Effects of abutment diameter, luting agent type, and re-cementation on the retention of implant-supported CAD/CAM metal copings over short abutments

PURPOSE: The aim of this study was to evaluate the effects of abutment diameter, cement type, and re-cementation on the retention of implant-supported CAD/CAM metal copings over short abutments. MATERIALS AND METHODS: Sixty abutments with two different diameters, the height of which was reduced to 3 mm, were vertically mounted in acrylic resin blocks with matching implant analogues. The specimens were divided into 2 diameter groups: 4.5 mm and 5.5 mm (n=30). For each abutment a CAD/CAM metal coping was manufactured, with an occlusal loop. Each group was sub-divided into 3 sub-groups (n=10). In each subgroup, a different cement type was used: resin-modified glass-ionomer, resin cement and zinc-oxide-eugenol. After incubation and thermocycling, the removal force was measured using a universal testing machine at a cross-head speed of 0.5 mm/min. In zinc-oxide-eugenol group, after removal of the coping, the cement remnants were completely cleaned and the copings were re-cemented with resin cement and re-tested. Two-way ANOVA, post hoc Tukey tests, and paired t-test were used to analyze data (α=.05). RESULTS: The highest pulling force was registered in the resin cement group (414.8 N), followed by the re-cementation group (380.5 N). Increasing the diameter improved the retention significantly (P=.006). The difference in retention between the cemented and recemented copings was not statistically significant (P=.40). CONCLUSION: Resin cement provided retention almost twice as strong as that of the RMGI. Increasing the abutment diameter improved retention significantly. Re-cementation with resin cement did not exhibit any difference from the initial cementation with resin cement.

[Evaluation of the antibacterial activity of annatto dye on some pathogenic bacteria]

Today, disadvantages of antibiotics and synthetic preservatives have been identified, and researchers are seeking natural and safe alternatives. Annatto dye is one of the commonly used dyes in the food industry, which has antimicrobial and antioxidant properties. The objective of this study was to determine the antimicrobial effect of annatto dye on some pathogenic bacteria. In this study, annatto dye was extracted from annatto seeds by maceration methods and after filtration, it was powdered by vacuum oven. Antimicrobial activity was evaluated by disc diffusion method and the minimum inhibitory concentration [MIC] and minimum bactericidal concentration [MBC] were determined using agar dilution method against Staphylococcus aureus, listeria innocua, Bacillus cereus and Salmonella enteritidis. In this study, Bacillus cereus and Salmonella enteritidis, respectively, showed the highest and the lowest sensitivity to annatto dye. S. enteritidis had the highest MIC among the tested bacteria, and MBC was not observed only for S. enteritidis in the tested concentrations of annatto dye. According to the results of this study, annatto dye was effective on the growth of all tested bacteria. Also, annatto dye had more antimicrobial effect on the tested gram-positive bacteria compared to gram-negative bacteria. Thus, considering the results of the experiment, annatto dye can be used as an inhibitor of bacterial growth