Tooth Pattern Research Articles

An inductive signalling network regulates mammalian tooth morphogenesis with implications for tooth regeneration

Sequential and reciprocal epithelial-mesenchymal interactions, essential throughout such aspects of tooth morphogenesis as patterning, size and number of teeth, involves a well-ordered series of inductive and permissive signals that exert global control over cell proliferation, differentiation and organogenesis. In particular, growth factors, transcription factors and their corresponding receptors, as well as other soluble morphogens, make up a regulatory network at the molecular level that synergistically or antagonistically controls intra-/inter-cellular signal transduction during odontogenesis. This review summarizes recent advances in the study of crucial signalling pathways, for example of BMPs, Wnt, Notch, Shh and FGF, with emphasis on the potential integrated signalling network responsible for tooth formation. Our work probes into the complexity of these inductive signalling pathways to promote the understanding of tooth regeneration. Additionally, our study provides further insights into therapeutic strategies for various dental abnormalities in patterning and number, such as tooth agenesis and supernumerary teeth.

Fracture Strength and Fracture Patterns of Root-filled Teeth Restored With Direct Resin Composite Restorations Under Static and Fatigue Loading

To assess fracture strength and fracture patterns of root-filled teeth with direct resin composite restorations under static and fatigue loading. MOD cavities plus endodontic access were prepared in 48 premolars. Teeth were root filled and divided into three restorative groups, as follows 1) resin composite; 2) glass ionomer cement (GIC) core and resin composite; and 3) open laminate technique with GIC and resin composite. Teeth were loaded in a servohydraulic material test system. Eight samples in each group were subjected to stepped fatigue loading: a preconditioning load of 100 N (5000 cycles) followed by 30,000 cycles each at 200 N and higher loads in 50-N increments until fracture. Noncycled teeth were subjected to a ramped load. Fracture load, number of cycles, and fracture patterns were recorded. Data were analyzed using two-way analysis of variance and Bonferroni tests. Fatigue cycling reduced fracture strength significantly (p<0.001). Teeth restored with a GIC core and a laminate technique were significantly weaker than the composite group (379±56 N, 352±67 N vs 490±78 N, p=0.001). Initial debonding occurred before the tooth underwent fracture. All failures were predominantly adhesive, with subcrestal fracture of the buccal cusp. Resin composite restorations had significantly higher fracture strength than did other restorations. Fatigue cycled teeth failed at lower load than did noncycled teeth.

Disturbance of respiratory muscle control in a patient with early-stage multiple sclerosis

To the Editor: Respiratory dysfunction from multiple sclerosis (MS) is most commonly of insidious onset and related to progressive respiratory muscle weakness [1]. Disorders of respiratory muscle coordination are poorly recognised and challenging to diagnose. We present a case of a patient with MS and no clear muscle weakness whose dyspnoea was associated with a disorder of respiratory muscle control. The potential utility of oesophageal manometry for diagnosis of unexplained dyspnoea is highlighted. A 54-year-old female with relapsing-remitting MS presented with 2 weeks of dyspnoea and orthopnoea. She was ambulatory with a low extended disability score of 1.5. 6 months earlier she started cyclophosphamide for disease progression recognised by magnetic resonance imaging (MRI). A week after her last infusion she developed severe dyspnoea and orthopnoea. She had no other symptoms. Her vital signs were normal. Her laboratory tests and arterial blood gas were unremarkable. Chest computed tomography showed no pulmonary parenchymal disease. Echocardiography was unremarkable. Pulmonary function testing (PFTs) demonstrated severe restriction, with a 14% lower vital capacity in the supine position. Her dyspnoea and PFTs improved over the following 1–2 months, but she did not return to her baseline level of pulmonary function. Electromyography (EMG) with phrenic nerve conduction studies demonstrated no abnormalities. MRI was prohibited by her orthopnoea. Previously, MRI demonstrated extensive demyelination in the brain and brainstem that was asymptomatic. Oesophageal manometry was performed to exclude the possibility of bilateral diaphragmatic dysfunction and to elucidate her unexplained dyspnoea. A balloon-catheter was inserted via the nose to position the balloon in the distal oesophagus to estimate pleural pressure. Repeated attempts to perform a forced vital capacity manoeuvre consistently demonstrated fluctuating exhalations, as evidenced by the saw tooth pattern of the flow volume curve (fig. …

A phase II study of intermittent sunitinib (S) in previously untreated patients (pts) with metastatic renal cell carcinoma (mRCC).

4515 Background: S as initial treatment in mRCC is limited by balancing acute and chronic toxicity with clinical benefit. Pre-clinical and retrospective clinical data support that extended treatment breaks are feasible without a reduction in efficacy. Methods: Pts with treatment-naïve clear cell mRCC were enrolled on a prospective phase II trial and initially treated with 4 cycles of S (50 mg 4/2). Pts with ≥ 10% reduction in tumor burden (TB) following 4 cycles had S held, with CT scans approximately every 10 weeks. S was re-initiated for 2 cycles in those pts with an increase in TB by ≥ 10% and again held with ≥ 10% TB reduction. This intermittent S dosing continued until RECIST-defined disease progression while on S. The primary objective was feasibility of intermittent S, defined as the proportion of eligible pts who underwent intermittent therapy. The alternative hypothesis was a feasibility of &gt; 80% vs. a null hypothesis of &lt; 50% (a=0.05; power 80%). Results: Thirty-six pts were enrolled; 70% male, median age 60, 95% PS 0/1 and 32% favorable/65% intermediate by Heng criteria. Twenty pts were eligible for intermittent therapy and all pts (100%) entered the intermittent phase. Pts were not eligible for intermittent S due to PD (n=13); toxicity (n=1) or w/d of consent (n=2) prior to end of cycle #4. Sixteen pts (80%) had ≥ 10% TB increase off S with a median (range) increase of 1.5 cm (1.1-2.5) compared to the TB immediately prior to stopping S, considering all off periods.Four pts did not have ≥ 10% TB increase off S (3 pts after the 1st off period; off for 12, 8 and 5 months to date and 1 pt after the 2nd off period; off for 8 months prior to restarting S). Most pts exhibited a stable saw tooth pattern of TB reduction on S and TB increase off S. No pt had RECIST-defined PD while on S, but 2 pts were taken off extended breaks due to gradual TB increase over time, and 1 pt developed new CNS mets during the 2nd off period.The objective response rate was 53%. Toxicity was typical for S and completely resolved during treatment breaks. Conclusions: S dosing with periodic extended time off drug is feasible and associated with reduction in toxicity during the off periods. Clinical efficacy does not appear to be compromised. Clinical trial information: NCT01158222.

Morphology and chronology of diphyodont dentition in miniature pigs, Sus Scrofa

There is little knowledge about the tooth replacement in large mammals. The aim of this study is to investigate the tooth replacement patterns in Chinese miniature pig (Sus Scrofa). The developmental patterns of mandibular successional and additional teeth from Chinese miniature pig before and after birth were investigated by microanatomy, immunohistochemistry, and cone beam computed tomography. Secondary dental lamina for successional teeth was not visible until its predecessor progressed to late bell stage. Successional teeth reached early cap stage when their predecessor began to erupt. The development patterns and speed varied between anterior and posterior successional teeth. Additional molars, derived from the free end of additional dental lamina, initiated sequentially in mandible ramus, while previous additional molar progressed into late bell stage. Proliferating cells in the permanent primordium were distributed asymmetrically. Our findings identify the characteristic patterns about spatiotemporal morphogenesis of successional teeth in context of their predecessor and cascade initiation of additional molars in miniature pigs. Our study provides a basis toward better understanding the mechanisms underlying diphyodont replacement in human and also assists in tooth regeneration and tooth engineering in large animal.

Developmental Processes, Evolvability, and Dental Diversification of New World Monkeys

The developmental processes that contribute to variation of morphological traits are the subject of considerable interest when attempting to understand phenotypic evolution. It is well demonstrated that most characteristics of tooth pattern can be modified by tinkering conserved signal pathways involved in dental development. This effect can be evaluated by comparing developmental models with naturally occurring variation within explicit phylogenetic contexts. Here, we assess whether evolutionary changes in lower molar (M) ratios among platyrrhines were channelled by alterations in the balance of activators and inhibitors as predicted by the inhibitory cascade (IC) model (Kavanagh et al. in Nature 449:427–432, 2007). Ordinary linear regression adjusted to M2/M1 versus M3/M1 ratios of 38 species of platyrrhines indicated that the slope and intercept were significantly different from the IC model. Conversely, when the phylogeny was incorporated into the regression analyses (PGLS), variation in molar ratios did not differ from the developmental model. PGLS also showed that changes in molar proportions are not an allometric effect associated with body size. Discrepancies between phylogenetically corrected and non-corrected analyses are mainly due to the departure of Callitrichines from the predicted values. This subfamily displays agenesis of M3 with higher than expected M2/M1 ratios, indicating that M3 fails to develop even when the inhibition by M1 on the subsequent molars is not increased. Our results show that evolution in molar ratios is concordant with slight changes in the proportion of activators and inhibitors that regulate molar development; however, other processes are required to account for variation in the number of teeth.

Fracture patterns of glass–ionomer cement overlays versus stainless steel bands during endodontic treatment: an ex‐vivo study

To compare fracture patterns of posterior teeth temporized with: mesio-occlusal-distal (MOD) glass-ionomer cement (GIC) interim restorations, stainless steel (SS) bands, GIC dome overlays and GIC dome overlays with occlusal temporary restorations. The root canals of 92 extracted human premolars and molars were prepared with rotary NiTi instruments and dressed with calcium hydroxide paste prior to cavity preparation for standardized MOD restorations. Teeth were divided into four groups (n = 23) and temporarily restored with: GIC interim restorations (GIC group), stainless steel bands (SS group), GIC dome overlays (GIC-O group) or GIC dome overlays with intermediate restorative material (IRM) in the access cavities (GIC-IRM group). Teeth were subjected to compressive axial load until fracture; fracture forces and fracture modes were recorded. Statistical analysis included Kaplan-Meier plots, Cox proportional hazards model, one-way analysis of variance, chi-square and Fisher's exact tests. There was a significantly higher risk of failure in the GIC group compared with the SS (P < 0.001), GIC-O (P < 0.001) and GIC-IRM (P = 0.001) groups. The mean fracture force for SS was significantly higher than GIC-O (P = 0.03) and GIC-IRM (P < 0.001). GIC fracture force was significantly lower than all other groups (P < 0.001). Significantly fewer unfavourable fractures were observed in SS compared with GIC (P = 0.001), GIC-O (P = 0.007) and GIC-IRM (P < 0.001). Glass-ionomer cement dome overlays with reduced cuspal height and occlusal inclines may be recommended for broken-down posterior teeth, without any risk of poor aesthetics, gingival irritation or further proximal tooth structure loss. Stainless steel bands may only need to be used in extensively broken-down teeth or in the presence of parafunctional habits.

Dental anomalies in a Portuguese population

The aim of this study was to evaluate the prevalence and pattern of agenesis, supernumerary teeth, impacted teeth and transpositions, as well as the relation between them, in a Portuguese sample. The study sample consisted of 2888 patients, observed between 2005 and 2009 at the Dentistry Clinic of the Instituto Superior de Ciências da Saúde-Norte (ISCSN, Portugal). The study included evaluation of the following parameters: agenesis of all teeth, supernumerary teeth, impacted permanent teeth and tooth transposition. The age range varied from 7 to 21 years. In order to study the absence of the third molar, subjects aged below 14 years were excluded. Statistical analysis was performed using SPSS(®). Excluding third molars, the prevalence of tooth agenesis, supernumerary teeth, impacted teeth and transpositions was 6.1%, 0.8%, 1.8% and 0.2%, respectively, for this Portuguese population. There was a significantly higher prevalence of supernumerary teeth in males than in females (P < 0.05). The mesiodens was the most frequent supernumerary tooth, the upper canine was the most frequent impacted tooth, and the upper canine and upper lateral were the two most frequently transposed teeth. There was a significantly higher prevalence of missing third molars in the impacted canine group than in the non-impacted canine group (P < 0.05). Agenesis is the most frequent dental anomaly. There are no differences between genders, except for supernumerary teeth, which are found more frequently in men. A relation between third molar agenesis and impacted canines was found.

Pipestoneomyidae, a new family of fossil rodents (Mammalia) from the Duchesnean (late middle Eocene, Bartonian) to Orellan (early Oligocene, Priabonian) of North America

Additional specimens of the problematical rodent Pipestoneomys Donahoe, 1956, have allowed for recognition of a new family, Pipestoneomyidae. A new genus and species of pipestoneomyid is recognized from the late middle Eocene (Duchesnean North American Land Mammal Age; Bartonian), Argorheomys septendrionalis, which is morphologically more primitive than Pipestoneomys and demonstrates that this new family has been distinct since the Duchesnean. The Pipestoneomyidae share a number of derived characters with the Geomorpha, especially the two-part inner layer of incisor enamel of the Eoymidae. The Pipestoneomyidae differ from the Eomyidae in lacking the basic “omega” pattern of the cheek teeth of the former, so are in the Eomyoidea as a distinct family.

Mid-Cretaceous Cretoxyrhina (Elasmobranchii) from Mangyshlak, Kazakhstan and Texas, USA

SIVERSON, M., WARD, D.J., LINDGREN, J. & KELLEY, L.S., iFirst article. Mid-Cretaceous Cretoxyrhina (Elasmobranchii) from Mangyshlak, Kazakhstan and Texas, USA. Alcheringa, 1–18. ISSN 0311-5518. The holotype of the nominal lamniform shark ‘Pseudoisurus’ vraconensis comprises an isolated tooth from a late Albian stratum at Besakty, Mangyshlak, Kazakhstan. Its stratigraphical provenance indicates that it is of Mortoniceras perinflatum Zone-age or somewhat older. It is indistinguishable at the species level from isolated teeth from the Mortoniceras rostratum Zone of the Pawpaw Shale in northeast Texas. Abundant teeth of ‘P’. vraconensis-type from slightly younger strata close to the Albian–Cenomanian boundary at Kolbay, eastern Mangyshlak, Kazakhstan, enabled the reconstruction of a dentition adhering to the dental blueprint of Cretoxyrhina, clarifying the generic identity of ‘P’. vraconensis. In the Kolbay population, the distal lobe of the root on the three probable third upper anterior teeth at hand is not labiolingually compressed relative to the mesial lobe. Labiolingual flattening of the root lobe facing the mesial side of the intermediate bar is a characteristic feature of modern lamnids and may reflect limited accommodation space for a thick root lobe to form at the distal margin of the anterior hollow. An intermediate bar adds structural strength to the anterior part of the palatoquadrate while isolating the upper anterior teeth, facilitating deep penetration by their enlarged cusps. Individuals of Cretoxyrhina from the late Coniacian to earliest Campanian Smoky Hill Chalk in Kansas display a strongly disjunct heterodonty in the anterior half of the upper jaw dentition. This so-called ‘lamnoid tooth pattern’ is regarded by some researchers as a synapomorphy of the Lamniformes. The dwarfed teeth creating the ‘lamnoid tooth pattern’ in Smoky Hill Chalk individuals are seemingly matched by relatively larger, corresponding teeth in the 15 million years older C. vraconensis. The probable weakening of the disjunct upper jaw heterodonty in Cretoxyrhina with increasing geological age indicates that the ‘lamnoid tooth pattern’ might have evolved independently in two or more lamniform clades.

A new acaremyid rodent (Hystricognathi: Octodontoidea) from the middle Miocene of Patagonia (South America) and considerations on the early evolution of Octodontoidea.

Octodontoidea is the most speciose and ecologically diverse superfamily of caviomorph rodents. The systematic relationships of modern octodontoids is moderately accepted, however, the relationships of fossils (from the Eocene?-middle Miocene) are not clear. In recent years the hypothesis of a complex early evolution of the superfamily has emerged, with "basal octodontoids" representing different evolutionary lineages. The extinct family Acaremyidae may represent one such lineage, consisting of the genera Acaremys, Sciamys, Galileomys, and variably Platypittamys. In this work we describe a new octodontoid rodent recorded in post-Colloncuran? levels exposed at the locality of El Petiso, Northwest of Chubut Province, Argentina. Based on a systematic analysis of dental characters, we conclude that the new specimens correspond to a new species of Sciamys. Additionally, if the post-Colloncuran age for El Petiso is verified, the new species will extend the temporal range of the family Acaremyidae until, at least, the late middle Miocene, as well as the temporal range for the genus Sciamys from the Santacrucian SALMA. Our phylogenetic analyses corroborate the position of the new species as a member of Sciamys, and confirm that Acaremyidae represents an extinct family from Patagonian South America that lived until the middle Miocene. Massoiamys obliquus qualifies as morphological ancestor that pre-announces the octodontiform tooth pattern of octodontids. Thus, the octodontiform tooth pattern appears at least twice within the superfamily Octodontoidea.

Tooth agenesis patterns in unilateral cleft lip and palate in humans

ObjectiveTo characterize tooth agenesis patterns and their overall prevalence in patients with complete unilateral cleft lip and palate (CUCLP). DesignPanoramic radiographs of 115 non-syndromic patients (78 males and 37 females) with CUCLP (85 patients had a cleft on the left and 30 on the right) from the Cleft Palate Craniofacial Unit in Nijmegen (The Netherlands) were evaluated. Third molars were not included in the evaluation. The Tooth Agenesis Code (TAC) was used to identify tooth agenesis patterns. ResultsAgenesis of at least one tooth was found in 48.7%, and agenesis outside the cleft was observed in 20.9% of patients. The lateral incisor of the maxillary cleft quadrant was the tooth most frequently missing (39.1%), followed by the maxillary lateral incisor (8.7%), and the mandibular second premolar (7.8%) in the non-cleft quadrants. Thirteen different tooth agenesis patterns were identified. Maxillary and/or maxillary and mandibular second and/or first premolars were involved in all patterns. ConclusionA higher prevalence of tooth agenesis is observed in patients with CUCLP, even outside the cleft region, compared with the general population. Thirteen different patterns were observed, of which 6 were unique patterns. Certain teeth were involved in all agenesis patterns. Both the prevalence of orofacial clefting as well as hypodontia is more frequently observed on the left side.

Tooth implant supported Prosthesis: A Literature review

Background: Implants are connected to the natural teeth in the management of partially edentulous patients. The use of this concept has been a subject of discussion as some authors have recommended it while others stress on the potential complications associated with splinting implants to natural teeth. Purpose: The purpose of this article was to systematically review the literature regarding the rationale, difference in the biomechanical behavior of the implant and the natural teeth, nature of connection, potential complications associated with splinting of implants and teeth, and guidelines to be followed. Materials and Methods: Various databases like PubMed, Ebscohost, Science Direct were searched between 1980 to December 2011 to retrieve articles regarding the implant natural teeth connection. A manual search for the references from the retrieved articles was also completed. The articles published only in English, randomized clinical trials, prospective and retrospective clinical studies, laboratory and computer generated research were included. Abstracts, opinion articles, technique articles and questionnaire based studies were excluded. Results: The biomechanical impact of mismatch in the mobility pattern of natural teeth and implants has been controversial. Various complications associated with tooth implant supported prosthesis has been reported with intrusion and implant overloading being the cause of concern. Marginal bone loss associated with overload around the implant has been reported and found to be within acceptable levels. The reports also suggested no significant differences between various types of connections utilized and to use the non rigid connections with caution. Conclusion: Whenever possible implant supported prostheses should be the treatment of choice. However, certain clinical situations demand connecting teeth to implants. Clinical Relevance to Interdisciplinary Dentistry The difference in the biomechanical behaviour between osseointegrated implants and teeth and the efficacy of the different modes of connection that have been employed are explored. Evidence based decisions could be made concerning utility of connecting teeth to implants

Adaptive evolution of the lower jaw dentition in Mexican tetra (Astyanax mexicanus)

BackgroundThe Mexican tetra (Astyanax mexicanus) has emerged as a good animal model to study the constructive and regressive changes associated with living in cave environments, as both the ancestral sighted morph and the cave dwelling morph are extant. The cave dwelling morphs lack eyes and body pigmentation, but have well developed oral and sensory systems that are essential for survival in dark environments. The cave forms and surface forms are interfertile and give rise to F1 hybrids progeny known as intermediates. In cavefish, degeneration of the lens is one of the key events leading to eye regression. We have previously shown that surgical lens removal in surface fish embryos has an effect on the craniofacial skeleton. Surprisingly, lens removal was also found to have an effect on the caudal teeth in the lower jaw. In order to understand this result, we analyzed the lower jaw and upper jaw dentitions of surface, cavefish and F1 hybrids of surface and cavefish and compared our findings with surface fish that underwent lens removal. We also investigated the upper jaw (premaxillae and maxillae) dentition in these fish.ResultsOur tooth analyses shows that cavefish have the highest numbers of teeth in the mandible and maxillae, surface forms have the lowest numbers and F1 hybrids are between these groups. These differences are not observed in the premaxillae. A wide diversity of cuspal morphology can also be found in these fish. Jaw size also differs amongst the groups, with the mandible exhibiting the greatest differences. Interestingly, tooth number in surgery fish is different only in the caudal region of the mandible; this is the region that is constrained in size in all morphs.ConclusionOur data provides the first detailed description of the jaw dentitions of two morphs of Astyanax mexicanus, as well as in F1 hybrids. Tooth number, patterning and cuspal morphology are enhanced in cavefish in all jaws. This is in contrast to the increase in tooth number previously observed on the lens ablated side of the surgery fish. These findings indicate that the mechanisms which govern the constructive traits in cavefish are different to the mechanisms causing an increase tooth number in surgery fish.

Tooth-implant connection: A critical review

Background: Controversy regarding tooth-implant connection in implant dentistry has emerged due to the differences in the mobility pattern of tooth and implant causing increased stress on the implant leading to implant failure.Purpose: The purpose of this review is to critically analyze the technical complications, the biological impact of tooth-implant connection and the treatment modalities that may be helpful in preventing intrusion. Materials and Methods: A detailed search was carried out in the dental literature available in English language from 1989 to 2012 which included review articles and case reports. The search was carried out in PubMed database, Google search engine, Medline and Science Direct as well as manual search of peer reviewed literature using relevant key words. Results: Literature search revealed studies involving complications and biomechanical interactions of tooth-implant connection and the survival rates of tooth-implant supported fixed prosthesis (TISP). Conclusion: Thus tooth-implant connection has its own advantages, disadvantages, risks and complications, but what justifies its application is the risk-benefit evaluation with a special attention on patient requirements. Thus many longitudinal studies are necessary before this method is declared as the treatment of choice.

Analysis of moment structures for assessing relationships among perceived chewing ability, dentition status, muscle strength, and balance in community‐dwelling older adults

The aim of this study was to assess relationships among perceived chewing ability, dentition status, muscle strength and balance in community-dwelling older adults using analysis of moment structures (Amos). Physical performance parameters such as muscle strength and balance can predict the future onset of disabilities in activities of daily living among older adults. In this context, elucidation of the relationships among oral conditions and physical performance parameters is necessary. Data on occlusal contact patterns of natural teeth (OPNT), self-assessed masticatory ability (mastication), body mass index (BMI), handgrip strength (HG) and one-leg standing time with eyes open (OLST) were collected from 501 independently living adults aged 65-74 years. The relationships among these parameters were analysed using Spearman's rank correlation coefficients and Amos. Subjects of both genders showed significant correlations among OPNT, mastication, HG and OLST, evaluated using Spearman's rank correlation coefficients. For each Amos model, the goodness-of-fit statistic indicated a good level of fit. In both men and women, OPNT was significantly related to mastication, and mastication was related to HG but not to OLST. OPNT was related to neither HG nor OLST in women and was related to OLST but not HG in men. The findings observed in this study present a possible importance of dental status and perceived chewing ability for the onset of disability by influencing physical performance in community-dwelling older adults.

Residence time distributions of in-line high shear mixers with ultrafine teeth

The large eddy simulation and combined species transport method was validated for the residence time distribution (RTD) predictions of the pilot-scale in-line high shear mixers (HSMs) with ultrafine teeth. RTD characteristics were experimentally and numerically investigated under different rotor speeds and flowrates for the in-line HSM with double rows of inclined stator teeth. The exponential decays of the RTD curves indicate that the in-line HSM generally behaves like a mixed flow reactor, where the mixedness increases under higher rotor speeds and flowrates. It is indicated that the RTDs are greatly dependent on the HSM configurations, such as the shear gap widths, tip-to-base clearances, rows of the rotor and stator teeth, as well as patterns of the stator teeth. Defects of channeling, short circuiting and fluid re-entrainment are resulted from inefficient in-line HSM designs, such as those with large shear gap widths, large tip-to-base clearances, single rows of rotor and stator teeth, or improper angles of stator teeth. It is suggested that the in-line HSM with double rows of inclined stator teeth, narrow shear gap width and tip-to-base clearance has the advantage to provide intensified mass transport efficiency in the view of exploring novel chemical reactors.

Dental morphology of the Lesser Bamboo Rat, Cannomys badius (Rodentia, Spalacidae).

Cannomys and Rhizomys are the sole living genera of the tribe Rhizomyini (Rhizomyinae, Spalacidae, Rodentia), known in the fossil record since the Late Miocene. The dental morphology of fossil Rhizomyini has been described in detail but until recently such descriptions were unavailable for extant species. A detailed account of the morphology and dental wear pattern of the cheek teeth of Cannomys badius is provided here based on the examination of museum specimens. Three stages of wear are recognized. Cannomys shares with Rhizomys the synapomorphy of having a mesolophid that is a long continuation of the protoconid on the first lower molar. There are significant differences between these taxa, such as the much smaller size of the cheek teeth and the trilophodont dental pattern of the M2, M3, and m2 in Cannomys.

Duplicated zebrafish co-orthologs of parathyroid hormone-related peptide (PTHrP, Pthlh) play different roles in craniofacial skeletogenesis

In mammals, parathyroid hormone-related peptide (PTHrP, alias PTH-like hormone (Pthlh)) acts as a paracrine hormone that regulates the patterning of cartilage, bone, teeth, pancreas, and thymus. Beyond mammals, however, little is known about the molecular genetic mechanisms by which Pthlh regulates early development. To evaluate conserved pathways of craniofacial skeletogenesis, we isolated two Pthlh co-orthologs from the zebrafish (Danio rerio) and investigated their structural, phylogenetic, and syntenic relationships, expression, and function. Results showed that pthlh duplicates originated in the teleost genome duplication. Zebrafish pthlha and pthlhb were maternally expressed and showed overlapping and distinct zygotic expression patterns during skeletal development that mirrored mammalian expression domains. To explore the regulation of duplicated pthlh genes, we studied their expression patterns in mutants and found that both sox9a and sox9b are upstream of pthlha in arch and fin bud cartilages, but only sox9b is upstream of pthlha in the pancreas. Morpholino antisense knockdown showed that pthlha regulates both sox9a and sox9b in the pharyngeal arches but not in the brain or otic vesicles and that pthlhb does not regulate either sox9 gene, which is likely related to its highly degraded nuclear localization signal. Knockdown of pthlha but not pthlhb caused runx2b overexpression in craniofacial cartilages and premature bone mineralization. We conclude that in normal cartilage development, sox9 upregulates pthlh, which downregulates runx2, and that the duplicated nature of all three of these genes in zebrafish creates a network of regulation by different co-orthologs in different tissues.

The impact of a tooth pattern of a synchronous tachogenerator on spectral components of an output EMF

The finite elements method is used to calculate the output EMF curve of a synchronous tachogenerator. A rotor tooth pattern was optimized in order to significantly decrease the level of higher harmonics in the output EMF of a tachogenerator.