Amelogenesis imperfecta

Question 1

What is amelogenesis imperfecta?

Answer 1

A group of conditions genomic in origin which affect the clinical structure, and appearance of enamel in all or nearly all teeth and may be associated with morphological or biochemical changes.

Question 2

How is amelogensis imperfecta classified?

Answer 2

Based on phenotype: Hypocalcified, hypoplastic and hypomature

Question 3

What is the prevalence of amelogensis imperfecta?

Answer 3

USA study reported 1:14000 cases which is the currently accepted number.

Question 4

What is the most common type of amelogenesis imperfecta?

Answer 4

Hypoplastic (60 - 73%)

Hypomaturation (20 - 40%)

Hypocalcification (7%)

Question 5

What happens during the secretory phase of amelogenesis?

Answer 5

A proteinaceous EC matrix is incrementally laid-down by epithelially-derived ameloblasts via Tomes’ processes.

This matrix partially mineralises to delineate enamel architecture forming the enamel prisms and rods.

As the enamel layer approaches full thickness, the tomes’ process is retracted and the final outer enamel layer is aprismatic.

Ameloblasts then enter transition stage with reduced protein matrix secretion and internal reorganization

Cells then enter the maturation stage and begin secreting serine protease KLK4 that compltely degrades enamel crystals bathed in enamel tissue fluid

Question 6

What are the characteristics of hypoplastic amelogenesis imperfecta?

Answer 6

Enamel does not reach normal thickness during development

Thin enamel, loss of mesiodistal contact, enamel pits or vertical or horizontal fissures in the enamel.

Question 7

What are the characteristics of hypomature amelogenesis imperfecta?

Answer 7

Mottled brown-yellow-white appearance, enamel is generally of normal thickness and teeth meet at contact points

Female carriers may have vertical stripes of opaque white enamel alternating with bands of normal enamel (due to lyonisation)

Question 8

What are the characteristics of hypocalcified amelogenesis imperfecta?

Answer 8

Enamel is so soft taht it may be lost soon after eruption leaving crown of dentin.

Radiographically the enamel fails to contrast with the dentin

Question 9

What is type 4 amelogenesis imperfecta?

Answer 9

Similar to both hypoplastic and hypomature, in addition to taurodontism and anterior open bite with skeletal basis.

Enamel contrast to slightly more than dentin, large pulp chambers.

Question 10

What conditions can appear like amelogenesis imperfecta?

Answer 10

Fluorosis

MIH

Chronological hypoplasia

Question 11

What are the characteristics of fluorosis that can be used to differentiate it from amelogenesis imperfecta?

Answer 11

Diffuse opacities, usually not associated with caries, number of teeth involved depends on time of exposure

Question 12

What are the characteristics of MIH that can be used to differentiate it from amelogenesis imperfecta?

Answer 12

Well demarcated opacities, involves FPMs +/- incisors only, can be associated with PEB and secondary caries

Question 13

What are the characteristics of Chronological hypoplasia that can be used to differentiate it from amelogenesis imperfecta?

Answer 13

Number of teeth involved and the extent of hypoplastic defects depends on time of disruption, no genetic involvement, symmetrical, chronological pattern, linear ring-like pattern

Question 14

What are the defining features of AI that make it different to every other condition of similar appearance?

Answer 14

Involves all teeth

Family history usually present

Associated with anomalies based on the type such as AOB and taurodontism

Question 15

What are the ultrastructural characteristics of AI?

Answer 15

Histological sections of hypoplastic AI: Pitted, rough with irregular cracked borders

SEM analysis: Irregular and disorganised superficial enamel layer

Presence of external defects incorrectly oriented enamel prisms

Reduced tooth mineral density

Question 16

What are the associations seen with AI?

Answer 16

Intracoronal resorption: Aggressive, asymptomatic with secondary caries.

Failure of eruption (reported in several case reports)

Nephrocalcinosis syndrome

Question 17

What causes intracoronal resorption?

Answer 17

Unknown pathogenesis; ectopic positioning of affected teeth, periapical inflammation of primary precursor, and developmental defect due to inclusion of uncalcified enamel matrix are all thought to contribute.

Question 18

What is nephrocalcinosis syndrome?

Answer 18

First reported in 1972

Case reports failure of eruption, enamel agenesis, unexplained nephrocalcinosis and normal biochemical parameters

It is important to detect this early and paediatric dentists play an important role in early referral of patients with AI to exclude renal pathology

Question 19

How is AI managed?

Answer 19

Early diagnosis

Fixing the clinical issues

Ensure pain free aesthetic and efficient masticatory system for the patient

Stainless steel crowns post teeth and composite crowns anterior in primary dentition.

In mixed dentition take radiographs to check for supernumerary teeth.

Question 20

What are the clinical problems associated with nephrocalcinosis syndrome?

Answer 20

Clinical problems include: Aesthetics, dental sensitivity, loss of occlusal vertical dimension dure to loss of dental structure, dental caries and/or gingival inflammation, orthodontic considerations