2.1 | Subjects and ethical approval
The study involved four non-consanguineous patients with NSTA who were referred to the Department of Prosthodontics, School and Hospital of Stomatology of Hebei Medical University, and 100 non-consanguineous controls. All participants were examined by prosthodontics specialists to determine the status of dentition. An oral examination and a dental treatment history were performed, and panoramic radiographs were taken to confirm the congenital absence of teeth (Figure 1). The study was conducted under the approval of the Ethics Committee of the School and Hospital of Stomatology, Hebei Medical University (NO: [2016] 004). All participants or their guardians signed written informed consent.