Congressmen and veterans took turns lambasting the Veterans Administration Tuesday for its handling of medical-safety failures at John A. Cochran Medical Center that may have exposed 1,812 veterans to infectious diseases. The House Committee on Veterans Affairs held a special hearing at the U.S. Courthouse downtown to examine lapses in the dental clinic at the hospital in midtown St. Louis. Failure to properly clean instruments in the dental clinic put the veterans at risk of contracting hepatitis B, hepatitis C and HIV.