Lateral incisor agenesis, canine impaction and characteristics of supernumerary teeth in a South European male population

Objective: To assess the prevalence of lateral incisor agenesis impacted canines and supernumerary teeth in a young adult male population. Materials and Methods: The panoramic radiographs of 1745 military students (mean age: 18.6 ± 0.52 years) who attended the Center of Aviation Medicine of the Armed Forces of Greece during the period 1997-2011 were initially analyzed for lateral incisor agenesis by two observers. After exclusion of the known orthodontic cases, a subgroup of 1636 examinees (mean age: 18.6 ± 0.44 years) was evaluated for canine impaction and supernumerary teeth. Results: Twenty-eight missing lateral incisors were observed in 22 military students, indicating an incidence of 1.3% in the investigated population. No lateral incisor agenesis was detected in the mandibular arch. A prevalence rate of 0.8% was determined for canine impaction in the sample of young adults. The majority of impacted teeth (86.7%) were diagnosed in the maxillary arch. Thirty-five supernumerary teeth were observed in 24 examinees (prevalence rate: 1.5%). The ratio of supernumerary teeth located in the maxilla versus the mandible was 2.2:1. The most common type of supernumerary tooth was the upper distomolar. Conclusion: The prevalence of lateral incisor agenesis, canine impaction, and supernumerary teeth ranged from 0.8 to 1.5% in the sample of male Greek military students.

Morphologic characteristics, location, and associated complications of maxillary and mandibular supernumerary teeth as evaluated using cone beam computed tomography.

OBJECTIVES To evaluate the location and morphologic characteristics of supernumerary teeth and to assess the frequency and extent of root resorption of adjacent teeth using cone beam computed tomography (CBCT). MATERIALS AND METHODS CBCT scans of 82 patients with supernumerary teeth in the maxilla and mandible were evaluated by two orthodontists independently. Data regarding the type, shape, and three-dimensional (3D) location of the supernumeraries including the frequency and extent of root resorption of adjacent teeth were recorded and evaluated for possible associations. RESULTS The study comprised a total of 101 supernumerary teeth. Most of the patients (80.5 per cent) exhibited one single supernumerary tooth, while 15.8 per cent had two and 3.7 per cent had three supernumeraries. Males were affected more than females with a ratio of 1.65:1. Mesiodentes were the most frequently diagnosed type of supernumerary teeth (48.52 per cent), followed by supernumerary premolars (23.76 per cent) and lateral incisors (18.81 per cent). Supernumeraries were most commonly conical in shape (42.6 per cent) with a normal or inclined vertical position (61.4 per cent). Root resorption of adjacent teeth was detected for 22.8 per cent of the supernumerary teeth, most frequently for supernumerary premolars. There was a significant association between root resorption of adjacent teeth and type and shape of tooth. Interrater agreement for the measurements performed showed kappa values ranging from 0.55 to 1 with a kappa value of 1 for type and shape of the supernumerary teeth. CONCLUSIONS CBCT provides 3D information about location and shape of supernumerary teeth as well as prevalence and degree of root resorption of neighbouring teeth with moderate to high interrater correlation.

Oral examination and radiographic evaluation of the dentition in wild cats from Namibia

Feline tooth resorption has been widely reported in domestic cats and sporadically described in other felidae. The goal of the present study was to determine the prevalence of tooth resorption and to report other dental problems in a population of wild felidae. Observations of dental disorders and anomalies were made in skulls from 73 wild felidae (cheetahs, leopards, caracals, African wildcats, and lions) originating from Namibia. In addition, radiographs were taken in 43 cases to determine signs of bone and root pathology. Radiographs showed varying stages of tooth resorption in 16.0% of the specimens. Other dental anomalies found included fused teeth, supernumerary roots, or missing teeth. The prevalence of dental resorption in wild felidae was lower than reported in the domestic cat.

A very rare cancer in Down syndrome: medulloblastoma. Epidemiological data from 13 countries

Persons with Down syndrome (DS) uniquely have an increased frequency of leukemias but a decreased total frequency of solid tumors. The distribution and frequency of specific types of brain tumors have never been studied in DS. We evaluated the frequency of primary neural cell embryonal tumors and gliomas in a large international data set. The observed number of children with DS having a medulloblastoma, central nervous system primitive neuroectodermal tumor (CNS-PNET) or glial tumor was compared to the expected number. Data were collected from cancer registries or brain tumor registries in 13 countries of Europe, America, Asia and Oceania. The number of DS children with each category of tumor was treated as a Poisson variable with mean equal to 0.000884 times the total number of registrations in that category. Among 8,043 neural cell embryonal tumors (6,882 medulloblastomas and 1,161 CNS-PNETs), only one patient with medulloblastoma had DS, while 7.11 children in total and 6.08 with medulloblastoma were expected to have DS. (p 0.016 and 0.0066 respectively). Among 13,797 children with glioma, 10 had DS, whereas 12.2 were expected. Children with DS appear to be specifically protected against primary neural cell embryonal tumors of the CNS, whereas gliomas occur at the same frequency as in the general population. A similar protection against neuroblastoma, the principal extracranial neural cell embryonal tumor, has been observed in children with DS. Additional genetic material on the supernumerary chromosome 21 may protect against embryonal neural cell tumor development.

“Fitness Fingerprints” Mediate Physiological Culling of Unwanted Neurons in Drosophila

BACKGROUND: The flower gene has been previously linked to the elimination of slow dividing epithelial cells during development in a process known as "cell competition." During cell competition, different isoforms of the Flower protein are displayed at the cell membrane and reveal the reduced fitness of slow proliferating cells, which are therefore recognized, eliminated, and replaced by their normally dividing neighbors. This mechanism acts as a "cell quality" control in proliferating tissues. RESULTS: Here, we use the Drosophila eye as a model to study how unwanted neurons are culled during retina development and find that flower is required and sufficient for the recognition and elimination of supernumerary postmitotic neurons, contained within incomplete ommatidia units. This constitutes the first description of the "Flower Code" functioning as a cell selection mechanism in postmitotic cells and is also the first report of a physiological role for this cell quality control machinery. CONCLUSIONS: Our results show that the "Flower Code" is a general system to reveal cell fitness and that it may play similar roles in creating optimal neural networks in higher organisms. The Flower Code seems to be a more general mechanism for cell monitoring and selection than previously recognized.

How useful is the ultrastructural study of the cilia of the respiratory tract in the diagnosis of an immotile cilia syndrome?

The immotile cilia syndrome (ICS) comprises a range of congenital defects of the ciliary apparatus most probably transmitted by autosomal recessive inheritance. Because cilia occur mainly in the respiratory and genital tract, the clinical symptoms of ICS are most commonly chronic sinusitis, bronchitis, bronchiectasis and male sterility. The syndrome can be associated with a situs inversus and is then called Kartagener's syndrome. We studied the ciliary ultrastructure in airway biopsies of 5 patients suffering from chronic upper and lower respiratory tract infections. With the single exception of one female patient with confirmed ICS diagnosis (Kartagener's syndrome) the etiology of the recurrent infections was unknown. The following ciliary defects were observed: missing dynein arms, radial spoke defects, missing nexin links, microtubular transpositions, compound cilia, supernumerary, absent, or incomplete microtubules, lack of ciliary orientation and various abnormal patterns of microtubular arrangement. In no instance did a patient show only a single anomaly; defects were always combined. Missing dynein arms, radial spoke defects and microtubular transpositions have frequently been described as lesions specific for ICS. Whenever these lesions were found simultaneously in both the respiratory and genital tracts, their genetic origin cannot be doubted. In our confirmed ICS patient the outer dynein arms were not missing but were reduced in number and length in a large number of cilia. The biopsy was, however, obtained from the heavily infected maxillary sinus and it is known that inflammation can lead to a loss of dynein arms. In the light of our investigations and of a review of the published cases of ciliary anomalies, it is concluded that none of the above defects in itself is specific for ICS. They may all occur as secondary lesions or sporadically as varieties in otherwise healthy subjects. It therefore appears questionable whether ICS can be diagnosed from the ciliary ultrastructure of a single airway biopsy. Assessment of ICS cannot be based simply on the ultrastructural demonstration of a particular ciliary defect, but necessitates additional considerations particularly regarding the origin of the biopsy, the sampling procedures and quantitation of defects. It appears necessary to investigate samples from different parts of the airways and quantitatively analyze the prominent lesions.

Tenascin-C is required for normal Wnt/β-catenin signaling in the whisker follicle stem cell niche.

Whisker follicles have multiple stem cell niches, including epidermal stem cells in the bulge as well as neural crest-derived stem cells and mast cell progenitors in the trabecular region. The neural crest-derived stem cells are a pool of melanocyte precursors. Previously, we found that the extracellular matrix glycoproteins tenascin-C and tenascin-W are expressed near CD34-positive cells in the trabecular stem cell niche of mouse whisker follicles. Here, we analyzed whiskers from tenascin-C knockout mice and found intrafollicular adipocytes and supernumerary mast cells. As Wnt/β-catenin signaling promotes melanogenesis and suppresses the differentiation of adipocytes and mast cells, we analyzed β-catenin subcellular localization in the trabecular niche. We found cytoplasmic and nuclear β-catenin in wild-type mice reflecting active Wnt/β-catenin signaling, whereas β-catenin in tenascin-C knockout mice was mostly cell membrane-associated and thus transcriptionally inactive. Furthermore, cells expressing the Wnt/β-catenin target gene cyclin D1 were enriched in the CD34-positive niches of wild-type compared to tenascin-C knockout mice. We then tested the effects of tenascins on this signaling pathway. We found that tenascin-C and tenascin-W can be co-precipitated with Wnt3a. In vitro, substrate bound tenascins promoted β-catenin-mediated transcription in the presence of Wnt3a, presumably due to the sequestration and concentration of Wnt3a near the cell surface. We conclude that the presence of tenascin-C in whiskers assures active Wnt/β-catenin signaling in the niche thereby maintaining the stem cell pool and suppressing aberrant differentiation, while in the knockout mice with reduced Wnt/β-catenin signaling, stem cells from the trabecular niche can differentiate into ectopic adipocytes and mast cells.

Cheek Tooth Extraction Via a Minimally Invasive Transbuccal Approach and Intradental Screw Placement in 54 Equids

OBJECTIVE: To describe (1) preoperative findings and surgical technique, (2) intraoperative difficulties, and (3) postoperative complications and long-term outcome of equine cheek tooth extraction using a minimally invasive transbuccal screw extraction (MITSE) technique. STUDY DESIGN: Retrospective case series. ANIMALS: Fifty-four equids; 50 horses, 3 ponies, and 1 mule. METHODS: Fifty-eight MITSE procedures were performed to extract cheek teeth in 54 equids. Peri- and intraoperative difficulties, as well as short- (<1 month) and long-term (>6 months) postoperative complications were recorded. Followup information was obtained through telephone interviews, making specific inquiries about nasal discharge, facial asymmetry, and findings consistent with surgical site infection. RESULTS: Preoperative findings that prompted exodontia included 50 cheek teeth with apical infections, 48 fractures, 4 neoplasia, 2 displacements, and 1 supernumerary tooth. Previous oral extraction was attempted but had failed in 55/58 (95%) animals because of cheek tooth fracture in 28, or insufficient clinical crown for extraction with forceps in 27. MITSE was successful in removing the entire targeted dental structure in 47/58 (81%) procedures. However, MITSE failed to remove the entire targeted dental structure in 11/58 (19%) procedures and was followed by repulsion in 10/11 (91%). Short-term postoperative complications included bleeding (4/58 procedures, 7%) and transient facial nerve paralysis (4/58 procedures, 7%). Owners were satisfied with the functional and cosmetic outcome for 40/41 (98%) animals with followup. CONCLUSION: MITSE offers an alternate for cheek tooth extraction in equids, where conventional oral extraction is not possible or has failed. Overall, there was low morbidity, which compares favorably with invasive buccotomy or repulsion techniques