Telescopic crowns: extra-oral and intra-oral retention force measurement--in vitro/in vivo correlation

doi: 10.1111/j.1741‐2358.2011.00477.x
Telescopic crowns: extra‐oral and intra‐oral retention force measurement –in vitro/in vivo correlation Objective: This study deals with the determination of the retentive forces of telescopic crowns measured extra‐ and intra‐orally and the correlation of these values. Background: The telescopic denture is a well‐documented solution for prosthetic rehabilitation for a partially edentulous jaw. Acceptable retention forces are needed to avoid inadvertent removal of the denture during movement of the jaws. Recent literature suggests 3–7 N per attachment to be acceptable. These values are only supported by in vitro studies. In vivo data are scarce, and a correlation of the in vitro and in vivo values is lacking. Material and Methods: Twenty‐five combined fixed‐removable prostheses with a total of 72 double crowns were used for extra‐oral retention force measurement prior to cementation (in vitro). The intra‐oral measurement was performed at 72 defined measuring points of the dentures 4–6 weeks after prosthetic rehabilitation (in vivo). A specifically designed measuring device was used. Results: The rank correlation showed that the in vitro and in vivo values correlate with each other (Spearman’s ρ = 0.5052). Additionally, it was found that the median values measured before (1.97N) insertion of the dentures were significantly lower than after (4.70N) insertion (Mann–Whitney test, p ≤ 0.0001). Conclusion: The retention forces measured before and after insertion of the denture correlate with each other although their dimension is significantly higher after insertion. The reason for this behaviour might be some tilting during removal. Nevertheless, the correlation allows a prediction of the clinically relevant forces by a measurement of the extra‐orally measured retentive values.     

Susceptibility of zinc-deficient wheat plants to colonization byFusarium graminearum Schw. Group 1

Wheat plants were grown at three levels of zinc nutrition in potted soil under controlled conditions. The surface soil in half of the pots was inoculated with a thin layer of milled chaff colonized byFusarium graminearum Group 1. Forty days after sowing, the plants were assessed for dry matter production and the extent of colonization by the pathogen. The concentration of zinc in the plant tissues was also determined.The zinc status of the plants ranged from severe deficiency through subclinical deficiency to sufficiency. The extent of colonization above the point of infection was decreased significantly by increasing the level of zinc supply. However, colonization of the seminal or secondary roots was not affected by zinc supply, nor was the incidence of infected plants. The unidirectional effect on resistance suggests that zinc has modified the contribution of the xylem flux to the upward spread of the pathogen.     

Assessing canopy health of native eucalypt forests

Summary   The assessment of forest health is an essential part of the monitoring of ecological sustainability in managed native forests. In Australia, unfortunately, very limited quantitative information on forest health is actually obtained for management and reporting purposes. In this article, we summarize current approaches used in Australia to assess native forest health and some recent developments in the application of remotely acquired digital imagery for classifying canopy health. In a recent study examining Bell miner associated dieback (BMAD), high-resolution airborne imagery was successfully manipulated to present severity categories for BMAD affected canopy. The potential of remotely sensed imagery lies not in map production but in the statistical modelling capacity of this spatial information, particularly when added to climatic and terrain-based spatial data sets. There are several statistical approaches to modelling these spatial datasets and in this article, we discuss our approach to producing a preliminary BMAD model. The importance of ground-based assessments is also emphasized and we recommend tree crown condition as a key health attribute for the spatial modelling of forests. Although significant progress has been made in the application of remote sensing technologies, the structural complexity of native forests means that there are still technical issues that require resolving before this approach becomes operationally routine.     

Evolutionary changes in the masticatory complex following the transition to farming in the southern Levant

A post-Pleistocene reduction trend in the dimensions of the masticatory complex followed the transition to agricultural lifestyle in several world regions. A major limitation of previous studies is large temporal gaps between the analyzed skeletal populations, which do not allow the detection and analysis of a diachronic morphological transition. In this work, we analyze a large number of specimens from the southern Levant, where agriculture first emerged in situ and for which there is a good diachronic sequence of the shift from a hunting-gathering way of life to a food producing, farming economy (12,000-7,000 uncalibrated bp). Changes in the masticatory complex are examined in the context of three prevailing dental reduction models: the Probable Mutation Effect (Brace,1963; Brace and Mahler,1971), Increasing Population Density Effect (Macchiarelli and Bondioli,1986) and Selective Compromise Effect (SCE) (Calcagno,1989). A series of linear regressions of dimension vs. time and coefficients of variation for each dimension are analyzed. Our results indicate significant reduction in the buccolingual but not mesiodistal dental dimensions and in the ramus breadth and anterior height dimensions of the mandible but not in its overall size. These findings, taken together with low coefficients of variation for the buccolingual dimensions, suggest selective pressure resulting in reduction of specific dimensions. The observed trend is in partial accordance with the SCE but differs from the trends observed in other regions, and is therefore best explained as a region-specific variant of the SCE.     

Synthesis of l‐threitol‐based crown ethers and their application as enantioselective phase transfer catalyst in Michael additions

A few new l ‐threitol‐based lariat ethers incorporating a monoaza‐15‐crown‐5 unit were synthesized starting from diethyl l ‐tartrate. These macrocycles were used as phase transfer catalysts in asymmetric Michael addition reactions under mild conditions to afford the adducts in a few cases in good to excellent enantioselectivities. The addition of 2‐nitropropane to trans ‐chalcone, and the reaction of diethyl acetamidomalonate with β‐nitrostyrene resulted in the chiral Michael adducts in good enantioselectivities (90% and 95%, respectively). The substituents of chalcone had a significant impact on the yield and enantioselectivity in the reaction of diethyl acetoxymalonate. The highest enantiomeric excess (ee ) values (99% ee ) were measured in the case of 4‐chloro‐ and 4‐methoxychalcone. The phase transfer catalyzed cyclopropanation reaction of chalcone and benzylidene‐malononitriles using diethyl bromomalonate as the nucleophile (MIRC reaction) was also developed. The corresponding chiral cyclopropane diesters were obtained in moderate to good (up to 99%) enantioselectivities in the presence of the threitol‐based crown ethers.     

Development and characterization of novel, polymorphic microsatellite markers for oat crown rust, Puccinia coronata

We report the development of 37 novel and polymorphic microsatellite markers for oat crown rust, Puccinia coronata f.sp. avenae. The allelic diversity ranged from two to 16 alleles per locus. Observed heterozygosity ranged from 0.000 to 0.971, and expected heterozygosity from 0.057 to 0.848. Thirteen of the loci were not in Hardy-Weinberg equilibrium, due to either the presence of null alleles, small sample size, or the effects of population subdivision (Wahlund's effect). All 37 primer pairs were tested with P. graminis and P. triticina showing that they are specific to P. coronata.     

Susceptibility of Thirty Cherry Genotypes on Phytophthora cactorum, P. citrophthora, P. citricola and P. parasitica

The diseases Phytophthor a crown and root rot consist of the most important problems in cherry cultivation. In this study, the susceptibility of 30 cherry genotypes to Phytophthora cactorum , P. citrophthora, P. parasitica and P. citricola was evaluated by using excised twig assay, excised shoot method and stem inoculation method. The results showed that all cherry genotypes tested were susceptible to all Phytophthora isolates used. Phytophthora parasitica and P. citrophthora were the most aggressive species. Host specificity of the Phytophthora isolates used in this study was not found although these isolates were from different plant species. In conclusion, because none of the cherry genotype showed a level of resistance to these pathogens, caution should be taken when these genotypes are used in locations, where these diseases are endemic.     

Comparison of theoretical and experimental data to evaluate substrate diffusional limitations for crown ether- and methyl-beta-cyclodextrin-activated serine protease subtilisin Carlsberg in tetrahydrofuran

Simple co-lyophilization of serine protease subtilisin Carlsberg with [12]-crown ether-4 (12-crown-4) or methyl-beta-cyclodextrin (MbetaCD) drastically increases its catalytic activity in organic solvents. We investigated whether the improved activity would cause substrate diffusional limitations. To experimentally assess the issue, the enzyme was inactivated with PMSF. Different amounts of active and inactive subtilisin were codissolved in 10 mM phosphate buffer (pH 7.8) followed by lyophilization with or without 12-crown-4 or MbetaCD. Initial rates for the transesterification reaction of N-acetyl-L-phenylalanine ethyl ester and 1-propanol in anhydrous THF were plotted vs. the amount of active enzyme present in the formulations. For all three enzyme formulations a linear relationship was observed and the results clearly show that activation of subtilisin Carlsberg by crown ethers and MbetaCD did not cause diffusional limitations. This was somewhat surprising because theoretical models predicted such diffusional limitations for the activated formulations. However, investigation of the protein powder particles obtained after co-lyophilization with 12-crown-4 and MbetaCD revealed a drastically reduced particle size for these formulations when suspended in THF. The particle micronization afforded by the excipients prevented substrate diffusional limitations, a factor that should be taken into account when designing improved enzyme formulations for synthetic applications in organic solvents.     

Concentration of selected elements in the roots and crowns of both primary and permanent teeth with caries disease

We examined the differences between the concentrations of chemical elements in caries-changed primary teeth and permanent ones with a division into the root and the crown. The study comprised 27 children aged from 4 to 11 yr and 36 adults aged from 36 to 71 yr. We examined the elements with the total reflection X-ray fluorescence method. The lowest concentrations of calcium, manganese, strontium, lead, and copper were in the roots of primary teeth compared to the roots of permanent ones. The calcium, nickel, zinc, lead, and copper concentrations were significantly higher in the roots of primary teeth than in the roots of permanent teeth. However, the zinc concentration was higher both in the root and crown of primary teeth than in permanent teeth. On the basis of our investigations, we can conclude that the content of some elements (manganese, copper, strontium, and lead) is higher in caries permanent teeth than in primary ones. The nickel and zinc concentrations are higher in the teeth of the children than the adults. However, the content of other elements (calcium, chromium, iron) is similar in both kinds of teeth.