Structured AbstractObjectiveTo investigate phenotypic differences in dental development between isolated oligodontia and oligodontia‐ectodermal dysplasia (ED).Setting and sample populationA total of 129 patients diagnosed with isolated oligodontia and 22 patients with oligodontia as part of ED were eligible.MethodsThe phenotype of dental development was assessed for the frequency of missing a certain tooth, dental age, development of each tooth present, abnormal size and abnormal shape of teeth. The data were analysed building linear, ordinal and logistic regression models.ResultsCompared to patients with isolated oligodontia, patients with oligodontia‐ED missed more frequently central incisors and second molars in both jaws, and lateral incisors in the mandible (P < .05). Oligodontia‐ED was associated with delayed development of the permanent dentition (β = −0.10; 95% CI: −0.17, −0.03). Specifically, the maxillary teeth: right central incisor, right lateral incisor, right second premolar and left second premolar were delayed approximately from 2 to 4 developmental stages. In addition, the left mandibular second premolar was 3 developmental stages delayed. Abnormal shape of teeth was 7 times more evident in patients with oligodontia‐ED compared to patients with isolated oligodontia (OR = 6.54; 95% CI: 2.34, 18.28). The abnormal size of teeth was not a distinctive characteristic for oligodontia‐ED.ConclusionsOligodontia‐ED distinguishes from isolated oligodontia by more disturbances in dental development. The abnormal shape of incisors and canines in a patient with oligodontia can raise suspicions for accompanying ectodermal abnormalities.