Orthodontic Centers of America ( OCA) reported a drop in first-quarter earnings, but said it believes business has stabilized after its acquisition of OrthoAlliance. Including certain charges, the company earned $14.9 million, or 30 cents a share, in the quarter ended March 31, compared with $18.5 million, or 36 cents a share, in the prior-year quarter. The company said results exclude temporary benefits received in the first quarter of 2002 from departed OrthAlliance practices. "With all of the changes and dramatic growth that we have gone through in the last two years, the company is the strongest that it has ever been," said Bart Palmisano, chief executive. The company said it hopes to expand its affiliated practices. As of March 31, Orthodontic Centers said it was affiliated with 371 practices. Total quarterly sales were $100.6 million, down from last year's $111.3 million. Shares of the Metairie, La.-based company closed at $7.27 Thursday.