A clinical evaluation of long term retention with bonded retainers made from multi-strand wires

The majority of patients from 4 orthodontic clinics in the south west of Sweden who have had bonded retainers on upper or lower anterior teeth for a period of at least 5 years were examined. The total failure rate during 5 years of observation was 36 per cent, slightly higher in the maxilla than in the mandible. The retainer had become detached in 15 per cent of the teeth bonded. The failure rate decreased during the 5 year period of observation. Seven fractures were reported, all in the upper front teeth. The failure rate was reduced when the retainers were positioned incisally, when larger diameter wires were used and in the 12 cases where a groove had been cut into the enamel to accept the retainer. The findings suggest that a limited flexibility of the retainer may be an advantage. In about 20 per cent of the retained segments minor rotations and small areas of space opened between some of the teeth attached to the retainer. No new caries lesions were found on any of the teeth associated with the bonded retainers during the period of observation.