Aim: To study the effects of microelectric current and other methods at different temperatures, on the dissolution of sodium hypochlorite (NaOCl). Materials and methods: Bovine muscle tissues (n = 165) were prepared and grouped into three temperature groups: (1) Room temperature, (2) 45°C, and (3) 600°C. Each temperature group was divided into five subgroups: (i) Control group: 5.25% NaOCl; (ii) 5.25% NaOCl with pipetting; (iii) 5.25% NaOCl with sonic activation; (iv) 5.25% NaOCl with ultrasonic activation; and (v) E-NaOCl = 5.25% NaOCl with microelectric current. Weight of specimens before and after treatment was done. In each group average, standard deviation and median were found out. The data were analyzed using multiway analysis of variance (ANOVA) test and Tukey honestly significant difference (HSD) tests. The alpha-type error was set at <0.05. Results: Tissue dissolution was highest with the ultrasonic group (p < 0.05), and the tissue dissolution ability of other groups was significantly higher than the positive control (p < 0.05) at room temperature. E-NaOCl group dissolved greater quantity of tissue (p < 0.05) at 45°C and at 60°C. Conclusion: NaOCl used along with microelectric current produced a higher tissue-dissolving ability. Combining with other techniques provides a synergistic effect on tissue dissolution.

Aim: To compare the shear bond strength (SBS) to dentin, of three different glass ionomer cements (GIC): Ketac Universal (with and without conditioner), Fuji IX, and Ketac Molar. Materials and methods: Forty-eight extracted human maxillary premolars were selected. Depth holes measuring 1.5 mm were drilled in the deepest part of central fossa of each tooth sample. Occlusal surfaces were ground on a trimmer to expose flat dentinal surface and polished. The specimens were then embedded in autopolymerizing acrylic resin. Groups I, III, and IV specimens were restored with Ketac Universal, Fuji IX, and Ketac Molar respectively after conditioning. Group II specimens were restored with Ketac Universal without conditioning. A cellophane tube of diameter 4 mm was used to prepare GIC restorations. The samples were kept in water bath at 37°C for 24 hours. Each GIC specimen was loaded in a universal testing machine (INSTRON) with a crosshead speed of 0.5 mm/min. The bond strength (MPa) was calculated by dividing the shear force in Newton (N) by area of adhesion (m²). Statistical analysis: The results were statistically analyzed by Welch test and analysis of variance (ANOVA) test with pairwise “t” test. Results: The mean value of SBS was found to be highest for Ketac Molar, followed by Ketac Universal with conditioner, and Fuji IX GIC, and was lowest for Ketac Universal without conditioner. Conclusion: Ketac Universal, when used without conditioner, showed significant values of SBS, but is less than other conventional GICs.

Introduction: The aim of this study is to evaluate the effects of herbal alternative (green tea polyphenols) and ethylenediaminetetraacetic acid (EDTA) + NaOCl on the microhardness of root canal dentin after instrumentation with ProTaper Next (PTN; Dentsply) and Twisted Files (TF; SybronEndo). Materials and methods: Twenty single-rooted human premolar teeth will be instrumented up to the working length with PTN and TF (10 each) and then will be longitudinally sectioned into 40 segments and then embedded in an autopolymerizing acrylic resin. The microhardness of the dentin in the specimen will be measured with a Vickers diamond indenter at the apical third of the roots. Then the specimens will be divided randomly into two groups: 17% EDTA + 2.5% NaOCl and green tea polyphenols. Posttreatment microhardness values will be obtained and the decrease in microhardness will be calculated as a percentage. Microhardness values will be statistically analyzed using the Kruskal–Wallis and Mann–Whitney U tests. Results: Statistical analysis using one-way analysis of variance (ANOVA) showed that both the file groups with NaOCl + EDTA showed significant reduction in root dentin microhardness (p > 0.05). Conclusion: Even though green tea polyphenols showed lesser reduction in microhardness, its ability to remove smear layer completely and the antibacterial efficacy and practicality of using green tea as a root canal irrigant require further investigations. Its potency to discolor tooth and ability to eliminate biofilm is a matter of debate.

Aim: To evaluate the effects of bonding agents, composite resins, and reattachment techniques on impact strength of permanent maxillary central incisors in which fragment reattachment was done. Materials and methods: Ninety permanent maxillary central incisors were collected and standardized fragments were obtained from 80 incisors by sectioning them 3 mm away from the incisal edge. The teeth specimens were distributed into eight test groups and one control group (n = 10) according to the reattachment technique (direct bonding or circumferential chamfer); adhesive system (single bond or Clearfil SE Bond); and intermediate material (Filtek flow or RelyX U200). The impact strength of reattached tooth was evaluated using universal testing machine Instron. The results were analyzed using one-way analysis of variance (ANOVA) and Tukey's multiple post hoc analysis. Results: The fragment reattachment using circumferential chamfer was significantly superior to direct bonding. The use of single bond significantly increased the impact strength when compared with the use of Clearfil SE. Conclusion: No technique or material, when individually considered, was capable of achieving the impact strength of the sound teeth; however, the association of reattachment technique circumferential chamfer with adhesive system (single bond) could approximate the impact strength of sound teeth. Clinical significance: By achieving knowledge about the right materials and techniques for reattachment, this treatment modality could be used as a viable and feasible option for the uncomplicated fractured anterior teeth.

Aim: To evaluate the effects of different surface treatments on the repair bond strength of three different nanohybrid composites, namely conventional nanohybrid, bulk fill, and ceramicincorporated composites. Materials and methods: A split mold of height 5 × 5 mm in diameter was taken; 60 composite blocks were prepared based on three composites used. Group I: Kerr nanohybrid, group II: Tetric N-Ceram Bulk Fill, and group III: NanoCeram. Composite material was restored with incremental layering technique of 2 mm thickness. Aging of the composite blocks was achieved by storing them in distilled water for 1 week and then thermocycling. The samples were surface treated as subgroup A: sandblasting with silica particles, subgroup B: coarse grit diamond bur, subgroup C: etching with 10% hydrofluoric acid, and subgroup D: control group. Surface roughness of each surface-treated sample was evaluated using three-dimensional (3D) profilometer. A silane coupling agent and an adhesive agent were applied. Composite blocks were restored with the respective composite resins using a repair mold. A shearing force test was performed using universal testing machine. A load was applied to the interface at a crosshead speed of 0.5 mm/minute until fracture. Analyses were performed using analysis of variance (ANOVA) and post hoc Tukey test. Results: Highest shear bond strength was observed in composites surface treated with sandblasting followed by bur and hydrofluoric acid. The lowest shear bond strength was observed in the control group. Conclusion: Sandblasting surface treatment of Kerr composite manifested the highest bond strength, followed by Tetric N-Ceram and NanoCeram groups. Bur treatment of Tetric N-Ceram showed the higher bond strength values compared with the other groups. HF3 surface treatment of NanoCeram composite presented inferior bond strength values. Repair bond strength of aged nanohybrid resins could be improved with sandblasting, silane, and adhesive resin application compared with other surface treatments.

Aim: The aim of this study was to evaluate the effect of thermocycling on microhardness of three composites cured at different durations. Materials and methods: One hundred and twenty disks (N = 120) were made with a dimension of 5 mm diameter and 2 mm height using a metal mold from three composites (Filtek Z350 XT, Tetric N Ceram, Z100 Universal Restorative). Forty disks each were made with each composite, which were again divided into two subgroups according to the duration of curing, 20 and 40 seconds. Microhardness test was done before and after thermocycling using Vickers microhardness test. Thermocycling was done at –5 and at 55°C for 250 cycles. Values were analyzed using analysis of variance (ANOVA) test, Tukey's simultaneous comparison. Results: Among the groups cured for 40 seconds, in the control group, Z100 restorative showed higher microhardness. After thermocycling, even though there was a significant reduction in microhardness in all three composites, Tetric N Ceram showed minimal change in values compared with the other two composites. Conclusion: It was concluded that after thermocycling, the composite resins are susceptible to significant reduction in microhardness. Clinical significance: Patient's oral conditions, such as the cyclic thermal gradient and humidity can have negative effects on the mechanical properties of restorative materials. This is one of the factors contributing to a future need for replacement of dental restorative materials.