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

Case Study of a Broken Instrument in a Primary Tooth and Literature Review

BACKGROUND

Root canal treatment is an important element of dental treatment, and broken instruments are one cause of endodontic treatment failure. Broken instruments are rarely reported in primary teeth because of their inherently wider and relatively straighter root canals. We describe a case of a patient with a broken instrument in a primary tooth and reviewed the literature across three databases.

CASE PRESENTATION

A boy aged 7 years and 2 months was referred to our hospital because of pain persisting despite multiple dental treatments. Radiographic examination revealed a broken instrument in the maxillary right primary second molar. The patient experienced dental fear, so the treatment proceeded with the use of behavioral management and nitrous oxide, after which his pain disappeared. At the age of 9 years and 2 months, eruption of the successive permanent teeth was confirmed, and no pathological findings were observed except enamel hypoplasia. We undertook a literature review across three databases and found only two articles about broken instruments in primary teeth, neither of which described the eruption of the permanent teeth. All three cases involved primary molars.

CONCLUSIONS

We removed a broken instrument from the root of a primary molar and performed root canal treatment, resulting in a good outcome for the primary molar until it was replaced with successive permanent teeth. Although rare, broken instruments in the roots of primary molars do occur, and care should be taken during root canal treatment of primary molars.

Dynamic torque and screw-in force of four different glide path instruments assessed in simulated single- and double-curved canals: An in vitro study

Background/purpose

The glide path instruments are the introductory instruments into the canals; thus, they should be durable enough to withstand torsional stress/screw-in force. This study aimed to investigate the torque and screw-in force of TruNatomy Glider (TN), ProGLIDER (PG), Hyflex EDM (EDM) and Dent Craft RE (RE) glide path instruments in single- and double-curved canals.

Materials and methods

Each instrument brand was divided into two groups (n = 7 each) according to the canal configuration. Torque and screw-in force were recorded during automated instrumentation of simulated resin canals with XSmart IQ cordless motor after the canal patency was checked with a #10 K-file. The values were statistically analyzed using the Kolmogorov-Smirnov test followed by the Kruskal Wallis test and the Mann-Whitney U test with Bonferroni correction (α = 0.05).

Results

TN produced significantly higher torque than RE in single-curved canals and PG in double-curved canals (P < 0.05). EDM yielded significantly higher screw-in force than TN and RE in single-curved canals (P < 0.05), but there was no significant difference in double-curved canals (P > 0.05). A significant effect of different canal configurations was only detected for screw-in force in EDM (P < 0.05).

Conclusion

TN in single-curved canals and RE in double-curved canals yielded higher torque values, while EDM exhibited greater screw-in force in both canal configurations. No effect of different canal configurations was detected for torque, but a significant impact was detected for screw-in force in EDM.

Retrieval of Separated Intracanal Endodontic Instruments: A Series of Four Case Reports

The separation of an endodontic instrument during a root canal procedure is one of the most common endodontic mishaps. Separation of endodontic instruments may block access to the apical portion of the root and hamper the disinfection process. It obstructs the appropriate debridement of the canal apical to the fragment, jeopardizing the treatment's outcome. However, due to the advancements in the methods and armamentarium, the effective retrieval of a separated instrument (SI) from the root canal has become possible. This paper includes a case series of management of separated instruments whereby SI was successfully removed in four cases. The instruments were separated intracanal at various levels in the middle and apical third of maxillary and mandibular molar teeth. The level of separation was located, staging performed, and SI was removed using an ultrasonic device under magnification. Removal of the SI was followed by obturation till the entire working length and subsequent post-endodontic restoration. Patient satisfaction with treatment outcomes in all cases was good. Case evaluation, good armamentarium, adequate knowledge along with good clinical skills and experience aid in the successful retrieval of separated instruments. Removal of the instrument without further damage to radicular dentin is important to maintain the integrity of the tooth.

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.

Piezoelectric versus conventional techniques for orthognathic surgery: Systematic review and meta-analysis

PURPOSE

A systematic review and meta-analysis of the advantages and disadvantages of the piezo surgery comparing with conventional osteotomy in orthognathic surgery.

METHODS

We conducted this systemic review in accordance with the preferred reporting items for systematic reviews and meta-analysis (PRISMA) statement. We searched for relevant studies in the PubMed/MEDLINE, Embase databases, Lilacs, Scopus and Science Direct to identify prospective and retrospective studies, compare patient outcomes (intraoperative blood loss, operative time, neurosensory disturbance) after performing orthognathic surgery by conventional saw or piezo-electric device. According to pool individual results we used the mean difference (MD) with the 95% confidence interval (95% CI).

RESULTS

Among three studies that used conventional saw and three studies used piezo-electric device and nine studies used both techniques, the operative time required to perform orthognathic standard procedures was longer using piezo-electric device compared to conventional saw. The results showed that during using the conventional saw to perform orthognathic surgery the amount of the blood loss was higher than the amount while using piezo-electric device (MD -140.4 mL; P = 0.29). based on the studies that evaluated neurosensory disturbance, after 3 months and 6 months respectively, neurosensory disturbance was seen in 23.8% and 23.4% of patient who underwent conventional osteotomy versus 4.3% and 2.4% of the patients who underwent surgery in which piezo surgery was used. Our meta-analysis showed difference in neurosensory disturbance between piezo-surgery and conventional surgery at 3 months (MD -19.5; P = 0.11) and 6 months (MD -21; P = 0.5) postoperatively.

CONCLUSION

Piezo-electric device enabled lower blood loss and higher nerve integrity rates in outcomes according to the complications that associated with orthognathic surgery.

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.

Ethical Aspects concerning Instrument Separation and Perforations during Endodontic Treatment: A Cross-Sectional Study

Aim

During endodontic treatment, dentists may face various unwanted procedural accidents, at any stage of the treatment that might compromise endodontic treatment outcome and bring obstacles to dentists as well. This study aimed to address and analyze several ethical concerns relating to the behavioural conduct of dentists towards endodontic instrument separation as well as perforation of the crown and/or root during root canal treatment in Riyadh, Saudi Arabia.

Method

Hundred and eleven questionnaires were distributed among dentists working in Riyadh in university clinics and government and private sectors. Data were collected, reviewed, and statistically analyzed by Fisher's exact and chi-square tests at a 5% significance level, using SPSS software.

Results

54.5% of the respondents have encountered instrument separation. 53.2% stated that they would inform the patient about the instrument separation. 43.6% of the respondents had experienced perforation during root canal treatment, and 54.9% reported that they would inform the patient of the accident.

Conclusion

Within the limitation of this survey, we concluded that most of the dental professionals did not hesitate to adhere to the correct ethical conduct, and they would inform the patient if an incident occurred.

Sealer penetration: effect of separated file's cross-section, taper and motion characteristics

OBJECTIVES

The separated root canal instruments may affect the quality of root canal filling, hence the success of endodontic treatment. The aim of this study was to evaluate the effects of separated file fragments of nickel-titanium rotary systems with different cross-section, taper and motion characteristics on the apical sealer penetration in oval-shaped root canals via confocal laser scanning microscope (CLSM).

MATERIALS AND METHODS

Distal roots of 60 mandibular molars with oval-shaped root canals were randomly divided into 4 groups as follows: group 1, FlexMaster Nickel Titanium Rotary File System (NTRFS) (separated instrument: 30/.06); group 2, ProTaper Next NTRFS (X3); group 3, ProTaper Universal NTRFS (F3); group 4, Revo-S NTRFS (AS30/.06). Root canals were filled with gutta-percha and AH plus labelled with 0.1% rhodamine B using a warm vertical compaction technique. Each specimen was horizontally sectioned at 1st, 3rd and 5th mm from apical foramen. Amount of maximum and average penetration depths, penetration percentage and sealer penetrated area were measured and analysed with one-way repeated measures of ANOVA and the Bonferroni post hoc tests. p < 0.05 was considered significant.

RESULTS

The penetration depth, percentage and penetrated area of the sealer increased from apical to coronal in all systems. The maximum and average penetration depths and penetration areas were higher in FlexMaster and Revo-S groups at the 3rd mm (p < 0.05). At the 5th mm, the Revo-S group had a higher penetration percentage, when compared with ProTaper Next and ProTaper Universal groups (p < 0.05).

CONCLUSIONS

In the 1st mm, separated fragments of any system did not allow the penetration of the sealer, while it was observed that the files with constant taper showed more positive results in terms of sealer penetration at apical 3rd and 5th mm.

CLINICAL RELEVANCE

In the presence of a separated file, the taper of the file might significantly affect the amount of penetrated sealer into the dentinal tubules as compared with the cross-section and motion characteristics of the file.

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.

The incidence of nickel-titanium endodontic hand file fractures: A 7-year retrospective study in a tertiary care hospital

Aim:

The present retrospective cross-sectional study aims to evaluate the incidence and factors associated with nickel-titanium hand file fractures in root canal-treated teeth in a tertiary care hospital of western India.

Methodology:

The diagnostic records of intraoral periapical (IOPA) radiographs were analyzed to check for file fractures in the root canal-treated teeth. As a part of standardized departmental protocol, Hand ProTaper Universal file system (Dentsply, India) was used for chemomechanical preparation for root canal treatment. The file fractures were analyzed with reference to age group, type of teeth, curvature of the canal, site of file fracture in the canal, length of file fracture, level of file fracture, distance of the file fracture from the apex, and obturation status of the file-fractured tooth. Chi-square test was applied to assess the significance difference between the tested groups.

Results:

A total of 19,810 IOPA X-rays were screened and 2728 root canal-treated teeth were found and of these 2728 cases, 109 file-fractured teeth were observed.

Conclusion:

The total incidence of file fractures was 3.9/100 root canal-treated cases, and mandibular molars with severely curved canals (>25°) had shown the maximum incidence of file fractures.

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.

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.

Success Rate and Time for Bypassing the Fractured Segments of Four NiTi Rotary Instruments

INTRODUCTION

The aim of this in vitro study was to compare the success rate and time required for bypassing the fractured segments of four different nickel-titanium (NiTi) rotary systems.

METHODS AND MATERIALS

This study was conducted on the mesiobuccal canals of 60 mandibular molars with fully-formed apices. Fifteen Flex Master, K3, RaCe and Hero Shaper instruments with 0.04 taper and tip size of #30 and 25 mm in length, were obtained. These instruments were notched at a point 3 mm from the tip of the instrument and were driven into the canals using a handpiece until the instruments fractured and became lodged therein. In the next step, an endodontist tried to bypass the fractured segment using K-files. The number of bypassed samples and the time required for bypassing of each sample were recorded. The Chi-square test was used to compare the bypassing rate among the experimental groups. One-way analysis of variance followed by Tukey's post hoc test was conducted to compare the time taken for bypassing of the fractured fragments.

RESULTS

One instrument in Flex Master group and two broken segments in each of the K3 and Hero groups were not bypassed. All of the samples in RaCe group were bypassed. No significant difference was found among four tested groups regarding rate of bypassing (P=0.738). The time taken to bypass fragments in the Hero group was significantly more than in those of K3 (P=0.047) and RaCe (P=0.024).

CONCLUSION

Under the limitations of this study, design features of rotary files can influence the time needed to bypass separated fragments.

Scanning Electron Microscopic Evaluation of Residual Smear Layer Following Preparation of Curved Root Canals Using Hand Instrumentation or Two Engine-Driven Systems

Introduction:

In this experimental study, the amount of smear layer (SL) remnants in curved root canals after chemomechanical instrumentation with two engine-driven systems or hand instrumentation was evaluated.

Methods and Materials:

Forty-eight mesiobuccal roots of mandibular first molars with curvatures ranging between 25 and 35 degrees (according to Schneider’s method) were divided into three groups (n=16) which were prepared by either the ProTaper Universal file series, Reciproc single file system or hand instrumentation. The canals were intermittently irrigated with 5.25% NaOCl and 17% (ethylenediaminetetraacetic acid) EDTA, followed by distilled water as the final rinse. The roots were split longitudinally and the apical third of the specimens were evaluated under 2500× magnification with a scanning electron microscope (SEM). The mean scores of the SL were calculated and analyzed using the non-parametric Kruskal-Wallis and Mann-Whitney U tests.

Results:

The mean scores of the SL were 2.00±0.73, 1.94±0.68 and 1.44±0.63 µm for the ProTaper Universal, Reciproc and hand instrumentation, respectively. Mean score of SL was significantly less in the hand instrumentation group than the ProTaper (P=0.027) and Reciproc (P=0.035) groups. The difference between the two engine-driven systems, however, was not significant (P=0.803).

Conclusion:

The amount of smear layer in the apical third of curved root canals prepared with both engine-driven systems was similar and greater than the hand instrumentation technique. Complete cleanliness was not attained.

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.

Practitioner experience with sonic osteotomy compared to bur and ultrasonic saw: a pilot in vitro study

The aim of the present study was to compare subjective experiences using bur, ultrasonic, and sonic osteotomy systems. Ten novice (N) and 10 expert (E) practitioners performed osteotomies on bovine ribs with each system. They scored ease of handling and sense of accuracy on visual analogue scales. The duration of the osteotomy procedure and the amount of noise were recorded objectively. Learning experience was evaluated in a second run. The Mann-Whitney U-test, Wilcoxon signed rank tests, and Spearman's rank correlation coefficient were used for the statistical analyses. The sonic system was significantly slower, with the worst noise impact (92.9dB; standard deviation (SD) 7.1). However, both user groups improved significantly in the second run (N 7.9, E 7.6). There were no significant differences in handling. The sense of accuracy was evaluated to be significantly best for the sonic system (N 8.4, E 8.4), compared to the ultrasonic system (N 7.1, E 7.1; both P=0.043) and bur system (N 5.5, P=0.002; E 6.0, P=0.006). The practitioners had a promising experience with the application of the ultrasonic system and particularly with the sonic system.

Endodontic instruments after torsional failure: nanoindentation test

This study aimed to evaluate effects of torsional loading on the mechanical properties of endodontic instruments using the nanoindentation technique. ProFile (PF; size 30, taper 04; Dentsply Maillefer, Switzerland) and stainless steel (SS; size 30, taper 02; Mani, Japan) instruments were subjected to torsional test. Nanoindentation was then performed adjacent to the edge of fracture (edge) and at the cutting part beside the shank (shank). Hardness and elastic modulus were measured under 100-mN force on 100 locations at each region, and compared to those obtained from the same regions on new instruments. It showed that PF and SS instruments failed at 559 ± 67 and 596 ± 73 rotation degrees and mean maximum torque of 0.90 ± 0.07 and 0.99 ± 0.05 N-cm, respectively. Hardness and elastic modulus ranged 4.8-6.7 and 118-339 GPa in SS, and 2.7-3.2 and 52-81 GPa in PF. Significant differences between torsion-fractured and new instruments in hardness and elastic modulus were detected in the SS system used. While in PF system, the edge region after torsional fracture had significantly lower hardness and elastic modulus compared to new instruments. The local hardness and modulus of elasticity of endodontic instruments adjacent to the fracture edge are significantly reduced by torsional loading.

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.

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.

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.

Success rates for removing or bypassing fractured instruments: a prospective clinical study

INTRODUCTION

The objective of this study was to evaluate the success rates of standardized techniques for removing or bypassing fractured instruments from root canals and determine whether visualization of the fractured instrument with the aid of an operating microscope has any impact on the success rates.

METHODS

In this prospective study, attempts were made to visualize 112 fractured instruments under a dental operating microscope after creating a straight-line access to the fragment. By using ultrasonic tips alone or associated with bypassing, the Ruddle technique was attempted to remove the 68 visible instruments. Bypassing was performed for the 44 nonvisible fragments. The χ(2) test was performed to assess whether any significant difference occurred between the success rates observed for the visible and nonvisible fractured instrument groups.

RESULTS

The overall success rate (removal and bypassing) was 70.5% (n = 79). In the visible fragment group, the success rate was 85.3% (n = 58), and in the nonvisible fragment group it was 47.7% (n = 21). Success rates were significantly higher when the fragment was visible (P = .0009).

CONCLUSIONS

The standardized techniques used in this study for removing or bypassing fractured instruments were effective, and approximately 2 times greater success rate was obtained when the fragment was visible inside the root canal compared with when it was nonvisible.

Effect of retained fractured instruments on tooth resistance to vertical fracture with or without attempt at removal

AIMS

To investigate the effect of retained fractured endodontic instruments on root strength and to evaluate the effectiveness of several root filling materials in reinforcing roots that had undergone unsuccessful attempt at removal of fractured instruments.

METHODOLOGY

Seventy five mandibular premolar roots were divided into five groups. In group A (control), canals were prepared to a size F5-ProTaper instrument and filled with gutta-percha and TubliSeal sealer fragments. In the experimental groups (B, C, D and E), 4 mm of F5-ProTaper instruments were fractured in the apical one-third of the canal and then treated as follows: in group B, the fragments were left in situ without attempt at removal, and canals were filled with gutta-percha and TubliSeal sealer (GP No Removal). In groups C, D and E, an attempt at removal of the fragment was simulated by preparing a staging platform coronal to the fragment using modified Gates Glidden burs (No 2-5). Canals in group C were filled with gutta-percha and TubliSeal sealer (GP Removal), group D filled with Resilon (Resilon Removal) and group E with mineral trioxide aggregate (MTA Removal). Roots then underwent vertical fracture. Data were analysed using the one-way anova at P<0.05.

RESULTS

Roots in the GP Removal group had significantly lower values for mean force for fracture (404.9 N). There was no significant difference between the control group and GP No Removal (765.2 and 707.8, respectively). Resilon Removal and MTA Removal groups (577.3 and 566.6 N) were not significantly different from the GP No Removal group.

CONCLUSIONS

Leaving fractured instruments in the apical one-third of the canal does not appear to affect the resistance of the root to vertical fracture; Resilon and MTA appear to compensate for root dentine loss that occurred as a consequence of attempts at retrieval of fractured instruments when used as canal filling materials.

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.

Piezoosteotomy in orthognathic surgery versus conventional saw and chisel osteotomy

INTRODUCTION

Piezoosteotomy was assessed as alternative osteotomy method in orthognathic surgery regarding handling, time requirement, nerve and vessel impairment.

MATERIALS AND METHODS

In this comparative clinical experience, 90 patient's orthognathic surgery procedures were performed in typical distribution prospectively by piezoosteotomy: 34 (38%) monosegment, 47 (52%) segmented LeFortI osteotomies, 94 (52%) sagittal split osteotomies, 11 (12%) symphyseal, and 4 (2%) mandibular body osteotomies. As controls served 90 retrospective patients with conventional saw and chisel osteotomy: 58 (64%) monosegment, 27 (30%) segmented LeFortI osteotomies, 130 (72%) sagittal split, and 4 (4%) symphyseal osteotomies.

RESULTS AND DISCUSSION

Piezoosteotomies were individually designed to interdigitate the jaw segments after repositioning. The pterygomaxillary suture weakened angulated tools; auxiliary chisels were required in 100% of cases for the nasal septum and lateral nasal walls, in 33% for pterygoid processes. The dorsal maxilla as the pterygoid process were easily reduced; 15% mandibular osteotomies required sawing, while the lingual dorsal osteotomy was performed by manual feedback due to limited visibility. Bloodloss decreased from average 537 +/- 208 ml vs. 772 +/- 338 ml (p = 0.0001). Operation time remained unchanged: 223 +/- 70 min vs. 238 +/- 60 min (p = 0.2) for a conventional bimaxillary procedure. Clinical courses and reossification were unobtrusive. Alveolar inferior nerve sensitivity was retained in 98% of the piezoosteotomy collective versus 84% of controls (p = 0.0001) at 3 months postoperative testing.

CONCLUSION

Piezoelectric osteotomy did not prolong the operation and reduced blood loss as alveolar nerve impairment. A few patients required additional sawing or chisel. Piezoelectric screw insertion as complex osteotomies may be initiated to simplify the procedure and increase segment interdigitation after repositioning as to minimize the osteofixation time and dimensions.

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.

A Comparison of Three Methods for Preparing Centered Platforms Around Separated Instruments in Curved Canals

This study compared three methods for creating the most centered staging platform (SP) around separated instruments (SI) in curved canals. Green .04 ProFiles, notched at D(3), were separated in the apical third of 42 mesiobuccal canals of maxillary and mandibular molars. Teeth were divided into three groups. SPs were prepared in group 1 with Gates Gliddens (GG) to a size #3; group 2 with LightSpeed to a size 90; and group 3 with incrementally cut rotary .06 ProFiles to size 82. Pre- and postoperative digital radiographs were imported into AutoCAD to measure the deviation of SP from the head of the separated instrument. Pearson's correlation showed a positive relationship between deviation of the SP and the distance of the SI from the elbow of the canal. ANOVA showed that LightSpeed instruments were significantly more effective in preparing a centered staging platform around separated instruments in curved canals when compared to GG drills and ProFiles (p < 0.05).

The Impact of Instrument Fracture on Outcome of Endodontic Treatment

Adoption of rotary nickel-titanium instruments has renewed concerns regarding instrument fracture and its consequences. The frequency of instrument fracture and its impact on treatment outcome were determined from an analysis of specialist endodontic practice records involving 8460 cases. A case-control study of treatment outcomes was conducted on a subset of 146 teeth with a retained instrument fragment (plus 146 matched controls), for which clinical and radiographic follow-up of at least 1 year was available. Masked radiographs were assessed by two calibrated examiners. Overall prevalence of retained fractured instruments was 3.3% of treated teeth. In the case-control study, overall healing rates were 91.8% for cases with a fractured instrument and 94.5% for matched controls (p > 0.05, Fisher's exact test). Healing in both groups was lower in teeth with a preoperative periapical radiolucency (86.7% versus 92.9%, p > 0.05). In the hands of skilled endodontists prognosis was not significantly affected by the presence of a retained fractured instrument.

Intraoral Piezosurgery: Preliminary Results of a New Technique

The piezosurgery instrument, developed in 1988, uses a modulated ultrasonic frequency that permits highly precise and safe cutting of hard tissue. Nerves, vessels, and soft tissue are not injured by the microvibrations (60 to 200 mm/sec), which are optimally adjusted to target only mineralized tissue. The selective and thermally harmless nature of the piezosurgery instrument results in a low bleeding tendency. In addition, the instrument can be used in operations requiring either local or general anesthesia. The precise nature of the instrument allows exact, clean, and smooth cut geometries during surgery. The difference in time requirement for surgical procedures using the piezosurgery instrument in comparison with the conventional drill is negligible. Postoperatively, excellent wound healing, with no nerve and soft tissue injuries, is observed. It is apparent that the range of application of piezosurgery is not limited to minor operations. Because of its highly selective and accurate nature, with its cutting effect exclusively targeting hard tissue, its use may be extended to more complex oral surgery cases, as well as to other interdisciplinary problems.