RESUMO
AIM: To evaluate the viability of the electrochemical dissolution of fragments of fractured NiTi instruments in root canals of extracted human maxillary molars, using two electrodes and the solution restricted to a small reservoir coupled to the pulp chamber. The primary hypothesis was that this method enables the reduction of fragment volume and re-establishment of the root canal path with a size 08 K-file, both in simulated canals and in extracted human maxillary molars. METHODOLOGY: Fragments of F1 ProTaper instruments were polarized in simulated root canals and in distobuccal root canals of extracted maxillary molars using a new method, with the solution restricted to a small acrylic microcell coupled to each resin block or pulp chamber. Two electrodes were used, where one was kept in contact with the intracanal fragment and another was positioned in the solution present in the acrylic microcell. After the tests, a size 08 K-file was used passively to verify the possibility of bypassing the fragment, which was also confirmed by radiographic analysis. Micro-CT analysis of the teeth was used before and after fragment dissolution to evaluate the volume, length and porosity of the fragments. The D'Agostino-Pearson normality test was used to verify the distribution of the data. A paired t-test (P < 0.05) was used to compare the volume, length and porosity of the fragments before and after the dissolution tests. RESULTS: After dissolution, all fragments could be bypassed with a size 08 K-file in both simulated canals and in extracted teeth. The dissolution process did not result in significant reduction of neither the fragment length nor the fragment porosity. However, it resulted in a significant reduction of fragment volume (paired t-test, P < 0.05). CONCLUSION: The electrochemical dissolution of fragments of NiTi files in root canals of extracted human maxillary molars using two electrodes, and the solution restricted to a small reservoir coupled to the pulp chamber resulted in a significant reduction of fragment volume. The re-establishment of the root canal path with the passive insertion of size 08 K-files was possible in all samples after the tests, both in simulated canals and in extracted teeth.
Assuntos
Cavidade Pulpar , Níquel , Ligas Dentárias , Eletrólitos , Humanos , Dente Molar/diagnóstico por imagem , Preparo de Canal Radicular , Solubilidade , TitânioRESUMO
AIM: To evaluate the effects of the [NaF 12 g L-1 + NaCl 1 g L-1 ] solution used in the electrochemical dissolution process of fractured endodontic files, as well as its NiTi-containing product, on dentine hardness, topography and human fibroblast viability. METHODOLOGY: Sixty single-rooted human teeth were evaluated for dentine microhardness using the Vickers hardness test and the area and number of dentinal tubules by scanning electron microscopy. The samples were divided according to the dentine surface treatment: distilled water; 17% EDTA; [NaF 12 g L-1 + NaCl 1 g L-1 ]; and 17% EDTA + [NaF 12 g L-1 + NaCl 1 g L-1 ]. Thirty-six single-rooted human teeth were divided according to the irrigation protocol: Dulbecco's Modified Eagle's Medium + 10% foetal bovine serum; 5.25% NaOCl; [NaF 12 g L-1 + NaCl 1 g L-1 ]; and [NaF 12 g L-1 + NaCl 1 g L-1 + NiTi]. The extracts in contact with the apical foramen were used in the MTT assay to evaluate human fibroblast viability, with dilutions of 100%, 50%, 25% and 12.5%. Statistical tests used were paired t-tests, one-way anova, Tukey's test, Kruskal-Wallis test and Dunn's post-test. RESULTS: The [NaF 12 g L-1 + NaCl 1 g L-1 ] solution did not modify dentine microhardness or the average dentinal tubule area. However, EDTA induced changes in dentine structure and microhardness (P < 0.05). The [NaF 12 g L-1 + NaCl 1 g L-1 ] solution, and its NiTi-containing product had lower cytotoxicity than NaOCl at dilutions of 25% and 50% (P < 0.01). CONCLUSIONS: The [NaF 12 g L-1 + NaCl 1 g L-1 ] solution did not alter dentine microhardness or damage the dentine structure. It also demonstrated lower cytotoxicity than NaOCl.
Assuntos
Dentina/efeitos dos fármacos , Dentina/patologia , Técnicas Eletroquímicas , Níquel/toxicidade , Preparo de Canal Radicular/instrumentação , Titânio/toxicidade , Adolescente , Técnicas de Cultura de Células , Linhagem Celular , Sobrevivência Celular/efeitos dos fármacos , Criança , Pré-Escolar , Eletrólise , Falha de Equipamento , Fibroblastos/efeitos dos fármacos , Dureza , Humanos , Lactente , Microscopia Eletrônica de Varredura , Níquel/química , Pele , Cloreto de Sódio/farmacologia , Fluoreto de Sódio/farmacologia , Hipoclorito de Sódio/farmacologia , Solubilidade , Fatores de Tempo , Titânio/químicaRESUMO
The purpose of this study was to investigate whether the Electrochemical Dissolution (DE) facilitates the retrieval of fractured files, from Endo-Training block with an artificial root canal, by using ultrasonic techniques (US). Twenty Endo-Training block with an artificial single canal with working length 16 mm and twenty nickel-titanium (NiTi) Protaper Universal rotary files were used. 10 Shaping S1 files and 10 Shaping S2 files, were sectioned transversally within the conduit, to 5mm of the apical tip. Twenty samples were divided into four groups: Group1 and 3 received the action of DE and US, and groups 2 and 4 received the action of US. To remove the fragments we used Staging Platform and Dental Microscope. Outcome was analyzed statistically by Student t test. Statistical Analysis showed a significant difference in retrieval time of the fragments and weight loss mass of Endo training block ultrasonic tips were used, between groups that applied Ultrasonic with electrochemical dissolution and the group using only ultrasonic. It can be concluded that there was weight loss mass of separated fragment by electrochemical action, however, it was not sufficient and its use alone was inconclusive to retrieve the fragments. The procedure needs to be complemented with the use of the staging platform, ultrasonic tips and Dental Microscope.
Este estudio tiene como propósito determinar si la Disolución Electroquímica (DE) favorece el retiro de fragmentos de limas fracturadas, insertos en bloc endodónticos de entrenamiento de resina, con un conducto radicular simulado, mediante el uso de ultrasonido (US). Se utilizaron 20 bloc y 20 limas rotatorias usadas ProTaper Universal de NiTi Shaping Files, 10 S1, 10 S2, que fueron fracturadas dentro del conducto, a 5 mm desde la punta apical y divididos en Grupo1 y 3 que recibieron la acción de la DE y US; y Grupo 2 y 4 sólo utilizó US. Para retirar los fragmentos se utilizó Plataforma de Trabajo y Microscopio Dental. Los datos fueron analizados con la prueba T de Student. Los resultados indican que existen diferencias estadísticamente significativas en el tiempo de retiro de los fragmentos y en la pérdida de masa del bloc de entrenamiento por el uso del ultrasonido, en los grupos que se aplicó Disolución Electroquímica más Ultrasonido. Se puede concluir que la acción electroquímica permite que exista pérdida de masa del fragmento fracturado, sin embargo, no es suficiente y su sola utilización no es concluyente para retirar los fragmentos, es necesario complementar el procedimiento con la utilización de la Plataforma de Trabajo, puntas de ultrasonido y el Microscopio Dental.