Feasibility and Safety of Adopting a New Approach in Delivering a 450 nm Blue Laser with a Flattop Beam Profile in Vital Tooth Whitening. A Clinical Case Series with an 8-Month Follow-Up

A prospective observational case series included six patients who presented with discoloured upper and lower teeth extending from the right second premolar to the left second premolar. The photoactivation dosimetry and treatment protocol were as follows: λ 450 nm, 1 W, CW; flattop beam profile; 1 cm2; 15 J/spot; 10 irradiated spots; an irradiation time of 15 s/spot; three whitening cycles in a single session. Blanc One ULTRA+ was the bleaching agent. A visual analogue scale (VAS) was utilised to evaluate the pain intensity and dental hypersensitivity during treatment immediately after complete treatment (T1), 24 h (T2), and 8 h (T3) postoperatively, and at an 8-month follow-up timepoint (T4), whereas the dental colour shade change was assessed using the VITA colour shade guide pre-treatment (T0), T1, and T4. The Gingival index and modified Wong Baker faces scale were utilised to evaluate gingival inflammation and patients' treatment satisfaction, respectively. Our findings revealed a reduction in the dental colour shade of the six cases between 2 and 10- fold (average of 3.5-fold) at T1 and maintained at T4, indicating significant improvement in the colour shade change with optimal outcomes. The percentage of this improvement for all the patients was ranged between 16.6% and 33.3%. At all timepoints, a "0" score was provided for pain intensity, dental hypersensitivity, and gingival inflammation. Our study demonstrates the feasibility and safety of a λ 450 nm laser delivered with a flattop handpiece to achieve optimal whitening outcomes without adverse effects. This offers a useful guide for dental clinicians for vital in-office tooth whitening. Extensive clinical studies with large data are warranted to validate our study protocol.

Photocatalytic Cascade Reaction Driven by Directed Charge Transfer over VS -Zn0.5 Cd0.5 S/GO for Controllable Benzyl Oxidation

Photocatalysis is an important technique for synthetic transformations. However, little attention has been paid to light-driven synergistic redox reactions for directed synthesis. Herein, the authors report tunable oxidation of benzyl to phenylcarbinol with the modest yield (47%) in 5 h via singlet oxygen (¹ O₂ ) and proton-coupled electron transfer (PCET) over the photocatalyst Zn_0.5 Cd_0.5 S (ZCS)/graphene oxide (GO) under exceptionally mild conditions. Theoretical calculations indicate that the presence of S vacancies on the surface of ZCS/GO photocatalyst is crucial for the adsorption and activation of O₂ , successively generating the superoxide radical (^• O₂ ^- ) and ¹ O₂ , attributing to the regulation of local electron density on the surface of ZCS/GO and photogenerated holes (h⁺ ). Meanwhile, accelerated transfer of photogenerated electrons (e^- ) to GO caused by the π-π stacking effect is conducive to the subsequent aldehyde hydrogenation to benzyl alcohol rather than non-selective oxidation of aldehyde to carboxylic acid. Anisotropic charge transport driven by the built-in electric field can further promote the separation of e^- and h⁺ for multistep reactions. Promisingly, one-pot photocatalytic conversion of p-xylene to 4-methylbenzyl alcohol is beneficial for reducing the harmful effects of aromatics on human health. Furthermore, this study provides novel insights into the design of photocatalysts for cascade reactions.