Sirona Dental Systems Inc. said Friday that profit dropped almost by half in its fiscal fourth quarter due to foreign exchange effects on its international businesses and other one-time charges.

Excluding those charges, profit increased on stronger sales in several of its businesses including imaging systems, design and manufacturing systems and instruments.

The Long Island City, N.Y., dental equipment maker reported earnings of $13.8 million, or 24 cents per share, for the July-September period. That compares with $24.7 million, or 44 cents per share, for the same part of 2010. Revenue increased 19.6 percent in the quarter to $218.8 million.

Excluding special charges, Sirona said it earned 68 cents per share, up from 44 cents per share in the same part of 2010.

Analysts, who typically exclude special items, had expected earnings of 61 cents per share on sales of $212.9 million, according to FactSet.

Sirona said revenue climbed 43 percent in its imaging systems business, 11 percent for computer-aided design and manufacturing systems, 11 percent in its instruments business and 2.7 percent in treatment centers. Revenue increased 14 percent in the U.S. and 22 percent internationally.

For the full year, Sirona earned $121.8 million, or $2.13 per share, compared with $90 million, or $1.59 per share, for 2010. Annual revenue increased 18.6 percent to $913.9 million.

The company expects to boost revenue by 6 to 8 percent in 2012, while increasing operating income to between $225 million and $234 million.

Analysts expect 2012 revenue of $974.3 million, which implies growth of 6.6 percent from this year.