Corrosion of filamentous intra-uterine copper. The MLCu250 and the MLCu375.

Although the effective life span of an IUD provided with filamentous copper is, calculated on the basis of the rate of dissolution of copper, several years, corrosion may lead to breakage of the wire after a shorter period of use. When copper wire with a diameter of 0.20 to 0.25 mm is used, the proportion of IUDs with broken wires increases with time after three years of use. It was not known whether this disadvantage could be reduced or eliminated by the use of a thicker wire. In this study the corrosion behaviour was observed in MLCu250 and MLCu375 devices, which have copper wire with a diameter of 0.30 and 0.40 mm, respectively. The earliest breakage was observed after 8 months of use for 0.30 mm wire and after 9 months of use for 0.40 mm wire. In IUDs with 0.30 mm wire the proportion with broken wires increased after 3 years of use. Since examples of the MLCu375 with 0.40 mm wire used for more than 3 years were few, it was impossible to make definite conclusions in this respect. In general, the corrosion behaviour in copper diameter range of 0.3 to 0.4 mm is the same as indicated in previous studies for diameter range of 0.2 to 0.25.