Effect of citric acid on force decay of orthodontic elastomeric chains

Abstract

Background: This study aimed to assess the effect of citric acid, as a weak acid commonly used
in food industry, on elastomeric chain force decay.
Materials and Methods: In this in vitro, experimental study, sixty elastomeric chains from two
commercial brands of American Orthodontics and Ortho Technology (n = 30) were cut into five‑piece
segments. Elastomeric chains of each brand were randomly divided into two groups of control (artificial
saliva) and citric acid. All elastomeric chains were incubated in artificial saliva at 37°C. Experimental
samples were immersed in 10 mL of citric acid for 90 s daily and were then transferred back to the
artificial saliva. The elastomeric chain force was measured at baseline (before the experiment), 1 day,
1 week, 2 weeks, and 3 weeks using an electromechanical universal testing machine. Data were analyzed
using t‑test, Kruskal–Wallis test, and Mann–Whitney U‑test at 0.05 level of significance.
Results: The elastomeric chain force gradually degraded over time. The difference in this respect was
not significant at 2 and 3 weeks in any group (P > 0.05). On initiation of the experiment, the force
in the citric acid group experienced a greater decay than that in the control group; the difference
between the citric acid and control groups in both the brands was significant at all time points until
the end of the 3rd week (P < 0.05). The difference between the American Orthodontics and Ortho
Technology brands in the control and citric acid groups was significant at all time points (P < 0.001).
Conclusion: Elastomeric chains in both the citric acid and artificial saliva groups experienced force
decay over time. Force decay was greater in the citric acid group. Thus, citric acid can effectively
decrease the elastomeric chain force. The Ortho Technology chain force was higher than that of
American Orthodontics in both the groups at all time points.
Key Words: Biodegradation, citric acid, elastomeric