[The determination of the level of the external osteotomy line in Le Fort I interventions for pure maxillary advancement].
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. In this paper were considered patients operated by orthognathic surgery from January 1994 to June 1997 have been studied. Patients were operated in the Institute in which authors work. Patients included were 120, 65 female and 55 male between 20 and 42 (mean 31). 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. 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. 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.