Force decay of elastomeric chain--a serial study. Part II.

This study was designed to evaluate the relaxation of elastomeric chain over time. The purposes were to compare the force decay curves of three variously stretched lengths, as well as to compare transparent and grey elastomeric chains. The elastomeric chains were fixed on a stainless steel framework that was submerged in 37 degrees C water bath for 6 weeks. The elastic forces of the chains were measured by a Dial-Type dynamometer, and recorded at the initial activation, first hour, eighth hour, twenty-fourth hour, third day, and then weekly to 6 weeks. The stretched length of the chains were decreased 0.5 mm per week. The results showed: (1) The sequence of stretch force at each time measurement of the Rocky Mountain clear energy chain was 40 mm > 35 mm > 30 mm. However, the percentage of remaining force was 40 mm < 35 mm < 30 mm. (2) The remaining force and the percentage of remaining force of the American Orthodontic short transparent chain were greater than the remaining force of the gray chain. (3) The remaining force and the percentage of remaining force of the Rocky Mountain clear chain with 40 mm stretch were greater than that of the American Orthodontic transparent and grey chains. (4) The effective force for canine retraction (184 gm) can be maintained by the Rocky Mountain energy chain with 40 mm, 35 mm, and 30 mm stretch for about 3 weeks, 1 week, and 3 days, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)