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                                                                     EXHIBIT 4.6

                        REVOLVING CREDIT PROMISSORY NOTE


$2,500,000.00                                                   October 17, 1996



       For value received TEXAS AIRSONICS, INC. and AMERICAN DENTAL
TECHNOLOGIES, INC., (hereinafter called "Maker" whether one or more) promises
to pay to the order of THE INTERNATIONAL BANK, ("Payee") at its office in
Corpus Christi, Nueces County, Texas, in lawful money of the United States the
sum of TWO MILLION FIVE HUNDRED THOUSAND DOLLARS, or so much thereof as may be
advanced and unpaid hereon from time to time, together with interest on the
unpaid principal balance hereon outstanding from time to time prior to maturity
at a rate which is the lesser from time to time of: (i) a variable rate which
is THE REFERENCE RATE as such varies from time to time, such variable rate to
change at the same time and with changes in the said Reference Rate; or (ii)
the maximum legal rate which may be lawfully contracted for, charged or
received hereon from time to time under applicable law; or (iii) 24% per annum.
The term "Reference Rate" shall mean that variable rate of interest per annum
established by the largest U. S. Banks ("Reference Banks") from time to time as
their "prime rate" as reported from time to time in the Money Rates Section of
the Southwest Edition of the Wall Street Journal.  In the event more than one
rate is published as said "prime rate" the average of such rates shall be used
in determining the Reference Rate.  Such rate is set by the Reference Banks as
a general reference rate of interest, taking into account such factors as the
Reference Banks may deem appropriate, it being understood that many of the
Reference Banks' commercial or other loans are priced in relation to such rate,
that it is not necessarily the lowest or best rate actually charged to any
customer and that the Reference Banks may make various commercial or other
loans at rates of interest having no relationship to such rate.  In the event
that Reference Banks do not have a rate designated by them as their "prime
rate", then the "Reference Rate" under the note shall be deemed to be the
variable rate of interest per annum which is the general reference rate
designated by Reference Banks as their "base rate", "prime rate", "reference
rate", or other similar rate which is comparable to the Reference Rate as
described above.



       All interest rates hereunder shall be computed on a full calendar year
(365/366 days) basis.  Article 5069 Chapter 15 V.A.T.S. shall not in any event
apply to the loan evidenced hereby.  After maturity hereof, unpaid principal
and accrued interest shall bear interest from maturity until paid at the rate
of eighteen percent (18%) per annum, calculated on a full calendar year
basis.



       Principal and accrued interest shall be due and payable ON DEMAND, but
if no demand then principal shall be due and payable on or before October 15,
1997, and accrued interest shall be due and payable on a monthly basis
commencing November 15, 1996, and on the same day of each succeeding month
thereafter, and at maturity.


         All payments hereon shall be first applied to accrued interest with
the remainder, if any, applied to unpaid principal.  Principal and accrued
interest may be prepaid in whole or in part from time to time without penalty
or premium.



         This note evidences funds to be advanced to Maker pursuant to a
Revolving Credit Agreement of even date.
Payment hereof is secured and guaranteed as set forth in such Agreement.



         This note shall evidence the Maker's, endorsers', sureties' and
guarantors' joint and several obligation to pay all advances, together with
interest thereon, made by Payee to Maker (or to either of them) or for Maker's
account (or for the account of either of them).  Interest shall accrue on
principal only from the date advanced until paid.  Each of Texas AirSonics,
Inc. and American Dental Technologies, Inc. shall be jointly and severally
liable hereunder.



       The Maker and all endorsers, guarantors and sureties hereof authorize
Payee from time to time to make advances to the Maker hereof without any
requirement that Payee notify them or any of them of such advances, provided
the total principal owing hereunder shall not exceed at any one time the face
amount of this note.  The amount owing hereunder at any given time shall be
determined by the total of all advances made less any principal payments made
plus the unpaid accrued interest thereon as determined by the provisions
hereof.



         At the option of the holder hereof, the maturity of this note may be
accelerated and all unpaid amounts of principal and accrued interest shall
become immediately due and payable, without presentment or demand or notice to
any person obligated as Maker or any other person obligated hereon, upon the
occurrence of any of the following events: default in the payment of any
indebtedness or any part thereof owing to holder by any person obligated as
Maker or any other person obligated hereon, whether evidenced by this note or
otherwise; or failure to perform or keep any of the material conditions and
covenants contained in any document given to secure indebtedness owing to
holder by any person obligated as Maker or any other person obligated hereon or
any document evidencing loan agreements made in connection herewith; or
insolvency or making of any general assignment for the benefit of creditors by
any person obligated as Maker or any other person obligated hereon; or the
filing of any petition or commencement of any proceeding by or against any
person obligated as Maker or any other person obligated hereon for any relief,
discharge, rearrangement, reorganization or otherwise under any bankruptcy or
insolvency laws; or the levying on, seizure or freezing of any account of any
person obligated as Maker or any other person obligated hereon by any agency or
instrumentality of the State or Federal government; or the issuance of any writ
of attachment or garnishment relating to or affecting any of the property or
assets of any person obligated as Maker or any other person obligated hereon;
or if the holder hereof in good faith deems itself insecure.

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$2,500,000.00 Revolving Credit Promissory Note
Maker:      Texas AirSonics, Inc. and American Dental Technologies, Inc.
Payee:      The International Bank


       Maker and all sureties, endorsers and guarantors of this note hereby
severally waive demand, presentment for payment, notice of nonpayment,
protest, notice of protest, notice of intention to accelerate maturity, notice
of acceleration of maturity, and all other notice, and diligence in collecting
this note or filing suit thereon or enforcing any security given therefor, and
agree to any substitution, exchange or release of any security now or hereafter
given for this note or the release of any party primarily or secondarily liable
hereon.  Maker and all sureties, endorsers and guarantors of this note further
severally agree that it will not be necessary for the payee or any holder
hereof, in order to enforce payment of this note, to first institute or exhaust
its remedies against any person obligated as Maker or other party liable
therefor or to enforce its rights against any security for this note and hereby
consent to the renewal and extension or modification from time to time of this
note (regardless of the number or length of time of the renewals, extensions or
modifications), and to any other indulgence with respect hereto, without notice
of any such renewal, extension, modification or indulgence.  All persons
obligated hereon, whether as a maker, endorser, surety, guarantor or otherwise,
shall be jointly and severally liable for repayment of the indebtedness
evidenced by or arising under this note.


         In the event that this note is placed into the hands of an attorney
for collection, or if collected through probate, bankruptcy or other judicial
proceedings, then there shall be additionally owing hereon all expenses and
costs of collection, including reasonable attorney's fees.


       It is expressly provided and stipulated that, notwithstanding any
provision of this Note or any loan agreement or in any deed of trust,
assignment, security agreement or other agreement securing payment of this
note, in no event shall the aggregate of all interest paid by the Maker to the
holder hereof or contracted for, chargeable or receivable hereunder ever exceed
the maximum legal rate of interest which may lawfully be charged Maker under
the laws of the State of Texas or the United States (whichever may permit the
higher rate) on the principal balance of this note from time to time advanced
and remaining unpaid.  In this connection, it is expressly stipulated and
agreed that it is the intent of the payee and the Maker in the execution and
delivery of this note to contract in strict compliance with usury laws of the
State of Texas or the United States (whichever may permit the higher rate).  In
the event said maximum legal rate is calculated under Texas statutes, the
applicable rate ceiling (maximum rate) shall be the indicated (weekly) rate
ceiling from time to time in effect, as provided in Article 5069-1.04 V.A.T.S.,
as amended.  In furtherance thereof, none of the terms of this note or any loan
agreement or in any deed of trust, assignment, security agreement or other
agreement securing payment of this note, shall ever be construed to create a
contract to pay for the use, forbearance or detention of money, interest at a
rate in excess of the maximum legal interest rate permitted to be charged to
the Maker under such laws.  The Maker or any guarantors, endorsers or other
parties now or hereafter becoming liable for payment of this note shall never
be liable for interest in excess of the maximum interest that may lawfully be
charged under such laws, and the provisions of this paragraph shall govern over
all other provisions of this note or any loan agreement or any deed of trust,
assignment, security agreement or other agreement securing payment of this
note, should such provisions be in apparent conflict herewith.  All sums paid
or agreed to be paid to payee or the holder of this note for the use,
forbearance or detention of the indebtedness of Maker under the terms of this
note or otherwise shall be amortized, prorated, allocated and spread throughout
the full term of such indebtedness until payment in full so that the actual
rate of interest with respect to such indebtedness is uniform throughout the
term hereof, and, in conjunction therewith, if the loan evidenced by this note
should ever be deemed to consist of two or more loans, then any sum paid or
agreed to be paid to the holder hereof for the use, forbearance or detention of
the indebtedness of Maker to payee under the terms of this note which is deemed
to be excessive interest with respect to one or more of such loans shall be
allocated to the loans for which a maximum lawful rate of interest has not been
contracted for, charged or received or for which no maximum rate of interest
exists.


                                              TEXAS AIRSONICS, INC.


                                              By:  Benjamin J. Gallant
                                                 ---------------------
                                                 Benjamin J. Gallant
                                                 President and CEO


                                              AMERICAN DENTAL TECHNOLOGIES, INC.




                                              By:  Benjamin J. Gallant
                                                 ---------------------
                                                 Benjamin J. Gallant
                                                 President