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

Region-specific gene expression profiling of early mouse mandible uncovered SATB2 as a key molecule for teeth patterning

Mammalian dentition exhibits distinct heterodonty, with more simple teeth located in the anterior area of the jaw and more complex teeth situated posteriorly. While some region-specific differences in signalling have been described previously, here we performed a comprehensive analysis of gene expression at the early stages of odontogenesis to obtain complete knowledge of the signalling pathways involved in early jaw patterning. Gene expression was analysed separately on anterior and posterior areas of the lower jaw at two early stages (E11.5 and E12.5) of odontogenesis. Gene expression profiling revealed distinct region-specific expression patterns in mouse mandibles, including several known BMP and FGF signalling members and we also identified several new molecules exhibiting significant differences in expression along the anterior-posterior axis, which potentially can play the role during incisor and molar specification. Next, we followed one of the anterior molecules, SATB2, which was expressed not only in the anterior mesenchyme where incisor germs are initiated, however, we uncovered a distinct SATB2-positive region in the mesenchyme closely surrounding molars. Satb2-deficient animals demonstrated defective incisor development confirming a crucial role of SATB2 in formation of anterior teeth. On the other hand, ectopic tooth germs were observed in the molar area indicating differential effect of Satb2-deficiency in individual jaw regions. In conclusion, our data provide a rich source of fundamental information, which can be used to determine molecular regulation driving early embryonic jaw patterning and serve for a deeper understanding of molecular signalling directed towards incisor and molar development.

Evaluation of Twenty Non-Metric Dental Crown Traits in Different Types of Malocclusions in a Sample from India, New Delhi Population

Background

Dental phenotype shows variation in the form of various metric and non-metric traits, primarily due to gene-environment interplay. It gives an insight into the evolutionary trends, ancestry, and food habits. Recently, it has been explored for genetic affinity with several growth anomalies and development of craniofacial skeleton which is also responsible for dental and skeletal malocclusions.

Objectives

the current study aims to investigate the non-metric dental crown traits (NDCTs) using Arizona State University Dental Anthropology system (ASUDAS) in different types of malocclusions in Delhi, National Capital Region (NCR) population.

Materials and methods

The study design was observational and retrospective. The total sample comprised of 240 pairs of dental casts divided into four equal groups of 60 subjects each (30 male and 30 female), based on malocclusion. The four groups of malocclusions were: Angle's Class I, Class II division 1, Class II division 2, Class III. The investigator was blinded for patient ID and sex before recording the data. The data for cast were recorded by three observers independently in a modified malocclusion- non-metric dental crown traits (M-NDCT) anthropological variants chart and statistically analyzed for association with different malocclusions and sex.

Results

Significant differences were found in the expression of several NDCTs (both in presence and scoring) in different malocclusions. Class I malocclusion showed a predominantly winging, shoveling -upper central and lateral incisor, protostylid, hypoconulid absence in lower second molar, and cusp number. Class II malocclusion showed a double shoveling, interrupted groove, tuberculum dentale, canine mesial ridge, premolar accessory cusp, Carabelli's trait, lingual cusp variation, and seventh cusp in the lower left first molar. Class III malocclusion showed the absence of hypocone in upper second molar, deflecting wrinkle, distal trigonid crest, and Y groove in left lower second molar (26.7%). Besides, sexual dimorphism was seen in shoveling -upper central and lateral incisor, canine mesial ridge, Carabelli's trait, 3-cusp in upper second molar, and cusp number.

Conclusions

Significant association was found between non-metric dental traits and malocclusions (Class I, Class division 1, Class II division 2, and Class III). Significant sex-linked differences were also found. Further studies can be performed at multicenter pan-India level with a standard robust protocol and a large sample.

Binder's phenotype with ankyloglossia: Report of a rare inherited association in an Indian female

Binder's syndrome, a rare congenital malformation of nasomaxillary complex, first described in 1962, has a hexad of characteristic clinical and radiographic features consisting of arhinoid face, intermaxillary hypoplasia with malocclusion, abnormal position of nasal bones, atrophy of nasal mucosa, reduced or absent anterior nasal spine and hypoplastic/absent frontal sinus. The typical facies due to mid-face hypoplasia may also be accompanied by other midline malformations such as cleft palate, spinal, skeletal and cardiac abnormalities. It is usually sporadic, of unknown etiology although various environmental and genetic mechanisms are implicated due to few familial cases predominantly in the Swedish population. A case of inherited Binder's syndrome is presented in an Indian female patient with an unusual finding of ankyloglossia (AG). The development of the anterior nasal spine and AG are chronologically related as they both occur during the 5^th–6^th weeks of gestation. The possible etiopathogenetic mechanisms for this rare association are reviewed.

Sella Turcica Morphology in Patients With Genetic Syndromes: Protocol for a Systematic Review

Background

The sella turcica is an important anatomical reference used in orthodontics and the evaluation of craniofacial growth. Studies have found an association between variations in sella turcica morphology in patients with certain syndromes affecting the craniofacial complex. It is hypothesized that each related syndrome or pathological condition is associated with a specific pattern of malformation of the sella turcica.

Objective

This study outlines the protocol for a systematic review that aims to determine if genetic syndromes involving the craniofacial complex are associated with abnormal radiographic sella turcica morphology and if there is a pattern of malformation that is consistent with each syndrome.

Methods

An electronic database search was conducted using a planned search strategy to identify relevant studies. We included primary studies evaluating the morphology of the sella turcica based on imaging from a lateral view. Specifically, only studies with postnatal human participants with genetic syndromes involving the craniofacial complex were included in this review. We placed no restrictions on the language or time frame of these studies. Based on the search findings, studies were further screened for relevance and eligibility by two independent reviewers. Data were extracted from the selected studies. We assessed the selected studies for risk of bias and quality by using risk of bias tools from the Joanna Briggs Institute. We will provide a narrative synthesis of our findings and a structured summary based on prespecified themes.

Results

The protocol is registered with PROSPERO (#CRD42019148060) and approved by the University of Western Cape Biomedical Science Research Ethics Committee (BM205/3). The literature search was conducted in September 2019 and updated in July 2020. The study was completed in August 2020, and the findings will be published in an open-access journal.

Conclusions

The results of this systematic review are expected to provide a comprehensive list of morphological variations of the sella turcica, which will aid in the identification of syndromes associated with the craniofacial complex. We also expect to identify patterns of sella turcica morphology that highlight genotype-phenotype correlations, thus adding to the body of evidence relating to genetics and craniofacial malformations.

Trial Registration

PROSPERO International Prospective Register of Systematic Reviews CRD42019148060; https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=148060

International Registered Report Identifier (IRRID)

RR1-10.2196/16633

General and stomatologic aspects of bardet-biedl syndrome

OBJECTIVE

The purpose of this study is to present a clinical report of a patient with Bardet-Biedl syndrome, aiming to help the dentist to identify the general aspects, systemic changes, alterations.

CLINICAL REPORT

Bardet-Biedl syndrome is defined as a genetic disorder of autosomal recessive condition; this case is a male patient, 20 years old. The general features presented by the patient were strabismus, polydactyly, hypogonadism, obesity, cognitive impairment, and autistic behavior. Dentally, this patient presents with hypotonic face, high-arched palate, dental crowding, unilateral crossbite, and difficulty in cleaning but with good-quality oral health.

CONCLUSIONS

Many patients with this syndrome have compromised oral hygiene, difficulty in addressing dental cases, developmental delay, and autistic behavior. Thus, it is important to pay attention to these early children from an early age and encourage preventive approach.

Klippel-feil: A syndrome in the occipital-cervical spine field and its dentofacial manifestations

Klippel-Feil syndrome (KFS) is defined by congenital cervical vertebral spine fusion and is seen with a wide spectrum of dental manifestations and craniofacial profiles. Previous studies on lateral cephalograms have documented an association between fusion of the cervical vertebrae and deviations in the craniofacial profile in non-syndromic patients with severe malocclusion. To our knowledge, no previous studies have described the craniofacial profile including the cranial base of KFS patients on lateral cephalograms. Therefore KFS and its craniofacial and dental manifestations were described according to existing literature and additionally the craniofacial profile and cranial base was analysed on lateral cephalograms of two patients with KFS. According to the literature the dental manifestations of KFS-patients included oligodontia, overjet, cross bite, open bite and deep bite. The craniofacial profile was clinically described as reduced lower facial height, midfacial hypoplasia, and mandibular prognathia. The analyses of the two lateral cephalograms showed increased mandibular inclination, increased vertical jaw-relationship, increased jaw angle and maxillary retrognathia. The cranial base was normal in both cases. The sagittal jaw relationship and mandibular prognathia varied between the two cases. The literature review and the analyses of the two lateral cephalograms have shown that deviations in the occipital and cervical spine field as KFS were associated with deviations in the teeth and craniofacial profile.

Mechanism of human tooth eruption: review article including a new theory for future studies on the eruption process

Human eruption is a unique developmental process in the organism. The aetiology or the mechanism behind eruption has never been fully understood and the scientific literature in the field is extremely sparse. Human and animal tissues provide different possibilities for eruption analyses, briefly discussed in the introduction. Human studies, mainly clinical and radiological, have focused on normal eruption and gender differences. Why a tooth begins eruption and what enables it to move eruptively and later to end these eruptive movements is not known. Pathological eruption courses contribute to insight into the aetiology behind eruption. A new theory on the eruption mechanism is presented. Accordingly, the mechanism of eruption depends on the correlation between space in the eruption course, created by the crown follicle, eruption pressure triggered by innervation in the apical root membrane, and the ability of the periodontal ligament to adapt to eruptive movements. Animal studies and studies on normal and pathological eruption in humans can support and explain different aspects in the new theory. The eruption mechanism still needs elucidation and the paper recommends that future research on eruption keeps this new theory in mind. Understanding the aetiology of the eruption process is necessary for treating deviant eruption courses.

Prenatal exposure to antiepileptic drugs and dental agenesis

OBJECTIVE

The aim of the study was to investigate the association between prenatal exposure to AEDs and the risk of dental agenesis and to differentiate between the possible effects of the different drugs used.

METHODS

Data on 214 exposed and 255 unexposed children, aged 12-18 years, were extracted from the Prescription Database of the Central Denmark Region and North Denmark Region and the Danish Medical Birth Registry. The children's dental charts were examined for the presence of dental agenesis.

RESULTS

Overall, children exposed to AED in utero had an increased risk of developing dental agenesis, but as a group, the difference was not significant (OR = 1.7; [95% CI: 0.8-3.6]). The risk of developing dental agenesis was three-fold increased (OR = 3.1; [95% CI: 1.3-7.4]) in children exposed to valproate in mono- or in poly-therapy with other AEDs than carbamazepine or oxcarbazepine. The risk was further increased (OR = 11.2; [95% CI: 2.4-51.9]) in children exposed to valproate and carbamazepine or oxcarbazepine in combination.

CONCLUSIONS

The present study shows that dental agenesis is a potential congenital abnormality that is related to prenatal exposure to valproate, and dental agenesis may be considered a sensitive marker for the teratogenicity of valproate.