Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of dental products distributor Patterson Companies (Nasdaq: PDCO) got drilled by investors in early trading on Friday, falling as much as 11% before recovering substantially.

So what: Patterson, which, along with dental, also serves the veterinary and rehabilitation markets, forecast that its fiscal 2011 third-quarter sales would grow less than 1% from the previous year, while earnings per share would be flat or slightly down.

Now what: Bad news? You betcha. Analysts were looking for the company to report revenue of $859 million and earnings per share of $0.51, while the company's forecast puts revenue at $825 million and earnings per share between $0.46 and $0.47. Patterson also dropped its full-year earnings per share forecast to a midpoint of $1.87, below the $1.95 that analysts had estimated. In light of the announcement, investors may want to adjust down their growth expectations for Patterson, which likely makes the price-to-earnings multiple of 18 on expected 2011 results seem expensive.

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