Estudo in vitro da degrada？？o da for？a de elásticos ortod？nticos de látex sob condi？？es dinamicas

aim: to analyze 3 sizes of latex orthodontics elastics (1/8", 3/16" and 5/16"), all classified as heavy force by their manufacturers, of the following commercial brands: dental morelli, 3m unitek corporation and american orthodontics. methods: through a developed device, the elastics bands were distended 26mm (position of rest of the mandible) and submerged in artificial saliva to 37oc. every minute they were prolonged to 44mm (simulation of mandibular movements) and after 1 second they returned to 26mm. measurements were accomplished in intervals of varied times. in the periods considered as meals time (3 times a day), the elastics bands were removed of the device and kept in an acrylic box, and in the period considered as nocturne the pneumatic device was turned off and the elastics bands were stretched in 26mm. results: the larger force degradation happened in the first 2 hours for the whole sample. conclusion: the elastics bands presented significant statistic differences in relation to thickness and width; and the 1/8" elastics bands should be changed at least every 24 hours and the 3/16" and 5/16" elastic bands can be changed every 72 hours, if force levels similar to the initials are desired.