Amelogenesis imperfecta
Amelogenesis imperfecta (AI) represents a group of developmental conditions affecting the structure and clinical appearance of the enamel of all or nearly all the primary or permanent teeth. Diagnosis is based on the family history, pedigree plotting and meticulous clinical observation. At present, genetic diagnosis is only available as a research tool.

Dentinogenesis imperfecta and dentin dysplasia
Dentinogenesis imperfecta and dentin dysplasia are diseases characterized by an abnormal formation and thus abnormal structure of the dentin, generally affecting both primary and permanent teeth.

Oligodontia is a dental abnormality in which the patient is missing teeth. It is a hereditary disorder characterized by agenesis of more than 6 primary/permanent teeth, excluding the wisdom teeth.
Not only the number of missing teeth, but also the type of missing teeth, must be considered. The teeth most often absent are the terminal teeth of a series (premolars (32% to 15%), maxillary lateral incisors (27%) and third molars (25%). The canines, first and second molars (1%) and maxillary central incisors (0.05%) are rarely absent; particular attention must be paid to this sign. The type of teeth that are missing is not coincidental; rather, it is directly related to the dentition pattern.

Early loss of primary and/or permanent teeth
Either partial or generalized early loss of primary and/or permanent teeth,
whether associated with an inflammatory and infectious context or not, in children and young adults, is always the warning sign of an underlying systemic disease such as, for example, hypophosphatasia or immune deficiencies found in cyclic neutropenia, Papillon-Lefèvre syndrome, Chédiak-Higashi syndrome or Ehlers-Danlos syndrome (VIII, IV).

Solitary median maxillary central incisor syndrome
Solitary median maxillary central incisor (SMMCI) syndrome is a developmental defect of the median line of the craniofacial bones and a minor clinical manifestation of holoprosencephaly (cerebral disorder).