title: Volumetric analysis of chin and mandibular retromolar region as donor sites for cortico-cancellous bone blocks.
abstract: OBJECTIVE
  To test whether the mandibular retromolar region renders different results from the chin region with respect to the amount of bone available for the harvesting of block grafts.
  
  
  METHODS
  Sixty cone beam computed tomography (CBCT) scans of mandibles of adult patients without pathologic findings in the chin and retromolar region were included. According to the number of mandibular teeth, 20 CBCT data sets were allocated to each of the following groups: group M1: dentition 36-46; group M2: dentition 37-47; and group M3: dentition 38-48. For the potential donor sites in the chin and the retromolar regions, the volume (VChin , VRetro ), the length (LChin , LRetro ), the height (HChin , HRetro ) and the width (HChin , HRetro ) were assessed using a computer software. Moreover, the chin was examined for the presence and the localization of the mandibular incisive canal. To compare the donor sites in the chin and in the retromolar regions, the quotients VRetro /VChin , LRetro /LChin , HRetro /HChin and WRetro /WChin were calculated and tested using the Wilcoxon signed-rank test or the sign test.
  
  
  RESULTS
  The mean bone volume VChin measured 3.5 ± 1.3 cm(3) (SD), whereas the overall VRetro amounted to 1.8 ± 1.1 cm(3) (SD). VRetro amounted to 2.6 ± 1.4 cm(3) (SD) in the group M1, 1.8 ± 0.5 cm(3) in the group M2 and 1.0 ± 0.4 cm(3) in the group M3. For the group M1, VRetro /VChin measured 82 ± 39% (P = 0.036). VRetro /VChin reached 57 ± 20% in the group M2 and 32 ± 12% in the group M3 (P < 0.001). The mandibular incisive canal was detected in 97% of the CBCT scans. The distance between the mandibular incisive canal and the apices of the central incisors measured 10.5 ± 3.5 mm.
  
  
  CONCLUSIONS
  The amount of bone available for the harvesting of cortico-cancellous blocks in the chin region was superior in comparison with the mandibular retromolar region. In the absence of the second and the third molars, the amount of bone harvestable in the retromolar region reached approximately 80% of the bone volume available in the chin region. In the majority of the cases, the mandibular incisive canal was detected within the donor site in the chin region.
authors.affiliation: Clinic of Fixed and Removable Prosthodontics and Dental Material Science, Center of Dental Medicine, University of Zurich, Zurich, Switzerland.
authors.forename: Marco
authors.initials: M
authors.lastname: Zeltner
authors.affiliation: Clinic of Fixed and Removable Prosthodontics and Dental Material Science, Center of Dental Medicine, University of Zurich, Zurich, Switzerland.
authors.forename: Laura B
authors.initials: LB
authors.lastname: Flückiger
authors.affiliation: Clinic of Fixed and Removable Prosthodontics and Dental Material Science, Center of Dental Medicine, University of Zurich, Zurich, Switzerland.
authors.forename: Christoph H F
authors.initials: CH
authors.lastname: Hämmerle
authors.affiliation: Institute of Mathematical Statistics and Actuarial Science, University of Bern, Bern, Switzerland.
authors.forename: Jürg
authors.initials: J
authors.lastname: Hüsler
authors.affiliation: Clinic of Fixed and Removable Prosthodontics and Dental Material Science, Center of Dental Medicine, University of Zurich, Zurich, Switzerland.
authors.forename: Goran I
authors.initials: GI
authors.lastname: Benic
mesh_terms: D000071556:Cancellous Bone / Q000637:transplantation; D002680:Chin; D054893:Cone-Beam Computed Tomography; D000071538:Cortical Bone / Q000637:transplantation; D003758:Dental Implantation, Endosseous / Q000379:methods; D006801:Humans; D008334:Mandible / Q000000981:diagnostic imaging*; D008875:Middle Aged; D008963:Molar; D020858:Tissue and Organ Harvesting
keywords: block; bone; bone augmentation; chin; cone beam computed tomography; donor site; graft; radiology; ramus; retromolar; symphysis; volume