Editor's Note: TheStreet ratings do not represent the views of TheStreet's staff or its contributors. Ratings are established by computer based on metrics for performance (which includes growth, stock performance, efficiency and valuation) and risk (volatility and solvency). Companies with poor cash flow or high debt levels tend to earn lower ratings in our model One out of the three major indices are trading lower today with the Dow Jones Industrial Average ( ^DJI) trading down 23 points (-0.2%) at 15,060 as of Friday, May 10, 2013, 12:49 PM ET. The NYSE advances/declines ratio sits at 1,550 issues advancing vs. 1,371 declining with 121 unchanged. The Health Services industry currently sits up 0.6% versus the S&P 500, which is unchanged. On the negative front, top decliners within the industry include Grifols ( GRFS), down 3.28, and Intuitive Surgical ( ISRG), down 2.41. Top gainers within the industry include Unilife Corporation ( UNIS), up 58.4%, St Jude Medical ( STJ), up 1.9%, Edwards Life ( EW), up 1.5%, Boston Scientific ( BSX), up 1.4% and HCA Holdings ( HCA), up 1.5%. TheStreet Ratings group would like to highlight 3 stocks pushing the industry lower today: 3. Sirona Dental Systems ( SIRO) is one of the companies pushing the Health Services industry lower today. As of noon trading, Sirona Dental Systems is down $4.01 (-5.3%) to $71.40 on heavy volume Thus far, 474,357 shares of Sirona Dental Systems exchanged hands as compared to its average daily volume of 245,900 shares. The stock has ranged in price between $71.13-$75.40 after having opened the day at $75.27 as compared to the previous trading day's close of $75.41. Sirona Dental Systems, Inc., together with its subsidiaries, develops, manufactures, and markets dental equipment for dentists worldwide. It operates in four segments: Dental CAD/CAM Systems, Imaging Systems, Treatment Centers, and Instruments. Sirona Dental Systems has a market cap of $4.3 billion and is part of the health care sector. The company has a P/E ratio of 31.8, above the S&P 500 P/E ratio of 17.7. Shares are up 16.8% year to date as of the close of trading on Thursday. TheStreet Ratings rates Sirona Dental Systems as a buy. The company's strengths can be seen in multiple areas, such as its revenue growth, largely solid financial position with reasonable debt levels by most measures, increase in net income, good cash flow from operations and growth in earnings per share. Although the company may harbor some minor weaknesses, we feel they are unlikely to have a significant impact on results. Get the full Sirona Dental Systems Ratings Report now. Exclusive Offer: Jim Cramer's 'go-to' small/mid-cap guru Bryan Ashenberg only buys stocks he thinks could return 50-100%. See his top picks for 14-days FREE.