AN ANALYSIS OF THE CORROSION PROCESS OF THE NOVA-T IUD

Objective: To measure the copper from Nova-T IUDs that have been used for up to 9 years. To examine the composition and extent of surface de posits on these used IUDs. Design: Nova-T IUDs were randomly collected at normal replacement or removal. The copper, silver and calcium cont ent was quantified by X-ray fluorescence; surface topography and analy sis was by scanning electron microscopy and X-ray dispersive analysis. Results: Copper loss slowly increased at an exponential rate over the study period but the copper was stabilized by the silver core and did not show increased fragmentation with extended use. No corrosion of t he silver core was detected. Calcium- and sulfur-containing surface de posits built up on the copper but did not modify the rate of copper re lease. Conclusions: The mean rate of copper loss was 0.25 mu mol/day d uring the first 40 months of use, which is not significantly different from that of similar IUDs without a silver core. The silver core of t he copper coil on the Nova-T IUD prevented its fragmentation. Surface deposits containing calcium and sulfur that built up on the IUD did no t affect the rate of copper loss.