title: The reproducibility of the head position for a laser scan using a novel morphometric analysis for orthognathic surgery.
abstract: 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.
authors.affiliation: Department of Oral and Maxillofacial Surgery, Eastman Dental Institute, University College London Hospitals, University of London, UK.
authors.forename: M
authors.initials: M
authors.lastname: Soncul
authors.forename: M A
authors.initials: MA
authors.lastname: Bamber
mesh_terms: D002508:Cephalometry / Q000295:instrumentation* / Q000379:methods; D003196:Computer Graphics; D003766:Dental Occlusion; D005145:Face / Q000033:anatomy & histology; D005260:Female; D006257:Head / Q000502:physiology; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007834:Lasers; D008297:Male; D056948:Orthognathic Surgical Procedures; D010347:Patient Care Planning; D011187:Posture; D015203:Reproducibility of Results