Exhibit 4.12

AMENDMENT
NO. 3 TO
ASSET PURCHASE AGREEMENT

AMENDMENT
NO. 3 TO ASSET PURCHASE AGREEMENT (the "Third Amendment"), dated as of June 29, 2001, among CORE-VENT CORPORATION, d/b/a Paragon Implant Company, a Nevada
corporation ("Paragon"), CORE-VENT BIOENGINEERING, INC., a California corporation ("C-V BioEngineering"), CORE-VENT PARAGON BIO, a California corporation
("C-V Paragon"), PARAGON ADMINISTRATION, INC., a California corporation ("Paragon Administration"), CORE-VENT GmbH, a corporation organized under the laws of the Federal
Republic of Germany ("C-V GmbH"), CORE-VENT ISRAEL (1997), a PARAGON Company Ltd., a corporation organized under the laws of Israel ("C-V Israel"; and
together with Paragon, C-V BioEngineering, C-V Paragon, Paragon Administration, C-V GmbH and C-V Israel, the "Seller"), the shareholders of Paragon
identified on the signature page hereof (the "Paragon Shareholders"), the shareholders of C-V BioEngineering identified on the signature page hereof (the "C-V BioEngineering
Shareholders"), the Niznick Family Foundation (the "Niznick Foundation"), a California not-for-profit corporation, DR. GERALD A. NIZNICK, an individual ("Dr. Niznick";
and together with the Paragon Shareholders, the C-V BioEngineering Shareholders and the Niznick Foundation, the "Shareholders"), SULZER MEDICA USA INC., a Delaware corporation
("Parent"), SULZER DENTAL INC. (formerly known as Sulzer Calcitek Inc.), a Delaware corporation ("Calcitek") and SULZER DENTAL GmbH (formerly known as Sulzer Calcitek GmbH.), a
corporation organized under the laws of the Federal Republic of Germany ("Calcitek GmbH"), SULZER DENTAL LTD., a corporation organized under the laws of Israel ("Calcitek Israel") and SULZER
DENTAL CORP, a corporation organized under the laws of Canada ("Calcitek Canada" and together with Calcitek, and Calcitek GmbH and Calcitek Israel, the "Purchaser").

W
I T N E S S E T H:

WHEREAS,
the Seller, the Shareholders, Parent and Purchaser entered into (i) the Asset Purchase Agreement dated November 1, 2000, pursuant to which Seller agreed to sell
and Purchaser agreed to purchase the Assets, all as more particularly set forth therein; (ii) Amendment No. 1 to Asset Purchase Agreement dated January 8, 2001; and
(iii) Amendment No. 2 to Asset Purchase Agreement (as so amended, the "Asset Purchase Agreement") pursuant to which Seller agreed to modify certain of the terms of the original Asset
Purchase Agreement, all as more particularly set forth therein;

WHEREAS,
the parties hereto wish to further amend the Asset Purchase Agreement by executing this Amendment No. 3 to Asset Purchase Agreement all as more particularly set forth
herein.

NOW,
THEREFORE, in consideration of the premises and the mutual agreements and covenants hereinafter set forth, and intending to be legally bound hereby, the parties hereby agree as
follows:

1.Definitions.Capitalized terms used herein without definition shall have the meanings ascribed to such terms
in the Asset Purchase Agreement.

2.Amendments.The parties hereby agree to amend the Asset Purchase Agreement as follows:

In
Section 2.08(b)(ii), the first sentence is deleted in its entirety and replaced with the following: "The Seller may dispute any amounts reflected on the Closing Balance Sheet,
provided that the Seller shall have notified the Purchaser and the Purchaser's Accountants in writing of each disputed item, specifying the estimated amount thereof in dispute and setting forth, in
reasonable detail, the basis for such dispute, on or before July 10, 2001. In the event that Seller identifies disputed amounts, Seller and Purchaser will begin discussions in an attempt to
identify the Independent Accounting Firm."

3.No Further Modifications.Except as expressly set forth herein, the terms and provisions of the Asset
Purchase Agreement remain unmodified and in full force and affect.

---

4.Miscellaneous.

(a)    This
Amendment No. 3 shall be governed by, and construed in accordance with, the laws of the State of California, applicable to contracts executed in and to be
performed entirely in that state.

(b)    This
Amendment No. 3 may be executed in one or more counterparts, and by the different parties hereto in separate counterparts, each of which when executed shall
be deemed to be an original but all of which taken together shall constitute one and the same agreement.

IN
WITNESS WHEREOF, the parties hereto have executed, or have caused this Agreement to be executed by their respective officers thereunto duly authorized, as of the date first written
above.

| |  | CORE-VENT CORPORATION, d/b/a Paragon Implant Seller                                                      
| |  | ---------------------------------------------------------------------------------------------------------
| |  | By: /s/ Dr. Gerald A. Niznick by Steve Good, attorney in factName: Dr. Gerald A. Niznick
Title: President
| |  | CORE-VENT BIOENGINEERING, INC.                                                                           
| |  | By: /s/ Dr. Gerald A. Niznick by Steve Good, attorney in factName: Dr. Gerald A. Niznick
Title: President
| |  | CORE-VENT PARAGON BIO                                                                                    
| |  | By: /s/ Dr. Gerald A. Niznick by Steve Good, attorney in factName: Dr. Gerald A. Niznick
Title: President
| |  | PARAGON ADMINISTRATION, INC.                                                                             
| |  | By: /s/ Dr. Gerald A. Niznick by Steve Good, attorney in factName: Dr. Gerald A. Niznick
Title: President
| |  | CORE-VENT GmbH                                                                                           
| |  | By: /s/ Dr. Gerald A. Niznick by Steve Good, attorney in factName: Dr. Gerald A. Niznick
Title: President

---

| |  | CVPBE, Inc.                                                                                              
| |  | ---------------------------------------------------------------------------------------------------------
| |  | By: /s/ Dr. Gerald A. Niznick by Steve Good, attorney in factName: Dr. Gerald A. Niznick
Title: President
| |  | CV Equipment, Inc.                                                                                       
| |  | By: /s/ Dr. Gerald A. Niznick by Steve Good, attorney in factName: Dr. Gerald A. Niznick
Title: President
| |  | PARAGON DENTAL IMPLANT, LTD.                                                                             
| |  | By: /s/ Dr. Gerald A. Niznick by Steve Good, attorney in factName: Dr. Gerald A. Niznick
Title: President
| |  | THE PARAGON SHAREHOLDERS                                                                                 
| |  | By: /s/ Dr. Gerald A. Niznick by Steve Good, attorney in factDr. Gerald A. Niznick                       
| |  | THE C-V BIOENGINEERING STOCKHOLDERS                                                                      
| |  | By: /s/ Dr. Gerald A. Niznick by Steve Good, attorney in factDr. Gerald A. Niznick                       
| |  | THE NIZNICK FOUNDATION                                                                                   
| |  | By: /s/ Dr. Gerald A. Niznick by Steve Good, attorney in factName: Dr. Gerald A. Niznick
Title: Director 
| |  | SULZER MEDICA USA INC.                                                                                   
| |  | By: /s/ David S. WiseName: David S. Wise
Title: Group Vice President, General Counsel and Secretary      

---

| |  | SULZER DENTAL INC.                                             
| |  | ---------------------------------------------------------------
| |  | By: /s/ Steven E. HansonName: Steven E. Hanson
Title: President
| |  | SULZER DENTAL GmbH                                             
| |  | By: /s/ Steven E. HansonName: Steven E. Hanson
Title: President
| |  | SULZER DENTAL LTD.                                             
| |  | By: /s/ Steven E. HansonName: Steven E. Hanson
Title: President
| |  | SULZER DENTAL CORP.                                            
| |  | By: /s/ Steven E. HansonName: Steven E. Hanson
Title: President

---

QuickLinks