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                                                                   EXHIBIT 4.1


                  CONSENT NO. 1, dated as of November 13, 1998 (this "Consent"),
under the Second Amended and Restated Credit Agreement, dated as of April 25,
1997 (the "Credit Agreement"), among Sybron International Corporation, a
Wisconsin corporation (the "Parent"), Ormco Corporation, a Delaware corporation
("Ormco"), Kerr Corporation, a Delaware corporation ("Kerr"), Nalge Nunc
International Corporation, a Delaware corporation ("NNI"), Erie Scientific
Company, a Delaware corporation ("Erie"), Barnstead Thermolyne Corporation, a
Delaware corporation ("Barnstead"; Ormco, Kerr, NNI, Erie and Barnstead are
collectively referred to herein as the "Subsidiary Borrowers"), the several
banks and other financial institutions from time to time parties thereto (the
"Lenders"), Chase Securities, Inc., as Arranger, and The Chase Manhattan Bank, a
New York banking corporation, as administrative agent for the Lenders thereunder
(in such capacity, the "Administrative Agent").


                              W I T N E S S E T H:


                  WHEREAS, pursuant to the Credit Agreement, the Lenders have
agreed to make, and have made, certain loans and other extensions of credit to
the Parent and the Subsidiary Borrowers; and

                  WHEREAS, the Parent and the Subsidiary Borrowers have
requested that the Administrative Agent and the Lenders consent to matters
regarding certain provisions of the Credit Agreement; and

                  WHEREAS, the Administrative Agent and the Lenders are willing
to agree to such request on the terms and conditions contained herein.

                  NOW, THEREFORE, in consideration of the premises and the
mutual agreements contained herein, and for other good and valuable
consideration, the receipt and sufficiency of which are hereby acknowledged, the
parties hereto hereby agree as follows:

          I.      Defined Terms.  Terms defined in the Credit Agreement and used
herein shall have the meanings given to them in the Credit Agreement.

          II.     Consent. (a) The Administrative Agent and the Lenders hereby 
consent, notwithstanding the provisions of Section 7.6 of the Credit Agreement,
to the proposed sale of Nalge Process Technologies Group, Inc. ("NPT") as
described on Annex 1 hereto, and that the Net Proceeds of such sale of NPT shall
not be counted towards the $25,000,000 limit on asset sales and other
dispositions set forth in subsection 7.6(e), provided that 100% of the Net
Proceeds of the sale of NPT shall be applied to the prepayment of the Term Loans
as provided in paragraph (b) below, and provided, further that no Default or
Event of Default shall have occurred and be continuing at the time of such sale.
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          (b) Notwithstanding the provisions of Section 2.15(c) of the Credit
Agreement, so long as no Default or Event of Default has occurred and is
continuing or would result herefrom, the Company shall be entitled to apply up
to $60,000,000 of the Net Proceeds of the sale of NPT to the outstanding
installments of principal with respect to Term Loans scheduled to be paid
pursuant to subsection 2.12 immediately succeeding the date of such prepayment,
provided that 100% of any Net Proceeds therefrom in excess of $60,000,000 shall
be applied as set forth in Section 2.15(c).

          III.    Conditions to Effectiveness. This Consent shall become 
effective on the date (the "Consent Effective Date") on which (i) the Parent,
the Subsidiary Borrowers, the Administrative Agent and the Majority Lenders
shall have executed and delivered to the Administrative Agent this Consent and
(ii) the Parent shall have paid to the Administrative Agent and the Lenders
consenting hereto the fees specified elsewhere with respect to this Consent.

          IV.     General

          1.      Representation and Warranties. To induce the Administrative 
Agent and the Lenders parties hereto to grant this Consent, the Parent and the
Subsidiary Borrowers hereby represent and warrant to the Administrative Agent
and all of the Lenders as of the Consent Effective Date that the representations
and warranties made by the Loan Parties in the Loan Documents are true and
correct in all material respects on and as of the Consent Effective Date, before
and after giving effect to the effectiveness of this Consent, as if made on and
as of the Consent Effective Date and no Default or Event of Default shall have
occurred and be continuing.

          2.      Payment of Expenses. The Parent and the Subsidiary Borrowers 
agree to pay or reimburse the Administrative Agent for all of its out-of-pocket
costs and reasonable expenses incurred in connection with this Consent, any
other documents prepared in connection herewith and the transactions
contemplated hereby, including, without limitation, the reasonable fees and
disbursements of counsel to the Administrative Agent.

          3.      Continuing Effect of Credit Agreement.  Except for this 
Consent, the Credit Agreement is and shall remain in full force and effect. This
Consent shall be a Loan Document.

          4.      GOVERNING LAW. THIS CONSENT AND THE RIGHTS AND OBLIGATIONS OF 
THE PARTIES HERETO SHALL BE GOVERNED BY, AND CONSTRUED AND INTERPRETED IN
ACCORDANCE WITH, THE LAWS OF THE STATE OF NEW YORK.

          5.      Counterparts. This Consent may be executed by one or more of 
the parties to this Agreement on any number of separate counterparts, and all of
said counterparts taken together shall be deemed to constitute one and the same
instrument. This Consent may be delivered by facsimile transmission of the
relevant signature pages hereof.


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          IN WITNESS WHEREOF, the parties hereto have caused this Consent to be
duly executed and delivered by their respective proper and duly authorized
officers as of the day and year first above written.


                                               SYBRON INTERNATIONAL CORPORATION

                                               By:  s/ John Buono
                                                  ------------------------------
                                               Title:  Assistant Treasurer


                                               ORMCO CORPORATION

                                               By:  s/ John Buono
                                                  ------------------------------
                                               Title:  Assistant Treasurer


                                               KERR CORPORATION

                                               By:  s/ John Buono
                                                  ------------------------------
                                               Title:  Assistant Treasurer


                                               NALGE NUNC INTERNATIONAL
                                                CORPORATION

                                               By:  s/ John Buono
                                                  ------------------------------
                                               Title:  Assistant Treasurer


                                               ERIE SCIENTIFIC COMPANY

                                               By:  s/ John Buono
                                                  ------------------------------
                                               Title:  Assistant Treasurer