title: The novel use of three-dimensional surface models to quantify and visualise the immediate changes of the mid-facial skeleton following rapid maxillary expansion.
abstract: BACKGROUND
  The transverse skeletal effects of rapid maxillary expansion (RME) have previously been assessed using cone-beam CT (CBCT). However, to date the majority of studies assess the changes based on two-dimensional slice images, which under utilises the three-dimensional (3D) data captured. This study optimizes the volumetric CBCT data by generating 3D rendered surface models to quantity and visualize the immediate 3D changes of the mid-facial bone surfaces following RME.
  
  
  METHODS
  The sample consisted of 14 patients who required RME prior to fixed appliances. Pre-treatment (T0) and immediate post expansion (T1) CBCT images were taken. Following superimposition the mid face was divided into six anatomical regions. A one-sample t-test was used to determine if the differences between the two surfaces were significantly ≥0.5 mm.
  
  
  RESULTS
  All regions showed a change following RME ≥ 0.5 mm. The maxillary and nasal bones showed 2.3 mm and 2.4 mm expansion respectively, followed by the zygomatic bones (1.4 mm), 2 cases showing asymmetric expansion.
  
  
  CONCLUSIONS
  The use of 3D surface rendered models allows quantification and visualisation of 3D changes in the mid-facial skeleton at anatomical sites distant of RME activation. Following activation there can be a pan mid-facial expansion, including not only the maxilla but also the nasal lateral bones and zygomas. The response was highly variable and asymmetric expansion can occur.
authors: Dental School, School of Medicine, College of Medical, Veterinary and Life Sciences, University of Glasgow, UK.
authors: S C
authors: SC
authors: Ong
authors: Dental School, School of Medicine, College of Medical, Veterinary and Life Sciences, University of Glasgow, UK. Electronic address: bkhambay@hku.hk.
authors: B S
authors: BS
authors: Khambay
authors: Dental School, School of Medicine, College of Medical, Veterinary and Life Sciences, University of Glasgow, UK.
authors: J P
authors: JP
authors: McDonald
authors: Dental School, School of Medicine, College of Medical, Veterinary and Life Sciences, University of Glasgow, UK.
authors: D L
authors: DL
authors: Cross
authors: Dental School, School of Medicine, College of Medical, Veterinary and Life Sciences, University of Glasgow, UK.
authors: L M
authors: LM
authors: Brocklebank
authors: Dental School, School of Medicine, College of Medical, Veterinary and Life Sciences, University of Glasgow, UK.
authors: X
authors: X
authors: Ju
mesh_terms: D000293:Adolescent; D002648:Child; D003198:Computer Simulation; D054893:Cone-Beam Computed Tomography; D005147:Facial Bones / Q000000981:diagnostic imaging* / Q000601:surgery*; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D008297:Male; D008437:Maxilla / Q000000981:diagnostic imaging / Q000601:surgery; D009295:Nasal Bone / Q000000981:diagnostic imaging / Q000601:surgery; D010155:Palatal Expansion Technique; D015050:Zygoma / Q000000981:diagnostic imaging / Q000601:surgery
keywords: 3D; Cone beam CT; Expansion; Rapid; Rendered surface