The aim of this study was to determine the presence of para-chloroaniline  (PCA) obtained by the mixture of 5,25% sodium hypochlorite (NaOCl) and 2% chlorhexidine (CHX), evaluated by nuclear magnetic resonance spectroscopy (NMR-H-1) at 600MHz. Initially a  commercial sample of 98% PCA (group 1: GPCA) was analyzed by NMRH-1 combining it with dimethylsulfoxide perdeuterated as solvent, in order to obtain the basal spectra.  Ten samples were then prepared by combining equal amounts of  5,25%NaOCl and 2%CHX (group 2:GHC) (PROPORTION 1:1 v/v) by manual stirring. Each sample was then spinned for 10 minutes at 25Cº, in order to eliminate the supernatant and to obtain the precipitate, which was prepared at dry vacuum to finally isolate the solid precipitate. The precipitate was again dissolved in d6-DMSO to perform the NMR.H-1 analysis. Commercial PCA showed a distinctive spectra, with  a characteristic double sign at 7.02-7.03 ppm and 6.58-6.59 ppm. Experimental samples lack of this distinctive  spectra, instead, they all showed a complex combination of signs, which none correspond to pure PCA.

This study aimed to analyze the effect of several final irrigation protocols on tubular permeability and push-out bond strength of an epoxy resin-based cement to radicular dentin. The crowns of 110 human teeth were removed to standardize at 17mm in length. The root canals were instrumented and irrigated with 5ml of 5% NaOCl and 17% EDTA. The samples were then randomly divided into 5 groups (n=22) according to the final irrigation protocol. Subsequently, the samples were subdivided into two different groups to assess dentin permeability or the evaluation of the push-out bond strength. In Group 1, all samples displayed the formation of brown-like precipitates. Group 2 and Group 5 demonstrated cleaner dentin walls. The push-out bond test after 72 hours denoted a significant difference when comparing Group 1 vs Group 2 and Group 1 vs Group 3. After thermocycling, a significant difference is observed between Group 1 and all remaining groups. The irrigation protocol using distilled water prior to irrigation with chlorhexidine significantly reduces the formation of intracanal precipitates by avoiding interactions between irrigants. The push-out bond strength of epoxy resin-based cement is directly influenced by the precipitates formed in the root canal after irrigation and the time of thermocycling.