Comparison of Dimensions and Residual Forces of Various Orthodontic Elastomeric Ligatures

Abstract

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.