Crown Group Research Articles

Thermomechanical aging effects on vertical marginal gap and fracture resistance: a comparative study of Bioflx and traditional pediatric crowns

BackgroundVarious types of crowns are used for full-coverage restoration of primary teeth affected by caries, developmental defects, or after pulp therapy. Prefabricated Stainless Steel and Zirconia crowns are commonly utilized. Bioflx crowns, which blend the properties of Stainless Steel and Zirconia, provide a flexible and aesthetically pleasing alternative.AimThis study aimed to evaluate the vertical marginal gap and fracture resistance of Bioflx pediatric crowns compared to Zirconia and Stainless Steel crowns following thermomechanical aging.MethodsThis in-vitro study was conducted using mandibular second primary crowns of three different materials (n = 30). Crowns were divided into three groups; Zirconia crowns group (n = 10, Nu Smile, USA), Bioflx crowns group (n = 10, Nu Smile, USA) and Stainless Steel crowns group (n = 10, Nu Smile, USA). The crowns were cemented onto standardized acrylic resin dies and subjected to thermomechanical aging. Vertical marginal gap measurements were obtained using a USB digital microscope with an integrated camera, while fracture resistance was assessed with a universal testing machine. Data were analyzed for outliers and tested for normality using the Shapiro-Wilk or Kolmogorov-Smirnov tests, with statistical significance set at 0.05.ResultsSignificant differences were observed in the vertical marginal gaps among the groups after cementation and thermomechanical aging (P = 0.013 and P = 0.001, respectively). Zirconia crowns exhibited the largest average marginal gap, followed by Bioflx and Stainless Steel crowns. Stainless steel crowns demonstrated the highest fracture resistance, followed by Bioflx crowns, while Zirconia crowns showed the lowest.ConclusionsBioflx crowns exhibit the largest vertical marginal gap but show greater fracture resistance compared to Zirconia crowns, although they are still less resistant than Stainless Steel crowns after undergoing thermomechanical aging.

Omnidens appendages and the origin of radiodont mouthparts

AbstractThe sophisticated, modular and adaptable body plan of arthropods underpins their dominance in marine invertebrate communities. The origin of this body plan from legged lobopodian worms can be inferred from Cambrian Konservat‐Lagerstätten, but our understanding retains some notable gaps: not least in the transition from swimming lobopodians such as Kerygmachela and Pambdelurion to robustly sclerotized radiodonts such as Anomalocaris. A large Pambdelurion‐like fossil from the Xiaoshiba biota, Omnidens qiongqii sp. nov., exhibits a novel combination of characters: an oral apparatus with a non‐radial configuration; and centimetric talon‐like grasping structures with heavily sclerotized blade‐like spines. The novel morphology broadens the interpretative framework for associated Cambrian taxa, demonstrating continuity in the morphology of euarthropod appendages prior to the origin of podomeres. A reappraisal of the euarthropod stem lineage suggests that radially arranged mouthparts may be a radiodont novelty, rather than an inheritance from the ancestral ecdysozoan. These results further resolve the evolutionary origins of the euarthropod body plan.

Russulaceae of the Pakaraima Mountains of Guyana 5. Two newly described diminutive species in a novel lineage of the crown clade of Russula (Russulaceae)

Much of our previous work documenting fungal biodiversity in Guyana has been centered in forests of Dicymbe corymbosa Spruce ex Benth., which forms monodominant stands in the white sands region of Guyana. In order to begin to assess fungal biodiversity associated with other ectomycorrhizal host trees found in Guyana, expeditions were conducted to areas containing Dicymbe altsonii and Pakaraimaea dipterocarpacea. In this paper, we describe two new species of Russula from Guyana with diminutive basidiomata: R. lilliputia and R. pakaraimaeae, found in association with these tree hosts, using a combined approach of morphological characterization and molecular analyses. Together with R. gelatinivelata, which we previously described from Guyana, R. lilliputia and R. pakaraimaeae form what appears to be a new lineage within the crown clade of Russula, sister to the subsect. Auratinae. Synapomorphies for the lineage include a pruinose to subtomentose pileus in dry conditions, suprapellis comprised of inflated cells that give rise to long cylindrical or digitate, and sinuous, thin or thick-walled pileocystidia that are strongly emergent, easily disarticulate in microscopic preparations, and have contents that are acid resistant in Basic Fuchsin, pruinose to subomentose patches on the stipe, suprahilar plage on the basidiospores, spore ornamentation of mostly isolated verrucae, and geographic distribution restricted to the Pakaraima Mountains of Guyana. Full descriptions, photos, line drawings of microscopic features, and comparisons with related species are provided.

Evaluation of Wear on Primary Tooth Enamel and Fracture Resistance of Esthetic Pediatric Crowns Manufactured from Different Materials

Background and Objectives: Advances in dental materials and CAD-CAM technology have expanded crown options in primary teeth due to their improved appearance and mechanical properties. Thus, this study aimed to assess the enamel wear and fracture resistance of prefabricated, milled, and 3D-printed esthetic pediatric crowns. Materials and Methods: The study involved 60 extracted maxillary second primary molars and 60 3D-printed resin dies, divided into six groups based on different crown materials (n = 10): prefabricated zirconia, prefabricated composite, milled composite, milled resin matrix ceramic, milled PEEK, and 3D-printed resin. Prefabricated crowns were selected after the preparation of the typodont mandibular second primary molar tooth, while milled and 3D-printed crowns were custom produced. The specimens underwent mechanical loading of 50 N at 1.6 Hz for 250,000 cycles with simultaneous thermal cycling. The 3D and 2D wear amounts were evaluated by scanning the specimens before and after aging. Then, the fracture resistance and failure types of the restorations were recorded. Results: The results showed that the milled PEEK group had superior fracture resistance compared to the other groups, while prefabricated zirconia crown group had the lowest value. Milled resin matrix ceramic crown group displayed the lowest 3D wear volume, while 3D-printed crown group showed the highest 2D wear. Conclusions: The restorative material type did not have a significant effect on the wear of primary tooth enamel. The fracture resistance of the tested materials differed according to the material type. Although the milled PEEK group showed the highest fracture resistance, all tested materials can withstand chewing forces in children.

A Molecular Temporal Evolutionary Framework of Land Plants and the Age of Angiosperms

A series of Bayesian molecular clock analyses with varying model combinations, parameters, and tree topologies were conducted to establish a temporal evolutionary framework of land plants and to estimate the age of angiosperms. The data consisted of five organellar and nuclear genes, 633 taxa, and 23 fossil calibration points (FCPs). The analyses were evaluated using an internal search thoroughness measure, effective sample sizes, and two external criteria: the consensus land plant phylogeny and a newly developed method that used the Hennigian reciprocal illumination principle to compare molecular age estimates of 21 nodes representing major land plant clades and the root split in green plants with those of their fossils in an a posteriori fashion. The results show that an analysis using a general time reversible (GTR) DNA substitution model, log normal branch-rate distribution, and Yule tree prior represented the best model combination, with the Birth-Death tree prior being equally optimal. This analysis estimated the age of the land plant crown group as 496.95 million years (MY), with a 95% highest posterior density (HPD) of 465.66–531.43 MY, and the age of the angiosperm crown group as 219.93 MY, with a 95% HPD of 184.09–256.82 MY. The former agrees with the fossil evidence, but the latter is significantly older than the fossil ages. A thorough examination of fossil evidence of angiosperms, as well as their evolutionary history in light of recent knowledge of morphology, physiology, and atmospheric CO2 concentration in the Mesozoic era, suggests that angiosperm radiation might have been delayed after their origin and that the current fossil record probably reflects only the products of that radiation, not the origin of angiosperms. Overall, the study shows that both molecular clock analyses and fossil studies, while agreeing on some aspects but disagreeing on others, can help develop a complete understanding of the temporal evolutionary history of land plants.

Multi-gene analysis of the Russula crown clade (Russulales, Basidiomycota) revealed six new species and Alboflavinae subsect. nov. from Fagaceae forests in China.

The crown clade is one of two major groups in the Russula subg. Russula. An analysis of Chinese samples was performed based on the morphology, internal transcribed spacer (ITS) sequences, and multi-gene phylogenies of 28S nrLSU, 16S mtSSU, rpb1, rpb2, and tef1-α. The results supported the independence of six new species: Russula alboflava (sect. Amethystinae), R. chrysantha (subsect. Chamaeleontinae), R. liyui (subsect. Laricinae), R. lutescens (subsect. Olivaceinae), R. paraxerampelina, and R. prunicolor (subsect. Xerampelinae) from Fagaceae forest habitats. Subsect. Alboflavinae was newly proposed in sect. Amethystinae. Members of the new subsection include R. alboflava, R. burlinghamiae, and possibly R. ballouii. Our analyses also supported the claim that two species of R. fulvograminea (subsect. Laricinae) and R. subrubens (subsect. Xerampelinae) have a Eurasian distribution. The habitat and primary hosts of the main phylogenetic clades within related subsections were summarized and discussed.

In-vitro comparison of fracture resistance of CAD/CAM porcelain restorations for endodontically treated molars

BackgroundThis study evaluates the fracture strength and patterns of feldspathic porcelain restorations made using CAD/CAM technology for lower first molars with extensive crown destruction. The restorations include post-core and full-contour crown, composite resin core and full-contour crown, and endocrown. This research provides insights into effective restorative options to address tooth fracture risk, supporting minimally invasive procedures and CAD/CAM integration in dental practices.MethodsThis study utilized 80 permanent mandibular first molars, which were divided into four groups: Group I (Post-Core-Full-contour crown), Group II (Core- Full-contour crown), Group III (Endocrown), and Group IV (Control). Root canal treatment was performed on all samples except for the control group. Following access cavity preparation, restorations for each tooth were fabricated using the CAD/CAM system and cemented with resin cement. The specimens were embedded in acrylic blocks. After undergoing thermomechanical aging, the samples were subjected to fracture resistance testing using a universal testing machine, which applied force until fracture occurred. The fracture patterns were subsequently analyzed, and the data were statistically evaluated using the Kruskal-Wallis and Chi-Square tests (p < 0.05).ResultsA significant difference in fracture values under axial forces was observed (p < 0.05). The control group had the highest fracture strength (1830 ± 277 N), while the Core- full-contour crown group showed the lowest (1532 ± 371 N). Failure types varied significantly among the groups (χ2 = 26.886, df = 9, p = 0.001). The most common failure type was Type-2 (33.75%), characterized by restorable fractures, while Type-3 fractures, unrestorable, were the least common (12.5%).ConclusionsThe findings underscore the significance of technological advancements in CAD/CAM for effectively restoring endodontically treated teeth with extensive crown damage. This study contributes valuable insights, emphasizing the clinical relevance of selecting appropriate restorative options to mitigate the risk of tooth fracture associated with coronal restoration failures.

Deep-time origin of tympanic hearing in crown reptiles.

The invasion of terrestrial ecosystems by tetrapods (c. 375 million years [Ma]) represents one of the major evolutionary transitions in the history of life on Earth. The success of tetrapods on land is linked to evolutionary novelties. Among these, the evolution of a tympanic ear contributed to mitigating the problem of an impedance mismatch between the air and the fluid embedding sound-detecting hair cells in the inner ear.1,2,3 Pioneering studies advocated that similarities in the tympanic ear of tetrapods could only result from a single origin of this structure in the group,4,5 an idea later challenged by paleontological and developmental data.4,6,7,8 Current evidence suggests that this sensory structure evolved independently in amphibians, mammals, and reptiles,1,6 but it remains uncertain how many times tympanic hearing originated in crown reptiles.9,10 We combine developmental information with paleontological data to evaluate the evolution of the tympanic ear in reptiles from two complementary perspectives. Phylogenetically informed ancestral reconstruction analyses of a taxonomically broad sample of early reptiles point to the presence of a tympanic membrane as the ancestral condition of the crown group. Consistently, comparative analyses using embryos of lizards and crocodylians reveal similarities, including the formation of the tympanic membrane within the second pharyngeal arch, which has been previously reported for birds. Therefore, both our developmental and paleontological data suggest a single origin for the tympanic middle ear in the group, challenging the current paradigm of multiple acquisitions of tympanic hearing in living reptiles.

Seating Accuracy of Prefabricated Interim Crowns on Immediate and Delayed Implants: A Laboratory Study.

Evaluation of seating accuracy of interim crowns for the immediate restoration of immediate implants (I-Imp) and delayed implants (D-Imp) placed via static computer-assisted implant surgery (sCAIS). A maxillary training model was modified by removing the central incisors and simulating fresh extraction socket in one site and healed ridge on the other site. An I-Imp was planned in the extraction socket and D-Imp was planned in the healed site. The planned implants were used to design sCAIS surgical template and interim crowns for immediate restoration of the implants. Fourteen surgical models received sCAIS implants after which the interim crowns were inserted. Subsequently, the models with the seated crowns were scanned by a laboratory scanner. The planning virtual model was superimposed against every surgical model to measure vertical, horizontal and proximal contact errors of each crown. All the crowns were positioned more incisally than the planned crowns. This was significantly more noticeable for the D-Imp crowns (0.81 mm) than the I-Imp crowns (0.55 mm). The 2 crown groups had similar horizontal errors (I-Imp &#61;0.35 mm, D-Imp &#61; 0.36 mm). The D-Imp crowns had minimal proximal contact error (0.14 mm), but the I-Imp crowns had significantly greater proximal contact error (0.74 mm) in the form of open distal contacts. This pattern of error appears related to the relationship between the socket morphology and the planned implant position. Prefabricated interim I-Imp crowns suffered from greater errors that affected the proximal contact quality than DImp crowns. The observed deviation of the I-Imp crowns can be attributed to the socket morphology and its relation to the planned implant position. The deviations of the I-Imp crowns are clinically significant and will require clinical adjustments. Thus, caution is needed before routine use of prefabricated interim crowns on I-Imp.

From the inside out: Were the cuticular Pseudonocardia bacteria of fungus-farming ants originally domesticated as gut symbionts?

The mutualistic interaction specificity between attine ants and antibiotic-producing Actinobacteria has been controversial because Pseudonocardia strains cannot always be isolated from worker cuticles across attine ant species, while other actinobacteria can apparently replace Pseudonocardia and also inhibit growth of Escovopsis mycopathogens. Here we report that across field samples of Panamanian species: (i) Cuticular Pseudonocardia were largely restricted to species in the crown of the attine phylogeny and their appearance likely coincided with the first attines colonizing Central/North America. (ii) The phylogenetically basal attines almost always had cuticular associations with other Actinobacteria than Pseudonocardia. (iii) The sub-cuticular glands nourishing cuticular bacteria appear to be homologous throughout the phylogeny, consistent with an ancient general attine-Actinobacteria association. (iv) The basal attine species investigated always had Pseudonocardia as gut symbionts while Pseudonocardia presence appeared mutually exclusive between cuticular and gut microbiomes. (v) Gut-associated Pseudonocardia were phylogenetically ancestral while cuticular symbionts formed a derived crown group within the Pseudonocardia phylogeny. We further show that laboratory colonies often secondarily acquire cuticular Actinobacteria that they do not associate with in the field, suggesting that many previous studies were uninformative for questions of co-adaptation in the wild. An exhaustive literature survey showed that published studies concur with our present results, provided that they analyzed field colonies and that Actinobacteria were specifically isolated from worker cuticles shortly after field collection. Our results offer several testable hypotheses for a better overall understanding of attine-Pseudonocardia interaction dynamics and putative coevolution throughout the Americas.

Neural crest precursors from the skin are the primary source of directly reprogrammed neurons

Direct reprogramming involves the conversion of differentiated cell types without returning to an earlier developmental state. Here, we explore how heterogeneity in developmental lineage and maturity of the starting cell population contributes to direct reprogramming using the conversion of murine fibroblasts into neurons. Our hypothesis is that a single lineage of cells contributes to most reprogramming and that a rare elite precursor with intrinsic bias is the source of reprogrammed neurons. We find that nearly all reprogrammed neurons are derived from the neural crest (NC) lineage. Moreover, when rare proliferating NC precursors are selectively ablated, there is a large reduction in the number of reprogrammed neurons. Previous interpretations of this paradigm are that it demonstrates a cell fate conversion across embryonic germ layers (mesoderm to ectoderm). Our interpretation is that this is actually directed differentiation of a neural lineage stem cell in the skin that has intrinsic bias to produce neuronal progeny.

Vertebrate paleontology of the Cloverly Formation (Lower Cretaceous), IV: the oldest edentulous frog (Salientia) from Laurasia

ABSTRACT Edentulism—lack of teeth—is a derived condition among salientians (total-group frogs and toads) that has arisen independently at least 22 times within the crown group, Anura. Despite this frequency, edentulism (in part or complete) is seldom documented in the salientian fossil record, and thus its evolutionary history remains obscure. A ∼90 Ma gap presently exists between the edentulous salientians Notobatrachus reigi (late Toarcian; Argentina) and the five known species from the latest Cretaceous of Argentina, South Africa, Canada, and the U.S.A. Here we report a new instance of edentulism in an Early Cretaceous salientian, Ostrombatrachos nodos gen. et sp. nov., based on a maxilla from an early Albian age (∼ 111 Ma) locality in the Cloverly Formation of Wyoming, U.S.A. Although incomplete, the holotype maxilla exhibits a distinctive suite of features (i.e., edentulous; pit-and-ridge external ornament; shallow groove across anteriormost portion of margo orbitalis and continuing anteroventrally down lateral surface of pars facialis to interrupt the external ornament; medially expanded orbital flange; moderately broad, deep lamina horizontalis; and weakly developed processus pterygoideus) that is unknown in any other salientian. This new taxon represents the oldest occurrence of edentulous maxillae in a Laurasian salientian and helps fill the long temporal gap in edentulism among salientians. O. nodos gen. et sp. nov. does not appear to be closely related to other edentulous Mesozoic salientians, suggesting it represents yet another independent evolution of this feature.

Phylogeny, historical biogeography and climate niche differentiation in extant species of Ceratophryidae (Anura, Hyloidea) frogs in South America

Ceratophryidae is a family of frogs containing twelve extant species distributed in South America. Several studies have been carried out concerning the systematics, morphology, karyotypes, and behaviour within this monophyletic family. However, little is known about the historical biogeography and the divergence in time of this group. Here, we present an updated phylogeny, along with a calibrated chronogram, to analyse the historical biogeographical pattern and climate niche differentiation among extant species of Ceratophryidae (Anura: Hyloidea) frogs in South America. A phylogeny based on morphological and genetic data was obtained from 256 morphological characters, six mitochondrial and eight nuclear genes for up to a total of 8428 characters in the homological matrix. Our results indicate that the genus Ceratophrys is sister to the clade Chacophrys + Lepidobatrachus. The divergence of the crown group of Ceratophryidae is estimated to have occurred 19.2 Ma at the beginning of the Miocene, with recent cladogenetic events related to the late Miocene (10.18–13.70 Ma) and the Pliocene (~5.3–2.6 Ma). Moreover, the Cerrado region is estimated to be the ancestral area of the family, as well for the genera Chacophrys and Lepidobatrachus. In addition, temperature seasonality and annual precipitation play a major role in the niche differentiation of extant species within Ceratophryidae. In conclusion, our data suggest multiple dispersal and vicariance events originating from the Cerrado region in the early Miocene, and recognize the role of the environment in the differentiation of the ecological niches among extant species of this family in South America. Ceratophryidae is hypothesized to have originated in the semi-arid Cerrado region in the early Miocene (~19.2 million years ago), from where species have diversified by independent dispersal and vicariance events across other South American regions. Ceratophrys frogs are phylogenetically recovered as the sister taxon to the clade comprising Chacophrys and Lepidobatrachus. Three lineages of Lepidobatrachus and four lineages from Ceratophrys diverged in the Pliocene, around 5.3 to 2.6 million years ago. Niche differentiation among extant species of Ceratophryidae appears to reflect roles for temperature seasonality and annual precipitation.

A chromosome phased diploid genome assembly of African hunting dog (Lycaon pictus).

The African hunting dog (Lycaon pictus, 2n=78) once ranged over most sub-Saharan ecosystems except its deserts and rainforests. However as a result of (still ongoing) population declines, today they remain only as small fragmented populations. Furthermore, the future of the species remains unclear, due to both anthropogenic pressure as well as interactions with domestic dogs, thus their preservation is a conservation priority. On the tree of life, the hunting dog is basal to Canis and Cuon and forms a crown group with them, making it a useful species for comparative genomic studies. Here, we present a diploid chromosome level assembly of an African hunting dog. Assembled according to VGP guidelines from a combination of PacBio HiFi reads and HiC data, it is phased at the level of individual chromosomes. The maternal (pseudo)haplotype (mat) of our assembly has a length of 2.38 Gbp, and 99.36 % of the sequence is encompassed by 39 chromosomal scaffolds. The rest is included in only 36 unplaced short scaffolds. At the contig level, mat consists of only 166 contigs with an N50 of 39 Mbp. BUSCO analysis showed 95.4 % completeness based on Сarnivora conservative genes (carnivora_odb10). When compared to other available genomes from subtribe Canina, the quality of the assembly is excellent, typically between the 1st and 3rd depending on the parameter used, and a significant improvement on previously published genomes for the species. We hope this assembly will play an important role in future conservation efforts and comparative studies of canid genomes.

Cell type and cell signaling innovations underlying mammalian pregnancy.

The fetal-maternal interface is one of the most intense loci of cell-cell signaling in the human body. Invasion of cells from the fetal placenta into the uterus, and the corresponding transformation of maternal tissues called decidualization, first evolved in the stem lineage of eutherian mammals( 1 , 2 ). Single-cell studies of the human fetal-maternal interface have provided new insight into the cell type diversity and cell-cell interactions governing this chimeric organ( 3-5 ). However, the fetal-maternal interface is also one of the most rapidly evolving, and hence most diverse, characters among mammals( 6 ), and an evolutionary analysis is missing. Here, we present and compare single-cell data from the fetal-maternal interface of species bracketing key events in mammal phylogeny: a marsupial (opossum, Monodelphis domestica ), the afrotherian Tenrec ecaudatus, and four Euarchontoglires - guinea pig and mouse (Rodentia) together with recent macaque and human data (primates) ( 4 , 5 , 7 ). We infer cell type homologies, identify a gene-expression signature of eutherian invasive trophoblast conserved over 99 million years, and discover a predecidual cell in the tenrec which suggests stepwise evolution of the decidual stromal cell. We reconstruct ancestral cell signaling networks, revealing the integration of fetal cell types into the interface. Finally, we test two long-standing theoretical predictions, the disambiguation hypothesis( 8 ) and escalation hypothesis( 9 ), at transcriptome-wide scale, finding divergence between fetal and maternal signaling repertoires but arms race dynamics restricted to a small subset of ligand-receptor pairs. In so doing, we trace the co-evolutionary history of cell types and their signaling across mammalian viviparity.

Phylogenetic and morphological evidence for four new species of Russula (Russulaceae, Basidiomycota) from northwestern China

Four novel species of subgenus Russula crown clade collected from northwestern China are described based on morphological and phylogenetic evidence. Morphologically, R. griseorosea Y.Song sp. nov. (subsection Puellarinae) is characterized by its brown pileus with a grayish pink tint, basidiospores with warts often connected by fine lines, orthochromatic pileipellis with long terminal cells and septate pileocystidia; R. micangshanensis Y.Song sp. nov. (subsection Olivaceinae) is diagnosed by its large basidia, hymenial cystidia and basidiospores, and spore ornamentations with unequal crests and often twinned warts, which give the spore distinctive appearance; R. minirosea Y.Song sp. nov. (subsection Laricinae) has very small basidiocarp with pileus less than 3.3 cm in diameter, basidiospores with fine reticulum, small basidia, and septate pileocystidia; R. purpureomarginalis F.Li &amp; Y.Song sp. nov. (subsection Xerampelinae) has large basidiospores with often isolated ornamentations, slim basidia and often septate flexuous pileocystidia. Differences between the four novel species and their closely related taxa were analyzed. Phylogenetic analyses based on both ITS and multi-locus (LSU, rpb2 and tef1) were carried out to confirm the distinct taxonomic status of the four novel species.

Alterations of pleiotropic neuropeptide-receptor gene couples in Cetacea

BackgroundHabitat transitions have considerable consequences in organism homeostasis, as they require the adjustment of several concurrent physiological compartments to maintain stability and adapt to a changing environment. Within the range of molecules with a crucial role in the regulation of different physiological processes, neuropeptides are key agents. Here, we examined the coding status of several neuropeptides and their receptors with pleiotropic activity in Cetacea.ResultsAnalysis of 202 mammalian genomes, including 41 species of Cetacea, exposed an intricate mutational landscape compatible with gene sequence modification and loss. Specifically for Cetacea, in the 12 genes analysed we have determined patterns of loss ranging from species-specific disruptive mutations (e.g. neuropeptide FF-amide peptide precursor; NPFF) to complete erosion of the gene across the cetacean stem lineage (e.g. somatostatin receptor 4; SSTR4).ConclusionsImpairment of some of these neuromodulators may have contributed to the unique energetic metabolism, circadian rhythmicity and diving response displayed by this group of iconic mammals.

Cumulative effect of digital manufacturing techniques, preparation taper and finish line designs on the retention of aged temporary molar crowns − An in vitro study

ObjectiveThis study evaluated the effects of finish-line design, tooth preparation taper or total occlusal convergence (TOC), and digital production technology on the retention of provisional crowns for molars. Material and MethodsDifferent taper angles (10° TOC and 20° TOC) and finish line designs (chamfer and shoulder) were used to prepare four mandibular first molar teeth. Two subgroups of the prepared teeth received temporary crowns that were either “Computer-Aided Design” and “Computer-Aided Manufacturing (CAD/CAM) milled or 3D printed. Hence, eight test groups of temporary crowns containing 10 samples each were created. Groups 1–4 were milled, and Groups 5–8 were 3D printed specimens. A consistent procedure was used to cement 80 temporary crowns. The specimens were thermocycled for a total of 5000 heat cycles, initially at 5 °C for 30 s (dwell time) and then at 55 °C for 30 s. The pull-off force necessary to remove the temporary crowns was recorded, and the tensile strength, which served as the dependent variable, was calculated. Analysis of variance (ANOVA) was used to assess the variations in retention forces among the test groups. ResultsThe mean tensile strengths at maximum load [MPa] were higher in Groups 5, 6, 7, 8 (6.6 MPa, 6.91 MPa, 7.65 MPa, and 7.45 MPa respectively) as compared to the mean tensile strengths at maximum load [MPa] in Groups 1, 2, 3, 4 (2.35 MPa, 3.52 MPa, 3.21 MPa, and 2.45 MPa respectively). ConclusionFor extended periods, 3D-printed crowns with steeper preparation tapers (20° TOC) and shoulder finish lines exhibited enhanced retention.

The Palaeobiology of Two Crown Group Cnidarians: Haootia quadriformis and Mamsetia manunis gen. et sp. nov. from the Ediacaran of Newfoundland, Canada.

The Ediacaran of eastern Newfoundland preserves the world's oldest known eumetazoan body fossils, as well as the earliest known record of fossilized muscular tissue. Re-examination of the holotype of the eight-armed Haootia quadriformis in terms of its morphology, the arrangement of its muscle filament bundles, and hitherto undescribed aspects of its anatomy support its interpretation as a crown staurozoan. We also document several new fossils preserving muscle tissue with a different muscular architecture to Haootia, but with only four arms. This new material allows us to describe a new crown group staurozoan, Mamsetia manunis gen. et sp. nov. This work confirms the presence of crown group medusozoan cnidarians of the Staurozoa in the Ediacaran of Newfoundland circa 565 Ma.

The mammary hair of Monodelphis domestica and homology of the mammary pilosebacous unit.

The unitary mammary gland is a synapomorphy of therian mammals and is thought to have evolved from the pilosebaceous organ in the mammalian stem lineage from which the lactogenic patch of monotremes is also derived. One of the key lines of evidence for the homology of the nipple and the lactogenic patch is that marsupials have retained a transient hair associated with developing mammary glands. However, these structures have not been documented since the early 20th-century drawings of Ernst Bresslau. In this study, we examine the developing mammary organs of Monodelphis domestica and document the presence of mammary hairs in 12-week-old females, as well as their absence after 18 weeks of age. Histochemical staining for cystine confirms the structures as keratinized hairs. Milk ducts of both juvenile and adult nipples show a division between KRT18+ luminal epithelium and KRT14+ ACTA2+ myoepithelium. These patterns match those in eutherians and suggest a conserved ductal morphology and mechanism of milk expulsion. Finally, PTHLH, a peptide hormone which promotes homeotic transformation of hairy skin into hairless nipples in the mouse, was detected in the Monodelphis milk duct during the mammary hair stage, suggesting that the mutual exclusivity of "hairless nipple" and "hair" organ identity is derived in eutherian mammals. These results reveal shared characteristics of the M. domestica nipple with both the eutherian nipple and the pilosebaceous organ, consistent with the evolutionary derivation of the mammary gland from an ancestral hair organ via developmental individualization of pilosebaceous and mammary identities.