Immediate and Delayed Effects of Diode Laser on Debonding of Ceramic Brackets: An in vitro Study.

AIM: The aim of the study is to evaluate the immediate and delayed effects of diode laser on debonding of ceramic brackets. MATERIALS AND METHODS: A total of 60 human extracted premolar teeth were randomly assigned to three different treatment groups. All teeth were bonded with adhesive precoated (APC) ceramic brackets (3M Unitek). A total of 20 teeth were debonded without lasing (group 1), 20 immediately after lasing (group 2), and 20 1 hour after lasing (group 3). For the lasing groups (groups 2 and 3), access cavity was prepared on the occlusal surface to a 2 mm diameter. A transbond plus self-etching primer (3M Unitek, Monrovia, CA, USA) and APC PLUS clarity advanced brackets (3M, Unitek, Monrovia, CA, USA) were used. The shear bond strength (SBS) and adhesive remnant index (ARI) were measured. The internal pulpal wall temperature was noted for the laser groups. RESULTS: The mean SBS was 15.4, 11.57, and 11.79 MPa for groups 1 to 3 respectively. Post hoc test showed significant difference (p < 0.001) between the control group and the lased groups. For groups 2 and 3, the rise in temperature was at an average of 1.4 and 1.3°C respectively. CONCLUSION: The SBS of APC brackets decreased by 33.3% on application of diode laser without increasing the internal pulp chamber wall temperature significantly. Shear bond strength remains more or less the same whether debonding is done immediately after lasing or 1 hour after lasing. Diode lasers increased the ARI scores and thus decreased the risk of enamel fracture.

Sequential interactions of silver-silica nanocomposite (Ag-SiO2 NC) with cell wall, metabolism and genetic stability of Pseudomonas aeruginosa, a multiple antibiotic-resistant bacterium.

UNLABELLED: The study was carried out to understand the effect of silver-silica nanocomposite (Ag-SiO(2) NC) on the cell wall integrity, metabolism and genetic stability of Pseudomonas aeruginosa, a multiple drug-resistant bacterium. Bacterial sensitivity towards antibiotics and Ag-SiO(2) NC was studied using standard disc diffusion and death rate assay, respectively. The effect of Ag-SiO(2) NC on cell wall integrity was monitored using SDS assay and fatty acid profile analysis, while the effect on metabolism and genetic stability was assayed microscopically, using CTC viability staining and comet assay, respectively. Pseudomonas aeruginosa was found to be resistant to ß-lactamase, glycopeptidase, sulfonamide, quinolones, nitrofurantoin and macrolides classes of antibiotics. Complete mortality of the bacterium was achieved with 80 µg ml(-1) concentration of Ag-SiO(2) NC. The cell wall integrity reduced with increasing time and reached a plateau of 70% in 110 min. Changes were also noticed in the proportion of fatty acids after the treatment. Inside the cytoplasm, a complete inhibition of electron transport system was achieved with 100 µg ml(-1) Ag-SiO(2) NC, followed by DNA breakage. The study thus demonstrates that Ag-SiO(2) NC invades the cytoplasm of the multiple drug-resistant P. aeruginosa by impinging upon the cell wall integrity and kills the cells by interfering with electron transport chain and the genetic stability. SIGNIFICANCE AND IMPACT OF STUDY: Although the synthesis, structural characteristics and biofunction of silver nanoparticles are well understood, their application in antimicrobial therapy is still at its infancy as only a small number of microorganisms are tested to be sensitive to nanoparticles. A thorough knowledge of the mode of interaction of nanoparticles with bacteria at subcellular level is mandatory for any clinical application. The present study deals with the interactions of Ag-SiO2NC with the cell wall integrity, metabolism and genetic stability of Pseudomonas aeruginosa, which would contribute substantially in strengthening the therapeutic applications of silver nanoparticles.