The crown of a tooth is composed of enamel and dentin. The enamel is the outer layer of a whitish color mostly composed of hard anorganic substance - over 96% and organic matter and water - less than 4%. This layer is much tougher and more resistant than the inside dentin that has a yellowish color and represents only 45% hard anorganic substance, the rest being 33% organic matter and 22% water.
Amelogenesis is the formation of dental enamel and begins when the crown forms within the maxillary bones, after the dentinogenesis (formation of the first dentin layer) and before tooth root formation.
Amelogenesis Imperfecta is a rare congenital disorder in which the teeth exhibit an abnormal development and mineralization of enamel unrelated to other systemic or general diseases. It is due to the malfunction of the enamel proteins (ameloblastin, enamelin, tuftelin and amelogenin) and results in a lower concentration of the anorganic substance in the enamel and low resistance to chemical and physical factors in the oral cavity.
Patients with this condition have an abnormal color of the teeth (yellow, brown or gray), and may have signs of the disease on all teeth or only a part of them. The disease is manifested in a variety of ways, depending on the type of amelogenesis, with defects in the shape or volume of the teeth. Teeth are hypersensitive to temperature variations, more susceptible to cavities, rapid wear (abrasion, bruising), excessive tartar and gingival hyperplasia.
Signs may arise from the teeth eruption period, but in the case of permanent teeth they become more apparent between 20 and 30 years, and the progression of the disease even results in the total loss of dental crowns after the age of 30.
All types of amelogenesis imperfecta are caused by genetic mutations, most of which are inherited from the patient's parents. When the disease is inherited, affected males have more dental anomalies and more severe signs than affected females.
Cases can be classified according to their clinical appearance in:
• Type 1 - Hypoplasia
The enamel has a normal density but an abnormal thickness due to the malfunctioning of its matrix formation. It is very thin, but tough and transparent and may have random grooves and pits. The teeth are smaller and can have spaces between them. Mineralization and color are normal but, due to lower thickness, the teeth may appear more closed (the dentin transpires through the smallest enamel). Over time, the color of the teeth will change. Radiologically, the enamel density is similar to that normally developed and different from dentin.
• Type 2 - Hypomaturation
Enamel has a normal thickness but abnormal density and mineralization. It is less tough compared to ordinary enamel and prone to rapid wear, but not as intense as type 3. Color can range from normal to yellow-brown. Radiologically, the density of the enamel is lower than normal enamel dentin.
• Type 3 - Hypocalcified
Enamel has a normal thickness but is defective so extremely fragile, less resistant than dentine and has a snowy/chalky appearance (white opaque). Teeth are prone to color change and rapid wear, exposing the inside dentine. Radiologically, the enamel density of these teeth is lower than the dentin.
• Type 4 - Hypoplasia-Hypomaturation with Taurodontism
The enamel has a mixed appearance with characteristics from AI type 1 and type 2. All type 4 affections have Taurodontism, a condition characterized by the presence of vertically enlarged molars crowns and reduced-sized roots, with a larger than normal pulp chamber. They can also be associated with an open bite.
Prophylactic and restorative dental treatments are very important as well as solving aesthetic problems, teeth becoming yellow or brown rapidly from dentin exposure due to enamel loss. The main objectives of the treatment are to relieve pain, save the remaining teeth of the patient and maintain his occlusal vertical height.
Several factors need to be considered before deciding on a treatment solution such as classification and severity of the disease, patient's social history, clinical appearance etc. Although there are several types of amelogenesis imperfecta, the general approach of this disorder is similar.
In the early stages of the disease, the fluoridation of affected areas to diminish the patient's sensitivity and dental veneers to protect the enamel against abrasion may be a temporary treatment.
In the more advanced disease situations, dental prosthetic crowns are needed to compensate enamel's abrasion, sometimes with pre-prosthetic devitalization of teeth (root canals on the most affected teeth). These crowns not only protect the teeth and treat the patient's sensitivity but also maintain the occlusal vertical dimension which, being prone to shrinking, can give the patient an older appearance.
To see some situations where amelogenesis imperfecta treatments have been succesfully applied visit Clinical Cases.