Purpose:The aim of this study was to determine the effect of solid (one-piece) and two-piece abutments on the stress profile of narrow implants with marginal bone loss. Materials and Methods: Solid and two-piece abutments were connected to a conical internal octagon-connection implant (3.3 mm in diameter, 10 mm in length) and restored with a single crown. Three-dimensional finite element analysis was used to simulate the stress distribution in implant models with different levels of marginal bone resorption (0, 1, 2, and 3 mm). The effect of the design variables under increased bone resorption scenarios, including abutment screw length and diameter, were assessed. Static loading was applied to determine the mechanical response of the implant and cortical and trabecular bone. Results: Marginal bone resorption levels dominated the mechanical response under static loading conditions. A marginal bone loss of 3 mm significantly increased stress values in the implant vicinity and abutment screw. Both abutment designs displayed similar stress distribution in the surrounding bone, but lower stress values were observed in the implant body with two-piece abutments. The abutment screw length was more effective in the resultant stress, as the longer screws reduced the stress in the implants. Conclusion: Marginal bone resorption magnitude is the crucial parameter in biomechanics to determine the mechanical behavior. As bone loss increases, resultant stress around implants under mastication forces may lead to implant failure, regardless of abutment type.

Summary Background/Aim: A factor affecting the success rate of dental implants, which has been used successfully for many years, is the implant-abutment connection system. The purpose of this study was to evaluate the stress distribution of different implant-abutment connection systems under different forces. Material and Methods: This in vitro study included a finite element analysis. In the study, the cylindrical and screwed dental implants available in 3 different diameters from 4 different companies were categorized into 12 different models. Two different scenarios of force application were conducted on each model in this study. In the first scenario, 100 N force and 100 N moment were applied in a vertical direction onto a point considered as the center of each tooth. In the second scenario, a 100 N force and moment were applied at a 45° angle in an oblique direction. Results: As a result of the forces applied to dental implants of different diameters from different companies, octagon implant-abutment connection systems had less stress accumulation than hexagon implant-abutment connection systems. In addition, when stress accumulation ratios were evaluated according to the diameter of the implants used, it was observed that 3 mm diameter implants accumulated more stress in bone than 4 mm diameter implants; there was no significant difference between 4 mm diameter implants and 5 mm diameter implants. Conclusions: Implant-abutment connection system is important for the longevity of implants under the forces. Therefore, this factor should be considered during implant selection.

No abstract

No abstract

The effectiveness of antifungal agents may be insufficient against resistant strains in some cases of oral candidiasis. The aim of this study was to evaluate the antifungal effect of thymoquinone against Candida albicans , Candida tropicalis , Candida glabrata and Candida krusei strains and the synergistic antifungal activity of these strains in combination with nystatin. To evaluate in vitro antifungal activity and interactions between thymoquinone and nystatin, substances were tested against Candida albicans ATCC 10,231, C. tropicalis ATCC 750, C.krusei ATCC 6258 and C. glabrata ATCC 2001 standard strains both individually and combinationally via microdilution method. MIC and ΣFIC index value were analysed. The Kruskal Wallis test and Bonferroni test were used for statistical evaluations. Statistical significance was set at p < 0.05. A statistically significant difference was observed between the mean ranks of all Candida species and doses of thymoquinone, nystatin, and the combination thymoquinone-nystatin ( p < 0.05). MIC values for thymoquinone were determined as 15 μg/mL for C. albicans , C. tropicalis and C. krusei while it was 30 μg/mL for C. glabrata . Moreover, MIC for nystatin was found as 1.875 μg/mL for C. albicans , C. tropicalis and C. krusei , whereas it was 7.5 μg/mL in C. glabrata. Interaction assays and ΣFIC index value revealed that, TQ and nystatin have a synergistic effect against to all strains. Thymoquinone was found to have antifungal activity on Candida species and synergistic effect when combined with nystatin.