Assessment of shoulder dimensions and angles of porcelain bonded to metal crown preparations

This research examined hand preference for a bimanual task in 45 tufted capuchin (Cebus apella) and 55 rhesus macaque (Macaca mulatta) monkeys. Investigators presented subjects with plastic tubes lined with food and noted which hand the animals used to hold the tubes and which hand the animals used to remove the food. Several significant findings emerged from this investigation. First, rhesus macaques, but not tufted capuchins, exhibited a population-level bias toward use of the right hand (although the difference in direction of hand preference between species was not significant). Second, capuchins exhibited greater hand preference strength than did macaques. Third, among capuchins, but not among macaques, hand preference strength was greater for adults than for immatures. Finally, both species used their index digit to remove food most frequently when compared with other digits. Findings of hand preference direction and strength in this study were compared with other findings noted for chimpanzees which performed a bimanual tube task in a previous study. The authors conclude that using the same procedure to compare hand preference across species represents a powerful research tool that can lead to a more complete understanding of the evolution and ontogenesis of primate handedness.     

Geometrics of tooth wear

Wear measurement implies the need for comparative measurements based on a reference frame. In this study, part of a tooth surface (common area) is proposed to be a reference frame for the comparative measurement. A registration procedure applies an iterative closest point algorithm for the least square best fit of the two surfaces on this common area. When the common area matches the best fit condition, the difference at the remaining part of the tooth surface represents changes between the two surfaces; in this case signifying tooth wear.The minimum requirements to verify tooth wear results are a three quadrant spherical surface of a molar tooth to be common area, and the fit of the common area needs to be less than 10 μm, to achieve the sensitivity of wear measurement up to the 100 μm level on the occlusal tooth surface. Incise apparatus was used for the digitisation of the tooth surface. Cloud, a 3-D image analysis software package was utilised for visualisation, registration and image analysis. A mathematical scrutiny was applied to validate the findings in theory. The proposed methodology is proven to be adequate to quantify tooth wear.     

Effects of porous barriers such as coral reefs on coastal wave propagation

Observations following the Sumatra Tsunami in Sri Lanka have indicated significantly enhanced wave heights and water inundations in areas where coral poaching has been prevalent. It has been hypothesized [EOS, 86(33), 2005] that low-resistance paths created by coral removal have led to water jetting through them, while simultaneously reducing flow speeds in nearby coral-laden areas that offer higher bottom resistance to the flow. A laboratory experiment to verify this hypothesis is described in this paper, where corals are simulated using a submerged porous barrier made of a uniform array of rods that impose enhanced drag on the flow. The flow velocities pertinent to an oncoming solitary wave packet on a slope are measured in the presence and absence of the simulated uniform coral cover as well as with an opening (gap) in the coral canopy. It is shown that the coral canopy substantially decreases the flow velocity due to increase in the bottom drag coefficient, which is a strong function of the canopy porosity. The exit flow velocity from the gap is significantly higher compared to the surroundings, thus leading to jetting flow. The magnitude of jetting is a strong function of porosity, in addition to a suite of other parameters that accounts for waves, corals, water depth and gap size. The results support the notion that during isolated wave events the removal of natural barriers may cause local flow intensification, thus leading to adverse impacts on coastal assets and ecosystems in areas of barrier removal.     

Variation in labial shoulder geometry of metal ceramic crown preparations: a finite element analysis

BACKGROUND: The anatomic variation of the frontal sinus and frontal recess can create both a diagnostic and therapeutic challenge. Most cases of frontal sinus disease can now be treated by endoscopic approaches. For refractory cases or those with severe pathology, the microscopically controlled drainage (MCD) operation has at times been successful and spared the patient the morbidity of an external approach. The aim of this study was to evaluate microscopically controlled frontal sinus surgery in these difficult cases. MATERIAL AND METHODS: Prospective analysis was performed on the efficacy of MCD in patients for whom endoscopic sinus surgery had failed or in primary cases with severe pathology or unfavorable anatomy. The technique employs a self-retaining endonasal retractor and a diamond bur under microscopic visualization to remove solid bone (frontal spine) obstructing the sinus drainage and allow a wide opening of the frontal recess while causing minimal mucosal damage. Unilateral drainage (extended frontal sinus drainage operation), and in some cases bilateral drainage (median drainage procedure) is employed. RESULTS: With an average of 23 months of follow-up, over 90% of patients were either free of symptoms or substantially improved after the MCD procedure. Three patients required revision surgery (extend the opening into a median drainage procedure) for adequate relief of symptoms. CONCLUSIONS: The MCD procedure is highly successful in the treatment of frontal recess disease, particularly in those cases of severe pathology or difficult anatomy. It may be used in those cases refractory to standard endoscopic sinus surgery where an external approach and frontal sinus obliteration are contemplated. As with endoscopic sinus surgery, precise knowledge of the frontal recess and neighboring landmarks is critical, and adequate drainage with minimal mucosal disruption should be the goal.