 In the United States, although toothbrushes were available at the end of the 19th century, the practice did not become widespread until after the Second World War, when US soldiers continued the toothbrushing that had been required during their military service..
<fluency>  In the United States, although toothbrushes were available at the end of the 19th century, the practice did not become widespread until after the Second World War, when US soldiers continued the toothbrushing that had been required during their military service..
 In the United States, although toothbrushes were available at the end of the 19th century, the practice did not become widespread until after the Second World War, when US soldiers continued the tooth brushing that had been required during their military service..