Abstract: This study investigated the effectiveness of XP-Endo Finisher (XPF) associated with XP-Endo Shaper (XPS) or Reciproc Blue (RB) files in reducing bacterial load in oval-shaped root canals (RC) during chemomechanical preparation (CMP) using 0.9% saline solution (NaCl) or 2.5% sodium hypochlorite (NaOCl). Eighty mandibular incisors with single oval-shaped RC were contaminated with Enterococcus faecalis. The teeth were randomly assigned to eight experimental groups (n = 10) according to the CMP, as follows: G1: XPS, G2: XPS + XPF, G3: RB, and G4: RB + XPF. CMP was performed with NaCl or NaOCl. The reduction of bacterial load was assessed by colony-forming unit count before (S1) and after (S2) CMP. Data normality was verified by using Shapiro-Wilk test. ANOVA, Tukey's test, and Bonferroni post-hoc test were used at a 5% significance level. Culturable bacteria were present in all S1 samples (p>0.05). All instrumentation techniques were effective in reducing bacterial load, irrespective of the irrigating solution (p < 0.05). With the use of NaCl, RB was more effective than XPS (p = 0.035). With the use of NaOCl, XPS and RB presented similar effectiveness (p = 0.779). XPF enhanced the bacterial reduction of both systems tested (p < 0.05). The use of NaOCl improved the CMP, irrespective of the instrumentation technique used (p < 0.05). In conclusion, XPS and RB files are effective in reducing bacterial levels in oval-shaped RC. The use of XPF as a method of agitation of the irrigating solution improved the cleaning efficiency of both file systems tested. Mechanical preparation performed with saline solution decreased culturable bacteria from the root canal, but antimicrobial substances such as NaOCl should be used to achieve a significantly better disinfection.

Resumo O objetivo do presente estudo foi avaliar os efeitos citotóxicos de cinco cimentos endodônticos (AH Plus, Endomethasone N, EndoSequence BC, MTA Fillapex e Pulp Canal Sealer EWT) utilizando um modelo de cultura celular tridimensional (3D). Utilizou-se um modelo convencional de cultura de células bidimensionais (2D) como técnica de referência para comparação. Os fibroblastos Balb/c 3T3 foram cultivados em culturas de células bidimensionais convencionais e em modelos de cultura de células tridimensionais de colagéno de cauda de rato do tipo I. Em seguida, ambas as culturas de células foram incubadas com eluções dos cimentos endodônticos recém manipulados, durante 24 h. A viabilidade celular foi medida pelo ensaio de MTT. Os dados foram analisados estatisticamente utilizando ANOVA e o teste de Tukey com nível de significância de p<0,05. Todos os cimentos testados exibiram efeitos citotóxicos. Contudo, o efeito citotóxico foi dependente do modelo de cultura e do cimento testado. Os cimentos apresentaram maior citotoxicidade no modelo 2D do que no modelo 3D (p<0,05). Em ambas as condições, a EndoSequence BC apresentou a menor citotoxicidade (p<0,05). MTA Fillapex foi mais citotóxico do que os outros cimentos endodônticos testados (p<0,05), com exceção do AH Plus no modelo de cultura de células 2D (p>0,05). Endomethasone N e EWT mostraram efeitos citotóxicos mais baixos do que AH Plus no modelo de cultura de células 2D (p<0,05); entretanto, não houve diferenças estatísticas entre esses cimentos no modelo de cultura de células 3D. Pode concluir-se que a citotoxicidade foi maior na cultura de células 2D em comparação com a cultura de células 3D. EndoSequence BC selante exibiu a maior citocompatibilidade e MTA Fillapex a menor citocompatibilidade.

Abstract The aim of the present study was to evaluate the cytotoxic effects of five endodontic sealers (AH Plus, Endomethasone N, EndoSequence BC, MTA Fillapex and Pulp Canal Sealer EWT) using a three-dimensional (3D) cell culture model. A conventional bi-dimensional (2D) cell culture model was used as reference technique for comparison. Balb/c 3T3 fibroblasts were cultured in conventional bi-dimensional cell culture and in rat-tail collagen type I three-dimensional cell culture models. Then, both cell cultures were incubated with elutes of freshly mixed endodontic sealers for 24 h. Cell viability was measured by the methyl-thiazol-diphenyltetrazolium assay (MTT). Data were statistically analyzed using ANOVA and the Tukey test at a significance level of p<0.05. All tested sealers exhibited cytotoxic effects; however, cytotoxic effect was culture model- and sealer-dependent. Sealers showed higher cytotoxicity in 2D than in 3D cell culture model (p<0.05). In both conditions, EndoSequence BC showed the lowest cytotoxicity (p<0.05). MTA Fillapex was much more cytotoxic than the other tested endodontic sealers (p<0.05), with the exception of AH Plus in the 2D cell culture model (p>0.05). Endomethasone N and Pulp Canal Sealer EWT showed lower cytotoxic effects than AH Plus in 2D cell culture model (p<0.05); however no statistical differences was observed among these sealers in 3D cell culture model. It may be concluded that cytotoxicity was higher in 2D cell culture compared to 3D cell culture. EndoSequence BC sealer exhibited the highest cytocompatibility and MTA Fillapex the lowest cytocompatibility.