1
S by enzymes, e.g., enamelysin (matrix metalloproteinase 20, Mmp-20) and kallikrein 4 [49]. The ways in which these proteins guide the formation of HA in enamel is unknown. There are, however, some important clues from recent studies. In the teeth of mice that produce a truncated form of ameloblastin, enamel fails to appear [50,51]. These mice also have reduced expression of amelogenin with no app