Liming in the sugarcane burnt system and the green harvest practice affect soil bacterial community in northeastern São Paulo, Brazil.

Here we show that both liming the burnt sugarcane and the green harvest practice alter bacterial community structure, diversity and composition in sugarcane fields in northeastern São Paulo state, Brazil. Terminal restriction fragment length polymorphism fingerprinting and 16S rRNA gene cloning and sequencing were used to analyze changes in soil bacterial communities. The field experiment consisted of sugarcane-cultivated soils under different regimes: green sugarcane (GS), burnt sugarcane (BS), BS in soil amended with lime applied to increase soil pH (BSL), and native forest (NF) as control soil. The bacterial community structures revealed disparate patterns in sugarcane-cultivated soils and forest soil (R = 0.786, P = 0.002), and overlapping patterns were shown for the bacterial community structure among the different management regimes applied to sugarcane (R = 0.194, P = 0.002). The numbers of operational taxonomic units (OTUs) found in the libraries were 117, 185, 173 and 166 for NF, BS, BSL and GS, respectively. Sugarcane-cultivated soils revealed higher bacterial diversity than NF soil, with BS soil accounting for a higher richness of unique OTUs (101 unique OTUs) than NF soil (23 unique OTUs). Cluster analysis based on OTUs revealed similar bacterial communities in NF and GS soils, while the bacterial community from BS soil was most distinct from the others. Acidobacteria and Alphaproteobacteria were the most abundant bacterial phyla across the different soils with Acidobacteria Gp1 accounting for a higher abundance in NF and GS soils than burnt sugarcane-cultivated soils (BS and BSL). In turn, Acidobacteria Gp4 abundance was higher in BS soils than in other soils. These differential responses in soil bacterial community structure, diversity and composition can be associated with the agricultural management, mainly liming practices, and harvest methods in the sugarcane-cultivated soils, and they can be detected shortly after harvest.

Effect of Nd:YAG (1064-nm) and Diode Laser (980-nm) EDTA Agitation on Root Dentin Ultrastructure Properties.

OBJECTIVE: The purpose of this study was to analyze the effects of agitation of 17% ethylenediaminetetraacetic acid (EDTA) with 1064 nm Nd:YAG and 980 nm diode laser on root dentin microhardness and superficial roughness (with confocal laser scanning microscopy [CLSM]). BACKGROUND DATA: Root canal irrigants are used in an attempt to minimize the negative effects of smear layer. MATERIALS AND METHODS: Twenty-five bovine roots were sectioned longitudinally and divided into five groups (n=10 each): (1) deionized water, (2) 17% EDTA, (3) 17% EDTA with 60 sec manual agitation, (4) 17% EDTA with 50 sec diode laser (2 W) agitation, and (5) 17% EDTA with 50 sec Nd:YAG (1.5 W) laser agitation. Microhardness and superficial roughness values were calculated before and after the procedures at the cervical, middle, and apical root thirds. Microhardness was statistically analyzed using two way ANOVA, paired t test, and Tukey's tests (α=0.05). Roughness was statistically analyzed using Kruskal-Wallis, paired t test, and Student-Newman-Keuls tests (α=0.05%). RESULTS: Statistically significant differences in microhardness and roughness were observed between the deionized water group and others. EDTA with 1064 nm Nd:YAG or 980 nm diode laser presented the lowest microhardness and the highest roughness values and was significantly different from EDTA with manual agitation and EDTA only (p<0.05). However, there were no differences in microhardness or dentin roughness between the root thirds (p>0.05). CLSM analysis showed that the control samples exhibited smoother surfaces than that of the EDTA groups. CONCLUSIONS: Nd:YAG 1064 nm and 980-nm diode laser EDTA agitation caused greater reduction in microhardness and increased roughness of root dentin than EDTA only or EDTA with manual agitation.