After the 6 - month surgery: all groups have increased hearing level and increase the highest in group 3, group 1 followed by group 2 (mean PTA after surgery compared to before surgery: 41.67% compared to 53.33%, 30.32% compared to 39.21%, 40.82% compared to 42.07%) (mean hearing gain after surgery compared to before surgery: 11.67, 8.89, 1.25).