Single session of Nd:YAG laser intracanal irradiation neutralizes endotoxin in dental root dentin.

Endotoxins released in the dental root by Gram-negative microorganisms can be neutralized by calcium hydroxide, when this medication is applied inside the root canal for at least seven days. However, several clinical situations demand faster root canal decontamination. Thus, for faster endotoxin neutralization, endodontists are seeking additional treatments. The in vitro study tested whether or not intracanal Nd:YAG laser irradiation would be able to neutralize endotoxin within the human dental root canal in a single session. Twenty-four human teeth with one root were mounted between two chambers. After conventional endodontic treatment, root canals were contaminated with Escherichia coli endotoxin. Then they were irradiated or not (controls) in contact mode with an Nd:YAG laser (1.5 W, 15 Hz, 100 mJ and pulse fluency of 124 J/cm2). The endotoxin activity was measured using the limulus lysate technique and data were statistically compared (p≤0.05). The concentration of active endotoxin measured in the negative control group was significantly lower than that of the positive control group (p=0.04). The concentrations of endotoxin in both irradiated groups were significantly lower than that of the positive control group (p=0.027) and similar to that of negative control group (p=0.20). A single session of intracanal Nd:YAG laser irradiation is able to neutralize endotoxin in the dental root tissues.

Expression of matrix metalloproteinases 2 and 9 in odontogenic myxoma in vivo and in vitro.

Odontogenic myxoma is a benign neoplasm, which presents local invasiveness and tendency for recurrence. Matrix metalloproteinases (MMPs) 2 and 9 are involved in tumor invasion. Thus, the aim of this study was to analyze the expression and activity of these MMPs in odontogenic myxoma in vivo and in vitro. Three cases of odontogenic myxoma and cultured cells derived from this tumor (Mix1 cell line) were used. The detection and activity of two MMPs (2 and 9) were performed by immunohistochemistry in formalin-fixed, paraffin-embedded sections of odontogenic myxoma and immunofluorescence of the cultured cells and, by gelatin zymographic analysis of Mix1 conditioned media, respectively. MMPs 2 and 9 were detected in vivo and in vitro. The zymographic assay detected latent MMP-2 as well as latent and active MMP-9. Based on our findings, we suggest that MMPs may be involved in local invasiveness of the odontogenic myxoma. MMP-9 is not only secreted by odontogenic myxoma but also has enzyme activity with no further stimulation. Other MMPs were not analyzed; however, our results suggest that the invasive behaviour of odontogenic myxoma could be related at least to MMP-9.