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Jurassic to Lower Cretaceous samples from the Sverdrup Basin, Arctic Canada, contain abundant and well preserved dinoflagellate cysts. The stratigraphic interval studied comprises the Savik Formation - Jaeger Formation complex, the Awingak Formation - Ringnes Formation deltaic complex and the Deer Bay Formation - Mould Bay Formation deltaic complex; it is characterized by dominantly elastic sedimentation. Seventeen dinoflagellate cyst Oppel-zones are recognized within the Lower Jurassic to Lower Cretaceous interval. The ages suggested by the assemblages of dinoflagellate cysts generally agree with those based on invertebrates and range from Toarcian or older to Late Valanginian or younger. Sixty genera and 129 species of dinoflagellate cysts have been identified. Eighteen new species are described: Apteodinium bucculiatum, ?Comparodinium cavum, Dapcodinium coalitum, Dapcodinium holotabulatum, ?Egmontodinium diminutum, Escharisphaeridia rudis, Glomodinium opeasatos, Glomodinium zabros, Hystrichodinium lanceatum, lithodinia serrulata, Millioudodinium jubaris, Occisucysta thulia, Parvulodinium penitabulatum, Sentusidinium cuculliformis, Sentusidinium filiatum, Tanyosphaeridium magneticum, Tectatodinium laminatum and Trichodinium erinaceoides

This ex-vivo study compared the static frictional resistance of three self-ligating brackets with a conventional steel-ligated Ultratrimm bracket. The effects of archwire size (0.020, 0.019 x 0.025 and 0.021 x 0.025-inch), bracket/archwire angulation (0, 5 and 10 degrees) and the presence of unstimulated human saliva were investigated. The study demonstrated that both increases in wire size and bracket/archwire angulation resulted in increased static frictional resistance for all bracket types tested, with the presence of saliva having an inconsistent effect. Mobil-Lock Variable-Slot had the least friction for all wires for 0 degree angulation. However, with the introduction of angulation, the values were comparable to those of the other brackets. Activa brackets had the second lowest frictional resistance, although high values were found with 0.019 x 0.025-inch wires. SPEED brackets demonstrated low forces with round wires, although with rectangular wires or in the presence of angulation, friction was greatly increased. Ultratrimm brackets produced large individual variation, confirming the difficulty in standardizing ligation force, although under certain conditions, significantly larger frictional forces were observed. In conclusion, self-ligating brackets showed reduced frictional resistance in comparison to steel ligated brackets only under certain conditions.

Recent demonstrations of the superficial nature and ease of removal of root-surface-associated cytotoxic materials suggest that extensive root-surface instrumentation is not warranted clinically. This in vitro investigation determined the detoxifying effects of a conservative regime of ultrasonic root debridement, using the Limulus amoebocyte lysate assay for lipopolysaccharide (LPS) as an indication of the presence or absence of cytotoxic materials. 20 extracted periodontally-involved single-rooted teeth, with no clinically detectable calculus deposits, were debrided with a Cavitron TF-10 tip. Light pressure, resulting from a force application of approximately 50 g, lasting for 0.8 s/mm2 of root surface was used and complete overlapping instrumentation ensured. The finding of LPS levels of less than 2.5 ng per root in 19 out of 20 teeth after such debridement was comparable to LPS levels found on healthy, uninvolved control teeth, and thus endorses the growing belief that root surface cleanliness can be readily achieved.

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