Anticaries potential of low fluoride dentifrices found in the brazilian market

CNPQ – CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOLow-fluoride (F) dentifrices (<600 µg F/g) are widely available worldwide, but evidence to recommend the use of such dentifrices, with either regular or improved formulations, is still lacking. Therefore, the aim of this study was to evaluate the anticaries potential of low-F dentifrices found in the Brazilian market, using a validated and tested pH-cycling model. Enamel blocks were selected by surface hardness (SH) and randomized into four treatment groups (n=12): non-F dentifrice (negative control), low-F dentifrice (500 μg F/g), low-F acidulated dentifrice (550 μg F/g) and 1,100 μg F/g dentifrice (positive control). The blocks were subjected to pH-cycling regimen for 8 days and were treated 2x/day with dentifrice slurries prepared in water (1:3, w/v). The pH of the slurries was checked, and only the acidulated one had low pH. After the pH cycling, SH was again determined and the percentage of surface hardness loss was calculated as indicator of demineralization. Loosely- and firmly-bound F concentrations in enamel were also determined. The 1,100 μg F/g dentifrice was more effective than the low-F ones to reduce enamel demineralization and was the only one that differed from the non-F (p<0.05). All F dentifrices formed higher concentration of loosely-bound F on enamel than the non-F (p<0.05), but the 1,100 μg F/g was the only one that differed from the non-F in the ability to form firmly-bound F. The findings suggest that the low-F dentifrices available in the Brazilian market, irrespective of their formulation, do not have anticaries potential27315CNPQ – CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOCNPQ – CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOsem informaçã

Maize inbreds for multiple resistance breeding against major foliar, ear and stalk rot diseases

Resistance breeding is considered the most effective and eco-friendly method to manage most of the crop diseases, but it can be challenging to find sources of resistance in maize for short growing season regions. In this study, 218 maize inbreds were evaluated in order to select those, which possess resistance to one or more of the following diseases:  Northern Corn Leaf Blight (NCLB), common rust, eyespot, grey leaf spot (GLS), goss’s bacterial wilt and leaf blight (goss’s wilt), Gibberella (fusarium) ear and stalk rot, and common smut. Significant variation in disease resistance was detected in the inbreds evaluated. Twenty-six inbreds, most of them of Canadian origin, were found to possess excellent resistance to multiple diseases. Three inbreds (CO428, CO470 and CO471) exhibited resistance to five foliar diseases (NCLB, common rust, eyespot, GLS, and goss’s wilt), while another seven inbreds had a resistant reaction to four diseases (CO452, CO466 and CO468 to common rust, eyespot, GLS and goss’s wilt; C0473 to NCLB, common rust, GLS and goss’s wilt; CO464 to NCLB, eyespot, GLS, and goss’s wilt, and PHZ51 to eyespot, ERSC, common smut, and goss’s wilt). Five of these inbreds also had intermediate resistance against stalk and ear rot. Forty-five inbreds were found to have resistance against two to three diseases. Inbreds CO457, CO458, CO459 and CO460 released as highly resistance to common rust were also found to have good resistance against eyespot, and GLS or goss’s wilt. CO450 released for eyespot resistance had good resistance against common rust and GLS, and moderate resistance against goss’s wilt. Three inbreds CO387, CO441, and CO449 were found to have resistance for gibberellic ear rot both by silk and kernel inoculation methods and common smut. Most of these inbreds found resistant in this study were from the Stiff Stalk (BSSS), Lancaster and Iodent maize heterotic groups. Many of the resistant inbreds identified in this study are excellent sources of resistance to leaf, ear and stalk rot diseases, and could be utilized in maize breeding programs for developing new hybrids with multiple disease resistance

Effect of microleakage and fluoride on enamel-dentine demineralization around restorations

There is no consensus about an association between microleakage and secondary caries, especially considering the presence of fluoride (F) at the tooth/restoration interface. Thus, a randomized, double-blind, crossover study was carried out to evaluate in situ the effect of microleakage on caries around enamel-dentine restorations in the presence of F from dental materials or dentifrice, either alone or in combination. In 4 phases of 14 days each, 14 volunteers wore palatal devices containing dental slabs restored with composite resin (CR) or resin-modified glass ionomer cement (GI). Restorations were made without leakage (L-), following the recommended adhesive procedures, or with leakage (L+), in the absence of adhesive procedures. Plaque-like biofilm (PLB) was left to accumulate on the restored slabs, which were exposed extraorally to a 20% sucrose solution 10×/day. The volunteers used a non-F (NF) or an F (FD) dentifrice 3×/day, depending on the experimental phase. No differences were found between L+ or L- restorations (p > 0.05). Higher demineralization in both enamel and dentine around CR restorations was observed under NF (p < 0.05). F concentration was higher in the fluid of PLB exposed to FD or formed onto GI restoration (p < 0.05). These results suggest that while microleakage does not affect caries development, GI or FD may maintain increased F levels in the PLB, thereby decreasing caries progression