5 Important Genetic Causes of Multiple Malformed Permanent Teeth

• Amelogenesis Imperfecta
  • Hypoplastic (type 1)
  • Hypomaturation (type 2)
  • Hypocalcified (type 3)

• Dentinogenesis Imperfecta
  • Shell teeth

• Dentinal Dysplasia

• Regional Odontodysplasia

• Multisystem Disorders with Associated Dental Defects

Amelogenesis Imperfecta

Amelogenesis imperfecta is a group of conditions caused by defects in the genes encoding enamel matrix proteins. Classification is complex and based on pattern of inheritance, enamel hypoplasia, hypomineralisation or hypomaturation and appearance; smooth, rough or pitted.

Hypoplastic Amelogenesis Imperfecta

The main defect is in formation of the matrix. The enamel is randomly pitted, grooved or very thin, but hard and translucent (Figure 3). The defects tend to become stained, but the teeth are not especially susceptible to caries unless the enamel is scanty and easily damaged.

Figure 3. Amelogenesis imperfecta, hypoplastic pitted type

Hypomaturation Amelogenesis Imperfecta

The enamel is normal in form on eruption but opaque, white to brownish-yellow. The teeth appear similar to mottled fluoride effects (Figure 5). However, they are soft and vulnerable to attrition, though not as severely as the hypocalcified type.

Figure 5. Amelogenesis imperfecta, hypomaturation type. Tooth morphology is normal but there are opaque white and discoloured patches

Hypocalcified Amelogenesis Imperfecta

Enamel matrix is formed in normal quantity but poorly calcified. When newly erupted, the enamel is normal in thickness and form, but weak and opaque or chalky in appearance.

Figure 6. Amelogenesis imperfecta, hypocalcified type. The soft chalky enamel was virtually of normal thickness and form but has chipped away during mastication

Dentinogenesis (odontogenesis) Imperfecta

This uncommon defect of collagen formation is transmitted as an autosomal dominant trait. The enamel appears normal but uniformly brownish or purplish and abnormally translucent.

Figure 7. Dentinogenesis imperfecta showing the translucent appearance of the teeth which are of normal morphology

Shell teeth (dentinogenesis Imperfecta type 3)

This rare anomaly is so called because only a thin shell of hard dental tissue surrounds overlarge pulp chambers. Like other types of dentinogenesis imperfecta there is normal, but thin, mantle dentine which covers irregular dentine.

Figure 8. Shell tooth. In this severe form of dentinogenesis imperfecta only a thin mantle of dentine is formed and no root develops

Dentinal Dysplasia (‘rootless’ teeth)

In dentinal dysplasia, the roots are very short and conical. The pulp chambers are obliterated by multiple nodules of poorly organized dentine containing sheaves of tubules.

Regional Odontodysplasia (ghost teeth)

This is a localized disorder of development affecting a group of teeth in which there are severe abnormalities of enamel, dentine and pulp.

Multisystem Disorders Affecting the Teeth

Ehlers-Danlos (floppy joint) syndromes

This group of collagen disorders is characterized (in varying degree), by hypermobile joints, loose hyperextensible skin, fragile oral mucosa and, in type VIII, early onset periodontitis.

Figure 9. Multiple pulp stones in a case of Ehlers-Danlos syndrome

Gardner’s syndrome (familial adenomatous polyposis)

Gardner’s syndrome is characterized by multiple osteomas, especially of the jaws, colonic polyps and skin tumors. The majority of patients have dental abnormalities. These include impacted teeth other than third molars, supernumerary or missing teeth and abnormal root formation.

Epidermolyis bullosa

Epidermolysis bullosa is a blistering disease of skin and mucosae. Dental abnormalities include fine or coarse pitting defects, or thin and uneven enamel which may also lack prismatic structure. The amelodentinal junction may be smooth. Dental defects vary in the different subtypes of the disease but are most frequent in the autosomal recessive, scarring type of epidermolysis bullosa in which there may be delayed, or failure of, eruption.