Dental developmental defects

Question 1

Discuss the pathogenesis of ectodermal dysplasia in terms of:

• Inheritance pattern/ gender affected
• Which gene is mutated
• What that gene’s role is in health

Answer 1

Inheritance pattern:
· Although in the majority of families it is inherited as an X-linked recessive trait, in some families it is inherited as an autosomal-recessive trait
· Female carriers usually show only mild manifestations

Which gene is mutated:
· EDA gene

What that gene’s role is in health:
· The EDA gene creates a protein which is involved in cell- cell signalling during early embryonic development when ectodermal organs are forming

Question 2

Explain the clinical and oral features of ectodermal dysplasia

Answer 2

• Characterized by the congenital absence of ectodermal structures
• Affected patients have smooth, dry skin with fine, scanty hairs and partial or total absence of sweat glands which leads to hyperthermia
• Teeth are either missing, or retarded in eruption, deformed, and frequently have conical crowns (peg shaped)

Question 3

Discuss the cause of hyperdontia in terms of:

• Where it is most common in the maxilla and mandible
• Associated conditions
• Which gender is more affected
• Which stage of tooth development is implicated

Answer 3

Where it is most common in the maxilla and mandible:
• Maxilla: anterior and molar regions of the
• Mandible: premolar region

Associated conditions:
• Associated with other defect like cleft palate or cleidocranial dysplasia

Which gender is more affected:
• Females

Stage of tooth development implicated:
• Initiation/ bud stage

Question 4

Define a supplemental teeth, and state the usual shape of supernumerary teeth

Answer 4

Supplemental teeth:
• Resemble normal tooth

Usual shape of supernumerary teeth
• Conical

Question 5

Explain the pathogenesis of hypodontia by stating

• Which stage of tooth development is affected
• Patterns of inheritance
• Teeth most commonly affected (3)

Answer 5

Stage of tooth development implicated:
• Initiation/ bud stage

Patterns of inheritance:
• Tends to be genetically linked (familial)

Teeth most commonly affected (3):
• Permanent dentition
• Third molars, permanent maxillary lateral incisors, and mandibular second premolars are most commonly affected

Question 6

Explain cleidocranial dysplasia in terms of:

• What the condition affects
• Inheritance pattern
• Which gene is affected/ function of the gene
• Which conditions it is related to

Answer 6

What the condition affects:
• A condition that primarily affects the development of the bones and teeth

Inheritance pattern:
• Autosomal dominant

Gene that is affected/ function of the gene:
• It is caused by mutations to the RUNX2 gene(affects osteoblast activity)
• This gene gives the body instructions to make aproteinused in the development and maintenance of bone and cartilage

Conditions it is related to:
• Related with osteogenesis imperfecta

Question 7

State the clinical features of cleidocranial dysplasia

Answer 7

• Underdeveloped or absent clavicles
• Dental abnormalities
• The cranium develops a mushroom shape because the fontanelles remain open
• Frontal, parietal, and occipital enlargement is quite noticeable

Question 8

State the oral manifestations of cleidocranial dysplasia, including the shape of teeth. Talk about the the number of teeth

Answer 8

• Peg shapedteeth
• Extrateeth
• Delayed loss of the primary (baby)teeth
• Delayed appearance of the secondary (adult)teeth
• Misalignment of theteethand jaws (malocclusion)

Number of teeth:
• Patients have many supernumerary teeth
• They are crowded in the jaws and do not erupt/ interfere with the eruption of normal teeth
• This results in pseudoanodontia

Question 9

Talk about connation (fusion and gemination) in terms of

• Which stage of tooth development is affected
• Which dentition is more commonly affected
• Which teeth are most frequently affected (2)

Answer 9

Which stage of tooth development is affected:
• Bud stage of formation

Which dentition is more commonly affected:
• Primary dentition

Which teeth are most frequently affected (2):
• Incisors
• Canines in the primary dentition)

Question 10

Discuss the separate pathogenesis of fusion and gemination

Answer 10

Fusion:
• Two separate developing teeth unite (and thus their dentine and enamel)
• There may two different pulps that slightly merge

Gemination:
• Two teeth develop from one tooth bud and as a result, the patient has an extra tooth
• Here, the two teeth share a common pulp
• Thus, two crowns arising from one single root

Question 11

Discuss concrescence in terms of:

• What it is
• Which dentition it is most common in
• Possible causes
• Histology

Answer 11

What it is:
• An acquired disorder in which the roots of one or more teeth are united by cementum alone

Dentition and teeth (jaw) most commonly affected:
• Permanent dentition where the roots of teeth develop close together
• Seen in maxillary posterior region -> 2nd and 3rd molar

Possible causes:
• May be following hypercementosis associated with chronic inflammation -> inflammatory changes at apical portion of root fuse

Histology:
• Excess cementum

Question 12

Discuss dens invaginatus in terms of:

• Which stage of tooth development it occurs in
• Which histological structure is affect/ explain how it occurs
• The most common jaw/ tooth affected

Answer 12

Which stage of tooth development it occurs in:
• Early bell stage (this is where crown shape is established)

Which histological structure is affect/ explain how it occurs:
• Occurs when the inner enamel epithelium invaginates into the dental papilla
• Thus, when development has been completed, the affected and distorted tooth contains a cavity that is completely or partially lined by enamel

The most common jaw/ tooth affected:
• Maxillary lateral incisors

Question 13

Discuss dens invaginatus in terms of its histological features

Answer 13

• No irregularities in the dentin below invagination
• Strains of vital tissue or fine canals that communicates with the pulp could be found
• Enamel lining irregularly structures
• TOOTH USUALLY NON VITAL -> therefore a necrotic pulp

Question 14

Discuss dens exvaginatus in terms of:

• Which stage of tooth development it occurs in
• Which histological structure is affect/ explain how it occurs
• The most common jaw/ tooth affected

Answer 14

Which stage of tooth development it occurs in:
• Early bell stage (this is where crown shape is established)

Which histological structure is affect/ explain how it occurs:
• Evagination of inner enamel epithelium cells, which are the precursors of ameloblasts
• Causes extra enamel/ cusp tip

The most common jaw/ tooth affected:
• Man­dibular premolars.

Question 15

For dilaceration:

• Explain dilaceration
• State which stage of tooth formation is affected
• State the most commonly affected teeth
• State the 2 most common causes of trauma to deciduous teeth

Answer 15

Stage of tooth formation affected:
• Root development or early bell stage (if crown is dilacerated)

Explanation:
• Injury displaces calcified portion of tooth germ, causing the remainder of tooth to form at a deformed angle
• Usually the result of acute mechanical trauma

State the most commonly affected teeth:
• Maxillary incisor

State the most common causes of trauma to deciduous teeth:
• Injured during laryngoscopy and endotracheal intubation

Question 16

Describe regional odontodysplasia in terms of its cause, dentition/ teeth most affected and stage of tooth development affected:

Answer 16

Cause:
• Uncommon developmental disorder of unknown aetiology associated with abnormalities of enamel, dentine, pulp, and the dental follicle

Teeth most affected:
• Both dentitions are affected
• Maxillary anterior, and is only limited to that area

Stage of tooth development affected:
• Advanced bell stage/ root stage

Question 17

Describe regional odontodysplasia in terms of the clinical features and treatment of affected teeth

Answer 17

Clinical features
• Very thin enamel and dentin are present
• On occasion, the enamel is not visible on the radiograph
• The pulp chambers of these teeth are extremely large
• Either the teeth do not erupt, or eruption is incomplete
• If ghost teeth erupt into the oral cavity, they are typically nonfunctional and malformed

Treatment:
Exo

Question 18

Describe the histopathological features of regional odontodysplasia

Answer 18

• Large areas of interglobular dentine
• Pulp stones?
• Irregular closure of enamel/dentine/ pulp
• Coronal dentin appears grey
• Invaginations extending from the enamel surface to the dentin
• Wide pulp space(possibly necrotic)

Question 19

Describe dentinogenesis imperfecta by stating:

• What type 1 dentinogenesis imperfecta is associated with
• The inheritance pattern of type 2 dentinogenesis imperfecta
• The basic pathophysiology

Answer 19

What type 1 Dentinogenesis imperfecta is associated with:
• Osteogenesis imperfecta

The inheritance pattern of type 2 Dentinogenesis imperfecta:
• Autosomal dominant

The basic pathophysiology:
• Defect lies with the odontoblasts, which lay down an abnormal matrix and then degenerate
• Cells derived from the dental pulp, which lay down abnormal dentin, later replace these odontoblasts

Question 20

Describe dentinogenesis imperfecta by stating:

• Which dentitions are affected
• Teeth colour
• Appearance of teeth
• Radiographic appearance

Answer 20

Which dentitions are affected:
• Both dentitions
• But, primary teeth show more severe symptoms

Teeth colour:
• Opalescent brown to brownish-blue

Appearance of teeth:
• Teeth have bulbous crowns
• Enamel hypoplasia as well
• The dentin is very soft, which produces chipping of enamel that results in tooth attrition (thus, absent enamel)

Radiographic appearance:
• Short, blunt, thin roots
• Total obliteration of the pulp chambers and root canals by dentine
• Periapical radiolucencies

Question 21

Describe the histopathological appearance of dentinogenesis imperfecta

Answer 21

• Normal tubular mantle dentine
• Dentine contains a reduced number of tubules which are wide or irregular
• Areas of atubular dentine may be present
• Abnormal dentine partly or totally obliterates the pulp chamber and root canal
• Dentine shows an increased water content and a decreased mineral content when compared with normal dentine

Question 22

Discuss dentinal dysplasia by stating/ explaining:

• Inheritance pattern
• Type 1 (teeth appearance, cause, radiographic appearance and histology)
• Type 2 (genetic defect, teeth appearance diff between primary/ permanent, radiographic appearance)

Answer 22

Inheritance pattern:
• Autosomal dominant inheritance

Type 1 rootless teeth/ radicular:
• Appearance: Teeth have normal crowns, normal colour BUT abnormal roots
• Because of the short roots, the teeth generally are exfoliated prematurely
• Cause: Disturbances in the Hertwig epithelial root sheath, which guides the formation of the root
• Radiographs: total or partial lack of pulp chambers and root canals and multiple peri-apical radiolucencies
• Histopathology: The pulp chambers of the permanent teeth generally are not obliterated fully and have a half-moon appearance on radiographs

Type 2/ coronal:
• Genetic defect: The basic defect in this condition is a mutation in the gene termed dentin sialophosphoprotein (DSPP)
• Teeth appearance: Translucent teeth with an amber colour characterize the primary dentition. However, permanent teeth appear normal
• Radiographs: lack of pulp chambers and small root canals (primary teeth). Thistle-shaped pulp chambers in single-rooted teeth and a bow-tie appearance of the pulp chambers of permanent molars

Question 23

Explain the following subtypes of amelogenesis imperfecta

• Hypoplastic
• Hypomaturation
• Hypocalcified
• Hypomatration- hypoplastic taurodontism

Answer 23

Hypoplastic:
• The enamel is hard/ mineralised but there isn’t enough of it
• The teeth are small, and the enamel is thin. Enamel is pitted.

Hypomaturation:
• Mutation to the KLK4 gene
• The enamel has a normal thickness, but it’s too soft due to high amounts of enamel matrix (under mineralised), so the teeth appear mottled and may wear away and break
• This defect occurs in the maturation stage of enamel formation
• Hydroxyapaptite crystals are normal but low thickness.

Hypocalcified:
• Defect occurs in the initial stages of enamel formation
• The enamel may have a normal thickness, but it’s too soft
• The teeth may be white, yellow, or brown, and the enamel may be pitted
• Hydroxyapaptite crystals are short, but normal thickness.

Hypomatration- hypoplastic taurodontism:
• The thin enamel is yellow to brown and pitted
• On radiographs the enamel has a radiodensity similar to dentin, and single-rooted teeth have large pulp chambers and molar teeth appear as taurodonts.

Question 24

Briefly explain the pathogenesis of amelogenesis imperfecta, and mention the inheritance patterns

Answer 24

Enamel formation:
• During the late bell stage, the ameloblasts lay down enamel 30% of which are almost instantaneously calcified. Here, hydroxyapatite crystals grow in length and form connections with each other
• After that, there is slow maturation of the enamel matrix where there Is the slow degradation of the enamel matrix and replacement of that degraded matric with hydroxyapatite. Here, hydroxyapatite crystals grow in width

Pathogenesis:
• AI is diverse collection of inherited diseases that causes qualitative or quantitative enamel defects
• Defects in genes encoding for specific enamel proteins have been implicated as causes for AI

Inheritance patterns:
• Mostlyinherited as autosomal dominant or, less frequently, X-linked traits.

Question 25

Explain tetracycline staining as an intrinsic source of tooth staining by stating:

• Causes
• Structure most affected
• Histological appearances of teeth
• Appearance of affected teeth

Answer 25

Cause:
• Systemic administration of tetracyclines during the period of tooth development results in their deposition in the dental hard tissues as well as in bone

Structure most affected:
• Dentine is more heavily stained than enamel

Histological appearances of teeth:
• Ground sections of affected teeth yellow bands of pigmentation related to incremental lines in dentine can be seen
• The pigmented bands fluoresce a bright yellow under ultraviolet light

Appearance of affected teeth:
• Affected teeth generally are yellowish when they erupt and become darker and browner after exposure to light.

Question 26

Explain fluorosis as an intrinsic source of tooth staining by stating:

• Which tooth formation stage is most sensitive and least sensitive
• Causes

Answer 26

Tooth formation stage is most sensitive and least sensitive:
• Early maturation phase of enamel = most sensitive
• Secretory phase = least sensitive

Cause:
• Ingestion of excess fluoride during the period of tooth formation may result in dental fluorosis, producing hypomineralized or hypoplastic enamel
• Effects dependent on dose, duration, and timing of exposure

Question 27

Explain erythroblastosisfoetalis as an intrinsic source of tooth staining by stating:

• Explanation
• Tooth appearance (colours) and histology results

Answer 27

Explanation
• Type of anaemiain which erythrocytes of a foetusare destroyed in a maternal immune reaction resulting from a blood groupincompatibility between the foetus and its mother

Tooth appearance (colours) and histology results:
• Teeth have blood pigment in the enamel and dentin, giving them a green, brown or blue hue
• Ground section of teeth test positive for bilirubin