Dental microwear of a basal ankylosaurine dinosaur, Jinyunpelta and its implication on evolution of chewing mechanism in ankylosaurs

Jinyunpelta sinensis is a basal ankylosaurine dinosaur excavated from the mid Cretaceous Liangtoutang Formation of Jinyun County, Zhejiang Province, China. In the present study, its dental microwear was observed using a confocal laser microscope. Jinyunpelta had steep wear facets that covered most of buccal surfaces of posterior dentary teeth. Observation of dental microwear on the wear facet revealed that scratch orientation varied according to its location within the wear facet: vertically (i.e. apicobasally) oriented scratches were dominant in the upper half of the wear facet, and horizontally (i.e. mesiolaterally) oriented ones were in the bottom of the facet. These findings indicated that Jinyunpelta adopted precise tooth occlusion and biphasal jaw movement (orthal closure and palinal lower jaw movement). The biphasal jaw movement was widely observed among nodosaurids, among ankylosaurids, it was previously only known from the Late Cretaceous North American taxa, and not known among Asian ankylosaurids. The finding of biphasal jaw movement in Jinyunpelta showed sophisticate feeding adaptations emerged among ankylosaurids much earlier (during Albian or Cenomanian) than previously thought (during Campanian). The Evolution of the biphasal jaw mechanism that contemporaneously occurred among two lineages of ankylosaurs, ankylosaurids and nodosaurids, showed high evolutionary plasticity of ankylosaur jaw mechanics.

Influence of the Method in Root Canal Filling Using Active Lateral Compaction Techniques

The aim of this study was to evaluate, by stereomicroscopy and confocal laser microscopy, the influence of different lateral compaction methods for the obturation quality, as well as the time spent for the procedure. Thirty root canals of freshly extracted single-rooted human teeth were prepared with the ProTaper system up to F5 instrument and filled with gutta-percha and AH Plus sealer by the lateral compaction technique. The teeth were divided into 3 groups (n=10) in accordance with the method used for the lateral compaction, as follows: Manual, Mechanical and Ultrasonic. The sealers were stained with rhodamine B dye in a proportion of 0.1% per gram in weight to allow for the analysis under a confocal microscope. During the root filling procedure, the time spent was recorded with a stopwatch. The specimens were stored at 37 °C for 48 h, and then sectioned at 2, 4 and 6 mm from the apex. The percentage of gutta-percha, sealer and void areas were evaluated using a stereomicroscope and sealer penetration perimeter by confocal laser microscope. Statistical analyses were performed using the Kruskall-Wallis and Dunn tests (p<0.05). The mechanical method required a shorter time for the lateral compaction than the manual method (p<0.05). There were no significant differences (p>0.05) for the perimeter of the dentin with sealer penetration among all groups. The mechanical method showed a higher (p<0.05) percentage of gutta-percha and less sealer at the 4 mm section in comparison with the manual method. The ultrasonic group showed intermediate values. The void areas found in the root filling were similar (p>0.05) between the three methods. In conclusion, the fastest lateral compaction was achieved with the mechanical method, and all the methods showed void areas in the root filling.