title: Anatomic Comparison of Contralateral Premolars.
abstract: BACKGROUND
  The comparative anatomy of contralateral premolars has not been previously studied. The purpose of this micro-computed tomography investigation was to qualitatively and quantitatively assess and compare the morphology of contralateral premolars in terms of length, canal width, dentinal thicknesses, accessory canals, root canal configurations, isthmi, C-shapes, root canal orifices, and apical foramina. The null hypothesis (H0) is that contralateral premolars are more morphologically similar than randomly assigned pairs for simple morphometric measurements (lengths, canal widths, and dentinal thickness).
  
  
  METHODS
  Forty-one intact premolar pairs (n = 82) extracted from 28 patients were scanned with micro-computed tomography and reconstructed. Quantitative comparative assessment of measurements was performed by pairwise statistical analysis of contralateral and random pairs with Student t test and one-sample t test. All measured parameters (lengths, widths, and thicknesses) were normalized by Z score so that they could all be compared on a common scale. A correlation study was also performed. Canal configurations and isthmi were classified according to preexisting classification schemes. The number and location of accessory canals and apical foramina were registered and compared.
  
  
  CONCLUSIONS
  Contralateral premolar pairs demonstrated a high degree of similarity in terms of the linear measurements (lengths, widths, and thicknesses). The apical portion (foramina, C-shapes, and accessory canals) did not demonstrate bilateral symmetry. The comprehensive statistical analysis of the normalized parameters by Z score showed no statistically significant differences between the contralateral premolar pairs. The null hypothesis (H0) was accepted.
authors.affiliation: Department of Biomaterials, Faculty of Dentistry, Institute of Clinical Dentistry, University of Oslo, Oslo, Norway.
authors.forename: Gaute Floer
authors.initials: GF
authors.lastname: Johnsen
authors.affiliation: Department of Biomaterials, Faculty of Dentistry, Institute of Clinical Dentistry, University of Oslo, Oslo, Norway.
authors.forename: Sazan
authors.initials: S
authors.lastname: Dara
authors.affiliation: Department of Biomaterials, Faculty of Dentistry, Institute of Clinical Dentistry, University of Oslo, Oslo, Norway.
authors.forename: Sameenah
authors.initials: S
authors.lastname: Asjad
authors.affiliation: Department of Endodontics, Faculty of Dentistry, Institute of Clinical Dentistry, University of Oslo, Oslo, Norway.
authors.forename: Pia Titterud
authors.initials: PT
authors.lastname: Sunde
authors.affiliation: Department of Biomaterials, Faculty of Dentistry, Institute of Clinical Dentistry, University of Oslo, Oslo, Norway. Electronic address: h.j.haugen@odont.uio.no.
authors.forename: Håvard Jostein
authors.initials: HJ
authors.lastname: Haugen
mesh_terms: D000293:Adolescent; D000328:Adult; D001641:Bicuspid / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D002648:Child; D003786:Dental Pulp Cavity / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D003804:Dentin / Q000033:anatomy & histology; D005260:Female; D006801:Humans; D008297:Male; D019227:Tooth Apex / Q000033:anatomy & histology; D055114:X-Ray Microtomography; D055815:Young Adult
keywords: Anatomical symmetry; contralateral premolars; micro-CT