Influência do pré-alargamento coronário na resistência à fadiga cíclica de instrumentos reciprocantes tratados termicamente / Influence of coronal pre-enlargement on cyclic fatigue resistance of heat-treated reciprocating instruments

Objetivo: O objetivo do presente estudo foi avaliar a influência do pré-alargamento coronário na resistência à fadiga cíclica de dois instrumentos reciprocantes tratados termicamente. Métodos: 20 instrumentos Reciproc Blue (R25 Blue) e 20 instrumentos X1 Blue (X1) foram utilizados para instrumentar blocos de resina simulando um molar superior com três canais radiculares. Os dentes foram divididos em quatro grupos (n=10), de acordo com o instrumento e com a técnica de instrumentação utilizada: grupos R25 e X1 - instrumentação com R25 Blue (25/0.08) ou X1 Blue (25/0.06), respectivamente, sem alargamento prévio; e grupos R25 ou X1 + pré-alargamento cervical - pré-alargamento com os instrumentos ProTaper Universal SX e S1 antes da instrumentação com R25 Blue ou X1. Os instrumentos foram testados com relação à fadiga cíclica utilizando-se um canal simulado de aço inoxidável com ângulo de curvatura de 86 graus e raio de curvatura de 6 mm. Os instrumentos foram acionados utilizando-se o movimento "RECIPROC ALL" do motor endodôntico (VDW) e o tempo de instrumentação até a fratura do instrumento foi contabilizado. Os resultados foram analisados pelo teste t de Student (p<0,05). Resultados: Os instrumentos X1 apresentaram maior resistência à fadiga cíclica do que R25 Blue em ambas as condições testadas (p<0,05). Não houve diferença entre os grupos com e sem pré-alargamento coronário para os instrumentos R25 Blue e X1 (p>0,05). Conclusão: O instrumento X1 Blue apresentou maior resistência à fadiga cíclica do que o Reciproc Blue. O pré-alargamento coronário não foi capaz de aumentar a resistência à fratura por fadiga cíclica dos instrumentos testados (AU).

Objective: The aim of this study was to evaluate the influence of cervical pre-flaring on the cyclic fatigue resistance of two heat-treated reciprocating instruments. Methods: 20 Reciproc Blue (R25 Blue) instruments e 20 X1 Blue File (X1) were used to instrument resin blocks simulating an upper molar with 3 root canals. The specimens were divided into four groups (n=10) according the instrument and type of instrumentation used: R25 and X1 groups: root canal preparation with R25 Blue (25/0.08) ou X1 Blue (25/0.06), without cervical pre-flaring; R25 or X1 + cervical pre-flaring- pre-flaring with ProTaper Universal SX e S1 before instrumentation with R25 Blue or X1 blue. After instrumentation the instruments were tested for cyclic fatigue using a simulated stainless steel root canal with 86 degree bending angle and 6 mm bending radius. The instruments were triggered using the "RECIPROC ALL" motion of a reciprocating endodontic motor (VDW) and the instrumentation time until instrument fracture was accounted. Results were analyzed by Students t-test (p<0.05). Results: Statistical analysis showed that the X1 Blue showed higher resistance to cyclic fatigue than the R25 Blue under both conditions tested (p<0.05). There were no differences between the groups with and without coronary pre-flaring for the R25 Blue and X1 Blue (p<0.05). Conclusion: X1 Blue showed higher resistance to cyclic fatigue than the R25 Blue. The cervical pre-flaring did not increased the resistance to cyclic fatigue fracture of the tested instruments (AU)

Effects of clinical use of NiTi reciprocating instruments on cyclic and torsional resistance, and on roughness

Abstrac The aim of the present study was to evaluate the cyclic fatigue, torsional resistance and surface roughness of Reciproc R25 instruments in four different situations, namely as new instruments and as instruments tested after clinical preparation of one, two or three maxillary molars with four root canals. The total time required to perform each root canal preparation was recorded. Cyclic fatigue resistance was determined by the time to fracture using a customized testing device (n = 10 per group). The torsional test evaluated the torque and angle of rotation to failure according to ISO 3630-1 (n = 10 per group). The roughness of the working parts of new and used instruments was evaluated with a profilometer (n = 5 per group). Statistical analysis was performed using one-way ANOVA and Tukey's test. The level of significance was set at 5%. No fractures or deformations were observed after clinical use. Higher preparation time was needed during the third use of the instruments for all root canals (p < 0.05). There were no significant differences among the groups in regard to either cyclic fatigue or torsional resistance (p > 0.05). Regarding the roughness measurements, groove depth was higher on new and one- versus two- or three-maxillary-molar-prepared instruments (p < 0.05). It can be concluded that the clinical use of Reciproc instruments increased preparation time and decreased surface roughness. However, clinical use did not affect the cyclic fatigue or torsional resistance of the Reciproc instruments.

Fadiga cíclica e resistência torcional de instrumentos reciprocantes tratados termicamente tipo Gold / Cyclic fatigue and torsional resistance of Gold-type thermally treated reciprocating instruments

Objetivo: o objetivo do presente estudo foi avaliar a fadiga cíclica e torcional dos instrumentos WA1 e WaveOne Gold. Métodos: vinte instrumentos do sistema WA1 (25/0,07v) e vinte instrumentos do sistema WaveOne Gold (25/0,07v) foram utilizados. A resistência à fadiga cíclica foi testada, medindo o tempo até a fratura em um canal artificial curvo de aço inoxidável com ângulo de 80° e raio de curvatura de 3 mm (n = 10). O torque máximo e ângulo de rotação no momento da falha dos instrumentos (n = 10) foram medidos de acordo com a norma ISO 3630-1. A superfície de fratura de todos os fragmentos foi examinada com um microscópio eletrônico de varredura. Os resultados foram analisados estatisticamente usando o teste t de Student com um nível de significância de 5%. Resultados: não foram observadas diferenças na vida em fadiga cíclica dos instrumentos testados (p > 0,05). A força máxima de torção dos instrumentos WA1 foi menor do que os instrumentos WaveOne Gold (p < 0,05); entretanto, não foram observadas diferenças no ângulo máximo de rotação de ambos os sistemas (p > 0,05). A fotomicrografia eletrônica de varredura da superfície da fratura revelou características similares e típicas de fadiga cíclica e de falha por torção para os dois tipos de instrumentos. Conclusão: dentro dos resultados do presente estudo, pode-se concluir que os instrumentos WaveOne Gold e WA1 tiveram comportamento similar com relação à fadiga cíclica. No entanto, o instrumento WaveOne Gold apresentou maior deflexão angular à fratura por torção, em comparação aos instrumentos WA1 (AU).

Introduction: The aim of the present study was to evaluate the cyclic and torsional fatigue resistance of WA1 and WaveOne Gold instruments. Methods: Twenty instruments of the WA1 system (25/0.07v) and twenty instruments of the WaveOne Gold system (25/0.07v) were used. The cyclic fatigue resistance was tested by measuring the time to fracture in a stainless steel curved artificial canal with an angle of 80° and a radius of curvature of 3 mm (n = 10). The maximum torque and rotation angle at instrument failure (n = 10) were measured according to ISO 3630-1. The fracture surface of all the fragments was examined with a scanning electron microscope. The results were statistically analyzed using the student t-test with a significance level of 5%. Results: There were no differences in cyclic fatigue life of the tested instruments (P> 0.05). The maximum torsional force of the WA1 instruments was lower than the WaveOne Gold instruments (P <0.05); however, no differences were observed in the maximum rotation angle of both systems (P> 0.05). The scanning electron photomicrographs of the fracture surface revealed similar and typical characteristics of cyclic fatigue and torsional failure for the 2 types of instruments. Conclusion: Within the results of the present study, it can be concluded that WaveOne Gold and WA1 instruments had similar behavior regarding cyclic fatigue. However, WaveOne Gold instruments presented greater angular deflection to torsional fracture than WA1 instruments.

Os cistos radiculares poem curar após tratamento endodôntico / Radicular cysts may heal after endodontic treatment

A etiologia das lesões perirradiculares e suas diferentes manifestações clínicas já estão bastante esclarecidas, porém o tratamento dos cistos radiculares ainda é um assunto controverso na Odontologia. O objetivo deste trabalho é realizar uma análise crítica, baseada na literatura, sobre o tratamento de cistos radiculares, buscando evidências que demonstrem que os cistos radiculares podem ser eliminados após tratamento endodôntico. Os cistos podem ser divididos em: cistos em bolsa e cistos verdadeiros, sendo que os cistos em bolsa respondem ao tratamento endodôntico, enquanto os cistos verdadeiros somente podem ser tratados através da cirurgia perirradicular. Pode-se concluir que sendo o agente microbiano o responsável pelas lesões perirradiculares, a maioria destas lesões, incluindo os cistos, regridem após a intervenção endodôntica não cirúrgica.

The etiology of apical periodontitis and its different clinical manifestations are already well versed, but the treatment of radicular cysts is still a controversial subject in Dentistry. The e aim of this study is to perform a critical analysis based on literature regarding treatment of radicular cysts, seeking evidence demonstrating that the radicular cysts can be eliminated after endodontic treatment. The cysts can be divided in: Apical Pocket Cysts and true cysts. Apical pocket cysts respond to endodontic treatment, while true cysts can only be treated by periradicular surgery. It can be concluded that since the microbial agent is responsible for the apical periodontitis, the majority of these lesions, including cysts regress after nonsurgical endodontic therapy.