The complete seating of full coronal restorations during cementation is hindered by the inability of cement to flow from the internal surface of the crown, and possible binding of the crown on the tooth. Perforation venting is an effective technique to allow full seating but requires repair of the perforation. Provision of space between the crown and the tooth for cement flow is also an effecti...

Most archaeological and fossil teeth are heavily worn, and this greatly limits the usefulness of tooth crown diameter measurements, as they are usually defined at the widest points of the crown. There are alternatives, particularly measurements at the cervix of the tooth, where the crown joints the root, and measurements along a diagonal axis in molars, that are much less affected by wear. Thes...

Light fluctuations and crown traits were studied for saplings of four tree species in a Costa Rican rain forest. Light fluctuations (1988–1994) were assessed by annual light estimations above saplings, using a visual crown position index. Crown traits in 1994 and growth between 1994 and 1995 were measured. Crown position values varied between 1.5 and 2.5. Of the 70 saplings only four were found...

Growth and survival of young European beech (Fagus sylvatica L.) is largely dependent on water availability. We quantified the influence of water stress (measured as Available Soil Water Storage Capacity or ASWSC) on vitality of young beech plants at a dry site. The study site was located in a semi-natural sessile oak (Quercus petraea (Mattuschka) Liebl.) stand adjacent to beech stands on a roc...

The aim of this study was to develop a relatively rapid, simple and repeatable method to characterize the crown architecture of Queensland maple (Flindersia brayleyana F. Muell.) by vertical hemispherical photography. Calibration scales were developed to provide horizontal planes of measurement at heights from 15 to 40 m above the camera. Hemispherical images of tree crowns were merged with the...

Zinc (Zn) deficiency is one of the leading nutrient disorders in rice (Oryza sativa). Many studies have identified Zn-efficient rice genotypes, but causal mechanisms for Zn deficiency tolerance remain poorly understood. Here, we report a detailed study of the impact of Zn deficiency on crown root development of rice genotypes, differing in their tolerance to this stress. Zn deficiency delayed c...

The dynamics of a water jet on a flat free surface are investigated using a nanosecond pulsed laser for creating an oscillating bubble with different depths beneath the free surface. A thin jet is shown to deform a crater surface resulted from surface depression and cause a circular ring-shaped crater on the connection surface between the crater of surface depression and the thin jet. The colla...

tall wheat grass (agropyron elongatum), as many other grasses, benefits from wide genetic bases in iran. estimation of genetic diversity and a selection of suitable genotypes is the initial step for developing adaptable synthetic varieties in many cool season grasses. in order to investigate production, variation and genetic similarity of 25 tall wheat grass genotypes, an experiment was conduct...

always on kingdom history of the world a king without a crown is unconceivable. the persian kings were not exception of this rule. iranian ancient kings crown as one of the aspects of the monarchy and power, the image of king while makes he distinguishes from other persons is visible in various artistic works. one of the important artistic works that image of iran’s kings with their power symbo...

introduction : to achieve success in treatment, one cannot ignore the knowledge of pulp anatomy. mandibular premolars are considered to be the most difficult teeth for endodontic therapy due to high variability in their canal morphology. it is possible that a relation exists between the crown size and the number of extra canals in these teeth, so this in vitro study aims to investigate the rela...