(Refiles to add dropped word "open" in quote in paragraph 7)
* Buyout, trade bidders readying offers for March -sources
* Unit includes world's No. 3 dental implant business
* Astra open to whole or partial offers, sources say
(Adds possible bidders, detail on Astra Tech)
By Quentin Webb
LONDON, Feb 23 (Reuters) - About 20 bidders are readying offers for all or parts of Astra Tech, the dental and medical devices unit that AstraZeneca Plc hopes could fetch $2 billion, people familiar with the matter said.
Astra Tech, which had revenues last year of $535 million, is the world's third-biggest dental implant maker behind Switzerland's Straumann Holding and Nobel Biocare Holding. It also sells medical devices, focusing chiefly on urology.
Parent AstraZeneca, which first flagged the sale in November, has sent so-called "information memorandums" to a slew of medtech companies and private equity firms, the people said, and requested preliminary bids in March. An initial screening weeded out dozens of other potential bidders, they added.
Many bidders may only be interested in one of the two disparate arms, and AstraZeneca has invited suitors to make bids for either arm or for the whole business, the people said.
"The conversations are ongoing, and we are going through the strategic review process as we speak," a company spokeswoman said. She declined to give further details.
Astra Tech's bigger rivals in dental implants have suggested they could consider bids for the company, which is based near Gothenburg in Sweden.
Last week Straumann's Chief Executive Beat Spalinger said it was "still completely open if we will put in an offer", and in November Nobel's chief financial officer, Dirk Kirsten, told Dow Jones his company would take a look once a sale memorandum was available.
SHAREHOLDER RETURNS
Astra Tech could also interest listed U.S. companies such as Medtronic, 3M, Danaher and Dentsply International, and private equity-owned Biomet, industry analysts said in November. Biomet is backed by Blackstone, KKR, TPG and the buyout arm of Goldman Sachs.
The auction highlights AstraZeneca's current focus on boosting returns to shareholders as it heads into a wave of patent expiries on some of its biggest selling medicines including Nexium, for heartburn and stomach ulcers, and Seroquel for schizophrenia and bipolar disorder.
AstraZeneca last month announced a doubling of its share buyback programme to $4 billion in 2011.
In contrast to some of its rivals, such as GlaxoSmithKline, Novartis and Sanofi-Aventis, AstraZeneca has stayed focused on its core pharmaceuticals business rather than seeking diversification. (Reporting by Quentin Webb; additional reporting by Ben Hirschler; Editing by Will Waterman)