Development of the dentition in cleidocranial dysplasia

Three-dimensional evaluation of dental characteristics in patients with Cleidocranial dysplasia

BACKGROUND

Cleidocranial dysplasia (CCD) is an autosomal dominant hereditary disorder. Besides skeletal abnormalities, CCD is often associated with dental complications, such as multiple supernumerary teeth and permanent teeth impaction or delayed eruption.

METHODS

Supernumerary teeth of axial, sagittal and coronal CBCT view was characterized in detail and 3D image reconstruction was performed. Number and location of teeth, morphology of supernumerary teeth, positional relationship between supernumerary and adjacent permanent teeth, direction of supernumerary teeth in CCD patients were analyzed.

RESULTS

The mean age of the 3 CCD patients in this study was 16.7 years. Among 36 supernumerary teeth, the majority of them were identified as apical side located and lingual side located. Normal orientation was the most common type in this study, followed by sagittal orientation, and horizontal orientation. Horizontal orientation teeth were all distributed in the mandible. Supernumerary teeth exhibited significantly shorter crown and dental-root lengths, as well as smaller crown mesiodistal and buccolingual diameters (P < 0.01). There was no difference in the number of supernumerary teeth between the maxilla and mandible, and the premolars region had the largest number of supernumerary teeth and the incisor region had the smallest number.

CONCLUSIONS

This study compares number and location of teeth, morphology of supernumerary teeth, positional relationship between supernumerary and adjacent permanent teeth and direction of supernumerary teeth, this study also provides a reference for the comprehensive evaluation of CCD patients before surgery.

Runx2 heterozygosity alters homeostasis of the periodontal complex

BACKGROUND AND OBJECTIVE

Haploinsufficiency of Runx2 (Runx2+/- ) causes dental anomalies. However, little is known about the involvement of Runx2 in the maintenance of dentin, cementum, and the periodontal ligament (PDL) during adulthood. This study aimed to observe the effects of Runx2+/- on homeostasis of the periodontal complex.

MATERIALS AND METHODS

A total of 14 three-month-old Runx2+/- mice and their wild-type littermates were examined using micro-computed tomography, histology, and immunohistochemistry. Phenotypic alterations in the dentin, cementum, and PDL were characterized and quantified.

RESULTS

Haploinsufficiency of Runx2 caused cellular changes in the PDL space including reduction of cell proliferation and apoptosis, and irregular attachment of the collagen fibers in the PDL space into the cementum. Absence of continuous thickness of cementum was also observed in Runx2+/- mice.

CONCLUSION

Runx2 is critical for cementum integrity and attachment of periodontal fibers. Because of its importance to cementum homeostasis, Runx2 is essential for homeostasis of periodontal complex.

Rare bilateral incisiform supernumerary teeth: A case report

An increased number of teeth in relation to normal dental formula is called hyperdontia, and the additional tooth are termed as supernumerary tooth. A supplemental tooth is a supernumerary tooth that closely resembles in shape to its adjacent teeth with which they are associated and supplements for occlusion. Primary dentition presents with lower prevalence of supernumerary teeth compared to permanent dentition. This report presents supplemental teeth in primary dentition.

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Advances in tooth agenesis and tooth regeneration

The lack of treatment options for congenital (0.1%) and partial (10%) tooth anomalies highlights the need to develop innovative strategies. Over two decades of dedicated research have led to breakthroughs in the treatment of congenital and acquired tooth loss. We revealed that by inactivating USAG-1, congenital tooth agenesis can be successfully ameliorated during early tooth development and that the inactivation promotes late-stage tooth morphogenesis in double knockout mice. Furthermore, Anti- USAG-1 antibody treatment in mice is effective in tooth regeneration and can be a breakthrough in treating tooth anomalies in humans. With approximately 0.1% of the population suffering from congenital tooth agenesis and 10% of children worldwide suffering from partial tooth loss, early diagnosis will improve outcomes and the quality of life of patients. Understanding the role of pathogenic USAG-1 variants, their interacting gene partners, and their protein functions will help develop critical biomarkers. Advances in next-generation sequencing, mass spectrometry, and imaging technologies will assist in developing companion and predictive biomarkers to help identify patients who will benefit from tooth regeneration.

Conservative orthodontic and multidisciplinary approaches for patients with cleidocranial dysplasia in late adolescence or young adulthood

This case series describes conservative orthodontic and multidisciplinary approaches for treating two patients diagnosed with cleidocranial dysplasia in late adolescence and young adulthood. Most of the impacted permanent teeth erupted spontaneously within 3 to 4 years after surgical extraction of the deciduous and supernumerary teeth. The remaining unerupted permanent teeth were facilitated with traction or extracted followed by implantation or restoration. Repositioning of the maxilla and mandible via orthognathic surgery was also applied to correct skeletal and occlusal discrepancies and lead to satisfying results.

Cleidocranial dysplasia with hypermobile Ehlers-Danlos syndrome: A case report

Cleidocranial dysplasia (CCD) is a rare genetic skeletal syndrome. The most common features are open fontanelles, hypertelorism, mid-face retrusion, hypoplasia, or aplasia of the clavicles leading to excessive shoulder mobility, dental abnormalities such as supernumerary, and impacted teeth. This case report describes a 31-year-old male with CCD with several unusual symptoms like generalized joint hypermobility, skin laxity, and smooth skin, which leads to set a diagnosis of hypermobile Ehlers-Danlos syndrome (hEDS). To our knowledge, this is the first case report in the literature that describes a patient with these 2 distinct syndromes CCD and hEDS.

An overview of the intraoral features and craniofacial morphology of growing and adult Japanese cleidocranial dysplasia subjects

BACKGROUND

Orthodontic treatment for cleidocranial dysplasia (CCD) requires an understanding of the nature of the retained deciduous teeth, supernumerary teeth, delayed eruption of the permanent teeth, and craniofacial morphology from childhood to adulthood. This study aimed to provide an overview of the intraoral and craniofacial characteristics of growing and adult Japanese CCD subjects.

METHODS

We assessed cross-sectionally the intraoral features of 28 CCD subjects (males, 15.3 ± 7.0 years; females, 15.2 ± 5.1 years) using orthopantomograms and photographs. Mean facial diagrams (profilograms) of 3 age groups (5-10 years, 11-14 years, over 15 years: adult) were constructed, and linear and angular measurements of 2 age groups (under 15 years, adult) were performed by using cephalograms. The data were compared with Japanese standards.

RESULTS

A mean of 11.7 and 8.4 retained deciduous teeth, 10.4 and 15.8 erupted permanent teeth were observed in the adult males and females, and a mean of 6.8 and 5.3 supernumerary teeth were observed in all males and females, respectively. A positive correlation was found between the number of supernumerary teeth and the age at initial visit. Cephalometric analysis showed an average to anteriorly positioned maxilla, a tendency for counter-clockwise rotation of the ramus, and a prognathic mandible in all groups.

CONCLUSIONS

The number of supernumerary teeth increased with age. The maxilla was average to anteriorly positioned, and the mandible was counter-clockwise rotated and prognathic for all groups. These characteristic craniofacial morphologies and changes of intraoral conditions at different ages in CCD patients should be considered when proposing rational orthodontic treatment plans.

Organoids from human tooth showing epithelial stemness phenotype and differentiation potential

Insight into human tooth epithelial stem cells and their biology is sparse. Tissue-derived organoid models typically replicate the tissue’s epithelial stem cell compartment. Here, we developed a first-in-time epithelial organoid model starting from human tooth. Dental follicle (DF) tissue, isolated from unerupted wisdom teeth, efficiently generated epithelial organoids that were long-term expandable. The organoids displayed a tooth epithelial stemness phenotype similar to the DF’s epithelial cell rests of Malassez (ERM), a compartment containing dental epithelial stem cells. Single-cell transcriptomics reinforced this organoid-ERM congruence, and uncovered novel, mouse-mirroring stem cell features. Exposure of the organoids to epidermal growth factor induced transient proliferation and eventual epithelial-mesenchymal transition, highly mimicking events taking place in the ERM in vivo. Moreover, the ERM stemness organoids were able to unfold an ameloblast differentiation process, further enhanced by transforming growth factor-β (TGFβ) and abrogated by TGFβ receptor inhibition, thereby reproducing TGFβ's known key position in amelogenesis. Interestingly, by creating a mesenchymal-epithelial composite organoid (assembloid) model, we demonstrated that the presence of dental mesenchymal cells (i.e. pulp stem cells) triggered ameloblast differentiation in the epithelial stem cells, thus replicating the known importance of mesenchyme-epithelium interaction in tooth development and amelogenesis. Also here, differentiation was abrogated by TGFβ receptor inhibition. Together, we developed novel organoid models empowering the exploration of human tooth epithelial stem cell biology and function as well as their interplay with dental mesenchyme, all at present only poorly defined in humans. Moreover, the new models may pave the way to future tooth-regenerative perspectives.

The Association Between Runx Signaling and Craniofacial Development and Disease

PURPOSE OF REVIEW

The Runx family genes (Runx1, Runx2, Runx3, and Cbfb) are important transcriptional regulators in the development of various tissues. We herein highlight the roles of the Runx family genes in morphogenesis in the craniofacial regions and in the pathogenesis of congenital morphological problems in these regions.

RECENT FINDINGS

A recent analysis using conditional Runx mutant animals and a human genetic study identified the novel roles of Runx genes in the development of the tooth, salivary glands, and the palate. In an animal study, Runx1/Cbfb signaling was found to regulate the Lgr5 expression and maintain the stem cells in the dental epithelium in the growing incisors. Aberrant Runx1/Cbfb signaling induced male-specific involution of the convoluted granular cell differentiation of the submandibular gland. In palatogenesis, Runx1/Cbfb signaling regulated the Tgfb3 expression in the fusing palatal epithelium through Stat3 activation. The combination of a human genetic study and a phenotype analysis of mutant animals revealed the various roles of Runx genes in the development of the tooth, palate, and salivary glands. Runx genes have functional redundancy in various tissues, which still hinder the roles of Runx genes in morphogenesis. Future studies may reveal the novel roles of Runx signaling.

Cleidocranial dysplasia and novel RUNX2 variants: dental, craniofacial, and osseous manifestations

Cleidocranial dysplasia (CCD) is a skeletal disorder affecting cranial sutures, teeth, and clavicles, and is associated with the RUNX2 mutations. Although numerous patients have been described, a direct genotype–phenotype correlation for RUNX2 has been difficult to establish. Further cases must be studied to understand the clinical and genetic spectra of CCD.

Identification of a familial cleidocranial dysplasia with a novel RUNX2 mutation and establishment of patient-derived induced pluripotent stem cells

Cleidocranial dysplasia (CCD) is an autosomal dominant hereditary disease associated with the gene RUNX2. Disease-specific induced pluripotent stem cells (iPSCs) have emerged as a useful resource to further study human hereditary diseases such as CCD. In this study, we identified a novel CCD-specific RUNX2 mutation and established iPSCs with this mutation. Biopsies were obtained from familial CCD patients and mutation analyses were performed through Sanger sequencing and next generation sequencing. CCD-specific human iPSCs (CCD-hiPSCs) were established and maintained under completely defined serum, feeder, and integration-free condition using a non-integrating replication-defective Sendai virus vector. We identified the novel mutation RUNX2_c.371C>G and successfully established CCD-hiPSCs. The CCD-hiPSCs inherited the same mutation, possessed pluripotency, and showed the ability to differentiate the three germ layers. We concluded that RUNX2_c.371C>G was likely pathogenic because our results, derived from next generation sequencing, are supported by actual clinical evidence, familial tracing, and genetic data. Thus, we concluded that hiPSCs with a novel CCD-specific RUNX2 mutation are viable as a resource for future studies on CCD.

Sequencing analysis of exons 5 and 6 in RUNX2 in non-syndromic patients with supernumerary tooth in Kelantan, Malaysia

OBJECTIVE

The aim of this study is to do a sequencing analysis of RUNX2 in non-syndromic patients with supernumerary tooth.

MATERIALS AND METHODS

Fifty-three patients with supernumerary tooth were identified retrospectively from 1,275 radiographic reviews who attended the Hospital Universiti Sains Malaysia (USM) Dental Clinic. Informed consent was obtained from the patients prior to the study. Blood samples were collected from 41 patients and DNA extractions were performed out of which 10 samples were chosen randomly for PCR amplification using designated primers for RUNX2 followed by DNA sequencing analysis.

RESULTS

This study involved 28 male patients (68.3%) and 13 female patients (31.7%) with a gender ratio of 2.2:1 and mean age of 15.9 ± 6.2 years. DNA extraction yielded ~ 40 ng/μl of concentrated DNA, and each DNA sample had more than 1500 bp of DNA length. The purity ranged between 1.8 and 2.0. DNA sequencing analysis did not reveal any mutations in exons 5 and 6 of RUNX2.

CONCLUSION

This study did not reveal any mutations in exons 5 and 6 of RUNX2 in non-syndromic patients with supernumerary tooth.

CLINICAL RELEVANCE

Analysis of mutations in RUNX2 is important to enhance the understanding of tooth development in humans.

A Prosthodontic Approach as a Complementary Solution for a Complicated Orthodontic Treatment of a Patient with Cleidocranial Dysplasia

This clinical report describes a prosthodontic rehabilitation of a 29-year-old patient with cleidocranial dysplasia (CCD), who, after completing an orthodontic treatment, was not satisfied with the aesthetic outcome. Besides aesthetics, the patient complained about mastication muscles pain, and clicking while eating but was not aware about her unilateral open bite on the right side. The aim of this treatment was to improve smile appearance and patient's well-being, as well as to restore the proper occlusal vertical dimension (OVD) along with complete intercuspation and to establish masticatory function. The first phase of the treatment concentrated on eliminating the muscle pain and temporomandibular joint (TMJ) clicking with a repositioning splint. During the second phase, the functional and aesthetic rehabilitation was obtained using adhesive prosthesis overlays and veneers.

Estrogen deficiency affects tooth formation and gene expression in the odontogenic region of female rats

BACKGROUND

There is some evidence that estrogen regulates the expression of several genes in different cells, including dental cells. Therefore, the aim of this study was to investigate the role of estrogen deficiency during tooth development regarding tooth structure morphology and its impact on the expression of odontogenesis-related genes.

METHODS

A total of 40 female Wistar rats was divided into OVX (estrogen deficiency) and Sham (control) groups. Bilateral ovariectomy was performed in the OVX group, while Sham surgery was performed in the control group at the age of 21 days. At an age of 56 days, 16 rats were euthanized for gene expression analyses of Bmp4, Smad6, Tgfb1 and Runx2. At the age of 63 days, the remaining rats were euthanized for histological and morphometric analyses of teeth. The mandibles of the rats were submitted to μCT analysis. Tooth structures (enamel, dentin and dental pulp) were analyzed. T test was used to compare the mean differences between groups (p<0.05).

RESULTS

In the μCT analysis, enamel and dentin thickness were significantly increased in the control group (p<0.0001). Pulp dimensions were significantly larger in the OVX group (p<0.0001). A reduction of tooth structures in the OVX group was confirmed in HE staining. Smad6 was differentially expressed in the OVX group (p=0.04).

CONCLUSION

Estrogen deficiency affects gene expression in the odontogenic region and tooth structure morphology.

4-Hexylresorcinol Administration Increases Dental Hard Tissue Formation and Incisor Eruption Rate in Rats

Dental hard tissue formation and bone turnover are required for tooth eruption. 4-Hexylresorcinol (4HR) accelerates tooth movement by increasing bone turnover in orthodontic treatment. This study aimed to evaluate the following: (1) the effect of 4HR application on the expression of proteins associated with tooth formation, and (2) the effect of 4HR application on mandibular incisor eruption rate in a rat model. Primary cultured pulp cells received either 4HR (1 to 100 µM) or solvent only; western blotting was performed for transforming growth factor-beta 1 (TGF-β1), bone morphogenic protein-2/4 (BMP-2/4), runt-related transcription factor 2 (Runx2), osterix (OSX), dentin sialophosphoprotein (DSPP), and parathyroid hormone-related protein receptor (PTHrP-R). In in vivo study, rats (15 males and 15 females) received either solvent or 0.128 mg/kg or 12.8 mg/kg of 4HR via subcutaneous injection; mandibular incisor eruption rate was subsequently recorded. Immunohistochemical staining and western blotting for TGF-β1, BMP-2/4, Runx2, OSX, DSPP, and PTHrP-R were performed in the mandibular tissue samples. 4HR administration was found to increase TGF-β1, BMP-2/4, Runx2, OSX, DSPP, and PTHrP-R expression in both cell culture and tissue samples. Immunohistochemical staining of some markers showed site-specific expression, thereby indicating programmed differentiation of odontoblasts and ameloblasts. The eruption rate was significantly higher in the 12.8 mg/kg 4HR-administered group than in the untreated control (p = 0.001 and 0.010 for males and females, respectively). Collectively, 4HR administration increased the expression of markers related to dental hard tissue formation and accelerated the eruption rate of incisors in rats.

Three-dimensional evaluation of morphology and position of impacted supernumerary teeth in cases of cleidocranial dysplasia

Cleidocranial dysplasia (CCD) is a congenital anomaly characterized by the presence of impacted supernumerary teeth and delayed eruption of permanent teeth. However, there has been no detailed investigation on supernumerary teeth in patients with CCD using three-dimensional (3D) imaging techniques. The purpose of this study was to elucidate the morphology and position of supernumerary teeth using 3D images reconstructed from cone-beam computed tomography (CBCT) data in a group of five Japanese subjects (male, 3; female, 2; age, 15.0-25.4 years) with CCD. All five subjects exhibited supernumerary teeth (39 in total; average, 7.8; range, 1-15). All supernumerary teeth were impacted and existed as pairs with adjacent permanent teeth. Comparison of the size (the crown and dental-root lengths, the crown mesiodistal and buccolingual diameters), the number of cusps and dental roots, the position, and direction of supernumerary teeth in relation to the adjacent permanent teeth was analyzed. The results of relationship analyses revealed that, at sites other than the molar region, supernumerary teeth were positioned on the lingual and distal sides and supernumerary teeth resembled the morphology of their adjacent permanent teeth in terms of the number of cusps but were smaller than the adjacent permanent teeth. In the molar region, supernumerary teeth were microdontia, which were apparently small and obscure morphologically. In addition, while all adjacent permanent teeth exhibited normal direction, five supernumerary teeth exhibited inverse direction. The findings of this study will improve our understanding of the characteristics of CCD and provide important information for the pathophysiology and clinical treatment.

Biomechanical stress regulates mammalian tooth replacement via the integrin β1-RUNX2-Wnt pathway

Renewal of integumentary organs occurs cyclically throughout an organism's lifetime, but the mechanism that initiates each cycle remains largely unknown. In a miniature pig model of tooth development that resembles tooth development in humans, the permanent tooth did not begin transitioning from the resting to the initiation stage until the deciduous tooth began to erupt. This eruption released the accumulated mechanical stress inside the mandible. Mechanical stress prevented permanent tooth development by regulating expression and activity of the integrin β1-ERK1-RUNX2 axis in the surrounding mesenchyme. We observed similar molecular expression patterns in human tooth germs. Importantly, the release of biomechanical stress induced downregulation of RUNX2-wingless/integrated (Wnt) signaling in the mesenchyme between the deciduous and permanent tooth and upregulation of Wnt signaling in the epithelium of the permanent tooth, triggering initiation of its development. Consequently, our findings identified biomechanical stress-associated Wnt modulation as a critical initiator of organ renewal, possibly shedding light on the mechanisms of integumentary organ regeneration.

Case series of cleidocranial dysplasia: Radiographic follow-up study of delayed eruption of impacted permanent teeth

This report describes 3 cases of cleidocranial dysplasia (CCD) and presents relevant findings on long-term follow-up radiographic images of impacted permanent teeth with delayed eruption. Radiographic images of 3 CCD patients were reviewed retrospectively. These images were mainly composed of panoramic and skull radiographs, and the follow-up periods were 3, 13, and 13 years, respectively. The distinct features revealed by the images were described, and the eruption state of impacted permanent teeth was evaluated. The features common to the 3 cases were multiple supernumerary teeth, the presence of Wormian bone, underdevelopment of the maxilla and the maxillary sinus, and clavicular hypoplasia. The eruption of impacted permanent teeth was not observed without proper dental treatment in adult CCD cases, even after long time periods had elapsed. When proper orthodontic force was applied, tooth movement was observed in a manner not significantly different from the general population.

Supernumerary teeth of permanent dentition in patients with neurofibromatosis type 1

PURPOSE

The purpose of the study was the investigation of supernumerary teeth (ST) in the permanent dentition of patients with neurofibromatosis type 1 (NF1).

MATERIAL AND METHODS

The panoramic radiographs of 200 NF1 patients were analysed for ST. The potential impact of certain neurogenic facial tumours on the measured variable was investigated separately. The results were compared to dental findings in panoramic radiographs of 200 age- and sex-matched controls.

RESULTS

The total number of ST in all individuals was 23 in 12 patients (3% of total population). However, all ST had developed in the group of NF1 patients (6%), (p = 0.0004). ST were particularly common distal to the molar region. Although ST occur in the region of facial plexiform neurofibroma, the numerical aberrations of the dentition are independent of specific type of facial nerve sheath tumour.

CONCLUSION

The unusual accumulation of ST in the terminal sections of molar development could be an indicator of preferred points of developmental disorder, in which the genetic predisposition of the patient is involved. Reviewing the results of other NF1 patient collectives is desirable.

Third Dentition Is the Main Cause of Premolar Supernumerary Tooth Formation

While the prevalence of supernumerary teeth (ST) is high in permanent dentition, the etiology of ST in humans remains unclear. However, multiple murine models of ST have elaborated on dated mechanisms traditionally ascribed to ST etiology: one involves the rescue of rudimental teeth, and the second considers the contribution of odontogenic epithelial stem cells. It remains unclear whether these mechanisms of ST formation in mice are applicable to humans. The third dentition is usually regressed apoptotic-that is, the teeth do not completely form in humans. Recently, it was suggested that ST result from the rescue of regression of the third dentition in humans. The present investigation evaluates the proportion of collected general ST cases that evinced a third dentition based on the clinical definition of ST derived from the third dentition. We also investigated the contribution of SOX2-positive odontogenic epithelial stem cells to ST formation in humans. We collected 215 general ST cases from 15,008 patients. We confirmed that the general characteristics of the collected ST cases were similar to the results from previous reports. Of the 215 cases, we narrowed our analysis to the 78 patients who had received a computed tomography scan. The frequency of ST considered to have been derived from the third dentition was 26 out of 78 cases. Evidence of a third dentition was especially apparent in the premolar region, was more common in men, and was more likely among patients with ≥3 ST. SOX2-positive odontogenic epithelial stem cells within the surrounding epithelial cells of developing ST were observed in non-third dentition cases and not in third dentition cases. In conclusion, the third dentition is the main cause of ST in humans. The odontogenic epithelial stem cells may contribute to ST formation in cases not caused by a third dentition.

The Treatment Strategy of Cleidocranial Dysplasia: Combined Orthodontic and Orthognathic Treatment

Cleidocranial dysplasia is a rare autosomal-dominant condition that affects ossification. The main symptoms of this cleidocranial dysplasia patient include craniofacial abnormalities, hypoplasia of clavicles, narrow thorax, retarded exfoliation of deciduous teeth, retarded eruption of permanent teeth, and multiple impacted supernumerary teeth. The aim of this treatment was to correct the craniofacial abnormalities and provide an adequate functional reconstruction of the occlusion. The patient was treated with a multidisciplinary therapeutic protocol including removal of supernumerary teeth, surgical exposure of impacted teeth, orthodontic, and orthognathic surgery. After 6 years' follow-up, the treatment objectives of acceptable occlusion, normal function, and acceptable profile were achieved.

RUNX2 mutation reduces osteogenic differentiation of dental follicle cells in cleidocranial dysplasia

Disturbed permanent tooth eruption is common in cleidocranial dysplasia (CCD), a skeletal disorder caused by heterozygous mutation of RUNX2, but the mechanism underlying is still unclear. As it is well known that dental follicle cells (DFCs) play a critical role in tooth eruption, the changed biological characteristics of DFCs might give rise to disturbance of permanent tooth eruption in CCD patients. Thus, primary DFCs from one CCD patient and normal controls were collected to investigate the effect of RUNX2 mutation on the bone remodeling activity of DFCs and explore the mechanism of impaired permanent tooth eruption in this disease. Conservation and secondary structure analysis revealed that the RUNX2 mutation (c.514delT, p.172fs) found in the present CCD patient was located in the highly conserved RUNT domain and converted the structure of RUNX2. After osteogenic induction, we found that the mineralised capacity of DFCs and the expression of osteoblast-related genes, including RUNX2, ALP, OSX, OCN and Col Iα1, in DFCs was severely interfered by the RUNX2 mutation found in CCD patients. To investigate whether the osteogenic deficiency of DFCs from the CCD patient can be rescued by RUNX2 restoration, we performed 'rescue' experiments. Surprisingly, the osteogenic deficiency and the abnormal expression of osteoblast-associated genes in DFCs from the CCD patient were almost rescued by overexpression of wild-type RUNX2 using lentivirus. All these findings indicate that RUNX2 mutation can reduce the osteogenic capacity of DFCs through inhibiting osteoblast-associated genes, thereby disturbing alveolar bone formation, which serves as a motive force for tooth eruption. This effect may provide valuable explanations and implications for the mechanism of delayed permanent tooth eruption in CCD patients.

Failure of Eruption of Permanent Tooth

Primary failure of eruption (PFE) is a rare condition that can lead to posterior open bites. It is difficult to diagnose and difficult to treat. PFE appears to be a condition that predominantly affects the molar dentition. The increased frequency of hypodontia in affected individuals and common findings of a family history regarding tooth eruption problems suggests a significant genetic component to the etiology of this rare condition.

Ablation of Runx2 in Ameloblasts Suppresses Enamel Maturation in Tooth Development

Runt-related transcription factor 2 (Runx2) is involved in the early stage of tooth development. However, only few studies have reported the role of Runx2 in enamel development, which may be attributed to that Runx2 full knockout mice cannot survive after birth. In the present study, we successfully established a Runx2-deficient mouse model using a conditional knockout (cKO) method. We observed a significant reduction in the degree of mineralization and the decreased size of enamel rods in cKO mice. Histological analysis showed the retained enamel proteins in enamel layer at maturation stage in cKO molars. Further analysis by qRT-PCR revealed that the expressions of genes encoding enamel structure proteins, such as amelogenin (AMELX), ameloblastin (AMBN) and enamelin (ENAM), were increased in cKO enamel organs. On the other hand, the expression of kallikrein-related peptidase-4 (KLK4) at the mRNA and protein levels was dramatically decreased from late secretory stage to maturation stage in cKO enamel organs, while the expression of matrix metalloproteinase-20 (MMP-20) was not significantly altered. Finally, immunohistochemistry indicated that the uptake of amelogenins by ameloblasts was significantly decreased in cKO mice. Taken together, Runx2 played critical roles in controlling enamel maturation by increasing synthesis of KLK4 and decreasing synthesis of AMELX, AMBN and ENAM.

Multiple supernumerary teeth in a likely syndromic individual from prehistoric Illinois

OBJECTIVE

This paper reports the first published case of a prehistoric human with five or more supernumerary teeth. Such cases are often neglected in paleopathology, in part due to a gap between the medicodental and anthropological literature leading to the view in anthropology that supernumerary teeth are curious anomalies rather than pathologies.

DESIGN

Reconstruction and pathological description of the skeletal remains were performed according to standard osteological protocols. Each supernumerary tooth was categorized based on its morphology, location, and orientation. The dental characteristics of the individual were compared to published norms for incidences of syndromic and non-syndromic supernumerary teeth and a differential diagnosis was subsequently performed.

RESULTS

Six supernumerary teeth and one deciduous tooth were identified. Additionally, the individual suffered from impacted teeth, dilacerated roots, and extensive sutural anomalies (including retention of the metopic suture into adulthood and an unusually high number of sutural bones). The morphology and location of the supernumerary teeth, in conjunction with the suite of other symptoms, are highly unusual among non-syndromic patients and therefore are indicative of a complex genetic disorder.

CONCLUSIONS

The individual reported here almost certainly suffered from a genetic disorder or syndrome resulting in extensive dental and sutural abnormalities. Despite a lack of post-cranial involvement, a tentative diagnosis of Cleidocranial Dysplasia was made on the basis that mutations in the RUNX2 gene may cause the dental symptoms without any pathology of the clavicle.

Abnormal bone remodelling activity of dental follicle cells from a cleidocranial dysplasia patient

OBJECTIVES

To explore the role of dental follicle cells (DFCs) with a novel cleidocranial dysplasia (CCD) causative gene RUNX2 mutation (DFCs^RUNX2+/m ) in delayed permanent tooth eruption.

MATERIALS AND METHODS

A CCD patient with typical clinical features was involved in this study. DFCs^RUNX2+/m were cultured and DNA was extracted for RUNX2 mutation screening. Measurements of cell proliferation, alkaline phosphatase (ALP) activity, alizarin red staining and osteoblast-specific genes expression were performed to assess osteogenesis of DFCs^RUNX2+/m . Co-culture of DFCs and peripheral blood mononuclear cells (PBMCs), followed tartrate-resistant acid phosphatase (TRAP) staining, real-time PCR and western blot were performed to evaluate osteoclast-inductive capacity of DFCs^RUNX2+/m .

RESULTS

A missense RUNX2 mutation (c. 557G>C) was found in DFCs^RUNX2+/m from the CCD patient. Compared with normal controls, this mutation did not affect the proliferation of DFCs^RUNX2+/m , but down-regulated the expression of osteogenesis-related genes, leading to a decrease in ALP activity and mineralisation. Co-culture results showed that DFCs^RUNX2+/m reduced the formation of TRAP⁺ multinucleated cells and the expression of osteoclastogenesis-associated genes. Furthermore, the mutation reduced the ratio of RANKL/OPG in DFCs^RUNX2+/m .

CONCLUSIONS

DFCs^RUNX2+/m disturbs bone remodelling activity during tooth eruption through RANK/RANKL/OPG signalling pathway and may thus be responsible for impaired permanent tooth eruption in CCD patients.

Characterization of dental phenotype in patients with cleidocranial dysplasia using longitudinal data

OBJECTIVE

To investigate the characteristics of the dental phenotype in patients with cleidocranial dysplasia (CCD) using longitudinal data.

MATERIALS AND METHODS

Twelve unrelated Korean CCD patients were observed using a longitudinal series of radiographs and clinical photographs. Statistical analysis was performed on the dental phenotypic data.

RESULTS

Although dysplasia of the clavicles, open fontanelle, and wormian bone were observed in all 12 patients, delayed fusion of the mandibular symphysis was found in four patients. One patient did not have a supernumerary tooth (ST). However, 62 STs were found in 11 patients (mean, 5.6 per patient; range of ST emergence, 5 years 6 months-14 years 8 months; developing position, occlusal to the permanent incisors, canines, and premolars and distal and apical to the permanent molars). The mandibular premolar region was the most frequent area of ST development (50.0%, P < .001). All 12 patients showed impacted permanent teeth (IPT), including one patient without ST (mean, 17.8 per patient). Impaction occurred most frequently in the mandibular premolar region and least frequently in the maxillary molar region (93.8% vs 39.6%, P < .01). The ratio of spontaneous eruption of IPT after removal of retained deciduous teeth and/or ST was highest for the maxillary and mandibular incisors (all 54.6%) and lowest for the mandibular canines and premolars (26.7% and 28.9%, respectively); however, the difference was not significant.

CONCLUSIONS

The emergence time and development position of ST and the root development of IPT should be considered to determine the timing for the removal of ST and forced eruption of IPT.

Mesenchymal Wnt/β-catenin signaling limits tooth number

Tooth agenesis is one of the predominant developmental anomalies in humans, usually affecting the permanent dentition generated by sequential tooth formation and, in most cases, caused by mutations perturbing epithelial Wnt/β-catenin signaling. In addition, loss-of-function mutations in the Wnt feedback inhibitor AXIN2 lead to human tooth agenesis. We have investigated the functions of Wnt/β-catenin signaling during sequential formation of molar teeth using mouse models. Continuous initiation of new teeth, which is observed after genetic activation of Wnt/β-catenin signaling in the oral epithelium, was accompanied by enhanced expression of Wnt antagonists and a downregulation of Wnt/β-catenin signaling in the dental mesenchyme. Genetic and pharmacological activation of mesenchymal Wnt/β-catenin signaling negatively regulated sequential tooth formation, an effect partly mediated by Bmp4. Runx2, a gene whose loss-of-function mutations result in sequential formation of supernumerary teeth in the human cleidocranial dysplasia syndrome, suppressed the expression of Wnt inhibitors Axin2 and Drapc1 in dental mesenchyme. Our data indicate that increased mesenchymal Wnt signaling inhibits the sequential formation of teeth, and suggest that Axin2/Runx2 antagonistic interactions modulate the level of mesenchymal Wnt/β-catenin signaling, underlying the contrasting dental phenotypes caused by human AXIN2 and RUNX2 mutations.

Supernumerary Molars and Wisdom Tooth Shape Alterations in Patients with Neurofibromatosis Type 1

Objectives

The purpose of the present study was the systematic investigation of numerical and morphological aberrations of teeth in the wisdom teeth region in neurofibromatosis type 1 patients.

Material and Methods

The panoramic radiographs of 179 patients were analysed for supernumerary molars and dysplastic wisdom teeth with special reference to facial tumour type. The results were compared to radiographic findings obtained in panoramic radiographs of age- and sex-matched controls.

Results

The total number of dysplastic or supernumerary molars was 21 (17 individuals, 4.75%) and predominantly a finding of the maxilla (maxilla: 15, mandible: 1, maxilla and mandible: 1). Differences of dental findings between neurofibromatosis type 1 (NF1) patients (n = 15) and the control group (n = 2) were statistically significant (P < 0.01). All individuals with supernumerary molars were diagnosed as being affected with NF1. This difference achieved statistical significance when it was considered that the event may occur at least once per quadrant, and thus the individual potentially needs to be considered four times (P = 0.0038).

Conclusions

This investigation revealed that supernumerary molars and aberrations in wisdom tooth form are more common in patients than in age- and sex-matched controls. There is no association between these findings and a specific feature of the disease, id est facial manifestation of a trigeminal nerve sheath tumour (plexiform neurofibroma). The cause of this phenomenon is unknown. A review of these dental findings on other neurofibromatosis type 1 study groups should be attempted.

Craniofacial features of cleidocranial dysplasia

Cleidocranial dysplasia (CCD) is an autosomal-dominant malformation syndrome affecting bones and teeth. The most common skeletal and dental abnormalities in affected individuals are hypoplastic/aplastic clavicles, open fontanelles, short stature, retention of primary teeth, delayed eruption of permanent teeth, supernumerary teeth, and multiple impacted teeth. Treatment of CCD requires a multidisciplinary approach that may include dental corrections, orthognathic surgery and cranioplasty along with management of any complications of CCD. Early diagnosis of this condition enables application of the treatment strategy that provides the best quality of life to such patients. Notably, Runx2 gene mutations have been identified in CCD patients. Therefore, further elucidation of the molecular mechanism of supernumerary teeth formation related to Runx2 mutations may improve understanding of dental development in CCD. The insights into CCD pathogenesis may assist in the development of new treatments for CCD.

Maxillary sinuses and midface in patients with cleidocranial dysostosis

The cleidocranial dysplasia is general skeletal disorder with an autosomal dominant inheritance. It is manifested by many craniofacial abnormalities, of which the maxillary hypoplasia is the most evident. The aim of the study was to use CBCT to evaluate the volume of the maxillary sinuses and the dimensions of maxillae in patients with CCD and compare them with healthy individuals. Files of four children with cleidocranial dysplasia were investigated. Volume of every maxillary sinus as well as two dimensional measurements of distances between particular points of interest located on surface of maxilla were calculated from reconstructed CBCT examination. Data were compared with a control group. Statistical analysis was performed. Linear and volumetric data obtained using CBCT was collected and compared with a control group. All affected children had both maxillary sinus volume and maxillary dimensions smaller than control values. The maxillary sinuses were underdeveloped up to half of normal values. The largest differences were recorded in vertical linear dimensions of the maxillae. Horizontal dimensions were also lower. There are morphological modifications of bone tissue which accompany CCD. It seems that these changes occur on the midfacial region and to a greater extent concern the maxillary sinus volume.

The Biology Underlying Abnormalities of Tooth Number in Humans

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.

A novel, complex RUNX2 gene mutation causes cleidocranial dysplasia

Background

Haploinsufficiency of the runt-related transcription factor 2 (RUNX2) gene is known to cause cleidocranial dysplasia (CCD). Here, we investigated a complex, heterozygous RUNX2 gene mutation in a Chinese family with CCD and the pathogenesis associated with the variations.

Methods

Genomic DNA extracted from peripheral venous blood was taken from the proband, her parents and 3 siblings, and 150 normal controls. Analysis of their respective RUNX2 gene sequences was performed by PCR amplification and Sanger sequencing. Pathogenesis associated with RUNX2 mutations was investigated by performing bioinformatics, real-time PCR, western blot analysis, and subcellular localization studies.

Results

We identified 2 complex heterozygous mutations involving a c.398–399 insACAGCAGCAGCAGCA insertion and a c.411–412 insG frameshift mutation in exon 3 of the RUNX2 gene. The frameshift mutation changed the structure of the RUNX2 protein while did not affect its expression at the mRNA level. Transfection of HEK293T cells with a plasmid expressing the RUNX2 variant decreased the molecular weight of the variant RUNX2 protein, compared with that of the wild-type protein. Subcellular localization assays showed both nuclear and cytoplasmic localization for the mutant protein, while the wild-type protein localized to the nucleus.

Conclusions

Our findings demonstrated that the novel c.398–399insACAGCAGCAGCAGCA mutation occurred alongside the c.411–412insG frameshift mutation, which resulted in RUNX2 truncation. RUNX2 haploinsufficiency was associated with CCD pathogenesis. These results extend the known mutational spectrum of the RUNX2 gene and suggest a functional role of the novel mutation in CCD pathogenesis.

Bilateral Transverse Mandibular Second Molars: A Case Report

Impaction of mandibular second permanent molars is a rare occurrence, with prevalence rates reported to be between 0.65% and 2.0%. In the absence of systemic conditions, impactions are usually unilateral. There appears to be no consensus as to the optimal treatment for impacted mandibular second molars and treatment plans will be based upon the individual case. Treatment may involve orthodontics and/or various surgical techniques, and early diagnosis is important. This paper presents an unusual case of bilateral transverse impaction of both mandibular second and third molars that was diagnosed at 18 years of age. All impacted molars were extracted.

Late-Developing Supernumerary Premolars: Analysis of Different Therapeutic Approaches

This case series describes the different potential approaches to late-developing supernumerary premolars (LDSP). LDSP are supernumerary teeth (ST) formed after the eruption of the permanent dentition; usually they develop in the premolar region of the upper and lower jaw. The choice to extract or to monitor the LDSP depends on many factors and has to be carefully planned due to the several risks that either the monitoring or the extraction could provoke. These four cases of LDSP showed different treatment plan alternatives derived from a scrupulous assessment of the clinical and radiographic information.

Cleidocranial Dysplasia: A Clinico-radiographic Spectrum with Differential Diagnosis

INTRODUCTION

Cleidocranial dysplasia (CCD) is characterized by aplasia or hypoplasia of the clavicles, characteristic craniofacial malformations, and the presence of numerous supernumerary and unerupted teeth. It affects bones derived from both intra-membranous and endochondral ossification. Incidence has been reported as 1 in 10,00,000. It is caused by mutation in the gene encoding transcription factor Core Binding Factor Subunit Alpha l (CBFAl) or Runt related transcription factor 2 (RUNX2).

CASE REPORT

This presentation discusses the clinical and radiographic features of a familial case of cleidocranial dysplasia occurring in a father and a child. All the clinical and radiographic features, except that of the chest x-ray, were more prominent in the child than the father. This supports the fact that CCD is transmitted by an autosomal-dominant mode of inheritance with high penetrance and variable expressivity. It is sporadic in about 40% of cases. Each child of an individual with CCD has a 50% chance of in heriting the mutation.

CONCLUSION

Diagnosis is mostly made on the basis of clinical and radiographic features. Molecular genetic testing such as sequence analysis or deletion analysis can be used in cleidocranial dysplasia. Some cases are diagnosed through incidental findings by physicians, treating patients for unrelated conditions. Treatment of these patients requires a multidisciplinary approach which includes orthopaedic and dental corrections along with management of any complications of cleidocranial dysplasia.

Cleidocranial dysplasia: A report of two cases with brief review

Cleidocranial dysplasia (CCD) is a genetic disorder primarily causing dysplasia of bones and teeth with autosomal dominant inheritance pattern. Affected individuals presented with several skeletal and dental abnormalities mainly hypoplasia of clavicles, open fontanelles, short stature, retention of primary teeth, supernumerary teeth, delayed eruption of permanent teeth, multiple impacted permanent teeth etc. The present series of two cases illustrates the clinical and radiological features of pediatric patients with cleidocranial dysplasia. The early diagnosis of the condition helps in proper orientation of the treatment thereby offering better quality of life to such patients.

Cleidocranial dysplasia syndrome (CCD) with an unusual finding in a young patient

Cleidocranial dysplasia (CCD), an autosomal dominant disorder with a prevalence of 1 in 1,000,000 individuals, presents with a wide range of variability. Dentists are often the first to encounter patients with CCD, some of whom do not show typical manifestations. Since it has similar features to other pathologies, CCD is misdiagnosed as other conditions. A 10-year-old boy suffering from CCD was misdiagnosed as having rickets and was referred for non-eruption of a few permanent teeth along with an unaesthetic facial appearance. Clinically and radiologically, a diagnosis of CCD was made. Currently, management of this patient's orofacial manifestations is underway.

Restorative treatment strategies for patients with cleidocranial dysplasia

OBJECTIVE

To develop a suitable treatment strategy for patients with cleidocranial dysplasia (CCD) who miss the optimal early treatment stage.

MATERIALS AND METHODS

This study enrolled 15 patients with CCD who had all missed the optimal treatment stage and were diagnosed with CCD through clinical examinations and genetic tests. Based on the chief complaints and requirements of the patients, three different therapeutic schedules were devised for these patients. Schedules I (periodontal and endodontic treatments) and II (periodontal, endodontic and prosthodontic treatments) were used for patients with low requirements, whereas Schedule III (multidisciplinary strategy, including periodontal, endodontic, surgical, orthodontic and prosthodontic treatments) was used for patients with high requirements.

RESULTS

Schedules I, II and III were used in five, seven and three patients, respectively. Schedule III treatments produced the best outcomes in terms of occlusion and esthetics.

CONCLUSIONS

Schedule III based on a comprehensive multidisciplinary therapy is an ideal restorative therapeutic strategy and can achieve good outcomes for patients with CCD who missed the optimal treatment stage.

Cleidocranial dysplasia

Cleidocranial dysplasia (CCD) is an autosomal dominant disorder resulting in the skeletal and dental abnormalities due to the disturbance in ossification of the bones. Clavicle is the most commonly affected bone. The prevalence of CCD is one in millions of live births. In this report, we present a case of 10-years-old boy showing features of this condition.

Genetic background of supernumerary teeth

Supernumerary teeth (ST) are odontostomatologic anomaly characterized by as the existence excessive number of teeth in relation to the normal dental formula. This condition is commonly seen with several congenital genetic disorders such as Gardner's syndrome, cleidocranial dysostosis and cleft lip and palate. Less common syndromes that are associated with ST are; Fabry Disease, Ellis-van Creveld syndrome, Nance-Horan syndrome, Rubinstein-Taybi Syndrome and Trico–Rhino–Phalangeal syndrome. ST can be an important component of a distinctive disorder and an important clue for early diagnosis. Certainly early detecting the abnormalities gives us to make correct management of the patient and also it is important for making well-informed decisions about long-term medical care and treatment. In this review, the genetic syndromes that are related with ST were discussed.

Odontomas and supernumerary teeth: is there a common origin?

The aim of the present work is to analyze all scientific evidence to verify whether similarities supporting a unified explanation for odontomas and supernumerary teeth exist. A literature search was first conducted for epidemiologic studies indexed by PubMed, to verify their worldwide incidence. The analysis of the literature data shows some interesting similarities between odontomas and supernumerary teeth concerning their topographic distribution and pathologic manifestations. There is also some indication of common genetic and immuno-histochemical factors. Although from a nosological point of view, odontomas and supernumeraries are classified as distinct entities, they seem to be the expression of the same pathologic process, either malformative or hamartomatous.

Initiation of teeth from the dental lamina in the ferret

Mammalian tooth development is characterized by formation of primary teeth that belong to different tooth classes and are later replaced by a single set of permanent teeth. The first primary teeth are initiated from the primary dental lamina, and the replacement teeth from the successional dental lamina at the lingual side of the primary teeth. An interdental lamina connects the primary tooth germs together. Most mammalian tooth development research is done on mouse, which does not have teeth in all tooth classes, does not replace its teeth, and does not develop an interdental lamina. We have used the ferret (Mustela putorius furo) as a model animal to elucidate the morphological changes and gene expression during the development of the interdental lamina and the initiation of primary teeth. In addition we have analyzed cell-cell signaling taking place in the interdental lamina as well as in the successional lamina during tooth replacement. By 3D reconstructions of serial histological sections we observed that the morphogenesis of the interdental lamina and the primary teeth are intimately linked. Expression of Pitx2 and Foxi3 in the interdental lamina indicates that it has odontogenic identity, and there is active signaling taking place in the interdental lamina. Bmp4 is coexpressed with the stem cell factor Sox2 at its lingual aspect suggesting that the interdental lamina may retain competence for tooth initiation. We show that when tooth replacement is initiated there is Wnt pathway activity in the budding successional lamina and adjacent mesenchyme but no active Fgf or Eda signaling. Genes associated with human tooth replacement phenotypes, including Runx2 and Il11rα, are mostly expressed in the mesenchyme around the successional lamina in the ferret. Our results highlight the importance of the dental lamina in the mammalian tooth development during the initiation of both primary and replacement teeth.