Severe maxilla-facial disharmonies need a complete three dimensional analysis.

This conference describes results of a social program financed by the French National Medical Insurance aimed at improving identification, diagnosis, follow-up and treatment of surgical cases. Participating orthodontists selected a group of 312 “border line surgery” patients who profited of CT scan exams. This work compared two sub-samples of patients with severe antero-posterior disharmonies evoking surgical direction (40 Class II and 34 Class III) with a reference sample (40 patients).

Patient’s CT scan data are treated by specific softwares elaborated in Toulouse using 14 maxillo-facial landmarks associated with trigeminal anatomy, and inertia matrices calculus to localize dental elements. This cephalometric analysis is able to describe the anatomy with three levels: alveolo-dental level/basic bones/global architecture or envelop.

The most determinant parameters and the threshold values are determined by statistical methods.

The importance of different kinds of parameters for surgical orientation can be classified:

• 1.

  Alveolo-dental parameters are more important than basic bone or architectural parameters.

• 2.

  Upper/lower gaps parameters are more important than position of whatever anatomical element.

• 3.

  Anterior landmarks are always more important than medium or posterior ones.

Beyond orthodontist’s comportment analysis, this work proposes an help for parameters selection and can give warning lights for surgical orientation.

The long term target was to define good practice behavior and to encourage orthodontists to avoid therapeutic relentlessness by not focusing too narrowly on orthodontic solutions. to the exclusion of other modalities such as surgery or to overuse orthodontic camouflage techniques:

• •

  Alveolo-dental parameters are more important than basic bone or architectural parameters.

• •

  Upper/lower gaps parameters are more important than position of whatever anatomical element.

• •

  Anterior landmarks are always more important than medium or posterior ones.

Conflict of interest: None declared.