A Study Of Force Degradation Of Orthodontic Elastomeric Chains:A Study In Vivo

Objective To evaluate the characteristics of force degradation and effects of elastomeric chains in oral cavity and vitro during the time.Methods In vitro study,4-unit elastomeric chains with the initial force 200g were set both in dry air and artificial saliva.The volunteers wear clear retainers which were used to hold the sample of 2-unit,4-unit,pre-stretched 4-unit and 6-unit elastomeric chains with the initial force 200g in vivo.After the first 4 weeks,4-unit specimens were stretched to 200g again for the second 4 weeks in vivo.At each measurement time intervals,the force value and the percentage of force degradation in vivo and vitro groups were recorded.Results Both vitro and vivo study had similar tendency of force degradation.There was a sharply force degradation within 4 hours,followed by a more stable phase after 1 week.The average force degradation of 4-unit specimens after 4 weeks was in vivo(64.76%),artificial saliva(55.00%),dry air(46.42%).In vivo study,the more number of units,pre-stretched treatment and reused the elastomeric chains were decreased less the elastomeric chains of force degradation than the regular style.Conclusion The force degradation of elastomeric chains in vivo was greater than in vitro.In order to decrease the degradation rate of elastomeric chains,increasing the number of units,using pre-stretched treatment and reusing the elastomeric chains were suggested in clinical.