Chapter 6
Anomalies of Teeth
Aim
The aim of this chapter is to provide the practitioner with an insight into the radiological features of the common and important anomalies of development in the teeth and jaws.
Introduction
Anomalies affecting the teeth can be classified into developmental (occurring during embryogenesis) or acquired (subsequent to normal development). A number of anomalies are inherited or may be a manifestation of systemic disease.
A Classification of Dental Anomalies
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anomalies affecting the crown
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anomalies of enamel: localised or generalised
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anomalies of dentine: generalised
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anomalies of enamel and dentine
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altered crown morphology
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anomalies affecting the root
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anomalies of the pulp/root canals
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altered root morphology
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anomalies affecting the whole tooth
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alteration in tooth size
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altered tooth morphology
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anomalies affecting the number of teeth.
Anomalies of Enamel: Localised or Generalised
Amelogenesis can be disturbed by a variety of conditions that include hereditary, environmental, systemic and dietary factors. Enamel hypoplasia is the common term used to define defective or incomplete formation of the enamel matrix. Hereditary factors often affect both the deciduous and the permanent dentition. If factors within the environment are causal, knowledge of tooth development chronology (see Chapter 2) helps in determining the duration of their influence.
Other conditions that can affect amelogenesis are:
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nutritional deficiencies (vitamins A, C and D)
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exanthematous diseases (measles, chickenpox)
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congenital syphilis (see below)
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diseases resulting in hypocalcaemia
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conditions affecting the neonate (birth trauma, prematurity, Rh haemolytic disease)
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ingestion of certain chemicals (notably fluoride) and drugs (e.g. tetracycline)
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radiotherapy
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idiopathic causes.
General radiographic features common to all types of hypoplasia include linear radiolucencies crossing the crown (Fig 6-1), deformities affecting the mesial and distal margins of the tooth and defects or angular pitting on the crown of the tooth.
Fig 6-1 Enamel hypoplasia affecting the incisors and the developing 13. The position of the hypoplastic banding on the teeth suggests systemic illness in the first two years of life.
Turner’s Hypoplasia
This condition represents a defect occurring during amelogenesis that is the result of either local trauma or infection originating from the deciduous predecessor.
Clinical features
Permanent incisors or premolars are affected. The degree of hypoplasia depends upon the stage of tooth development and the severity and extent of the infection or trauma. Similar appearances can be seen affecting the developing teeth of children who have undergone radiotherapy to the head and neck region.
Radiological signs
If the deformity is minimal, the tooth will show a localised area of hypoplasia. A prolonged disturbance will lead to pronounced changes in tooth morphology that include gross deformity, irregularity and a reduction in crown size (Fig 6-2).
Fig 6-2 Turner’s hypoplasia affecting an unerupted 11. The crown is pitted. There was a history of previous chronic abscess on the deciduous precursor.
Amelogenesis Imperfecta
This is an inherited condition affecting enamel formation in both dentitions. From a purely radiological standpoint, amelogenesis imperfecta can be classified into two types: hypoplastic and hypocalcified.
Hypoplastic amelogenesis imperfecta
This occurs during the early stage of enamel formation and results in an abnormal enamel matrix that subsequently undergoes normal mineralisation.
Clinical features
The enamel matrix is either extremely thin or absent, with a variable appearance described as pitted, smooth, rough or glossy. The crowns of the teeth are “square-shaped”, resembling a tooth prepared for a full coronal restoration.
Radiological signs
The enamel is extremely thin but with a normal radiopacity compared to the underlying dentine (Fig 6-3).
Fig 6-3 Hypoplastic amelogenesis imperfecta. Note the thin enamel but normal underlying tooth structure.
Hypocalcified amelogenesis imperfecta
This represents disturbances occurring later in enamel formation affecting either the maturation or mineralisation of the matrix. The enamel has a normal thickness but defective mineralisation.
Clinical features
The colour of the affected crown ranges from clear through to brown. The enamel fractures away easily resulting in rapid attrition and a reduction in tooth height.
Radiological signs
There is a lack of radiographic contrast between dentine and enamel.
Anomalies of Dentine: Generalised
Dentinogenesis imperfecta
Dentinogenesis imperfecta, an inherited condition, affects both dentitions and is classified into two main types. In Type I, the condition coexists with osteogenesis imperfecta. In Type II there are no associated skeletal abnormalities.
Clinical features
The appearance of the teeth is characteristic, having an opalescent hue and small size. The enamel readily fractures from the tooth resulting in rapid attrition.
Radiological signs
The crowns of the teeth have a pronounced cervical constriction giving a “bulbous” appearance (Fig 6-4). There is obliteration of the pulp. The roots are short and slender and root fractures have been reported. Periapical radiolucencies are seen.
Fig 6-4 Dentinogenesis imperfecta. The bulbous crowns and spindly roots are typical features.
Dentinal dysplasia
Dentinal dysplasia is an inherited condition affecting both dentitions. It is divided into two types: Type I (radicular dentinal dysplasia) and Type II (coronal dentinal dysplasia). It occurs less frequently than dentinogenesis imperfecta.
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