Resumo Este estudo correlacionou a resistência de união (RU) e a penetração de cimentos de diferentes bases à dentina radicular por meio do teste push-out e da análise por microscopia Confocal a laser (MCL). Quarenta e cinco canais radiculares foram preparados pela técnica coroa-ápice e obturados com guta-percha associada aos seguintes cimentos (n=15): Endofill, AH Plus e MTA Fillapex. Para análise por MCL da penetração dos cimentos, cinco canais foram obturados com os cimentos manipulados com Rodamina B a 0,1%. Em seguida, os espécimes foram seccionados transversalmente e submetidos ao teste de push-out (n=10) e análise por MCL (n=5). Os dados da RU apresentaram as seguintes médias (MPa) e desvio padrão: AH Plus (4,17±1,86); MTA Fillapex (3,13±1,96) e Endofill (2,10±1,03). A análise estatística (two-way ANOVA, α=0,05) mostrou diferença significativa entre os cimentos (p<0,001) e as regiões do canal radicular (p<0,001). Os resultados de RU de Endofill e MTA Fillapex foram estatisticamente semelhantes (p>0,05), no entanto, foram estatisticamente diferentes de AH Plus (p<0,001). A análise regional da RU demonstrou semelhança entre as regiões média e apical (p>0,05), e ambas foram diferentes da região cervical (p<0,001). A análise por MCL verificou a formação de tags em todos os grupos, com maior penetração nos espécimes obturados com AH Plus (p<0,05). O teste de Kendall (correlação entre RU à dentina e profundidade de penetração dos cimentos na dentina) e o teste de Pearson (correlação entre o padrão de falha e a profundidade de penetração dos cimentos na dentina) não evidenciaram correlação significativa entre as variáveis avaliadas nos cimentos testados (p<0,05). O grupo AH Plus apresentou maior RU, e formação de tags mais profundos que os outros cimentos. Não houve correlação significativa entre RU e penetração intratubular dos cimentos testados.

Abstract This study correlated the bond strength (BS) and dentin penetration of different sealers by push-out test and Confocal Laser Scanning Microscopy (CLSM) analysis. Forty-five root canals were prepared according to the crown-down technique and filled with gutta-percha associated to the following sealers (n=15): Endofill, AH Plus and MTA Fillapex. Five canals of each group were filled with the sealers added with 0.1% Rhodamine B dye. Next, the specimens were transversely sectioned and submitted to the push-out test (n=10) and CLSM analysis (n=5). The BS data showed the following means (MPa) and standard deviation: AH Plus (4.17±1.86); MTA Fillapex (3.13±1.96) and Endofill (2.10±1.03). Statistical analysis (two-way ANOVA, α=0.05) showed significant difference among sealers (p<0.001) and root canal thirds (p<0.001). The BS results of Endofill and MTA Fillapex were statistically similar (p>0.05), however, they were statistically different from AH Plus (p<0.001). The regional analysis of BS showed similarity between middle and apical thirds (p>0.05), and both were different from coronal portion (p<0.001). CLSM analysis verified tags formation in all groups and higher penetration of the specimens filled with AH Plus (p<0.05). The Kendall test (correlation between BS to dentin and sealer penetration into dentinal tubules) and the Pearson test (between failures pattern and sealer penetration into dentinal tubules) did not show correlation between the variables evaluated for all the tested sealers (p>0.05). AH Plus group had higher BS to dentin, and deeper tags formation than the other sealers. There was no significant correlation between BS and intratubular penetration of the tested sealers.

Resumo O objetivo desse estudo foi avaliar o efeito da irrigação intracanal com hipoclorito de sódio (NaOCl) e ácido etilenodiamino tetracético (EDTA) previamente à medicação de hidróxido de cálcio na resistência à compressão da dentina radicular. Quarenta e oito raízes com canais únicos e retos tiveram os canais instrumentados pela técnica coroa-ápice com limas Flexofile e brocas Gates Glidden sob irrigação com solução salina (NaCl) a 0,9%. Os canais radiculares foram separados em 4 grupos (n=12), de acordo com a solução irrigadora: Grupo Controle, NaCl 0,9%; GrupoNaOCl, NaOCl 1%; GrupoEDTA, EDTA 17%; e GrupoEDTA+NaOCl, NaOCl 1% e EDTA 17%. As soluções permaneceram por 40 min, sendo renovadas a cada 10 min, exceto para o GrupoEDTA+NaOCl, onde as soluções foram alternadas a cada 10 min. Os canais foram secos, preenchidos com pasta de hidróxido de cálcio e radiografados. Cada canal foi selado e mantido a 37 °C por 30 dias. Após esse período, as raízes foram cortadas 1 mm abaixo da junção cemento-esmalte e 6 mm apicalmente a este corte, a fim de obter cilindros de 6 mm de comprimento. O teste de compressão foi realizado com velocidade de cruzeta de 1 mm/min. As médias (±SD) da resistência à compressão em MPa foram: Grupo Controle, 151.23±94.36; GrupoNaOCl, 167.50±57.25; GrupoEDTA, 108.79±99.88; GrupoEDTA+NaOCl, 60.12±92.10. Diferenças estatisticamente significativas foram encontradas entre os grupos (ANOVA e Tukey; a=0,05; p=0,02). O Grupo Controle e o GrupoNaOCl obtiveram maiores médias de resistência à compressão em relação ao GrupoEDTA+NaOCl. A irrigação intracanal com EDTA 17% e NaOCl 1% promoveu redução significativa da resistência à compressão da dentina, após 30 dias de medicação intracanal com hidróxido de cálcio.

Abstract The aim of this study was to assess the effects of intracanal irrigation with sodium hypochlorite (NaOCl) and ethylenediaminetetracetic acid (EDTA) prior to calcium hydroxide medication on the compressive strength of root dentin. Forty-eight roots with single and straight canals were instrumented with a crown-down technique using Flexofile files and Gates Glidden burs, under 0.9% sodium chloride (NaCl) irrigation. Root canals were randomly separated into 4 groups (n=12), according to the irrigating solution: Control Group, 0.9% NaCl; GroupNaOCl, 1% NaOCl; GroupEDTA, 17% EDTA; and GroupEDTA+NaOCl, 17% EDTA and 1% NaOCl. Solutions remained for 40 min, renewed every 10 min, except for GroupEDTA+NaOCl, where the solutions were alternated every 10 min. Canals were dried and filled with calcium hydroxide paste, and radiographed. Each canal was sealed and stored at 37 °C for 30 days. After this period, the roots were cut 1 mm below the cementoenamel junction and 6 mm apically from this point in order to obtain 6 mm-long cylinders. The compressive test was conducted with a crosshead speed of 1 mm/min. The means (±SD) (MPa) of compressive strength were: Control Group, 151.23±94.36; GroupNaOCl, 167.50±57.25; GroupEDTA, 108.79±99.88; GroupEDTA+NaOCl, 60.12±92.10. Significant statistical differences among groups were found (ANOVA and Tukey, a=5%, p=0.02). Control Group and GroupNaOCl showed higher means of compressive strength than GroupEDTA+NaOCl. Intracanal irrigation with 17% EDTA and 1% NaOCl produced a significant reduction of dentin compressive strength 30 days after medication with calcium hydroxide.

The use of an adequate method for evaluation of the adhesion of root canal filling materials provides more reliable results to allow comparison of the materials and substantiate their clinical choice. The aims of this study were to compare the shear bond strength (SBS) test and push-out test for evaluation of the adhesion of an epoxy-based endodontic sealer (AH Plus) to dentin and gutta-percha, and to assess the failure modes on the debonded surfaces by means of scanning electron microscopy (SEM). Three groups were established (n=7): in group 1, root cylinders obtained from human canines were embedded in acrylic resin and had their canals prepared and filled with sealer; in group 2, longitudinal sections of dentin cylinders were embedded in resin with the canal surface smoothed and turned upwards; in group 3, gutta-percha cylinders were embedded in resin. Polyethylene tubes filled with sealer were positioned on the polished surface of the specimens (groups 2 and 3). The push-out test (group 1) and the SBS test (groups 2 and 3) were performed in an Instron universal testing machine running at crosshead speed of 1 mm/min. Means (±SD) in MPa were: G1 (8.8±1.13), G2 (5.9±1.05) and G3 (3.8±0.55). Statistical analysis by ANOVA and Student's t-test (a=0.05) revealed statistically significant differences (p<0.01) among the groups. SEM analysis showed a predominance of adhesive and mixed failures of AH Plus sealer. The tested surface affected significantly the results with the sealer reaching higher bond strength to dentin than to gutta-percha with the SBS test. The comparison of the employed methodologies showed that the SBS test produced significantly lower bond strength values than the push-out test, was skilful in determining the adhesion of AH Plus sealer to dentin and gutta-percha, and required specimens that could be easily prepared for SEM, presenting as a viable alternative for further experiments.