[Study on fatigue resistance of mechanical nickel-titanium files by phase-locked infrared flaw detection method].

PURPOSE: The fatigue resistance of mechanical nickel-titanium files was tested by phase-locked infrared flaw detection method, in order to timely detect instrument wear, providing reference for clinical safe use and timely abandonment of nickel-titanium files. METHODS: Twenty sets of mechanical nickel-titanium files were selected from Reciproc-Blue(RB), MTWO and S3 respectively, and resin simulated root canals with 60° and 90° bending were prepared, which were divided into 6 subgroups. The fatigue value after use, the number of uses before breaking and the length of fracture of file 25# of each group of files were recorded and compared with SPSS 26.0 software package. RESULTS: With the increase of the times of use, the fatigue value of the three kinds of files increased gradually. Among the two types of curved root canals, the number of uses before fracture in RB group was significantly increased compared with that in MTWO group and S3 group (P＜0.05). The number of uses of the three kinds of files in the 90° curved root canal were significantly less than in the corresponding groups in the 60° curved root canal(P＜0.05). There was no significant difference in the length of fracture among the three kinds of files(P＞0.05). CONCLUSIONS: Phase-locked infrared flaw detection method can be used for non-destructive testing and quantitative analysis of the fatigue degree of nickel-titanium files.

Effect of repetitive up-and-down movements on torque/force generation, surface defects and shaping ability of nickel-titanium rotary instruments: an ex vivo study.

BACKGROUND: The screw-in effect is a tendency of a nickel-titanium (NiTi) rotary endodontic file to be pulled into the canal, which can result in a sudden increase in stress leading to instrument fracture, and over-instrumentation beyond the apex. To reduce screw-in force, repeated up-and-down movements are recommended to distribute flexural stress during instrumentation, especially in curved and constricted canals. However, there is no consensus on the optimal number of repetitions. Therefore, this study aimed to examine how repeated up-and-down movements at the working length affect torque/force generation, surface defects, and canal shaping ability of JIZAI and TruNatomy instruments. METHODS: An original automated root canal instrumentation device was used to prepare canals and to record torque/force changes. The mesial roots of human mandibular molars with approximately 30˚ of canal curvature were selected through geometric matching using micro-computed tomography. The samples were divided into three groups according to the number of up-and-down movements at the working length (1, 3, and 6 times; n = 24 each) and subdivided according to the instruments: JIZAI (#13/0.04 taper, #25/0.04 taper, and #35/0.04 taper) or TruNatomy (#17/0.02 taper, #26/0.04 taper, and #36/0.03 tape) (n = 12 each). The design, surface defects, phase transformation temperatures, nickel-titanium ratios, torque, force, shaping ability, and surface deformation were evaluated. Data were analyzed with the Kruskal-Wallis and Dunn's tests (α = 0.05). RESULTS: The instruments had different designs and phase transformation temperatures. The 3 and 6 up-and-down movements resulted in a smaller upward force compared to 1 movement (p < 0.05). TruNatomy generated significantly less maximum torque, force, and surface wear than JIZAI (p < 0.05). However, TruNatomy exhibited a larger canal deviation (p < 0.05). No statistical differences in shaping ability were detected between different up-and-down movements. CONCLUSIONS: Under laboratory conditions with JIZAI and TruNatomy, a single up-and-down movement at the working length increased the screw-in force of subsequent instruments in severely curved canals in the single-length instrumentation technique. A single up-and-down movement generated more surface defects on the file when using JIZAI. TruNatomy resulted in less stress generation during instrumentation, while JIZAI better maintained the curvature of root canals.

Extrusion of debris during retreatment using various nickel-titanium files in teeth with simulated lateral root perforation.

PURPOSE: To investigate the influence of various nickel-titanium (Ni-Ti) files on debris extrusion during the retreatment of teeth with simulated lateral root perforation, focusing on root resorption. METHODS: Sixty human mandibular premolar teeth were divided into groups with and without perforation and further subdivided based on the retreatment technique. Lateral root perforations were created in one group (Group 1), while the other group had no perforations (Group 2). Two retreatment techniques were compared: Remover (RE)+One RECI (OR) and ProTaper Universal Retreatment (PTUR)+WaveOne Gold (WOG). The weight of the extruded debris was determined. The time of both retreatment procedures was measured. Statistical analyses were performed using a two-way analysis of variance (ANOVA) test (P < 0.05). RESULTS: Teeth with simulated lateral root perforation exhibited higher extrusion of debris during retreatment. In both groups, RE+OR files led to more extruded debris than PTUR+WOG files. However, this difference was statistically significant in Group 2 (P < 0.001). Compared to PTUR+WOG files, RE+OR files showed a statistically significant longer time to remove obturation material (P < 0.001). CONCLUSION: Perforated teeth exhibited significantly higher debris extrusion. While both file systems demonstrated similar debris extrusion in perforated teeth, the RE+OR files significantly increased debris extrusion in non-perforated teeth compared to the PTUR+WOG files.

Retratamiento endodóntico no quirúrgico de molar inferior con lesión apical: estrategia terapéutica / Non-surgical endodontic retreatment of a lower molar with an apical lesion: therapeutic strategy

La terapéutica endodóntica se apoya básicamente en dos modelos teóricos o paradigmas: el concepto de "tubo hueco" técnico y quirúrgico esencialmente mecanicista, y el modelo terapéutico para conductos radiculares, que busca la restitución ad integrum de los tejidos apicales y el hueso alveolar que los rodea. La instrumentación debe complementarse con la limpieza por irrigación abundante y la obturación con un biomaterial bioactivo, con características reológicas que permitan su adaptación plástica a las paredes del conducto radicular y module la respuesta de los tejidos hacia la regeneración con aposición de tejido calcificado en el foramen apical (AU)

Endodontic therapy is basically based on two theoretical models or paradigms, which are the concept of the technical and surgical "hollow tube", essentially mechanistic, and the therapeutic model of root canals, which seeks the ad integrum restitution of the apical tissues and bone. alveolar that surrounds them. The instrumentation must be complemented with cleaning by abundant irrigation, and with a bioactive biomaterial, with rheological characteristics that allows its plastic adaptation to the walls of the root canal and modulates the response of the tissues towards regeneration with apposition of calcified tissue in the apical foramen (AU)

Fifteen years of engine-driven nickel-titanium reciprocating instruments, what do we know so far? An umbrella review.

Numerous systematic reviews (SRs) have produced conflicting findings on engine-driven nickel-titanium reciprocating instruments (reciprocating instruments) since Yared's seminal study 15 years ago. This umbrella review analysed SRs examining the clinical and laboratory evidence regarding reciprocating instruments for root canal treatment. SRs that evaluated qualitatively and/or quantitatively the outcomes postoperative pain, oral health-related quality of life (OHRQoL), shaping ability, debris extrusion, microbial load, endotoxins reduction, cyclic fatigue, file fracture, dentinal cracks and root canal filling removal were included. The AMSTAR 2 tool was used to evaluate SRs quality, while the ROBIS tool to assess risk of bias (RoB). Forty SRs were included. The SRs revealed predominantly 'high' RoB and 'critically low' quality. Most focused on technical outcomes, exhibiting significant methodological and statistical heterogeneity. Findings suggest comparable efficacy between reciprocating and rotary instruments. However, due to the scarcity of high-quality evidence, future well-designed studies and reviews considering core outcome measures are needed.

Effect of simulated clinical use and sterilization on the cyclic fatigue resistance of nickel titanium files.

Aim: Assess the effect of simulated clinical use and sterilization on the cyclic fatigue resistance of Race Evo and Tia Tornado Blue nickel titanium (NiTi) files. Materials and Methods: For this study, a total of sixty-four NiTi files were selected, with thirty-two files each from two different manufacturers. Files from each manufacturer were subdivided into four subgroups (n = 8) based on the test parameters. The control groups included files that were neither used nor sterilized. Files from the test groups were used to prepare the root canals of extracted mandibular premolars and then sterilized. This procedure was repeated once, twice, or thrice, depending on the test group. All files were then subjected to a cyclic fatigue test. Data was statistically analyzed using the Kruskal-Wallis and Mann-Whitney U tests. Results: No significant difference was observed in the number of cycles to failure (NCF) among the subgroups for both types of files (P = 0.869 for Tia Tornado Blue, P = 0.626 for Race Evo). Tia Tornado Blue files displayed significantly higher NCF values in the control (P = 0.021), once (P = 0.027), and thrice (P = 0.031) usage groups when compared to Race Evo files. Conclusions: Repeated clinical use and sterilization for up to three cycles did not affect the cyclic fatigue resistance of Race Evo and Tia Tornado Blue files.

The extended finite element method in endodontics: A scoping review and future directions for cyclic fatigue testing of nickel-titanium instruments.

OBJECTIVES: The present study reviews the current literature regarding the utilization of the extended finite element method (XFEM) in clinical and experimental endodontic studies and the suitability of XFEM in the assessment of cyclic fatigue in rotary endodontic nickel-titanium (NiTi) instruments. MATERIAL AND METHODS: An electronic literature search was conducted using the appropriate search terms, and the titles and abstracts were screened for relevance. The search yielded 13 hits after duplicates were removed, and four studies met the inclusion criteria for review. RESULTS: No studies to date have utilized XFEM to study cyclic fatigue or crack propagation in rotary endodontic NiTi instruments. Challenges such as modelling material inputs and fatigue criteria could explain the lack of utilization of XFEM in the analysis of mechanical behavior in NiTi instruments. CONCLUSIONS: The review showed that XFEM was seldom employed in endodontic literature. Recent work suggests potential promise in using XFEM for modelling NiTi structures.

Electrochemical Properties of Nickel-Titanium Rotary Endodontic Instruments.

INTRODUCTION: Nickel-titanium rotary endodontic files have been commercially available for decades, but more recent innovations have introduced heat-treated and surface-treated files. This study investigated the corrosion properties of various nickel-titanium files in normal saline and sodium hypochlorite (NaOCl). METHODS: Ten different file brands of size 40 with a 0.04 taper were subjected to electrochemical testing in 0.9% NaCl (saline) and 5.25% NaOCl at room temperature. The Open Circuit Potential (OCP) was observed for 1 hour followed by a cyclic polarization test from -300 to 700 mV and back to -300 mV (vs OCP). Nonparametric ANOVA and a pairwise comparison (P < .05) were used for statistical analysis of the OCP at 1 hour and the corrosion current (Icorr) obtained via the cyclic polarization test. RESULTS: Significant differences (P < .05) were found between files with respect to OCP and Icorr in both solutions. Nine files exhibited significantly greater (P < .05) Icorrs in NaOCl than in saline. Conversely, pitting corrosion was observed in the saline solution but not NaOCl. Weak and/or moderate correlations existed between OCP and Icorr measures in the 2 solutions. CONCLUSION: Significant differences in electrochemical properties were observed among the 10 brands of files. Overall, there was not a clear trend between conventional, heat-treated, or surface-treated files among OCP or Icorr in either solution.

Effect of preset torque setting on torque/force generation, shaping ability and surface changes of nickel titanium rotary instrument in different root canal curvature locations: An ex vivo study.

The aim of this study was to evaluate how preset torque settings influence the torque, vertical force, and root canal-centering ability of ProGlider and ProTaper NEXT nickel-titanium rotary instruments in canals with different curvature locations. Based on micro-computed tomography, mesial roots of human mandibular molars (25°-40° curvature) were allocated to the apical curvature (apical 1-5 mm) or the middle curvature (apical 5-9 mm) groups, and mandibular incisors (curvature <5°) to the straight canal group. Each group was subjected to automated instrumentation and torque/force measurement with the preset torque of 1, 2.5, or 5 N•cm. Canal-centering ratios were determined with micro-computed tomography. Instrument fracture occurred only in the 2.5 and 5 N•cm groups in curved canals. The preset torque setting and curvature location did not influence canal shaping ability.

Effects of Side Flattening on Torsional and Cyclic Fracture Resistance of Nickel-Titanium File.

INTRODUCTION: The purpose of this study was to evaluate the effect of side flattening of cutting flutes on the cyclic resistance and torsional resistance of nickel-titanium files. METHODS: Both novel flattened Platinum V.EU (PL) and standard nonflattened CC Premium V.EU (CC) rotaries were tested. For cyclic fatigue tests, all the files were rotated in an artificial root canal with a curvature of 45° and a radius of 6.06 mm at 300 rpm (n = 15 in each group). The number of cycles to failure (NCF) was calculated. For torsional tests, the files were rotated at 2 rpm clockwise until fracture occurred. The maximum torque value at fracture was measured and the toughness and distortion angle were computed. Subsequently, 5 fragments were randomly selected in each experiment, the cross-section and longitudinal direction of the fragments were photographed using a scanning electron microscope. An unpaired t-test was performed at a significance level of 95%. RESULTS: There was a statistically significant difference in NCF between CC and PL (P < .05). CC showed higher NCF than PL. There was no statistically significant difference between CC and PL with regards to the parameters related to torsional resistance (distortion angle, ultimate strength, and toughness) (P > .05). CONCLUSION: Within the limitations of this study, side flattening of the file did not improve cyclic resistance or torsional resistance of the files. As side flattening may reduce a file's cyclic resistance, such files should be used with caution in clinical practice.

Micro-computed tomography analysis of shaping ability of nickel-titanium instruments activated by continuous rotation or adaptive motion.

This study assessed the ability of Twisted File Adaptive (TFA), TruNatomy (TRN) and VDW.Rotate (VR) instruments activated by continuous rotation (CR) and adaptive motion (AM) to shape curved root canals. Thirty mandibular molars with two separate mesial canals 20°-40° curved were collected and scanned using micro-computed tomography (µCT). The canals were then randomly assigned into six groups (n = 10): TRN, VR or TFA instruments activated by CR or AM. TRN groups 17.02, 20.04 and 26.04; VR groups 15.04, 20.05 and 25.06; TFA groups were shaped consecutively using 15K-file, 20.04 and 25.06. After they were shaped, the canals were scanned again. The volume of removed dentin, canal transportation and centring ratio were calculated µCT images. All data were analysed using the Kruskal-Wallis test or one-way analysis of variance (p < 0.05). With both kinematics, the TRN instrument removed the least amount of dentin, the VR-CR and the TFA-AM removed the most (p < 0.05). The transportation and centring ratios among all groups were similar (p > 0.05). The volume of dentin removed, the diameter or design features of the instruments and different kinematics did not affect the centring ratio and the amount of transportation and remained within safe limits. All three instruments activated by either kinematics were found to have similar effectiveness in shaping curved root canals.

Shaping Efficiency of Rotary and Reciprocating Kinematics of Engine-driven Nickel-Titanium Instruments in Moderate and Severely curved Root Canals Using Microcomputed Tomography: A Systematic Review of Ex Vivo Studies.

INTRODUCTION: This systematic review aimed to compare reciprocating with continuous rotary instrumentation kinematics, by means of microcomputed tomography evaluations, in extracted human permanent teeth with moderate and severe canal curvatures. METHODS: The research protocol was registered in the International Prospective Register of Systematic Reviews and given the reference number CRD42023404035. An electronic search was undertaken in MEDLINE (PubMed), EBSCO, Scopus, Web of Science databases until December 2021. Manual screening of issues in endodontic journals and references of relevant articles were assessed individually. The risk of bias (RoB) of the included articles was evaluated with the QUIN tool (Quality Assessment Tool for In Vitro Studies). RESULTS: Among 1640 retrieved articles, 49 were included in the qualitative synthesis. Fifteen articles had low RoB, 33 articles had medium RoB, and only 1 study was at high RoB. Continuous rotary systems had better centering ability in both moderate and severe canal curvatures and resulted in less apical transportation in severely curved root canals. None of the kinematic systems was capable of instrumenting the entire canal surface area. Reciprocating kinematics systems tended to provide higher increase in surface area of severely curved canals and produced fewer dentinal microcracks in moderately curved canals. CONCLUSIONS: The evidence presented in this review suggests that continuous rotary system seems to be better than reciprocating system in solving the major issues encountered during root canal instrumentation of extracted teeth with moderate and severe curvatures.

Comparative Analysis of Irrigation Techniques for Cleaning Efficiency in Isthmus Structures.

INTRODUCTION: This study aimed to evaluate the removal of a biofilm-mimicking hydrogel from isthmus structures in a simulated complex root canal system consisting of 2 curved root canals by Laser-activated irrigation (LAI, AdvErl Evo, Morita) and mechanical activation techniques. METHODS: A 3D-printed root canal model with 2 parallel root canals (60°-curvature, radius 5 mm, dimension 25/.06) with a total length of 20 mm connected via isthmuses (2.5 × 0.4 × 0.2 mm) at 5 mm and 8 mm from the apical endpoint and with lateral canals (diameter 0.2 mm) in all directions at 2, 5, and 8 mm from the apex was filled with a colored biofilm-mimicking hydrogel. Irrigation protocols under continuous irrigation with distilled water (3 × 20s per root canal; 3 ml/20s; n = 20) included conventional needle irrigation (=NI); manual agitation (=MA, gutta-percha point 25/.06); EndoActivator (=SAI-EA, 25/.04); EDDY (=SAI-E, 25/.04); ultrasonically-activated irrigation (=UAI) and LAI (Er:YAG-laser; P400FL tip at canal entrance; 25pps, 50 mJ, 300µs). Removal of the hydrogel was determined as a percentage via standardized photos through a microscope. Statistical analysis was performed using Kruskal-Wallis and Conover tests (P = .05). RESULTS: Laser-activated irrigation (LAI) was associated with the greatest removal of hydrogel from the entire root canal system (P < .05), followed by SAI-E. No significant differences were reported for the coronal isthmus between LAI, SAI-E, NI, and MA (P > .05), but inferior results for SAI-EA and UAI (P < .05). In the apical isthmus, all techniques outperformed UAI (P < .05), with LAI, SAI-E, and NI showing the best results (P < .05). CONCLUSIONS: Laser-activated irrigation (LAI) was superior to other irrigation techniques in the entire root canal system. SAI-E and NI performed comparable to LAI in the isthmuses.

BlueShaper: un nuevo sistema multialeación para la instrumentación mecanizada en endodoncia: comunicación breve / BlueShaper: a new multialloy system for mechanized instrumentation in endodontics: brief communication

El objetivo de esta comunicación es describir y analizar el sistema BlueShaper para la preparación quirúrgica mecaniza- da de los conductos radiculares. El sistema dispone de un set básico de 4 limas: Z1, Z2, Z3 y Z4, con un D0 de 0,14 mm, 0,17 mm, 0,19 mm y 0,25 mm respectivamente y conicidad variable que oscila entre el 2 y 10 %. La lima Z1 posee una aleación Pink, que le confiere mayor resistencia a la torsión y una gran capacidad de corte. Las limas Z2, Z3 y Z4 presentan una aleación Blue que aumenta la resistencia a la fatiga cíclica e incrementa su flexibilidad. Para conductos radiculares más amplios se incluyen, además, las limas Z5, Z6 y Z7. La empresa comer- cializa conos de gutapercha BlueShaper que se corresponden con las limas Z3, Z4, Z5, Z6 y Z7. El sistema de limas mul- tialeación Blue Shaper podría considerarse como un nuevo aporte clínico para la preparación mecánica de los conductos radiculares (AU)

The aim of this communication was to describe and analyze the BlueShaper system for the mechanized surgical preparation of root canals. The system has a basic set of 4 files: Z1, Z2, Z3 and Z4, with 0.14 mm, 0.17 mm, 0.19 mm and 0.25 mm DO respective- ly, and variable conicity ranging between 2 and 10 %. Z1 file has a Pink alloy, which gives it greater resistance to torsion and great cutting capacity. The Z2, Z3 and Z4 files feature a Blue alloy that increases resistance to cyclic fatigue and increases their flexibility. For larger root canals, the Z5, Z6 and Z7 files are also included. The company supplies specific BlueShaper ́s gutta-percha cones for Z3, Z4, Z5, Z6 and Z7 files. The BlueShaper multialloy file system could be consid- ered as a new clinical contribution for the mechanical prepa- ration of root canals (AU)

Shaping ability of non-adaptive and adaptive core nickel-titanium single-file systems with supplementary file in ribbon-shaped canals analysed by micro-computed tomography.

This study compared shaping ability between two single-file systems and before/after using supplementary file in untouched area, volume of removed dentin, maximum cut depth (the highest cut depth by main file) and remaining thinnest dentin (the thinnest root dentin after preparation). Ribbon-shaped distal canals of mandibular molars were prepared with non-adaptive core (WaveOne Gold) or adaptive core (XP-endo Shaper) files (n = 15/group) and additionally prepared with a supplementary file (XP-endo Finisher), and the shaping ability was investigated using micro-computed tomography. XP-endo Shaper group demonstrated significantly less overall untouched area than WaveOne Gold group (38.21 ± 6.98% vs. 47.68 ± 9.16%) (p < 0.05). No significant difference was detected between XP-endo Shaper and WaveOne Gold groups in volume of removed dentin (1.85 ± 0.53 vs. 1.66 ± 0.33 mm3 ), maximum cut depth (0.10-0.28 vs. 0.10-0.29 mm) and remaining thinnest dentin (0.66-0.80 vs. 0.78-0.88 mm). Supplementary XP-endo Finisher treatment significantly decreased untouched area (11%-23% reduction) (p < 0.05) with minimally cut root dentin (0.01-0.02 mm).

Effect of Glycolic Acid, Maleic Acid, and EDTA in the Removal of Smear Layer from Root Canal Dentin

ABSTRACT Objective: To assess the efficacy of 5% Glycolic Acid (GA), 17% ethylenediaminetetraacetic acid (EDTA) and 7% maleic acid (MA), in removing the smear layer (SL). Material and Methods: For the experiment, forty single-rooted human teeth were selected. To perform the chemo‑mechanical preparation, the root canals were instrumented to an apical size of #30, along with simultaneous irrigation of 2.5% NaOCl. The samples were allotted to the experimental groups based on the final irrigating solution (n=10): (1) The GA group: 05%, (2) the EDTA group: 17%, (3) the MA group: 7%, and (4) the control group: Distilled water. The teeth were evaluated for the presence or absence of SL using SEM. Results: Comparing the 5% GA, 7% MA and 17% EDTA groups, no statistically significant differences were found at the coronal and middle thirds (p>0.05). However, in the apical third, MA had greater efficacy than EDTA (p=0.002) and GA (p=0.041), with a significant difference in the SL removal, while there was no significant difference between the latter (p=0.148). Conclusion: Thus, it was concluded that 7% maleic acid as a final irrigating solution is more efficacious than 17% EDTA and 5% glycolic acid in eliminating the smear layer from the apical portion of the root canal.

Endodontic file separation and its management among dentists in Punjab, Pakistan: a cross-sectional study

The study aimed to find the incidence and awareness of endodontic instrument separation and its management among dental house officers, postgraduate trainees, demonstrators, consultants, and general dentists. Methods: This online questionnaire-based cross-sectional study was conducted with the approval of the IRB in private and public dental hospitals and dental clinics in Punjab. The authors developed the survey tool, which comprises 24 closed-ended items regarding demographics, the incidence of file separation, and awareness about its management. The data were analyzed using IBM SPSS version 24. The Chi-Square Test was used to compare percentages of categorical variables. Results: Postgraduate trainees experienced the most instrument separations (43.6%), made the most retrieval attempts (49.2%), and experienced the most secondary errors during retrieval (52.1%) (p<0.001). Around four out of ten respondents always informed the patients (39.6%) and department (41.6%) about errors. Manual files (69.8%), stainless steel files (75.8%), and short files (60.4%) were more frequently separated, and the most frequent cause was older fatigue files (57.7%). Manual files were more frequently broken in public dental institutes (p=0.003). Two-thirds of the file separations (72.5%) occurred during cleaning and shaping in the apical third of molars (65.1%), especially in mesiolingual canal (56.4%). Bypass attempt was the most common in symptomatic teeth (47.7%). Conclusions: Preventive approaches such as limiting file reuse and constructing a glide path can reduce the occurrence of file separation. Operators should be familiar with the number of uses of the instrument before fatigue and should be trained through workshops and refresher courses

Preparos endodônticos minimamente invasivos: construção de bases científicas / Minimally invasive endodontic prepararions: the construction of scientific bases

O conceito de Endodontia Minimamente Invasiva é amplo, e envolve não só a realização de acessos, mas também o uso de instrumentos com conicidades reduzidas ou geometrias inovadoras. Buscando avaliar se as estratégias minimamente invasivas adotadas apresentam vantagens frente aos tratamentos tradicionais, a presente tese foi dividida em três estudos. O estudo 1 avaliou a preservação da dentina perirradicular e o alargamento da porção apical dos canais de molares inferiores com instrumentos TruNatomy e ProTaper Gold. Para isso, vinte molares inferiores foram microtomografados, pareados e distribuídos em 2 grupos. No grupo ProTaper Gold, os canais mesial e distal foram preparados até os instrumentos F2 e F3, respectivamente, enquanto no grupo TruNatomy, os canais mesial e distal foram ampliados até os instrumentos prime e medium, respectivamente. Após um novo escaneamento, os parâmetros de instrumentação foram calculados. Os dados foram analisados pelos testes de Mann-Whitney, T Student e escalonamento multidimensional não-métrico. Não foram encontradas diferenças entre os grupos em relação à área não preparada e redução de espessura de dentina. O grupo ProTaper Gold removeu mais dentina que o TruNatomy no terço coronal das raízes mesiais. O estudo 2 avaliou a formação de microtrincas dentinárias em molares inferiores acessados de forma ultraconservadora (UltraAC), instrumentados com Reciproc e XP-Endo Shaper. Quarenta molares inferiores foram microtomografados, pareados e distribuídos em 4 grupos de acordo com o tipo de cavidade de acesso e protocolo do sistema de instrumentação: tradicional/Reciproc; tradicional/XP-endo Shaper; UltraAC/Reciproc e UltraAC/XP-endo Shaper. Após os preparos dos canais, os dentes foram escaneados novamente e as imagens transversais das raízes mesiais e distais, do nível da furca ao ápice foram avaliadas com o objetivo de identificar a presença de microtrincas dentinárias. Em todos os grupos, as microtrincas verificadas nas imagens pós-operatórias já estavam presentes no exame pré-operatório. O estudo 3 avaliou a influência de instrumentos com o mesmo diâmetro de ponta e diferentes conicidades no percentual de área não preparada e volume de dentina removida após o preparo dos canais mesiovestibular e distovestibular de molares superiores com ou sem o canal mesiovestibular 2 (MV2). Vinte e dois molares superiores foram selecionados, microtomografados, pareados e classificados em dois grupos, de acordo com a anatomia das raízes: dentes com MV2 e dentes sem MV2. Após o acesso, os canais radiculares foram preparados com instrumentos 25/.01, 25/.03, 25/.05, 25/.06 e 25/.08v. Os dentes foram submetidos a novos escaneamentos por micro-CT após preparo com cada instrumento descrito anteriormente. Os dados foram analisados usando o Modelo linear generalizado misto e aproximação de Kenward-Roger para testes Wald F. Em dentes com e sem canais MV2, a porcentagem de área não preparada apresentou uma diminuição significativa ao longo do tratamento após cada instrumento utilizado e a porcentagem de dentina removida apresentou um aumento significativo ao longo do tratamento. Com base nos estudos, concluiu-se que as estratégias minimamente invasivas adotadas não apresentaram vantagens frente aos tratamentos tradicionais(AU)

The concept of Minimally Invasive Endodontics is broad, and involves not only the realization of accesses, but also the use of instruments with reduced tapers or innovative geometries. Seeking to assess whether the minimally invasive strategies adopted have advantages over traditional treatments, this thesis was divided into three studies. Study 1 evaluated the preservation of periradicular dentin and enlargement of the apical portion of the mandibular molar canals prepared with TruNatomy and ProTaper Gold instruments. For this, twenty lower molars were microtomography, paired and divided into 2 groups. In the ProTaper Gold group, the mesial and distal canals were prepared up to the F2 and F3 instruments, respectively, while in the TruNatomy group, the mesial and distal canals were prepared up to the prime and medium instruments, respectively. After a new scan, the instrumentation parameters were calculated. Data were analyzed by Mann-Whitney, T Student and non-metric multidimensional scaling tests. No differences were found between groups regarding unprepared area and dentin thickness reduction. The ProTaper Gold group removed more dentin than TruNatomy in the coronal third of the mesial roots. Study 2 evaluated the formation of dentinal microcracks in mandibular molars accessed by ultraconservative cavites (UltraAC), instrumented with Reciproc and XP-Endo Shaper. Forty lower molars were microtomography, paired and divided into 4 groups according to the type of access cavity and instrumentation system protocol: traditional/Reciproc; traditional/XP-endo Shaper; UltraAC/Reciproc and UltraAC/XP-endo Shaper. After the root canal preparations, the teeth were scanned again and the transverse images of the mesial and distal roots, from the furcation level to the apex, were evaluated in order to identify the presence of dentinal microcracks. In all groups, the microcracks seen in the postoperative images were already present in the preoperative examination. Study 3 evaluated the influence of instruments with the same tip diameter and different tapers on the percentage of unprepared area and volume of dentin removed after preparation of the mesiobuccal and distobuccal canals of maxillary molars with or without the mesiobuccal canal 2 (MV2). Twenty-two maxillary molars were selected, microtomography, paired and classified into two groups, according to root anatomy: teeth with MV2 and teeth without MV2. After access, the root canals were prepared with instruments 25/.01, 25/.03, 25/.05, 25/.06 and 25/.08v. The teeth were rescanned by micro-CT after preparation with each instrument described above. Data were analyzed using the Generalized Linear Mixed Model and Kenward-Roger approximation for Wald F tests. In teeth with and without MV2 canals, the percentage of unprepared area showed a significant decrease throughout the treatment after each instrument used and the percentage of removed dentin showed a significant increase during treatment. Based on the studies, it was concluded that the minimally invasive strategies adopted did not present advantages over traditional treatments(AU)

Alargamento do forame como complemento no tratamento endodôntico para regeneração de uma lesão periapical extensa: relato de caso / Foraminal enlargement as a complement in the endodontic treatment for the regeneration of an extensive periapical lesion. A case report

Introdução: O alargamento do forame refere-se ao alargamento mecânico intencional do forame para reduzir a carga bacteriana em uma área afetada frequentemente por infecções endodônticas além do limite da constrição apical. Objetivo: O objetivo do presente relato de caso é apresentar a técnica de alargamento do forame de um dente com lesão periapical extensa, como complemento do tratamento endodôntico e alternativa precoce à microcirurgia periapical. Métodos: É apresentado o caso de um incisivo lateral superior endodonticamente tratado, com uma extensa lesão periapical associada. Devido à história clínica e radiográfica, tempo decorrido desde o tratamento endodôntico inicial e alta probabilidade de áreas de reabsorção apical com biofilme extrarradicular, o retratamento endodôntico com alargamento do forame foi indicado como primeira opção, adiando a indicação de cirurgia endodôntica de acordo com a evolução. Resultados: Na avaliação de acompanhamento de dois anos, por exame de imagem, observou-se evolução clínica favorável ao retratamento, com aumento total da densidade óssea. O procedimento cirúrgico endodôntico complementar foi descartado. Conclusão: O alargamento do forame é uma alternativa complementar viável em casos de periodontite apical de longa duração com suspeita de biofilme no nível do forame. Pode ser considerado uma opção antes da indicação de retratamento endodôntico cirúrgico (AU).

Introduction: Foraminal enlargement refers to intentional mechanical enlargement of the foramen to reduce the bacterial load in an area frequently affected by endodontic infections beyond the limits of the apical constriction. The objective of this case report is to present the foraminal enlargement technique of a tooth with an extensive periapical lesion as a complement in the endodontic treatment and an early alternative to periapical microsurgery. Materials and methods: The case is presented of an endodontically treated upper lateral incisor with an extensive associated periapical lesion. Due to the clinical and radiographic history, the time elapsed since the initial endodontic treatment, and the high probability of areas of apical resorption with extra-radicular biofilm, endodontic retreatment with foraminal enlargement was indicated as the first option, postponing the indication for endodontic surgery according to evolution. Results: In the follow-up appointment at 2 years, a favorable clinical imaging evolution of retreatment was observed, with a total increase in bone density. The complementary endodontic surgical procedure was discarded. Conclusion: Foraminal enlargement is a viable complementary alternative in cases of long-term apical periodontitis with suspicion of biofilm at the foramen level. It can be considered an option before the indication of surgical endodontic retreatment (AU).