Curvature-dependent shear bond strength of different attachment materials for orthodontic lingual indirect bonding

To evaluate the shear bond strength (SBS) of different attachment materials used for lingual bonding, the influence of artificial aging and the radii of curvature of the enamel surface on SBS, 192 third molars were photographed to determine the radius of curvature of the oral surface. After phosphoric acid etching a cylindrical test piece was bonded to the oral enamel using a mold that was filled with a chemically curing (Maximum Cure, Transbond IDB Premix) or a dual-curing (Nexus NX3, RelyX Unicem2) attachment material. SBS was tested after 24 h, 500 thermal cycles or 90 days at 37 °C with a universal testing machine. Computed tomography scans were performed to determine the bonded surface and calculate SBS. Values ranged from 8.3 to 20.9 MPa. RelyX Unicem2 showed the highest SBS values at baseline, 500 thermal cycles and after 90 days (p < 0.001). Ninety days of wet storage significantly reduced SBS of Maximum Cure (p = 0.028). The radius of curvature correlated positively with SBS (rs = 0.204, p = 0.005). The SBS of all attachment materials was sufficient for clinical use, even after artificial aging. RelyX Unicem2 showed almost twice as high SBS values as the other attachment materials.

Octopus arms exhibit exceptional flexibility

The octopus arm is often referred to as one of the most flexible limbs in nature, yet this assumption requires detailed inspection given that this has not been measured comprehensively for all portions of each arm. We investigated the diversity of arm deformations in Octopus bimaculoides with a frame-by-frame observational analysis of laboratory video footage in which animals were challenged with different tasks. Diverse movements in these hydrostatic arms are produced by some combination of four basic deformations: bending (orally, aborally; inward, outward), torsion (clockwise, counter-clockwise), elongation, and shortening. More than 16,500 arm deformations were observed in 120 min of video. Results showed that all eight arms were capable of all four types of deformation along their lengths and in all directions. Arms function primarily to bring the sucker-lined oral surface in contact with target surfaces. Bending was the most common deformation observed, although the proximal third of the arms performed relatively less bending and more shortening and elongation as compared with other arm regions. These findings demonstrate the exceptional flexibility of the octopus arm and provide a basis for investigating motor control of the entire arm, which may aid the future development of soft robotics.

FORMATION OF THE GINGIVAL RECESSION IN PATIENTS WITH BRUXISM

Subject. Despite the data on the polyetiology of gum recession, the role of some factors in its formation remains unknown, which does not allow to adequately develop methods for the prevention of this disease. The aim of this study was to assess the effect of bruxism on the formation of gingival margin recession. Methodology. The study was based on data, obtained during the examination of 65 patients aged 20 to 40 years with a of bruxism, established by a neurologist. The control group consisted of 65 conditionally healthy patients of the same age without neurological pathology and with intact periodontal disease. The study excluded individuals with other etiological factors that can lead to gingival recession. Result. According to the results of the study, a 1 year later, the occurrence of gingival recession was determined in 44.7 % of cases, after 2 years, the number of recessions was determined in 64.7 %, and after 36 months in 77 % of cases. At the same time, the periodontal condition in relation to the formation of recessions remained unchanged in the patients of the comparison group. In all cases, recession was determined by the oral surface of the lower incisors, in 80 % of patients, on the vestibular surface of the canines and bicuspid of both jaws. Conclusions: In patients with bruxism, there is a gradual formation of gingival recession with a predominant localization in the area of the oral surface of the incisors in the lower jaw, and on the vestibular surface of the canines and the buccal surface of the bicuspid.

New rhenopyrgid edrioasteroids (Echinodermata) and their implications for taxonomy, functional morphology, and paleoecology

Rhenopyrgids are rare, turreted edrioasterid edrioasteroids from the lower Paleozoic with a distinctive and apparently conservative morphology. However, new, well-preserved rhenopyrgid edrioasteroid material from Canada, along with a review of described taxa, has revealed broader structural diversity in the oral surface and enabled a re-evaluation of rhenopyrgid functional morphology and paleoecology.The floor plates in Rhenopyrgus viviani n. sp., R. coronaeformis Rievers, 1961 and, R. flos Klug et al., 2008 are well fused to each other and the interradial oral plate and lack obvious sutures, thereby forming a single compound interradial plate. This differs from other rhenopyrgids where sutures are more apparent. Such fused oral surface construction is only otherwise seen in some derived edrioblastoids and in the cyathocystids, suggesting homoplasy.Our analysis further suggests that the suboral constriction could contract but the flexible pyrgate zone could not. Thus, specimens apparently lacking a sub-oral constriction should not necessarily be placed in separate genera within the Rhenopyrgidae. It also supports rhenopyrgids as epifaunal mud-stickers with only the bulbous, textured, entire holdfasts (coriaceous sacs) anchored within the substrate rather than as burrow dwellers or encrusters.Rhenopyrgus viviani n. sp. is described from the Telychian (lower Silurian) Jupiter Formation of Anticosti Island, Québec, Canada and is differentiated by a high degree of morphological variability of pedunculate plates, broader oral plates, and narrower distal ambulacral zones. Specimens lacking or with obscured diagnostic plates from the Ordovician of Montagne Noire, France, and the Ordovician and Silurian of Girvan, Scotland are also described.UUID: http://zoobank.org/7f81d67f-4155-4719-8a45-b278ad70739d

A new species of Astropecten (Echinodermata: Asteroidea: Paxillosida: Astropectinidae) and a comparison of the Astropecten species from the Gulf of Mexico and the East Florida Shelf

A new species of Astropecten is described, supported by morphological and molecular evidence, from the Gulf of Mexico and the East Florida Shelf with most specimens from 30–60 m in depth. The new species, A. mcedwardi n. sp., is small, with a maximum major radius < 30 mm. Specimens of A. mcedwardi n. sp. have been found in five museums as an undescribed species or misidentified under several names. The spination of the oral surface most closely resembles that of Astropecten antillensis Lütken, 1859 from the Caribbean, but the body form is similar to that of Astropecten duplicatus Gray, 1840, which is found in the same geographic range. Examination of specimens from different collections indicates that the new species may overlap in distribution with A. antillensis along the East Florida Shelf. Sequencing and phylogenetic analysis of two mitochondrial genes reveal that A. mcedwardi is closely related to A. antillensis but that its phylogenetic lineage is distinct from that of A. antillensis.

A new species of Fibularia from Japanese waters with a redescription of F. japonica and F. ovulum (Echinodermata: Echinoidea: Clypeasteroida)

A new species, Fibularia coffea sp. nov., occurs from shallow waters in Japan. This new species is distinguished from the other species of Fibularia by the following characters: test height is low, oral surface is slightly depressed toward the peristome, number of pores of petal III continues to increase with the test growth, reaching over 30 at TL > 7.5 mm, and black pigments form symmetric pentaradial on aboral surface in living animals. Two further Japanese species, Fibularia japonica and F. ovulum, are redescribed based on the type specimens (F. japonica) and additional specimens (F. ovulum), respectively. A tabular key to the extant species of Fibularia is also provided. A partial fragment of the mitochondrial gene cytochrome oxidase subunit I (COI) of the type specimens of F. coffea sp. nov. and the additional specimen of F. japonica was sequenced for barcoding in future works.

Eggs for breakfast? Analysis of a probable mosasaur biting trace on the Cretaceous echinoid <i>Echinocorys ovata</i> Leske, 1778

Fossil biting traces (praedichnia) represent indirect evidence of predation and shed light on fossil predator–prey interactions and fossil food webs. Especially from echinoderm skeletons, biting traces are well known. Here, we describe the oral surface of a large Cretaceous (Maastrichtian) holasteroid echinoid Echinocorys ovata Leske, 1778 from Hemmoor (northern Germany) which exhibits four circular punctures arranged in a semi-circular arc. Whereas three of the punctures penetrated the skeleton, one puncture only just hit the margin of the echinoid test at the ambitus, leaving a long incision furrow in the skeleton. The punctures were not lethal to the sea urchin as is indicated by progressed skeletal regeneration and closure of the fractures. The overall appearance of the punctures suggests that they were produced during a single mechanical event, most likely by the biting action of the teeth of a large vertebrate animal. We analysed the shape and arrangement of the biting trace and conclude that it was probably produced by a marine reptile possessing a prognath tooth position, most likely by a globidensine mosasauroid. Our finding not only sheds light on mosasaur feeding behaviour and prey selection but also increases the knowledge of the food webs in the chalk sea ecosystem during the uppermost Cretaceous.