Introduction: The aim of this study was to evaluate whether a 6° counterclockwise change in occlusal plane inclination would produce significant modifications on the final result of a maxillary impaction and mandible advancement model surgery. Materials and methods: Four groups were used in this study, with ten identical maxillary casts and one mandibular cast mounted on the same semi-adjustable articulator, with the same malocclusion. The occlusal plane of the two control and study groups had an inclination of 13° and 7°, respectively. Preoperative and postoperative measures were performed using the Erickson platform and impactions of 6 and 10 mm were tested. To control these movements during model surgery, two splints were fabricated using another two maxillary and mandibular casts mounted with occlusal plane of 13°, simulating the proposed movement. Results: The results were compared using the t test. Only the antero-posterior movement of the upper incisor was statistically significant for both study groups (p < 0.05), with a mean of 0.48 and 0.94 mm in the 10 and 6 mm impaction groups, respectively. Discussion: This information means that if an error in the occlusal plane transference occur, it will not be clinically significant, because differences smaller than 1 mm does not have influence on soft and hard tissue final result. © 2012 Springer-Verlag.172109114Ellis III, E., Tharanon, W., Gambrell, K., Accuracy of face-bow transfer: effect on surgical prediction and postsurgical result (1992) J Oral Maxillofac Surg, 50, pp. 562-567Wolford, L.M., Galiano, A., A simple and accurate method for mounting models in orthognathic surgery (2007) J Oral Maxillofac Surg, 65, pp. 1406-1409Bailey, J.O., Nowlin, T.P., Evaluation of the third point of reference for mounting maxillary casts on the Hanau articulator (1984) J Prosthet Dent, 51, pp. 199-201Goska, J.R., Christensen, L.V., Comparison of cast positions by using four face-bows (1988) J Prosthet Dent, 59, pp. 42-44O'Malley, A.M., Milosevic, A., Comparison of three face-bow/semi-adjustable articulator systems for planning orthognathic surgery (2000) Br J Oral Maxillofac Surg, 38, pp. 185-190Gateno, J., Forrest, K.K., Camp, B., A comparison of 3 methods of face-bow transfer recording: implications for orthognathic surgery (2001) J Oral Maxillofac Surg, 59, pp. 635-640Bamber, M.A., Firouzal, R., Harris, M., Linney, A., A comparative study of two arbitrary face-bow transfer systems for orthognathic surgery planning (1996) Int J Oral Maxillofac Surg, 25, pp. 339-343