Malformations of the tooth root in humans

Abstract

The most common root malformations in humans arise from either developmental disorders of the root alone or disorders of radicular development as part of a general tooth dysplasia. The aim of this review is to relate the characteristics of these root malformations to potentially disrupted processes involved in radicular morphogenesis. Radicular morphogenesis proceeds under the control of Hertwig's epithelial root sheath (HERS) which determines the number, length, and shape of the root, induces the formation of radicular dentin, and participates in the development of root cementum. Formation of HERS at the transition from crown to root development appears to be very insensitive to adverse effects, with the result that rootless teeth are extremely rare. In contrast, shortened roots as a consequence of impaired or prematurely halted apical growth of HERS constitute the most prevalent radicular dysplasia which occurs due to trauma and unknown reasons as well as in association with dentin disorders. While odontoblast differentiation inevitably stops when growth of HERS is arrested, it seems to be unaffected even in cases of severe dentin dysplasias such as regional odontodysplasia and dentin dysplasia type I. As a result radicular dentin formation is at least initiated and progresses for a limited time. The only condition affecting cementogenesis is hypophosphatasia which disrupts the formation of acellular cementum through an inhibition of mineralization. A process particularly susceptible to adverse effects appears to be the formation of the furcation in multirooted teeth. Impairment or disruption of this process entails taurodontism, single-rooted posterior teeth, and misshapen furcations. Thus, even though many characteristics of human root malformations can be related to disorders of specific processes involved in radicular morphogenesis, precise inferences as to the pathogenesis of these dysplasias are hampered by the still limited knowledge on root formation.

Molar‐incisor malformation: Eight new cases and a review of the literature

“…Numerous tooth and root malformations can be encountered in dental practice . One of these generalized, heritable defects is dentin dysplasia type 1 (DD‐1), which has an autosomal dominant pattern of inheritance . A rare condition, it is found in about one in 100 000 patients .…”

Cellular and molecular mechanisms of tooth root development

“…In humans, certain genetic mutations have been linked to root development defects (Dong et al, 2005;Yang et al, 2015). However, the majority of root defects observed in humans are associated with complex genetic disorders that lead to multiple developmental defects (reviewed by Luder, 2015). For example, BCOR mutations are responsible for causing oculofaciocardiodental (OFCD) syndrome, in which patients suffer from multiple craniofacial and cardiac anomalies but also have canines with extremely long roots (Fan et al, 2009;Gorlin, 1998).…”

Distal root curvatures in mandibular molars: analysis using digital panoramic X-rays

“…This is an important method limitation in the use of bidimensional images, but the justification of its use is based on the high prevalence of dilacerations and curvatures in mesial or distal direction. Finally, the criterion used to differentiate a curvature from a dilaceration of the root has varied over the years and this may in part explain the wide range of reported percentages [16]. Schneider [21] defines a way to measure the angle of deviation of the root with respect to the longitudinal axis of the tooth, thereby classifying the roots as straight, moderately or severely curved.…”

“…The causes of root dilacerations vary depending of tooth type and dentition. In permanent anterior teeth, dilacerations most often is a consequence of a trauma to the primary predecessor, such as an intrusive trauma, and produce a dislocation of the radicular parts of the germ [16,24]. On the other hand, the causes of root dilacerations of premolars and molar is not completely clear, although it is often seen when the roots of retained teeth encounter a cortical bone structure during its development [16].…”