➡️ 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…
Hereditary enamel dysplasia
Hereditary brown enamel
Hereditary brown opalescent teeth
Prevalence: 1 in 700 to 1 in 15,000
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:
Formative – deposition of organic matrix
Calcification – Matrix mineralization
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
Snow-capped teeth, X-linked
🔹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
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.
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.
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.
Hypoplastic: Disturbance in the differentiation/viability of Ameloblasts. Defect in matrix formation.
Hypomaturation: Alteration in enamel rod & rod sheath structures.
Hypocalcified: Defects of matrix structure & of mineral deposition.
References: Shafer’sTextbook Of Oral Pathology; Internet