Comparison of the time required to create secondary fracture of separated file fragments by using ultrasonic vibration under various canal conditions

Endoscope-assisted retrieval of separated instruments: An ex vivo comparative study of Masserann, microsonic, and loop techniques

Instrument separation during root canal treatment can hinder effective cleaning and shaping, making reliable retrieval techniques essential. Endoscopic visualization might aid in instrument removal procedures offering direct magnification of root canal anatomy. This ex vivo study evaluated the success rate and procedure time of three instrument retrieval techniques - Masserann, microsonic, and loop techniques - under the visualization of dental operation microscope (DOM) assisted by an endoscope. Sixty extracted human mandibular single-rooted teeth with simulated fractures were assigned to the Masserann, microsonic, or ultrasonic with loop techniques (n = 20/group), each performed under endoscopic visualization alongside DOM. The success rate of instrument removal and procedure time were recorded. Complications, such as root perforation, apical extrusion and secondary fracture, were recorded. Statistical analysis was conducted using Pearson χ2 and Kruskal-Wallis tests with 5% significance threshold. Success rates for the microsonic, Masserann, and ultrasonic with loop techniques were 80%, 70%, and 80%, respectively (p > 0.05). The average procedure times were 13.02 min for the microsonic technique, 17.25 min for the Masserann technique, and 17 min for the ultrasonic with loop technique (p > 0.05). The Masserann technique demonstrated a higher complication rate, with two cases each of perforation and apical extrusion, whereas no secondary fractures occurred in any group. Conclusively, the microsonic technique showed the highest success rate with the shortest retrieval time, indicating its efficiency and suitability for instrument removal from root canals, particularly when combined with enhanced visualization through endoscopy.

Predictive factors in the retrieval of endodontic instruments: the relationship between the fragment length and location

Objectives

This study aimed to relate the file fragment length and location in the root canal to the retrieval chances, the clinical time required and the occurrence of secondary fractures.

Materials and Methods

Sixty clinical cases of fractured instruments were included in this study. They were classified according to the instrument length and the location of the root canal. In each group, the success rate in the instrument retrieval, the clinical time required and the occurrence of secondary fractures were evaluated. The collected data were analyzed using the Kruskal-Wallis test on the basis of a 0.05 significance level.

Results

The fragment length showed no significant influence on the assessed variables (p > 0.05). The root third where the instrument was located resulted in an increased clinical time, with statistically significant differences (p < 0.05). However, the procedure success rate and the occurrence of secondary fractures showed no association with these variables.

Conclusions

In accordance with the findings of this study, the fractured fragment length did not influence any of the variables assessed, but it is suggested to focus on the fragment location inside the root canal to decide the retrieval of a fractured instrument.

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.

Separated Instrument in Endodontics: Frequency, Treatment and Prognosis

Instrument separation during endodontic therapy is a frequent accident with rotary instruments being more likely to separate than manual ones. The treatment of cases with a separated instrument can be either conservative or surgical. A conservative approach involves the following treatment choices: a) bypass of the fragment, b) removal of the fragment, c) instrumentation and obturation coronally to the fragment. Concerning the removal of a separated instrument, a variety of techniques and systems have been developed. Ultrasonics, in combination with the operative microscope constitute the most effective and reliable tools for removing a separated endodontic instrument from a root canal. The likelihood of successful removal depends on: the level of separation (coronal, middle or apical third); location in relation to the root canal curvature; the type of separated instrument; its length; the degree of canal curvature and the tooth type. Several complications may occur during the management of a separated instrument: separation of the ultrasonic tip or file used for bypassing or removing the instrument; further separation of the fragment; perforation; ledge; extrusion of the file into periapical tissues; tooth weakening due to dentin removal, as well as excessive temperature rise in periodontal tissues. Prognosis for a tooth retaining a separated instrument depends on the presence of a periapical lesion, the microbial load of the root canal during the time of separation and the quality of the obturation.