Using manual versus mechanized glide path instruments and ProTaper Gold versus ProTaper Next systems in curved canals: micro-CT study

Abstract The aim of this study was to evaluate the root canal shaping effect of ProTaper Gold (PTG) versus ProTaper Next (PTN) instrumentation systems, and of a manual #15 K-type file (K15) versus the ProGlider (PG) mechanized instrument for glide path creation, in severely curved mesial canals. Twenty-four mandibular molars with two separate mesial canals were anatomically matched using computed tomographic scanning, and then divided into two groups (n=12) according to the glide path instrument used, either K15 or PG. In all teeth, the PTG system was used to prepare the mesiobuccal canal, and the PTN, the mesiolingual canal. The teeth were scanned by computed microtomography, before and after root canal preparation, and the values of the initial volume, final volume, volumetric variation, untouched walls, and canal transportation variables were determined. The data were analyzed using the two-way ANOVA test, and the Tukey test for multiple comparisons. There was no significant difference among the study groups regarding volumetric variation or root canal transportation, either in the cervical, middle or apical thirds, or in the entire root canal (p>0.05). In the apical third, the percentage of untouched walls was significantly higher in groups using K15 than in those using PG (p<0.05), namely 33.144% and 23.285%, respectively, irrespective of the instrumentation system. In the other regions, there was no difference between K15 and PG regarding this variable. It was concluded that PG was associated with a lower rate of untouched walls in the apical region than K15.

Root canal curvature influences uncontrolled removal of dentin and cleaning efficacy after ultrasonic activation

Abstract This study evaluated the correlation between root canal curvature and the effects of ultrasonic irrigation in the following parameters: volume of uncontrolled dentin removal (UDRVol), maximum depth of dentin defects, removal of accumulated hard tissue debris (AHTD), and canal transportation in prepared curved root canals. Twenty-four human permanent mandibular molars were divided into two groups according to root canal curvature: moderate curvature (MC: mean 25°); and severe curvature (SC: mean 48°). The specimens were scanned using an X-ray microcomputed scanner (Skyscan 1172) before and after cleaning and shaping and after the final irrigation protocol with ultrasonic irrigation. There was a moderate correlation between the degree of root canal curvature and the volume of remaining AHTD (p<0.05) and between the degree of root canal curvature and maximum depth of defects due to uncontrolled removal of dentin (p<0.05). The teeth in the SC group had a greater maximum depth of defects on the dentin wall in the apical third than the teeth in the MC group (p <0.05). Both groups had a significant reduction of AHTD in all canal thirds, but the amount of remaining AHTD in the middle and apical thirds and the whole canal was significantly greater in the SC than in the MC group (p <0.05). Canal transportation was not influenced by the canal curvature in all thirds (p >0.05). This study concluded that root canal curvature affects significantly the uncontrolled removal of dentin and remaining AHTD volume after the final irrigation protocol with ultrasonic irrigation.

Resumo Este estudo avaliou a correlação entre a curvatura do canal radicular e os efeitos da irrigação ultrassônica nos seguintes parâmetros: volume de remoção não controlada de dentina (UDRVol), profundidade máxima do desgaste de dentina, remoção de debris de tecido duro acumulado (AHTD) e transporte em canais radiculares curvos. Vinte e quatro molares inferiores humanos permanentes foram divididos em dois grupos de acordo com a curvatura do canal radicular: curvatura moderada (MC: média de 25°); e curvatura acentuada (SC: média de 48°). Os espécimes foram digitalizados usando um scanner microcomputador de raios X (Skyscan 1172) antes e depois da limpeza e modelagem e após a irrigação ultrassônica. Houve uma correlação moderada entre o grau de curvatura do canal radicular e o volume de AHTD remanescente (p<0,05) e entre o grau de curvatura do canal radicular e a profundidade máxima de defeitos devido à remoção descontrolada de dentina (p<0,05). Os dentes do grupo SC apresentaram maior profundidade máxima de defeitos na parede dentinária no terço apical do que os dentes do grupo MC (p<0,05). Ambos os grupos tiveram uma redução significativa de AHTD em todos os terços do canal, mas a quantidade de AHTD remanescente nos terços médio e apical e em todo o canal foi significativamente maior no grupo SC do que no grupo MC (p <0,05). O transporte do canal não foi influenciado pela curvatura do canal em todos os terços (p > 0,05). Este estudo concluiu que a curvatura do canal radicular afeta significativamente a remoção descontrolada de dentina e o volume remanescente de AHTD após a irrigação ultrassônica.

Extrusão apical de irrigantes em dentes imaturos utilizando diferentes dispositivos de irrigação por pressão negativa / Apical extrusion of irrigants in immature teeth using different negative pressure irrigation devices

Objetivo: O objetivo deste estudo foi avaliar a extrusão apical de irrigantes em dentes imaturos simulados, comparando a irrigação convencional com outros dispositivos de irrigação por pressão negativa. Materiais e Métodos: 48 amostras de dentes imaturos simulados foram montadas em um modelo adaptado para conter o irrigante extravasado e distribuídas igualmente em 4 grupos (n=12) de acordo com o dispositivo de irrigação utilizado: Grupo Irrigação Convencional (IC), Grupo EndoVac (EV), Grupo Pulp Sucker (PS) e Grupo Ivac (IV). As amostras foram irrigadas com 15mL de solução irrigadora, sendo 10mL de NaOCl a 2,5% e 5mL de EDTA a 17% intercalados. As amostras foram pesadas em balança de precisão antes e depois dos procedimentos de irrigação, sendo a diferença entre os pesos final e inicial considerado o volume de irrigante extravasado. Os dados foram coletados e analisados estatisticamente pelos testes de Kruskal-wallis e exato de Fisher. Resultados: Os grupos que utilizaram pressão negativa promoveram significativamente menor volume de irrigante extravasado que o grupo IC (p<0,05), não havendo diferenças significativas quando comparados entre si (p>0,05). Houve diferenças significativas na associação entre os grupos e a extrusão de irrigante, sendo o grupo PS menos associado a extrusão de irrigante (p<0,005). Discussão: Estudos anteriores apontam os dispositivos de pressão negativa como opções seguras diante de extravasamento de irrigantes quando comparados à irrigação convencional. Conclusão: A irrigação convencional promoveu significativamente maior volume de extrusão de irrigante quando comparada aos dispositivos de irrigação por pressão negativa. O sistema PulpSucker mostrou extravasamento de irrigante em um número significativamente menor de amostras.

Aim: The aim of this study was to evaluate the apical extrusion of irrigants in simulated immature teeh, comparing convencional irrigation with other negative pressure irrigation devices. Materials and methods: 48 samples of simulated immature teeth were set up in an adapted model to contain the extravasated irrigant and evenly distributed into 4 groups (n=12) according to the device used: Convencional Irrigation Group (CI), EndoVac Group (EV), Pulp Sucker Group (PS) and Ivac Group (IV). The samples were irrigated with 15mL of irrigant solution, consisting of 10mL NaOCl 2,5% and 5mL EDTA 17%, in na alternating sequence. The samples' weights were measured using a precision scale before and after the irrigation procedures, with the difference between de final and initial weights considered the volume of extravasated irrigant. Data were collected and statistically analyzed by Kruskal-wallis and Fisher exact tests. Results: The groups that used negative pressure devices significantly promoted a lower volume of extruded irrigant than the CI group (p<0,05), with no significant differences between the negative pressure groups (p>0,05). There were signficant differences in the association between the groups and irrigant extrusion, with the PS group showing significantly less association with irrigant extrusion (p<0,005). Discussion: Previous studies have indicated that negative pressure devices are safe alternatives to convencional irrigation when considering irrigant extrusion. Conclusion: Conventional irrigation promoted a significantly greater volume of irrigant extrusion when compared to negative pressure irrigation devices. The PulpSucker system showed irrigant extravasation in significantly fewer samples.

Optimization of automated preparation of long oval-shaped root canals using supplementary instrumentation

Abstract This study compared the preparation of long oval-shaped root canals using WaveOne Gold and XP-endo Shaper systems, both supplemented or not with manual instrumentation. Twenty-four long oval-shaped canals of mandibular incisors were distributed into two groups according to the instrumentation: WaveOne Gold Primary or XP-endo Shaper systems. All root canals were manually instrumented with a size 25 K-file after automated preparation. The specimens were scanned by using a micro-CT device (17.42 µm) before and after automated preparation and manual instrumentation. The increased surface of the root canal and the percentage of untouched areas were assessed. Both WaveOne Gold and XP-endo Shaper systems increased the root canal surface and had similar untouched areas (p>0.05). Supplementary instrumentation increased the surface of the root canal and decreased the untouched walls (p<0.05). WaveOne Gold and XP-endo Shaper systems provided a similar preparation of long oval-shaped canals and manual instrumentation improved their preparation.

Resumo Este estudo comparou o preparo de canais radiculares ovais longos usando os sistemas WaveOne Gold e XP-endo Shaper, ambos complementados ou não com instrumentação manual. Vinte e quatro canais longos e ovais de incisivos inferiores foram distribuídos em dois grupos de acordo com a instrumentação: sistemas WaveOne Gold Primary ou XP-endo Shaper. Todos os canais foram instrumentados manualmente com uma lima K tamanho 25 após preparo automatizado. Os espécimes foram escaneados usando um dispositivo de micro-CT (17,42 µm) antes e após o preparo automatizado e instrumentação manual. O aumento de superfície do canal radicular e a porcentagem de áreas intocadas foram avaliadas. Ambos os sistemas WaveOne Gold e XP-endo Shaper aumentaram a superfície do canal radicular e apresentaram áreas intocadas semelhantes (p>0,05). A instrumentação complementar aumentou a superfície do canal radicular e diminuiu o percentual de áreas intocadas (p <0,05). Os sistemas WaveOne Gold e XP-endo Shaper tiveram o preparo de canais ovais longos semelhantes, e a instrumentação manual melhorou o preparo.

Mechanism of action of Bioactive Endodontic Materials

Abstract A continuous search for bioactive materials capable of supporting the replacement of damaged pulp tissue, with effective sealing potential and biocompatibility, has represented the attention of studies over the last decades. This study involves a narrative review of the literature developed by searching representative research in PUBMED/MEDLINE and searches in textbooks associated with the mechanism of action of bioactive materials (calcium hydroxide, mineral trioxide aggregate (MTA), and calcium silicate cements). The reflective analysis of the particularities of the chemical elements of these materials, considering the tissue and antibacterial mechanism of action, allows a better understanding of the characteristics and similarities in their tissue responses. Calcium hydroxide paste remains the antibacterial substance of choice as intracanal dressing for the treatment of root canal system infections. Calcium silicate cements, including MTA, show a favorable biological response with the stimulation of mineralized tissue deposition in sealed areas when in contact with connective tissue. This is due to the similarity between the chemical elements, especially ionic dissociation, the potential stimulation of enzymes in tissues, and the contribution towards an alkaline environment due to the pH of these materials. The behavior of bioactive materials, especially MTA and the new calcium silicate cements in the biological sealing activity, has been shown to be effective. Contemporary endodontics has access to bioactive materials with similar properties, which can stimulate a biological seal in lateral and furcation root perforations, root-end fillings and root fillings, pulp capping, pulpotomy, apexification, and regenerative endodontic procedures, in addition to other clinical conditions.

Resumo Uma busca contínua de materiais bioativos com capacidade de substituir o tecido pulpar danificado, com efetiva capacidade de selamento e biocompatibilidade, tem representado a atenção e foco de muitos estudos ao longo das últimas décadas. Este estudo envolve uma revisão narrativa da literatura desenvolvida por meio de pesquisas representativas encontradas no PUBMED/MEDLINE e pesquisas em livros didáticos associadas ao mecanismo de ação de materiais bioativos (hidróxido de cálcio, agregado de trióxido mineral (MTA) e cimentos de silicato de cálcio). A presente análise reflexiva das particularidades dos elementos químicos destes materiais bioativos, considerando o mecanismo de ação tecidual e antibacteriano, possibilita um melhor entendimento das características e similaridades no comportamento tecidual. A pasta de hidróxido de cálcio continua sendo a substância antibacteriana de escolha como medicação intracanal para o tratamento das infecções do sistema de canais radiculares. Este fato se deve a disponibilidade química de íons cálcio e hidroxila do hidróxido de cálcio aos tecidos, e a inibição enzimática bacteriana. Os cimentos de silicato de cálcio, dentre os quais inclui o MTA, apresentam uma resposta biológica favorável ao estímulo à deposição de tecido mineralizado nas áreas seladas e em contato com tecido conjuntivo. Este fato é decorrente da similaridade entre os elementos químicos, em especial devido a dissociação iônica, ao potencial estímulo de enzimas teciduais, e a contribuição com um meio alcalino decorrente do pH destes materiais. O comportamento dos materiais bioativos, em especial o MTA e os novos cimentos de silicato de cálcio na atividade de selamento biológico mostraram efetivos. A endodontia contemporânea atualmente conta com o potencial de materiais bioativos com propriedades análogas capaz de estimular o selamento biológico em perfurações radiculares laterais e de furca, em obturações radiculares, capeamento pulpar, pulpotomia, apicificação e procedimentos endodônticos regenerativos, além de outras condições clínicas.

Remoção de obturações endodônticas de Endosequence BC/CPoint em canais radiculares curvos usando instrumentos rotatórios ou reciprocantes / Removal of Endosequence BC/CPoint endodontic fillings in curved root canals using rotary or reciprocating instruments

Objetivo: O presente estudo usou micro-CT para avaliar a quantidade de material obturador remanescente em canais radiculares curvos que tinham sido obturados com cimento Endosequence BC/Cpoint ou com cimento AH/ guta-percha, depois do retratamento utilizando instrumentos rotatórios ou reciprocantes. Métodos: Sessenta canais mesiovestibulares de molares superiores foram instrumentados até MTwo #35.04. As amostras foram randomicamente alocadas em quatro grupos (n=15): os canais do G1 e G2 foram obturados com AH/guta-percha, e os canais do G3 e G4 foram obturados com BC/Cpoint. O material obturador foi removido usando instrumentos rotatórios ou reciprocantes ­ G1 e G3: R25 Reciproc + reinstrumentação com R40; e G2 e G4: Sistema ProTaper Universal Retratamento + reinstrumentação com MTwo 40.06. Micro-CTs foram usadas para medir a quantidade de material obturador remanescente (mm3 ) para o canal inteiro e para cada terço, em dois momentos: 1) após a remoção do material obturador; e 2) após a reinstrumentação. Resultados: Após a remoção do material obturador, BC/CPoint permaneceu mais dentro do canal do que AH/guta-percha quando o canal inteiro (29,92% x 19,25%, p=0,0290) e o terço apical foram analisados. Após a reinstrumentação, BC/CPoint permaneceu mais do que AH/guta-percha somente no terço apical. Protocolos de tratamento com instrumentos rotatórios ou reciprocantes removeram material obturador sem diferença para AH/guta-percha (G1 e G2: p> 0,05) e BC/CPoint (G3 e G4: p> 0,05). Conclusões: BC/Cpoint é mais difícil de ser removido de canais radiculares curvos do que AH/guta-percha. Instrumentos rotatórios e reciprocantes têm habilidade similar na remoção de material obturador (AU).

Objective: This study used micro-CT to evaluate the amount of remaining filling material in curved root canals obturated with Endosequence BC Sealer/Cpoint or AH/gutta-percha after a rotary or reciprocating retreatment. Methods: Sixty mesiobuccal canals of maxillary molars were instrumented up to MTwo #35.04. Samples were randomly assigned to four groups (n=15): canals from G1 and G2 were filled with AH/gutta-percha, and canals from G3 and G4 were filled with BC/Cpoint. Filling material was removed using rotary or reciprocating instruments: G1 and G3: R25 Reciproc + re-shaping with R40; and G2 and G4: ProTaper Universal Retreatment system + re-shaping with MTwo 40.06. Micro-CT was used to measure the remaining amount of filling material (mm3 ), for the whole canal, and for each third, in two moments: 1) after filling removal and 2) after canal re-shaping. Results: After filling removal, BC/CPoint remained more into the canal than AH/Gutta-percha when the whole canal (29.92% x 19.25%, p = 0.0290) and the apical third were analyzed. After re-shaping, BC/CPoint remained more than AH/Gutta-percha only in the apical third. Rotary or reciprocating retreatment protocols removed filling material without difference for AH/gutta-percha (G1 and G2: p > 0.05) and BC/CPoint (G3 and G4: p > 0.05). Conclusion: BC/Cpoint is more difficult to be removed from curved root canals than AH/gutta-percha. Reciprocating and rotary instruments have similar ability to remove filling material (AU).

Resistência à fadiga cíclica dos instrumentos Reciproc e Mtwo nos movimentos rotatório e reciprocante / Resistance to cyclic fatigue of Reciproc and Mwto files on continuous rotation and reciprocating movements

Objetivo: O objetivo do presente estudo foi avaliar a influência da liga (NiTi convencional e M-Wire) e do movimento (reciprocante e rotação contínua) na resistência à fadiga cíclica. Métodos: Quinze limas Reciproc R25 (VDW GmbH, Munique, Alemanha) foram usadas em movimento reciprocante (MR), enquanto trinta limas Mtwo 25.07 (VDW GmbH, Munique, Alemanha) foram usadas em MR (n=15) ou em rotação contínua (RC) (n=15). Os instrumentos foram submetidos a ensaios dinâmicos movidos por motor elétrico, que permitiram reproduzir o movimento de pecking motion, a 300rpm de velocidade. Os instrumentos simularam a instrumentação de um canal radicular curvo com 40o e 5mm de raio de curvatura. A fratura dos instrumentos foi detectada por um sensor digital, e o tempo e o número de ciclos foram registrados. Os dados foram analisados estatisticamente pelos testes ANOVA e de Tukey (p<0,05). Resultados: Os instrumentos Reciproc R25 movidos por MR alcançaram número significativamente maior (p<0,05) de ciclos antes da fratura (1.777,68±334,2 ciclos), quando comparados aos instrumentos MT 25.07 movidos por MR (610,67±126,3 ciclos) ou RC (432,23±183,2 ciclos). Conclusões: O movimento reciprocante mostrou resistência à fadiga cíclica significativamente maior, e os instrumentos de NiTi M-Wire apresentaram maior resistência à fadiga cíclica do que os instrumentos rotatórios de NiTi convencional (AU).

Objective: The aim of present study was to evaluate the influence of alloy (conventional NiTi and M-Wire NiTi) and movement (reciprocating movement and continuous rotation) on resistance to cyclic fatigue. Methods: Fifteen Reciproc R25 files (VDW GmbH, Munich, Germany) were used in reciprocation motion (RM), while thirty MTwo 25/.07 files (VDW GmbH, Munich, Germany) were used either in RM (n=15) or in continuous rotation (CR) (n=15). The files were submitted to dynamic assays device moved by electric engine that allowed the reproduction of pecking motion under 300 rpm of speed. The files act simulating the instrumentation of a curved root canal with 40º and 5-mm of curvature radius. The fracture was detected by the device sensor and the time and number of cycles were obtained. Data were statistically analyzed by ANOVA and Tukeys tests (p<0.05). Results: The Reciproc R25 instruments moved by RM reached significantly higher number (p<0.05) of cycles before fracture (1777.68 ± 334.2 cycles) when compared with MTwo 25/.07 instruments moved by RM (610.67 ± 126.3 cycles) or CR (432.23 ± 183.2 cycles). Conclusions: The reciprocation motion showed significantly greater cyclic fatigue resistance and the M-Wire NiTi files showed higher cyclic fatigue resistance than conventional NiTi rotary files (AU).

Knowledge about Coronavirus disease 19 (COVID-19) and its professional repercussions among Brazilian endodontists

Abstract The aim of this study was to assess Brazilian endodontists' level of knowledge about the coronavirus disease (COVID-19) and examine its professional repercussions. The link to the online survey that was created for this study was shared with Brazilian endodontists through social networking applications. The questionnaire contained questions that pertained to COVID-19 and its impact on dental practice. The collected data were analyzed using t-test, chi-square analysis, and analysis of variance, and the level of significance was set at 0.05. A total of 2,135 participants responded to the questionnaire, and all five Brazilian regions were represented in the sample. A total of 98.50% of endodontists reported that dental procedures can transmit COVID-19. Complete social distancing was practiced by 96.68% of the participants, and approximately 25% knew someone who had COVID-19. Moreover, in their daily practice, 72.13% of them implemented biosecurity measures that are ineffective in preventing COVID-19. Furthermore, 91.7% of them reportedly suspended elective dental procedures. Only 55.69% of them reported that they performed only emergency procedures in their workplaces. Those who believed that COVID-19 cannot be transmitted during dental procedures were less knowledgeable about the symptoms of COVID-19 (p = 0.0095). Endodontists who believed that personal protective equipment cannot prevent contamination were more knowledgeable about the symptoms of COVID-19 than their counterparts (p = 0.0003). The participating Brazilian endodontists demonstrated adequate knowledge about the risk of contamination during dental procedures and the main symptoms of COVID-19. Only some professionals reported providing emergency dental care during the pandemic.

Torsional fatigue strength of reciprocating and rotary pathfinding instruments manufactured from different NiTi alloys

Abstract To evaluate the torsional properties of engine-driven pathfinding instruments manufactured from different NiTi alloys - R-Pilot (tip size 12.5;.04 taper; M-Wire) and One G (tip size 14;.03 taper; Conventional NiTi). A total of 40 NiTi instruments from engine-driven pathfinding instruments (n = 20) were used. The torsion tests followed ISO 3630-1 (1992). Three millimeters of each instrument tip was fastened to a small load cell by a lever arm linked to the axis of torsion. During the test, the torsion testing machine software measured the maximum torsional strength and angle of rotation (0) before instrument failure. The fractured surface of each instrument was assessed by scanning electron microscopy (SEM). In addition, a supplementary examination was performed to measure the cross-sectional area and the metal mass volume of each instrument 3 mm from the tip. Data were analyzed using a t-test, with significance level set at 5%. R-pilot had significantly higher torsional strength than did One G (p < 0.05). Regarding the angle of rotation to fracture, One G had higher angles than did R-Pilot (p < 0.05). The supplementary examination showed that R-Pilot had the highest cross-sectional area and volume of metal mass at 3 mm from the tip (p < 0.05). R-pilot (M-Wire NiTi alloy) had a significantly higher torsional strength and One-G (superelastic NiTi alloy) had the highest angle of rotation to fracture.

Comparison of rRNA-based reverse transcription PCR and rDNA-based PCR for the detection of streptococci in root canal infections

Abstract Objective The rDNA-based method is unable to distinguish between alive and dead cells. Alternatively, bacterial viability can be assessed by molecular methods based on ribosomal RNA (rRNA). Therefore, this study aimed to detect viable streptococci in root canal samples using rRNA-based reverse transcription polymerase chain reaction (RT-PCR), compared to an rDNA-based PCR assay. Methodology Microbiological root canal samples were obtained from 32 teeth with primary endodontic infections before (S1) and after chemomechanical preparation (S2), and after removal of intracanal medication (S3). RNA and DNA were extracted, and complementary DNA (cDNA) was synthesized from RNA using RT reaction. cDNA and genomic DNA were subjected to PCR with primers complementary to the 16S rRNA sequences of Streptococcus spp. McNemar's test was used to compare the detection rate of both assays (P<0.05). Results Streptococci were detected in 28.12% (9/32) and 37.5% (12/32) of S1 samples using rRNA- and rDNA-based PCR assays, respectively. In contrast, they were detected in only 6.25% (2/32) of S2 samples using rRNA-based RT-PCR, compared to 15.62% (5/32) using rDNA-based PCR. Finally, in S3 samples, streptococci were not detected by rRNA, whereas rDNA-based PCR still detected the bacteria in 12.5% (4/32) of the samples. The total number of PCR-positive reactions in the rDNA-based PCR was higher than in the rRNA-based assay (P<0.05). Conclusions The rRNA-based RT-PCR showed a lower detection rate of streptococci when compared to the rDNA-based PCR, suggesting that the latter may have detected dead cells of streptococci in root canal samples.

Influence of cross-section and number of use in cyclic fatigue resistance of rotary instruments

Aim: The aim of present study was to evaluate if the cross-section and the number of use have influence in cyclic fatigue resistance of rotary files. Methods: K3 Endo (group K) and EndoSequence (group E) files, 25/.04, 25 mm, were subdivided into 3 subgroups (n=12) according to the number of uses, 1, 3 and 5 uses, totalizing 72 files. The files were submitted to dynamic assays device moved by an electric engine, using 300 rpm of speed that permitted the reproduction of pecking motion. The files run within a temperate steel ring's groove, simulating an instrumentation of a curved root canal with 40-degrees and 5-mm of curvature radius. The fracture of file was detected by sensor of device and the time and the number of cycles was acquired. The data were analyzed statistically by two-way ANOVA (p<0.05). Results: There were no statistical significant differences in regard to the number of uses (p>0.05). K3 Endo files showed greater resistance to cyclic fatigue than EndoSequence instruments (p<0.01). Conclusion: It may be concluded that the cross-section of instruments presented significant influence in cyclic fatigue resistance and the number of uses up to 5 times had no influence in cyclic fatigue resistance in both NiTi rotation systems evaluated

Effect of rewetting solutions on micropush-out dentin bond strength of new bioceramic endodontic material

Abstract To evaluate the influence of rewetting solutions on bond strength to root dentin of conventional gutta-percha (GP) or niobium phosphate glass-based gutta-percha (GNb) associated with a bioceramic sealer. The root canals of 80 human mandibular premolars were prepared using nickel-titanium instruments and irrigation with sodium hypochlorite and EDTA. The teeth were randomly divided into four groups according to the gutta-percha used: GNb or GP associated with EndoSequence BC Sealer (BC) and the solution for rewetting dentin before filling (distilled water; phosphate buffer saline solution - PBS; simulated body fluid - SBF; or no solution). The root canals were filled with a single cone using warm vertical condensation. Micropush-out bond strengths associated with the filling materials in slices from middle root thirds was determined 30 days after root filling. The failure mode was analyzed with stereoscopic lens. The data were statistically analyzed by two-way ANOVA and Holm-Sidak test (p < 0.05). There was significant difference in the types of gutta-percha (p < 0.001) and in the different rewetting solutions (p = 0.003). The interaction between gutta-percha and rewetting solutions was not significant (p = 0.53). The SBF solution provided an increase in bond strength for both gutta-percha solutions. The GNb+BC (3.42 MPa) association increased bond strength when compared with GP+BC (2.0 MPa). The use of SBF as a dentin rewetting solution increased bond strength in the groups studied. Association of GNb with bioceramic sealer was beneficial, increasing the bond strength to dentin when compared with the association with GP.

Ions Release and pH of Calcium Hydroxide-, Chlorhexidine- and Bioactive Glass-Based Endodontic Medicaments

Abstract This study evaluated pH and release of calcium, sodium and phosphate ions from different medications in human dentin. Fifty premolars were prepared and randomly divided into groups: (CHX) - 2% chlorhexidine gel; (CHX + CH) - CHX + calcium hydroxide PA; (CH) - CH + propylene glycol 600; (NPBG) - experimental niobium phosphate bioactive glass + distilled water; (BG) - bioactive glass (Bio-Gran) + distilled water. The specimens were immersed in deionized water and the pH variations were measured. The quantification of ions in the solutions was made by inductively coupled plasma - atomic emission spectroscopy (ICP/AES) at 10 min, 24 h, 7, 14, 21 and 30 days. The results were analyzed by ANOVA and Tukey`s test, with a significance level of 5%. CH had the highest level of calcium ions release at 30 days, while CHX and BG released more sodium ions. BG, NPBG and CHX released a higher amount of phosphate ions. The pH of CH was significantly higher compared with the other groups. CH favored the greatest increase of pH and calcium ions release. The bioactive glasses released more sodium and phosphate ions and presented an alkaline pH immediately and after 30 days.

Resumo Este estudo avaliou o pH e a liberação de íons cálcio, sódio e fosfato de diferentes medicamentos em dentina humana. Cinquenta pré-molares foram preparados e divididos aleatoriamente em grupos: (CHX) - clorexidina gel 2%; (CHX + CH) - CHX + hidróxido de cálcio PA; (CH) - CH + propilenoglicol 600; (NPBG) - vidro experimental nióbio fosfato bioativo + água destilada; (BG) - vidro bioativo (Bio-Gran) + água destilada. Os espécimes foram submersos em água deionizada e as variações de pH foram mensuradas. A quantificação dos íons nas soluções foi feita por espectrometria de emissão atômica com plasma indutivamente acoplado (ICP - AES) nos tempos de 10 min, 24 h, 7, 14, 21 e 30 dias. Os resultados foram analisados por ANOVA e teste Tukey, com um nível de significância de 5%. Verificou-se que CH a teve a maior liberação íons de cálcio ao final de 30 dias, enquanto CHX e BG liberaram mais íons de sódio. BG, NPBG e CHX apresentaram a maior liberação de íons fosfato. O pH de CH foi significativamente maior em comparação com os outros grupos testados. O grupo CH aumentou o pH e a liberação de íons cálcio. Os vidros bioativos obtiveram uma maior liberação de íons sódio e fosfato e apresentaram pH alcalino imediato e ao final de 30 dias.

Effect of different torques in cyclic fatigue resistance of K3 rotary instruments

Aim: To assess the effect of different torque values on cyclic fatigue resistance of K3 rotary nickel-titanium (NiTi) files. Methods: Eighty K3 files, size 25 mm, taper 0.04 were divided in 4 groups according to different torques (0.5, 1, 2 and 6 Ncm) and were submitted to a cyclic fatigue test. This test was performed with a device that allowed the file to rotate inside a stainless steel artificial curved canal, simulating the pecking motion. Files rotated until fracture occurred and time to failure was recorded in seconds with a stopwatch. Data were analyzed by ANOVA and Tukey tests (p<0.05). Results: All groups were compared and only the group of 6 N.cm showed statistically significant difference (p=0.0002). Conclusions: For #25.04 K3 files, the evaluated torques up to 2 N.cm had no influence on cyclic fatigue resistance. Using 6 N.cm torque value resulted in lower resistance to cyclic fatigue.

Ex vivo evaluation of three instrumentation techniques on E. faecalis biofilm within oval shaped root canals

The objective of the present study was to assess the effectiveness of reciprocating instrumentation in disinfecting oval-shaped root canals infected with Enterococcus faecalis. Forty-five human lower premolars were infected with a culture of E. faecalis (ATCC 29212) for 28 days. Five other teeth that were neither contaminated nor instrumented were used as controls. The 45 specimens were divided into three experimental groups (n = 15) based on the root canal preparation technique used: manual (K-type, Dentsply Maillefer, Ballaigues, Switzerland); rotary (MTwo, VDW GmbH, Munich, Germany); and reciprocating (Reciproc R50, VDW GmbH, Munich, Germany) instruments. During chemomechanical preparation, 21 mL of 2.5% NaOCl was used as the irrigating solution. Microbiological sampling was performed before (S1) and immediately after (S2) the chemomechanical preparation using sterilized paper points. Specimens were then cleaved, and 0.02 g of dentine chips was collected from the root thirds to verify the presence of microorganisms in dentinal tubules. All three preparation techniques reduced the number of microorganisms in the root canal lumen and dentine chips from the root thirds, but no significant differences were observed between the three groups (p > 0.05). Reciprocating instrumentation with Reciproc R50 was effective in reducing the number of microorganisms within the root canal system. Although this technique involves the use of only one file to perform the root canal therapy, it is as effective as conventional rotary instrumentation in reducing theE. faecalis biofilm from the root canal system. However, further clinical investigations are warranted in order to ratify these results.

Influence of Apical Patency and Cleaning of the Apical Foramen on Periapical Extrusion in Retreatment

This study evaluated the influence of apical patency, root filling removal technique and cleaning of the apical foramen, concerning the amount of debris extruded during root canal retreatment. Forty mandibular incisors were randomly assigned to 4 groups - GIM (n=10), GIIM (n=10), GIPT (n=10) and GIIPT (n=10), which were named according to leaving (I) or not (II) apical patency during canal preparation and filling removal technique (manual - M or ProTaper system - PT). After filling material removal, each specimen of each group had the apical foramen cleaned by sizes 15, 20 and 25 instruments, generating 12 subgroups: GIM15, GIM20, GIM25, GIIM15, GIIM20, GIIM25, GIPT15, GIPT20, GIPT25, GIIPT15, GIIPT20 and GIIPT25. Extruded filling debris was collected by a Milipore filtration system, an HV-durapore, 0.45 µm pore filter with a 25 mm diameter. The filters were weighed before and after the collection on an analytical scale (10–5 g), and the difference was calculated. The mean weight of extruded filling debris was analyzed statistically by Kruskal-Wallis and Friedman ANOVA tests (α=0.05). The mean values found in the groups (in mg) were: GIM (0.95±0.94), GIIM (0.47±0.62), GIPT (0.30±0.31) and GIIPT (0.32±0.44). There was no statistically significant difference among any of the groups or subgroups (p>0.05). ProTaper provided the smallest amount of extruded filling material, regardless of presence or absence of apical patency, followed by manual technique, without and with apical patency. Additional amounts of debris were collected during cleaning of the apical foramen, regardless of the instrument, presence/absence of patency or root filling removal technique.

Este estudo verificou a influência da patência apical, técnica de desobturação e limpeza foraminal na quantidade de material sólido extruído, durante retratamento endodôntico. Quarenta incisivos inferiores foram divididos aleatoriamente em quatro grupos - GIM (n=10), GIIM (n=10), GIPT (n=10) e GIIPT (n=10) - nomeados de acordo com a realização (I) ou não (II) de patência apical durante o preparo de canais e a técnica de desobturação - manual (M) ou sistema ProTaper (PT). Após a desobturação, realizou-se a limpeza foraminal em cada espécime de todos os grupos com instrumentos #15, #20 e #25, gerando 12 subgrupos: GIM15, GIM20, GIM25, GIIM15, GIIM20, GIIM25, GIPT15, GIPT20, GIPT25, GIIPT15, GIIPT20 e GIIPT25. O material sólido extruído foi coletado pelo sistema de filtração Millipore®, com filtros de 0,45 µm de poro e 25 mm de diâmetro. Os filtros foram pesados antes e após a coleta, em balança analítica de precisão (10–5g), e as diferenças foram calculadas. Os valores médios encontrados (em mg) foram: GIM (0,95±0,94), GIIM (0,47±0,62), GIPT (0,30±0,31) e GIIPT (0,32±0,44), sem diferença estatística entre quaisquer dos grupos ou subgrupos (p>0,05). O sistema Protaper proporcionou a menor quantidade de material sólido extruído, independente da presença ou não de patência apical seguidos da técnica manual sem e com patência apical. Quantidades adicionais foram coletadas durante a limpeza foraminal, independente do instrumento utilizado, da presença ou não da patência apical ou da técnica de desobturação.

Cyclic Fatigue Resistance of Rotary NiTi Instruments after Simulated Clinical Use in Curved Root Canals

The aim of this study was to assess cyclic fatigue resistance in rotary nickel-titanium instruments after simulated clinical use in curved root canals (40-degree, 5-mm radius curve). Thirty-six RaCe rotary NiTi files, size #5, taper 0.04, were divided into 3 groups: Groups A, B and C with one, three and five cycles of use, respectively. Time to failure was recorded with a stopwatch in seconds and subsequently converted to number of cycles to fracture. The data were analyzed statistically by ANOVA and Tukey's test (α=0.05). Five sets of clinically used files (group C) reached significantly lower cycle-numbers before fracture (mean=197.5 cycles) when compared with one set of clinically used files (mean=309.2) and three sets (mean=287.5). Results showed that the number of simulated clinical uses of RaCe instruments for shaping curved canals affects adversely the fatigue resistance of these instruments after five uses.

Resumo O objetivo deste estudo foi avaliar a resistência à fadiga cíclica de instrumentos rotatórios de níquel-titânio após simulação de uso clinico em canais curvos (curvatura de 40° e raio de 5 mm). Trinta e seis instrumentos, calibre n° 25 conicidade 0,04, foram divididos em três grupos: o Grupo A com um ciclo de uso; Grupo B, três ciclos de uso e grupo C, cinco ciclos de uso. Um cronômetro digital aferiu em segundos o tempo até a fratura do instrumento que, posteriormente, foi convertido em número de ciclos para fratura. Os dados foram analisados por ANOVA e teste de Tukey (p<0,05). O grupo que utilizou o instrumento por cinco ciclos (grupo C) atingiu significativamente menores números de ciclos antes da fratura (média = 197,5 ciclos) quando comparado com os instrumentos utilizados em um ciclo (média = 309,2) e três ciclos (média = 287,5). Os resultados mostraram que o número de uso de instrumentos RaCe para modelar canais curvos afeta negativamente a resistência à fadiga cíclica dos instrumentos após cinco usos. .

Evaluation of the inflammatory response of the subcutaneous conjunctive of mice against some endodontic irrigations solutions

Introduction: Sodium hypochlorite has been used as an endodontic irrigant since 1936, when Walker used it as Sodium Chlorine. Since then it has became the most well acceptable endodontic irrigant. During the last few years many studies have reported the importance of pH control. Objective: This study evaluates the inflammatory response of some endodontic irrigations solutions in the subcutaneous connective tissue of mice. Material and methods: Thirty-six mice were obtained from the Biomedical Sciences Institute at the University of São Paulo. Their backs were divided into four quadrants and each quadrant was injured with an 8 mm punch. Three of these wounds were submitted to differents solutions, while the fourth was used as a control. This experiment was done in triplicate. After the irrigation of the wounds, the mice were sacrificed at 3, 7 and 14 days. The samples were fixed on 10% formalin and histologically analyzed after hematoxylin and eosin staining. Results: At 14 days all wounds were covered with epithelium with a mild inflammatory infiltrate in the subjacent connective tissue, except for the group that employed 5% sodium hypochlorite at pH 11. Conclusion: The greatest the pH and concentration of sodium hypochlorite solutions, the most toxic they are.

Assessing apical transportation in curved canals: comparison between cross-sections and micro-computed tomography

The aim of this study was to compare two methods of assessing apical transportation in curved canals after rotary instrumentation, namely, cross-sections and micro-computed tomography (µCT). Thirty mandibular molars were divided into two groups and prepared according to the requirements of each method. In G1 (cross-sections), teeth were embedded in resin blocks and sectioned at 2.0, 3.5, and 5.0 mm from the anatomic apex. Pre- and postoperative sections were photographed and analyzed. In G2 (µCT), teeth were embedded in a rubber-base impression material and scanned before and after instrumentation. Mesiobuccal canals were instrumented with the Twisted File (TF) system (SybronEndo, Orange, USA), and mesiolingual canals, with the EndoSequence (ES) system (Brasseler, Savannah, USA). Images were reconstructed, and sections corresponding to distances 2.0, 3.5, and 5.0 mm from the anatomic apex were selected for comparison. Data were analyzed using Mann-Whitney's test at a 5% significance level. The TF and ES instruments produced little deviation from the root canal center, with no statistical difference between them (P > 0.05). The canal transportation results were significantly lower (0.056 mm) in G2 than in G1 (0.089 mm) (p = 0.0012). The µCT method was superior to the cross-section method, especially in view of its ability to preserve specimens and provide results that are more closely related to clinical situations.