Church & Dwight Co. announced a voluntarily recall of its Arm & Hammer Spinbrush Rechargeable SONIC toothbrushes because the charging base may overheat with localized melting and sparking, possibly causing fire, shock or burns.

In a news release, the company said the risk of the malfunctions appears to increase with the age of the product. To date, Church & Dwight said it has received six consumer reports of overheating in the U.S. and one consumer report in Canada. There have been no reported injuries.

The recall is limited to select Spinbrush toothbrushes with lot numbers: DD9310 to 9365 or DD0002 to 0122. The lot number can be found on the bottom of the charging base and on the packaging.

The company said products with lot numbers outside of these ranges are not at risk and are not subject to the recall.

The Spinbrush battery-powered or Spinbrush SONIC battery-operated toothbrushes do not have a charging base with an electric cord and plug and are not subject to the recall.

The indicated lots were sold between February 2010 and October 2011 in all U.S. states and in Canada.

Consumers who have the affected units are urged to stop using them and to call Church & Dwight at 888-709-4100 for a full refund.