Dental approach to craniofacial syndromes: how can developmental fields show us a new way to understand pathogenesis?

Abstract

The paper consists of three parts. Part 1: Definition of Syndromes. Focus is given to craniofacial syndromes in which abnormal traits in the dentition are associated symptoms. In the last decade, research has concentrated on phenotype, genotype, growth, development, function, and treatment. Part 2: Syndromes before Birth. How can the initial malformation sites in these syndromes be studied and what can we learn from it? In this section, deviations observed in syndromes prenatally will be highlighted and compared to the normal human embryological craniofacial development. Specific focus will be given to developmental fields studied on animal tissue and transferred to human cranial development. Part 3: Developmental Fields Affected in Two Craniofacial Syndromes. Analysis of primary and permanent dentitions can determine whether a syndrome affects a single craniofacial field or several fields. This distinction is essential for insight into craniofacial syndromes. The dentition, thus, becomes central in diagnostics and evaluation of the pathogenesis. Developmental fields can explore and advance the concept of dental approaches to craniofacial syndromes. Discussion. As deviations in teeth persist and do not reorganize during growth and development, the dentition is considered useful for distinguishing between syndrome pathogenesis manifested in a single developmental field and in several fields.

Figure 1

Schematic illustrations of craniofacial fields. Fn: frontonasal field, Mx: maxillary field, P: palatal field, Md: the complete mandibular field, and Oc: occipital and cervical spine field. Green arrows indicate migration paths of neural crest cells from different regions at the neural tube to different developmental fields in the cranium.

Figure 2

Profile (a) and frontal (b) radiograph of a girl aged 9 years with a single median maxillary central incisor. Different developmental fields are marked on the radiographs. Green: occipital and cervical spine field (Oc). Purple: theka field (T). Light and dark blue: the complete mandibular field (Md). Yellow: frontonasal field (Fn). Red: maxillary field (Mx). Orange: palatal field (P). Note that the sella turcica is a borderline region between fields. This figure is reprinted with permission from European Journal of Orthodontics 2010:32:140-147 [5].

Figure 3

Schematic drawing of the maxilla, demonstrating three different fields in the left and right side of the maxilla.

Figure 4

Panoramic radiograph illustrating the different fields in the maxilla and mandible with different innervation, surrounded by different ectomesenchyme. In the maxilla: red colour demonstrates the bilateral frontonasal field, innervated by the nervus nasopalatinus. Green colour demonstrates the bilateral maxillary field, innervated by the nervus maxillaris. Blue colour demonstrates the bilateral palatal fields, innervated by the nervus palatinus. In the mandible, similar fields are illustrated, innervated by different nerve branches from the nervus alveolaris inferior [6]. This figure is reprinted with permission from Orthodontic Waves 2012;71:1-16 [7].

Figure 5

Schematic illustration of hard tissue structures within the frontonasal field in the human cranium. s: sella turcica; c: crista galli; ns: nasal septum; n: nasal bone; i: central incisor.

Figure 6

Section of photograph of a girl, aged 12 years 1 month, with SMMCI (single median maxillary central incisor). The face is characterized by tubular-shaped nose and philtrum blurred towards the prolabium without the normal s-shape. Deviations all occur within the frontonasal field, illustrated schematically in Figure 5.

Figure 7

Intraoral photograph with a mirror placed between the dental arches, demonstrating the palate. The figure demonstrates a single central incisor, absence of papilla incisive, and a vault midaxially in the palate. Deviations all occur within the frontonasal field, illustrated schematically in Figure 5. The figure is reprinted with permission from Neuropediatrics 2009;40:280-283 [8].

Figure 8

Panoramic radiograph of the dentition in a girl with SMMCI, aged 12 years 1 month, shown in Figure 6. Note the maxillary central incisor, the narrow nasal cavity, and the close-set eyes. Apart from the maxillary front the dentition looks normal. Deviations all occur within the frontonasal field, illustrated schematically in Figure 5.

Figure 9

Profile radiograph of girl with SMMCI, aged 12 years 1 month, shown in Figure 6. Note the short anterior cranial fossa, the undeveloped sella turcica, and the maxillary retrognathia. Deviations all occur within the frontonasal field, illustrated schematically in Figure 5.

Figure 10

Intraoral photographs of two adult individuals with Trisomy 21/Down syndrome. In the left photograph, agenesis of the maxillary right lateral incisor and premolars is registered. Agenesis is also registered in the mandibular central incisor region. In the right photograph, an anterior vertical open bite is registered. In the maxilla a malformed right lateral incisor, agenesis of the left lateral incisor, and enamel pits at the central incisors are observed. In the mandible, agenesis of one central incisor is observed.

Figure 11

Profile radiograph of a girl with Down syndrome, aged 8 years 6 months. Note the enlarged thickness of the skull, absence of the nasal bone, deviations in the upper contour of the anterior wall of the sella turcica, malformations of the cervical spine, and maxillary retrognathia. Deviations of the skeleton occur in several craniofacial fields.