title: Investigation of dental alginate and agar impression materials as a brain simulant for ballistic testing.
abstract: Routine forensic research into in vitro skin/skull/brain ballistic blood backspatter behavior has traditionally used gelatin at a 1:10 Water:Powder (W:P) ratio by volume as a brain simulant. A limitation of gelatin is its high elasticity compared to brain tissue. Therefore this study investigated the use of dental alginate and agar impression materials as a brain simulant for ballistic testing. Fresh deer brain, alginate (W:P ratio 91.5:8.5) and agar (W:P ratio 81:19) specimens (n=10) (11×22×33mm) were placed in transparent Perspex boxes of the same internal dimensions prior to shooting with a 0.22inch caliber high velocity air gun. Quantitative analysis to establish kinetic energy loss, vertical displacement elastic behavior and qualitative analysis to establish elasticity behavior was done via high-speed camera footage (SA5, Photron, Japan) using Photron Fastcam Viewer software (Version 3.5.1, Photron, Japan) and visual observation. Damage mechanisms and behavior were qualitatively established by observation of the materials during and after shooting. The qualitative analysis found that of the two simulant materials tested, agar behaved more like brain in terms of damage and showed similar mechanical response to brain during the passage of the projectile, in terms of energy absorption and vertical velocity displacement. In conclusion agar showed a mechanical and subsequent damage response that was similar to brain compared to alginate.
authors.affiliation: Sir John Walsh Research Institute, Faculty of Dentistry, University of Otago, PO Box 647, Dunedin 9054, New Zealand.
authors.forename: Lisa
authors.initials: L
authors.lastname: Falland-Cheung
authors.affiliation: Sir John Walsh Research Institute, Faculty of Dentistry, University of Otago, PO Box 647, Dunedin 9054, New Zealand.
authors.forename: Neil
authors.initials: N
authors.lastname: Piccione
authors.affiliation: Sir John Walsh Research Institute, Faculty of Dentistry, University of Otago, PO Box 647, Dunedin 9054, New Zealand.
authors.forename: Tianqi
authors.initials: T
authors.lastname: Zhao
authors.affiliation: Department of Mechanical Engineering, University of Canterbury, Private Bag 4800, Christchurch 8041, New Zealand.
authors.forename: Milad Soltanipour
authors.initials: MS
authors.lastname: Lazarjan
authors.affiliation: Sir John Walsh Research Institute, Faculty of Dentistry, University of Otago, PO Box 647, Dunedin 9054, New Zealand.
authors.forename: Suzanne
authors.initials: S
authors.lastname: Hanlin
authors.affiliation: Department of Mechanical Engineering, University of Canterbury, Private Bag 4800, Christchurch 8041, New Zealand.
authors.forename: Mark
authors.initials: M
authors.lastname: Jermy
authors.affiliation: Sir John Walsh Research Institute, Faculty of Dentistry, University of Otago, PO Box 647, Dunedin 9054, New Zealand. Electronic address: neil.waddell@otago.ac.nz.
authors.forename: J Neil
authors.initials: JN
authors.lastname: Waddell
mesh_terms: D000362:Agar; D000464:Alginates; D000818:Animals; D001921:Brain; D003670:Deer; D003760:Dental Impression Materials; D044709:Forensic Ballistics; D020723:Glucuronic Acid; D020197:Head Injuries, Penetrating; D006603:Hexuronic Acids; D006801:Humans; D007700:Kinetics; D008422:Materials Testing; D008954:Models, Biological; D014948:Wounds, Gunshot
chemical_list: D000464:Alginates; D003760:Dental Impression Materials; D006603:Hexuronic Acids; D020723:Glucuronic Acid; D000362:Agar
keywords: Blood back spatter; Brain simulant; Forensics; Wound ballistics