title: Can cone beam CT predict the hardness of interradicular cortical bone?
abstract: OBJECTIVE
  Orthodontic mini implants can be inserted at the interradicular site. The bone quality at this site may affect the stability and anchorage of the implant. Bone density is clinically evaluated by Hounsfield units (HU) obtained from cone beam CT (CBCT). The objective of this study was to determine the correlations between HU, microhardness and cortical bone thickness of interradicular site at various segments (anterior/posterior) and aspects (buccal/lingual) of both jaws in a swine model.
  
  
  METHODS
  Eight mandible and maxilla swine bones were scanned by CBCT. The HU and thickness of the above-mentioned sites were determined. Then, a Knoop microhardness test was applied and the Knoop Hardness Number was obtained (KHN).
  
  
  RESULTS
  The mandible parameters spread over a wider range than the maxilla. The buccal aspect of the maxilla had higher HU and KHN values than the mandible. The lingual aspect of the mandible had higher KHN values than the maxilla. Posterior segments had higher HU and KHN values. The thickness of the alveolar cortical bone was greater in the maxilla than in the mandible. Correlations were found between HU and KHN for 3 of the 4 sites (anterior or posterior, buccal or lingual) of the mandible only. No correlations were found for the maxilla. Upon pooling the HU and KHN data for the whole jaw, correlation was found for the maxilla as well.
  
  
  CONCLUSIONS
  Relying on HU values as a predictor of cortical bone hardness should be considered with caution.
authors.affiliation: Department of Oral Biology, The Goldschleger School of Dental Medicine, Tel Aviv University, Tel Aviv 69978, Israel. tbrosh@post.tau.ac.il.
authors.forename: Tamar
authors.initials: T
authors.lastname: Brosh
authors.forename: Bereznyak-Elias
authors.initials: BE
authors.lastname: Yekaterina
authors.forename: Raphael
authors.initials: R
authors.lastname: Pilo
authors.forename: Nir
authors.initials: N
authors.lastname: Shpack
authors.forename: Silvia
authors.initials: S
authors.lastname: Geron
mesh_terms: D000818:Animals; D015519:Bone Density; D054893:Cone-Beam Computed Tomography / Q000379:methods*; D008334:Mandible / Q000000981:diagnostic imaging*; D008437:Maxilla / Q000000981:diagnostic imaging*; D013552:Swine
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