title: The nasopalatine canal, a limiting factor for temporary anchorage devices: a cone beam computed tomography data study.
abstract: OBJECTIVE
  There is only little knowledge on topographical predispositions of the nasopalatine canal as a limiting factor for insertion of mid-palatal temporary anchorage devices (TAD). The purpose of the study was to assess the course of the nasopalatine canal, the adjacent vertical bone quantity, and whether it might differ among vertical facial types, using pre-existing cone beam computed tomography (CBCT) scans.
  
  
  METHODS
  Out of a consecutive sample collected from April 2008 to August 2012, only patient data depicting both upper and lower jaw completely were evaluated retrospectively. The linear measurements were taken on the respective midsagittal view perpendicular to the palate at the level of 1st molar/2nd premolar (5/6), 2nd premolar/1st premolar (4/5), and 1st premolar/canine (3/4). Screen-prints were used to measure the inclination of the nasopalatine canal in relation to the maxillary jaw base. Maxillary and mandibular divergence was assessed on rendered lateral cephalograms.
  
  
  RESULTS
  Out of 3869 pre-existing consecutive CBCT scans, data from 398 patients met the inclusion criteria and could be extracted. The mean vertical bone was 4.09 mm at the 5/6 level, 5.22 mm at the 4/5 level, and 3.14 mm at the 3/4 level, respectively. A statistically significant negative correlation exists between jaw divergence and the canal angulation with regard to the maxillary base. A statistically significant negative correlation exists between the canal angulation and vertical bone measurements at the 4/5 and 3/4 levels.
  
  
  CONCLUSIONS
  Vertical bone volume is sufficient at 4/5 level for TAD placement, and bares only a small risk for neuro-sensory impairment. Therefore, only in rare cases a CBCT is justified for palatal implant placement. The course of the nasopalatine canal is negatively correlated with the vertical skeletal facial pattern pointing to the fact that in hypodivergent patients a TAD might be placed in a more distal or paramedian region.
authors.affiliation: Clinic for Orthodontics and Pediatric Dentistry, Center for Dental and Oral Medicine and Cranio-Maxillofacial Surgery, University of Zurich, Switzerland.
authors.forename: Raphael
authors.initials: R
authors.lastname: Tilen
authors.affiliation: Clinic for Orthodontics and Pediatric Dentistry, Center for Dental and Oral Medicine and Cranio-Maxillofacial Surgery, University of Zurich, Switzerland.
authors.forename: Raphael
authors.initials: R
authors.lastname: Patcas
authors.affiliation: Oral and Maxillofacial Radiology, Applied Oral Sciences, Faculty of Dentistry, The University of Hong Kong, Hong Kong SAR, China.
authors.forename: Michael M
authors.initials: MM
authors.lastname: Bornstein
authors.affiliation: Private practice, Traben-Trarbach, Germany.
authors.forename: Björn
authors.initials: B
authors.lastname: Ludwig
authors.affiliation: Clinic for Orthodontics and Pediatric Dentistry, Center for Dental and Oral Medicine and Cranio-Maxillofacial Surgery, University of Zurich, Switzerland.
authors.forename: Marc
authors.initials: M
authors.lastname: Schätzle
mesh_terms: D000328:Adult; D000368:Aged; D002508:Cephalometry / Q000379:methods; D054893:Cone-Beam Computed Tomography / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D008334:Mandible / Q000000981:diagnostic imaging / Q000473:pathology; D008437:Maxilla / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D008875:Middle Aged; D009296:Nasal Cavity / Q000000981:diagnostic imaging / Q000473:pathology*; D052280:Orthodontic Anchorage Procedures / Q000295:instrumentation*; D010159:Palate / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D012189:Retrospective Studies; D055815:Young Adult