➡️ Represents a group of hereditary defects of enamel unassociated with any other generalized defects. It is entirely an ectodermal disturbance, since the mesodermal components of the teeth are basically normal.

➡️ Otherwise known as…

• AI
• Hereditary enamel dysplasia
• Hereditary brown enamel
• Hereditary brown opalescent teeth

Prevalence: 1 in 700 to 1 in 15,000

Etiology:

• Dental enamel is a highly mineralized tissue with over 95% of the volume occupied by unusually large, organized structures called the hydroxyapatite crystals.
• The formation of these is controlled in Ameloblasts through the interaction of a no. of organic matrix molecules that include –

Develoment of Enamel:

➡️ 3 stages:

1. Formative – deposition of organic matrix
2. Calcification – Matrix mineralization
3. Maturation – Crystallites enlarge & mature

Types of AI classification (Witkop and Sauk)

Based on clinical, histological & genetic criteria:

🔹 TYPE I HYPOPLASTIC

• Pitted Autosomal dominant
• Local Autosomal dominant
• Local Autosomal Recessive
• Smooth Autosomal dominant
• Smooth, X-linked dominant
• Rough Autosomal dominant
• Enamel agenesis, Autosomal Recessive

🔹 TYPE II HYPOMATURATION

• Diffuse Pigmented, Autosomal Recessive
• Hypomaturation
• Snow-capped teeth, X-linked
• Autosomal Dominant

🔹 TYPE III HYPOCALCIFICATION

• Diffuse Autosomal dominant
• Diffuse Autosomal Recessive

🔹 TYPE IV COMBINATION TYPE

• Hypomaturation – Hypoplastic with taurodontism
• Hypomaturation – Hypoplastic with taurodontism, Autosomal Dominant
• Hypoplastic – Hypomaturation with taurodontism, Autosomal Dominant

Clinical Features:

1) Hypoplastic – Enamel not formed to full normal thickness.

2) Hypomaturation –

• The enamel can be pierced by an explorer point under firm pressure.
• Can be lost by chipping away from the underlying normal appearing dentin.
• Teeth normal in shape but exhibit a mottled, opaque white, brown-yellow discoloration.
• Snow capped pattern – Zone of white opaque enamel on the incisal or occlusal third of crown.

3) Hypocalcified –

• The enamel is so soft that it can be removed by a prophylaxis instrument.
• Yellow, brown or orange on eruption. Stained brown to black with time.
• Rapid calculus apposition.
• Coronal enamel lost with function except for the cervical portion which is mineralized better.
• Autosomal Recessive – More severe.

Other Features:

• Both dentition affected
• Crown – Yellow to dark brown
• Enamel might have numerous parallel vertical wrinkles or grooves.
• Open Contact points.
• Occlusal & incisal edges frequently abraded.

Radiographic Features:

• The enamel may appear totally absent.
• When present may appear as a thin layer, chiefly over tip of cusps & on inter-proximal surfaces.
• In some cases, calcification is so much affected that enamel and dentin seem to have the same radio density, making differentiation b/w the two difficult.

Histological Features:

1. Hypoplastic: Disturbance in the differentiation/viability of Ameloblasts. Defect in matrix formation.
2. Hypomaturation: Alteration in enamel rod & rod sheath structures.
3. Hypocalcified: Defects of matrix structure & of mineral deposition.

Management:

• Sealants/bonding
• Prosthetic reconstruction

References: Shafer’sTextbook Of Oral Pathology; Internet