Direct evidence showing the effect of root surface iron plaque on arsenite and arsenate uptake into rice (Oryza sativa) roots

The present study aimed to investigate the effects of root surface iron plaque on the uptake kinetics of arsenite and arsenate by excised roots of rice (Oryza sativa) seedlings. The results demonstrated that the presence of iron plaque enhanced arsenite and decreased arsenate uptake. Arsenite and arsenate uptake kinetics were adequately fitted by the Michaelis-Menten function in the absence of plaque, but produced poor fits to this function in the presence of plaque. Phosphate in the uptake solution did not have a significant effect on arsenite uptake irrespective of the presence of iron plaque; however phosphate had a significant effect on arsenate uptake. Without iron plaque, phosphate inhibited arsenate uptake. The presence of iron plaque diminished the effect of phosphate on arsenate uptake, possibly through a combined effect of arsenate desorption from iron plaque.

Risk indicators associated with root decay in independently living older adults

Objective: To determine the risk indicators associated with root caries experience in a cohort of independently living older adults in Ireland.
Methods: The data reported in the present study were obtained from a prospective longitudinal study conducted on the risk factors associated with root caries incidence in a cohort of independently living older adults (n=334). Each subject underwent an oral examination, performed by a single calibrated examiner, to determine the root caries index and other clinical variables. Questionnaires were used to collect data on oral hygiene habits, diet, smoking and alcohol habits and education level. A regression analysis with the outcome variable of root caries experience (no/yes) was conducted.
Results: A total of 334 older adults with a mean age of 69.1 years were examined. 53.3% had at least one filled or decayed root surface. The median root caries index was 3.13 (IQR 0.00, 13.92). The results from the multivariate regression analysis indicated that individuals with poor plaque control (OR 9.59, 95%CI 3.84-24.00), xerostomia (OR 18.49, 95%CI 2.00-172.80), two or more teeth with coronal decay (OR 4.50, 95% CI 2.02-10.02) and 37 or more exposed root surfaces (OR 5.48, 95% CI 2.49-12.01) were more likely to have been affected by root caries.
Conclusions: The prevalence of root caries was high in this cohort. This study suggests a correlation between root caries and the variables poor plaque control, xerostomia, coronal decay (≥2 teeth affected) and exposed root surfaces (≥37). The significance of these risk indicators and the resulting prediction model should be further evaluated in a prospective study of root caries incidence.
Clinical Significance: Identification of risk indicators for root caries in independently living older adults would facilitate dental practitioners to identify those who would benefit most from interventions aimed at prevention.

Cost-effectiveness of ART restorations in elderly adults: a randomized clinical trial

BACKGROUND: As the world population ages, the requirement for cost-effective methods of treating chronic disease conditions increases. In terms of oral health, there is a rapidly increasing number of dentate elderly with a high burden of maintenance. Population surveys indicate that older individuals are keeping their teeth for longer and are a higher caries risk group. Atraumatic Restorative Treatment (ART) could be suitable for patients in nursing homes or house-bound elderly, but very little research has been done on its use in adults.

OBJECTIVES: To compare the cost-effectiveness of ART and a conventional technique (CT) for restoring carious lesions as part of a preventive and restorative programme for older adults.

METHODS: In this randomized clinical trial, 82 patients with carious lesions were randomly allocated to receive either ART or conventional restorations. Treatment costs were measured based on treatment time, materials and labour. For the ART group, the cost of care provided by a dentist was also compared to the cost of having a hygienist to provide treatment. Effectiveness was measured using percentage of restorations that survived after a year.

RESULTS: Eighty-two patients received 260 restorations, that is, 128 ART and 132 conventional restorations. 91.1% of the restorations were on one surface only. After a year, 252 restorations were assessed in 80 patients. The average cost for ART and conventional restorations was €16.86 and €28.71 respectively; the restoration survival percentages were 91.1% and 97.7%, respectively. This resulted in a cost-effectiveness ratio of 0.18 (ART) and 0.29 (CT). When the cost of a hygienist to provide ART was inserted in the analysis, the resulting ratio was 0.14.

CONCLUSIONS: Atraumatic restorative treatment was found to be a more cost-effective alternative to treat older adults after 1 year, compared to conventional restorations, especially in out of surgery facilities and using alternative workforce such as hygienists. Atraumatic restorative treatment can be a useful tool to provide dental care for frail and fearful individuals who might not access dental treatment routinely.

BUCKLED LAYER STRUCTURE FOR ATOMIC ADSORPTION ON W(100) - THE (ROOT-2X-ROOT-2)R45-DEGREES NITROGEN STRUCTURE FROM ATLEED

Adsorption of 0.5 monolayer of N adatoms on W{100} results in a sharp (root 2 X root 2)R45 degrees LEED pattern. The only previous quantitative LEED study of this system gave a simple overlayer model with a Pendry R-factor of 0.55. An exhaustive search has been made of possible structures, including a novel vacancy reconstruction, displacive reconstructions and underlayer adsorption. From this work a new overlayer structure is derived with an R(p) value of 0.22, displaying a considerable buckling of 0.27 +/- 0.05 Angstrom within the second W layer and consequently involving large changes in the interlayer spacings of the surface. The N adatom is pseudo-five-fold coordinated to the W surface, bonding to a second-layer W atom with a nearest-neighbour bond length of 2.13 Angstrom and with the four next-nearest-neighbour W atoms in the surface plane at 2.27 Angstrom. The structure does not resolve the work function anomaly observed on this surface.