Cyclin-Dependent Kinase Inhibitor p21/metabolism; Embryonic Stem Cells/cytology; Embryonic Stem Cells/metabolism; Homeodomain Proteins/metabolism; T-Box Domain Proteins/genetics; T-Box Domain Proteins/metabolism; Tooth/embryology; Transcription Factors/metabolism; Animals; Base Sequence; Cell Proliferation; Cyclin-Dependent Kinase Inhibitor p21/genetics; DNA Primers/genetics; DiGeorge Syndrome/embryology; DiGeorge Syndrome/genetics; Disease Models, Animal; Epithelium/embryology; Epithelium/metabolism; Female; Gene Expression Regulation, Developmental; Homeodomain Proteins/genetics; Humans; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Mice, Transgenic; Odontogenesis/genetics; Odontogenesis/physiology; Pregnancy; Signal Transduction; T-Box Domain Proteins/deficiency; Tooth/cytology; Tooth/metabolism; Tooth Abnormalities/embryology; Tooth Abnormalities/genetics; Transcription Factors/deficiency; Transcription Factors/genetics; Transcriptional Activation; Homeobox Protein PITX2