[Factors on force degradation of elastomeric chains in vitro]

To evaluate the influence of factors of type of filament, number of loops, initial force on force degradation of elastomeric chains.

The chains of different type of filament and number of loops were stretched to produce specified initial force,and the stretched length of different groups of chains was maintained in artificial saliva of 37 degrees centigrade. The remaining force were recorded at some appointed moment in 4 weeks. Then the percentage of remaining force was calculated and the statistical processed with analysis of variance using SPSS 11.5 software package.

The percentage of remaining force was between 60% and 90% at the initial 4 hours, between 50% and 80% at first 24 hours, and between 40% and 70% after 4 weeks. The influence of filament and loops was statistically significant (P<0.01).The percentage of remaining force of medium, mini, small, large filament types increased in sequence, and 2, 3, 4,5 loops increased in sequence.Whereas the differences of various initial force were not significant (P>0.05).

The force of all groups of elastomeric chains degrades most quickly within the initial 4 hours, and the degradation tends to be stable after 24 hours.The shorter the filament, the more slowly the force degrades. As the number of loops increases, the force degradation rate decreases. The initial force has no impact on force degradation rate.