FORM 3

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 INITIAL STATEMENT OF BENEFICIAL OWNERSHIP OF SECURITIES Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL OMB Number: 3235-0104 Expires: January 31, 2005 Estimated average burden hours per response... 0.5

(Print or Type Responses)

1. Name and Address of Reporting Person *   ALEXOS NICHOLAS W 2. Date of Event Requiring Statement (Month/Day/Year) 06/20/2006 3. Issuer Name and Ticker or Trading Symbol SIRONA DENTAL SYSTEMS, INC. [SIRO] (Last) (First) (Middle) C/O MADISON DEARBORN PARTNERS, LLC, THREE FIRST NATIONAL PLAZA, SUITE 3800 4. Relationship of Reporting Person(s) to Issuer (Check all applicable) __X__ Director _____ 10% Owner _____ Officer (give title below) _____ Other (specify below) 5. If Amendment, Date Original Filed(Month/Day/Year) (Street) CHICAGO, IL 60602 6. Individual or Joint/Group Filing(Check Applicable Line) _X_ Form filed by One Reporting Person ___ Form filed by More than One Reporting Person (City) (State) (Zip) Table I - Non-Derivative Securities Beneficially Owned

1.Title of Security (Instr. 4) 2. Amount of Securities Beneficially Owned (Instr. 4) 3. Ownership Form: Direct (D) or Indirect (I) (Instr. 5) 4. Nature of Indirect Beneficial Ownership (Instr. 5) Common Stock 36,972,480 I See Footnote (1) (2)

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.			SEC 1473 (7-02)
	Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB control number.

Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)

1. Title of Derivative Security (Instr. 4)	2. Date Exercisable and Expiration Date (Month/Day/Year)		3. Title and Amount of Securities Underlying Derivative Security (Instr. 4)		4. Conversion or Exercise Price of Derivative Security	5. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 5)	6. Nature of Indirect Beneficial Ownership (Instr. 5)
	Date Exercisable	Expiration Date	Title	Amount or Number of Shares

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
ALEXOS NICHOLAS W C/O MADISON DEARBORN PARTNERS, LLC THREE FIRST NATIONAL PLAZA, SUITE 3800 CHICAGO, IL 60602	  X	Â	Â	Â

Signatures

by /s/ Nicholas W. Alexos		06/21/2006
**Signature of Reporting Person		Date

Explanation of Responses:

*	If the form is filed by more than one reporting person, see Instruction 5(b)(v).
**	Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1)	Owned by Sirona Holdings Luxco S.C.A. ("Luxco")
(2)	The following entities may be deemed to have a beneficial interest in the Common Stock held by Luxco. Sirona Holdings S.A. ("Luxco Manager"), by virtue of its being the sole manager of Luxco; MDCP IV Global Investments LP ("MDCP IV Global Investments"), by virtue of its being the controlling shareholder of Luxco Manager; MDP IV Global GP, LP ("MDP IV Global GP"), by virtue of its being the sole general partner of MDCP IV Global Investments and MDP Global Investors Limited by virtue of its being the sole general partner of MDP IV Global GP. As a member of MDP Global Investors Limited, Mr. Alexos may also be deemed to share beneficial ownership of the Common Stock held by Luxco. Mr. Alexos disclaims beneficial ownership of the above referenced shares except to the extent of his pecuniary interest therein.

Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, See Instruction 6 for procedure.

Potential persons who are to respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB number.