PAX9 and Oligodontia: At least eight genes have been identified as the major causes of non-syndromic oligodontia (NSO): MSX1 (Zheng et al., 2021), PAX9 (Sun et al., 2021), AXIN2 (Wong et al., 2014), WNT10A (Arzoo et al., 2014), LRP6 (Massink et al., 2015), EDA (Zhang et al., 2020), EDAR (Zhang et al., 2021), and WNT10B (Yu et al., 2016).