[Data analysis in long-term follow-ups of previously treated orthodontic patients].

The structure of former orthodontically treated patients, who underwent a long-term follow-up study in October 1989, was evaluated. An attempt was made to contact 1429 former patients, whereby 28.8% did not get the invitations because they had changed their address. As the compliance of approximately 17 years postretention of the 1,018 patients depends on change of address, job, interest and death, 20% of these were willing to participate and get examined. A structural conformity of the controlled group and the patient total cannot be presumed due to the patients' answers in the follow-up study. Questionnaires will be sent to patients, who did not participate in the analysis, in order to avoid unilateral results.