A spontaneous novel mutation in COL1A2 (c.1171G>A; p.Gly391Ser) causing only dentin defects and a novel mutation in PAX9 (c.43T>A; p.Phe15Ile) causing hypodontia were identified and correlated with the phenotypic presentations in the family. This evidence concerns the gene COL1A2 and tooth agenesis.