Interlabial gap behavior with time

BackgroundThe purpose of this study was to evaluate the long-term behavior of the interlabial gap in patients with Class I and Class II malocclusion after orthodontic treatment and to investigate whether interlabial gap behavior is related to treatment with or without extraction.MethodsLateral head-films at the pre- and post-treatment and long-term follow-up stages were obtained from 61 patients who initially had Class I or Class II malocclusion and with pre- and post-treatment lip incompetence, who were treated with or without extraction. Dependent and independent Student's t tests were used for the intra- and intergroup comparisons.ResultsThere were significant interlabial gap reductions of 1.64 and 1.72 mm in Class I and II, respectively, but there was no significant intergroup difference. Nonextraction patients had significantly greater interlabial gap reduction (2.7 mm) than did extraction patients (1.3 mm) in the long-term.ConclusionsIt was concluded that the interlabial gap decreases significantly and similarly in treated Class I and Class II malocclusion patients and that nonextraction treatment has greater interlabial gap reduction than does extraction treatment in the long-term post-treatment period.