Dental developmental defects Flashcards
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
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
Explain the clinical and oral features of ectodermal dysplasia
- 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)
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
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
Define a supplemental teeth, and state the usual shape of supernumerary teeth
Supplemental teeth:
• Resemble normal tooth
Usual shape of supernumerary teeth
• Conical
Explain the pathogenesis of hypodontia by stating
- Which stage of tooth development is affected
- Patterns of inheritance
- Teeth most commonly affected (3)
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
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
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
State the clinical features of cleidocranial dysplasia
- 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
State the oral manifestations of cleidocranial dysplasia, including the shape of teeth. Talk about the the number of teeth
- 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
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)
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)
Discuss the separate pathogenesis of fusion and gemination
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
Discuss concrescence in terms of:
- What it is
- Which dentition it is most common in
- Possible causes
- Histology
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
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
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
Discuss dens invaginatus in terms of its histological features
- 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
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
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.
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
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
Describe regional odontodysplasia in terms of its cause, dentition/ teeth most affected and stage of tooth development affected:
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
Describe regional odontodysplasia in terms of the clinical features and treatment of affected teeth
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
Describe the histopathological features of regional odontodysplasia
- 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)
Describe dentinogenesis imperfecta by stating:
- What type 1 dentinogenesis imperfecta is associated with
- The inheritance pattern of type 2 dentinogenesis imperfecta
- The basic pathophysiology
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
Describe dentinogenesis imperfecta by stating:
- Which dentitions are affected
- Teeth colour
- Appearance of teeth
- Radiographic appearance
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
Describe the histopathological appearance of dentinogenesis imperfecta
- 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
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)
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
Explain the following subtypes of amelogenesis imperfecta
- Hypoplastic
- Hypomaturation
- Hypocalcified
- Hypomatration- hypoplastic taurodontism
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.
Briefly explain the pathogenesis of amelogenesis imperfecta, and mention the inheritance patterns
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.
