Influence of temperature on the torsional properties of two thermally treated NiTi rotary instruments

Abstract This study aimed to evaluate the influence of temperature on torsional strength and angular deflection of two experimental NiTi rotary instruments manufactured from Blue and Gold thermal treatments and with identical cross-sections. A total of 40 experimental NiTi instruments 25.06 and with a triangular cross-section and manufactured from Blue and Gold thermal treatments were used (n=20). The torsional test was performed in the 3 mm from the tip of the instrument according to ISO 3630-1. The torsional test evaluated the torsional strength and angular deflection to failure at room temperature (21°C ± 1° C) and body temperature (36°C ±1°C). The fractured surface of each fragment was observed by using scanning electron microscopy (SEM). Data were analyzed using an unpaired t test for inter and intra-group comparison and the level of significance was set at 5%. The results showed that the body temperature did not affect the torsional strength and angular deflection of the instruments when compared with room temperature (P>0.05). However, at body temperature, the Blue NiTi instruments presented significantly lower angular deflection in comparison with Gold NiTi instruments (P<0.05). There was no significant difference regarding the torsional strength of the instruments at body temperature (P>0.05). The temperature did not affect the torsional strength of the instruments manufactured from Blue and Gold technology. However, the Blue NiTi instruments presented significantly lower angular deflection than Gold instruments at 36°C temperature.

Resumo O objetivo deste estudo foi avaliar a influência da temperatura nas propriedades de torção (resistência à torção e deflexão angular) de dois instrumentos rotatórios experimentais de NiTi fabricados com secção triangu.ar e tratamentos térmicos Blue e Gold. Quarenta instrumentos experimentais de NiTi 25.06 com tratamento térmico Blue e Gold foram usados (n= 20). Foi avaliada a resistência torcional e a deflexão angular até a fratura na temperatura ambiente (21°C ± 1°C) e corporal (36°C ± 1°C). O teste torcional foi realizado nos 3 mm da ponta dos instrumentos de acordo com a ISO 3630-1. A superfície fraturada de cada instrumento foi observada pelo microscópio eletrônico de varredura (MEV). Os dados foram analisados por meio do teste t não pareado para a comparação inter e intragrupos e o nível de significância à 5%. Os resultados demonstraram que a temperatura corporal não afetou a resistência a torção e deflexão angular quando comparada com a temperatura ambiente (P>0.05). No entanto, na temperatura de 36°C o instrumento com tratamento térmico Blue apresentou menor deflexão angular quando comparado com o Gold (P<0.05). Não houve diferença significante entre os dois instrumentos em relação a resistência à torção. A temperatura corporal não modificou a resistência torcional dos instrumentos fabricados com tecnologia Blue e Gold. No entanto, os instrumentos com NiTi Blue apresentaram menor deflexão angular do que o Gold a 36°C.

Comparison of the Physicochemical Properties, Antimicrobial Action, and Cytotoxicity of Ambroxol Hydrochloride, N-acetylcysteine, and Calcium Hydroxide Pastes.

OBJECTIVE: To evaluate the solubility, pH, antimicrobial action, and cytotoxicity of ambroxol hydrochloride (AMB), N-acetylcysteine (NAC), and calcium hydroxide (CH) pastes for use as intracanal medications. METHODS: Solubility was determined by micro-CT, based on the paste volume remaining after immersion in water for 7 days. pH was measured by immersing acrylic tubes containing the pastes in ultrapure water and then measuring pH after 3 hours, 3 days, and 7 days. Antimicrobial action against Enterococcus faecalis was assessed based on the percentage of living cells, using the live/dead staining method under confocal microscopy. Cytotoxicity was assessed based on the cell viability of L929 fibroblast-like cells after 6, 24, and 48 hours. Cytotoxicity data were compared using the ANOVA and Tukey tests, and the antimicrobial data were compared using the Kruskal-Wallis and Dunn tests. The significance level used was 5% (α=0.05). RESULTS: The solubility values for all the study groups were significantly different (P<0.05), where the highest values were for NAC, followed by AMB, and then CH. Likewise, the pH levels were all significantly different (P<0.05), where NAC and AMB levels were acidic, and CH levels were alkaline. The antimicrobial action of AMB was significantly higher than that of CH (P<0.05), and that of NAC was also higher than that of CH, albeit not significantly. AMB and NAC were more cytotoxic than CH, and higher dilutions of CH promoted higher cell viability levels than lower dilutions of the same paste (P<0.05). CONCLUSION: The NAC and AMB pastes were more soluble and cytotoxic than the CH paste and had acidic pH levels. The AMB paste displayed the highest antimicrobial action against Enterococcus faecalis biofilm.

CYCLIC AND TORSIONAL FATIGUE RESISTANCE OF THREE DIFFERENT THERMALLY TREATED NICKEL-TITANIUM ROTARY INSTRUMENTS

Background: The aim of this study was to evaluate the cyclic fatigue and torsional fatigue resistance of three thermally treated rotary instruments, such as: Logic 2 25.05 (LOG 25.05), Edge Taper Platinum 25.06 (EDT 25.06) and ProTaper Gold 25.08 (PTG 25.08).Methods: A total of 60 rotary instruments of LOG 25.05, EDT 25.06 and PTG 25.08 were used (n=20). Cyclic fatigue tests were performed at 36°C using an artificial stainless steel canal with a 60ºangle and a 5-mm radius of curvature. The time (in seconds) and number of cycles to fracture (NCF) was recorded. The torsional test evaluated the torque and angle of rotation to failure at 3 mm from the tip according to ISO 3630-1. The fractured surface of each fragment was observed by using scanning electron microscopy (SEM). Data were analyzed using one-way ANOVA and Holm-Sidak's tests for multiple comparison, the level of significance was set at 5%.Results: EDT 25.06 had highest cyclic fatigue resistance (time and NFC), followed by LOG 25.05 and PTG 25.08 (P<0.05). There were no significantly difference between LOG 25.05 and ETP 25.06 regarding the NCF (P>0.05). In relation the torsional test, the LOG 25.05 and ETP 25.06 presented similar torque (P>0.05). The PTG presented greater torque than the other groups (P<0.05). The PTG 25.08 presented the lowest angular rotation to fracture than the other groups (P<0.05). The SEM images demonstrated typical features of cyclic and torsional fracture.Conclusion: In conclusion, the LOG 25.05 and ETP 25.06 presented similar cyclic and torsional properties. The PTG 25.08 showed greater torsional strength.

Evaluation of Torsional Resistance and Bending Stiffness of Coronal Flaring Nickel-Titanium Instruments.

OBJECTIVE: The aim of this study was to evaluate the bending and torsional resistance of the following instruments: Mtwo 25/.07 (MT - VDW, Munich, Germany), Navigator W-XN 25.07 (WXN - Wizard Navigator, Medin, Nové Mesto na Morave, Czech Republic), ProTaper Universal SX 19/.04 (PSX - Dentsply Tulsa Dental Specialties, Tulsa, USA), MK Orifice Shapper 17/.08 (OS - MK Life Medical and Dental Products, Porto Alegre, Brazil) and MK Sequence 17.12 (MKS - MK Life Medical and Dental Products, Porto Alegre, Brazil). METHODS: One hundred instruments were used (n=20). Resistance to bending (n=10), torque and angular deflection (n=10) at the failure of new instruments were measured according to ISO 3630-1. Metal mass volume at 3 mm from the tip was evaluated using micro-computed tomography (micro-CT). The fractured surface of each fragment was examined by scanning electron microscopy (SEM). Data were analysed using 1-way analysis of variance and Tukey tests. RESULTS: Torsional resistance values of MK Sequence were higher than the other groups (P<0.05). No differences were observed among MT, WXN and OS (P>0.05) and PTS, which presented the lowest values (P<0.05). MT showed the highest angular deflection (P<0.05). WXN and PSX presented no significant difference (P>0.05). PSX and OS also showed no significant differences (P>0.05). MKS instruments had the lowest angular deflection values (P<0.05). There were significant differences among all the groups in bending stiffness test (P<0.05), but PSX had the lowest torque to bend (P<0.05). MKS had the larger metal mass volume at 3 mm from the tip (P<0.05). SEM analysis showed similar and typical features of torsional failure for all instruments tested. CONCLUSION: In conclusion, MK Sequence 17/.12 had the highest torsional fracture resistance. Mtwo 25/.07 showed higher angular deflection capacity, and ProTaper Universal SX the 19/.04 lower bending stiffness.

Evaluation of the mechanical properties of different nickel-titanium retreatment instruments.

This study investigated the cyclic fatigue, bending, torsional resistance and angular deflection of Pro-R 25.08, Logic RT 25.08, MK Retreatment 25.08 (MK RT) and ProTaper Retreatment D2 instruments. Cyclic fatigue test was performed until fracture in a custom stainless-steel device with water bath equipment to simulate body temperature. Fracture time was recorded. A number of cycles were calculated. Resistance to bending at 45°, torsional resistance and angular deflection were evaluated. The fracture surfaces were examined by scanning electron microscopy. Statistical analysis was performed with one-way ANOVA and Tukey and Kruskal-Wallis and Dunn tests. Pro-R and Logic RT presented the highest cyclic fatigue (P < 0.05). D2 had higher strength to bend than Pro-R and Logic RT (P < 0.05). Logic RT showed the highest torque and angular deflection (P < 0.05), without differences when compared to D2 (P > 0.05). Instrument performances were dependent on their geometrical features and heat treatments.

Antibióticos potencializam a ação antimicrobiana de cimentos endodônticos, em diferentes períodos, após a presa / Antibiotics increase the antimicrobial action of endodontic seal-ers, in different periods, after setting time

O objetivo do presenteestudo foi avaliar a atividade antibacteriana dos cimentos endodôn-ticos MTA Fillapex, Sealapex, Sealer 26 e Endofill puros e acrescidos de amoxicilina e ci-profloxacina frente a duas linhagens ATCC de Enterococcus faecalis (ATCC 29212 e ATCC 4083). Os testes foram realizados pela técnica de difusão radial dos cimentos aplicados di-retamente no ágar e impregnados em discos de papel e pelo teste de contato direto. Para a análise estatística, utilizaram-se os testes de ANOVA e Tukey com nível de significância de 5%. Os resultados mostraram que pela técnica da difusão radial, considerando os cimentos puros, o Sealapex foi o único que apresentou halos de inibição frente às duas linhagens. Já quando da associação de amoxicilina e ciprofloxacina, o MTA Fillapex revelou os melhores halos de inibição para as duas linhagens. Todos os cimentos tiveram a ação potencializada pela adição dos antibióticos (p<0,05). Pela técnica de difusão dos cimentos impregnados em discos de papel, o cimento Sealapex puro fresco demonstrou atividade antimicrobiana em todas as variáveis de tempo. Quando acrescidos dos antibióticos, todos os cimentos ti-veram a ação antimicrobiana potencializada pelas drogas, em todas as variáveis de tempo. Esse mesmo resultado foi observado na técnica do contato direto dos cimentos com ambas as linhagens. A atividade antibacteriana, frente ao E. faecalis, dos cimentos MTA Fillapex, Endofill, Sealer e Sealapex, acrescidos dos antibióticos amoxicilina e ciprofloxacina, foi potencializada mesmo após um longo período da presa dos cimentos.

The objective of this study was to evaluate the antibacterial activity of different endodon-tic cements (MTA Fillapex, Sealapex, Sealer 26, and Endofill), both pure and mixed with 5% of amoxicillin or ciprofloxacin, against two strains of Enterococcus faecalis (ATCC 29212 and ATCC 4083). Bacterial susceptibility testing was conducted by radial diffusion methods and direct contact test after different periods. Data were subjected to ANO-VA and Tukey test with a significance level of 5%. Sealapex was the only pure sealer to promote the inhibition of bacterial growth against both strains in different experimental periods. However, all cements present an increase in antibacterial activity by the addition of antibiotics (p<0.05). MTA Fillapex and Sealapex associated with amoxicillin promoted increased values for bacterial growth against ATCC 29212 and ATCC 4083 in comparison to other groups (p<0.001), including extended periods after setting time. The association of antibiotic agents increased the antibacterial effect of the evaluated sealers against the strains of E. faecalis.