Effect of combined digital imaging parameters on endodontic file measurements.

INTRODUCTION: This study assessed the effect of the combination of a dedicated endodontic filter, spatial resolution, and contrast resolution on the determination of endodontic file lengths. METHODS: Forty extracted single-rooted teeth were x-rayed with K-files (ISO size 10 and 15) in the root canals. Images were acquired using the VistaScan system (Dürr Dental, Beitigheim-Bissingen, Germany) under different combining parameters of spatial resolution (10 and 25 line pairs per millimeter [lp/mm]) and contrast resolution (8- and 16-bit depths). Subsequently, a dedicated endodontic filter was applied on the 16-bit images, creating 2 additional parameters. Six observers measured the length of the endodontic files in the root canals using the software that accompanies the system. The mean values of the actual file lengths and the measurements of the radiographic images were submitted to 1-way analysis of variance and the Tukey test at a level of significance of 5%. The intraobserver reproducibility was assessed by the intraclass correlation coefficient. RESULTS: All combined image parameters showed excellent intraobserver agreement with intraclass correlation coefficient means higher than 0.98. The imaging parameter of 25 lp/mm and 16 bit associated with the use of the endodontic filter did not differ significantly from the actual file lengths when both file sizes were analyzed together or separately (P > .05). When the size 15 file was evaluated separately, only 8-bit images differed significantly from the actual file lengths (P ≤ .05). CONCLUSIONS: The combination of an endodontic filter with high spatial resolution and high contrast resolution is recommended for the determination of file lengths when using storage phosphor plates.

Eficácia da terapia fotodinâmica antimicrobiana em biofilmes de Staphylococcus aureus suscetível e resistente á meticilina / Antimicrobial photodynamic therapy effectiveness against susceptible and methicillin-resistant Staphylococcus aureus biofilms

A necessidade de superar o desafio criado pelos biofilmes resistentes aos tratamentos antimicrobianos convencionais tem levado à busca por tratamentos alternativos, como terapia fotodinâmica antimicrobiana (aPDT). Este estudo avaliou in vitro a eficácia da aPDT na inativação de biofilmes de Staphylococcus aureus suscetíveis e resistentes à meticilina (MRSA e MSSA), mediado pelos fotossensibilizadores (PSs) Curcumina (Cur) e Photodithazine® (PDZ). Biofilmes foram formados e tratados com diferentes concentrações de Cur (0, 20, 40 e 80 μM) e PDZ (0, 50 e 75 mg/L), e iluminados ou não por fonte de luz LED (Cur 455 ± 3 nm/ 5,28 J/cm2; PDZ 660 ± 3 nm/ 5,28 J/cm2 ou 50 J/cm²). Os grupos Controle Positivo (CP) não receberam nenhum PS e também não foram iluminados. A viabilidade dos micro-organismos após a aPDT foi avaliado pelo número de colônias viáveis, pelo ensaio de XTT e pela utilização do kit LIVE/DEAD® na Microscopia Confocal de Varredura à Laser (MCVL). Os resultados foram avaliados por análises de variância de dois fatores de efeitos fixos (ANOVA) e complementados por comparações múltiplas de médias pelo teste de Tukey. Para ambas as cepas, todas as concentrações de Cur e PDZ testadas reduziram significativamente a atividade metabólica e o UFC/mL para ambos micro-organismos quando comparado com os grupos CN (p0,05). Os resultados foram otimizados para a Cur quando utilizou-se a maior concentração (80 μM), para a PDZ, a maior redução nos micro-organismos foi observada quando associou-se a maior concentração de PDZ (75 mg/L) com a maior dose de luz (50 J/cm²). Os biofilmes submetidos a aPDT demostraram pela MCVL um maior número de células coradas em vermelho, indicando que a aPDT foi eficaz para promover danos ou morte às células bacterianas. Assim, a aPDT pode ser considerada promissora para atuar de forma sinérgica no tratamento de infecções bacterianas

The need to overcome the challenge created by biofilms regarding conventional antimicrobial approaches has lead to search of alternative treatments such as Antimicrobial Photodynamic Therapy (aPDT). This in vitro study evaluated the efficacy of aPDT using the photosensitizer (PS) Curcumin (Cur) and Photodithazine® (PDZ) in the inactivation of biofilms of methicillin susceptible and resistant S. aureus (MSSA and MRSA). Biofilms were treated with different Cur (0, 20, 40 or 80 µM of Cur) and PDZ concentrations (0, 50 or 75 mg/L) and illuminated or not with LED source (Cur 455 ± 3 nm/ 5.28 J/cm2 ; PDZ 660 ± 3 nm/ 5.28 J/cm2 or 50 J/cm²). Positive control samples were not exposed to PS or light. The microorganisms viability after aPDT were evaluated by counting the number of colonies, the XTT assay and LIVE/DEAD® staining using confocal laser scanning microscopy (CLSM). The results were evaluated by analysis of variance, two-factor fixed effects (ANOVA) and complemented by multiple comparisons by Tukey test. For both strains, all the tested Cur and PDZ concentrations reduced significantly both biofilm metabolic activity and CFU/mL compared to the negative control (p 0.05). Moreover, the results were optimized for Cur when the higher concentration was used (80 µM); For PDZ, the best results were obtained when it was associated a higher concentration of PDZ (75 mg/L) with the higher dose of light (50 J/cm²). Biofilms submitted to aPDT showed a large number of red-stained colonies, indicating that this therapy was efficient in disrupting the bacterial membrane. It can be concluded that PS was efficient in reducing viable colonies of both S. aureus strains by damaging cell membrane and causing cell death. Thus, the aPDT is can be considered promising to act synergistically in the treatment of bacterial infections