Effect of a calcium hydroxide/chlorhexidine paste as intracanal dressing in human primary teeth with necrotic pulp against Porphyromonas gingivalis and Enterococcus faecalis.

BACKGROUND: Intracanal medication is important for endodontic treatment success as it eliminates microorganisms that persist after biomechanical preparation. Aim. To evaluate the effect of two intracanal medications against Porphyromonas gingivalis and Enterococcus faecalis in the root canals of human primary teeth with necrotic pulp with and without furcal/periapical lesion, using quantitative real-time polymerase chain reaction (qRT-PCR). DESIGN: Thirty-two teeth with necrotic pulp were used. Twelve teeth did not present lesion, and 20 teeth presented radiographically visible furca/periapical lesion. Microbiological samples were collected after coronal access and biomechanical preparation. The teeth were medicated with calcium hydroxide pastes prepared with either polyethylene glycol or chlorhexidine. After 30days, the medication was removed and a third collection was performed. Microbiological samples were processed using qRT-PCR. Data were analysed by Wilcoxon and Mann-Whitney tests (α=0.05). RESULTS: There was no significant difference in the microbiota present in the primary teeth with and without furcal/periapical lesion. Biomechanical preparation was effective in reducing the number of microorganisms (P<0.05). The intracanal medications had similar antibacterial activity. CONCLUSION: The association of chlorhexidine with calcium hydroxide did not increase the antibacterial activity of the intracanal medication in the treatment of primary teeth with necrotic pulp with and without furcal/periapical lesion.

Distribution patterns and impact of transposable elements in genes of green algae.

Transposable elements (TEs) are DNA sequences able to transpose in the host genome, a remarkable feature that enables them to influence evolutive trajectories of species. An investigation about the TE distribution and TE impact in different gene regions of the green algae species Chlamydomonas reinhardtii and Volvox carteri was performed. Our results indicate that TEs are very scarce near introns boundaries, suggesting that insertions in this region are negatively selected. This contrasts with previous results showing enrichment of tandem repeats in introns boundaries and suggests that different evolutionary forces are acting in these different classes of repeats. Despite the relatively low abundance of TEs in the genome of green algae when compared to mammals, the proportion of poly(A) sites derived from TEs found in C. reinhardtii was similar to that described in human and mice. This fact, associated with the enrichment of TEs in gene 5' and 3' flanks of C. reinhardtii, opens up the possibility that TEs may have considerably contributed for gene regulatory sequences evolution in this species. Moreover, it was possible identify several instances of TE exonization for C. reinhardtii, with a particularly interesting case from a gene coding for Condensin II, a protein involved in the maintenance of chromosomal structure, where the addition of a transposomal PHD finger may contribute to binding specificity of this protein. Taken together, our results suggest that the low abundance of TEs in green algae genomes is correlated with a strict negative selection process, combined with the retention of copies that contribute positively with gene structures.