• Faciogenital dysplasia (Aarskog’s syndrome)
• Cornelia de Lange syndrome
• Schinzel–Giedion syndrome
• Prader–Willi syndrome
• Otodental syndrome
• Robinson’s syndrome
• Amelo–onychohypohidrotic dysplasia
Complications
• Usually, severe dental crowding in the affected area.
Treatment
• In case of delayed tooth eruption caused by local etiological factors, removal of the factor and orthodontic evaluation followed by surgical or orthodontic treatment, or both, when needed.
Ankylosis
Definition
• Ankylosis appears clinically as an eruption defect, frequently followed by irregular occlusion. It is characterized by occlusal surface retention of the affected teeth, at a level at least 1 mm or more cervical to the adjacent teeth (Fig. 1.23).
Etiology
• The defect is caused by local traumatic and metabolic factors, whereas genetic factors have also been implicated. It is the result of continuing eruption of the adjacent teeth in contrast to the immobilization of the affected teeth.
Occurrence in children
• Primary teeth 1.3–9.9%.
• Coexistence of missing successors 11–20%.
• Permanent teeth, rare compared to primary (1:10).
Localization
• Primary and permanent molars.
• More frequently in the mandible.
• Frequently a bilateral finding.
Clinical features
• Occlusal surface at least 1 mm cervically compared to adjacent teeth.
• Sharp, clear sound on percussion.
• Absence of regular mobility.
• Three clinical forms: mild, moderate, severe.
Radiological features
• Break of periodontal membrane continuity.
• Absence of findings in ankylosed buccal and lingual surfaces.
• Findings in 30% of the cases with ankylosed proximal surfaces (Figs. 1.24, 1.25).
Complications
• In moderate and severe cases, the defect usually causes orthodontic disturbances in the involved area, resulting from malalignment of the adjacent and opponent teeth.
Treatment
• Depending on the severity of the ankylosis, a) follow-up of the resorption rate of the ankylosed tooth and possible build-up; b) mechanical luxation;c) extraction and orthodontic treatment.
Fig. 1.21 Eruption delay of upper central incisors due to impacted odontomas and supernumerary teeth
Fig. 1.22 Eruption delay of upper and lower anterior teeth due to impacted supernumerary teeth in a patient with cleidocranial dysplasia
Fig. 1.23 Radiological features of moderate ankylosis of a lower second primary molar
Early Exfoliation
Definition
• Refers to early loss of either primary or permanent teeth.
Etiology
• The condition results frequently from trauma, periodontal disease, and extraction due to caries. However, some genetic and systemic disorders may cause early loss of teeth as a result of damage to either soft periodontal tissue or bone (Fig. 1.26).
Genetic/systemic disorders
• Prepubertal periodontitis
• HIV periodontitis
• Hypophosphatasia
• Acatalasia
• Papillon–Lefevre syndrome
• Gingival fibromatosis and hypertrichosis
• Oculodentodigital syndrome, type I
• Ehlers–Danlos syndrome, type VIII
• Progeria
• Vitamin D–resistant rickets
• Diabetes mellitus
• Glycogen storage disease, Type Ib
• Langerhans cell histiocytosis
• Cyclic neutropenia
• Leukemia
• Inherited immunodeficiencies
• Acrodynia
• Neoplasms
• Hajdu–Cheney syndrome
• Chediak–Higashi syndrome
• Ellis–van Creveld syndrome
Enamel Defects
These defects result from the action of various etiological factors during the apposition and mineralization stages of dental development.
Fig. 1.24 Radiological features of severe ankylosis of a lower first permanent molar
Fig. 1.25 Radiological features of mild and moderate ankylosis of the upper and lower primary molars
Fig. 1.26 Early exfoliation of an upper primary molar due to periodontitis in a patient with cyclic neutropenia
Definition
• The range of enamel defects covers a group of defects clinically recognizedas enamel hypoplasia, hypocalcification, hypomaturation (demarcatedand diffuse enamel opacities), or a combination of the former, dependingon the phase of amelogenesis that the etiological factor acts on.
Etiology
• Defective formation of the enamel matrix results in hypoplasia; defective calcification of an otherwise normal quantity of organic matrix results in hypocalcification; and defective formation of the crystallites in various