SCHEDULE 13D JOINT FILING AGREEMENT

Exhibit 99.A

SCHEDULE 13D JOINT FILING AGREEMENT

The undersigned hereby agree as follows:

(i) Each of them is individually eligible to use the Schedule 13D to which this Exhibit is attached, and such Schedule 13D is filed on behalf of each of them; and

(ii) Each of them is responsible for the timely filing of such Schedule 13D and any amendments thereto, and for the completeness and accuracy of the information concerning such person contained therein; but none of them is responsible for the completeness or accuracy of the information concerning the other person making the filing, unless such person knows or has reason to believe that such information is inaccurate.

Date:  September 27, 2005

	SIRONA HOLDINGS LUXCO S.C.A.
	By:		Sirona Holdings S.A.
	Its:		Manager
	By:		/s/ XXXXXXX XXXXXXXX
	Name:		Xxxxxxx Xxxxxxxx
	Its:		A Director
	By:		/s/ XXXXXXXXX XXXX
	Name:		Xxxxxxxxx Xxxx
	Its:		B Director
	SIRONA HOLDINGS S.A.
	By:		/s/ XXXXXXX XXXXXXXX
	Name:		Xxxxxxx Xxxxxxxx
	Its:		A Director
	By:		/s/ XXXXXXXXX XXXX
	Name:		Xxxxxxxxx Xxxx
	Its:		B Director

	MDCP IV GLOBAL INVESTMENTS LP
	By:		MDCP IV Global GP, LP
	Its:		General Partner
	By:		MDP Global Investors Limited
	Its:		General Partner
	By:		/s/ XXXXXXX XXXXXXXX
	Name:		Xxxxxxx Xxxxxxxx
	Its:		Managing Director
	MDCP IV GLOBAL GP, LP
	By:		MDP Global Investors Limited
	Its:		General Partner
	By:		/s/ XXXXXXX XXXXXXXX
	Name:		Xxxxxxx Xxxxxxxx
	Its:		Managing Director
	MDP GLOBAL INVESTORS LIMITED
	By:		/s/ XXXXXXX XXXXXXXX
	Name:		Xxxxxxx Xxxxxxxx
	Its:		Managing Director
	MADISON DEARBORN PARTNERS, LLC
	By:		/s/ XXXXXXX XXXXXXXX
	Name:		Xxxxxxx Xxxxxxxx
	Its:		Managing Director

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