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                                                                EXHIBIT 5.1

                   POSTERNAK, BLANKSTEIN & LUND, L.L.P.
                            ATTORNEYS AT LAW
                            ----------------
                         100 Charles River Plaza
                       Boston, Massachusetts 02114

                                       June 7, 1997


National Dentex Corporation
111 Speen Street
Framingham, Massachusetts  01701

        Re:     Registration Statement on Form S-8

Ladies and Gentlemen:

        This opinion is rendered to you in connection with the preparation of
the Registration Statement on Form S-8 (the "Registration Statement") under
the Securities Act of 1933, as amended (the "Securities Act"), by National
Dentex Corporation, a Massachusetts corporation (the "Company"), relating to
an aggregate of 185,000 shares (the "Shares") of the Company's common stock,
$0.01 par value per share (the "Common Stock") issuable upon the exercise of
options granted under the Company's 1992 Long Term Incentive Plan (the "Plan").

        We have acted as counsel to the Company in connection with the prepara-
tion of the Registration Statement.  For purposes of this opinion, we have
examined the Articles of Organization and By-laws, each as amended and restated,
of the Company; the Plan, as amended to date; such records of the corporation
proceedings of the Company as we have deemed material; the Registration State-
ment and all exhibits thereto; and such other documents as we have deemed
necessary to enable us to render this opinion.

        We are attorneys admitted to practice in The Commonwealth of
Massachusetts.  We express no opinion concerning the laws of any jurisdiction
other than the laws of the United States of America and The Commonwealth
of Massachusetts.

        In rendering the opinion expressed herein, we assume that all steps
necessary to comply with the registration requirements of the Securities Act
and with applicable requirements of state law regulating the sale of securities
will be duly taken.


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POSTERNAK, BLANKSTEIN & LUND, L.L.P.

National Dentex Corporation
June 7, 1997
Page 2


        Based upon and subject to the foregoing, and having regard for such
legal considerations as we have deemed relevant, it is our opinion that the
Shares have been duly authorized for issuance by all necessary corporate
action and, when issued and delivered against payment of the consideration
therefor as set forth in the Plan, will be validly issued, fully paid and
nonassessable.

        This opinion is rendered solely for your benefit, and may not be
relied upon by any other party without our prior written consent.  We hereby
consent to the filing of this opinion as an exhibit to the Registration
Statement and to the reference to our name in the Registration Statement.

                                        Very truly yours,

                                        POSTERNAK, BLANKSTEIN & LUND, L.L.P.


                                        By: /s/ Donald H. Siegel, P.C.
                                           ---------------------------------
                                           A Partner Thereof