Occurrence in children
• Frequent in primary dentition (33%).
• Frequent in cases of local etiology; 12–23% in permanent teeth following trauma or chronic inflammation in the predecessor primary teeth.
• Frequent in cases of systemic etiology; 71 % in children with a history of prenatal insult.
• Approximately 70 genetic disorders are associated with enamel defects.
Localization
• In cases of local etiology, mainly in permanent incisors and premolars.
• In cases of systemic etiology, mainly in the primary molars and permanent incisors and molars, but also in all the teeth developing during the period of action of the etiological factor.
• In cases of genetic etiology, all teeth in both primary and permanent dentitions may be involved.
Clinical features
• Hypoplasia, pits, grooves, and lines in the whole enamel surface or in certain areas. Possible reduction of the enamel thickness (Figs. 1.27–1.29).
• Hypocalcification, soft enamel of yellow-brownish color, easily removed by probing in isolated areas of the enamel, enamel attrition, sensitivity in thermal stimuli (Figs. 1.30, 1.31).
• Hypomaturation (opacities), dull enamel with mottled, white, opaque appearance and regular thickness, reduced hardness and possible microfractures (Fig. 1.32).
Complications
• Occasional occlusal distortion, aesthetic problems, sensitivity.
Treatment
• Conservative aesthetic restorations, prosthetic rehabilitation.
Fig. 1.27 Enamel hypoplasia and hypomineralization of all the primary teeth (chronological) resulting relaxing medicines during pregnancy
Fig. 1.28 Enamel hypoplasia and hypomineralization of an upper central incisor due to mechanical trauma of the predecessor primary tooth
Fig. 1.29 Enamel hypoplasia of all the permanent teeth (chronological), resulting from prolonged use of medicines for chronic nephritic syndrome
Amelogenesis Imperfecta
Definition
• The term "amelogenesis imperfecta" characterizes isolated defects of the enamel resulting exclusively from genetic factors and not associated with generalized genetic disorders and syndromes. This proposed terminology has been questioned recently, since other local abnormalities associated with amelogenesis imperfecta have been found, such as skeletal anterior open bite. In addition, the assumption of an isolated enamel defect in amelogenesis imperfecta may not be correct, since it depends on the clinician’s ability to diagnose other abnormalities else-where in the body.
Etiology
• The defect results from genetic factors acting during embryogenesis, particularly in the phases of enamel formation.
• Recently, it has been suggested that the anomaly results from a defect in the enamel matrix proteins amelogenin and enamelin. The amelogenin gene has been located in the p22.1–22.3 region of the X chromosome and in the pericentromeric region of the Y chromosome. The X-linked types of amelogenesis imperfecta are therefore strongly associated with a molecular defect in this locus.
• They are classified into many types, according to their clinical features and mode of inheritance.
Classification
Type I, hypoplastic
• la: pitted hypoplastic, autosomal dominant (Fig. 1.33)
• lb: local hypoplastic, autosomal dominant (Fig. 1.34)
• Ic: local hypoplastic, autosomal recessive
• Id: smooth hypoplastic, autosomal dominant (Fig. 1.35)
• Ie: smooth hypoplastic, X-linked dominant
• If: rough hypoplastic, autosomal dominant (Fig. 1.36)
• Ig: rough hypoplastic (enamel agenesis), autosomal recessive
Type II, hypomature
• Ila: hypomature pigmented enamel, autosomal recessive
• lib: hypomature enamel, X-linked recessive (Fig. 1.37)
• lie: snow-capped enamel, autosomal dominant
Type III, hypocalcified
• Ilia: hypocalcified enamel, autosomal dominant (Fig. 1.38)
• Illb: hypocalcified enamel, autosomal recessive (Fig. 1.39)
Type IV, hypomature-hypoplastic with taurodontism
• IVa: hypomaturation-hypoplasia with taurodontism, autosomal dominant
• IVb: hypoplasia-hypomaturation with taurodontism, autosomal dominant
Occurrence in children
• One per 4000–8000, all types
• 60–73% of the total hypoplastic types, 20–40% hypomaturation types, 7% hypocalcified types
Localization
• All teeth, primary and permanent
Clinical features
Hypoplasia
• Normal or reduced enamel thickness throughout the whole surface, or in isolated areas.
• Enamel pits, grooves, fissures and linear depressions randomly distributed over the entire enamel surface.
• Hard enamel with a normal or slightly yellow-brown color.
• Frequent microfractures of the enamel, and possible attrition.
• Types Id, Ie, and If appear clinically as
