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                                                                    EXHIBIT 3.6

                           ARTICLES OF INCORPORATION

                                       OF

                           CT ACQUISITION CORPORATION


         The undersigned natural person of the age of eighteen (18) years or
more, acting as an incorporator of a corporation under the Texas Business
Corporation Act, hereby adopts the following Articles of Incorporation for such
corporation:

                                   ARTICLE I

                                      NAME

         The name of the corporation is CT Acquisition Corporation.


                                   ARTICLE II

                                    DURATION

         The period of its duration is perpetual.


                                  ARTICLE III

                                    PURPOSE

         The purpose or purposes for which the corporation is organized are to
transact any and all lawful business for which corporations may be incorporated
under the Texas Business Corporation Act.


                                   ARTICLE IV

                                     SHARES

         The aggregate number of shares which the corporation has authority to
issue is One Thousand (1,000) shares of One Cent ($0.01) par value per share.
Such shares are designated as common stock and shall have identical rights and
privileges in every respect.


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                                   ARTICLE V

                          DENIAL OF PREEMPTIVE RIGHTS

         The right of a shareholder referred to in Article 2.22-1 of the Texas
Business Corporation Act, to exercise a preemptive right to acquire additional,
unissued or treasury shares of the corporation or securities of the corporation
convertible into or carrying a right to subscribe to or acquire shares of the
corporation is hereby denied.


                                   ARTICLE VI

                              NONCUMULATIVE VOTING

         Directors shall be elected by majority vote. No shareholder of the
corporation shall have the right to cumulate his votes in the election of
directors.


                                  ARTICLE VII

                             POWER TO AMEND BYLAWS

         Without limiting the power of the shareholders of the corporation to
amend or repeal the corporation's bylaws or to adopt new bylaws, the Board of
Directors shall have the power to amend or repeal the corporation's bylaws and
to adopt new bylaws.


                                  ARTICLE VIII

                            COMMENCEMENT OF BUSINESS

         The corporation will not commence business until it has received for
the issuance of its shares consideration of the value of One Thousand Dollars
($1,000.00), consisting of money, labor done, or property actually received.


                                   ARTICLE IX

                          REGISTERED OFFICE AND AGENT

         The street address of the initial registered office of the corporation
is 350 North St. Paul Street, Dallas, Texas 75201, and the name of its initial
registered agent at such address is CT Corporation System.

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                                   ARTICLE X

                               INITIAL DIRECTORS

         The number of Directors constituting the initial Board of Directors is
two (2) and the name and address of each person who is to serve as a Director
until the first annual meeting of the shareholders, or until his successor or
successors are elected and qualified is:

                         J. Ernest Talley
                         13800 Montfort Drive
                         Suite 300
                         Dallas, Texas 75240

                         Mark E. Speese
                         13800 Montfort Drive
                         Suite 300
                         Dallas, Texas 75240

         The number of Directors may hereafter be increased or decreased as
provided in the bylaws of the corporation.


                                   ARTICLE XI

                             LIABILITY OF DIRECTORS

         No Director of the Corporation shall be liable to the Corporation or
its shareholders for monetary damages for an act or omission in the Director's
capacity as a Director, except that this article does not eliminate or limit
the liability of a Director to the extent the Director is found liable for: (1)
a breach of the Director's duty of loyalty to the Corporation or its
shareholders; (2) an act or omission not in good faith that constitutes a
breach of duty of the Director to the Corporation or an act or omission that
involves intentional misconduct or a knowing violation of the law; (3) a
transaction from which the Director received an improper benefit, whether or
not the benefit resulted from an action taken within the scope of the
Director's office; or (4) an act or omission for which the liability of a
Director is expressly provided for by an applicable statute.

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                                  ARTICLE XII

                   ACTIONS BY SHAREHOLDERS WITHOUT A MEETING

         Any action required by the Texas Business Corporation Act to be taken
at any annual or special meeting of shareholders, or any action which may be
taken at any annual or special meeting of shareholders, may be taken without a
meeting, without prior notice, and without a vote, if a consent or consents in
writing, setting forth the action so taken, shall be signed by the holder or
holders of shares having not less than the minimum number of votes that would
be necessary to take such action at a meeting at which the holders of all
shares entitled to vote on the action were present and voted.


                                  ARTICLE XIII

                                  INCORPORATOR

         The name and address of the incorporator is:

                    Lisa N. Tyson
                    Winstead Sechrest & Minick P.C.
                    5400 Renaissance Tower
                    1201 Elm Street
                    Dallas, Texas  75270-1999


         IN WITNESS WHEREOF, I have hereunto set my hand this the 6th day of
May, 1996.


                                        /s/ LISA N. TYSON
                                        ---------------------------------------
                                        Lisa N. Tyson

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