[The determination of the level of the external osteotomy line in Le Fort I interventions for pure maxillary advancement].

Background: Therapy of severe malocclusions needs a cooperation between orthodontist and maxillo-facial surgeon. The aim of this study is to evaluate how the ortho-surgical team can get a common base of programmation to transfer on split-casts osteotomic simulation reaching a more exact surgical result.

Methods: In this paper were considered patients operated by orthognathic surgery from January 1994 to June 1997 have been studied.

Environment: Patients were operated in the Institute in which authors work.

Patients: Patients included were 120, 65 female and 55 male between 20 and 42 (mean 31).

Operations: Patients were operated, for the most part, by combined operation at maxilla and mandible. RECORDINGS: The mean of values noticed was calculated adding all values and dividing for the number of values.

Results: The mean calculated is 33 mm (DS 2,22) of distance from canine cusp and 29 mm (DS 2,19) from mesio-vestibular cusp of the first upper molar.

Conclusions: This study demonstrates that it is possible, with a statistically significant precision, to transfer osteotomic reference lines from clinical practice to a planning more pertinent to surgical performance. In this study we tried to standardize a value to increase precision of surgery, transferring easily feasible surgical measurements to split-casts.