Backround: The in vitro cytotoxic effects of six different clear aligner materials were evaluated using the MTT analysis. Methods: The clear aligner material samples [Duran (ScheuDental GmbH, Iserlohn, Germany), Zendura-Flx (Bay Materials LLC, Fremont, CA, USA), Taglus (Laxmi Dental Export Pvt. Ltd, Mumbai, India), Smart Track (Align Technology, San Jose, CA, USA), Zendura (Bay Materials LLC, Fremont, CA, USA), Essix C + (Essix ^® (Raintree Essix, Inc., 4001 Division St, Metairie, LA-USA)] were initially kept in a saline solution in airtight test tubes for 8 weeks at 37°C. According to the recommended ISO standards, the weights of the samples were divided by the volumes of the dilutions in the ratio of 0.1 g/ml. To evaluate the cytotoxicity of the samples, an MTT analysis was performed using a human gingival fibroblast cell line (HGF). To analyse the data, the Kruskal– Wallis test was applied (a=0.05). Results: Zendura was the most cytotoxic material resulting in 67.3 ± 16.20% cell viability, followed by Smart Track with 87.6 ± 5.53% cell viability. While Duran, Essix C + had 92.6 ± 26.34% and 94.9 ± 8.54% cell viability, Zendura-Flx, Taglus had 106.9 ± 12.76% and 113.183 ± 7.45% cell viability, respectively. Conclusion: While Zendura and Smart Track showed mild cytotoxicity, other materials showed greater cell viabilities. According to the ISO standards, the clinical use of each brand of aligners, except Zendura, may be considered reliable. Taking into account standard deviation, Zendura and Duran should be used with caution. The suppliers of aligners should adhere to the manufacturer’s recommendations since an increase in ion release might arise from material wear.

Background: The purpose of this study was to assess the effects of systemically given krill oil (KO) on the development of new bone formation in the sutura palatina media following rapid maxillary expansion (RME). Methods: 28 4–5 week-old male Wistar albino rats were randomly divided into 4 groups: Control (C), Only Expansion (OE) (no supplement but undergoing expansion and retention), KE (supplemented during both the expansion and retention phases), Krill Oil Nursery Group (KN) (supplemented during the 40-day nursery phase as well as during the expansion and retention phases). A 5-day RME was followed by a 12-day retention period. All rats were euthanized simultaneously. Micro-computerized tomography (Micro-CT), hemotoxylen-eosin (H&E) staining, and immunohistochemical analysis were conducted. Kruskal-Wallis and Dunn tests with Bonferonni corrrection were applied (p < 0.05). Results: Expansion and KO supplementation did not cause a statistically significant change in bone mineral density (BMD), bone volume fraction (BV/TV), spesific bone surface (BS/BV) and trabecular thickness (Tb.Th). While the expansion prosedure increased the trabecular seperation (Tb.Sp), KO supplemantation mitigated this effect. The KE group exhibited a statistically significantly increase in trabecular number (Tb.N) compared to the OE group. Although receptor activator of nuclear factor-kappa-Β ligand (RANKL)/osteoprotegerin (OPG) ratios did not show significant differences between groups, the KE and OE groups demonstrated the lowest and highest value, respectively. KE showed a reduced amount of tartrate-resistant acid phosphatase (TRAP) compared to the OE. Conclusion: KO positively affected the architecture of the new bone formed in the mid-palatal suture. In this rat model of RME, results support the idea that administering of KO during the expansion period or beginning before the RME procedure may reduce relapse and enhance bone formation within the mid-palatal suture.