Aim
To evaluate possible modifications in root canal sealers subjected to a variety of heating conditions using vibrational spectroscopy and analysis of physical and chemical properties.
Methodology
EndoSequence BC Sealer HiFlow, Bio‐C Sealer, BioRoot RCS and AH Plus were analysed chemically using Raman spectroscopy (25–220 °C) and Fourier‐transform infrared spectroscopy (FT‐IR) (37–100 °C ). For FT‐IR, the materials were tested individually and mixed with root dentine powder. Scanning electron microscopy (SEM) and coupled energy dispersive spectroscopy (EDS) were used to evaluate surface and chemical elements. ISO 6876‐2012 and ASTM‐C266‐07 specifications were followed to evaluate flow, setting time (moist and dry), solubility and radiopacity. Also, pH analysis at 37 and 100 °C was performed. Shapiro–Wilk and Mixed ANOVA (within and between the effects of the subjects), Levene, and a post hoc analyses with Bonferroni correction were performed (P < 0.05).
Results
Vibrational spectroscopy revealed peaks of tricalcium silicate, dicalcium silicate and zirconium dioxide. Chemical changes in the Raman spectra during heating were discrete, as the inorganic content predominated the signalling for all root canal sealers. FT‐IR analysis exhibited spectral changes in water absorption for EndoSequence BC Sealer HiFlow and Bio‐C Sealer, probably related to dehydration. For BioRoot RCS and AH Plus, no significant chemical changes were observed. Bio‐C Sealer exhibited a band of polyethylene glycol only after heating to 100 °C, probably related to its thermal decomposition. SEM/EDS analysis corroborated the composition results observed in vibrational spectroscopy for all materials. Heating to 100 °C significantly changed the flowability of all calcium silicate‐based sealers with a wide variation in setting times at both temperatures, along with solubility levels above ISO standards. For all tested sealers, radiopacity fulfilled the requirements, and pH exhibited alkaline values.
Conclusions
The tested calcium silicate‐based sealers were affected by heating. Calcium silicate‐based root canal sealers had high solubility which is a concern for their clinical use. AH Plus was the only root canal sealer that was stable after heating.
Mid-infrared photothermal (MIP) microscopy is a valuable
tool for
sensitive and fast chemical imaging with high spatial resolution beyond
the mid-infrared diffraction limit. The highest sensitivity is usually
achieved with heterodyne MIP employing photodetector point-scans and
lock-in detection, while the fastest systems use camera-based widefield
MIP with pulsed probe light. One challenge is to simultaneously achieve
high sensitivity, spatial resolution, and speed in a large field of
view. Here, we present widefield mid-infrared photothermal heterodyne
(WIPH) imaging, where a digital frequency-domain lock-in (DFdLi) filter
is used for simultaneous multiharmonic demodulation of MIP signals
recorded by individual camera pixels at frame rates up to 200 kHz.
The DFdLi filter enables the use of continuous-wave probe light, which,
in turn, eliminates the need for synchronization schemes and allows
measuring MIP decay curves. The WIPH approach is characterized by
imaging potassium ferricyanide microparticles and applied to detect
lipid droplets (alkyne-palmitic acid) in 3T3-L1 fibroblast cells,
both in the cell-silent spectral region around 2100 cm–1 using an external-cavity quantum cascade laser. The system achieved
up to 4000 WIPH images per second at a signal-to-noise ratio of 5.52
and 1 μm spatial resolution in a 128 × 128 μm field
of view. The technique opens up for real-time chemical imaging of
fast processes in biology, medicine, and material science.
While
theophylline
has been extensively studied with multiple polymorphs
discovered, there is still currently no conclusive structure for the
metastable theophylline form III. In this present work, by combining
more widely used techniques such as X-ray diffraction and thermogravimetric
analysis with more emerging techniques like low-frequency Raman and
terahertz time-domain spectroscopy, to analyze the structure and dynamics
of a crystalline system, it was possible to provide further evidence
that the form III structure has a theophylline monohydrate structure
with the water molecules removed. Solid-state density functional theory
simulations were paramount in proving that this proposed structure
is correct and explain how vibrational modes within the crystal structures
feature and govern polymorphic transitions and the metastable form
III. Through the insight provided by both simulated and experimental
results, it was possible to decisively conclude the elusive crystal
structure of theophylline form III. It was also shown that the correct
space group for theophylline monohydrate is not P21/n but, in fact, Pc.
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