title: Volume analysis of heat-induced cracks in human molars: A preliminary study.
abstract: BACKGROUND
  Only a few methods have been published dealing with the visualization of heat-induced cracks inside bones and teeth.
  
  
  OBJECTIVE
  As a novel approach this study used nondestructive X-ray microtomography (micro-CT) for volume analysis of heat-induced cracks to observe the reaction of human molars to various levels of thermal stress.
  
  
  METHODS
  Eighteen clinically extracted third molars were rehydrated and burned under controlled temperatures (400, 650, and 800°C) using an electric furnace adjusted with a 25°C increase/min. The subsequent high-resolution scans (voxel-size 17.7 μm) were made with a compact micro-CT scanner (SkyScan 1174). In total, 14 scans were automatically segmented with Definiens XD Developer 1.2 and three-dimensional (3D) models were computed with Visage Imaging Amira 5.2.2. The results of the automated segmentation were analyzed with an analysis of variance (ANOVA) and uncorrected post hoc least significant difference (LSD) tests using Statistical Package for Social Sciences (SPSS) 17. A probability level of P < 0.05 was used as an index of statistical significance.
  
  
  RESULTS
  A temperature-dependent increase of heat-induced cracks was observed between the three temperature groups (P < 0.05, ANOVA post hoc LSD). In addition, the distributions and shape of the heat-induced changes could be classified using the computed 3D models.
  
  
  CONCLUSIONS
  The macroscopic heat-induced changes observed in this preliminary study correspond with previous observations of unrestored human teeth, yet the current observations also take into account the entire microscopic 3D expansions of heat-induced cracks within the dental hard tissues. Using the same experimental conditions proposed in the literature, this study confirms previous results, adds new observations, and offers new perspectives in the investigation of forensic evidence.
authors.affiliation: Department of Anthropology, University of Vienna, Althanstrasse, 1090 Vienna, Austria ; School of Dentistry, University of Birmingham, St. Chads Queensway, Birmingham B4 6NN, United Kingdom.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Sandholzer
authors.affiliation: Department of Anthropology, University of Vienna, Althanstrasse, 1090 Vienna, Austria ; Faculty of Science, FNWI, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Katharina
authors.initials: K
authors.lastname: Baron
authors.affiliation: Department of Oral Surgery, Medical University of Vienna, Sensengasse, Austria.
authors.forename: Patrick
authors.initials: P
authors.lastname: Heimel
authors.affiliation: Department of Theoretical Biology, University of Vienna, Althanstrasse, 1090 Vienna, Austria.
authors.forename: Brian D
authors.initials: BD
authors.lastname: Metscher
keywords: Fire victims; X-ray microtomography; forensic odontology; forensic science; heat-induced changes