Effect of autoclave sterilisation and heat activated sodium hypochlorite irrigation on the performance of nickel-titanium rotary files against cyclic fatigue

The present study aims to assess the impact of heat-activated sodium hypochlorite (NaOCl) and/or autoclave sterilisation on the cyclic fatigue resistance (CFR) of heat-treated nickel-titanium rotary files used in root canal treatment. The CFR of One Curve (OC) files was evaluated under the following conditions: as received (Group 1; control), immersion in NaOCl at 23 ± 1ºC (Group 2), immersion in NaOCl at 60 ± 1ºC (Group 3), autoclave sterilisation at 135 1ºC (Group 4), combined treatment of autoclave sterilisation and immersion in NaOCl at 23 ± 1ºC (Group 5), and combined treatment of autoclave sterilisation and immersion in NaOCl at 60 ± 1ºC (Group 6). A simulated root canal in a zirconia block was utilised to test the performance of the files. All the types of treatments resulted in significant reductions in fracture resistance of the OC files. Immersion of the files in NaOCl at 23ºC revealed the smallest reduction, while combined treatment of autoclaving and immersion in NaOCl at 60ºC caused the greatest reduction. Autoclave sterilisation or exposure of OC files to 2.5% NaOCl adversely affect the cyclic fatigue life and increasing solution temperature or combined treatment caused additionally significant reduction in CFR

In vivo evaluation of the sealing ability of two endodontic sealers in root canals exposed to the oral environment for 45 and 90 days Avaliação, in vivo, da capacidade de selamento de dois cimentos endodônticos em canais radiculares expostos ao meio bucal por 45 e 90 dias

This in vivo study evaluated the sealing ability of a resin-based sealer (AH Plus) and a zinc oxide-eugenol sealer (Endofill) in dogs' teeth, exposed to the oral environment for 45 and 90 days. Forty eight lower incisors from 8 dogs were endodonticaly treated. A stratified randomization determined the sealer use in each root canal. All canals were filled using the lateral condensation technique. The excess filling material at the cervical portion of the root canal was sectioned, leaving a 10-mm obturation length inside the canal. Teeth were provisionally sealed with glass ionomer cement for 24 h and the canals were exposed to the oral environment for either 45 or 90 days. Therefore, the experimental groups were as follows: A45- AH Plus for 45 days; A90- AH Plus for 90 days; E45- Endofill for 45 days; and E90- Endofill for 90 days (n=12). After the experimental period, the dogs were killed and the lower jaw was removed. The incisors were extracted and the roots were covered with two coats of nail varnish. The teeth were immersed in India ink for 96 h and submitted to diaphanization. Dye leakage (in mm) was measured using stereomicroscopy (10x magnification). The results were statistically analyzed using two-way ANOVA and Tukey test for multiple comparisons (á = 0.05). Group E90 (2.03&plusmn;0.94) showed significantly higher mean leakage value than all other groups (p<0.001). None of the sealers, in both study conditions, were able to prevent dye leakage.<br>Este estudo in vivo avaliou a capacidade de selamento de um cimento endodôntico resinoso (AH Plus) e um a base de óxido de zinco eugenol (Endofill), em dentes de cães, expostos ao meio bucal, por 45 e 90 dias. Foi realizado o tratamento endodôntico de 48 incisivos inferiores de 8 cães. Uma randomização estratificada determinou o tipo de cimento a ser usado em cada canal que foram tratados pela técnica de condensação lateral. Após a obturação, o excesso de material obturador, na porção cervical do canal radicular foi seccionado, restando o comprimento de 10 mm no interior do canal radicular. Os dentes foram selados, provisoriamente, com cimento de ionômero de vidro por 24 h. A seguir, o selamento coronário foi removido e os canais ficaram expostos ao meio bucal. Desta forma, delineou-se os seguintes grupos experimentais: A45- AH Plus por 45 dias; A90- AH Plus por 90 dias; E45- Endofill por 45 dias; e E90- Endofill por 90 dias (n=12). Passado o período experimental, os cães foram mortos e as mandíbulas removidas. Realizou-se a exodontia dos incisivos e as suas raízes foram impermeabilizadas com duas camadas de esmalte para unhas. Os dentes foram imersos em tinta nanquim por 96 h. Após realizou-se a diafanização dos espécimes e a infiltração de corante foi medida (em mm) com auxílio de uma lupa esteroscópica, em aumento de 10x. Os resultados foram analisados estatisticamente através da Análise de Variância de dois fatores e Teste de Comparações Múltiplas de Tukey (á = 0.05). O grupo E90 (2.03&plusmn;0.94) apresentou uma infiltração média significativamente maior do que a ocorrida nos demais grupos (p<0.001). Os cimentos avaliados, nos dois períodos experimentais, não foram capazes de impedir a infiltração de corante