Assessment of the Ability of Different Cleaning Protocols to Remove Eugenol-based Endodontic Sealer from the Root Dentin.

AIM: The aim of this study is to assess three protocols for removing a eugenol-based filling endodontic sealer from root dentin and the bond strength of fiberglass posts luted with resin cement. MATERIALS AND METHODS: Sixty single-rooted bovine teeth were prepared and filled with the Endofill endodontic sealer and gutta-percha cones. After 7 days, 9 mm of the filling was removed and divided into five groups (n = 12) according to the cleaning protocol: G1 (negative control), unfilled; G2 (positive control), saline solution; G3, 95% alcohol; G4, amyl acetate; and G5, Largo bur. The canals were hybridized and fiberglass posts were luted with resin cement. They were cross-sectioned in slices of 1 mm and subjected to the push-out test. The other samples were sectioned longitudinally and visualized in a scanning electron microscope (SEM), and the existing chemical elements were quantified by energy dispersive spectroscopy (EDS). The statistical analysis used variance analysis (ANOVA)-one way and Fisher's test, at a 5% significance level. RESULTS: The 95% alcohol was more effective for cleaning the canal, resulting in a clean dentinal surface and bond strength statistically similar to the negative control. The Largo bur was also statistically similar to the negative control, with only a few debris impregnated on the wall. Amyl acetate showed more sealer residues on the canal walls, with a consequent lower bond strength value than the other groups, only higher than the positive control. CONCLUSION: The 95% alcohol and Largo burs may be used after removing the canal filling, so that the bond strength is improved when using the eugenol-based sealer.

Effect of different protocols of eugenol removal on the bond strength between the fibre post and root dentin.

The aim of this study was to evaluate the bond strength between the fibre post and root dentin after different cleaning protocols to remove eugenol from dentin. The residues and elemental composition of dentin were analysed using SEM and EDS. Bovine incisor roots were obturated with eugenol-based sealer. The post space was prepared, and the roots were divided into the following groups according to the cleaning protocol: unfilled (negative control), saline solution (positive control), 70% ethanol, acetone and 70% isopropyl alcohol. The fibre posts were cemented and push-out test realised. Chemical analysis of the dentin was performed using SEM and EDS. The bond strength values were analysed by anova/Fisher's and were as follows: negative control (7.30 ± 2.77) = 70% ethanol (6.64 ± 2.91) = 70% isopropyl alcohol (5.01 ± 3.15) = acetone (4.42 ± 1.53) >positive control (1.29 ± 0.56). It was concluded that 70% ethanol may be a good cleaning protocol to remove eugenol from dentin.

Oral Lesions found in a Dental School in Southern Brazil.

OBJECTIVE: This study aimed to perform an epidemiological survey of the cases of oral lesions diagnosed in a Brazilian dental school. MATERIALS AND METHODS: An epidemiological survey was carried out at the Faculty of Dentistry of the University of Passo Fundo (FOUPF), Rio Grande do Sul, Brazil, between March 2015 and June 2017, characterizing the patients in terms of gender, age, and ethnicity. A total of 3,200 records were evaluated, from which 716 presented information on oral lesions diagnosed and treated at the clinics of the FOUPF. The data were evaluated by descriptive statistics of frequency. RESULTS: The most frequent change was the coated tongue (13.83%). The majority of the patients were female (56%), white (31.57%), in the sixth decade of life (21.65%). Regarding the classification of lesions, the most frequent group was developmental changes (25%). CONCLUSION: It is considered that the sample studied presented a significant index of oral lesions and normality changes, considering that 716 (22.38%) patients studied showed some type of change in the oral cavity. CLINICAL SIGNIFICANCE: The sample studied presents peculiar characteristics regarding the number of oral lesions/conditions diagnosed. It is also considered that Schools of Dentistry are valuable environments for carrying out epidemiological surveys in stomatology, providing the diagnostic exercise, as long as the students are stimulated for this purpose.

Influence of remaining coronal structure and of the marginal design on the fracture strength of roots restored with cast post and core.

OBJECTIVE: The purpose of this study was to evaluate the fracture strength of roots that were prosthetically restored with cast post and core with or without any remaining coronal structure and with different finish lines. MATERIALS AND METHODS: Sixty bovine incisors were sectioned below the cementoenamel junction, endodontically treated and randomly divided into six experimental groups (n = 10) containing teeth with or without any remaining coronal structure and with a beveled shoulder, a chanfered or a shoulder finish line design. The cast post and core were luted with dual-cured resin cement. The metal crowns were cemented with zinc phosphate cement. The specimens were subjected to a tangential compressive load (135° angle) at a crosshead speed of 0.5 mm/min until failure, using a universal testing machine. The fracture strength data were analyzed using the ANOVA and LSMeans (least square means) tests (α = 0.05). RESULTS: The data indicated that the teeth with 2 mm of remaining coronal structure showed the highest fracture strength values when compared with the teeth without any remaining structure (p < 0.05). As to the different finish line designs, the highest fracture strength values were obtained for the beveled shoulder, followed by the chanfered and then by the shoulder designs (p < 0.05). CONCLUSIONS: It may be concluded that, to increase fracture strength, a beveled shoulder and 2 mm of remaining coronal structure are the ideal conditions.

Fatigue strength: effect of welding type and joint design executed in Ti-6Al-4V structures.

BACKGROUND: This study evaluated the fatigue strength of Ti-6Al-4V-machined structures submitted to laser (L)-welding and TIG (TIG)-welding procedures, varying the joint designs. MATERIALS AND METHODS: Seventy dumbbell rods were machined in Ti-6Al-4V alloy with central diameters of 3.5 mm. The specimens were sectioned and welded using TIG or L and three joint designs {'I' design, varying welding distances [0.0 mm (I00) or 0.6 mm (I06)], or 'X' [X] design}. The combinations of variables created six groups, which, when added to the intact group, made a total of seven groups (n = 10). L was executed as follows: 360 V/8 ms (X) and 390 V/9 ms (I00 and I06), with focus and frequency regulated to zero. TIG was executed using 2:2 (X) and 3:2 (I00 and I06) as welding parameters. Joints were finished, polished and submitted to radiographic examination to be analysed visually for the presence of porosity. The specimens were then subjected to mechanical cyclic tests, and the number of cycles completed until failure was recorded. The fracture surface was examined using a scanning electron microscope. RESULTS: The Kruskal-Wallis and Dunn test (α = 0.05) indicated that the number of cycles resisted for fracture was higher to X for both welding procedures. To L, I06 was as resistant as X. The Mann-Whitney U-test (α = 0.05) indicated that L joints were more resistant than TIG to I00 and I06. Spearman's correlation coefficient (α = 0.05) indicated a negative correlation between the number of cycles and presence of porosity. CONCLUSION: Thus, to weld Ti-6Al-4V structures, the best condition is X, independent of the welding method employed.

Influence of endodontic irrigants on bond strength of a self-etching adhesive.

The aim of this in vitro study was to evaluate the bond strength of a self-etching adhesive system to dentine irrigated with sodium hypochlorite (NaOCl), chlorhexidine solution (CX) and ethylene diamine tetra acetic acid (EDTA) by microtensile testing. Sixty human third molars were sectioned 3 mm below the occlusal level and then randomly divided into six groups: G1(control), without irrigant solution; G2, 1% NaOCl; G3, 1% NaOCl followed by the application of 17% EDTA; G4, 2% CX; G5, 2% CX followed by the application of 17% EDTA and G6, 17% EDTA. The specimens received the self-etching adhesive system were restored with composite resin, then sectioned and trimmed to obtain four hourglass-shaped slabs from each tooth. The specimens were submitted to the microtensile test in a Universal Testing Machine at a crosshead speed of 0.5 mm min(-1) until fracture. The results were submitted to statistical analysis by anova /Newman-Keuls. The means and standard deviations (MPa) were: G1, 26.88 (±3.81); G2, 19.08 (±3.89); G3, 18.16 (±2.21); G4, 18.14 (±4.32); G5, 34.30 (±3.32); G6, 13.61 (±1.21). It was concluded that the application of 2% CX followed by the application of 17% EDTA resulted in increasing the bond strength of the self-etching adhesive system to dentine, when compared with the results obtained for the other tested groups.