There are two limitations for this study: (1) while the study suggests an important role for SIRT1 in DD, it should be noted that this disorder represents a polygenic phenotype and that many other loci remain to be discovered beyond SIRT1; (2) the quality of experienced early environment (e.g., parental care, exposure to childhood abuse) was not evaluated in the DD group. The gene discussed is SIRT1; the disease is dentin dysplasia.