Bypass de instrumento endodôntico fraturado: relato de caso / Bypass of a fractured endodontic instrument: case report

Introdução: Mesmo com toda evolução tecnológica desses instrumentos, com o desenvolvimento das limas de liga de níquel-titanio (NiTi) e sistemas mecanizados, as fraturas podem ocorrer durante o preparo químico/mecânico. Existem três abordagens mais regulamente aplicadas para solucionar essa intercorrencia: tentativa de remoção do instrumento com ultrassom, tentativa de ultrapassálo (bypass) ou a obturação do segmento. Objetivo: Relatar um caso da técnica de bypass em instrumento fraturado no canal radicular. Descrição do caso: Paciente, sexo feminino, 47 anos, brasileira, sem condições sistêmicas associadas, foi encaminhada à clínica do Curso de Odontologia da UNIFENAS, Divinópolis, Minas Gerais, Brasil, para resolução de fratura de instrumento no canal mésio- vestibular do primeiro molar superior direito (16). Optou-se pelo tratamento pela técnica de bypass, que envolveu as seguintes etapas: anestesia, abertura, utilização de lima C-Pilot #08 para ultrapassar o instrumento fraturado, odontometria, escalonamento regressivo a partir da lima k#20, desinfecção com hipoclorito de sódio 5%, medicação com hidróxido de cálcio por 21 dias, agitação da substância irrigadora e obturação dos canais radiculares. Conclusão: O bypass ao instrumento é uma técnica conservadora, eficaz e uma solução adequada em casos de fratura de limas endodônticas dentro dos canais radiculares. Essa técnica visa preservar o máximo possível da estrutura dental original, evitando procedimentos mais invasivos.(AU)

Introduction: Even with all technological evolution of these instruments, with the development of nickel-titanium alloy (NiTi) files and mechanized systems, fractures can occur during chemical/mechanical preparation. There are three most commonly applie to resolve this complication: attempting to remove the instrument with ultrasound, attempting to bypass it, or obturating the segment. Objective: To report a case of bypass technique in fractured instrument in the root canal. Case description: A 47-year-old female patient from Brazil, with no associated systemic conditions, was referred to the clinic of the Dentistry Course at UNIFENAS, Divinópolis, Minas Gerais, Brazil, for resolution of an instrument fracture in the mesio-vestibular canal of the right upper first molar (16). Treatment was performed using the bypass technique, which involved the following steps: anesthesia, opening, use of a C-Pilot #08 file to bypass the fractured instrument, odontometry, regressive scaling from the k#20 file, disinfection with 5% sodium hypochlorite, medication with calcium hydroxide for 21 days, agitation of the irrigating substance and root canal filling. Conclusion: Instrument bypass is a conservative, effective technique and an adequate solution in cases of endodontic file fracture within root canals. This technique aims to preserve as much of the original tooth structure as possible, avoiding more invasive procedures.(AU)

Possibility of Bypassing Three Fractured Rotary NiTi Files and Its Correlation with the Degree of Root Canal Curvature and Location of the Fractured File: An In Vitro Study.

Introduction: This study aimed to evaluate the success rate of bypassing three NiTi rotary files (RaCe®, Hero 642®, and K3®), fractured in various root canal locations of extracted mandibular molars with two different canal curvatures. Materials and Methods: Ninety freshly extracted human first or second mandibular molars were selected. Three millimeters of the file tip (RaCe®, Hero 642®, and K3®), was fractured intentionally in the mesiobuccal root canal of each tooth by weakening the file in the last 3 mm of files #30 with 4% taper and preparing the root canals with two different degrees of curvature (n=30). Then, bypass possibility of the fractured files was evaluated using #8, #10, and #15 K-files and compared in different groups. In addition, the rate of accidental procedural errors was compared between these groups. Data were analyzed with univariate analysis and logistic regression models at a significance level of 0.05. Results: The overall success rate of bypassing was 61.1%. RaCe® files had the highest and the K3® files had the lowest bypass possibility rates (P=0.01); the greater the degree of canal curvature, the less successful the bypass procedure (P=0.01). The fracture of the files used to bypass was the most prevalent error. Conclusion: Based on this in vitro study the type of fractured file and the amount of canal curvature affected the success rate of the bypassing technique. In RaCe® files and the mild curvature group, the success rate was the highest.

Effects of Ultrasonic Removal of Fractured Files from the Middle Third of Root Canals on the Resistance to Vertical Root Fracture.

INTRODUCTION: This study aimed to analyze the effects of ultrasonic removal of fractured files from the middle third of root canals on the vertical root fracture resistance. METHODS: This study was an extension of a previous study assessing the effects of fractured file removal on dentinal microcracks. It included 18 bilaterally matched pairs of human mandibular incisors prepared and analyzed in the previous study. Briefly, 1 member of each pair was assigned to an ultrasonic or a control group. In the ultrasonic group, K-files were fractured in the middle third of canals followed by ultrasonic file removal and canal preparation. In the control group, the root canals were simply prepared. Micro-computed tomographic imaging was performed before and after treatment, and the cross-sectional root images were screened for microcracks. For the present study, 3-dimensional reconstruction was performed for volumetric assessments. The fracture resistance was measured using a universal testing machine. All data were statistically analyzed. RESULTS: Fracture loads were significantly smaller in the ultrasonic group (P < .05). The percentage increase in the canal volume significantly influenced the root fracture resistance (P < .05), whereas microcracks had no significant effect (P > .05). CONCLUSIONS: Ultrasonic removal of fractured instruments from the middle third of root canals lowers the vertical root fracture resistance, with increased dentin removal being the primary cause.

[Impact of fractured file removal from the middle third root canal on vertical root fracture resistance: three-dimensional finite element analysis].

Objective: To analyze effect of fractured file removal from the middle third root canal on root fracture resistance using finite element analysis, which provides a theoretical basis for clinical prognosis evaluation. Methods: Two finite-element models were established, the fractured file removal model (fractured file located in the middle third of root canals, followed by ultrasonic file removal and root canal preparation) and the control model (root canal preparation only), and compressive displacement dependencies on compressive force was computed and compared with experimental data for validation. The validated finite-element models were used to analyze the stress distribution differences during the initiation, propagation and completion of the crack between fractured file removal specimen and control one. Results: The critical breaking force of the fractured file removal specimen was 406 N, and the finite element simulation result was 396 N. The critical breaking force of the control specimen was 502 N, and the finite element simulation result was 483 N. The position of crack initiation in the finite element simulation was basically consistent with that in the experiment. The experimental data of compressive test and the results of finite-element computation were in agreement, thus validating the finite-element model. In the process of continuous pressure, the stress distribution of the control root is relatively uniform, and the location of crack initiation and the direction of propagation have a certain unpredictability. Compared with the control root, the stress concentration on the root with fracture file removal was obvious, especially on edges, and the number of cracks are much more. Because of the thinner radicular wall, the crack propagation rate is faster too. Therefore, the overall root fracture resistant is decreased obviously. Conclusions: During the fractured file removal procedure, amount of dentine removed should be minimized, and the edges and corners which caused by fractured file removal should be shaped to smooth in order to reduce the stress concentration and prevent the root from fracture.

Impact of fractured file removal from the middle third root canal on vertical root fracture resistance: three-dimensional finite element analysis / 中华口腔医学杂志

Objective@#To analyze effect of fractured file removal from the middle third root canal on root fracture resistance using finite element analysis, which provides a theoretical basis for clinical prognosis evaluation.@*Methods@#Two finite-element models were established, the fractured file removal model (fractured file located in the middle third of root canals, followed by ultrasonic file removal and root canal preparation) and the control model (root canal preparation only), and compressive displacement dependencies on compressive force was computed and compared with experimental data for validation. The validated finite-element models were used to analyze the stress distribution differences during the initiation, propagation and completion of the crack between fractured file removal specimen and control one.@*Results@#The critical breaking force of the fractured file removal specimen was 406 N, and the finite element simulation result was 396 N. The critical breaking force of the control specimen was 502 N, and the finite element simulation result was 483 N. The position of crack initiation in the finite element simulation was basically consistent with that in the experiment. The experimental data of compressive test and the results of finite-element computation were in agreement, thus validating the finite-element model. In the process of continuous pressure, the stress distribution of the control root is relatively uniform, and the location of crack initiation and the direction of propagation have a certain unpredictability. Compared with the control root, the stress concentration on the root with fracture file removal was obvious, especially on edges, and the number of cracks are much more. Because of the thinner radicular wall, the crack propagation rate is faster too. Therefore, the overall root fracture resistant is decreased obviously.@*Conclusions@#During the fractured file removal procedure, amount of dentine removed should be minimized, and the edges and corners which caused by fractured file removal should be shaped to smooth in order to reduce the stress concentration and prevent the root from fracture.

Effects of ultrasonic removal of fractured files from the middle third of root canals on dentinal cracks: a micro-computed tomography study.

AIM: To evaluate the frequency of dentinal microcracks after ultrasonic removal of fractured files from the middle third of root canals using micro-computed tomography (micro-CT). METHODOLOGY: Eighteen bilaterally matched pairs of human mandibular incisors extracted for periodontal reasons were included. The matched pairs of teeth were then divided into a control group and an experimental group, with one member of each pair assigned to each group. In the control group, the canals were instrumented using the ProTaper Next (PTN) system. In the experimental group, size 20 K-files were fractured in the middle third of the root canals, followed by their ultrasonic removal. Subsequently, the canals were instrumented with the PTN system. All teeth were scanned using high-resolution micro-CT before (preoperative) and after (intraoperative) file removal and after (postoperative) root canal preparation. Pre-, intra-, and postoperative cross-sectional images of the roots were screened to identify the presence of dentinal defects. Two experienced observers evaluated the images twice in a blinded manner. The incidence of dentinal microcracks was noted and statistically analysed using Fisher's exact and McNemar's tests (P = 0.05), with the root cross-section and the tooth root as the units of analysis, respectively. RESULTS: All fractured files in the experimental group were removed successfully. New microcracks were detected in 0.56% (93/16 472) cross-sections (8/18 specimens) generated after file removal in the experimental group. These microcracks were detected 4-6 mm below the root canal orifice and exhibited a width and length of 12-36 µm and 48-72 µm, respectively. They did not disappear or propagate after canal preparation. No new dentinal microcracks were observed in the control group. There was a significant difference in the incidence of new microcracks between the two groups (P < 0.05). CONCLUSIONS: Ultrasonic removal of fractured files from root canals resulted in the formation of short microcracks in a small number of cross-sections in approximately half the specimens. Further studies are necessary to determine the cause and consequences of this finding.