Evaluation of Time-Dependent Force Decay in Memory and Conventional Orthodontic Elastomeric Chains: A Linear Regression Model
Cesar Mauricio-Vilchez, Franco Mauricio, Diego Galarza-Valencia, Alexandra Cadenillas, Sebastian Contreras, Fran Espinoza-Carhuancho, Frank Mayta-Tovalino
Abstract
Objective:
To evaluate the decay of force over time of memory and conventional elastomeric orthodontic chains in artificial saliva, Coca-Cola, and coffee.
Methods:
This was a prospective, longitudinal, and experimental study. A total of 540 elastomeric chain segments (American Orthodontics ® ) were allocated into six experimental groups according to the chain type (memory or conventional) and immersion medium. Each group consisted of 90 specimens that were repeatedly evaluated at baseline and after 1, 7, 14, 21, and 28 days. The chains were then mounted to custom acrylic templates and immersed every day in 250 mL of their assigned solution for 15 min and then stored in artificial saliva at 37°C. Force degradation was measured using a universal testing machine with a traction speed of 0.5 mm/s and a stretch of 25 mm.
Results:
Over the course of the 28-day immersion period, all types of chains showed a reduction in the amount of force produced. Although there was a greater amount of initial force generated by conventional chains when compared with memory chains, memory chains continued to maintain much larger amounts of residual force compared with conventional chains at the end of 28 days in all levels of immersion media tested. Using linear mixed-effects models, the analysis determined that the amount of force produced by conventional chains at the end of 28 days was significantly less than that produced by memory chains (
Conclusion:
Memory elastomeric chains demonstrated superior force retention and a slower rate of force decay than conventional chains throughout the 28-day period. Coffee significantly reduced force retention compared with artificial saliva, whereas Coca-Cola had no significant effect.