Effect of Cryotherapy on Fracture Resistance of Neoniti Rotary Instruments.

Objectives: Nickel-titanium (NiTi) rotary files were introduced to optimize root canal instrumentation in endodontic treatment. However, despite the numerous advantages of NiTi instruments, they may unexpectedly break during clinical use, resulting in obstruction of the root canal system. This investigation aimed to assess the effect of cryotherapy on fracture resistance of Neoniti rotary files. Materials and Methods: This in vitro, study was conducted on 20 Neoniti rotary files with #35 tip size and 6% taper in two groups with and without cryogenic treatment (N=10). For cryogenic treatment, the files were immersed in liquid nitrogen at -196°C for 24 hours. Next, the Neoniti files in both groups were subjected to cyclic fatigue testing in a hand-piece operating at 500 rpm with 20 N/cm torque. The files were rotated until fracture and the fracture time as well as the number of cycles to fracture were recorded for each file. The two groups were compared by independent t-test at 0.05 level of significance. Results: The number of cycles to fracture was 235700±50649.22 in the control and 280600±22979.21 in the cryotherapy group. The mean fracture time was 471.40±101.29 and 561.20±45.958 seconds in the control and cryotherapy groups, respectively. Significant differences in both variables were noted between the two groups (P<0.05). Conclusion: Based on our findings, utilizing cryogenic treatment may enhance the fracture resistance of rotary instruments, making it a beneficial practice for dental clinicians to adopt. By using cryogenically treated rotary instruments, clinicians can potentially reduce the risk of file fracture during dental procedures.

Evaluation of the apical microleakage of MTA Fillapex, AH26, and Endofill sealers / Avaliação da microinfiltração apical de cimentos MTA Fillapex, AH26 e Endofill

Objective: Proper apical seal plays an important role in the success of root canal treatment. The most common cause of failure of root canal therapy is known as the lack of adequate apical seal. The aim of this in vitro study was to compare the apical microleakage of MTA Fillapex, AH26, and Endofill sealers using dye penetration method. Material and Methods: In this in vitro study, 72 single-rooted extracted human teeth were selected. The teeth were randomly divided into three experimental groups of 20 and two positive and negative control groups of 6. The canals were prepared by step-back technique and then filled with gutta-percha and one of the sealers mentioned. In the positive control group, the canals were filled with gutta-percha without sealer, and in the negative control group, the canals were prepared but not filled. The teeth were immersed in 2% methylene blue dye for 72 hours. The teeth were then cut longitudinally and the level of dye penetration was measured under a stereomicroscope. Data were analyzed by SPSS ver. 19 software, ANOVA and Bonferroni post-hoc tests. Results: The mean level of dye penetration in the Endofill test group was significantly higher than that in the AH26 and MTA Fillapex test groups. While, the observed difference between AH26 and MTA Fillapex groups was not statistically significant (p<0.05). Conclusion: The results of this study showed that AH26 and MTA Fillapex sealers did not show any significant difference in apical seal properties. However, their sealing strength was significantly greater than Endofill sealer. (AU)

Objetivo: O selamento apical adequado desempenha um papel importante no sucesso do tratamento do canal radicular. A causa mais comum de falha da terapia endodôntica é conhecida como falta de selamento apical adequado. O objetivo deste estudo in vitro foi comparar a microinfiltração apical dos cimentos MTA Fillapex, AH26 e Endofill usando o método de penetração de corantes. Materiais e métodos: Neste estudo in vitro, 72 dentes humanos unirradiculares extraídos foram selecionados. Os dentes foram divididos aleatoriamente em três grupos experimentais de 20 e dois grupos controle, positivo e negative, de 6. Os canais foram preparados pela técnica escalonada e preenchidos com guta-percha e um dos cimentos mencionados. No grupo controle positivo, os canais foram preenchidos com guta-percha sem cimento, e no grupo controle negativo, os canais foram preparados, mas não preenchidos. Os dentes foram imersos em corante azul de metileno a 2% por 72 horas. Os dentes foram então cortados longitudinalmente e o nível de penetração do corante foi medido sob um estereomicroscópio. Os dados foram analisados pelo software SPSS ver. 19 e pelos testes ANOVA e post-hoc de Bonferroni. Resultados: O nível médio de penetração do corante no grupo de teste Endofill foi significativamente maior do que nos grupos de teste AH26 e MTA Fillapex. Enquanto, a diferença observada entre os grupos AH26 e MTA Fillapex não foi estatisticamente significante (p <0,05). Conclusão: Os resultados deste estudo mostraram que os cimentos AH26 e MTA Fillapex não apresentaram diferença significativa nas propriedades do selamento apical. No entanto, suas forças de vedação foram significativamente maiores que a do cimento Endofill. (AU)

Effect of retreatment on the push-out bond strength of MTA-based and epoxy resin-based endodontic sealers.

Background. Further studies on the adhesion properties of MTA-based materials seem necessary due to their growing use in endodontic treatment. This research aimed to assess the effect of retreatment on the bond strength of MTA-based (MTA Fillapex) and epoxy resin-based (AH Plus) sealers. Methods. ProTaper rotary files were applied to prepare the root canals of 80 human mandibular premolars. Then, the roots were randomly divided intotwo groups of A (n=40) and B (n=40), which were obturated with gutta-percha and MTA Filla-pex and AH Plus sealer, respectively. In both groups, the teeth were randomly subdivided into 2 subgroups. No retreatment was carried out in subgroups A1 and B1, while subgroups A2 and B2 were retreated with rotary files and a solvent. Then, a push-out test was performed on four 2-mm slices of each tooth at a distance of 2 mm from the coronal surface after two weeks of incubation. Data were analyzed with two-way ANOVA and statistical significance was set at P<0.05. Results. Regardless of the procedure followed (P<0.001), significant differences were detected in the mean bond strength values between the two sealers. Irrespective of the sealer type (P=0.3), no significant differences were revealed by comparing the mean bond strength values of the study subgroups. Furthermore, no statistically significant interaction (P=0.5) was found between the treatment and sealer types. Conclusion. AH Plus sealer exhibited a higher bond strength compared to MTA Fillapex. Retreatment using rotary files and chloroform had no statistically significant effect on the bond strength of sealers evaluated in this study.

Comparison of Apical Extrusion of Debris by Using Single-File, Full-Sequence Rotary and Reciprocating Systems.

OBJECTIVES: During root canal preparation, apical extrusion of debris can cause inflammation, flare-ups, and delayed healing. Therefore, instrumentation techniques that cause the least extrusion of debris are desirable. This study aimed to compare apical extrusion of debris by five single-file, full-sequence rotary and reciprocating systems. MATERIALS AND METHODS: One hundred twenty human mandibular premolars with similar root lengths, apical diameters, and canal curvatures were selected and randomly assigned to six groups (n=20): Reciproc R25 (25, 0.08), WaveOne Primary (25, 0.08), OneShape (25, 0.06), F360 (25, 0.04), Neoniti A1 (25, 0.08), and ProTaper Universal. Instrumentation of the root canals was performed in accordance with the manufacturers' instructions. Each tooth's debris was collected in a pre-weighed vial. After drying the debris in an incubator, the mass was measured three times consecutively; the mean was then calculated. The preparation time by each system was also measured. For data analysis, one-way ANOVA and Games-Howell post hoc test were used. RESULTS: The mean masses (±standard deviation) of the apical debris were as follows: 2.071±1.38mg (ProTaper Universal), 1.702±1.306mg (Neoniti A1), 1.295±0.839mg (OneShape), 1.109±0.676mg (WaveOne), 0.976±0.478mg (Reciproc) and 0.797±0.531mg (F360). Compared to ProTaper Universal, F360 generated significantly less debris (P=0.02). The ProTaper system required the longest preparation time (mean=88.6 seconds); the Reciproc (P=0.008), OneShape (P=0.006), and F360 (P=0.001) required significantly less time (P<0.05). CONCLUSIONS: All instruments caused extrusion of debris through the apex. The F360 produced significantly less debris than did the ProTaper Universal.

Comparison of Push-out Bond Strength of Gutta-percha to Root Canal Dentin in Single-cone and Cold Lateral Compaction Techniques with AH Plus Sealer in Mandibular Premolars.

Background and aims. The single-cone technique has gained some popularity in some European countries. The aim of the present study was to compare the push-out bond strength of gutta-percha to root canal dentin with the single-cone and cold lateral compaction canal obturation techniques. Materials and methods . The root canals of 58 human mandibular premolars were prepared using modified crown-down technique with ProTaper rotary files up to #F3as a master apical file (MAF) and divided randomly into groups A and B based on canal obturation technique. In group A (n = 29) the root canals were obturated with single-cone technique with #F3(30/.09) ProTaper gutta-percha, which was matched with MAF in relation to diameter, taper and manufacturer; in group B (n = 29) the canals were obturated with gutta-percha using cold lateral compaction technique. In both groups AH plus sealer were used. After two weeks of incubation, three 2-mm slices were prepared at a distance of 2 mm from the coronal surface and push-out test was carried out. Data were analyzed with descriptive statistics using independent samples t-test. Results. There were statistically significant differences between two groups. The mean push-out bond strength was higher in group B (lateral compaction technique) compared to group A (single-cone technique; P < 0.05). Conclusion . Use of single-cone technique for obturation of root canals resulted in a lower bond strength compared to cold lateral compaction technique.