Removal of Broken Files from Root Canals by Using Ultrasonic Techniques Combined with Dental Microscope: A Retrospective Analysis of Treatment Outcome

Microendodontics at Different Levels From Routine to Complex Cases: A Case Series

Over the past 30 years, the precision with which endodontics is performed has improved as a result of the advancements in technologies. Endodontists deal with intricate cases regularly, which appears to necessitate greater visual acuity. The invention of the dental operating microscope has been the most significant revolution. Nonetheless, due to a variety of behavioral variables, the use of magnification has yet to be adopted into general practice. The present case series aims to provide insight into the use of dental operating microscopes at different levels (routine to complex) in the field of endodontics and seeks to encourage the use of magnification in daily practice. The first level shows the non-surgical endodontic treatment of the mandibular molar with a curved canal. In the second case, the separated instrument was retrieved non-surgically using ultrasonics, whereas in the third case, surgical intervention (autotransplantation) was required for the removal of the fractured instrument. The microscope offers numerous advantages, including improved lighting, magnification, and vision of the operation field. High magnification aids in conservative access as well as identifying isthmuses, interpreting the complexity of root canal architecture, removing fractured instruments, minimizing soft and hard tissue stress, and detecting fractures and microfractures. If incorporated into daily practice, this magnifying device will drastically increase the success rate of procedures.

Analysis of Endodontic Successes and Failures in the Removal of Fractured Endodontic Instruments during Retreatment: A Systematic Review, Meta-Analysis, and Trial Sequential Analysis

This study presents a systematic review with meta-analysis to evaluate the success rates of endodontic retreatments in teeth where separated instruments are located within the roots. The search and selection of studies were conducted across two databases, SCOPUS and PubMed, as well as the Cochrane Library registry, yielding a total of 1620 records. Following the selection process, 11 studies were included in the systematic review. Overall, out of 1133 retreated teeth, there were 172 failures in instrument removal and 55 perforations. The meta-analysis results indicate that failures are more frequent when instruments are located in the apical third, with a failure rate of 21%, compared to an 8.8% failure rate in the middle/coronal third. The anatomy of the root canals, particularly the location of the separated instruments, significantly influences the success rates.

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.

Outcome of Contemporary Nonsurgical Endodontic Retreatment: A Systematic Review of Randomized Controlled Trials and Cohort Studies

INTRODUCTION

The success rates of NS-ReTx have varied across decades of prior research. Nonetheless, recent endodontic advances have substantially enhanced case management. This systematic review aimed to identify rigorous studies on contemporary NS-ReTx, investigating both periapical healing-evaluated strictly for complete resolution or loosely for size reduction of periapical radiolucency-and success, denoting clinical normalcy combined with periapical healing.

METHODS

We systematically searched MEDLINE, Embase, Web of Science, the Cochrane Library, and gray literature from January 1988 to December 2022. Article selection and data extraction were independently conducted by 3 reviewers. Selected studies underwent risk of bias assessment, and evidence quality using the Grading of Recommendations, Assessment, Development, and Evaluation approach. Meta-analysis and meta-regression established pooled outcome rates, 95% confidence intervals (CIs), and significant clinical prognostic factors (P < .05).

RESULTS

Twenty-nine articles were included. Pooled periapical healing rates using strict and loose criteria were 78.8% (95% CI: 75.2-82.4) and 87.5% (95% CI: 83.8-91.2), respectively. Pooled success rates using strict and loose criteria were 78.0% (95% CI: 74.9-81.2) and 86.4% (95% CI: 82.6-90.1), respectively. Meta-regression analyses revealed significant influences on NS-ReTx outcomes (P < .05), including periapical status, lesion size, apical root filling extent, and follow-up duration.

CONCLUSIONS

Contemporary NS-ReTx shows encouraging outcomes, achieving periapical healing and success rates ranging from approximately 78% (strict criteria) to 87% (loose criteria). The absence of or smaller preoperative lesions, adequate root filling length, and extended follow-ups significantly improve NS-ReTx outcomes. Integrating these factors into treatment planning is pivotal for optimizing the outcome of NS-ReTx.

The Management of Fractured Dental Instruments: A Case Series

The most common problem faced by dentists during root canal therapy is instrument separation. Instrument separation leads to the inefficient biomechanical preparation of the canals, which can affect the outcome of the root canal-treated tooth. Hence, bypassing the fractured instrument or removal can be accounted as a viable choice to maintain the structural integrity of the tooth. This article illustrates a case series wherein the fractured instrument was managed successfully with the use of conservative techniques.

Endodontic Orthograde Retreatments: Challenges and Solutions

Endodontic orthograde retreatments are considered one of the possible treatment options in case of post-treatment diseases considering the promising results present in the literature. Despite this, a plethora of articles have been published on this topic, and drawing conclusions could be challenging. For this reason, this review aims to summarize the crucial points on each aspect of non-surgical endodontic retreatments, discussing and comparing the current protocols, techniques, materials, and indications. Taking into consideration data from the literature, in terms of diagnosis, CBCT should be considered the first choice, since it can thoroughly affect the diagnosis and treatment plan. Regarding the procedural phases, some conclusions can be drawn: when present, coronal restoration materials such as crowns, partial prostheses, post, and core should be removed; the use of magnification devices, ultrasonic instruments, and an in-depth interpretation of radiographic images with both 2D and 3D images are strongly recommended during the orifice location; additional protocols such as irrigants activation, ultrasonic cleaning, and rotary or reciprocating instrumentation of treated canals are strongly recommended for filling materials removal and to achieve a high-quality chemo-mechanical disinfection; perforations should be treated as soon as possible, and the material of choice to treat them is the MTA or other calcium-silicate-based repair materials; the presence of ledges does not intrinsically reduce the success rate of RCRts if properly managed; in case of instrument fragments, their removal should be considered as the first treatment option, however many variables should be considered to select the proper technique or consider the option of bypassing.

Efficacy of the HBW Ultrasonic Ring for retrieval of fragmented manual or rotatory instruments

A study was conducted to evaluate the success rates of bypassing or removing fragments of instruments that had fractured within the roots of mandibular molars using a HBW Ultrasonic Ring. Forty extracted first permanent mandibular molars with root canal curvature were included. The teeth were distributed randomly into four groups according to the type of instrument and the root canal third where they had fractured. The success rate for removal of instrument fragments was 100% for both of two stainless steel groups, 90% for a nitinol middle third group, and 80% for a nitinol apical third group. The mean time required for instrument removal was around 40 min. The HBW Ultrasonic Ring showed acceptable experimental results for retrieval of broken instrument fragments.

MAGNIFICATION, ULTRASONICS AND BIOCERAMICS - THE IDEAL TRIO FOR FILE RETRIEVAL: A CASE REPORT

During routine endodontic therapy, a clinician may encounter many procedural errors which alter the course and outcome of the treatment. Instrument separation is one of the most common types of procedural error, resulting in metallic obstruction in the canal and impeding efficient cleaning and shaping of the root canal. The clinician has to evaluate the options of attempting retrieval, bypassing or leaving the fragment as it is. When an attempt such a fragment becomes difficult, it should be retrieved with the help of ultrasonics under magnification and the canals should with bioceramic sealer to improve the tooths prognosis.

Nonsurgical Management of a Large Periapical Lesion Following Instrument Retrieval From the Apical Third: A Case Report With a Three-Year Follow-Up

Instrument separation in the apical third of the tooth, which is associated with a large periapical lesion, presents an arduous task for the clinician. This case report presents nonsurgical endodontic management of a maxillary central incisor associated with a large periapical lesion and a separated instrument in the apical third of the root canal. A 28-year-old male patient presented with pain and labial swelling in the left maxillary central incisor region. Pulp sensibility testing showed no response. The radiograph revealed the presence of a separated instrument in the apical third of the root canal and periapical radiolucency. A diagnosis of previously initiated therapy with acute apical abscess was made. In the first visit, instrument retrieval was done using ProUltra Endo tips (Dentsply Sirona, York, Pennsylvania) under a dental operating microscope. In the subsequent visit, obturation was done as the patient was asymptomatic. The patient was recalled for follow-up at six, 12, 18, 24, and 36 months. Complete healing of the periapical tissues was evident on the radiograph, and the tooth remained functional for the entire follow-up period of three years. The successful outcome seen in this case shows that even large periapical lesions can be managed conservatively by nonsurgical endodontic treatment

Influence of Cross-Section and Pitch on the Mechanical Response of NiTi Endodontic Files under Bending and Torsional Conditions—A Finite Element Analysis

In this article, the effects of cross-section and pitch on the mechanical response of NiTi endodontic files is studied by means of finite element analyses. The study was conducted over a set of eight endodontic rotary files, whose geometry was obtained from combinations of two cross-sections(square and triangular) and four pitches. Each file was subjected to bending and torsional analyses, simulating the testing conditions indicated in the ISO 3630 Standard, in order to assess their stiffness and mechanical strength. The results indicate that endodontic files with a square cross-section have double the stiffness of those with triangular cross-sections, both in terms of bending and torsion. For both loading modes, endodontic files with a triangular cross-section can undergo larger deformations before overload failure than those with a square cross-section: up to 20% more in bending and 40% in torsion. Moreover, under equivalent boundary conditions, endodontic files with triangular cross-sections present a higher fatigue life than those with square cross-sections: up to more than 300% higher for small pitches. The effect of pitch on the stiffness and strength of the file is smaller than that of the cross-section shape, but smaller pitches could be beneficial when using a triangularcross-section, as they increase the bending flexibility, fatigue life, and torsion stiffness. These results suggest a clinical recommendation for the use of files with a triangular-shaped cross-section and a small pitch in order to minimize ledging and maximize fatigue life. Finally, in this study, we reveal the sensitivity of the orientation of files with respect to the bending direction, which must be taken into account when designing, reporting, and interpreting test results under such loading conditions.

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.

Management of a radiopaque foreign body associated with a lower first premolar: A case report

Operator mishaps significantly affects root canal treatment outcome. However, several factors affect root canal anatomy of teeth. Therefore, knowledge of teeth anatomy and the use of advanced technologies like cone-beam computed tomography (CBCT), magnification, and illumination are crucial for better diagnostic purposes and to avoid any procedural errors. In this case report, we present a case of a 32-year-old male patient with a radiopaque foreign body associated with a lower first premolar tooth and how do the use of advanced technologies could affect the treatment outcome.

The applications of ultrasound, and ultrasonography in dentistry: a scoping review of the literature

OBJECTIVES

This scoping review aims to summarize the available literature on the clinical applications of ultrasonography and ultrasound in diagnostic, therapeutic, and interventional dental applications.

MATERIALS AND METHODS

We followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses, Extension for Scoping Reviews checklist and conducted a protocol-driven scoping review of randomized controlled trials, cohort studies, cross-sectional studies, case-control studies, and case series that assessed ultrasonography or ultrasound use as a stand-alone diagnostic, therapeutic, and interventional tool in dentistry. We included studies published after 1980, study samples ≥ 10, with diagnostic, concordance, or therapeutic outcomes. We searched Ovid MEDLINE, Embase, and others (up to April 2021) and extracted information regarding study level, patient level, test or treatment level, and outcome level data.

RESULTS

Five interventional studies (related to oral medicine, temporomandibular disorders, and dental anesthesia), eight therapeutic studies (related to surgery and orthodontics), and seventy-five diagnostic studies (related to orthodontics, surgery, endodontics, oral medicine, temporomandibular disorders, restorative dentistry, and periodontology) were identified and presented in this review.

CONCLUSION

Ultrasonography has a well-established niche in diagnostic dentistry, while therapeutic and interventional ultrasounds have a smaller, yet present, niche in dentistry. However, further research is needed to report the precise estimates of the diagnostic, therapeutic, and interventional effects.

CLINICAL SIGNIFICANCE

Dentists are mostly unfamiliar with ultrasonography and ultrasound and their potential uses. This review maps the diagnostic and therapeutic applications of ultrasonography and ultrasound technology in dentistry and highlights the current challenges, gaps of knowledge, and research status of ultrasound technology in this regard.

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.

Cyclic and spontaneous movement of a fractured and extruded instrument back into the root canal: A rare case report

Retreatment of endodontically involved teeth may require the removal of obstruction from root canal space. Instrument fracture is an undesirable and stressful incident which can negatively affect the prognosis of the tooth. Any corrective step taken should be performed with utmost care to prevent extrusion of the fragment into periapex. This case report describes a rare occurrence of movement of a fractured instrument during inter-appointment period. A previously treated left mandibular first molar with a fractured instrument was taken up for retreatment. During the course of treatment, the fractured fragment which was previously located in the apical third of the distal canal was dislodged into the periapical region. However, it was found that fragment moved back inside the canal after the inter-appointment period. The same sequence of events repeated before the instrument could be retrieved. Hydrostatic and vascular pressure build due to periapical inflammation could be cited reasons for such a movement.

Outcome of Endodontic Treatment through Existing Full Coverage Restorations: An Endodontic Practice Case Series

INTRODUCTION

This case series assessed the outcome of nonsurgical endodontic treatment completed through retained full coverage restorations (FCRs) in a board-certified endodontist private practice. The number of cases completed by the first author was 153.

METHODS

All cases were performed following a standardized protocol for treatment and restoration depending on the type of FCR. Number of cases that showed up for 2- to 4-year follow-up was 127, with 83% recall rate. The age range of patients was 33-95 years, with mean age of 54.734 years. The mean recall time was 2.448 years. FCRs and their distribution were as follows: 4 anterior teeth, 14 premolars, and 109 molars. There were 103 nonsurgical root canal treatments and 24 retreatments. Patients who presented for recall had 74 porcelain fused to metal crowns, 17 zirconia crowns, 15 abutments of porcelain fused to metal bridges, 14 lithium disilicate crowns, 5 gold crowns, 1 full metal crown, and 1 gold onlay.

RESULTS

There were no endodontically related failures. Six cases failed; 3 were due to vertical root fractures, 1 was due to horizontal root fracture, and 2 were due to extensive recurrent caries causing restorative failure. The percentage of healed cases following the American Association of Endodontists outcome criteria adopted in 2004 with intact retained FCR was 95.3%.

CONCLUSIONS

The results suggest predictable favorable outcomes for nonsurgical endodontic treatment through FCR following the proposed protocol for diagnosis, treatment, and restoration.

Techniques to address fractured instruments in the middle or apical third of the root canal in human permanent teeth: a systematic review of the in vitro studies

OBJECTIVE

The objective of this study is to investigate techniques for approaching fractured instruments in the root canal and to present possible outcomes in relation to dentin thickness, fracture resistance, technique success, and clinical time.

MATERIALS AND METHODS

The bibliographic research was carried out in PubMed, Cochrane, Lilacs, Web of Science, Scopus, grey literature, and manual search. Following the inclusion and exclusion criteria, the titles and abstracts of 506 articles were read. Of these, 60 articles were selected and read in full. Fourteen articles were included in this systematic review.

RESULTS

The most studied technique was the ultrasonic technique and obtained good general results. The more apically the instrument is located, the more difficult it is to remove, the more dentin is removed, and the lower the fracture resistance of the tooth. When removal is not possible, the bypass technique can be performed (bypassing), and on weakened teeth or with little dental remnants, the GentleWave System technique can be used.

CONCLUSION

This systematic review shows the evidence from laboratory studies that the curvature and the root third in which the fracture of instruments occurred is relevant to fracture resistance and success. The ultrasonic technique got the best results. Well-conducted clinical studies should be performed for clinical practice.

CLINICAL RELEVANCE

The approach of fractured instruments in the root canal is efficient with the use of ultrasound, bypass technique, and Gentle Wave System.

A Modified Partial Platform Technique to Retrieve Instrument Fragments from Curved and Narrow Canals: A Report of 2 Cases

Two cases are reported to present the "Burrow platform" (BP) technique. The BP technique uses a partial platform for retrieving instrument fragments, thereby reducing the loss of radicular dentin.The BP technique is a microscope-aided approach implementing coated ultrasonic tips to create an access to instrument fragments in the middle and apical thirds of the root canal. The technique consists of 4 steps: (1) coronal access, (2) radicular access, (3) partial platform, and (4) exposure of the fragment and retrieval. A precise, angulated access pathway is specific to the BP technique. In the coronal half, the radicular access pathway extends toward the outer wall of the curvature. In the apical half, the radicular access pathway is oriented toward the inside of the curvature. One and 4 instrument fragments were successfully retrieved in the respective cases. At follow-up, all teeth were asymptomatic and had responded favorably to the treatment.The BP technique may present a suitable alternative to fragment removal from curved canals and slender roots to avoid ledge formation, transportation, and perforation. Instrument retrieval using the BP technique can be performed using commonly available armamentarium.

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.

Efficiency and Temperature Rise of File Ablation by Neodymium:Yttrium-Aluminum-Perovskite Laser In Vitro

INTRODUCTION

Retrieving a separated file in the root canal system requires a skilled clinician. A metal file can be removed by ablation via the neodymium:yttrium-aluminum-perovskite (Nd:YAP) laser; however, the efficiency and potential hazards of the ablation procedure are still unclear. The aim of this study was 2-fold: to investigate the efficiency of file ablation using the Nd:YAP laser and to evaluate the rise in temperature of the root surface in vitro.

METHODS

In part 1 of this study, #10 and #15 C-files (VDW GmbH, Munich, Germany) and ProTaper Next X1 and X2 files (Dentsply Maillefer, Ballaigues, Switzerland) were selected. Under 8.5×, the Nd:YAP laser was used to ablate the files starting at the tip of the file. The length of the file was recorded after each 5-pulse ablation. In part 2 of this study, 3 files each of the #15 C-file and the ProTaper Next X2 were separated in 6 distal roots of mandibular second molars with single canals. Two-pulse and 5-pulse modes were used to ablate the separated files, and the rise in root surface temperature was recorded with an infrared camera. Another 3 unaltered distal roots served as the negative control. For scanning electron microscopic evaluation, the teeth were split with bone scissors and observed under a scanning electron microscope to evaluate the surface change of the file and the root canal wall.

RESULTS

The average length of the ablated files after each 5-pulse interval was 0.113-0.158 mm with no statistical difference between the different files.The temperature rise of the negative control group (mean ± standard deviation = 1.86° ± 0.11°C and 5.81° ± 0.35°C for the 2- and 5-pulse group) was significantly lower than the roots with separated files (mean ± standard deviation = 3.74° ± 0.20°C and 4.02° ± 0.11°C for 2-pulse C-file and ProTaper Next X2; 8.47° ± 0.19°C and 9.04° ± 0.20°C for 5-pulse C-file and ProTaper Next X2). The temperature rise of all groups was lower than 10°C. The 2-pulse group showed a lower temperature rise than the 5-pulse group. The diameter or the type of alloy had no effect on the temperature rise.

CONCLUSIONS

Separated files (stainless steel or nickel-titanium alloy) can be ablated by the Nd:YAP laser. When the number of pulses is less than 5, the temperature rise of the root surface is considered safe to the surrounding periodontium.

Effect of synchronous irrigation on cyclic fatigue of nickel-titanium instrument in the dynamic and static models

OBJECTIVE

To evaluate the effect of synchronous water irrigation on the fatigue resistance of nickel-titanium instrument.

METHODS

A standardized cyclic fatigue test models were established, and five types of nickel-titanium instruments (PTU F1, WO, WOG, RE, and M3) were applied. Each instrument was randomly divided into two groups (N = 12). There was synchronous water irrigation in the experimental group, and no water irrigation in the control group. Besides, ProTaper Universal F1 was randomly divided into 10 groups (N = 20). In the static group, nickel-titanium instruments were divided into one control group (no irrigation, N = 20) and six experimental group (irrigation, N = 20) based on different flow rate, angle and position; while in the dynamic group, instruments were divided into one control group (no irrigation, N = 20) and two experimental group (irrigation, N = 20) based on different flow rate. The rotation time (Time to Failure, TtF) of instruments was recorded and analyzed.

RESULTS

According to the static experiments, the TtF of instruments in all experimental groups was significantly higher than that in the static control group. Besides, the dynamic tests of PTU F1 showed that the TtF in the experimental group was significantly higher than that in the dynamic control group. Compared with control group, the TtF in the experimental groups increased by at least about 30% and up to 160%. The static and dynamic tests of PTU F1 showed that the TtF of nickel-titanium instrument in all experimental groups was significantly higher than that in the control group. However, there was no significant difference between any two experimental groups.

CONCLUSION

Regardless of dynamic or static model, TtF with irrigation was longer than that with non-irrigation, indicating that synchronous irrigation can increase the fatigue resistance of nickel-titanium instrument. However, different irrigation conditions may have the same effect on the fatigue resistance.

Preventing nickel-titanium rotary instrument from breakage by continuous irrigation with different fluids during root canal preparation

To study the effect of continuous irrigation of rotating nickel-titanium instrument with several common clinical fluids on the diameter, breaking length and breaking position of nickel-titanium instrument, so as to provide some reference and theoretical basis for clinical operation and instrument improvement.A standardized curved root canal model was established, and ProTaper Universal (PTU) F1 instrument was selected for root canal preparation. The nickel-titanium F1 instrument was flushed with distilled water, 0.9% NaCl, 0.2% chlorhexidine, 1% sodium hypochlorite and 5% sodium hypochlorite, and the diameter, length and position of the instrument before and after breakage were recorded.Only 5% sodium hypochlorite influenced the diameter of 6 mm marker points under different irrigation conditions (P < .05). There was no statistical difference in the length of broken instruments among all the groups, and torsional deformation mainly occurred at the end of broken instruments. The broken positions of instruments in all the groups were located at the bending segment of the root canal. The breaking frequency of the 5% sodium hypochlorite group was the highest in the area 3-5.5 mm away from apical foramen, while the other 4 groups had the highest breaking frequency in the area 0 to 1.5 mm away from apical foramen.External irrigation with different fluids did not influence the breaking length of instruments. The closer to the apical foramen was, the higher the breaking frequency of instruments was. However, only 5% sodium hypochlorite can affect the diameter of rotary nickel-titanium instruments, and may lead to early breakage of the instrument, indicating that the use of disinfectants, except 5% sodium hypochlorite, cannot reduce breakage resistance of nickel-titanium instrument compared with distilled water flushing. Furthermore, 5% hypochlorite could not be recommended for irrigation in clinical practice.

Comparative evaluation of the effectiveness of ultrasonic tips versus the Terauchi file retrieval kit for the removal of separated endodontic instruments

Objective

The aim of this study was to perform a comparative evaluation of the effectiveness of ultrasonic tips versus the Terauchi file retrieval kit (TFRK) for the removal of broken endodontic instruments.

Materials and Methods

A total of 80 extracted human first mandibular molars with moderate root canal curvature were selected. Following access cavity preparation canal patency was established with a size 10/15 K-file in the mesiobuccal canals of all teeth. The teeth were divided into 2 groups of 40 teeth each: the P group (ProUltra tips) and the T group (TFRK). Each group was further subdivided into 2 smaller groups of 20 teeth each according to whether ProTaper F1 rotary instruments were fractured in either the coronal third (C constituting the PC and TC groups) or the middle third (M constituting the PM and TM groups). Instrument retrieval was performed using either ProUltra tips or the TFRK.

Results

The overall success rate at removing the separated instrument was 90% in group P and 95% in group T (p > 0.05) The mean time for instrument removal was higher with the ultrasonic tips than with the TFRK (p > 0.05).

Conclusion

Both systems are acceptable clinical tools for instrument retrieval but the loop device in the TFRK requires slightly more dexterity than is needed for the ProUltra tips.

Removal of a separated endodontic instrument by using the modified hollow tube-based extractor system: A case report

The frequency of separation of NiTi rotary instruments has increased with the increasing use of these instruments, and this error may result from inadequate experience of using these instruments. This iatrogenic error can complicate root canal treatment, and special experience is required to manage this problem. This case report describes the management of the separation of an F3 instrument from a ProTaper NiTi rotary system. A 30-year-old man was referred to the College of Dentistry, Taibah University (Saudi Arabia) with an intracanal separated NiTi rotary instrument (F3 of the ProTaper system; Dentsply Maillefer, Ballaigues, Switzerland) in the canal of the maxillary right canine. The separated instrument was removed by using the modified hollow tube–based extractor system. The present case revealed that sometimes a simple method can be an effective alternative of a professional method; using NiTi rotary instruments with strict adherence is important for the prevention of instrument separation.

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.

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.

Stress distribution in a mandibular premolar after separated nickel-titanium instrument removal and root canal preparation: a three-dimensional finite element analysis

Objective

This study used finite element analysis (FEA) to assess the von Mises stresses of a mandibular first premolar after removing a separated instrument with an ultrasonic technique.

Methods

FEA models of the original and treated mandibular first premolar were reconstructed, and three models (the original canal, size 30/taper 0.04 canal, and separated instrument removal canal) were created. Two-direction (vertical and lateral) loading patterns were simulated with a 175-N force. The maximum von Mises stresses of the models within the roots from the apex to the cervical region were collected and summarized.

Results

Under vertical and lateral loads, all maximal values in the three models were localized in the straight-line access region. Compared with the original model (model 1), the treated models (models 2 and 3) had greater maximum stress values from the apex to the cervical region. Greater differences in the maximum von Mises stresses between models 2 and 3 were present in the straight-line access region.

Conclusions

Separated instrument removal caused changes in stress distribution and increases in stress concentration in the straight-line access region of roots.

In Vitro Evaluation of a Novel Root Canal Endoscope for Visualizing the Apex of Curved Root Canal Models and an Extracted Tooth

INTRODUCTION

In straight root canals, intraradicular structures around the root canal orifice and apical foramen can be visualized with a dental operating microscope and commercially available root canal endoscopes. However, the root apex area, including the apical foramen, in a curved root canal cannot be visualized using these devices. In the present study, the potential of a newly developed root canal endoscope implementing an image fiber was examined in 3 types of root canal models and extracted teeth.

METHODS

A straight and 2 curved (10° and 30°) resin block models were prepared. A resolution chart was set at the outer surface of the apical foramen in each model. Using the microscope and the endoscope, the resolution chart was observed, and the captured images were analyzed quantitatively. Additionally, fracture lines in 20 extracted teeth were observed with both devices.

RESULTS

With the dental operating microscope, a resolution chart line was clearly observed in the straight canal model with 18.0 line pairs/mm resolution and an observing capability of 0.16 at 40 × magnification but not in the curved root canal models. With the root canal endoscope, resolution charts in all types of root canal models were visualized, and the resolution and observing capability were 16.0 line pairs/mm and 0.053, respectively. Fracture lines and the apical foramen of the extracted teeth were observed more clearly with the endoscope than the microscope.

CONCLUSIONS

The newly developed root canal endoscope using an image fiber is useful for accurate visualization of the apex area of curved root canals.

Management of fractured root canal treated mandibular molar with separated endodontic instrument extending in periapical region

The aim of this article is to present a case which demonstrates that debriding and disinfecting the infected, under-obturated canal of a tooth using standardized orthograde technique along with surgical retrieval of separated periapical instrument, heals the lesion of endodontic origin. Restoring the tooth with a definitive restoration involving core and crown reinstates the fractured tooth as a functional member of dental arch.

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.

Separation of Nickel-Titanium Rotary and Reciprocating Instruments: A Mini-Review of Clinical Studies

Objective:

This review aimed to evaluate clinical studies that assessed separated NiTi rotary and reciprocating instruments.

Design and Methods:

This review assessed clinical studies involving treatments performed by undergraduate students, graduate students, and endodontic specialists. This review evaluated studies using rotary instruments, reciprocating instruments, and hybrid techniques. The number of uses of the different NiTi rotary and reciprocating systems was also assessed.

Results:

The incidence of separation for rotary instruments ranged from 0% to 23%. Rotary instruments were used from 1 to 50 times depending on the instrument and tooth type. The lowest rate of incidence separation for rotary instruments was obtained by undergraduate students, using a hybrid technique. The separation incidence for reciprocating instruments ranged from 0% to 1.71%. Reciprocating instruments were mostly single-used; one study reported their use up to 3 times. Separation rate in reciprocating instruments was similar in single-use or in multiple uses 0.2%.

Conclusions:

Separation of instruments has dropped recently and seems to be a minor problem in current Endodontics. Multiple uses of NiTi rotary instruments are a possibility without significantly increasing the risk of instrument separation. Single and multiple uses of NiTi reciprocating instruments are also associated with low incidence of separation. Attempting to remove separated instruments should be carefully evaluated.

Comparison of the accuracy of periapical radiography with CBCT taken at 3 different voxel sizes in detecting simulated endodontic complications: an ex vivo study

OBJECTIVES

To compare the accuracy of a photostimulable phosphor plateP sensor with cone beam CT (CBCT) images in the detection of simulated endodontic complications.

METHODS

Following simulated endodontic complications were created in 40 extracted human mandibular molar teeth: Group 1, Instrument separation (N = 10); Group 2, Strip perforation (N = 10); Group 3, Underfilling of root canals (N = 10); Group 4, Overfilling of root canals (N = 10). Intraoral and CBCT images (voxel size: 0.075 , 0.1 and 0.2 mm) were taken. Images were scored by 4 observers according to a 5-point scale. Weighted kappa and intraclass correlation coefficients were calculated. Receiveroperating characteristic analysis was performed and DeLong test was used to compare areaunder curve values. Significance level was set at p < 0.05.

RESULTS

Intraobserver kappa ranged from moderate (0.417) to excellent (0.918). Intraclass correlation coefficients ranged from moderate (0.482) to excellent (0.855). For Group 1 (instrument separation) the highest Az values were obtained for intraoral images and the lowest for CBCT (0.2 mm voxel size) (p < 0.05). The highest Az values were obtained for Group 2 (strip perforation) among all groups. With all CBCT image settings, observers performed similarly and better than intraoral images (p < 0.05) in detection of strip perforation. For Group 3 (underfilling), higher Az values for CBCT images were obtained compared to intraoral images without statistically significant difference (p > 0.05). For Group 4 (overfilling), higher Az values for CBCT images were obtained when compared to digital intraoral for observer 1 and 2 (p < 0.05).

CONCLUSIONS

CBCT images may be useful as an adjunct to periapical imaging in the detection of endodontic complications, such as strip perforation and overfilled root canals.

The Impact of Apical Patency in the Success of Endodontic Treatment of Necrotic Teeth with Apical Periodontitis: A Brief Review

Accumulation of soft tissue or dentinal remnants in the apical region is a common event that can cause blockage of root canals. This event can be avoided if apical patency is performed during the root canal shaping procedures. However, there is no consensus on the role of apical patency in relation to the success of endodontic treatment of necrotic teeth with apical periodontitis. Therefore, the purpose of this paper was to conduct a brief review on the role of apical patency in guaranteeing the success of endodontic treatments of necrotic teeth with apical periodontitis considering two other key points; the root canal anatomy and microbiology.

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.

The impact of fractured endodontic instruments on treatment outcome

Instrument fracture complicates the endodontic procedure by obstructing debridement, delaying treatment completion and affecting the patient's dental experience. When a file fractures there are several treatment options that could be selected, however, the future management should be based on the effect of the fractured instrument on treatment outcome. The aim of the following review was to analyse the literature assessing the impact of endodontic instrument fracture, focusing on its influence on endodontic prognosis and treatment outcome. A comprehensive MEDLINE search including various keywords identified several publications that considered the variables. Analysis of the publications highlighted a paucity of quality long-term clinical outcome studies relating specifically to the influence of instrument fracture. The available studies demonstrated a wide variety of methodologies reporting conflicting findings; therefore, meaningful conclusions were difficult. Within the confines of the literature it appears that retained fractured instruments do not reduce the prognosis of endodontically treated teeth if apical periodontitis is absent, however, if disease is present healing is significantly reduced. Therefore, the stage at which an instrument fractures in infected cases appears likely to be significant as canal disinfection will be compromised accordingly. Considering the risks associated with file removal, perhaps this should only be attempted if apical disease is present. Although it is accepted that the nature of file fracture precludes integration into randomised prospective trials, there is a need for well designed long-term outcome studies investigating the influence of fractured files.

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.

Case series: tooth retention 5 years after irretrievable separation of LightSpeedLSX instruments

INTRODUCTION

Of 3,216 root canals treated endodontically at the Creighton University School of Dentistry from September 1, 2005, to August 31, 2007, with LightSpeedLSX instruments (LightSpeed Technology, Inc, San Antonio, TX), there were 12 cases of irretrievable instrument separation. More than 5 years after the separations, an attempt was made to contact the patients and assess for healing and tooth retention.

METHODS

Third- and fourth-year dental students performed root canal procedures according to protocol from September 1, 2005, to August 31, 2007. A database was collected during the 24-month period recording cases with irretrievable LightspeedLSX separation. Efforts were made from July 2011 to December 2011 to contact the 12 patients for endodontic follow-up. Clinical and radiographic evaluations of healing were performed.

RESULTS

Of the 12 patients with irretrievable separations, 8 patients were contacted and 5 returned to Creighton University School of Dentistry for follow-up. All 8 contacted patients confirmed the presence of the root canal-treated tooth in question, and the teeth of the 5 evaluated patients were determined to be asymptomatic and functional. Radiographic analysis resulted in 2 teeth being classified as complete healing, 2 as uncertain healing, and 1 as no healing.

CONCLUSIONS

The 100% tooth retention rate and the lack of symptoms in 8 contacted (5 evaluated) patients 5 years after treatment suggests that long-term retention and functionality can occur after irretrievable instrument separation. Although tooth retention and functionality are desirable outcomes, radiographic findings may be indicative of inadequate periapical healing, thus requiring the clinician to evaluate whether additional treatment is necessary.

Success of ultrasonic technique in removing fractured rotary nickel-titanium endodontic instruments from root canals and its effect on the required force for root fracture

INTRODUCTION

Fracture of rotary nickel-titanium files is a real concern among endodontists; it affects the long-term prognosis of treatment. Ultrasound is a favorable technique for removing broken files, although it may result in some complications. The aim of this study was to determine the success rate of ultrasonic technique in removing file fragments and to evaluate its influence on the force required to fracture a tooth root.

METHODS

An in vitro study was carried out on 70 extracted maxillary premolars. In the experimental group a #30/.04 taper Hero file was guided into the canal to break and lodge therein. The lodged file was removed by ultrasonic vibration and use of a dental operating microscope. The canals were instrumented with Hero files by using crown-down technique and then obturated. All the teeth were prepared for mechanical testing in Testometric machine to measure the required force for root fracture. The Fisher exact test and independent two-sample t test were used to analyze data.

RESULTS

Ultrasonic technique exhibited a success rate of 80% in removing broken files. Success rate in the roots with file fracture before the curve was 11.5 times more than that of file fracture cases beyond the curve. Other factors such as bypass possibility did not affect success rate. The average time required for removing file fragments was 36.3 ± 7.15 minutes, which did not significantly differ in different file locations within the canal. According to mechanical test results, ultrasonic application did not significantly affect the required force for root fracture. The force required to fracture a root did not significantly differ in various file locations. Vertical fracture in the buccolingual direction (split tooth) was the most incident fracture pattern. Procedural errors observed in this study predominantly included transportation, perforation, and craze line.

CONCLUSIONS

Ultrasonic technique was successful in removing 80% of fractured rotary files and did not significantly affect the required force for root fracture.

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.