Dentition mammals the infants have a set of teeth that fall out and are replaced by adult teeth. These are called deciduous teeth, primary teeth, baby teeth or milk teeth. Animals that have two sets of teeth, one followed by the other, are said to be diphyodont. Normally the dental formula for milk teeth is the same as for adult teeth except that the molars are missing. Because mammal teeth are specialised for different functions, many mammal groups have lost teeth not needed in their adaptation. Tooth form has also undergone evolutionary modification as a result of natural selection for specialised
U Should've Known Better song entered the "Billboard" Hot 100 chart, where it debuted at number 67 in the week of June 6, 2004, the second-highest debut of the week. "U Should've Known Better" remained twenty weeks on the chart, reaching its peak position of number 19 in its ninth week. It marked the second single from "After the Storm" to reach the top twenty on the Hot 100chart and, as the album's final single, would remain its second highest-charting offering behind leading single "So Gone." Although never released on a CD single or CD maxi single format, "U Should've Known Better" was also