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                                                                     EXHIBIT 3.4



                              AMENDED AND RESTATED
                                     BY-LAWS
                                       OF
                       AMERICAN DENTAL TECHNOLOGIES, INC.

                             AS OF DECEMBER 15, 1993



                                    ARTICLE I

                                    MEETINGS

         Section 1. Place of Meeting. Any meetings of the stockholders or of the
Board of Directors of this Corporation may be held within or without the State
of Delaware as designated in notices of said meetings.

         Section 2. Annual Meeting of Stockholders. An annual meeting of the
stockholders shall be held in each year, beginning with the year 1991, on the
4th Tuesday in April at 9:00, or if such date is a holiday, the meeting shall be
on the next succeeding business day. One of the purposes of the annual meeting
of the stockholders shall be to set the number of directors to constitute the
Board of Directors and to elect a Board of Directors. If the annual meeting is
not held on the date designated therefore, the Board of Directors shall cause
the meeting to be held thereafter as convenient but within ninety (90) days
after said designated date.

         Section 3. Notice of the Annual Meeting or Delayed Annual Meeting of
Stockholders. Not less than ten (10) days, nor more than fifty (50) days, prior
to the date fixed by Section 2 of this article for the holding of the annual
meeting or delayed annual meeting of stockholders, written notice of the time,
place and purposes of such meeting shall be mailed, as hereinafter provided, to
each stockholder entitled to vote at such meeting.

         Section 4. Special Meetings of Stockholders. Special meetings of
stockholders of the Corporation may be called only by the Board of Directors
pursuant to a resolution approved by a majority of the entire Board of
Directors, upon not less the ten (10) nor more than fifty (50) days written
notice. The Board of Directors shall promptly call a special meeting of the
stockholders, upon the notice required in the foregoing sentence, pursuant to
the request of stockholders holding not less that ten percent (10%) of the
outstanding shares of this Corporation entitled to vote.

         Section 5. Intentionally Left Blank.

         Section 6. Organizational Meeting of Board. At the place of holding the
annual meeting of stockholders, and immediately following the same, the Board of
Directors as constituted upon final adjournment of such annual meeting, shall
convene for the purposes of electing officers and transacting any other business
properly brought before it, providing that the organizational meeting in any
year may be held at a different time and place than that herein provided by
consent of a majority of the Directors of such new Board.

         Section 7. Regular Meetings of the Board. Regular meetings of the Board
of Directors may be held at times and places agreed upon by a majority of the
directors at any meeting of the Board of Directors and such regular meetings may
be held at such times and places without any notice of the time, place or
purposes of such regular meetings.

         Section 8. Special Meetings of the Board. Special meetings of the Board
of Directors may be called at the request of any member of the Board at any time
by means of written notice of the time, place and purpose thereof mailed to each
director not less than three (3) days nor more than sixty (60) days prior to the
date fixed for the holding of any special meeting of Directors, but action taken
at any such meeting shall not be invalidated for want of notice if such notice
shall be waived as hereinafter provided.

         Section 9. Notices and Mailing. Every notice shall be deemed duly
served when the same has been deposited in the United States mail, with postage
prepaid, plainly addressed to the sendee at his or her or its last known
address.


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         Section 10. Waiver of Notice. Notice of the time, place and purpose of
any meeting of the stockholders or of the Board of Directors may be waived by
telegram, telecopy, radiogram, cablegram or other writing, either before or
after such meeting has been held. The attendance of any stockholder or director
at any stockholders' or directors' meeting shall constitute a waiver of any
notice to which such stockholder or director may be entitled pursuant to these
By-Laws, except when the stockholder or director, as the case may be, attends a
meeting for the express purpose of objecting, at the beginning of the meeting,
to the transaction of any business because the meeting is not lawfully convened.

                                   ARTICLE II

                                     QUORUM

         Section 1. Quorum of Stockholders. A majority of the outstanding shares
of this Corporation entitled to vote, presented by the record holders thereof in
person or by proxy, shall constitute a quorum at any meeting of the
stockholders. The stockholders present in person or by proxy at such meeting may
continue to do business until adjournment, notwithstanding the withdrawal of
enough stockholders to leave less than a quorum. Whether or not a quorum is
present, the meeting may be adjourned by a vote of the shares present.

         Section 2. Quorum of Directors. A majority of the directors then in
office shall constitute a quorum for transaction of business.

                                   ARTICLE III

                          VOTING, ELECTIONS AND PROXIES

         Section 1. Who is Entitled to Vote. Except as the Certificate of
Incorporation, or an amendment or amendments thereto, otherwise provide, each
stockholder of this corporation shall, at every meeting of the stockholders, be
entitled to one vote in person or by proxy for each share of capital stock of
this corporation held by such stockholder, subject, however, to the full effect
of the limitations imposed by the fixed record date for determination of
stockholders set forth in Section 2 of this Article.

         Section 2. Record Date for Determination of Stockholders. Any date not
more than fifty (50) nor less than ten (10) days preceding (a) the date of any
meeting of stockholders, (b) the date for the payment of any dividends, (c) the
date for the allotment of rights, (d) the date when any change or conversion of
exchange of capital stock shall go into effect may be fixed by the Board of
Directors as a record date for the determination of the stockholders entitled to
notice of, and to vote at, any such meeting, or entitled to receive payment of
any such dividend, or to any such allotment of rights, or to exercise the rights
in respect of any such change, conversion or exchange of capital stock. In such
case, such stockholders and only such stockholders as shall be stockholders of
record on the date so fixed shall be entitled to such notice of, and to vote at,
such meeting, or allotment of rights, or to exercise such rights, as the case
may be, notwithstanding any transfer of any stock on the books of the
Corporation or otherwise after any such record date fixed as aforesaid. Nothing
in this Section shall affect the rights of a stockholder and his transferee or
transferor as between themselves.

         Section 3. Proxies. No proxy shall be deemed operative unless and until
signed by the stockholder and filed with the Corporation.

         Section 4. Vote by Shareholder Corporation. Any other corporation
owning voting shares in this Corporation may vote upon the same by the president
of such stockholder corporation, or by proxy appointed by him, unless some other
person shall be appointed to vote upon such shares by resolution of the Board of
Directors of such stockholder corporation.

         Section 5. (a) Appointment of Inspectors. The Corporation shall, in
advance of any meeting of stockholders, appoint one or more inspectors to act at
the meeting and make a written report thereof. The Corporation may designate one
or more persons as alternate inspectors to replace any inspector who fails to
act. If no inspector or alternate is able to act at a meeting of stockholders,
the person presiding at the meeting shall appoint one or more inspectors to act
at the meeting. Each inspector, before entering upon the discharge of his
duties, shall take and sign an oath faithfully to execute the duties of
inspector with strict impartiality and according to the best of his ability.


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                    (b) Duties of Inspectors. The inspectors shall (i) ascertain
the number of shares outstanding and the voting power of each, (ii) determine
the shares represented at a meeting and the validity of proxies and ballots,
(iii) count all votes and ballots, (iv) determine and retain for a reasonable
period a record of the disposition of any challenges made to any determination
by the inspectors, and (v) certify their determination of the number of shares
represented at the meeting, and their count of all votes and ballots. The
inspectors may appoint or retain other persons or entities to assist them in the
performance of their duties.

                                   ARTICLE IV

                               BOARD OF DIRECTORS

         Section 1. Number and Term of Directors. The affairs of this
Corporation shall be conducted by a Board of Directors. Except as otherwise
provided by Article Eight of the Amended Certificate of Incorporation of ADL
Consolidated, Inc., the number of directors of the Corporation, shall be fixed
from time to time by the vote of a majority of the entire Board; provided,
however, that the number of directors shall not be reduced so as to shorten the
term of any director at the time in office. The directors of the Corporation
shall be divided into three classes; Class I, Class II and Class III, each such
class, as nearly as possible, to have the same number of directors. The term of
office of the initial Class I directors shall expire at the annual election of
directors by the stockholders of the Corporation in 1991, the term of the office
of the initial Class II directors shall expire at the annual election of
directors by the stockholder of the Corporation in 1992, and the term of the
office of the initial Class III directors shall expire at the annual election of
directors by the stockholders of the Corporation in 1993, or in each case
thereafter when their respective successors are elected by the stockholders and
qualify. At each annual election of directors by the stockholders of the
Corporation, the directors chosen to succeed those who terms are then expired
shall be identified as being of the same class as the directors they succeed and
shall be elected by the stockholders of the Corporation for a term expiring at
the third succeeding annual election of directors, or thereafter when their
respective successors in each case are elected by the stockholders and qualify.
Any Directors or the entire Board of Directors may be removed, with or without
cause, by the holders of a majority of the outstanding shares of this
Corporation entitled to vote.

         Section 2 (a) Vacancies. Vacancies in the Board of Directors (including
vacancies created by an increase in the number of directors) shall be filled by
appointment made by a majority of all the remaining directors. Each person so
appointed shall hold office until the next election of the class to which he
shall have been appointed and until his successor shall be elected and
qualified.

                   (b) Increases. In case of an increase in the number of
directors, the additional directors may be elected by the Board of Directors and
such directorships thereby created shall be apportioned among the classes of
directors so as to maintain such classes as nearly equal in number as possible.
In case of vacancies in the Board of Directors, a majority of the remaining
directors in the Class of Directors in such vacancy occurs, may elect directors
to fill such vacancy.

         Section 3. Action by Unanimous Written Consent. If and when all of the
directors shall severally or collectively consent in writing to any action to be
taken by the Corporation such action shall be a valid corporate action as though
it had been authorized at a meeting of the Board of Directors.

         Section 4. Power to Elect Officers. The Board of Directors shall select
a president, treasurer, and a secretary, and may select a chairman of the board,
one or more vice presidents, one or more assistant treasurers, and one or more
assistant secretaries, and any other officers that the Board of Directors deems
in the best interests of the Corporation which may be appointed and their duties
prescribed by resolution of the Board.

         Section 5. Power to Appoint Other Officers and Agents. The Board of
Directors shall have power to appoint such other officers and agents as the
Board may deem necessary for transaction of the business of the Corporation.

         Section 6. Removal of Officers and Agents. Any officer or agent may be
removed by the Board of Directors whenever, in the judgment of the Board, the
business interests of the Corporation will be served thereby.

         Section 7. Delegation of Powers. For any reason deemed sufficient by
the Board of Directors, whether occasioned by absence or otherwise, the Board
may delegate all or any of the 





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powers and duties of any officer to any other officer or director, but no
officer or director shall execute, verify or acknowledge any instrument in more
than one capacity.

         Section 8. Power to Appoint Committees of the Board. The Board of
Directors shall have power to appoint, by resolution, committees composed of one
or more directors who, to the extent provided in such resolution, may exercise
the business and affairs of the Corporation except as restricted by statute. In
the absence or disqualification of a member of the committee, the members
thereof present at a meeting and not disqualified from voting whether or not
they constitute a quorum, may unanimously appoint another director of the Board
to act at the meeting in place of such an absent or disqualified member.

                                    ARTICLE V

                                    OFFICERS

         Section 1. Chairman of the Board. The Chairman of the Board shall be
selected by and from the membership of the Board of Directors. He shall conduct
all meetings of the Board and shall perform all duties incident thereto.

         Section 2. President. The President shall have general and active
management of the business of the Corporation and shall see that all orders and
resolutions of the Board are carried into effect. He shall be ex-officio, a
member of all standing committees, and shall have the general powers and duties
of supervision and management usually vested in the office of president of a
corporation. During the prolonged absence or disability of the President, or the
vacancy of his office, the below listed individuals shall perform the duties and
exercise the power of President, until a successor is appointed, as follows:
Vice President, and if he be not available, then whosoever shall be appointed by
the Board of Directors.

         Section 3. Vice President. The duties which the Vice Presidents are to
perform shall be designated by the Board of Directors.

         Section 4. Secretary. The Secretary shall attend all meetings of the
stockholders, and shall preserve in the books of the Company true minutes of the
proceedings of all such meetings. He shall safely keep in his custody the seal
of the Corporation, and shall have authority to affix the same to all
instruments where its use is required. He shall give all notices required by
statute, by-law or resolution. He shall perform such other duties as may be
delegated to him by the Board of Directors or by the executive committee.

         Section 5. Treasurer. The Treasurer shall have custody of all corporate
funds and securities, and shall keep in books belonging to the Corporation full
and accurate accounts of all receipts and disbursements; he shall deposit all
monies, securities and other valuable effects in the name of the corporation in
such depositories as may be designated for that purpose by the Board of
Directors. He shall disburse the funds of the Corporation as may be ordered by
the Board, taking proper vouchers for such disbursements and shall render to the
President and directors at regular meetings of the Board, and whenever requested
by them, an account of all his transactions as Treasurer, and of the financial
condition of the Corporation. If required by the Board, he shall deliver to the
President of the Corporation, and shall keep in force, a bond in form, amount,
and with a surety or sureties satisfactory to the Board, conditioned for
faithful performance of the duties of his office, and for restoration to the
Corporation in case of his death, resignation, retirement or removal from
office, of all books, papers, vouchers, money and property of whatever kind in
his possession or under his control belonging to the Corporation.

         Section 6. Assistant Secretary and Assistant Treasurer. The Assistant
Secretary, in the absence or disability of the Secretary, shall perform the
duties and exercise the powers of the Secretary. The Assistant Treasurer, in the
absence or disability of the Treasurer, shall perform the duties and exercise
the powers of the Treasurer.


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                                   ARTICLE VI

                               STOCK AND TRANSFERS

         Section 1. Certificates for Shares. Every stockholder shall be entitled
to a certificate of the shares to which he has subscribed, said certificate to
be signed by the Chairman of the Board, President or a Vice President and by the
Secretary, or the Treasurer, or by the Assistant Secretary or the Assistant
Treasurer, and may be sealed with the seal of the Corporation or a facsimile
thereof certifying the number and class of shares represented by such
certificates, which certificates shall state the terms and provisions of all
classes of shares; provided, that where such certificate is signed by a transfer
agent or an assistant transfer agent, or by a transfer clerk acting on behalf of
such Corporation, and by a registrar, the signature of any such officers may be
a facsimile.

                  If the shares of the Corporation shall become listed on a
national securities exchange, the Corporation may eliminate certificates
representing such shares and provide for such other methods of recording,
noticing ownership and disclosure as may be provided by the rules of that
national securities exchange.

         Section 2. Transferable Only on Books of the Corporation. Shares shall
be transferable only on the books or by an attorney lawfully constituted in
writing, and upon surrender of the certificate therefor. A record shall be made
of every such transfer and issue. Whenever any transfer is made for collateral
security and not absolutely, the fact shall be so expressed in the entry of such
transfer.

         Section 3. Registered Stockholders. The Corporation shall have the
right to treat the registered holder of any share as the absolute owner thereof,
and shall not be bound to recognize any equitable or other claim to or interest
in such share on the part of any other person, whether or not the Corporation
shall have express or other notice thereof, save as may be otherwise provided by
the statutes of Delaware.

                                   ARTICLE VII

                            EXECUTION OF INSTRUMENTS

         Section 1. Checks, Etc. All checks, drafts and orders for payment of
money shall be signed in the name of the Corporation or any assumed name under
which the Corporation has duly filed a certificate therefor and shall be
countersigned by such officers or agents as the Board of Directors shall from
time to time designate for that purpose.

         Section 2. Contracts, Conveyances, Etc. When the execution of any
contract, conveyance or other instrument has been authorized without
specification of the executing officers, the president or any vice president, or
the treasurer or assistant treasurer, or the secretary or assistant secretary,
may execute the same in the name and behalf of this Corporation, and may affix
the corporate seal thereto. The Board of Directors shall have power to designate
the officers and agents who shall have authority to execute any instrument in
behalf of this Corporation.

                                  ARTICLE VIII

                              AMENDMENT OF BY-LAWS

         Section 1. These By-Laws may be amended, altered, changed, added to or
repealed by the affirmative vote of the holders of at least sixty-six and two
thirds percent (66 2/3%) of the shares entitled to vote at any regular or
special meeting of the stockholders if notice of the proposed amendment,
alteration, change, addition or repeal be contained in the notice of the
meeting, or by the affirmative vote of the majority of the Board of Directors if
the amendment, alteration, change, addition or repeal be proposed at a regular
or special meeting of the Board and adopted at a subsequent regular meeting,
provided, however, that no change of the date for the annual meeting of the
stockholders shall be made within thirty (30) days next before the day on which
such meeting is to be held unless consented to in writing, or by a resolution
adopted at a meeting, by the holders of at least sixty-six and two thirds
percent (66 2/3%) of the total shares of stock entitled to vote thereon and
further provided that the compensation of directors shall not be fixed or
changed except by the consent of a majority of the stockholders.


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                                   ARTICLE IX

                            DISALLOWED TAX DEDUCTIONS

         If at any time or times there is for any reason a final disallowance of
a deduction claimed by the Corporation for its federal income tax return for any
business or medical expenses paid by the Corporation in behalf of or reimbursed
by it to any stockholder or related party of the Corporation, such disallowed
amount shall be additional compensation for the services of such employee. If at
any time or times there is for any reason a final disallowance of a deduction
claimed by the Corporation on its federal income tax return for any part of any
payment in the nature of compensation or interest or rent made by the lessor, or
lessee who was, at the time of such payment, a stockholder or related party
shall thereupon become and be indebted to the Corporation for the amount by
which said payment to him or her was thus finally determined to be
nondeductible, and such stockholder or related party shall thereupon be
obligated to repay such amount to the Corporation in such reasonable
installments as the Board of Directors shall determine.

                                    ARTICLE X

                                 INDEMNIFICATION

         Section 10.1. Action by Third Party. The Corporation has the power to
indemnify a person who was or is a party or is threatened to be made a party to
a threatened, pending or completed action, suit or proceeding, whether civil,
criminal, administrative or investigative and whether formal or informal, other
than an action by or in the right of the Corporation, by reason of the fact that
he or she is or was a director, officer, employee or agent of the Corporation,
or is or was serving at the request of the Corporation as a director, officer,
partner, trustee, employee or agent of another foreign or domestic corporation
partnership, joint venture, trust or other enterprise, against expenses,
including attorneys' fines, and amounts paid in settlement actually and
reasonably incurred by him or her in connection with the action, suit, or
proceeding, if the person acted in good manner he or she reasonably believed to
be in or the best interests of the Corporation or its stockholders, and with
respect to a criminal action or proceeding, if the person had no reasonable
cause to believe his or her conduct was unlawful. The termination of an action,
suit, or proceeding by judgment, order, settlement, conviction, or upon a plea
of nolo contendere or its equivalent, does not, of itself, create a presumption
that the person did not act in good faith and in a manner which he reasonably
believed to be in or not opposed to the best interests of the Corporation or its
stockholders, and, with respect to a criminal action or proceeding, had
reasonable cause to believe that his or her conduct was unlawful.

         Section 10.2. Action by or in Right of Corporation. The Corporation has
the power to indemnify a person who was or is a party to or is threatened to be
made a party to a threatened, pending or completed action or suit by or in the
right of the Corporation to procure a judgment in its favor by reason of the
fact that he or she is or was a director, officer, employee, or agent of the
Corporation, or is or was serving at the request of the Corporation as a
director, officer, partner, trustee, employee, or agent of another foreign or
domestic corporation, partnership, joint venture, trust, or other enterprise,
whether for profit or not, against expenses, including actual and reasonable
attorneys' fees, and amount paid in settlement incurred by the person in
connection with the action or suit, if the person acted in good faith and in a
manner the person reasonably believed to be in or not opposed to the best
interests of the Corporation or its stockholders. However, indemnification shall
not be made for a claim, issue, or matter in which the person has been found
liable to the Corporation unless and only to the extent that the court in which
the action or suit was brought has determined upon application that, despite the
adjudication of liability but in view of all circumstances of the case, the
person is fairly and reasonably entitled to indemnification for the expenses
which the court considers proper.

         Section 10.3. Expense. Indemnification against expenses:

         (a) To the extent that a director, officer, employee, or agent of the
Corporation has been successful on the merits or otherwise in defense of an
action, suit, or proceeding referred to above in Sections 10.1 or 10.2, or in
defense of a claim, issue, or matter in the action, suit, or proceeding, he or
she shall be indemnified against expenses, including actual and reasonable
attorneys' fees, incurred by him or her in connection with the action, suit, or
proceeding and an action, suit, or proceeding brought to enforce the mandatory
indemnification provided in this Subsection.


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          (b) An indemnification under Sections 10.1 and 10.2 above, unless
ordered by a court, shall be made by the Corporation only as authorized in the
specific case upon a determination that indemnification of the director,
officer, employee, or agent is proper in the circumstances because he or she has
met the applicable standard of conduct set forth in Subsections (a) and (b)
above. This determination shall be made in any of the following ways:

              (i)   By a majority vote of a quorum of the board consisting of
directors who were not parties to the action, suit, or proceeding.

              (ii)  If the quorum described in subdivision (i) is not
obtainable, then by a majority vote of a committee of directors who are not
parties to the action. The committee shall consist of not less than two (2)
disinterested directors.

              (iii) By independent legal counsel in a written opinion.

              (iv)  By the stockholders.

          (c) If a person is entitled to indemnification under Section 10.1 or
10.2 for a portion of expenses including attorney's fees, judgments, penalties,
fines, and amounts paid in settlement, but not for the total amount thereof, the
Corporation may indemnify the person for the portion of the expenses, judgments,
penalties, fines, or amounts paid in settlement for which the person is entitled
to be indemnified.

         Section 10.4. Payment in Advance. Expenses incurred in defending a
civil or criminal action, suit, or proceeding described in Sections 10.1 or 10.2
above may be paid by the Corporation in advance of the final disposition of the
action, suit, or proceeding upon receipt of an undertaking by or on behalf of
the director, officer, employee, or agent to repay the expenses if it is
ultimately determined that the person is not entitled to be indemnified by the
Corporation. The undertaking shall be by unlimited general obligation of the
person on whose behalf advances are made but need not be secured.

         Section 10.5.   Non-exclusivity.

          (a) The indemnification or advancement of expenses provided under
Sections 10.1 to 10.4 is not exclusive of other rights to which a person seeking
indemnification or advancement of expenses may be entitled under the articles of
incorporation, bylaws, or a contractual agreement. However, the total amount of
expenses advanced or indemnified from all sources combined shall not exceed the
amount of actual expenses incurred by the person seeking indemnification or
advancement of expenses.

          (b) The indemnification provided for in Sections 10.1 to 10.5
continues as to a person who ceases to be a director, officer, employee, or
agent and shall inure to the benefit of the heirs, executors, and administrators
of the person.

         Section 10.6. Insurance. The Corporation shall have the power to
purchase and maintain insurance on behalf of any person who is or was a
director, officer, employee or agent of the Corporation, or is or was serving at
the request of the Corporation as a director, officer, employee or agent of
another corporation, partnership, joint venture, trust or other enterprise
against any liability asserted against him and incurred by him in any such
capacity or arising out of his status as such, whether or not the Corporation
would have the power to indemnify him against such liability under Sections 10.1
to 10.5.

         Section 10.7. Constituent Corporations. For purposes of Sections 10.1
to 10.6 above, "corporation" includes all constituent corporations absorbed in a
consolidation or merger and the resulting or surviving corporation, so that a
person who is or was a director, officer, employee, or agent of the constituent
corporation or is or was serving at the request of the constituent corporation
as a director, officer, partner, trustee, employee, or agent of another foreign
or domestic corporation, partnership, joint venture, trust, or other enterprise
whether for profit or not shall stand in the same position under the provisions
of this Subsection with respect to the resulting or surviving corporation as the
person would if he or she had served the resulting or surviving corporation in
the same capacity.


<PAGE>   8



         Section 10.8. Definitions. For the purposes of Sections 10.1 to 10.6
above, "other enterprises" shall include employee benefit plans; "fines" shall
include any excise taxes assessed on a person with respect to an employee
benefit plan; and "serving at the request of the Corporation" shall include any
service as a director, officer, employee, or agent of the Corporation which
imposes duties on, or involves services by, the director, officer, employee, or
agent with respect to an employee benefit plan, its participants or
beneficiaries; and a person who acted in good faith and in a manner he or she
reasonably believed to be in the interest of the participants and beneficiaries
of an employee benefit plan shall be considered to have acted in a manner "not
opposed to the best interests of the Corporation or its stockholders" as
referred to in Sections 10.1 and 10.2 above.

                                   ARTICLE XII

                                   FISCAL YEAR

         The fiscal year of the Corporation shall be January 1 to December 31.