Oligodontia

Oligodontia is a rare developmental dental anomaly in humans characterized by the absence of six or more teeth.

Epidemiology

The prevalence of isolated oligodontia is unknown. In European populations the estimated prevalence of both syndromic and non-syndromic oligodontia varies from 1/625 to 1/1,250 depending on the studies.

Clinical description

Clinical features of oligodontia include six or more missing teeth, lack of development of maxillary and mandibular alveolar bone height and reduced lower facial height. Variation in tooth morphology is also observed along with problems in tooth development, eruption and exfoliation.

Etiology

Possible causes of oligodontia include viral disease during pregnancy, genetic predisposition, metabolic imbalances, developmental abnormalities and environmental factors. Autosomal dominant mutations in PAX9 and MSX1 have been found in patients with molar non-syndromic oligodontia. The most recent gene identified as causing oligodontia is an autosomal recessive mutation in LTBP3 which was found in one case. WNT10A gene mutations, responsible for autosomal recessive forms of HED, odonto-onycho-dermal dysplasia and Schöpf-Schulz-Passarge syndrome (see these terms) are also seen in a substantial proportion (30 to 50% cases according to studies) of non-syndromic oligodontia cases. EDA and EDARADD, genes involved in different forms of X-linked and hypohidrotic ectodermal dysplasia (HED, see this term), are also mutated in non-syndromic oligodontia. The dental phenotype associated with autosomal dominant HED is usually less severe than that seen in autosomal recessive HED. Oligodontia-cancer predisposition syndrome (see this term) is due to AXIN2 gene mutations. IKBKG gene mutations are also associated to syndromic oligodontia, observed in incontinentia pigmenti and HED with immunodeficiency (see these terms).

Diagnostic methods

Clinical examination along with a panoramic radiograph (and intra-oral X-rays if needed) is performed when teeth are thought to be missing. Delayed eruption of teeth, persistence of primary teeth, alveolar bone hypotrophy, and the presence of diastemas all suggest a diagnosis of oligodontia. In normal conditions all primary teeth and crypts of permanent first molars are visible on radiography at birth and crowns of permanent teeth (except third molars) at 6 years of age. When more than six teeth are absent then a diagnosis of oligodontia is given.

Differential diagnosis

Isolated oligodontia should be distinguished from syndromic forms. Oligodontia is seen in X-linked hypohidrotic ectodermal dysplasia with immunodeficiency (HED), ECC syndrome, orofaciodigital syndrome type I and oral facial clefting syndromes such as Van Der Woude syndrome, Ellis-Van Creveld syndrome or Rapp-Hodgkin syndrome, hidrotic ectodermal dysplasia, focal facial dermal dysplasia (see these terms), oligodontia-taurodontism-hypotrichosis syndrome or trichothiodystrophies.

Antenatal diagnosis

Genetic antenatal diagnosis is possible but is never performed.

Genetic counseling

Genetic counseling is necessary to exclude syndromic oligodontia and discuss issues related to inheritance.

Management and treatment

Treatment of oligodontia requires a multidisciplinary approach. Prosthetic treatment includes removable partial dentures, fixed partial dentures and over dentures. Osseointegrated dental implants are also possible when there is adequate bone height as they offer a more stable, long-term solution. Early implant therapy consists of the placement of 2 symphyseal implants from the age of 6 years old, allowing for the stabilization of a mandibular prosthesis that will be modified regularly to follow mandibular bone growth. Maxillary implants are placed upon the completion of skeletal growth.

Prognosis

With proper dental treatment, patients can have normal dentition and orofacial functions