Predictability of maxillary surgery: a comparison of internal and external reference marks.

Internal reference lines have traditionally been used to correlate model work with maxillary surgery. An external point of reference has been suggested for more accurate positioning of the maxilla during surgery. This study compared the predictability of two groups of patients undergoing Le Fort I maxillary osteotomies with either internal reference lines or an external reference point. In the group in which an external reference point was employed, the position of the maxillary central incisor was more accurately predicted on both the x and y coordinates (p less than 0.01) than in the group in which internal reference lines were placed.