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At least 145 records · Page 8Linked to original sources
PubMed1975

The effect of preparation procedures on original canal shape and on apical foramen shape.

With the use of clear casting resin, simulated curved canals were created so that canal preparation procedures could be directly visualized and compared. Regardless of the type of enlarging instrument or the technique used, undesirable characteristics were produced in all preparations that would make canal filling difficult. To modify the typical preparations, alteration of the enlarging flutes, use of rasping rather than rotation of the instruments, and a flaring technique are recommended.

Dental Pulp Cavity↗
PubMed2003

To shape or not to shape...simulated bougie-assisted difficult intubation in a manikin.

Thirty anaesthetists attempted to place a derived 'optimal' curve bougie or a straight bougie in the trachea of a manikin, in a randomised cross-over study. A Grade 3 Cormack and Lehane laryngoscopic view was simulated. The anaesthetists were blinded to success (tracheal placement) or failure (oesophageal placement). The success rates with the curved and straight bougies were 83 and 7%, respectively, giving a difference (95% confidence interval) of 77% (54-87%) between the two bougies (p < 0.0001). On a separate occasion, under identical laboratory conditions, 30 anaesthetists attempted to place a straight coudé (angled)-tipped bougie or a straight straight-tipped bougie in the trachea of a manikin. The success rates with the coudé- and straight-tipped bougies were 43 and 0%, respectively, giving a difference (95% confidence interval) of 43% (21-61%) between the two bougies (p < 0.001). These results suggest that bougies used to facilitate difficult intubation should be curved and have a coudé tip.

Clinical Competence↗
PubMed2001

An adaptive-focus statistical shape model for segmentation and shape modeling of 3-D brain structures.

This paper presents a deformable model for automatically segmenting brain structures from volumetric magnetic resonance (MR) images and obtaining point correspondences, using geometric and statistical information in a hierarchical scheme. Geometric information is embedded into the model via a set of affine-invariant attribute vectors, each of which characterizes the geometric structure around a point of the model from a local to a global scale. The attribute vectors, in conjunction with the deformation mechanism of the model, warranty that the model not only deforms to nearby edges, as is customary in most deformable surface models, but also that it determines point correspondences based on geometric similarity at different scales. The proposed model is adaptive in that it initially focuses on the most reliable structures of interest, and gradually shifts focus to other structures as those become closer to their respective targets and, therefore, more reliable. The proposed techniques have been used to segment boundaries of the ventricles, the caudate nucleus, and the lenticular nucleus from volumetric MR images.

Brain↗
PubMed1988

The head shapes of some mammalian spermatozoa and their possible relationship to the shape of the penetration slit through the zona pellucida.

A method has been developed for establishing from electron micrographs the radius of curvature of rabbit and guinea-pig sperm nuclei in head-to-tail section (the major axis), and of guinea-pig spermatozoa with intact acrosomes in transverse section (the minor axis). Radii of curvature of head-to-tail sections lie, for the most part, between 7 and 100 microns in both species. Guinea-pig sperm nuclei in transverse section show a range of radii between 3 and 10 microns, and approximate, therefore, caps of prolate spheroids. The method is not applicable to rat and mouse spermatozoa but Nomarski light microscopy suggests that these nuclei are straight in the longitudinal direction. The distribution of the radii of curvature in rabbit sperm nuclei is similar to that of the radii of curvature of penetration slits through the zona pellucida of the rabbit egg. It is suggested that longitudinal curvature of sperm heads is correlated with any curvature of the penetration slit.

Animals↗