Defect propagation in NiTi rotary instruments: a noncontact optical profilometry analysis.

AIM: To evaluate the presence and propagation of defects and their effects on surfaces of nickel-titanium (NiTi) instruments using noncontact, three-dimensional optical profilometry, and to assess the accuracy of this method of investigation. METHODOLOGY: The flute surface areas of instruments from two commercial instrumentation systems, namely Reciproc R25 (n = 5) and WaveOne Primary (n = 5), were assessed and compared before and after performing two instrumentation cycles in simulated root canals in clear resin blocks. All the analyses were conducted on areas measuring 211 × 211 µm, located 3 mm from the tips of the instruments. A quantitative analysis was conducted before and after the first and second instrumentation cycles, using the Sa (average roughness over the measurement field), Sq (root mean square roughness) and Sz (average height over the measurement field) amplitude parameters. All the data were submitted to statistical analysis at a 5% level of significance. RESULTS: There was a significant increase (P = 0.007) in wear in both groups, especially between baseline and the second instrumentation cycle, with significantly higher wear values being observed on WaveOne instruments (Sz median values = 33.68 and 2.89 µm, respectively, for WO and RP groups). A significant increase in surface roughness (P = 0.016 and P = 0.008, respectively, for Sa and Sq) was observed in both groups from the first to the second instrumentation cycle, mostly in WaveOne specimens. Qualitative analysis revealed a greater number of defects on the flute topography of all the instruments after use. CONCLUSIONS: More defects were identified in WaveOne Primary instruments compared to Reciproc R25, irrespective of the evaluation stage. The investigation method provided an accurate, repeatable and reproducible assessment of NiTi instruments at different time-points.

A new method for the assessment of the surface topography of NiTi rotary instruments.

AIM: To describe a new method for the assessment of nanoscale alterations in the surface topography of nickel-titanium endodontic instruments using a high-resolution optical method and to verify the accuracy of the technique. METHODOLOGY: Noncontact three-dimensional optical profilometry was used to evaluate defects on a size 25, .08 taper reciprocating instrument (WaveOne® ), which was subjected to a cyclic fatigue test in a simulated root canal in a clear resin block. For the investigation, an original procedure was established for the analysis of similar areas located 3 mm from the tip of the instrument before and after canal preparation to enable the repeatability and reproducibility of the measurements with precision. All observations and analysis were taken in areas measuring 210 × 210 µm provided by the software of the equipment. RESULTS: The three-dimensional high-resolution image analysis showed clear alterations in the surface topography of the examined cutting blade and flute of the instrument, before and after use, with the presence of surface irregularities such as deformations, debris, grooves, cracks, steps and microcavities. CONCLUSIONS: Optical profilometry provided accurate qualitative nanoscale evaluation of similar surfaces before and after the fatigue test. The stability and repeatability of the technique enables a more comprehensive understanding of the effects of wear on the surface of endodontic instruments.

The earliest stages of ecosystem succession in high-elevation (5000 metres above sea level), recently deglaciated soils.

Global climate change has accelerated the pace of glacial retreat in high-latitude and high-elevation environments, exposing lands that remain devoid of vegetation for many years. The exposure of 'new' soil is particularly apparent at high elevations (5000 metres above sea level) in the Peruvian Andes, where extreme environmental conditions hinder plant colonization. Nonetheless, these seemingly barren soils contain a diverse microbial community; yet the biogeochemical role of micro-organisms at these extreme elevations remains unknown. Using biogeochemical and molecular techniques, we investigated the biological community structure and ecosystem functioning of the pre-plant stages of primary succession in soils along a high-Andean chronosequence. We found that recently glaciated soils were colonized by a diverse community of cyanobacteria during the first 4-5 years following glacial retreat. This significant increase in cyanobacterial diversity corresponded with equally dramatic increases in soil stability, heterotrophic microbial biomass, soil enzyme activity and the presence and abundance of photosynthetic and photoprotective pigments. Furthermore, we found that soil nitrogen-fixation rates increased almost two orders of magnitude during the first 4-5 years of succession, many years before the establishment of mosses, lichens or vascular plants. Carbon analyses (pyrolysis-gas chromatography/mass spectroscopy) of soil organic matter suggested that soil carbon along the chronosequence was of microbial origin. This indicates that inputs of nutrients and organic matter during early ecosystem development at these sites are dominated by microbial carbon and nitrogen fixation. Overall, our results indicate that photosynthetic and nitrogen-fixing bacteria play important roles in acquiring nutrients and facilitating ecological succession in soils near some of the highest elevation receding glaciers on the Earth.

The Health Belief Model and HIV risk behaviours: a causal model analysis among Anglos, African-Americans and Mexican-Americans.

A causal model of the Health Belief Model (HBM) is empirically evaluated which emphasizes possible indirect paths linking distal demographic and seriousness/susceptibility variables to HIV risk behaviours among Anglo, African-American, and Mexican-American adults. A specific focus of the paper is upon alcohol-related expectancies (anticipation of disinhibitory effects of alcohol upon sexual behavior) as a 'barrier' to preventive behaviours. Ethnic comparisons stem both from the paucity of available research on the HBM in minority populations and from recent questions regarding the applicability of rational models such as the HBM among minority groups. Analyses of data from a community sample of 1390 adults indicate relatively consistent direct effects of barriers for males and benefits for females upon HIV risk behaviors. The analyses suggest distinct paths operative among males and females. The susceptibility-barriers-risk behaviours path among males may suggest that alcohol-related expectancies (barriers in this model) may be more strongly related to risk behaviours among males than minority females.

Solitary drinking, social isolation, and escape drinking motives as predictors of high quantity drinking, among Anglo, African American and Mexican American males.

This paper addresses the phenomenon of 'solitary drinking', considering whether Anglo, African American and Mexican American male regular drinkers differ in the propensity to drink in solitary contexts and whether such differences may help to explain observed ethnic variation in patterns of heavy drinking. Further, the paper considers whether apparent relationships between solitary drinking and drinking patterns are explained by individual personality characteristics such as social isolation and/or by endorsement of 'escape drinking' motives. Data were analysed from a random community sample of 481 adult male regular drinkers in San Antonio, Texas, USA. Contingency table and logistic regression analyses indicated that initially observed ethnic differences in high quantity and high maximum drinking were largely eliminated by controls for education, escape motives and solitary drinking. Ethnic variation in the role of solitary drinking was suggested as well, with solitary drinking more strongly related to high quantity consumption, in particular, among African Americans than among Mexican Americans. The nature of the observed interactions suggests that fundamental differences between Anglos and African Americans in the roles of solitary drinking and escape drinking motives may underlie seemingly similar frequent, lower quantity drinking patterns in these groups that appear more frequently than among Mexican American males.

Acculturation and drinking patterns among U.S. Anglos, blacks, and Mexican Americans.

The relationship between acculturation, generational status/nativity and drinking patterns is examined using data from a 1988 community survey of 1286 adult regular drinkers (at least two drinks/month) in San Antonio, Texas. This sample includes 412 Anglo, 239 Black, and 635 Mexican American respondents, with Mexican Americans further classified into high, medium, and low acculturation groups using a language-use-based acculturation measure. This data set allows comparisons between racial/ethnic majority and minority groups with further comparisons between Black and Mexican American subgroups. These racial/ethnic and acculturation level comparisons highlight the effects of minority status and cultural differences between groups with regard to drinking patterns. Overall, the analyses indicate little evidence to support an 'acculturation stress' model of alcohol use, wherein the stresses of acculturation produce higher levels of alcohol consumption among moderately or higher acculturation groups. Generally, in our data, quantity and frequency consumption was somewhat higher among the least acculturated males and moderately acculturated females. Further analyses by generational status indicate heavier consumption patterns among second-generation individuals, especially among the less acculturated, though those differences were eliminated by controls. The findings highlight inadequacies of using generational status/nativity measures alone to assess acculturation level. Further, joint effects of acculturation level and generational status suggest the viability of a cultural marginality model of acculturation, though many of the effects of acculturation and generational status are explained by demographic and psychosocial factors.

"Machismo," self-esteem, education and high maximum drinking among anglo, black and Mexican-American male drinkers.

This study seeks to clarify the relevance of machismo to patterns of high maximum drinking among male drinkers. Specifically, the study describes the psychometric properties of a newly developed 7-item machismo measure, compares levels of machismo and self-esteem for a sample of Anglo, black and Mexican-American males, and examines both main and interaction effects of machismo, self-esteem and education as predictors of alcohol use in these racial/ethnic subgroups. Logistic regression analyses document interaction between race/ethnicity, machismo, self-esteem and education, which calls into question the presumed importance of machismo as a cultural element causing heavy drinking patterns among Mexican-American males.