Abstract.Objective: This study aimed to evaluate cytotoxicity of three commercial brands of orthodontic elastomeric ligatures. Materials and Methods: The three commercial orthodontic elastomeric ligature brands were C-brand, T-brand and U-brand from different manufacturing countries. The cytotoxic assay was performed using cell cultures (L929) which were subjected to the cell viability test with methyl-tetrazolium (MTT). The L929 cell line was grown in 96-well tissue culture plates (1x10 5 cells/cm 3 ). Elastomeric ligatures (0.2 g) from each brand was placed in 1 ml of Minimum Essential Medium (MEM) at 37°C with 5% CO2 at 100% humidity in an incubator for 24 hours. After incubation, the cell mitochondrial activity was evaluated by the MTT test for detecting viable cells from optical density according to ISO 10993-5: 2009 (E) test procedure. Cytotoxic effects were determined by the percentage of cell viability. Results: Microscopic investigation showed that all commercial elastomeric ligatures caused alterations in the fibroblast cell morphology from an elongated to a spherical form. The cell viability of C-brand, T-brand and U-brand were 51.10, 73.04 and 93.04%, respectively. Conclusion: T-brand and U-brand orthodontic elastomeric ligatures were non cytotoxic potential. U-brand had the greatest cell viability and C-brand had the lowest cell viability at 24 hours.

Objective: The study aimed to compare dimensions and residual forces of various commercial type orthodontic elastomeric ligatures available in Thailand. Materials and Methods: The study compared 5 types of elastomeric ligatures: MU-MTEC, UnitekTM, MorelliTM, WelovehealthTM and DentsplyTM. A digital caliper was used to measure dimensions: the inner and outer diameters and cross-sectional thickness. Then the initial extension force and residual force on days 1, 2, 3, 4, 5, 6, 7, 14 and 28 were measured according to ISO 21606: 2007. The data were analyzed with the Kruskal-Wallis test and Spearmans rank correlation. Results: No significant difference was found between the outer diameter of MU-MTEC and WelovehealthTM. However, significant mean differences were found in dimensions among the other ligature types. The lowest mean for inner diameter and cross sectional thickness was found in UnitekTM and the lowest mean for outer diameter was found in MorelliTM. The highest mean inner diameter, outer diameter and cross sectional thickness was found in Dentsply, UnitekTM, and MorelliTM, respectively. In terms of initial extension force, significant differences (p<0.001) were found among all samples. The highest mean was found in DentsplyTM (2.69 N) and the lowest mean was found in WelovehealthTM (1.80 N). All samples had rapid force degradation at about 42.21-56.23% after 24 hours, with a slow degradation rate until Week 1 and a constantly stable rate from Weeks 1-4. The greatest force decay on the first day was found in MorelliTM (56.23%). At 28 days, the residual force for all types of elastomeric ligature was about 31.97-46.84%. Conclusion: All 5 brands of commercial elastomeric ligatures had different dimensions, initial extension forces and residual forces. The correlation between brand and dimension, initial extension force and residual force showed different patterns. All elastomeric ligatures had greater force decay on the first day (residual force 43.77 57.79%), then slightly decreased over 28 days.