The Biology Underlying Abnormalities of Tooth Number in Humans

Abstract

In past decades, morphologic, molecular, and cellular mechanisms that govern tooth development have been extensively studied. These studies demonstrated that the same signaling pathways regulate development of the primary and successional teeth. Mutations of these pathways lead to abnormalities in tooth development and number, including aberrant tooth shape, tooth agenesis, and formation of extra teeth. Here, we summarize the current knowledge on the development of the primary and successional teeth in animal models and describe some of the common tooth abnormalities in humans.

Concise Review: Cellular and Molecular Mechanisms Regulation of Tooth Initiation

“…However, detailed histological analyses of human embryonic mandibles, as well as the extensive genetic studies in mice, clearly demonstrate that a morphologically and molecularly distinct dental lamina precedes the formation of the placodes (reviewed in refs. [1,4] (Fig. 1).…”

“…The thickening within the oral ectoderm, also called dental lamina, is thus considered to be the first sign of tooth development (reviewed in refs. ( [1,4]. No teeth are formed outside the dental lamina strip, thus dental lamina indicates the position of the future dentition (reviewed in ref.…”

“…The function of the placode in tooth development is still a matter of controversy. It has been hypothesized that teeth of the same family (deciduous and permanent teeth of the same class in each jaw quadrant) are initiated from the same placode and that the placode (with the underlying mesenchyme) carries the information for the correct patterning of the individual tooth family [4,51]. Tucker et al suggested that the signal for the tooth type specification (e.g., unicuspid incisor vs. multicuspid molar) originates from the ectoderm and most likely involves BMP signaling [52].…”

“…2A) (formation of a new generation of teeth) or by serial addition (addition of teeth of the same class within the dentition of the same generation) (reviewed in ref. [4]. Both modes are generated through the extension of the dental lamina.…”

Tooth ablation in Iron Age central Thailand: Evidence from the archaeological sites of Ban Mai Chaimongkol and Tha Kae

“…In many cases, an individual may have missing teeth because of agenesis, the absence of a tooth germ, or its failure to develop (Parkin, Elcock, Smith, Griffin, & Brook, ). Agenesis is one of the most common congenital anomalies affecting human dentition and is controlled by a combination of genetic, environmental, and developmental factors (Cobourne, ; Juuri & Balic, ). Contemporary clinical research suggests prevalence rates for hypodontia vary, ranging from 2.6% to 11.3% depending on demographic profiles (Altug‐Atac & Erdem, ; De Coster, Marks, Martens, & Huysseune, ).…”