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OBJECTIVES: This study evaluated the effect of repeated uses and autoclaving in the instrumented area, fracture resistance, and time of instrumentation of thermally treated nickel-titanium reciprocating systems. MATERIALS AND METHODS: Two hundred simulated canals were instrumented using Reciproc Blue and WaveOne Gold. Each file was used up to 10 times or until fracture. The instrumented area was measured in pre- and post-operative images, using ImageJ software. Kaplan-Meier survival analysis evaluated the number of uses of instruments before fracture. Instrumented area and time of instrumentation were analyzed by Mann-Whitney U test and Kruskal-Wallis. Correlations among the number of uses and instrumented area were measured. The level of statistical significance was set at p < 0.05. RESULTS: Reciproc Blue presented a higher estimated number of uses in comparison with WaveOne Gold (p = 0.026), but autoclaving did not affect the resistance to fracture of instruments (p > 0.05). The instrumented area was different among the evaluated groups (p = 0.039), and the instrumented area along the uses of both tested instruments was reduced. With the time of instrumentation, there was also a significant difference among the evaluated groups; the groups without sterilization cycles were faster, in comparison to those submitted to autoclaving (p = 0.010). CONCLUSIONS: Reciproc Blue was more resistant than WaveOne Gold, suffering later fracture. Additionally, the sterilization cycles did not influence the estimated number of uses of thermally treated reciprocating instruments, but the instrumented area of root canals was reduced along with the repeated uses of both instruments.

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A fratura acidental de um instrumento durante o tratamento endodôntico pode ocorrer devido à falta de conhecimento anatômico do elemento dentário, ao uso de instrumentos inadequados ou à falha técnica do operador. O objetivo do presente estudo foi apresentar um relato de caso clínico da remoção de um instrumento fraturado no terço apical de um pré-molar superior. O fragmento localizava-se no terço apical da raiz vestibular. A primeira tentativa de remoção do fragmento foi realizada sem sucesso. Após 15 dias, em uma nova tentativa, o instrumento foi removido com o auxílio de ultrassom e inserto específico. Entre as sessões, utilizou-se medicação intracanal à base de hidróxido de cálcio, paramonoclorofenol canforado e propilenoglicol. Decorridos 15 dias, o dente mostrou-se assintomático e foi obturado pela técnica da condensação lateral. Assim, a paciente foi encaminhada para a realização da restauração definitiva. Após 3 meses, foi observada radiograficamente a regressão da lesão perirradicular. Conclui-se que a retirada do fragmento no caso descrito se mostrou uma opção eficiente, propiciando a manutenção do dente com ausência de sinais e sintomas.

Accidental fracture of an instrument during endodontic treatment can occur due to lack of dental anatomy knowledge, use of inadequate instruments or technical failure of the operator. The aim of the present study is to present a case report of instrument fragment removal from a superior premolar. The fragment was identified to be in the apical third of the buccal root. The first attempt to remove the instrument was made without success. After 15 days, in a new attempt, the instrument was removed with the aid of an ultrasonic endodontic tip. The intracanal medication between sessions was calcium hydroxide, camphorated paramonochlorophenol and propylene glycol. After more 15 days, the tooth was asymptomatic and was filled by lateral condensation. Thus, the patient was referred for definitive restoration. After 3 months, it was observed radiographically the regression of the periradicular lesion. In conclusion, the removal of the fragment proved to be an efficient option, providing the maintenance of the tooth with no signs and symptoms.

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INTRODUCTION: The objective of this in vitro study was to evaluate whether cervical preparation with Mtwo files in a crown-down technique influences instrumentation time and the cyclic fatigue resistance of these instruments. METHODS AND MATERIALS: Two instrumentation techniques were evaluated (manufacturer and crown-down). Each group consisted of 10 kits containing four Mtwo instruments (10/0.04, 15/0.05, 20/0.06, and 25/0.06), which were used to prepare three standard simulated curved resin canals. The mean instrumentation time and the corresponding number of cycles for each instrumentation (NCI) were recorded. The instruments were rotated at a constant speed of 300 rpm in a stainless-steel canal (diameter of 1.5 mm) at a 90° angle of curvature and 5-mm radius. The center of the curvature was 5 mm from the tip of the instrument. The cyclic fatigue resistance of the files was determined by counting the number of cycles to failure (NCF). Data were analyzed by the Mann-Whitney test. RESULTS: The mean instrumentation time and NCI of files 10/0.04 and 15/0.05 were significantly lower (P<0.05) when the crown-down technique was used compared to the manufacturer's method for the same tip size/taper file. There was no significant difference in the mean NCF between the two techniques. CONCLUSION: The crown-down technique did not interfere with resistance to cyclic fatigue. However, the shorter instrumentation time of files 10/0.04 and 15/0.05 could reduce the fracture risk in the case of reuse of these instruments.

RESUMO

INTRODUCTION: Reciprocating instruments were developed to improve and simplify the preparation of the root canal system by allowing greater centralization of the canal and requiring a shorter learning curve. Despite the risk of instrument separation, using a reciprocating instrument in more than 1 case is a relatively common clinical practice. The aim of this study was to evaluate the fracture resistance of Reciproc (R25; VDW, Munich, Germany) and WaveOne (Primary; Dentsply Maillefer, Ballaigues, Switzerland) instruments according to the number of uses during the preparation of root canals in up to 3 posterior teeth. METHODS: A prospective clinical study was conducted by 3 experienced specialists who performed treatment of 358 posterior teeth (1130 canals) over a period of 12 months using 120 reciprocating instruments, 60 of which were Reciproc R25 and 60 were WaveOne Primary. The motion used during instrumentation followed the recommendations of the respective manufacturers. After each use, the instruments were observed under a dental operating microscope at 8× magnification. In the case of fracture or deformation, the instrument was discarded. RESULTS: None of the instruments showed any signs of deformation, but 3 instruments fractured (0.26% of the number of canals and 0.84% of the number of teeth). All fractures occurred in mandibular molars (1 WaveOne Primary file during the third use and 2 Reciproc R25 files, 1 during the first use and the other during the third use). CONCLUSIONS: There was a low incidence of fracture when reciprocating files were used in up to 3 cases of endodontic treatment in posterior teeth.

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This case report describes root canal filling performed over a large S1 ProTaper file fragment in a second mandibular molar with irreversible pulpitis. An S1 ProTaper file was fractured during the instrumentation of the mesiobuccal canal. Approximately 10 mm of file fragment remained in the apical and middle thirds of the canal. The obturation was performed over this fragment using thermomechanically compacted gutta-percha and sealer. Radiographic findings and the absence of clinical signs and symptoms at 3-year follow up indicated successful treatment. Cone-beam computed tomography images revealed absence of periapical lesion and details of intracanal file fragment related to root fillings and apex morphology. In this case, the presence of a large intracanal fractured instrument did not have a negative impact on the endodontic prognosis during the follow up evaluation period.

Este relato de caso descreve a obturação do canal radicular realizada sobre um grande fragmento da lima ProTaper S1 em um segundo molar inferior com pulpite irreversível. Uma lima ProTaper S1 fraturou durante a instrumentação do canal mésio-vestibular. Aproximadamente 10 mm de remanescente do fragmento da lima permaneceu nos terços apical e médio do canal. A obturação foi realizada sobre este fragmento usando guta-percha compactada termomecanicamente e cimento endodôntico. Achados radiográficos e ausência de sinais e sintomas clínicos após 3 anos de acompanhamento indicaram o sucesso do tratamento. Imagens de tomografia computadorizada de feixes cônicos revelaram a ausência de lesão periapical e detalhes do fragmento da lima intracanal relacionados à obturação do canal radicular e à morfologia do ápice. Neste caso, a presença de grande instrumento fraturado intracanal não teve impacto negativo no prognóstico endodôntico durante o período de acompanhamento.

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El propósito de este estudio fue comparar la capacidad de sellado de tres técnicas de obturación con gutapercha termoplastificada, técnica de obturación vertical de Schilder, compactación termomecánica y Thermafil (Dentsply-Maillefer), en dientes con instrumentos fracturados en la región apical. Un total de 30 dientes unirradiculares extraídos fueron instrumentados con ProTaper (Dentsply-Maillefer), en cada uno de los mismos se fracturaron intencionalmente instrumentos rotatorios ProTaper F3 en el tercio apical. Los dientes fueron divididos aleatoriamente en tres grupos (n = 10) para ser obturados con la técnica correspondiente, para que, con la técnica de filtración de colorante y con la ayuda de la aclaración de los dientes fueran observados bajo microscopio para determinar la cantidad de microfiltración apical que permitía cada técnica. En todos los grupos, los especímenes presentaron alguna cantidad de microfiltración apical. Los dientes que fueron obturados con Thermafil presentaron una microfiltración promedio de 3,134 μm, resultando en significativamente mayor microfiltración que los obturados con la técnica termomecánica de McSpadden y de compactación vertical de Schilder, (p < 0.05) que obtuvieron un promedio de microfiltración de 1,934 μm y 2,083 μm respectivamente. Mientras que no existe diferencia estadísticamente significativa de microfiltración entre la técnica de McSpadden y la de Schilder (p > 0.05).

The purpose of the present study was to compare the sealing ability of three warm obturation techniques (thermo-plasticized gutta-percha): Schilders warm vertical compaction, McSpadden's thermo-mechanical compaction and Thermafil (Dentsply-Maillefer) in teeth fractured at the apical region. 30 extracted, single-rooted teeth were prepared with Pro-Taper (Dentsply-Maillefer). At the apical third of each of these teeth, ProTaper F3 rotary instruments were deliberately fractured. Teeth were randomly divided into three groups (n = 10) to be later filled with the selected technique, so that with dye penetration technique and with the aid of discoloring teeth technique, teeth could be microscopically assessed so as to determine the amount of apical microfiltration elicited in every technique. In all groups, specimens presented some degree of apical microfiltration. Teeth filled with Thermafil presented 3,134 µm average microfiltration. This microfiltration was significantly higher than the one observed with McSpadden thermo-mechanical technique and Schilder's vertical compaction technique (p < 0.05). These two techniques presented 1,934 µm and 2,083 µm respectively. McSpadden and Schilder's technique show no statistically significant microfiltration differences (p > 0.05).