Among rare diseases, a fifth of them are associated with oral manifestations. The most frequent are: enamel dysplasia, cleft lip or palate and oligodontia. Beside the pathology, patients are eager of functional therapeutics which often needs prosthodontics. This oral rehabilitation aims to a better life quality.

Teeth absence management in the case of oligodontia necessitates critical analysis of the supporting tissues: the periodontium and the underlying bone. Deciduous teeth with resorbed roots and hypoplasic permanent teeth are often observed. Thus, some questions arise: can we use them as abutments or can we restore them knowing that they present an anomaly in their position and are more fragile? How do we replace many teeth when bone is lacking (clefts, agenesis)? Can we implant on a missing tooth site or can we use autograft? What do we expect for periodontal healing?

Adjacent teeth have often migrated, occlusion is unstable due to mixed dentition and patient’s disease. For example, in mandibular incisors agenesis cases, the remaining deciduous teeth are used when consultation happens at adolescence. This results in upper jaw incisors migration toward mandible and thus an anterior overbite. Orthodontic treatments will allow to recreate gap width and a normal occlusion in order to perform prosthodontics treatment in the best possible conditions. Giving the weak dental and periodontal supports, our attention will be focused on choosing the best option between tooth and implant supported prosthodontics. During the mixed dentition, orthodontic treatment and aesthetic rehabilitation have to be planed at the same time and to last until “definitive” implant and periodontal therapies are possible. In this article, we will present one oligodontia case report to illustrate a possible solution.

The dental surgeon can feel inadequate when confronted with a rare disease: (a) difficult diagnosis, (b) therapeutic complexity, (c) and questioning by the parents, are three major obstacles that we have to overcome in order to carry out our therapy. Even if the field of genetics has made major advances during the last few years, it is clinical knowledge, above all, that leads us to a diagnosis. Certain syndromes present with very subtle signs which alone can appear trivial but which, taken together, defines a pathological entity. To know or to discover these signs and to recognize them is therefore the first challenge.

Hypohidrotic ectodermal dysplasias (HED) are a heterogeneous and complex group of syndromes characterized by a dental craniofacial phenotype associated with severe oligodontia, maxillary hypoplasia with broad face and most notably facial concavity. Cephalometric analyses show insufficient maxillary sagittal growth, a protruded mandible, reduced facial and ramus heights, as well as basicranial changes. Early diagnosis and care from a multidisciplinary team are essential. In the primary dentition, initial prosthetic treatment is recommended and may possibly be combined with interceptive orthodontic treatment. In the mixed dentition, treatment of a transverse maxillary deficiency consists in installing a removable expander or a quadhelix in the case of moderate phenotypes where there is adequate anchorage support. To achieve mandibular anterior repositioning of the maxilla the patient must wear a facial mask. In the permanent dentition, the important steps are correlated with the pre-implant and pre-prosthetic orthodontic adjustments, as well as the presurgical orthodontic preparation that precedes subsequent single or double jaw orthognathic surgery. Temporary skeletal anchorage with mini-screws or plates can be used in cases of insufficient anchorage.