<PAGE>   1

                                                         File No. 333-__________

     As filed with the Securities and Exchange Commission on April 17, 1998

================================================================================
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

                             -----------------------

                                    FORM S-8
                             REGISTRATION STATEMENT
                                      Under
                           THE SECURITIES ACT OF 1933

                             -----------------------

                           NATIONAL DENTEX CORPORATION
             (Exact name of registrant as specified in its charter)


        MASSACHUSETTS                                         04-2762050
(State or other jurisdiction of                            (I.R.S. Employer
incorporation or organization)                            Identification No.)
               

               526 BOSTON POST ROAD, WAYLAND, MASSACHUSETTS 01778
                    (Address of Principal Executive Offices)

                          1992 LONG TERM INCENTIVE PLAN
                            (Full title of the Plan)


                             RICHARD F. BECKER, JR.
                Vice President - Finance and Assistant Treasurer
                           National Dentex Corporation
                              526 Boston Post Road
                          Wayland, Massachusetts 01778
                    (Name and address of agent for services)
                                 (508) 358-4422
                     (Telephone number, including area code,
                              of agent for service)


                                    Copy to:

                            MICHAEL L. ANDRESINO, ESQ
                      Posternak, Blankstein & Lund, L.L.P.
                             100 Charles River Plaza
                              Boston, MA 02114-2723
                                 (617) 973-6100

                             -----------------------



<PAGE>   2

<TABLE>
<CAPTION>

================================================================================

                         Calculation of Registration Fee

--------------------------------------------------------------------------------
                                     Proposed      Proposed
                                     Maximum        Maximum
   Title of                          Offering      Aggregate       Amount of
Securities to     Amount to be        Price        Offering       Registration
be Registered     Registered(1)    Per Share(2)    Price(3)           Fee
-------------     ------------     -----------     ---------      ------------
<C>               <C>                 <C>         <C>               <C>      
Common Stock
$0.01 par value   150,000 shares      $25.75      $3,862,500        $1,139.44

</TABLE>



--------------------------------------------------------------------------------

(1)  Plus such additional number of shares as may be required pursuant to the
     1992 Long Term Incentive Plan in the event of a stock dividend, stock
     split, split-up, recapitalization or other similar event.

(2)  This estimate is made pursuant to Rule 457(c) and (h) under the Securities
     Act of 1933, as amended (the "Securities Act"), solely for purposes of
     determining the registration fee and is based upon the market value of
     outstanding shares of the Company's common stock on April 14, 1998,
     utilizing the average of the high ($26.50) and low ($25.00) sale prices
     reported on the NASDAQ National Market System for that date.

(3)  This estimate is made pursuant to Rule 457(h) under the Securities Act
     solely for the purposes of determining the registration fee and is based
     upon the maximum price at which any outstanding options under such plan may
     be exercised.

================================================================================



<PAGE>   3

                                     PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

Item 3.   INCORPORATION OF CERTAIN DOCUMENTS BY REFERENCE.

     National Dentex Corporation (the "Company") hereby incorporates by
reference the following documents which have previously been filed with the
Securities and Exchange Commission:

     a)   The Company's Annual Report on Form 10-K for the fiscal year ended
          December 31, 1997; and

     b)   The description of the Company's Common Stock, $0.01 par value,
          contained in the Company's registration statement on Form 8-A (File
          No. 0-23092) under the Securities Exchange Act of 1934, as amended
          (the "Exchange Act").

     In addition, all documents subsequently filed with the Securities and
Exchange Commission by the Company pursuant to Sections 13 (a) and 13 (c),
Section 14 and Section 15 (d) of the Exchange Act prior to the filing of a
post-effective amendment which indicates that all securities offered hereunder
have been sold or which deregisters all securities then remaining unsold, shall
be deemed to be incorporated by reference in this registration statement and to
be a part hereof from the date of filing of such documents.

Item 4.   DESCRIPTION OF SECURITIES.

     Not Applicable.

Item 5.  INTERESTS OF NAMED EXPERTS AND COUNSEL.

     The validity of the shares to be offered hereby will be passed upon for the
Company by Posternak, Blankstein & Lund, L.L.P., Boston, Massachusetts.

     The consolidated financial statements of the Company incorporated by
reference herein from the Company's Annual Report on Form 10-K for the fiscal
year ended December 31, 1997 have been incorporated by reference in reliance on
the report of Arthur Andersen LLP, independent public accountants, given on the
authority of such firm as experts in accounting and auditing in giving said
reports.




<PAGE>   4

Item 6.   INDEMNIFICATION OF DIRECTORS AND OFFICERS.

     Section 67 of the Business Corporation Law of the Commonwealth of
Massachusetts provides that indemnification of directors, officers, employees or
other agents may be provided by a corporation. Section 13 (b) (1-1/2) of the
Business Corporation Law of the Commonwealth of Massachusetts provides that the
Articles of Organization may contain a provision eliminating or limiting the
personal liability of a director to the corporation or its stockholders for
monetary damages for breach of fiduciary duty as a director provided that such
provision shall not eliminate or limit the liability of a director (i) for any
breach of the director's duty of loyalty to the corporation or its stockholders,
(ii) for acts or omissions not in good faith or which involve intentional
misconduct or a knowing violation of law, (iii) under Sections 61 or 62 of the
Massachusetts Business Corporation Law, or (iv) for any transaction from which
the director derived an improper personal benefit.

     Article Six of the Company's Articles of Organization, as amended,
eliminates the personal liability of each member of the Company's Board of
Directors to the Company or its stockholders for monetary damages for breach of
fiduciary duty as a director. However, the liability of a director is not
eliminated (i) for any breach of such director's duty of loyalty to the Company
or its stockholders, (ii) for acts or omissions not in good faith or which
involve intentional misconduct or a knowing violation of law, (iii) under
Section 61 or 62 of the Massachusetts Business Corporation Law, or any
amendatory or successor provision thereto, or (iv) for any transaction from
which such director derived an improper personal benefit. This provision is
intended to afford directors additional protection, and limit their potential
liability, from suits alleging a breach of duty of care by a director. The
Company believes this provision will assist it in maintaining and securing the
services of directors who are not employees of the Company. As a result of the
inclusion of such a provision, stockholders may be unable to recover monetary
damages against directors for actions taken by them that constitute fiduciary
duties, although it may be possible to obtain injunctive or other equitable
relief with respect to such actions. If equitable remedies are found not to be
available to stockholders for any particular case, stockholders may not have any
effective remedy against the challenged conduct.

     The Company's By-Laws also provide that directors and officers shall be
indemnified against liabilities arising from their service as directors or
officers to the fullest extent permitted by Massachusetts law, which generally
requires that the individual act in good faith and in a manner he reasonably
believes to be in or not opposed to the Company's best interests.

     The Company has an insurance policy that insures the Company's directors
and officers against certain liabilities which may be incurred in connection
with the performance of their duties.

Item 7.   EXEMPTION FROM REGISTRATION CLAIMED.

     Not applicable.




<PAGE>   5

Item 8. EXHIBITS.

       The following is a complete list of exhibits filed or incorporated by
reference as part of this registration statement.

EXHIBIT

4.1    Amendment dated April 7, 1998 to National Dentex Corporation 1992 Long
       Term Incentive Plan.

5.1    Opinion of Posternak, Blankstein & Lund, L.L.P. as to the legality of the
       securities being registered.

23.1   Consent of Arthur Andersen LLP.

23.2   Consent of Counsel, contained in its opinion filed as Exhibit 5.1.

Item 9. UNDERTAKINGS.

       a)     The undersigned registrant hereby undertakes:

              (1)    To file, during any period in which offers or sales are
       being made, a post-effective amendment to this registration statement:

                     (i)    To include any prospectus required by Section 10(a)
              (3) of the Securities Act;

                     (ii)   To reflect in the prospectus any facts or events
              arising after the effective date of the registration statement (or
              the most recent post-effective amendment thereof) which,
              individually or in the aggregate, represent a fundamental change
              in the information set forth in the registration statement;
              notwithstanding the foregoing, any increase or decrease in volume
              of securities offered (if the total dollar value of securities
              offered would not exceed that which was registered) and any
              deviation from the low or high end of the estimated offering range
              may be reflected in the form of prospectus filed with the
              Securities and Exchange Commission pursuant to Rule 424(b) if, in
              the aggregate, the changes in volume and price represent no more
              than a 20% change in the maximum aggregate offering price set
              forth in the "Calculation of Registration Fee" table in the
              registration statement; and

                     (iii)  To include any material information with respect to
              the distribution not previously disclosed in the registration
              statement or any material change to such information in the
              registration statement;

              PROVIDED, HOWEVER, that paragraphs (a) (l) (i) and (a) (1) (ii)
              above do not apply if the information required to be included in a
              post-effective amendment by those



<PAGE>   6

              paragraphs is contained in periodic reports filed with or furnish
              to the Commission by the undersigned registrant pursuant to
              Section 13 or Section 15(d) of the Exchange Act that are
              incorporated by reference in the registration statement;

              (2)    That, for the purpose of determining any liability under
       the Securities Act, each such post-effective amendment shall be deemed to
       be a new registration statement relating to the securities offered
       therein, and the offering of such securities at that time shall be deemed
       to be the initial bona fide offering thereof; and

              (3)    To remove from registration by means of a post-effective
       amendment any of the securities being registered which remain unsold at
       the termination of the offering.

       b)     The undersigned registrant hereby undertakes that, for purposes of
determining any liability under the Securities Act, each filing of the
registrant's annual report pursuant to Section 13(a) or 15(d) of the Exchange
Act that is incorporated by reference in the registration statement shall be
deemed to be a new registration statement relating to the securities offered
therein, and the offering of such securities at that time shall be deemed to be
the initial bona fide offering thereof.

       c)     Insofar as indemnification for liabilities arising under the
Securities Act may be permitted to directors, officers and controlling persons
of the registrant pursuant to the foregoing provisions, or otherwise, the
registrant has been advised that in the opinion of the Securities and Exchange
Commission such indemnification is against public policy as expressed in the
Securities Act, and is, therefore, unenforceable. In the event that a claim for
indemnification against such liabilities (other than the payment by the
registrant of expenses incurred or paid by a director, officer or controlling
person of the registrant in the successful defense of any action, suit or
proceeding) is asserted by such director, officer or controlling person in
connection with the securities being registered, the registrant will, unless in
the opinion of its counsel the matter has been settled by controlling precedent,
submit to a court of appropriate jurisdiction the question whether such
indemnification by it is against public policy as expressed in the Securities
Act and will be governed by the final adjudication of such issue.




<PAGE>   7

                                   SIGNATURES

       Pursuant to the requirements of the Securities Act of 1933, the
registrant certifies that it has reasonable grounds to believe that it meets all
of the requirements for filing on Form S-8 and has duly caused this registration
statement to be signed on its behalf by the undersigned, thereunto duly
authorized, in the Town of Wayland, Commonwealth of Massachusetts, on this 7th
day of April, 1998.



                                  NATIONAL DENTEX CORPORATION


                                  By: /s/ William M. Mullahy
                                      ----------------------------------------
                                      William M. Mullahy, President and
                                      Chief Executive Officer

       Pursuant to the requirements of the Securities Act of 1933, this
registration statement has been signed below by the following persons in the
capacities and on the date indicated.

       Each person whose signature appears below constitutes and appoints
William M. Mullahy and David L. Brown, and each of them, as his true and lawful
attorney-in-fact and agent, with full power of substitution, for him and in his
name, place and stead, in any and all capacities to sign any or all amendments
or post-effective amendments to this registration statement, and to file the
same, with all exhibits thereto and other documents in connection therewith,
with the Securities and Exchange Commission, granting unto said attorney-in-fact
and agent full power and authority to do and perform each and every act and
thing requisite and necessary to be done in and about the premises, as fully to
all intents and purposes as he might or could do in person, hereby ratifying and
confirming all that said attorney-in-fact and agent or his substitute, may
lawfully do or cause to be done by virtue hereof.


         Signature                   Title                           Date
         ---------                   -----                           ----


/s/ William M. Mullahy         President, Chief                   April 7, 1998
---------------------------    Executive Officer
William M. Mullahy             and Director (Principal
                               Executive Officer)


/s/ David L. Brown             Vice President, Treasurer          April 7, 1998
---------------------------    and Chief Financial Officer 
David L. Brown                 (Principal Financial Officer)


/s/ Richard F. Becker, Jr.     Vice President - Finance           April 7, 1998
---------------------------    and Assistant Treasurer
Richard F. Becker, Jr.         (Principal Accounting
                               Officer)


<PAGE>   8

/s/ David V. Harkins           Chairman of the                    April 7, 1998
---------------------------    Board and Director
David V. Harkins               


/s/ Jack R. Crosby             Director                           April 7, 1998
---------------------------
Jack R. Crosby


/s/ William H. McClurg         Director                           April 7, 1998
---------------------------
William H. McClurg


/s/ Norman F. Strate           Director                           April 7, 1998
---------------------------
Norman F. Strate



<PAGE>   9

                                  EXHIBIT INDEX

Exhibit No.                               Description
-----------                               -----------

     4.1             Amendment dated April 7, 1998 to National Dentex
                     Corporation 1992 Long Term Incentive Plan *

     5.1             Opinion of Posternak, Blankstein & Lund, L.L.P. as to the
                     legality of the securities being registered

    23.1             Consent of Arthur Andersen LLP

    23.2             Consent of Counsel (included in Exhibit 5.1 hereto)

----------

*  Balance of Plan incorporated by reference to Exhibit 4.1 to the Company's
   Registration Statement on Form S-1 filed on December 20, 1993 (File No.
   33-70440).
[{"type": "S-8", "sequence": "1", "description": "NATIONAL DENTEX CORPORATION", "secsgml_size_bytes": 18260}]
{"company-data": {"conformed-name": "NATIONAL DENTEX CORP /MA/", "cik": "0000913616", "assigned-sic": "8000", "irs-number": "042762050", "state-of-incorporation": "MA", "fiscal-year-end": "1231"}, "filing-values": {"form-type": "S-8", "act": "33", "file-number": "333-50341", "film-number": "98596133"}, "business-address": {"street1": "111 SPEEN ST", "city": "FRAMINGHAM", "state": "MA", "zip": "01701", "phone": "5088204800"}}
1

                                                         File No. 333-__________

     As filed with the Securities and Exchange Commission on April 17, 1998

================================================================================
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

                             -----------------------

                                    FORM S-8
                             REGISTRATION STATEMENT
                                      Under
                           THE SECURITIES ACT OF 1933

                             -----------------------

                           NATIONAL DENTEX CORPORATION
             (Exact name of registrant as specified in its charter)

        MASSACHUSETTS                                         04-2762050
(State or other jurisdiction of                            (I.R.S. Employer
incorporation or organization)                            Identification No.)
               

               526 BOSTON POST ROAD, WAYLAND, MASSACHUSETTS 01778
                    (Address of Principal Executive Offices)

                          1992 LONG TERM INCENTIVE PLAN
                            (Full title of the Plan)

                             RICHARD F. BECKER, JR.
                Vice President - Finance and Assistant Treasurer
                           National Dentex Corporation
                              526 Boston Post Road
                          Wayland, Massachusetts 01778
                    (Name and address of agent for services)
                                 (508) 358-4422
                     (Telephone number, including area code,
                              of agent for service)

                                    Copy to:

                            MICHAEL L. ANDRESINO, ESQ
                      Posternak, Blankstein & Lund, L.L.P.
                             100 Charles River Plaza
                              Boston, MA 02114-2723
                                 (617) 973-6100

                             -----------------------
2
================================================================================

                         Calculation of Registration Fee

--------------------------------------------------------------------------------
                                     Proposed      Proposed
                                     Maximum        Maximum
   Title of                          Offering      Aggregate       Amount of
Securities to     Amount to be        Price        Offering       Registration
be Registered     Registered(1)    Per Share(2)    Price(3)           Fee
-------------     ------------     -----------     ---------      ------------
Common Stock
$0.01 par value   150,000 shares      $25.75      $3,862,500        $1,139.44
--------------------------------------------------------------------------------

(1)  Plus such additional number of shares as may be required pursuant to the
     1992 Long Term Incentive Plan in the event of a stock dividend, stock
     split, split-up, recapitalization or other similar event.

(2)  This estimate is made pursuant to Rule 457(c) and (h) under the Securities
     Act of 1933, as amended (the "Securities Act"), solely for purposes of
     determining the registration fee and is based upon the market value of
     outstanding shares of the Company's common stock on April 14, 1998,
     utilizing the average of the high ($26.50) and low ($25.00) sale prices
     reported on the NASDAQ National Market System for that date.

(3)  This estimate is made pursuant to Rule 457(h) under the Securities Act
     solely for the purposes of determining the registration fee and is based
     upon the maximum price at which any outstanding options under such plan may
     be exercised.

================================================================================
3

                                     PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

Item 3.   INCORPORATION OF CERTAIN DOCUMENTS BY REFERENCE.

     National Dentex Corporation (the "Company") hereby incorporates by
reference the following documents which have previously been filed with the
Securities and Exchange Commission:

     a)   The Company's Annual Report on Form 10-K for the fiscal year ended
          December 31, 1997; and

     b)   The description of the Company's Common Stock, $0.01 par value,
          contained in the Company's registration statement on Form 8-A (File
          No. 0-23092) under the Securities Exchange Act of 1934, as amended
          (the "Exchange Act").

     In addition, all documents subsequently filed with the Securities and
Exchange Commission by the Company pursuant to Sections 13 (a) and 13 (c),
Section 14 and Section 15 (d) of the Exchange Act prior to the filing of a
post-effective amendment which indicates that all securities offered hereunder
have been sold or which deregisters all securities then remaining unsold, shall
be deemed to be incorporated by reference in this registration statement and to
be a part hereof from the date of filing of such documents.

Item 4.   DESCRIPTION OF SECURITIES.

     Not Applicable.

Item 5.  INTERESTS OF NAMED EXPERTS AND COUNSEL.

     The validity of the shares to be offered hereby will be passed upon for the
Company by Posternak, Blankstein & Lund, L.L.P., Boston, Massachusetts.

     The consolidated financial statements of the Company incorporated by
reference herein from the Company's Annual Report on Form 10-K for the fiscal
year ended December 31, 1997 have been incorporated by reference in reliance on
the report of Arthur Andersen LLP, independent public accountants, given on the
authority of such firm as experts in accounting and auditing in giving said
reports.
4

Item 6.   INDEMNIFICATION OF DIRECTORS AND OFFICERS.

     Section 67 of the Business Corporation Law of the Commonwealth of
Massachusetts provides that indemnification of directors, officers, employees or
other agents may be provided by a corporation. Section 13 (b) (1-1/2) of the
Business Corporation Law of the Commonwealth of Massachusetts provides that the
Articles of Organization may contain a provision eliminating or limiting the
personal liability of a director to the corporation or its stockholders for
monetary damages for breach of fiduciary duty as a director provided that such
provision shall not eliminate or limit the liability of a director (i) for any
breach of the director's duty of loyalty to the corporation or its stockholders,
(ii) for acts or omissions not in good faith or which involve intentional
misconduct or a knowing violation of law, (iii) under Sections 61 or 62 of the
Massachusetts Business Corporation Law, or (iv) for any transaction from which
the director derived an improper personal benefit.

     Article Six of the Company's Articles of Organization, as amended,
eliminates the personal liability of each member of the Company's Board of
Directors to the Company or its stockholders for monetary damages for breach of
fiduciary duty as a director. However, the liability of a director is not
eliminated (i) for any breach of such director's duty of loyalty to the Company
or its stockholders, (ii) for acts or omissions not in good faith or which
involve intentional misconduct or a knowing violation of law, (iii) under
Section 61 or 62 of the Massachusetts Business Corporation Law, or any
amendatory or successor provision thereto, or (iv) for any transaction from
which such director derived an improper personal benefit. This provision is
intended to afford directors additional protection, and limit their potential
liability, from suits alleging a breach of duty of care by a director. The
Company believes this provision will assist it in maintaining and securing the
services of directors who are not employees of the Company. As a result of the
inclusion of such a provision, stockholders may be unable to recover monetary
damages against directors for actions taken by them that constitute fiduciary
duties, although it may be possible to obtain injunctive or other equitable
relief with respect to such actions. If equitable remedies are found not to be
available to stockholders for any particular case, stockholders may not have any
effective remedy against the challenged conduct.

     The Company's By-Laws also provide that directors and officers shall be
indemnified against liabilities arising from their service as directors or
officers to the fullest extent permitted by Massachusetts law, which generally
requires that the individual act in good faith and in a manner he reasonably
believes to be in or not opposed to the Company's best interests.

     The Company has an insurance policy that insures the Company's directors
and officers against certain liabilities which may be incurred in connection
with the performance of their duties.

Item 7.   EXEMPTION FROM REGISTRATION CLAIMED.

     Not applicable.
5

Item 8. EXHIBITS.

       The following is a complete list of exhibits filed or incorporated by
reference as part of this registration statement.

EXHIBIT

4.1    Amendment dated April 7, 1998 to National Dentex Corporation 1992 Long
       Term Incentive Plan.

5.1    Opinion of Posternak, Blankstein & Lund, L.L.P. as to the legality of the
       securities being registered.

23.1   Consent of Arthur Andersen LLP.

23.2   Consent of Counsel, contained in its opinion filed as Exhibit 5.1.

Item 9. UNDERTAKINGS.

       a)     The undersigned registrant hereby undertakes:

              (1)    To file, during any period in which offers or sales are
       being made, a post-effective amendment to this registration statement:

                     (i)    To include any prospectus required by Section 10(a)
              (3) of the Securities Act;

                     (ii)   To reflect in the prospectus any facts or events
              arising after the effective date of the registration statement (or
              the most recent post-effective amendment thereof) which,
              individually or in the aggregate, represent a fundamental change
              in the information set forth in the registration statement;
              notwithstanding the foregoing, any increase or decrease in volume
              of securities offered (if the total dollar value of securities
              offered would not exceed that which was registered) and any
              deviation from the low or high end of the estimated offering range
              may be reflected in the form of prospectus filed with the
              Securities and Exchange Commission pursuant to Rule 424(b) if, in
              the aggregate, the changes in volume and price represent no more
              than a 20% change in the maximum aggregate offering price set
              forth in the "Calculation of Registration Fee" table in the
              registration statement; and

                     (iii)  To include any material information with respect to
              the distribution not previously disclosed in the registration
              statement or any material change to such information in the
              registration statement;

              PROVIDED, HOWEVER, that paragraphs (a) (l) (i) and (a) (1) (ii)
              above do not apply if the information required to be included in a
              post-effective amendment by those
6

              paragraphs is contained in periodic reports filed with or furnish
              to the Commission by the undersigned registrant pursuant to
              Section 13 or Section 15(d) of the Exchange Act that are
              incorporated by reference in the registration statement;

              (2)    That, for the purpose of determining any liability under
       the Securities Act, each such post-effective amendment shall be deemed to
       be a new registration statement relating to the securities offered
       therein, and the offering of such securities at that time shall be deemed
       to be the initial bona fide offering thereof; and

              (3)    To remove from registration by means of a post-effective
       amendment any of the securities being registered which remain unsold at
       the termination of the offering.

       b)     The undersigned registrant hereby undertakes that, for purposes of
determining any liability under the Securities Act, each filing of the
registrant's annual report pursuant to Section 13(a) or 15(d) of the Exchange
Act that is incorporated by reference in the registration statement shall be
deemed to be a new registration statement relating to the securities offered
therein, and the offering of such securities at that time shall be deemed to be
the initial bona fide offering thereof.

       c)     Insofar as indemnification for liabilities arising under the
Securities Act may be permitted to directors, officers and controlling persons
of the registrant pursuant to the foregoing provisions, or otherwise, the
registrant has been advised that in the opinion of the Securities and Exchange
Commission such indemnification is against public policy as expressed in the
Securities Act, and is, therefore, unenforceable. In the event that a claim for
indemnification against such liabilities (other than the payment by the
registrant of expenses incurred or paid by a director, officer or controlling
person of the registrant in the successful defense of any action, suit or
proceeding) is asserted by such director, officer or controlling person in
connection with the securities being registered, the registrant will, unless in
the opinion of its counsel the matter has been settled by controlling precedent,
submit to a court of appropriate jurisdiction the question whether such
indemnification by it is against public policy as expressed in the Securities
Act and will be governed by the final adjudication of such issue.
7

                                   SIGNATURES

       Pursuant to the requirements of the Securities Act of 1933, the
registrant certifies that it has reasonable grounds to believe that it meets all
of the requirements for filing on Form S-8 and has duly caused this registration
statement to be signed on its behalf by the undersigned, thereunto duly
authorized, in the Town of Wayland, Commonwealth of Massachusetts, on this 7th
day of April, 1998.

                                  NATIONAL DENTEX CORPORATION

                                  By: /s/ William M. Mullahy
                                      ----------------------------------------
                                      William M. Mullahy, President and
                                      Chief Executive Officer

       Pursuant to the requirements of the Securities Act of 1933, this
registration statement has been signed below by the following persons in the
capacities and on the date indicated.

       Each person whose signature appears below constitutes and appoints
William M. Mullahy and David L. Brown, and each of them, as his true and lawful
attorney-in-fact and agent, with full power of substitution, for him and in his
name, place and stead, in any and all capacities to sign any or all amendments
or post-effective amendments to this registration statement, and to file the
same, with all exhibits thereto and other documents in connection therewith,
with the Securities and Exchange Commission, granting unto said attorney-in-fact
and agent full power and authority to do and perform each and every act and
thing requisite and necessary to be done in and about the premises, as fully to
all intents and purposes as he might or could do in person, hereby ratifying and
confirming all that said attorney-in-fact and agent or his substitute, may
lawfully do or cause to be done by virtue hereof.

         Signature                   Title                           Date
         ---------                   -----                           ----

/s/ William M. Mullahy         President, Chief                   April 7, 1998
---------------------------    Executive Officer
William M. Mullahy             and Director (Principal
                               Executive Officer)

/s/ David L. Brown             Vice President, Treasurer          April 7, 1998
---------------------------    and Chief Financial Officer 
David L. Brown                 (Principal Financial Officer)

/s/ Richard F. Becker, Jr.     Vice President - Finance           April 7, 1998
---------------------------    and Assistant Treasurer
Richard F. Becker, Jr.         (Principal Accounting
                               Officer)
8

/s/ David V. Harkins           Chairman of the                    April 7, 1998
---------------------------    Board and Director
David V. Harkins               

/s/ Jack R. Crosby             Director                           April 7, 1998
---------------------------
Jack R. Crosby

/s/ William H. McClurg         Director                           April 7, 1998
---------------------------
William H. McClurg

/s/ Norman F. Strate           Director                           April 7, 1998
---------------------------
Norman F. Strate
9

                                  EXHIBIT INDEX

Exhibit No.                               Description
-----------                               -----------

     4.1             Amendment dated April 7, 1998 to National Dentex
                     Corporation 1992 Long Term Incentive Plan *

     5.1             Opinion of Posternak, Blankstein & Lund, L.L.P. as to the
                     legality of the securities being registered

    23.1             Consent of Arthur Andersen LLP

    23.2             Consent of Counsel (included in Exhibit 5.1 hereto)

----------

*  Balance of Plan incorporated by reference to Exhibit 4.1 to the Company's
   Registration Statement on Form S-1 filed on December 20, 1993 (File No.
   33-70440).