Ultrasonic removal of broken instruments in root canals

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.

Efficacy of two instrument retrieval techniques in removing separated rotary and reciprocating nickel-titanium files in mandibular molars - An in vitro study

Context

This in vitro study aimed to evaluate the efficacy of both the staging platform (SP) and burrow platform (BP) techniques in the retrieval of separated rotary and reciprocating files in mesiobuccal (MB) canals of mandibular molars.

Materials and Methods

Forty extracted human mandibular molars with moderate curvature were used in this study. Anatomically, size-matched samples were equally distributed into two different retrieval techniques: Group SP and Group BP. Each group was further subdivided into two subgroups based on their motion kinematics: rotary and reciprocating subgroups. Four millimeters of ProTaper F1 20/07 (rotary) and WaveOne Gold 20/07 (reciprocating) instruments was separated at the apical third region of the MB canal in mandibular molars. Both techniques' success in retrieving separated files was assessed and the canal volume loss was calculated using cone-beam computed tomography. The total time taken for retrieval was also analyzed.

Results

The overall success rate for retrieval of separated instruments (SIs) was 92.5% (37/40). There was no significant difference in retrieval success rates between SP (95%) and BP technique (90%). BP technique (2.32 mm3 and 103 min) resulted in significantly lesser canal volume loss and longer time for retrieval when compared to SP technique (3.75 mm3 and 90 min).

Conclusion

Within the limitations of the current study, in mandibular molars with moderate curvature, the BP technique showed a similar success rate to that of SP technique for retrieval of SI. The BP technique resulted in lesser canal volume loss but took more time for retrieval of SI when compared with SP technique.

Management of an Intracanal Separated Instrument in the Lower Right First Molar: A Case Report

Separating an endodontic instrument is one of the most frequent errors during a root canal treatment. If endodontic instruments get separated, it could hinder disinfection and prevent access to the apical portion of the root. It compromises the success of the treatment by impeding the proper debris removal from the canal. But now that techniques and tools have advanced, it is feasible to remove a separated instrument from the root canal successfully. This case report presents the management of a separated instrument, demonstrating the successful removal of the separated instrument.

Comparative evaluation of increase in temperature on the external root surface of teeth during retrieval of broken NiTi instrument using two ultrasonic tips and two power settings: An in vitro study

Context

An unfavorable event that can hinder endodontic treatment and affect the outcome of root canal treatment is the separation of endodontic instruments. Endodontic instrument separation can occur due to clinical or metallurgical factors. Friction between the ultrasonic tip and the remaining dentin generates heat, which is subsequently transferred to the external root surface. Elevated temperatures exceeding 10°C above body temperature for more than a minute may result in injury to periodontal or bone tissue.

Aim

The aim of this study was to evaluate and compare temperature rise on the external root surface of teeth during retrieval of broken NiTi instrument using two different ultrasonic tips and two power settings.

Materials and Methods

In each group, a sample size of 8 was sufficient to attain a statistical power exceeding 90%, enabling the detection of a minimum mean difference of 0.9204 (delta) through a one-way ANOVA test at a 95% confidence level (alpha 0.05). After access opening and working length determination, samples were randomly distributed into two groups - Group 1 (A and B) - ProUltra tip at high and low power settings and Group 2 (A and B) - Cric Dental IR3 at high and low power settings. The temperature rise was measured using K-type thermocouple thermometer. The comparisons were analyzed using the Kruskal-Wallis test with pairwise comparisons using the Dunn's test.

Results

Group 1A and Group 1B resulted in lower heat generation compared to Group 2A and 2B and its difference was statistically significant (P < 0.05). Minimum temperature rise is seen in the ProUltra group at lower power settings (Group 1A) at the apical level and maximum temperature rise is seen in the Cric Dental IR3 group at higher power settings (Group 2B) at the middle third level.

Conclusion

It was found that there is a significant temperature rise seen when ultrasonic tips are used for the retrieval of separated files, especially at higher power settings. The ProUltra tip demonstrated the lowest temperature rise at lower power settings, particularly at the apical level, whereas the IR3 Cric Dental tip exhibited the highest temperature rise, notably at higher power settings and the middle third level.

Effects of ultrasonics and trephine burs on dentinal microcrack formation during broken instrument removal procedures: A micro-CT analysis

The objective of this study was to compare the effects of ultrasonic and trephine burs on microcrack formation during the removal of broken instruments, utilising micro-computed tomography (Micro-CT). Twenty-five extracted human mandibular molars were used for this study. The hand files were fractured into the mesiobuccal canal, except in the control group. In the ultrasonic group (n = 10), ultrasonic tips were used to retrieve the instrument, while in the trephine group (n = 10), trephine burs (Meitrac, Meisinger) and an extractor device were utilised. For the control group (n = 5), only staging platform was prepared. After the removal procedures, micro-CT images were obtained from the specimens. The chi-squared test was used to analyse the data, and significance was considered to be p < 0.05. Overall, 15 736 cross sections were analysed. No significant differences were found between control and experimental groups. Removal of broken instruments with trephine burs caused significantly more dentinal microcracks compared with ultrasonics (p = 0.016).

Present status and future directions - Removal of fractured instruments

Success rate of fractured instrument retrieval varies because it is dependent mainly on several factors including the visibility of the fractured instrument, the length of the fractured instrument in relation to the curvature of the canal, and the techniques applied to each case. This review aims to update the present status on removal of fractured instruments to identify factors and variables that could affect the success of fractured instrument retrieval based on both the preparation techniques and the instrument retrieval techniques. On the other hand, future directions of fractured instrument retrieval should focus on management of non-visible fractured instruments since the removal of those instruments are deemed unpredictable with the current techniques, whereas the removal of visible fractured instruments are considered predictable now. Another possible direction of it is there might be no more instrument fracture due to possible significant changes in the root canal preparation technique which may dispense with the use of rotary instruments.

Dental Operating Microscope-guided Retrieval of Broken Instrument from a Deciduous Molar Using Ultrasonics

Endodontic procedures are associated with various mishaps, one of which is instrument breakage. It can act as an obstruction to mechanical and chemical cleaning of an infected root canal, thereby hampering the prognosis of treatment. Instrument retrieval must be performed with minimum damage to a tooth and surrounding tissues, minimal loss of radicular dentine and simultaneously maintaining the original canal shape as much as possible. This case report represents successful retrieval of a separated K file fragment from the distobuccal canal of the right mandibular primary second molar 85 with ultrasonic energy application under the dental operating microscope.

Comparative Analysis of Ease of Removal of Fractured NiTi Endodontic Rotary Files from the Root Canal System-An In Vitro Study

This study aimed at analyzing and comparing the ease of removal of fractured nickel-titanium (NiTi) endodontic rotary files from the root canal system between the ultrasonic tips and the Endo Rescue appliance removal systems, as well as comparing the volume of dentin removed between ultrasonic tips and the Endo Rescue appliance using a micro-computed tomography (micro-CT) scan.

MATERIAL AND METHODS

Forty NiTi endodontic rotary files were intentionally fractured in 40 root canal systems of 20 lower first molar teeth and distributed into the following study groups: A: Ultrasonic tips (n = 20) (US) and B: Endo Rescue device (n = 20) (ER). Preoperative and postoperative micro-CT scans were uploaded into image processing software to analyze the volumetric variations of dentin using an algorithm that enables progressive differentiation between neighboring pixels after defining and segmenting the fractured NiTi endodontic rotary files and the root canal systems in both micro-CT scans. A non-parametric Mann-Whitney-Wilcoxon test or t-test for independent samples was used to analyze the results.

RESULTS

The US and ES study groups saw 8 (1 mesiobuccal and 7 distal root canal system) and 3 (distal root canal system) fractured NiTi endodontic rotary files removed, respectively. No statistically significant differences were found in the amount of dentin removed between the US and ER study groups at the mesiobuccal (p = 0.9109) and distal root canal system (p = 0.8669).

CONCLUSIONS

Ultrasonic tips enable greater ease of removal of NiTi endodontic rotary files from the root canal system, with similar amounts of dentin removal between the two methods.

Factors Affecting the Removal Time of Separated Instruments

INTRODUCTION

Separated endodontic instruments may adversely affect the outcome of endodontic treatment. The combination of ultrasonic techniques and dental operating microscopes appears to be effective in the removal of separated instruments compared with more randomized techniques. This study evaluated the roles of root canal curvature and separated instrument length on the time needed to loosen and retrieve the instrument fragments.

METHODS

The retrieval procedures of 128 separated instruments referred to a private endodontic practice for retreatment by general practitioners were evaluated in patients who were monitored for a minimum of 6 months. Preoperative cone-beam computed tomographic images were used to measure separated instrument lengths in relation to the degrees of canal curvatures. Ultrasonic instruments were used in the initial phase to remove the tooth structure and to loosen the fractured instrument. In the second phase, ultrasonic instruments, wire loops, or XP Shapers (FKG Dentaire SA, La Chaux-de-Fonds, Switzerland) were used for fragment removal. The time periods for all procedures were recorded. Statistical analysis was completed applying log-normal regression, structural equation modeling, and linear regression using Stata Version 14.2 software (StataCorp LLC, College Station, TX).

RESULTS

All separated instruments were successfully retrieved. Using the protocol in this study, 89.8% of the instruments were removed using ultrasonic instruments alone with a mean time of 221 seconds. The instrument removal time was dependent on both the instrument length and the root canal curvature. Additionally, preparation times were proportionately longer with increasing separated instrument lengths when the loop device was required.

CONCLUSIONS

The preparation phase appears to have an important role in the retrieval of separated instruments. Preparation times for both non-loop and loop groups demonstrate that length and curvature are independent predictors of the log-transformed time. Generally, procedure times were extended with increasing file lengths and higher degrees of canal curvature.

Management of an over-extruded fragment in a C-shaped root canal configuration: A case report and literature review

Separation of root canal instruments is a common incident during root canal treatments' procedures. The complex configuration of root canal systems is one of the most influencing factors, not only during the occurrence of instrument separation but also during the management of such unpleasant incidents. There are few reports on the management of fractured instruments located in the apical third of the root canals apical, especially those extruded beyond the apex. A 37-year-old woman was referred to an endodontic specialist to complete a root canal treatment after the separation of an endodontic file in the middle-third of the C-shaped root canal configuration (Vertucci type II) of the mandibular second molar. A failed attempt at managing the fragment by the dentist resulted in the backward placement of the fragment, which was more apically, and partial extrusion beyond the root apex. The fractured instrument was successfully and safely retrieved using different procedures and techniques including bypassing the fragment, loosening the fragment using ultrasonics and then removing it by the crab-claw shaped tweezers (Zumax broken instruments removal kit). This case report demonstrates the importance of high magnification provided by the dental operating microscopes and sound clinical skills and judgment, especially in assessing the difficulty of cases that is necessary for various treatment approaches. In addition, the availability of different armamentaria to manage separated instruments is essential. Finally, this case report proposes and advocates the idea of removing fractured instruments extruding beyond the apex without surgery.

Microcomputed tomographic investigation of the trepan bur/microtube technique for the removal of fractured instruments from root canals without a dental operating microscope

OBJECTIVES

The aim of this study was to evaluate the removal of fractured instruments in mandibular incisor canals by using the trepan bur/microtube technique without a dental operating microscope (DOM).

MATERIALS AND METHODS

Thirty-four mandibular incisors were selected, and 5-mm apical segments of #25/.06 taper K3 NiTi instruments were fractured in the apical portion of each canal. Coronal enlargement was performed, and a staging platform was prepared at the coronal aspect of the fractured instrument. Then, a trepan bur was used to expose 1-1.5 mm of the fragmented instrument, and a microtube device was used to withdraw the fragment. Microcomputed tomographic (micro-CT) imaging was used to evaluate the geometric changes in the root canal and dentin. The time required for fractured instrument removal in each sample was recorded, and the results were statistically analyzed with a paired t test.

RESULTS

The trepan bur/microtube technique exhibited a success rate of 76.47%, and the average fractured instrument removal time was 8.55 ± 5.81 min. The changes in canal volume and dentin volume from the coronal end of the fractured instrument to 1.5 mm apical to the end were significantly greater than those from the cementoenamel junction (CEJ) to the coronal end of the fractured instrument during fractured instrument removal (P < 0.0001).

CONCLUSIONS

The study showed that the trepan bur/microtube technique had a significant impact on geometric changes in the root canal and dentin from the coronal end of the fractured instrument to 1.5 mm apical to the end.

CLINICAL RELEVANCE

These findings suggest that the trepan bur/microtube technique may be an optional method for fractured instrument removal from relatively straight canals.

The top 10 most-cited articles on the management of fractured instruments: a bibliometric analysis

Objectives

The purpose of this research was to identify the top 10 most-cited articles on the management of fractured or broken instruments and to perform a bibliometric analysis thereof.

Materials and Methods

Published articles related to fractured instruments were screened from online databases, such as Web of Science, Scopus, PubMed, and ScienceDirect, and highly cited papers, with at least 50 citations since publication, were identified. The most-cited articles were selected and analysed with regard to publication title, authorship, the journal of publication, year, institution, country of origin, article type, and number of citations.

Results

The top 10 most-cited articles were from various journals. Most were published in the Journal of Endodontics, followed by the International Endodontic Journal, and Dental Traumatology. The leading countries were Australia, Israel, Switzerland, the USA, and Germany, and the leading institution was the University of Melbourne. The majority of articles among the top 10 articles were clinical research studies (n = 8), followed by a basic research article and a non-systematic review article.

Conclusions

This bibliometric analysis revealed interesting information about scientific progress in endodontics regarding fractured instruments. Overall, clinical research studies and basic research articles published in high-impact endodontic journals had the highest citation rates.

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.

Removal of a Broken Instrument from a Tooth with Apical Periodontitis Using a Novel Approach

Instrument breakage during treatment can lead to serious complications and carries the risk of treatment failure. When a file breaks in the canal, bypassing or removal can be difficult and the long-term prognosis of the tooth may be compromised. Sometimes surgery may be indicated for removal of the broken segment. Often some part of the root cannot be cleaned because of blockage by the broken file. This report presents a specific approach in non- surgical removal of a broken file from a maxillary lateral incisor with a buccal sinus tract and a broken instrument in the apical third which was partially over extended into the periapical lesion. The broken file was accessed through the sinus tract and pushed into the canal. The canal was cleaned and shaped, filled with mineral trioxide aggregate (MTA).

Retained dental needle migration across the skull base to the cochlea presenting as hearing loss

OBJECTIVES

Long-term retained foreign bodies in the human body have been reported across many specialties, but relatively few exist in the ENT literature.

PATIENTS

We present a case report of a patient with a broken dental needle fragment in the posterior oral cavity with subsequent migration to the cochlea over the course of 4 years, eventually leading to hearing loss. CT scan and middle ear exploration demonstrated a 4-cm metallic fragment abutting the base of the cochlea, immediately adjacent to the internal carotid artery.

INTERVENTIONS

The needle segment was removed through an endaural approach without complication.

RESULTS

Postoperatively, the patient had improvements in PTA and speech discrimination, as well as the resolution of chronic otalgia and jaw pain. Imaging, audiologic results, and surgical details and pictures are presented herein.

CONCLUSION

To our knowledge, based on a thorough PubMed and Google Scholar search, there are no reports of such a foreign body migration from the oral cavity to the skull base.

Removal of an instrument fractured by ultrasound and the instrument removal system under visual magnification

AIM

The case of a lower molar with apical periodontitis, which had previous root canal treatment and a fractured instrument in the distal root beyond the foramen, is presented.

BACKGROUND

The simultaneous presence of a foreign body (endodontic instrument or material) in periapical tissues and microorganisms in the root canal, are etiological factors in the formation or maintenance of a periapical lesion, and can lead to failure in endodontic treatment.

CASE DESCRIPTION

This instrument was removed through the staging platform technique, by using ultrasound and an Instrument removal system (IRS) microtube under microscope visual amplification. All the canals were re-instrumented, irrigated with sodium hypochlorite and passive ultrasonic irrigation, removal of smear layer and intracanal medication with calcium hydroxide for 8 days, after which they were filled. The symptoms disappeared and clinical and radiograph 2-year follow-up shows healing of periapical tissues.

CONCLUSION

The combined use of visual magnification microscope, ultrasound and the IRS system by staging platform technique, allowed the removal of an endodontic instrument beyond the foramen, which made it possible to apply a conventional disinfection protocol.

CLINICAL SIGNIFICANCE

Endodontic re-treatment by conservative approach of complicated cases it is an option with good clinical prognosis, before apical surgery or extraction.

Clinical decision-making after endodontic instrument fracture

When a file fractures during root canal treatment there are several treatment options available to the clinician. The definitive management should be based on a thorough knowledge of the success rates of each treatment option, balanced against potential risks of removal or file retention. Although integration of modern techniques into endodontic practice has improved the clinician's ability to remove fractured files, removal may not always be possible or even desirable. The aim of the third and final review in this series was to analyse the literature with regard to the management of fractured files. Analysis of the literature demonstrated that the presence of a fractured instrument need not reduce the prognosis if the case is well treated and there is no evidence of apical disease. Therefore, in cases without apical disease removal of the file may not be necessary and retention or bypass should be considered. If apical disease is present, file fracture significantly reduces prognosis indicating a greater need to attempt file removal or bypass. A plethora of different methods have been employed to remove fractured instruments and although successful, these techniques usually require the use of the operating microscope and specialist care. Removal of a fractured file is not without considerable risk, particularly in the apical regions of the root canal, therefore, leaving the fragment in situ should be considered if referral is not possible. Finally, it is imperative that the patient is informed (accompanied by appropriate record keeping) if instrument fracture occurs during treatment or if a fractured file is discovered during a routine radiographic examination.

Electrochemical-induced dissolution of stainless steel files

AIM

To investigate the effectiveness of the dissolution process when hand stainless steel files are polarized in solutions containing chloride and fluoride to promote their dissolution.

METHODOLOGY

Redox curves and anodic polarization curves were obtained to determine the conditions necessary for the dissolution of stainless steel endodontic files. Anodic polarization of sizes 20 and 30 files was performed, and a t-test (P < 0.05) was used to compare the weight loss, the time of dissolution and the electrical charge generated by both groups of files. Fragments were polarized in simulated root canals to evaluate the dissolution process. After the tests, a size 10 K-file was used to verify the possibility of bypassing the fragment. Radiographic analysis of the simulated canals was used before and after the tests to verify fragment dissolution.

RESULTS

A progressive consumption of the sizes 20 and 30 files was observed with total polarization times of 7.0 and 9.0 min, respectively. Files with the larger diameters exhibited greater weight loss, longer times of dissolution and generated a greater electrical charge during the active dissolution process (t-test, P < 0.05). After 60 min, the anodic polarization of file fragments in simulated root canals resulted in their partial dissolution.

CONCLUSION

A 60-min anodic polarization of stainless steel K-file fragments in simulated root canals resulted in their partial dissolution. The fragments could be bypassed after the test.

Correlation between endodontic broken instrument and nickel level in urine

This study aims to evaluate the correlation between the presences of separated endodontic instrument inside the dental canal and the nickel (Ni) level in the urine samples of subjected patients. Same-gendered and near-aged participants were selected and were instructed to collect their urine in sterile nickel-free plastic containers. The procedures were carried out in the office, and samples were stored in low-temperature cooler for 1 day and then they were transferred to the laboratory for electrothermal atomic absorption spectrometry. The level of Ni was measured and the correlation coefficient was calculated. Data were analyzed using t tests, Pearson's correlation coefficients, and linear regression analysis, at a level of significance P < 0.05. The statistical analysis has showed significant difference in Ni level between endodontic and control groups (P < 0.05). There was no correlation between Ni level in urine and the age or time period of broken instrument inside the canal; however, Ni level of urine and the age of participants in experimental group has demonstrated a positive correlation. The amount of Ni element can be increased in the urine of patients who have experienced broken endodontic instrument inside the dental canal. However, there is no positive correlation between the remaining pieces of instruments inside the canal and the elevation of nickel amount in urine during the tested time period. This issue suggested that the aging of remaining broken instrument inside the canal does not show any remarkable concern regarding the Ni elevation in the urine excreted by an individual.

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

INTRODUCTION

Nickel-titanium files often separate because of mechanical fatigue. The purpose of this study was to determine safe preparation techniques for separated file removal by using ultrasonics.

METHODS

Fifty nickel-titanium file fragments were divided into 5 groups. An ultrasonic tip was activated on a file fragment positioned between dentin blocks simulating several canal conditions: Group 1 consisted of the fragment protruding from a pair of straight dentin blocks. For group 2, the fragment was also positioned between 2 straight dentin blocks except one block was positioned 1 mm more apically than the other block, simulating a troughed area that is often created during file removal attempts. For groups 3-5, the fragment was positioned similarly as group 2 but between blocks with 30°, 45°, and 60° curvatures, respectively. The time it took for secondary fracture to occur was recorded, and the data were statistically analyzed.

RESULTS

Fragments with dentin wall supporting on the opposite side of ultrasonic activation site resisted fracture significantly longer than those without it. Fragments in 30° and 45° curved blocks took significantly longer to fracture than the other groups (Fisher protected least significant difference, P < .05).

CONCLUSIONS

Secondary fracture of separated files appeared to be reduced when the ultrasonic tip was applied to the inner curvature of the canal.

Electrochemical induced dissolution of fragments of nickel-titanium endodontic files and their removal from simulated root canals

AIM

To improve the dissolution process of NiTi endodontic rotary files aiming at fragment removal and the recovery of the original path of the root canal during a clinically acceptable period of time.

METHODOLOGY

Anodic polarization curves and redox curves were obtained to determine the conditions necessary for the dissolution of endodontic files. Anodic polarization of K3 files was performed, and analysis of variance (P < 0.05) was used to compare different test times in relation to weight loss, length loss and electrical charge generated in each solution. The polarization of fragments in simulated root canals was undertaken to evaluate the dissolution process. After the tests, a size 10 K-file was used to verify the possibility to bypass the fragment. The total electrical charge of each test was obtained from the corresponding graph area. Radiographic analysis of the simulated canals was used before and after the tests to verify fragment dissolution.

RESULTS

The weight loss values, the length loss values and the total values of electrical charge in each period of time were significantly higher (P < 0.05) in the tests using the selected solution compared with the solution previously proposed. A progressive consumption of the K3 file tip was observed up to 30 min. The anodic polarization of file fragments in simulated root canals for 60 min resulted in their partial dissolution and enabled the recovery of the original canal pathway with size 10 K-files.

CONCLUSIONS

Increasing fluoride concentration resulted in greater active dissolution of NiTi files. The dissolution of fractured files in simulated root canals enabled the recovery of its original path during a clinically acceptable period of time.

Management of intracanal separated instruments

INTRODUCTION

Intracanal separation of endodontic instruments may hinder cleaning and shaping procedures within the root canal system, with a potential impact on the outcome of treatment. The purposes of this narrative review of separated instruments were to (1) review the literature regarding treatment options, influencing factors, and complications and (2) suggest a decision-making process for their management.

METHODS

An online search was conducted in peer-review journals listed in PubMed to retrieve clinical and experimental studies, case reports, and review articles by using the following key words: instruments, files, obstructions, fractured, separated, broken, removal, retrieval, management, bypassing, and complications with or without root canal and endodontic.

RESULTS

There is a lack of high-level evidence on management of separated instruments. Conventional conservative management includes removal of or bypassing the fragment or filling the root canal system to the coronal level of the fragment. A surgical intervention remains an alternative approach. These approaches are influenced by a number of factors and may be associated with complications. On the basis of current clinical evidence, a decision-making process for management is suggested.

CONCLUSIONS

Guidelines for management of intracanal separated instruments have not been formulated. Decisions on management should consider the following: (1) the constraints of the root canal accommodating the fragment, (2) the stage of root canal preparation at which the instrument separated, (3) the expertise of the clinician, (4) the armamentaria available, (5) the potential complications of the treatment approach adopted, and (6) the strategic importance of the tooth involved and the presence/or absence of periapical pathosis. Clinical experience and understanding of these influencing factors as well as the ability to make a balanced decision are essential.

Utilizing spiral computerized tomography during the removal of a fractured endodontic instrument lying beyond the apical foramen

AIM

To present a case that used spiral computerized tomography (CT) to locate and successfully remove a fractured endodontic instrument lying beyond the apical foramen using a surgical approach.

SUMMARY

The fracture of an endodontic instrument beyond the apical foramen is rare. In this case report, after an attempt to remove a fractured instrument failed, a multi-slice spiral computerized tomography (MSCT) was used for diagnosis and treatment planning. The fractured segment was precisely located and found in the soft tissue and successfully removed by surgery. For the successful removal of a fractured endodontic instrument beyond the apical foramen, the following are necessary: (i) knowledge of the cause of fracture and how to plan treatment; (ii) determining the precise location of the fractured segment using CT; and 3) skilful operation.

KEY LEARNING POINTS

•  Fractured endodontic instruments might lie within the soft tissue. •  Computerized tomography is an effective diagnostic aid for localizing the precise position of fractured instruments.

The outcome of retained instrument removal in a specialist practice

AIM

To determine the success rate of a microendodontic technique for the removal of fractured instruments from root canals.

METHODOLOGY

Removal was attempted on a total of 170 consecutive referral cases with fractured instruments. All removal attempts were performed using an operating microscope and ultrasonic tips using a technique described by Ruddle (2003).

RESULTS

Of the 170 fractured instruments, 162 could be removed without perforation of the root canal, corresponding to a success rate of 95%. At a failure rate of 5%, eight instruments could not be removed, with root wall perforation occurring in one case. The lowest success rate of 93% was found in maxillary molars, the highest success rate of 100% in maxillary premolars and anterior and canine teeth of the maxillary and mandibular jaw. All removal failures occurred in cases where the fractured instruments were located apically or in the middle and apical part of the root. Regarding the angle of root canal curvature, the lowest success rates were found between 21 degrees and 50 degrees.

CONCLUSIONS

The position of the instrument within the root canal, the angle of the curvature of the root canal and the location of the fractured instrument in relation to the root canal curvature were the decisive factors that had a negative influence on the treatment outcome.The removal method tested represents a highly effective technique for the retrieval of fractured instruments.

A novel technique for the removal of fractured instruments in the apical third of curved root canals

AIM

To report on a conservative approach for removal of a fractured file in the severely curved apical portion of the distobuccal canal of a mandibular molar.

SUMMARY

With the assistance of stainless steel hand files and a chloroform-dipped gutta-percha cone, a fractured rotary NiTi instrument was successfully removed. The use of this technique may assist in removal of loose instrument fragments that are not easily accessible to other removal techniques.

KEY LEARNING POINTS

Instrument fractures do not always lead to an unfavourable prognosis and their removal from the apical third of curved canals should not be routinely attempted. The case highlights that it is possible to conservatively remove loosely bound objects from the hard-to-reach areas of the root canal system.

Opinions and attitudes of endodontists and general dental practitioners in the UK towards the intra-canal fracture of endodontic instruments. Part 2

AIM

To investigate the attitudes of general dental practitioners (GDPs) and endodontists in the UK towards management of fractured endodontic instruments.

METHODOLOGY

A questionnaire was sent to 330 systemically selected GDPs and all endodontists working in the UK (170). It was accompanied by a covering letter explaining the aims of the study and indicating that all the information given would remain confidential. Those who did not respond to the first mailing were sent another two mailings. Data were analysed using chi-square test at P <or= 0.05.

RESULTS

The overall response rate was 75%. Only 18.5% of respondents reported that they would retrieve instruments located in the apical third of root canals with a significantly higher proportion of endodontists (25.9%) compared with that of GDPs (14%) doing so. A significantly higher proportion of endodontists (98.5%) used ultrasonics for removal of fractured instruments compared with GDPs (75.8%). The most common complication of fractured instrument retrieval was thought to be excessive removal of dentine (67%). The majority of respondents (88.5%) reported that they would leave the unsuccessfully removed file in situ and obturate the root canal.

CONCLUSION

Both endodontists and GDPs were aware of the limitations of root canal anatomy when removal of fractured instruments was considered. Excessive removal of dentine, the most common complication associated with the removal process, suggests the need for more conservative techniques. Both endodontists and GDPs demonstrated a conservative approach when management of fractured instruments failed. Further studies regarding attitudes of GDPs and endodontists towards some specific aspects of fractured instruments management are required.

Evaluation of the Efficiency of a New File Removal System in Comparison With Two Conventional Systems

A novel file-removal system (FRS) was designed to address weak points of conventional file-removal methods. The purpose of this study was to compare file-removal time and dentin removal rates among the FRS, the Masserann kit (Micro-Mega, Besancon, France), and an ultrasonic file-removal method. Ninety extracted mandibular incisors with separated nickel titanium files were divided into 3 groups of 30 teeth each. Groups 1, 2, and 3 had file-removal attempts made by using the Masserann kit, a CPR-7 titanium ultrasonic tip (Obtura-Spartan Corp., Fenton, MO), and the FRS, respectively. Each group had three operators removing the separated files. Pre-/postoperative digital radiographs were downloaded into image analyzing software that calculated the amount of dentin removed. The FRS needed less time and had less dentin loss than the others (p<0.05). There were statistical differences between the experienced operator and less experienced operators regarding the file-removal time and the dentin removal rates (p<0.05).

Rotary NiTi Instrument Fracture and its Consequences

The fracture of endodontic instruments is a procedural problem creating a major obstacle to normally routine therapy. With the advent of rotary nickel-titanium (NiTi) instruments this issue seems to have assumed such prominence as to be a considerable hindrance to the adoption of this major technical advancement. Considerable research has been undertaken to understand the mechanisms of failure of NiTi alloy to minimize its occurrence. This has led to changes in instrument design, instrumentation protocols, and manufacturing methods. In addition, factors related to clinician experience, technique, and competence have been shown to be influential. From an assessment of the literature presented, we derive clinical recommendations concerning prevention and management of this complication.

Removal of Separated Files from Root Canals With a New File-removal System: Case Reports

There have been many different devices and techniques developed to retrieve instruments fractured during endodontic procedures, but none of them can consistently remove separated instruments from root canals. Iatrogenic accidents such as perforation and canal destruction have been reported during the removal of separated instruments. The file removal process becomes even more difficult when breakage occurs in a curved canal or in the apical third of the canal. Four cases requiring removal of separated files from the apical third of curved canals are presented. All were successfully treated using a newly designed system and technique.

Nonsurgical retreatment

With all the potential for endodontic success, the fact remains clinicians are confronted with posttreatment endodontic disease. When the elected treatment plan is endodontic nonsurgical retreatment, then the goal is to access the pulp chamber and remove materials from the root canal space and if present, address deficiencies or repair defects that are pathologic or iatrogenic in origin. This article provides a literature review with clinical recommendations for one important group of retreatment issues: the removal of posts and broken instruments.

Factors associated with the removal of fractured NiTi instruments from root canal systems

OBJECTIVE

To evaluate the influence of various factors on the success or failure of attempts to remove fragments of separated NiTi instruments from root canals.

STUDY DESIGN

Instrument removal attempts were undertaken on 72 teeth with a separated NiTi instrument using a variety of techniques and armamentarium. Factors including type of tooth, degree of root canal curvature, location of fragment in relation to the root canal curvature, and radiographic length of fragment were analyzed. A success of treatment was defined as removal or complete bypassing of the fragments.

RESULTS

The overall success rate was 53%. The success rate for ProFile fragments was 41% and for the NiTi K-file 60%. The success rate in maxillary teeth was higher than that in mandibular teeth. Of 52 instruments in molars, 28 were successfully removed or bypassed. Of the 12 fragments in premolars, only 2 were removed. All 8 cases in anterior teeth were retrieved completely. When the fragment was localized before the curvature, complete removal was achieved. When the fragments were located at and beyond the curvature, the success rates were 60% and 31%, respectively. In canals with a slight, moderate, and severe curvature, the success rates were 100%, 83%, and 43%, respectively. In general, the longer the fragment, the greater the chance for successful removal or bypass.

CONCLUSIONS

Favorable factors for removal of separated NiTi fragments are straight root canals, anterior teeth, localization before the curvature, fragments longer than 5 mm, and hand NiTi K-file.

Discuss The Prevention And Management Of Procedural Errors During Endodontic Treatment

Procedural errors in endodontics, or alternatively, any mistake that occurs at some point in the process of root canal treatment of a tooth can be a result of factors which the operator has both control, as well no control over. For the majority of these mistakes the operator is at fault, either through lack of operator knowledge or concentration during treatment. This is fortunate in the sense that this means these errors are, in the main, preventable. Keeping in mind that dentists, being human, will commit errors at some point in their career, knowledge as to how to manage these situations is indispensable. As there exists a multitude of possible procedural errors, the areas that are going to be focused on are those which occur more commonly, and those with more disastrous sequelae. These include: diagnosis, radiography, canal access, instrumentation, obturation, tooth isolation and coronal seal.

Perforation risks associated with the use of Masserann endodontic kit drills in mandibular molars

PURPOSE

The use of Masserann kit is a frequently recommended technique for the removal of canal obstructions. Although this technique is usually successful, it may cause excessive removal of dentin tissue in root canals. The aim of this study is to evaluate the perforation risk and the remaining dentin thickness in mesial canals of mandibular molars following the use of Masserann kit.

STUDY DESIGN

Fifty-three extracted human mandibular molars were selected for the study. The teeth were separated into 3 groups based on the degree of curvature of the root canals. By using Radio Visio Graphy and Coral Draw 8.0 software packages, the dentin/cement thickness of root canal was measured before and after the use of Masseran kit drills.

RESULTS

In the severely and moderately curved mesial root of mandibular molars, the Masserann Kit increased the risk of creating thin or perforated walls. Additionally, after 7.5mm depth of drilling, the percentage of perforations increased in all groups.

CONCLUSIONS

With respect to endangering the dentinal walls towards the apex of root canals, Masserann kit drills were found to increase the risk of perforations in curved canals and in deep preparations.

Evaluation of an Ultrasonic Technique to Remove Fractured Rotary Nickel-Titanium Endodontic Instruments from Root Canals: Clinical Cases

The removal of fractured rotary nickel-titanium instruments from small, curved root canals is one of the most complex operative procedures in endodontics. There have been many different devices and techniques developed to remove fractured instruments, but none are consistently successful and all show a high incidence of canal damage such as perforation. A technique using a staging platform and the use of modern ultrasonic tips with direct visualization through a dental operating microscope has recently been evaluated. The use of this technique in clinical practice is described in 24 cases and illustrated by 3 cases.

Evaluation of an Ultrasonic Technique to Remove Fractured Rotary Nickel-Titanium Endodontic Instruments from Root Canals: An Experimental Study

The use of nickel-titanium rotary instruments in endodontic practice is increasing. One frequently mentioned problem is fracture of an instrument within the root canal. To date, there is no consistently safe and successful technique for removing these fractured instruments. This study evaluates the use of an ultrasonic technique to remove fractured rotary nickel-titanium instruments from narrow, curved canals in both simulated (resin blocks) and mesiolingual canals of extracted mandibular first molars. A technique using ultrasonic tips, combined with the creation of a "staging platform" and the use of the dental operating microscope, was consistently successful and safe at removing fractured rotary nickel-titanium instruments from curved root canals, when some part of the fractured instrument segment was located in the straight portion of the canal. When the fractured instrument segment was located entirely around the curve, the success rate was significantly decreased and major canal damage often occurred.

The use of an ultrasonic technique to remove a fractured rotary nickel-titanium instrument from the apical third of a curved root canal

The frequency of use of nickel-titanium rotary instruments in endodontic practice is increasing. One occasionally mentioned problem is fracture of an instrument within the root canal. The broken instrument may prevent access to the root apex, impeding optimal cleaning and shaping procedures. A case report is presented which uses a modern technique, utilising a staging platform and the use of newly designed ultrasonic tips with direct visualisation through a dental operating microscope, to remove a fractured rotary nickel-titanium instrument from the apical third of a curved root canal.

Broken instrument removal--two cases

This paper reports two clinical aids for the removal of broken instruments in root canals using a combination of hand instrumentation and ultrasonic devices. This technique is based on two phases: hand instrumentation with stainless-steel K-file instruments for bypassing the fragments, and K-files mounted on an ultrasonic handpiece for loosening and retrieval of the broken instruments. This method offers the following advantages: conservation of the remaining dentin wall of the root canal and elimination of the necessity for surgical treatment.

Influence of several factors on the success or failure of removal of fractured instruments from the root canal

The influence of several factors on the success rate of removal procedures of fractured endodontic instruments was evaluated postoperatively. In 105 teeth with 113 fragments removal attempts were undertaken using a wide range of techniques and instruments. All cases were analyzed with special regard to the following factors: type of tooth and root canal, site of fragment in relation to root canal curvature, length of fragment, and type of fractured instrument. Success of treatment was defined as removal or complete bypassing of the fragment. Of 82 instruments in molars (maxillary: 32, mandibular: 50), 56 were removed or bypassed (max.: 26, mand.: 30). Of 16 fragments in premolars (max.: 12, mand.: 4), 8 could be removed or bypassed (max.: 6, mand.: 2). Of 14 fragments in canines and incisors (max.: 7, mand.: 7), 13 could be removed completely (max.: 6, mand.: 7). When the fragment was localized before the curvature 2 of 18 cases failed, when localized inside the curvature 13 of 31 cases failed and when localized beyond the curvature 15 of 33 cases failed. Anatomical factors favorable for removal were: straight canals, incisors and canines, localization before the curvature, length of fragment more than 5 mm, localization in the coronal or mesial third of the root canal, reamer or lentulo spirales. In molars removal procedures were most successful in the palatal canals of maxillary molars.

A new approach for the retrieval of broken instruments

The purpose of this article is to present a modified ultrasonic spreader and a new technique that are used for the retrieval of solid obstructions that can not be bypassed by conventional methods. The technique advocated and the instruments proposed are described. A clinical case is discussed to show the possibilities and limitations of both instrument and method.