Treatment decision in adult patients with bimaxillary protrusion: Orthodontic therapy or Orthognathic surgery?

Objectives: A bimaxillary protrusion is a condition in which the maxillary and the mandibular incisor teeth protrude severely so that the lips cannot be closed together. Because not all bimaxilary protrusion patients are candidates for surgical correction, patient assessment and selection remain main issues in diagnosis and treatment planning. The purpose of this study was to separate bimaxilary protrusion patients who can be properly treated orthodontically from those who require orthognathic surgery.

Methods: A large sample size was a necessary to obtain a sufficiently robust model. Thus, a multicentric study design was chosen The cephalograms of 86 adult patients with bimaxilary protrusion malocclusions were analyzed. The orthodontic group comprised 69 patients, and the surgery group 17 patients. Twelve linear, proportional, and angular measurements were made. Stepwise discriminant analysis was applied to identify the dentoskeletal and soft-tissue variables that best separate the groups.

Results: The discriminant function model was highly significant (P <0.001); 94% of the patients were correctly classified. The following variables were extracted: LLP,the maxillary incisor to mandibular incisor angle(-1),the mandibular incisor to line NB(1-NB),ULP . The resulting equation was: Individual score =-40.574+0.362*( LLP)+0.575*(-1) +0.347*( 1-NB)-0.879*(ULP).

Conclusion: By means of discriminant analysis, correct classification of adult bimaxillary protrusion patients succeeded to a very high degree. Bimaxillary protrusion patients want instant esthetic facial results and that their soft tissue profile should be more regard than hard tissue. Of all the variables, the LLP  was the most decisive parameter.