The occurrence of a single median maxillary central incisor (SMMCI) is a very rare condition and might be a sign of a more severe midline defect, which could be a mild degree of holoprosencephaly. Absence of the internasal and partial absence of the intermaxillary suture has been observed in a fetus with holoprosencephaly. The purpose of this study was to evaluate the intermaxillary suture, the eruption pattern of the single central incisor in the SMMCI condition, and the growth of the maxilla in a group of patients with SMMCI. A similar study was not found in the scientific literature. The material included orthopantomographs, dental radiographs, and lateral cephalometric radiographs from 11 patients with an SMMCI. The orthopantomographs and dental radiographs showed that the intermaxillary suture was abnormal anterior to the incisive foramen; however, the SMMCI erupted within the expected time interval. Superimposition on stable structures on lateral cephalometric radiographs from two untreated patients, in which growth analysis was possible, showed that the horizontal and vertical growth of the maxilla was normal. Due to the sutural midline defect it is suggested that a transversal growth analysis is included in all treatment planning of SMMCI patients.