Tensile Properties And Force Degradation Of Elastomeric Chains In Vitro

Objective:The purpose of the study was to reveal the stretched length when different kinds of elastomeric chains were stretched to produce the intended force , and to evaluate the influence patterns of such factors as the type of filament,number of loops,initial force on force degradation of elastomeric chains, in order to provide some useful information for clinical practice.Methods:The elastomeric chains tested in this study included four kinds of filament types: small, mini, medium and large. Each type of the elastomeric chains were all cutted into two, three, four, five loops. And various chains were stretched to produce the initial force of 100g, 150g, 200g, 250g, the stretched length was measured by an Instron Universal Testing Machine. Then arranged the experiment groups by the orthogonal design, and the stretched length of different groups of chains were maintained respectively in artificial saliva environment of 37℃. The remaining force of the chains were recorded at the different moment in 4 weeks. Then calculated the percentage of remaining force, and analysed the results.Results:1. Within the force of 250g, the stretched length approximately linearly increased while the stretch force increased. When the stretched force was 100g, the stretched length of various chains was between 0.67~2.05mm. And the stretched length of the chains increased 0.3～1 mm per 50g stretched force. When given the same stretched force, the strerched length of small, mini, medium, large filament types and 2, 3, 4, 5 loops was increased in sequence. 2. All groups of elastomeric chains degraded the most force at the initial 4 hours, the percentage of remaining force was between 60% and 90%. The force of chains still degraded quickly at first 24 hours, the percentage of remaining force was between 50% and 80%. And then the force degraded slowly, the percentage of remaining force after 4 weeks was between 40% and 70%.3. The influence of filament and loops on force degradation of elastomeric chains was statistically significant, the percentage of remaining force of medium, mini, small, large filament types was increased in sequence, and the percentage of remaining force of 2, 3, 4, 5 loops was increased in sequence. Whereas the differences of various initial force showed no statistical significant.Conclusions:1. When given the same stretched force, types of filament and number of loops had obviously influence on the stretched length, and when the stretched length of various elastomeric chains was adjusted slightly, the force of chains would change significantly. So while elastomeric chains applied to clinical treatments, it is important to use the dynameter for the precise force.2. The force of all groups of elastomeric chains degraded most quickly within the initial 4 hours , and the degradation tended to stable after 24 hours.3. Under the same conditions, the shorter the filament, the more slowly the force degraded. As the number of loops increases, the force degradation rate decreases. Within the force of 250g, the initial force has no influence on force degradation rate.