obligations of a Lender hereunder, thereunder
and under the other Loan Documents.

     SECTION 4 CONFIRMATION OF LOAN DOCUMENTS. Each Loan Party, by its
execution and delivery of this Agreement, irrevocably and unconditionally
ratifies and confirms in favor of the Administrative Agent that it consents
to the terms and conditions of the Credit Agreement as it has been amended by
this Agreement and that notwithstanding this Agreement, each Loan Document to
which such Loan Party is a party shall continue in full force and effect in
accordance with its terms, as it has been amended by this Agreement, and is
and shall continue to be applicable to all of the Obligations.

     SECTION 5 CONDITIONS PRECEDENT. This Agreement shall become effective
upon the execution and delivery of counterparts hereof by all parties hereto
to the Administrative Agent and the fulfillment of the following conditions:

           5.1 All legal matters in connection with this Agreement shall be
     satisfactory to the Administrative Agent, the Lenders and their
     respective counsel in their sole discretion.

           5.2 The Administrative Agent shall have received a $3,000
     processing and recordation fee from the Borrowers.

           5.3 FNB shall have received its Revolving Credit Note duly
     executed by the Borrowers, payable to its order and otherwise complying
     with the provisions of Section 2.04 of the Credit Agreement.

           5.4 The Administrative Agent shall have received a certificate
     signed by a Financial Officer of each Borrower and Guarantor that (i)
     both before and after giving effect to the transactions contemplated
     herein all representations and warranties contained in this Agreement or
     otherwise made in writing to the Administrative Agent in connection
     herewith shall be true and correct in all material respects on and as of
     the date hereof (except insofar as such representations and warranties
     relate expressly to an earlier date) and (ii) both before and after
     giving effect to the transactions contemplated herein there exists no
     unwaived Default or Event of Default.

                                       2

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           5.5 The Administrative Agent shall have received a favorable
     opinion of counsel in form and substance satisfactory to the
     Administrative Agent and its counsel.

           5.6 Messrs. Kaye, Scholer, Fierman, Hays & Handler, LLP, counsel
     to the Agent, shall have received payment in full for all legal fees
     charged, and all costs and expenses incurred, by such counsel through
     the date hereof and all legal fees charged, and all costs and expenses
     incurred, by such counsel in connection with the transactions
     contemplated under this Agreement and the other Loan Documents and
     instruments in connection herewith and therewith.

           5.7 The Administrative Agent shall have received such other
     documents as the Lenders or the Administrative Agent or its counsel
     shall reasonably deem necessary.

     SECTION 6 MISCELLANEOUS.

           6.1      Each Borrower and each Guarantor reaffirms and restates
     the representations and warranties set forth in Article IV of the Credit
     Agreement, as amended by this Agreement and after giving effect to the
     transactions contemplated herein, and all such representations and
     warranties shall be true and correct in all material respects on and as
     of the date hereof (except insofar as such representations and
     warranties relate expressly to an earlier date). Each Loan Party
     represents and warrants (which representations and warranties shall
     survive the execution and delivery hereof) to the Agent that:

           (a) It has the corporate power and authority to execute, deliver
     and carry out the terms and provisions of this Agreement and the
     transactions contemplated hereby and has taken or caused to be taken all
     necessary corporate action to authorize the execution, delivery and
     performance of this Agreement and the transactions contemplated hereby;

           (b) No consent of any other person (including, without limitation,
     shareholders or creditors of any Loan Party), and no action of, or
     filing with any governmental or public body or authority is required to
     authorize, or is otherwise required in connection with the execution,
     delivery and performance of this Agreement;

           (c) This Agreement has been duly executed and delivered on behalf
     of each Loan Party by a duly authorized officer, and constitutes a
     legal, valid and binding obligation of each Loan Party enforceable in
     accordance with its terms, subject to bankruptcy, reorganization,
     insolvency, moratorium and other similar laws affecting the enforcement
     of creditors' rights generally and the exercise of judicial discretion
     in accordance with general principles of equity; and


                                        3


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          (d) The execution, delivery and performance of this Agreement will
     not violate any law, statute or regulation, or any order or decree of
     any court or governmental instrumentality, or conflict with, or result
     in the breach of, or constitute a default under any contractual
     obligation of any Loan Party.

           6.2 Except, as herein expressly amended, the Credit Agreement is
     ratified and confirmed in all respects and shall remain in full force
     and effect in accordance with its terms.

           6.3 The Acknowledgment, Waiver and Consent (the "WAIVER AND
     CONSENT") dated as of July 23, 1999, among the Administrative Agent, the
     Lenders, the Borrower and the Guarantors is hereby ratified and
     confirmed in all respects and shall remain in full force and effect in
     accordance with its terms. By its signature below FNB shall become a
     party to and be bound by the terms and provisions of the Waiver and
     Consent.

           6.4 All references to the Credit Agreement contained in the Credit
     Agreement and the other Loan Documents and the other documents and
     instruments delivered pursuant to or in connection therewith shall mean
     the Credit Agreement, as amended hereby and as may in the future be
     amended, restated, supplemented or modified from time to time.

           6.5 This Agreement may be executed by the parties hereto
     individually or in combination, in one or more counterparts, each of
     which shall be an original and all of which shall constitute one and the
     same agreement.

           6.6 Delivery of an executed counterpart of a signature page to
     this Agreement by telecopier shall be effective as delivery of a
     manually executed counterpart of this Agreement.

           6.7 THIS AGREEMENT SHALL BE GOVERNED BY, AND CONSTRUED AND
     INTERPRETED IN ACCORDANCE WITH, THE LAWS OF THE STATE OF CALIFORNIA
     WITHOUT REGARD TO CHOICE OR CONFLICT OF LAW PRINCIPLES THEREOF.

           6.8 The parties hereto shall, at any time and from time to time
     following the execution of this Agreement, execute and deliver all such
     further instruments and take all such further actions as may be
     reasonably necessary or appropriate in order to carry out the provisions
     of this Agreement.

               [REMAINDER OF THIS PAGE INTENTIONALLY LEFT BLANK.]


                                        4

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                  IN WITNESS WHEREOF, the Borrowers, Guarantors, the
Administrative Agent, the Syndication Agent and the Lenders have caused this
Agreement to be duly executed by their respective authorized officers as of the
day and year first above written.


                            GENTLE DENTAL SERVICE CORPORATION,
                            as a Borrower


                            By: /s/ Michael T. Fiore
                               ---------------------------------
                                     Name:  Michael T. Fiore
                                     Title:  President

                            GENTLE DENTAL MANAGEMENT, INC.,
                            as a Borrower


                            By: /s/ Michael T. Fiore
                               ---------------------------------
                                     Name:  Michael T. Fiore
                                     Title:  President

                            DENTAL CARE ALLIANCE, INC.,
                            as a Borrower


                            By: /s/ David P. Nichols
                               ---------------------------------
                                     Name: David P. Nichols
                                     Title: Chief Financial Officer

                            GMS HAWAII ACQUISITION COMPANY,
                            as a Guarantor


                            By: /s/ Michael T. Fiore
                               ---------------------------------
                                     Name:  Michael T. Fiore
                                     Title:  President

                            GMS DENTAL GROUP MANAGEMENT OF HAWAII, INC.,
                            as a Guarantor


                            By: /s/ Michael T. Fiore
                               ---------------------------------
                                     Name:  Michael T. Fiore
                                     Title:  President


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                            GMS DENTAL GROUP MANAGEMENT
                            OF SOUTHERN CALIFORNIA, INC.,
                            as a Guarantor


                            By: /s/ Michael T. Fiore
                               ---------------------------------
                                     Name:  Michael T. Fiore
                                     Title:  President


                            GMS DENTAL GROUP MANAGEMENT OF
                            THE MOUNTAIN STATES, INC.,
                            as a Guarantor


                            By: /s/ Michael T. Fiore
                               ---------------------------------
                                     Name:  Michael T. Fiore
                                     Title:  President

                            GENTLE DENTAL MANAGEMENT - PACIFIC
                            NORTHWEST, INC., as a Guarantor


                            By: /s/ Michael T. Fiore
                               ---------------------------------
                                     Name:  Michael T. Fiore
                                     Title:  President

                            GENTLE DENTAL OF IRVINE,
                            as a  Guarantor


                            By: /s/ Michael T. Fiore
                               ---------------------------------
                                     Name:  Michael T. Fiore
                                     Title:  President

                            GDSC OF PIEDMONT, INC.,
                            as a Guarantor


                            By: /s/ Michael T. Fiore
                               ---------------------------------
                                     Name:  Michael T. Fiore
                                     Title:  President


                            GENTLE DENTAL LEGACY, INC.,
<PAGE>
                            as a Guarantor


                            By: /s/ Michael T. Fiore
                               ---------------------------------
                                     Name:  Michael T. Fiore
                                     Title:  President


                            DENTAL CARE ALLIANCE OF FLORIDA, INC.,
                            as a Guarantor


                            By: /s/ David P. Nichols
                               ---------------------------------
                                     Name: David P. Nichols
                                     Title: Chief Financial Officer


                            DENTAL CARE ALLIANCE OF MICHIGAN, INC.,
                            as a Guarantor


                            By: /s/ David P. Nichols
                               ---------------------------------
                                     Name: David P. Nichols
                                     Title: Chief Financial Officer


                            DENTAL CARE ALLIANCE OF GEORGIA, INC.,
                            as a Guarantor


                            By: /s/ David P. Nichols
                               ---------------------------------
                                     Name: David P. Nichols
                                     Title: Chief Financial Officer


                            DENTAL CARE ALLIANCE OF INDIANA, INC.,
                            as a Guarantor


                            By: /s/ David P. Nichols
                               ---------------------------------
                                     Name: David P. Nichols
                                     Title: Chief Financial Officer



                            DENTAL ONE ASSOCIATES, INC.,
                            as a Guarantor


<PAGE>



                            By: /s/ David P. Nichols
                               ---------------------------------
                                     Name: David P. Nichols
                                     Title: Chief Financial Officer


                            DENTAL CARE ALLIANCE OF PENNSYLVANIA, INC.,
                            as a Guarantor


                            By: /s/ David P. Nichols
                               ---------------------------------
                                     Name: David P. Nichols
                                     Title: Chief Financial Officer


                            SERRA PARK DENTAL SERVICES, INCORPORATED,
                            as a Guarantor


                            By: /s/ Michael T. Fiore
                               ---------------------------------
                                     Name:  Michael T. Fiore
                                     Title:  President

                            SPDS DMI, INCORPORATED,
                            as a Guarantor


                            By: /s/ Michael T. Fiore
                               ---------------------------------
                                     Name:  Michael T. Fiore
                                     Title:  President

                            UNION BANK OF CALIFORNIA, N.A.,
                            as Administrative Agent and as a Lender


                            By: /s/ Nancy Perkins
                               ---------------------------------
                                     Name: Nancy Perkins
                                     Title: Vice President


                            THE CHASE MANHATTAN BANK, as Syndication Agent
                            and as a Lender


                            By: /s/ Eric Groberg
                               ---------------------------------


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                                     Name: Eric Groberg
                                     Title:  Vice President

                            U.S. BANK NATIONAL ASSOCIATION,
                            as a Lender


                            By: /s/ Brian O'Neill
                               ---------------------------------
                                     Name: Brian O'Neill
                                     Title: V.P.

                            FLEET CAPITAL CORPORATION,
                            as a Lender


                            By: /s/ James J. Karnowski
                               ---------------------------------
                                     Name: James J. Karnowski
                                     Title: Vice President

                            BANK OF AMERICA, N.A. (successor by merger to
                            NationsBank, N. A.), as a Lender


                            By: /s/ Ruth Z. Edwards
                               ---------------------------------
                                     Name: Ruth Z. Edwards
                                     Title: Vice President

                            FIRST NATIONAL BANK, as a Lender


                            By: /s/ Roger Smock
                               ---------------------------------
                                     Name: Roger Smock
                                     Title: Chief Lending Officer


<PAGE>

Solely as to Sections 4 and 6:  INTERDENT, INC., as a Guarantor


                            By: /s/ Michael T. Fiore
                               ---------------------------------
                                     Name: Michael T. Fiore
                                     Title: