Introduction This study examined the effect of vapor lock on canal debridement efficacy by testing the null hypothesis that there is no difference between a “Closed” and an “Open” system design in smear layer and debris removal using a side-vented needle for irrigant delivery. Methods Roots in the “Closed System” were sealed with hot glue and embedded in polyvinylsiloxane to restrict fluid flow through the apical foramen during cleaning and shaping. For the “Open System”, the apical foramen was enlarged and connected to the external environment via a channel within the polyvinylsiloxane to permit unrestricted fluid flow. Smear and debris scores were evaluated using SEM and analyzed using Cochran-Mantel-Haenszel statistic. Results No difference in smear scores was detected between the two systems at all canal levels. Significant differences in debris scores between the two systems were found at each canal level: coronal (p<0.001), middle (p<0 .001) and apical (p<0.001). Conclusion The null hypothesis was rejected; presence of an apical vapor lock effect adversely affects debridement efficacy. Thus, studies with unspecified or questionable mechanisms to restrict fluid flow through the apical foramen have to be interpreted with caution.

Aim-To compare canal and isthmus debris debridement efficacies of the manual dynamic irrigation (MDI) and apical negative pressure (ANP) techniques in the mesial root of mandibular first molars with narrow isthmi, using a closed canal design.Methodology-Micro-computed tomography was employed to select 20 teeth, each containing a narrow isthmus. Each root was sealed at the apex with hot glue and embedded in polyvinylsiloxane to simulate a closed canal system. The teeth were submitted to a standardised instrumentation protocol. Final irrigation was performed with either the MDI or the ANP technique using the EndoVac system (N=10). Masson trichrome-stained sections were prepared from completely demineralised roots at ten canal levels between 1-2.8 mm of the anatomical apices. Areas occupied by canals and isthmus of each root and debris in the corresponding regions were digitised by the NIH Image J software and statistically analysed using two-way repeated measures ANOVA.Results-For the instrumented canals, there were no differences between the two groups (p=0.131) in the area occupied by debris at all canal levels (p=0.343). Conversely, for the isthmus, less debris was found in the ANP group (p<0.001) but no differences were seen in each group with respect to the ten canal levels (p=0.352).Conclusion-Neither technique produce completely removed debris from the isthmus regions. However the EndoVac system, which encompasses the ANP concept, removed considerably more debris from narrow isthmi of the mandibular mesial roots.

The null hypothesis was rejected; the presence of a sealed apical foramen adversely affected debridement efficacy when using manual dynamic agitation but not the EndoVac. Apical negative pressure irrigation is an effective method to overcome the fluid dynamics challenges inherent in closed canal systems.

Introduction MTA Plus (MTAP; Avalon Biomed Inc., Bradenton, FL) is a new calcium silicate cement with unknown cytotoxicity characteristics. The objectives of this study were to examine the effect of MTA Plus on the viability, apoptosis/necrosis profile and oxidative stress levels of rat odontoblast-like cells. Methods MDPC-23 cells were exposed to gray and white MTA Plus (GMTAP, WMTAP), gray and white ProRoot® MTA (GMTA, WMTA; Dentsply Tulsa Dental Specialties, Tulsa, OK) cements or their eluents. The cells were evaluated for: i) cell viability using XTT assay, ii) apoptosis/necrosis using flow cytometry and confocal laser scanning microscopy, and iii) oxidative stress by measuring reactive oxygen species. Results XTT assay showed that all test cements exhibited marked initial cytotoxicity that decreased with time. By the end of the third week, GMTAP and GMTA were comparable to untreated cells (negative control) in terms of cell viability, while WMTAP and WMTP were significantly lower than the untreated cells. Apoptosis/necrosis profiles of cells exposed to WMTAP and GMTAP were not significantly different from untreated cells, while cells exposed to WMTA and GMTA showed significantly less viable cells. All experimental groups exhibited reduction of intracellular ROS formation compared to untreated cells, although cells exposed to WMTA was not significantly different from untreated cells. Conclusions Both the gray and white versions of MTA Plus possess negligible in-vitro cytotoxic risks that are time and dilution dependent. They enrich the spectrum of hydraulic calcium silicate cements currently available to clinicians for endodontic applications.

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