Effect of curing light emission spectrum on the nanohardness and elastic modulus of two bulk-fill resin composites.

OBJECTIVE: To determine the nanohardness and elastic moduli of two bulk-fill resin based composites (RBCs) at increasing depths from the surface and increasing distances laterally from the center after light curing. METHODS: Two bulk-fill dental RBCs: Tetric EvoCeram Bulk Fill (TECBF) and Filtek Bulk Fill Flowable (FBFF) were light cured in a metal mold with a 6mm diameter and a 10mm long semi-circular notch. The RBCs were photo-polymerized for 10s using a light emitting diode (LED) Bluephase Style curing light, with the original light probe that lacked the homogenizer. This light has two blue light and one violet light LED emitters. By changing the probe orientation over the mold, the light output from only two LEDs reached the RBC. Measurements were made using: (i) the light from one violet and one blue LED, and (ii) the light from the two blue LEDs. Five specimens of each RBC were made using each LED orientation (total 20 specimens). Specimens were then stored in the dark at 37°C for 24h. Fifty indents were made using an Agilent G200 nanoindentor down to 4mm from the surface and 2.5mm right and left of the centerline. The results were analyzed (alpha=0.05) using multiple paired-sample t-tests, ANOVA, Bonferroni post-hoc tests, and Pearson correlations. RESULTS: The elastic modulus and nanohardness varied according to the depth and the distance from the centerline. For TECBF, no significant difference was found between the spatial variations in the elastic modulus or hardness values when violet-blue or blue-blue LEDs were used. For FBFF, the elastic modulus and nanohardness on the side exposed to the violet emitter were significantly less than the side exposed to the blue emitter. A strong correlation between nanohardness and elastic modulus was found in all groups (r(2)=0.9512-0.9712). SIGNIFICANCE: Resin polymerization was not uniform throughout the RBC. The nanohardness and elastic modulus across two RBC materials were found to decline differently according to the orientation of the violet and blue light LED emitters within the curing light.

Pesticide use and opportunities of exposure among farmers and their families: cross-sectional studies 1998-2006 from Hebron governorate, occupied Palestinian territory.

BACKGROUND: Adverse health effects caused by pesticide exposure have been reported in occupied Palestinian territory and the world at large. The objective of this paper is to compare patterns of pesticide use in Beit-U'mmar village, West Bank, between 1998 and 2006. METHODS: We studied two populations in Beit-U'mmar village, comprised of: 1) 61 male farmers and their wives in 1998 and 2) 250 male farmers in 2006. Both populations completed a structured interview, which included questions about socio-demographic factors, types of farming tasks, as well as compounds, quantities, and handling of pesticides. Using the 1998 population as a reference, we applied generalized linear regression models (GLM) and 95% confidence intervals (CI) in order to estimate prevalence differences (PD) between the two populations. RESULTS: In 1998, farmers used 47 formulated pesticides on their crops. In 2006, 16 of these pesticides were still in use, including five internationally banned compounds. There were positive changes with less use of large quantities of pesticides (>40 units/year) (PD -51; CI -0.60, -0.43), in applying the recommended dosage of pesticides (PD +0.57; CI +0.48, +0.68) and complying with the safety period (PD +0.89; CI+0.83, +0.95). Changes also included farmers' habits while applying pesticides, such as less smoking (PD -0.20; CI-0.34, -0.07) and eating at the work place (PD -0.33; CI-0.47, -0.19). No significant changes were found from 1998 to 2006 regarding use of personal protective equipment, pesticide storage, farmers' habits after applying pesticides, and in using some highly hazardous pesticides. CONCLUSIONS: The results were based on two cross-sectional surveys and should be interpreted with caution due to potential validity problems. The results of the study suggest some positive changes in the handling of pesticides amongst participants in 2006, which could be due to different policy interventions and regulations that were implemented after 1998. However, farm workers in Beit -U'mmar village are still at risk of health effects because of ongoing exposure to pesticides. To the best of our knowledge, no studies on long-term changes in pesticide use have been reported from developing countries.

Fecundability among newly married couples in agricultural villages in Palestine: a prospective study.

BACKGROUND: The validity of studies on fecundability in Western countries has been questioned. The complexity of societal and cultural factors makes it difficult to dissect pure biological impact. Our aim was to assess couple fecundability in a population which to a large degree is unaffected by the same socio-cultural influences. METHODS: We conducted a prospective study on time-to-pregnancy (TTP), with a complete follow-up between 2005 and 2007, among 205 newly married couples in two Palestinian agricultural villages. The couples had never had premarital sex and all planned to become pregnant. We followed the couples from the date of marriage until pregnancy was recognized by a pregnancy test, or at maximum 12 months. RESULTS: Overall fecundability was 0.17. Unexpectedly, cycle fecundability increased during the first cycles from 0.16 (cycle 1) to 0.25 (cycle 5), after which the expected decline started. The initial increase in fecundability was restricted to couples with teenage brides. A total of 70.7% of the couples conceived within 6 cycles, 13.4% did not conceive during follow-up. Prolonged TTP was associated with the oldest age category for both genders. Educated women appeared to be highly fecund. CONCLUSIONS: The fecundability result is probably uninfluenced by the societal and cultural factors seen in Western populations, because premarital sex is a taboo in this Muslim population. The increase in fecundability during the first months following marriage is difficult to interpret, but could be due to either behavioural or biological influences.