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Early diagnosis of caries and tooth enamel microcracks is of great importance for preventing the destruction of healthy tooth enamel. Inorder to detect microcracks in the enamel and pathogenic microflora foci that can cause caries, nanoform of aluminum phthalocyanine (AlPc) can be used as a marker. In a colloidal solution, the nanoparticles do not fluoresce, unlike their molecular form. To convert the particle into its molecular form, it is necessary to have a solvent or specific environment (bacteria, macrophages, etc.). That is why the hydrophobic nanoparticles of aluminum phthalocyanine (nAlPc) can act as markers for detecting hidden pathogenic microflora during fluorescent diagnostics. Further reduction of the diagnosis time and increase the efficiency can be achieved by using biologically compatible surfactants as additional activators of nAlPc.In order to carry out local fluorescence spectroscopy of enamel microcracks and pathogenic microflora foci on the enamel surface, a model compound containing surfactants, auxiliary components and nAlPc colloid at a concentration of 10 mg/l was prepared.Studies on the interaction of the model compound with nAlPc and Protelan MST-35 with tooth enamel ex vivo have shown this surfactant to be a promising auxiliary activator of the nanoparticles, allowing conducting local fluorescence spectroscopy of the tooth enamel surface 3 min after application. In addition, statistical processing of the results showed the effectiveness of using the model compound for local fluorescence spectroscopy of the enamel surface in order to detect the enamel microcracks and the pathogenic microflora accumulation foci that can lead to the development of a cariogenic process.

Objectives: This study aimed to compare the bond strength and enamel damage following debonding of metal brackets cured by different light-curing modes: conventional, soft start, and pulse delay modes., Material and Methods: Sixty extracted upper premolars were randomly divided into three groups according to the used light-curing mode. Metal brackets were bonded with a light-emitting diode device employing different modes. Group 1: conventional mode (10s mesial+10 s distal); group 2: soft start mode (15s mesial+15s distal); group 3: pulse delay mode (3s mesial+3s distal, followed by 3min of no photoactivation, then 9s mesial+9s distal). Radiant exposure was the same in all study groups. Shear bond strengths of the brackets were tested with a universal testing machine. A stereomicroscope was used to determine the number and length of enamel microcracks. One-Way ANOVA and Kruskal-Wallis tests were used to detect significant differences in shear bond strength and microcracks number and length among groups., Results: The soft start and pulse delay modes produced significantly greater shear bond strength than the conventional mode (19.46±4.90MPa; 20.47±4.97MPa; 12.14±3.79MPa, respectively, P<0.001). However, there was no significant difference between the soft start and pulse delay groups (P=0.768). The number and length of microcracks increased significantly after debonding in all study groups. The change in microcracks length was not different among study groups., Conclusion: The soft start and pulse delay modes produced greater bond strength than the conventional mode without predisposing enamel to higher risk of damage. Conservative methods for debonding are still required., (Copyright © 2023 CEO. Published by Elsevier Masson SAS. All rights reserved.)