Can the addition of surfactants to NaOCl irrigation impact on the percentage of voids of root canal filling?

This study evaluated the impact of canal irrigation using surfactants associated to NaOCl on the percentage of voids of root canal filling through micro-computed tomographic (micro-CT) analysis. 27 mandibular mesial roots with Vertucci type II canal configuration with isthmus were selected and scanned in a micro-CT device. The specimens were assigned to three groups (n = 9), according to the irrigation solution during instrumentation: 2.5% NaOCl without additives (control), 2.5% NaOCl with 0.1% Benzalkonium Chloride and 2.5% NaOCl with 0.1% Tween 80. After obturation, the specimens were rescanned, and the percentage of voids were calculated. Data were analysed using one-way ANOVA with a significance level of 5%. The percentage of voids were similar among the groups (p > 0.05). None of the specimens showed completely voids-free areas. The addition of surfactants to NaOCl irrigation did not improve the quality of root canal filling of mandibular mesial root canals.

The impact of long-term storage conditions on the development of experimental dentinal microcracks.

This study evaluated the impact of long-term storage conditions (medium and time) on the development of experimental dentinal microcracks through micro-computed tomography. Sixty freshly extracted premolars were stored in formalin, water, or dry conditions (n = 20) and scanned after 72 h, 30 days, 6 months and 3 years of extraction. The effect of the storage medium and time on the occurrence of dentinal defects was statistically evaluated. A total of 211 000 images were screened revealing the existence of 11 519 slices with dentinal defects. Dry conditions significantly contributed to the development of new defects in all time points. During the 3-year follow-up period, no new defects were detected in the teeth that were stored in water and, in a single tooth, in the formalin group, after 6 months of storage.

Exploring the Efficacy of 6 Preparation Systems for Achieving Minimal Root Canal Transportation: A Micro-CT Investigation.

INTRODUCTION: This study aimed to assess the canal transportation with 6 preparation systems. METHODS: Sixty curved mesial roots of mandibular molars were scanned, and their root canals (n = 20 per group) were prepared with XP-endo Shaper, BioRace, ProTaper Next, Twisted File Adaptive, Reciproc, or Reciproc Blue systems. After preparation, a new scan was conducted, and transportation was determined by comparing the geometric center of the canal in 13,542 cross-sectional slices. The transport direction frequencies were recorded, and linear transport were compared using a Univariate GLM model and Tukey honestly significant difference tests (α = 5 %). RESULTS: Transportation was affected by the preparation system and root third (P < .05), with no significant effect observed for the root canal (P > .05). The Twisted File Adaptive had the highest transport (P < .05), and the lowest transports were observed with XP-endo Shaper, ProTaper Next, and BioRace (P < .05). Reciproc Blue and Reciproc showed intermediate results (P < .05). The apical and coronal third exhibited the lowest and highest transportation, respectively (P < .05). A significant interaction was observed between the preparation system and root third (P < .05). In the coronal third, transportation was mostly toward the disto-inside direction, whereas in the middle and apical thirds, transportation was predominantly toward the mesio-outside direction. CONCLUSIONS: XP-endo Shaper had the lowest mean linear transportation followed by the ProTaper Next, BioRace, Reciproc Blue, and Reciproc systems. The Twisted File Adaptive system had the worst performance. The direction of transportation was generally toward the inner aspect of the canal at the coronal third and toward the outer aspect of the curve at the middle and apical thirds.

Clinical Accuracy and Precision of 3 Multifrequency Electronic Apex Locators Assessed through Micro-Computed Tomographic Imaging.

INTRODUCTION: This study aimed to compare the in vivo accuracy and precision of 3 electronic apex locators (EALs) in determining the position of the major foramen using micro-computed tomographic (micro-CT) technology. METHODS: After access preparation of 23 necrotic or vital teeth from 5 patients, canals were negotiated, and hand files were used to determine the position of the foramen with 3 EALs: Propex Pixi (Dentsply Maillefer, Ballaigues, Switzerland), Woodpex III (Woodpecker Medical Instrument Co, Guilin, China), and Root ZX II (J Morita, Tokyo, Japan). After fixing the silicon stop to the file, teeth were extracted and scanned in a micro-CT device with and without the instrument inserted into the canal. Data sets were coregistered, and the accuracy and precision of the EALs were determined at a tolerance level of ±0.5 mm by measuring the distance from the tip of the instruments to a tangential line crossing the margins of the foramen. Statistical comparisons were performed using Friedman with post hoc related samples sign and Spearman tests (α = 5%). RESULTS: A significant difference was detected comparing the accuracy of Root ZX II (100%), Woodpex III (86.96%), and Propex Pixi (52.17%) (P < .05). There was a lack of significance in the relationship between the pulp status and the accuracy of the tested EALs (P > .05). Propex Pixi was significantly less precise than Root ZX II (P < .05), whereas no difference was found between Woodpex III and Root ZX II or Propex Pixi (P > .05). CONCLUSIONS: EALs presented similar precision, but Woodpex III and Root ZX II showed better accuracy to determine the position of the apical major foramen than Propex Pixi.

Design, metallurgy, mechanical properties, and shaping ability of 3 heat-treated reciprocating systems: a multimethod investigation.

OBJECTIVE: This study aimed to compare 3 reciprocating systems regarding design, metallurgy, mechanical properties, and shaping ability. MATERIALS AND METHODS: New Reciproc Blue R25, WaveOne Gold Primary, and REX 25 instruments (n=41 per group) were analyzed regarding design, metallurgy, and mechanical performance, while shaping ability (untouched canal walls, volume of removed dentin, and hard tissue debris) was tested in 36 anatomically matched root canals of mandibular molars. Results were compared using one-way ANOVA post hoc Tukey and Kruskal-Wallis tests with a significant level set at 5%. RESULTS: All instruments showed symmetrical cross sections with asymmetrical blades, no radial lands, no major defects, and an almost equiatomic nickel and titanium ratio. The highest R-phase start temperatures were observed with WaveOne Gold (46.1°C) and REX (44.8°C), while Reciproc Blue had the lowest R-phase start (34.5°C) and finish (20°C) temperatures. WaveOne Gold had the lowest time to fracture (169 s) and the highest maximum load (301.6 gf) (P <0.05). The maximum torque of Reciproc Blue (2.2 N.cm) and WaveOne Gold (2.1 N.cm) were similar (P >0.05), but lower than REX (2.6 N.cm) (P <0.05). No statistical differences were observed among instruments in the angle of rotation (P >0.05) and in the shaping ability in both mesial and distal canals (P >0.05). CONCLUSION: Although the overall design, temperature transition phases and mechanical behavior parameters were different among tested instruments, they were similar in terms of shaping ability. CLINICAL RELEVANCE: All tested heat-treated NiTi reciprocating systems showed similar shaping ability, without clinically significant errors.

Micro-CT Study of the In Vivo Accuracy of a Wireless Electronic Apex Locator.

INTRODUCTION: This study aimed to compare the in vivo accuracy of Wirele-X and RootZX II electronic apex locators (EALs) in determining the position of the major foramen using micro-computed tomography (micro-CT) as the analytical tool. METHODS: Eleven vital teeth planned for extraction from 5 patients were used. After conventional access cavity preparation, root canals were flared and negotiated up to the apical third with sizes 08 and 10 K-files followed by irrigation with 2.5% NaOCl. K-type files were used to determine the working length of the selected canals using Root ZX II and Wirele-X apex locators until their numeric displays read "0.0." After fixing the silicon stop to the file, teeth were extracted and imaged in a micro-CT device using a double-scan protocol. Image stacks, with and without the file in the root canal, were then co-registered and the measurement error calculated as the absolute difference between the tip of the file and the major foramen. Positive and negative values were recorded when the file tip was detected beyond or short of the major foramen, respectively. Accuracy was determined on stable measurements within ± 0.5 mm when the file tip did not extend beyond the major foramen. The χ2 test was applied to compare the ability of the EALs to detect the position of the major foramen, and the t test for dependent variables was used to verify differences in the 2 measurements obtained in each tooth. Significance level was set at 5%. RESULTS: Within a tolerance level of ± 0.5 mm, no significant differences were observed between the tested EALs regarding the absolute distance values (P = .82) or in their ability to detect the position of the major foramen (χ2 = 0.2588; P = .6109). The accuracy of the Root ZX II and the Wirele-X apex locators within ± 0.5 mm were 81.8% and 90.9%, respectively. CONCLUSIONS: Root ZX II and Wirele-X performed similarly regarding the in vivo detection of the major foramen. Using strict criteria, the accuracy of the Root ZX II and the Wirele-X apex locators were 81.8% and 90.9%, respectively.

A critical analysis of research methods and experimental models to study root canal fillings.

Canal filling materials and techniques have been one of the most studied topics in Endodontics. A simple search using the mesh term "root canal filling" in PubMed revealed more than 11 000 articles, an impressive number that is much higher than "root canal disinfection" (5544 articles) or even the popular "root canal preparation" (8527 articles). The overriding importance attributed to root filling procedures is not merely intuitive. It derived from the appealing relevance given by the appearance of the white lines in common radiographs grounded on retrospective clinical data that had identified the quality of a root filling as one of the major causes of treatment failure (lack of healing). Since the publication of the Washington study, impressive efforts have been made for the release of new materials and techniques, as well as, for the development of a plethora of laboratory methods to assess the quality of root filling procedures. This narrative review aims to address and discuss the most relevant laboratory methods to assess the root canal filling. As filling quality improvements have not translated into higher success rates, as reported in longitudinal clinical studies, more than to deliver a simple methodology-based review, this paper aims to present an in-depth critical view on the assessment of laboratory methods used to study the filling materials and techniques. Recent data indicate that the long-term dimensional stability/degradation over time of endodontic sealers plays a central role in the treatment outcome. In this context, laboratory methods should be developed focusing on predicting, at least to some degree, the long-term clinical behaviour of root canal fillings, rather than simply ranking different materials or techniques.

Present status and future directions - Minimal endodontic access cavities.

In the last decades, the move of medicine towards minimally invasive treatments is notorious and scientifically grounded. As dentistry naturally follows in its footsteps, minimal access preparation have also becume a trend topic in the endodontic field. This procedure aims to maximize preservation of dentine tissue backed up by the idea that this is an effective way to reduce the incidence of post-treatment tooth fracture. However, with the assessment of the body of evidence on this topic, it is possible to observe some key points (a) the demand for nomenclature standardization, (b) the requirement of specific tools such as ultra-flexible instruments, visual magnification, superior illumination, and three-dimensional imaging technology, (c) minimally invasive treatment does not seem to affect orifice location and mechanical preparation when using adequate armamentarium, but it (d) may impair adequate canal cleaning, disinfection and filling procedures, and also (e) it displays contradictory results regarding the ability to increase the tooth strengthen compared to the traditional access cavity. In spite of that, it is undeniable that methodological flaws of some benchtop studies using extracted teeth may be responsible for the conflicting data, thus triggering the need for more sophisticated devices/facilities and specifically designed research in an attempt to make clear the role of the access size/design on long-term teeth survival. Moreover, it is inevitable that a clinical approach such as minimal endodontic access cavities that demands complex tools and skilled and experienced operators bring to the fore doubts on its educational impact mainly when confronted with the conflicting scientific output, ultimately provoking a cost-benefit analysis of its implementation as a routine technique. In addition, this review discusses the ongoing scientific and clinical status of minimally invasive access cavities aiming to input an in-depth and unbiased view over the rationale behind them, uncovering not only the related conceptual and scientific flaws but also outlining future directions for research and clinical practices. The conclusions attempt to skip from passionate disputes highlighting the current body of evidence as weak and incomplete to guide decision making, demanding the development of a close-to-in situ laboratory model or a large and well-controlled clinical trial to solve this matter.

Os primeiros passos para a implementação de um banco de dentes humanos na Faculdade de Odontologia UFF / The first steps to implement a human teeth bank at Faculty of Dentistry - UFF

O Banco de Dentes Humanos (BDH) é uma instituição sem fins lucrativos, vinculada a uma faculdade, universidade ou instituição com o propósito de suprir as necessidades acadêmicas, através do fornecimento de dentes humanos para estudo e treinamento laboratorial dos alunos dos cursos de graduação e pós-graduação. Assim, o presente trabalho teve como objetivo relatar os métodos utilizados para captação, tratamento, seleção, preservação, armazenamento e reutilização de dentes humanos extraídos, realizados por alunos da Faculdade de Odontologia (FO) da Universidade Federal Fluminense (UFF) através de dois projetos deferidos junto a PROAES-UFF. Para isso, foram realizadas campanhas de conscientização e programas de divulgação para a doação de dentes humanos extraídos permanentes e decíduos tanto para a comunidade científica odontológica como para a comunidade leiga. Após 24 meses, foram captados um total de 2.536 dentes, sendo 346 molares superiores, 279 molares inferiores, 262 pré-molares superiores, 418 pré-molares inferiores, 343 caninos, 296 incisivos superiores e 592 incisivos inferiores. As campanhas e ações dos projetos da PROAES-UFF foram eficientes para coletar dentes humanos, suprindo as atividades laboratoriais de diversas disciplinas na graduação e também servindo de estoque para a futura implementação do BDH da FO-UFF.

The Human Teeth Bank (HTB) is a non-profit institution, linked to a college, university or institution with the purpose of meeting academic needs, through the provision of human teeth for study and laboratory training of undergraduate and postgraduate students. Thus, this study aimed to report the methods of capture, treatment, selection, preservation, storage and reuse of extracted human teeth, carried out by students from the Faculty of Dentistry (FO) of Universidade Federal Fluminense (UFF) through two projects approved by PROAES-UFF. To this end, awareness campaigns and outreach programs were carried out for the donation of human teeth extracted, permanent and deciduous, both for the dental scientific community and for the lay community. After 24 months, a total of 2,536 teeth were captured, with 346 upper molars, 279 lower molars, 262 upper premolars, 418 lower premolars, 343 canines, 296 upper incisors and 592 lower incisors. The campaigns and actions of PROAES-UFF projects were efficient in collecting human teeth, supplying the laboratory activities of several disciplines during graduation and also serving as a stock for a future implementation of the HTB of FO-UFF.

Comparison of five rotary systems regarding design, metallurgy, mechanical performance, and canal preparation-a multimethod research.

OBJECTIVES: To compare the design, metallurgy, mechanical performance, and canal preparation of 5 rotary systems. MATERIAL AND METHODS: A total of 735 25-mm NiTi instruments (sizes 0.17[0.18]/.02v, 0.20/.04v, 0.20/.07v, 0.25/.08v, 0.30/.09v) from ProTaper Gold, ProTaper Universal, Premium Taper Gold, Go-Taper Flex, and U-File systems were compared regarding overall geometry and surface finishing (stereomicroscopy and scanning electron microscopy), nickel and titanium ratio (energy-dispersive spectroscopy), phase transformation temperatures (differential scanning calorimetry), mechanical performance (torsional and bending tests), and unprepared canal surface (micro-CT). One-way ANOVA and Mood's median tests were used for statistical comparisons with a significance level set at 5%. RESULTS: Stereomicroscopic analysis showed more spirals and high helical angles in the Premium Taper Gold system. All sets of instruments had symmetrical spirals, no radial lands, no major defects, and an almost equiatomic ratio between nickel and titanium elements, while differences were observed in their tips' geometry and surface finishing. At room temperature (20 °C), DSC test revealed martensitic characteristics for ProTaper Gold and Go-Taper Flex, and mixed austenite plus R-phase for the Premium Taper Gold, while ProTaper Universal and U-Files had full austenitic characteristics. Overall, larger instruments had higher torque resistance and bending load values than smaller ones, while a lack of consistency and mixed values were observed in the angle of rotation. The 0.25/.08v and 0.30/.09v instruments of ProTaper Universal and U-File had the highest maximum torques, the lowest angles of rotation, and the highest bending loads than other tested systems (P < .05). No significant difference was noted regarding the untouched root canal walls after preparation with the tested systems (P > .05). CONCLUSIONS: Although differences observed in the overall geometry and phase transformation temperatures have influenced the results of mechanical tests, unprepared canal surface areas were equivalent among systems. CLINICAL RELEVANCE: Root canal preparation systems with similar geometries might present different mechanical behaviors but equivalent shaping ability.

A critical analysis of research methods and experimental models to study dentinal microcracks.

The purpose of this narrative review was to discuss the scientific milestones that led to the current understanding of the root dentinal microcrack phenomenon based on the interplay between the usage of micro-computed tomography (micro-CT) as an analytical tool alongside a close-to-mouth experimental model. In 2009, reports on the development of dentinal microcracks in extracted teeth after root canal preparation triggered an awareness of the potential for vertical root fractures (VRFs) of endodontically treated teeth could be developed from defects created by the mechanical stress of nickel-titanium preparation systems on dentine. This assumption was taken for granted, even though no cause-effect relationship had been scientifically demonstrated. Since then, several studies using the sectioning method with extracted teeth have been published and the large discrepancy amongst their outcomes soon become evident. Moreover, the high frequency of reported dentinal microcracks largely contrasted with the clinical incidence of VRFs, raising doubts on their methodological reliability. Using micro-CT technology, it was demonstrated by several studies that, in extracted teeth, dentinal defects already existed before the endodontic procedures, indicating that the initial reports framed a non-existing cause-effect relationship between canal preparation and dentinal microcracks. Although these new findings contributed to a better comprehension of this phenomenon, the misconception that microcracks were the starting point for VRFs was only surpassed with a new in situ approach using fresh cadavers. Surprisingly, microcracks were not identified in sound teeth. As a conclusion, dentinal microcracks in extracted teeth can be considered a non-natural occurrence observed only in a laboratory set-up as a consequence of dehydration and storage conditions. Thus, dentinal microcracks shall not be considered as the starting point for VRFs as they do not manifest in non-extracted teeth. Identifying dentinal microcracks as a laboratory phenomenon highlights the impact of recent scientific developments to disclaim the clinical relevance of laboratory-obtained outcomes.

Does sodium thiosulphate avoid the formation of the brown-coloured precipitate as an intermediate irrigant between NaOCl and chlorhexidine?

This study evaluated the efficacy of sodium thiosulphate (ST) as an intermediate irrigant between sodium hypochlorite (NaOCl) and chlorhexidine (CHX) to avoid the formation of the brown-coloured precipitate. The in vitro experiment used microtubes to test the mixture of 2.5% NaOCl, 2% CHX and 5% ST solutions, varying their order and time of addition. In the ex vivo experiment, 10 bovine teeth were divided into two groups according to the intermediate irrigant used: distilled water (control) and 5% ST (experimental). Colour change occurred in all microtubes after interaction between solutions. While the precipitate was not observed in the experimental group, it was seen in all specimens of the control group. The 5% ST was able to prevent the formation of the brown-coloured precipitate in the ex vivo experiment, whereas it only prevented its in vitro formation when the waiting time for adding CHX was 10, 15 and 20 min.

Is canal overinstrumentation able to produce apical root dentinal microcracks in extracted teeth?

AIM: To assess the impact of mechanical overinstrumentation of root canals in extracted teeth on the development of dentinal microcracks in the apical portion of the root by means of micro-computed tomographic (micro-CT) analysis. Root canal preparation short of the canal terminus and at the apical foramen (AF) were used as controls. METHODOLOGY: Twenty 2-rooted maxillary premolars with two canals were selected, scanned in a micro-CT device and the root canals prepared sequentially using Reciproc M-Wire R25 instruments to working lengths: 1 mm short of the AF (AF - 1 mm), at the AF (AF), and overinstrumentation (AF + 1 mm). A micro-CT scan of each specimen was performed after each time point. After reconstruction and co-registration procedures, the images were screened from the cementoenamel junction to the apex (n = 55 352) to identify the presence of dentinal microcracks in the apical third of the root. RESULTS: After the analyses of 55 352 slices, dentinal microcracks were visualized in 12.45% of the images (6892 slices), with 5.73% (3174 slices) in the cervical, 3.57% (1976 slices) in the middle and 3.15% (1740 slices) in the apical third. All dentinal microcracks observed at all time points (AF - 1 mm, AF and AF + 1 mm) were already present in the corresponding images before canal instrumentation. Therefore, no new microcracks were detected, regardless of the working length used for canal instrumentation. CONCLUSION: Reciprocating root canal preparation either short, at or beyond the AF (overinstrumentation) did not create dentinal microcracks in the roots of extracted 2-rooted maxillary premolars.

Root groove depth and inter-orifice canal distance as anatomical predictive factors for danger zone in the mesial root of mandibular first molars.

OBJECTIVES: This study evaluated the danger zone (DZ) in mesial roots of mandibular molars and the correlation between anatomical references of the DZ and some anatomical landmarks including tooth/root length, depth of mesial and distal grooves, and inter-canal orifices distance. MATERIAL AND METHODS: Twenty-eight mesial roots of mandibular molars with 2 independent canals were scanned and divided into 2 groups according to root length. The anatomical landmarks were correlated (Pearson or Spearman coefficients) with root level, thickness, and position of the DZ and also compared (independent samples t or Mann-Whitney tests) between the 2 groups at α = 5%. RESULTS: No statistical difference was observed between groups regarding DZ parameters and depth of mesial and distal grooves (P > 0.05). Orifice distance in group 2 (4.49 ± 0.75 mm) was significantly greater than group 1 (3.76 ± 0.89 mm) (P < 0.05). Significant correlations (P < 0.05) were found between (i) DZ level and root/tooth length (r = 0.54 and 0.49, respectively), (ii) DZ thickness and distal groove depth (r = - 0.45), and orifice distance (r = 0.38), and (iii) DZ position and depth of mesial (r = 0.39) and distal (r = 0.40) grooves. Other variables such as root length and distal groove depth (r = 0.28), and orifice distance and mesial groove depth (r = 0.36) were also correlated (P < 0.05). CONCLUSIONS: The length of tooth/root, the distance of canal orifices, and the depth of mesial/distal grooves of mesial roots of mandibular molars might be predictive factors for the root level, position, and thickness of the DZ. CLINICAL RELEVANCE: The length, distance of mesial canal orifices, and the depth of mesial and distal grooves of the mesial roots of mandibular molars might be moderate predictive factors for the root level, position, and thickness of the DZ.

Glide Path with Reciprocating Driven Pathfinding Instrument: Performance and Fracture Rate.

INTRODUCTION: This study assessed the number of mesial and distal canals of mandibular molars in which the R-Pilot pathfinding reciprocating instrument reached the working length (WL) during macro glide path procedure. Fracture and deformation rates were also evaluated. METHODS: One hundred fifty-six root canals of 52 teeth were scouted to the length of the apical foramen. Then the R-Pilot instrument was positioned at the canal orifice and activated. The instrument was moved by using a pecking motion and light apical pressure. This procedure was repeated in an attempt to reach the WL. The type of fracture and/or instrument deformation was assessed by scanning electron microscopy, whereas the roots with fractured instruments were scanned through micro-computed tomography. The percentage frequency distribution of fractures, deformations, and root canals in which the R-Pilot reached the WL were recorded and statistically compared by using the Pearson's χ2 test with α = 5%. RESULTS: R-Pilot instruments reached the WL in 139 root canals (89.10%), and χ2 test showed a significant difference between the observed frequencies and the expected frequencies (χ2 = 95.41, P = .000). The observed frequencies of fractures (2.56%) and deformations (1.92%) were also significantly lower than the expected (fracture: χ2 = 140.41, P = .000; deformation: χ2 = 144.23, P = .000). Fractures occurred mostly at the apical and curved parts of the root canals. CONCLUSIONS: R-Pilot reached the WL in 89.10% of the root canals of mandibular molars with fracture and deformation rates of 2.56% and 1.92%, respectively.

Influence of autoclave sterilization procedures on the cyclic fatigue resistance of heat-treated nickel-titanium instruments: a systematic review.

OBJECTIVES: This systematic review evaluated the influence of autoclave sterilization procedures on the cyclic fatigue resistance of heat-treated nickel-titanium (NiTi) instruments. MATERIALS AND METHODS: A systematic search without restrictions was conducted in the following electronic databases: PubMed, Scopus, Web of Science, ScienceDirect, Cochrane, and Open Grey. The hand search was also performed in the main endodontic journals. The eligible studies were submitted to the methodological assessment and data extraction. RESULTS: From 203 abstracts, a total of 10 articles matched the eligible criteria. After reading the full articles, 2 were excluded because of the absence of the heat-treated instruments in the experimental design and 3 due to the lack of a control group using heat-treated instruments without autoclave sterilization. From the 5 included studies, 1 presented a low risk of bias, 3 presented moderate and 1 high risk. It was observed heterogeneous findings in the included studies, with autoclave sterilization cycles increasing, decreasing or not affecting the cyclic fatigue life of heat-treated NiTi instruments. However, the retrieved studies evaluating the cyclic fatigue resistance of endodontic instruments presented different protocols and assessing outcomes, this variability makes the findings less comparable within and also between groups and preclude the establishment of an unbiased scientific evidence base. CONCLUSIONS: Considering the little scientific evidence and considerable risk of bias, it is still possible to conclude that autoclave sterilization procedures appear to influence the cyclic fatigue resistance of heat-treated NiTi instruments.

3-dimensional Ability Assessment in Removing Root Filling Material from Pair-matched Oval-shaped Canals Using Thermal-treated Instruments.

INTRODUCTION: The purpose of this study was to evaluate the ability of the XP-endo Shaper instrument (FKG Dentaire, La Chaux-de-Fonds, Switzerland) during the removal of root fillings from oval-shaped canals. M-Wire Reciproc and Reciproc Blue systems (VDW, Munich, Germany) were used as reference instruments for comparison, and micro-computed technology was used as an analytical tool. METHODS: Thirty mandibular incisors with oval-shaped canals were matched based on similar anatomic features of the canal (eg, volume, aspect ratio, and 3-dimensional configuration) after scanning procedures. The canals were prepared with M-Wire Reciproc R25 instruments and filled with gutta-percha and AH Plus sealer (Dentsply DeTrey, Konstanz, Germany) using the continuous wave of condensation technique. Then, the sample was allocated into 3 experimental groups (n = 10) according to the retreatment protocol used: M-Wire Reciproc, Reciproc Blue, and XP-endo Shaper. M-Wire Reciproc R25, Reciproc Blue R25, and XP-endo Shaper instruments were used to remove the root fillings. Apical enlargement was performed with M-Wire Reciproc R40, Reciproc Blue R40, and BioRace BR5 (FKG Dentaire) instruments. Each sample was scanned after each endodontic procedure. The volume of remaining root filling material was quantified before and after apical enlargement. The percentage volumes of root filling reduction in relation to the instrumented canals at both time points (before and after apical enlargement) were calculated and considered for statistical analysis. Data were analyzed statistically with a significance level of 5%. RESULTS: Reciproc Blue presented significantly lower removal of filling material compared with the XP-endo Shaper (Tukey test, P < .05). No difference was detected either between M-Wire Reciproc and Reciproc Blue (Tukey test, P > .05) or M-Wire Reciproc and XP-endo Shaper (Tukey, P > .05). The increase of apical enlargement significantly improved the removal of root fillings from the root canals (P < .05); this effect was similar for all systems (time point × file system, P > .05). CONCLUSIONS: The XP-endo Shaper instrument showed a higher percentage of root filling removal, but no differences were observed comparing M-Wire Reciproc with the XP-endo Shaper or Reciproc Blue. The increase of apical enlargement improved the removal of root fillings in all groups. None of them was able to render root canals completely free from root fillings.

Performance of Reciproc Blue R25 Instruments in Shaping the Canal Space without Glide Path.

INTRODUCTION: This study assessed the frequency in which Reciproc Blue R25 instruments (VDW, Munich, Germany) reached the full working length (WL) of mandibular molar canals without a glide path. The influence of the type of electric motor (ie, conventional corded or cordless) on the instrument's performance was also assessed. METHODS: One hundred mandibular molars with slight to moderate root canals were selected and randomly assigned into 1 of 2 experimental groups according to the type of electric motor used: conventional corded (VDW Silver, VDW) or cordless motors (VDW.CONNECT Drive, VDW). Therefore, 50 molars and 154 root canals were selected for each motor. Reciproc Blue R25 instruments were used until reaching two thirds of the estimated WL. Then, a size 10 K-file was passively inserted to determine the full WL. No active instrumentation movement was performed with a size 10 K-file. Independently, whether a size 10 K-file reached the apex or not, Reciproc Blue R25 instruments were used to complete canal preparation. When the Reciproc Blue R25 instrument was able to reach the full WL, the case was classified as "reaching the full working length" (RFWL). If the instrument was not able to reach the full WL, the case was classified as "not reaching the full working length" (NRFWL). The chi-square test of goodness of fit was used to verify whether the observed frequencies of RFWL and NRFWL adhered to the expected ones. A 5% cutoff level of significance was considered for statistical assumptions. RESULTS: Reciproc Blue R25 instruments were able to reach the full WL in 304 root canals (98.70%). The chi-square test revealed the observed frequencies of RFWL and NRFWL to be significantly different from the expected frequencies (χ2 = 292,208, P = .000). The frequency of RFWL and NRFWL was exactly the same for both types of electric motors. No instrument fractured, and a single file deformed. In 50 of 308 root canals, a size 10 K-file was unable to passively reach the full WL. From these 50 canals, Reciproc Blue R25 instruments were able to reach the full WL in 47 of them. CONCLUSIONS: Reciproc Blue R25 instruments were able to reach the full WL in a high frequency of cases. The type of electric motor used did not interfere in the frequency of RFWL cases. No instrument fractured, and a single file deformed.

Micro-CT evaluation of different final irrigation protocols on the removal of hard-tissue debris from isthmus-containing mesial root of mandibular molars.

OBJECTIVES: This study aimed to compare four final irrigation protocols (passive ultrasonic irrigation [PUI], EndoVac, Self-Adjusting File [SAF] and EasyClean) on the removal of accumulated hard-tissue debris (AHTD) from mesial canals of mandibular molars through microcomputed tomographic (micro-CT) analysis. MATERIALS AND METHODS: Forty mesial roots of mandibular molars presenting isthmuses type I or III were scanned in a micro-CT device and instrumented up to Reciproc R40 instrument. After the completion of canal preparations, root canals of each group were submitted to a final rinse using 20 mL of solution (16 mL of 5.25% NaOCl and 4 mL of 17% EDTA) in a total time of 5 min according to one of the four final irrigation protocols (n = 10): PUI, EndoVac, SAF and EasyClean operated at reciprocating motion. The sample was scanned again after canal preparation and after the use of the final irrigation protocols, and the registered data sets were examined to evaluate the percentage of AHTD. Data were statistically compared using the Tukey test with a significance level set at 5%. RESULTS: All groups presented a decrease on the accumulation of hard-tissue debris after the use of the final irrigation protocols (P < 0.05). No significant differences in the removal of AHTD were observed among the final irrigation protocols (P > 0.05). CONCLUSIONS: All final irrigation protocols showed the same effectiveness in the removal of AHTD. None of them was able to render mesial canals of mandibular molars completely free from packed debris. CLINICAL RELEVANCE: This study highlighted that all final irrigation protocols (PUI, EndoVac, SAF, and EasyClean) promoted a similar removal of AHTD. However, none of the final irrigation protocols was able to render mesial canals of mandibular molars completely free from packed debris.

Micro-CT comparison of XP-endo Finisher and passive ultrasonic irrigation as final irrigation protocols on the removal of accumulated hard-tissue debris from oval shaped-canals.

OBJECTIVE: To compare the effectiveness of the XP-endo Finisher instrument and passive ultrasonic irrigation (PUI) as final irrigation protocols on the removal of accumulated hard-tissue debris (AHTD) from oval-shaped canals using micro-computed tomographic (micro-CT) analysis. METHODS: Twenty mandibular incisors were anatomically pair-matched based on similar morphological dimensions (length, volume, aspect ratio, and configuration) through micro-CT analysis, prepared with Reciproc R25 instrument, scanned again, and assigned to one of the two experimental groups (n = 10), according to the final irrigation protocol: XP-endo Finisher and PUI. After the final irrigation protocols, the specimens were rescanned and the registered datasets were examined to quantify the amount of AHTD. Data were statistically analyzed using Student's t test with a significance level of 5%. RESULTS: The final irrigation protocols were highly similar in terms of volumetric percentage reduction of AHTD (P = 1.000). CONCLUSIONS: XP-endo Finisher and PUI showed the same effectiveness on the removal of AHTD. None of the tested final irrigation protocols completely removed the AHTD from oval-shaped root canals. CLINICAL RELEVANCE: AHTD may be considered clinically relevant because it could harbor bacterial contents away from the disinfection procedures. Both final irrigation protocols were effective on the removal of AHTD.