The reproducibility of the head position for a laser scan using a novel morphometric analysis for orthognathic surgery.

The aim of this study was to evaluate the reproducibility of the head position for a three-dimensional soft tissue laser scan (lasergraph) using thin-plate splines, for orthognathic surgery planning and follow-up. 60 laser scans of five subjects (12 scans per subject) were obtained at specified intervals. The head was positioned in the lateral view using a spirit level, an engineering device for setting horizontal surfaces, to adjust the Frankfort horizontal plane parallel to the ground. The projection of a narrow beam of longitudinal laser light was used to adjust the axial plane for the frontal view. These scanned images (lasergraphs) were digitised and the co-ordinates of the landmarks recorded. The digitised laser scans were compared using thin-plate splines analysis. The mean difference between the scans due to variations in head position was 0.0135 +/- 0.0109 g x cm2/ sec2 in the lateral view and 0.0090 +/- 0.0054 g x cm2/sec2 in the frontal view. This represents an overall distortion error of less than 2% when following up the surgical change of a typical bimaxillary osteotomy case with 6 mm maxillary advancement and 3 mm mandibular set-back. It is concluded that facial laser scans (lasergraphs) with the Frankfort horizontal plane set using a head rest and spirit level, and the axial plane set using projection of a vertical laser light on the facial midline, are highly reproducible.

The optical surface scan as an alternative to the cephalograph for soft tissue analysis for orthognathic surgery.

The aim of this study was to compare cephalographs and optical surface scanner images (lasergraphs) by measuring the lipincisor relationship, the nasolabial angle, nasal tip projection, the nasofacial angle, the nasomental angle, and the labiomental angle in pre- and postoperative orthognathic surgery patients. The results showed that the methods were comparable, but the optical surface scan (lasergraph) could be used to greater advantage for pre- and postoperative assessment of soft tissue changes with orthognathic surgery, because of its clarity and 3-dimensional potential.