Effectiveness of three auxiliary irrigation methods for cleaning the internal walls of root canals of curved isolated teeth.

OBJECTIVES: This study aimed to compare the effectiveness of ultrasound and acoustic and laser cleaning of curved root canals. METHODS: A total of 92 molars with independent root canals with a curvature of 20°-40° were prepared and standardized at 04 25# and stained with gentian violet solution for 72 h. Among them, 52 were randomly divi-ded into four groups for final rinsing (n=13): NI group, PUI group, EDDY group, and PIPS group. Ten samples in each group were cut horizontally along the long axis perpendicular to the root and divided into curved upper, curved, and apical segments. Images were taken with a stereomicroscope and Image J measurements were taken to calculate the depth of rinse penetration. The remaining three samples from each group were split along the long axis of the dentin, photographed by scanning electron microscope to record the dentin tubule exposure and staining layer, and scored for staining layer by double-blind method. SPSS 26.0 software was used to perform statistical analysis and select the best flushing method. An extra 40 samples were randomly divided into four groups for detection of flushing fluid penetration depth (n=10): 10, 20, 30, and 40 s. RESULTS: In the upper part, the mean depth of infiltration was not significantly different between the experimental and control groups (P>0.05). The PIPS group had a significantly lower smear layer score than the control group and the EDDY group (P<0.01). In the curved segment, the mean depth of infiltration was significantly greater in the PUI group than in the control group (P<0.05); the tarnish layer score was lower in each experimental group than in the control group. At the top, the mean depth of infiltration was greater in the PUI and PIPS groups than in the control group (P<0.05), and the smear layer score was lower in the PIPS group than in the other groups (P<0.05). After the time was changed, the depth of infiltration of PUI increased only in the apical segment as the flushing time increased. CONCLUSIONS: The PUI and PIPS methods facilitate the penetration of irrigation solution into the dentin canal in curved root canals, especially in the apical segment. The PIPS technique is effective in removing the smear layer in curved root canals.

Hydrazone-oxime Selectively Directed Redox-Neutral [4 + 2] Annulations Cascade with Alkynes and Iodonium Ylides to Build 1,1'-Biisoquinoline Mono-N-oxides.

Selective C-H activation of a molecule containing multiple directing groups is an important but challenging issue in organic chemistry. Herein, a combined directing group (hydrazone-oxime) selectively directed [4 + 2] annulation cascade to synthesize novel 1,1'-biisoquinoline mono-N-oxides has been developed. Owing to the subtle differences in electronic properties between hydrazone and oxime, the first C-H annulation with alkynes preferentially occurs at the hydrazone side to form 1-oximido isoquinolines, which then undergoes a second C-H annulation with iodonium ylides at the oxime side. The two [4 + 2] annulations work smoothly under redox-neutral conditions and can be performed in one pot, without utilization of stoichiometric external oxidants. Moreover, ESI-MS and DFT calculations have been conducted to corroborate the reaction mechanism. Such novel biisoquinoline skeletons can pave the way for future research prospects with synthetic value.

Rh(III)-Catalyzed One-Pot Three-Component Diannulation of Benzils, Ammonium Acetate, and Alkynes to Build 1,1'-Biisoquinolines.

An efficient one-pot synthesis of 1,1'-biisoquinolines by a three-component reaction of commercially available raw materials (benzils, NH4OAc, and alkynes) is disclosed. This complicated reaction involves in situ diimine formation via benzil-NH4OAc condensation, Rh(III)-catalyzed 2-fold imine-directed C-H activation, and annulation with alkynes. Both symmetric and unsymmetric 1,1'-biisoquinolines could be assembled in moderate to high yields. The reaction mechanism is supported through ESI-MS, in which Cp*ClRh+, Cp*(OAc)Rh+, Cp*(OPiv)Rh+, and two rhodacycle intermediates are successfully detected to explain the evolution of rhodium species.

Decarbonylative/decarboxylative [4 + 2] annulation of phthalic anhydrides and cyclic iodoniums towards triphenylenes.

A palladium-catalyzed decarbonylative/decarboxylative [4 + 2] annulation of phthalic anhydrides with cyclic diaryliodonium salts to synthesize triphenylenes has been developed. The reaction shows broad substrate scope with a high yield of up to 99%, and it provides an efficient and fast way to access functionalized triphenylenes in only one hour.