Crown Group Research Articles

Cretaceous Antarctic bird skull elucidates early avian ecological diversity.

Fossils representing Cretaceous lineages of crown clade birds (Aves) are exceptionally rare but are crucial to elucidating major ecological shifts across early avian divergences. Among the earliest known putative crown birds is Vegavis iaai1-5, a foot-propelled diver from the latest Cretaceous (69.2-68.4 million years ago)6 of Antarctica with controversial phylogenetic affinities2,7-10. Initially recovered by phylogenetic analyses as a stem anatid (ducks and closely related species)1,2,11, Vegavis has since been recovered as a stem member of Anseriformes (waterfowl)7-9, or outside Aves altogether10. Here we report a new, nearly complete skull of Vegavis that provides new insight into its feeding ecology and exhibits morphologies thatsupport placement among waterfowl within crown-group birds. Vegavis has an avian beak (absence of teeth andreduced maxilla) and brain shape (hyperinflated cerebrum andventrally shifted optic lobes). The temporal fossa is well excavated and expansive, indicating that this bird had hypertrophied jaw musculature. The beak is narrow and pointed, and the mandible lacks retroarticular processes. Together, these features comprise a feeding apparatus unlike that ofany other known anseriform but like that ofother extant birds that capture prey underwater (for example, grebes and loons). The Cretaceous occurrence of Vegavis, with a feeding ecology unique among known Galloanserae (waterfowl and landfowl), is further indication that the earliest anseriform divergences were marked by evolutionary experiments unrepresented in the extant diversity3,11-13.

Oxidative adaptations in prokaryotes imply the oxygenic photosynthesis before the crown group Cyanobacteria

Abstract The metabolic transition from anaerobic to aerobic in prokaryotes reflects adaptations to oxidative stress. Methanogen, one of the earliest life forms on Earth, has evolved into three major groups within the Euryarchaeota, exhibiting different phylogenetic affiliations and metabolic characters. In comparison with other strictly anaerobic methanogenic groups, the Class II methanogens possess better capability to adapt to limited oxygen pressure. Cyanobacteria is considered the first and only prokaryote evolving oxygenic photosynthesis and responsible for the Great Oxidation Event on Earth. However, the connection between oxygenic Cyanobacteria and evolutionary adaptations to oxidative stress in prokaryotes remains elusive. Here, through the SMC (structural maintenance of chromosomes) protein-encoding gene, which was horizontally transferred from the ancient Class II methanogens to the last common ancestor of crown group Cyanobacteria, we demonstrate that the origin of extant Cyanobacteria was undoubtedly posterior to the occurrence of oxygen-tolerant Class II methanogens. In addition, we found that certain prokaryotic lineages had evolved the tolerance mechanisms against oxidative stress before the origin of extant Cyanobacteria. The contradiction that oxidative adaptations in Class II methanogens and other prokaryotes predating crown group oxygenic Cyanobacteria implies the existence of more ancient biological oxygenesis. We propose that these potential oxygenic organisms might represent the extinct phototrophs and first emerge during the Paleoarchean, contributing to the oxidative adaptations in the prokaryotic tree of life and facilitating the dispersal of reaction centers across the bacterial domain.

Feather Evolution Following Flight Loss In Crown Group Birds: Relaxed Selection And Developmental Constraints.

Feathers are complex structures exhibiting structural/functional disparity across species and plumage. Flight was lost in >30 extant lineages from ~79.58 Ma-15 Ka. Effects of flight loss on senses, neuroanatomy, and skeletomusculature are known. To study how flightlessness affects feathers, we measured 11 feather metrics across the plumage of 30 flightless taxa and their phylogenetically closest volant taxa, with broader sampling of primaries across all orders of crown birds. Our sample includes 27 independent flight losses, representing nearly half of extant flightless species. Feather asymmetry measured by barb angle differences between trailing and leading vanes decreases in flightless lineages, most prominently in flight feathers and weakest in contour feathers. Greatest changes in feather anatomy occur in older flightless lineages (penguins, ratites). Comparative methods show some microscopic feather traits are not dramatically modified after flightlessness compared to body mass increase and relative wing and tail fan reduction, but changes toward greater symmetry are stronger. Relaxing selection for flight does not rapidly modify feather flight adaptations, apart from asymmetry. Feathers of recently flightless lineages resemble their volant relatives. Developmental constraints and relaxed selection for novel feather morphologies may explain some observed changes. Macroscopic changes to flight apparati (skeletomusculature, airfoil size) are more evident in recently flightless taxa and could more reliably detect flightlessness in fossils, with increased feather symmetry as a potential microscopic signal. We observed apical modification in later stages of feather development (asymmetric displacement of barb loci), while morphologies arising during early developmental stages are only altered after millions of years of flightlessness.

Tradition and Political Economy in the Viceroyalty of New Spain (18th century)

The legal traditions of the Spanish Empire, which had certain particularities but were always in line with the imperial Catholic culture, played a major role in the development and expansion of the Hispanic world in the Ancien Régime. The converging interests and goals of the Crown, the Church and various groups of individuals were ment to ensure the institutional stability of an immense geoeconomic and cultural space, in which public policies and their implementation were based on the principle of the common good. Throughout the 18th century, beyond the conflicting corporate interests and the great challenges of the time, tradition and reformism influenced one another shaping a political and socioeconomic space, which contributed to strengthening the power and increasing the administrative efficiency of the Hispanic Monarchy. Meanwhile, the two tendencies’ mutual influence boosted the economy in terms of production, finance, trade, and welfare. At the local level, the Hispano-Indian cities and communities had their own administrative and economic resources, and contributed greatly to meeting the financial needs of the Crown, which was often based on negotiation. The Spanish Empire’s fiscal policy and public expenditure, in turn, sought to meet not only defence needs but also those of the government, in addition to promoting Christian education. On balance, the state, the Church and the civil society contributed to the maintenance and development of the Viceroyalty of New Spain.

A timescale for the evolutionary history of sea spiders (Arthropoda: Pycnogonida)

Abstract Sea spiders (Arthropoda: Pycnogonida) are an ancient lineage of chelicerates represented by a single living order, Pantopoda, and a patchy fossil record that provides limited information of their evolutionary timescale. The sudden appearance of Pantopoda in the Middle Jurassic has led several authors to propose a recent (Early Jurassic) origin and rapid diversification of modern pycnogonids. In contrast, a recent molecular clock study suggested Pantopoda originated before the Devonian, and diversified slowly, though the calibrations on which it was based have since been revised. Here, we conduct timetree inference analyses using a set of 13 mitochondrial protein-coding genes, 18S rRNA sequences and 98 Ultra Conserved Elements from 198 pycnogonid taxa, with calibrations reflecting the most recent interpretations of the sea spider fossil record. Our analyses estimate that pycnogonids diverged from other arthropods during the Cambrian (539-510 Ma), indicating about 100 Myr between Pycnogonida origin and pantopod diversification. The pycnogonid crown group (=Pantopoda) diversified during the Late Palaeozoic, in an interval spanning the Early Silurian and the Late Devonian (435-367 Ma), preceding the appearance of the first pantopod fossil by ~206.5 Myr. Our analysis also implies that pantopod families originated between the Late Devonian and the Late Jurassic (378-154 Ma). This leads to very different estimates to previous studies based on the fossil record. However, previous molecular divergence time analyses yielded a similar evolutionary timescale, despite a notably different set of calibrations. This effective corroboration of previous evidence indicates that the underpinning molecular evidence is informative and that the inferred long ghost lineages faithfully reflect the patchy nature of the pycnogonid fossil record which results from their low fossilisation potential. Regardless, our results predict further fossil discoveries from different environments and periods, which might at least partially rewrite pycnogonid history.

Enhanced sensitivity and scalability with a Chip-Tip workflow enables deep single-cell proteomics.

Single-cell proteomics (SCP) promises to revolutionize biomedicine by providing an unparalleled view of the proteome in individual cells. Here, we present a high-sensitivity SCP workflow named Chip-Tip, identifying >5,000 proteins in individual HeLa cells. It also facilitated direct detection of post-translational modifications in single cells, making the need for specific post-translational modification-enrichment unnecessary. Our study demonstrates the feasibility of processing up to 120 label-free SCP samples per day. An optimized tissue dissociation buffer enabled effective single-cell disaggregation of drug-treated cancer cell spheroids, refining overall SCP analysis. Analyzing nondirected human-induced pluripotent stem cell differentiation, we consistently quantified stem cell markers OCT4 and SOX2 in human-induced pluripotent stem cells and lineage markers such as GATA4 (endoderm), HAND1 (mesoderm) and MAP2 (ectoderm) in different embryoid body cells. Our workflow sets a benchmark in SCP for sensitivity and throughput, with broad applications in basic biology and biomedicine for identification of cell type-specific markers and therapeutic targets.

Cranial osteology and neuroanatomy of the late Permian reptile Milleropsis pricei and implications for early reptile evolution.

Millerettidae are a group of superficially lizard-like Permian stem reptiles originally hypothesized as relevant to the ancestry of the reptile crown group, and particularly to lepidosaurs and archosaurs. Since the advent of cladistics, millerettids have typically been considered to be more distant relatives of crown reptiles as the earliest-diverging parareptiles and therefore outside of 'Eureptilia'. Despite this cladistic consensus, some conspicuous features of millerettid anatomy invite reconsideration of their relationships. We provide a detailed description of the late Permian millerettid Milleropsis pricei using synchrotron X-ray phase-contrast micro-computed tomography focusing on the cranial anatomy of three individuals known from a burrow aggregation. Our data reveal a suite of neuroanatomical features Milleropsis shares with neodiapsids that are absent both in other 'parareptiles' and in early diverging groups of 'eureptiles'. Traits shared between Milleropsis and neodiapsids include: the presence of a tympanic emargination on the quadrate, quadratojugal and squamosal, the loss of epipterygoid contribution to the basicranial articulation suggesting a more kinetic palatoquadrate, the absence of a sphenethmoid and the pathway of the abducens nerve through the braincase. Our findings suggest that the early reptile neurocranium, a region poorly sampled in phylogenetic analyses due to relative visual inaccessibility and poor preservation, has the potential to inform the phylogenetic relationships of early reptiles.

Origin of the only myrmecomorphic stink bug, Pentamyrmex spinosus (Hemiptera: Pentatomidae), in the radiation era of ants (Hymenoptera: Formicidae)

AbstractMyrmecomorphy is the most common type of Batesian mimicry in arthropods. In the true bugs (Insecta: Hemiptera: Heteroptera), myrmecomorphy has been recorded in at least seven superfamilies, but not among the stink bugs (Pentatomoidea) until 2014. The only known species that exhibits a high degree of myrmecomorphy during both the adult and nymphal stages within this group, Pentamyrmex spinosus, was reported based on a single specimen, yet little was known beyond its morphological description. In this study, the biology of this species is reported as living in bamboo (Poaceae: Bambusoideae), in close proximity with a highly similar ant species, Polyrhachis dives (Hymenoptera: Formicidae). Further, the phylogenetic position and the origin time of this stink bug species were inferred in the context of Pentatomoidea. The dated phylogeny indicates that Pentamyrmex spinosus is the sister group of Phyllocephalinae, a specialized grass‐feeding subfamily in Pentatomidae, and diverged about 42.7 Ma (52.6–33.2 Ma), roughly synchronous with the radiation of the crown group of Polyrhachis ants (42.0–33.0 Ma) and slightly after the early radiation of bamboos (66.9–24.9 Ma). Our results suggest that the origin of this myrmecomorphic stink bug was probably driven by the rapid diversification of spiny ants and bamboo. In addition, our results also provide a reference framework for the phylogenetic and taxonomic systems of Pentatomoidea and Pentatomidae.

In vivo evaluation of the enamel wear of primary molar against four types of crowns using the intra-oral scanner

BackgroundPrimary tooth wear is a common phenomenon that affects chewing ability, dental sensitivity, aesthetics, and occlusion. This study was conducted to compare the antagonistic enamel wear of primary molars opposed to four different crown materials.MethodsForty lower second primary molars of children aged 4–8 years were allocated into 4 groups: Group 1 (n = 10): received stainless steel crowns; Group 2 (n = 10): received prefabricated commercially available zirconia crowns (NuSmile®); Group 3 (n = 10): received locally manufactured zirconia crowns created via the CAD/CAM system; and Group 4 (n = 10): received locally manufactured hybrid ceramic (Vita Enamic®) crowns created via the CAD/CAM system. All the crowns were cemented with resin-modified glass ionomer cement. The upper arch was scanned with a 3D intraoral scanner immediately (baseline), 6 months, and 1 year after crown cementation to evaluate the wear of the natural enamel of the antagonistic primary molar. The resultant scans were compared via Exocad software to measure the amount of linear wear of the mesiopalatal cusp of the primary upper second molar.ResultsThe analysed data revealed statistically significant differences between the studied groups. The highest mean wear was detected in the CAD/CAM zirconia crown group, followed by the NuSmile zirconia crown group and then the CAD/CAM hybrid crown group, and the lowest mean wear was detected for the stainless-steel crown group.ConclusionCompared with stainless steel crowns, aesthetic crowns cause more wear in the antagonistic primary molar enamel. CAD/CAM zirconia crowns induce the greatest amount of wear, followed by NuSmile zirconia crowns. The CAD/CAM hybrid crown is an aesthetic tooth-coloured crown that causes less wear of the opposing enamel than zirconia crowns do.Trial registrationThe ClinicalTrials.gov Protocol Registration and Results System (PRS) has this RCT registered as (NCT06456879) on 07/06/2024.

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.

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.

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.

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.

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.

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.