Local Diseases
1 Dental Defects
Nick A. Lygidakis Consultant Paediatric Dentist DDS, MScD, MScM, DrOdont
Marina G. Laskari Orthodontist, DDS, MSc Boston University, USA
Defects in Size
These defects result from various etiological factors acting during the stage of dental morphodifferentiation.
Microdontia
Definition
• Refers to teeth that appear smaller in size compared to normal. Pseudomicrodontia refers to all teeth of an individual appearing smaller than normal, as a result of enlarged jaw dimensions. True microdontia refers to teeth of smaller size in a jaw of normal size (Figs. 1.1, 1.2).
Etiology
• Multifactorial. Generalized microdontia is rare, and may be associated with congenital hypopituitarism or exposure to radiation or chemotherapy during dental development. In contrast, localized microdontia is more common, and is frequently followed by hypodontia; it has therefore been suggested that these two defects are controlled by different mutations in the same genes.
• Syndromes in which microdontia may be seen include the trisomy 21 syndrome, the ectodermal dysplasia syndromes, and the Marshall I, Rieger, focal dermal hypoplasia, Silver-Russell, Williams, Gorlin-Chaudhry-Moss, Coffin-Siris, Salamon, trichorhinophalangeal, odontotrichomelic, neuroectodermal, and dermo-odontodysplasia syndromes.
• Also a frequent finding in cases of cleft lip and palate.
Occurrence in children
• Rare (less than 1%) in primary teeth.
• More common (2.5%) in permanent teeth.
• Females more frequently affected than males.
Localization
• Upper laterals.
• Upper third molars.
Clinical features
• Usual crown shape or sometimes with tapering (peg or conical) crown, but smaller in size than the range of normal variation.
Treatment
• Aesthetic restoration with composites, crowns in severe cases, orthodontic treatment for closure of spaces, if needed.
Macrodontia
Definition
• Refers to teeth that appear larger than the normal size. Some or all teeth may be affected (Fig. 1.3).
Etiology
• Multifactorial. Generalized macrodontia is observed in cases of pituitary gigantism, and in individuals with small jaws. Localized macrodontia is observed in cases of unilateral facial hyperplasia, resulting from over-development of tooth buds.
• Macrodontia may also be associated with congenital hemifacial hypertrophy and some genetic syndromes such as craniofacial dysostosis, otodental svndrome, and Sturge–Weber syndrome.
Occurrence in children
• Rare (1.1%) in permanent dentition.
Localization
• Lower third molars and second premolars.
• Upper central incisors.
• Frequent bilateral symmetry.
Clinical features
• Usual tooth morphology with rounded edges, exceeding in size the range of normal variation.
Complications
• Clinically, macrodontia may lead to crowding and potential abnormal teeth eruption as a result of reduced available space in the dental arch.
Treatment
• Aesthetic restoration and orthodontic treatment of the potential crowding.
Fig. 1.1 Microdontia of the upper lateral incisors
Fig. 1.2 Microdontia of a lower permolar
Fig. 1.3 Macrodontia of the upper and lower incisors in a patient with otodental syndrome
Conical Teeth
Definition
• Refers to teeth that have a conical shape with a pointed edge.
Etiology
• Frequently followed by hypodontia, and for this reason it has been suggested that these two anomalies are controlled by different mutations in the same genes (Fig. 1.4).
• In the majority of the cases, conical teeth are found in patients with genetic disorders such as ectodermal dysplasia, Rieger, dento-onychodermal and incontinentia pigmenti syndromes.
Occurrence in children
• Rare in both permanent and primary teeth (0.2%).
Localization
• Upper incisors.
Clinical features
• Characteristic conical shape with sharp, pointed edge.
Treatment
• Aesthetic restoration with composites, crowns.
Defects in Shape
These defects manifest as a result of various etiological factors acting during the initiation/proliferation and the morphodifferentiation stages of dental development.
Gemination
Definition
• Refers to incomplete division of the tooth bud, resulting in the formation of two partially or completely independent crowns with a shared root (Fig. 1.5). If the division is complete, the anomaly is termed twinning, and results in the formation of a supernumerary tooth, which appears as a minor image of its normal partner.
Etiology
• This defect can be found in both the primary and permanent dentitions, and results from various degrees of invagination of the developing dental organ caused by local, systemic, and genetic factors.
• The genetic factors involved are probably similar to those affecting the dental lamina in cases of hyperdontia.
Occurrence in children
• Including fusion, rare in both primary (0.5–1.6%) and in permanent