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                                                                   EXHIBIT 10.13

                                PROMISSORY NOTE

1.   PRINCIPAL AMOUNT: $675,000, U.S.D.

2.   INTEREST RATE: 8.5% ANNUM

3.   DATE OF LOAN: DECEMBER 15, 1999

4.   MATURITY DATE: FEBRUARY 15, 2001

5.   LENDER:   American Dental Technologies, Inc.
               5555 Bear Lane
               Corpus Christi, Texas 78405

6.   BORROWER: Denics, Co. Ltd.
               Yotsuya Y's Bldg
               7-6 Honshio-CHO
               Shinjuku-ku
               Tokyo 160, Japan

7.   IN PAYMENT OF INVOICES #47073 AND #48232, BORROWER AGREES TO PAY LENDER THE
     PRINCIPAL AMOUNT OF $675,000 U.S.D. PLUS INTEREST AT THE RATE OF 8.5% PER
     ANNUM IN THE MANNER DESCRIBED BELOW.

          PAYMENT SCHEDULE: TWELVE EQUAL MONTHLY PAYMENTS OF $58,881.77 U.S.D.
          BEGINNING ON MARCH 15, 2000 AND CONTINUING ON THE 15TH OF EACH
          SUCCEEDING MONTH WITH THE LAST PAYMENT ON FEBRUARY 15, 2001.
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          All payments will be made to Lender at its address set forth above and
          in lawful currency of the United State of America.


          PREPAYMENT: This note may be prepaid in full or in part on or before
          its Maturity Date,

8.   Compliance with applicable law: It is Lender's Intention to comply fully
     with Texas law and federal law as applicable, regulating credit terms,
     interest, fees, charges, expenses and other amounts. For purposes of
     determining Lender's compliance with such laws, the following shall apply
     to the extent permitted by law: (a) any contract, charge or receipt by
     Lender, whether occurring now or in the future, shall be strictly limited
     by this provision; (b) the "Maximum Lawful Rate" shall be the maximum
     lawful ceiling, rate or amount that Lender could have contracted to change
     or ceiling, rate or amount that Lender could have contracted to charge or
     receive under Texas law or applicable federal law, whether permits the
     highest maximum ceiling, rate or amount; (c) to the extent Texas Article
     5069 1.04, as amended, provides the Maximum Lawful rated, the "Indicated
     rate ceiling" shall apply unless changed by the Lender or in accordance
     with Texas law; (d) Lender may calculate rates or mounts by aggregating,
     amortizing, prorating, allocating and spreading contracted for charge or
     receipt shall obligate Borrower or any obligor to pay any amount in excess
     of Maximum Lawful Rate or waive any right under Texas 5069; and (f) any
     contract, charge or receipt that in the event of acceleration or under any
     other contingency purports to require the payment or collection of any
     amount in excess of the Maximum Lawful Rate shall automatically be

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     reformed to not obligate Borrower or any Obligor to pay any amount in
     excess of the Maximum Lawful Rate. If Lender ever contracts for charges or
     receives rate or amount in excess of the Maximum Lawful Rate, the excess
     (whether denominated principal, interest, or other wise) shall be
     automatically subject to reallocation, cancellation, credit, applications
     or refund to eliminate any amount in excess of the Maximum Lawful Rates.

9.   Financial information: Borrower will provide Lender with current financial
     statements including, but not limited to, balance sheets and profit and
     loss statements and other information upon request.

10.  Modification and Waiver: The modification or waiver of any Borrower's
     obligations or Lender's rights under this Note must be contained in a
     writing signed by Lender. Lender may perform any of Borrower's obligations
     or delay or fail to exercise any of its rights without causing a waiver of
     those obligations or rights. A waiver on one occasion will not constitute a
     waiver other occasion. Borrower's obligations under this Note shall not be
     affected if Lender amends compromises, exchanges, fails to exercise,
     impairs or releases any of the obligations belonging to any co-borrower or
     guarantor of any of its rights against any co-borrower, guarantor or
     collateral.

11.  Severability: If any provision of this Note violates the law or is
     unenforceable, the rest of the Note of the will remain valid.


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12.  Notice: Any notice or other communications to be provided to Borrower or
     Lender under this Note shall be in writing and sent to the parties at the
     addresses described in this Note or such other addresses and the parties
     may designate in writing from time to time.

13.  Applicable law: This note shall be governed by the laws of the state of
     Texas and applicable federal laws. Borrower consents to the jurisdiction
     and venue of any court located in Nueces County, Texas in the event of any
     legal proceeding under this Note.

14.  Collection expenses: If Lender hires an attorney (who is not a salaried
     employee of Lender) to assist in collecting any amount due or enforcing any
     right or remedy under this Note, Borrower agrees to pay Lender's reasonable
     attorney's fees and collection costs subject to court award.

15.  Miscellaneous: This Note is being executed for commercial purposes.
     Borrower and Lender agree that time is of the essence. Borrower waives
     presentment, demand for payment, notice of intent to accelerate, notice of
     acceleration, notice of dishonor and protest. All references to Borrower in
     this Note shall include all of the parties signing this Note. If there is
     more than one Borrower, their obligation will be joined and several. This
     Note and any related documents represent the complete and integrated
     understanding between Borrower and Lender pertaining to the terms and
     conditions of those documents.

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16. ADDITIONAL TERMS: THIS NOTE CONSTITUTES PAYMENT OF INVOICES #47073 AND
    #48232 OWED BY BORROWER TO LENDER.

DENICS CO. LTD

BY: /s/ KENGO IWAI
    ---------------------
    Kengo Iwai, President

                            UNCONDITIONAL GUARANTEE

     I, SHOHEI OGURI OF TOKYO, JAPAN HEREBY IRREVOCABLY AND UNCONDITIONALLY
GUARANTEE PAYMENT OF ALL AMOUNTS OWED BY BORROWER TO LENDER AS SET FORTH IN
THE  FORGOING NOTE FROM DENICS CO., LTD. TO AMERICAN DENTAL TECHNOLOGIES, INC.
AS IF I WAS THE BORROWER. THIS GUARANTEE IS PERFORMABLE IN CORPUS CHRISTI,
TEXAS.

                                        /s/ SHOHEI OGURI
                                        --------------------------------
                                        SHOHEI OGURI, INDIVIDUALLY


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

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

                                        ADDRESS:


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