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Dental implant changes following incineration
Forensic Science International 207 (2011) 50–54
Contents lists available at ScienceDirect
Forensic Science International journal homepage: www.elsevier.com/locate/forsciint
Dental implant changes following incineration J. Berketa a,*, H. James a, V. Marino b a b
Forensic Odontology Unit, School of Dentistry, University of Adelaide, Adelaide, South Australia 5005, Australia Biomaterials Laboratory, School of Dentistry, University of Adelaide, Adelaide, South Australia 5005, Australia
A R T I C L E I N F O
A B S T R A C T
Article history: Received 7 May 2010 Received in revised form 11 August 2010 Accepted 29 August 2010 Available online 28 September 2010
Non-visual identification of victims utilizes DNA, fingerprint and dental comparison as primary scientific identifiers. In incidents where a victim has been incinerated, there may be loss of fingerprint detail and denaturing of DNA. Although extremely durable, tooth loss will also occur with extreme temperatures and the characteristics of recovered dental implants, if any, may be the only physical identifying data available. Currently, there are no experimental investigations to determine what changes occur to dental implants following high temperature exposure. A selection of dental implants was radiographed, utilizing purpose built apparatus to allow standard methodology. They were then heated in an INFITROLTM kiln to a maximum temperature of 1125 8C and the radiographic procedure repeated. Image subtraction evaluation of the radiographs was recorded using Adobe1 Photoshop1. Both commercially pure titanium and titanium alloy dental implants survived the incineration and there was oxidation of the surface leading to minor alteration of the image. There was, however, no detectable sagging of the implants. The results of this research suggest that dental implants are still recognizable following incineration. In scenarios commonly seen by forensic odontologists, heat will destroy both teeth and conventional dental restorative materials. Implants, however, will resist these conditions and will also retain the features necessary to identify the type of implant. ß 2010 Elsevier Ireland Ltd. All rights reserved.
Keywords: Forensic odontology Identification Incineration Dental implant oxidation Metal sag
1. Introduction Dental antemortem/postmortem comparison by odontologists continues to be the major scientific method for identification in disasters throughout the world [1–3], and radiographic images of dental structures are utilized in image comparison to support odontologists’ conclusions [4,5]. The placement of dental endosseous implants in patients to replace one or more missing teeth is occurring at a rapidly growing rate [6–8], increasing the likelihood that implants will be present in deceased victims and detected in postmortem radiographic examination. As implants are mass produced they lack the individuality of hand crafted restorations, but their physical properties of corrosion resistance and extremely high melting point [9,10] could assist in the identification of victims where there is lack of other scientific evidence such as DNA or fingerprints [11]. In situations of extreme heat, it has been seen that the crown of the tooth detaches from the root, probably due to the anatomy of teeth
* Corresponding author at: Forensic Odontology Unit, School of Dentistry, University of Adelaide, Level 3, 233 North Terrace, Adelaide, South Australia 5005, Australia. Tel.: +61 8 83035431; fax: +61 8 83034385. E-mail address: [email protected] (J. Berketa). 0379-0738/$ – see front matter ß 2010 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.forsciint.2010.08.025
allowing central vapourization of the pulp tissue [5]. Conventional dental filling materials such as amalgam, composite resin and gold may melt or distort [5,12,13]. As commercially pure titanium and titanium alloy dental implants have a melting point greater than 1650 8C [14] the likelihood of implants surviving thermal insult is high, providing some weight of evidence to the identification of victims. Maximum temperatures in human crematoria range around 950–1000 8C [12,15,16]. Currently it has been recorded that temperatures within burning motor vehicles reach 1000 8C [17]. A study in Sweden recorded temperatures in tunnel fires of up to 1365 8C [18]. Although the melting point of titanium metal is much greater than these reported temperatures, metals may sag (creep) at a much lower temperature than their melting point. Sagging in metals occurs when T > 0.3–0.4TM for metals where T is the temperature and TM is the melting temperature in degrees Celsius minus 272.15 [14]. The recognition features of implants include the grooves, holes and threads [19]. It is important to ascertain if the sagging might be of such magnitude that the individual features of the implants will no longer be recognizable radiographically. The exact number of dental implants sold by individual companies remains a trade secret; however Nobel-BiocareTM (Zurich, Switzerland) and StraumannTM (Waldenburg, Switzerland)
[(Fig._1)TD$IG]
J. Berketa et al. / Forensic Science International 207 (2011) 50–54
51
Fig. 1. Radiographic aid constructed from cold cure resin.
remain the most popular supply companies across the world [20]. These companies all utilize commercially pure titanium in their implant construction. 3i BiometTM (London, UK) is a well-known dental implant company that chooses to utilize titanium alloy (Ti– 6Al–4V) to manufacture their dental implants due to the alloy’s increased physical strength [21]. The authors decided to test these types of dental implants following incineration in a temperature controlled kiln. The hypothesis was that radiographs of pre- and post-incineration implants could be reliably compared. 2. Materials and methods Nobel-BiocareTM, StraumannTM and 3i BiometTM companies were approached to donate implants for the study. The implants selected from the donations were StraumannTM Standard Plus 3.3 8 mm, a Nobel-BiocareTM Branemark Mk III Groovy 15 5 mm, a Nobel-BiocareTM All-in-oneTM 13 3 mm and a 3i Biomet Certain 4 8.5 mm. Each implant was irradiated for 0.18 s at 65 kVp 8 mA using a Belmont Searcher model DX-068 (Takara Belmont, Osaka, Japan). The sensor was a MPSe Ethernet digital with Cygnus software (Cygnus Technologies, Scottsdale, USA). To allow standard methodology, a purpose built apparatus made from a cold cure resin (VertexTM Trayplast, Zeist, The Netherlands) was constructed as shown in Fig. 1. To reproduce the rotation of the implant within the positioning aid, each implant was superficially marked on its leading head edge with a high speed diamond bur and this mark was aligned forward to the beam on a marked area on the positioning apparatus. The implants were placed in an INFI-TROLTM (K.H. Huppert, Chicago, USA) kiln designed to heat porcelain restorations. The temperature within the INFI-TROLTM kiln was monitored with a digital thermometer Model N19 – Q1437 (Dick Smith, Chullora, Australia), with a temperature range of 200 to 1370 8C (0.5%) using KType thermocouples. A digital camera (Nikon Coolpix 5900, Tokyo, Japan) was mounted on a tripod in front of the kiln’s door and a photograph was taken of the implants within the kiln at room temperature and at each 100 8C increment and at 1125 8C Following the photograph at 1125 8C, the kiln was switched off and the door of the kiln was left open for the implants to cool slowly. At room temperature the implants were again photographed before removal. In order to standardize the method, the fired implants were then re-irradiated using the same apparatus. The procedure was repeated after one month using a second set of implants. The radiographic images of the implants taken before the firings were compared to the images taken after the firings using computer software, Adobe1 Photoshop1CS2 (Adobe Systems, San Jose, USA). An image subtraction function of the software was used to highlight differences between the images [22]. As there appeared to be colour changes between the pure titanium and alloy type implants further examination of the incinerated samples was conducted using field emission scanning electron microscopy (SEM) and X-ray elemental analysis.
3. Results The differences function in Adobe1 Photoshop1CS2 determines any changes between two images of the same size. If the images are identical the resultant subtraction image is completely black, reflecting the same pixel value. Any pixel discrepancies translate into differences in brightness and appear on the subtraction image as shades of grey. The results of the comparative analysis revealed image differences which we attribute to a slight enlargement of the implants, as seen in Fig. 2. Even though there was a slight discrepancy in size for each implant type, no detectable sagging
was noted and the recognition features of threads and grooves were still identifiable. Following the firing of the implants a distinctive gold coloured crust was visible on the surfaces of the pure titanium implants but not on the alloy type implant (Fig. 3). The SEM images of the implants indicated a distinct layer of crust formed on the surface after incineration, seen in Fig. 4. This crust was brittle and easily removed. The elemental analysis revealed that this crust consisted of titanium oxide on the commercially pure titanium implants at most sites except in the centre area of the implant where aluminum was curiously detected (Fig. 5). On the titanium alloy implant (3i) oxygen, aluminum and titanium were detected but not vanadium (Fig. 6).
4. Discussion The results indicate that there was no sagging visible on the radiographic images of the identification features such as grooves and threads following exposure to 1125 8C. The 1125 8C temperature was selected as it was extremely close to the maximum attainable temperature of the kiln and for occupational health and safety concerns. The temperature however was above the maximum temperatures reached in cremations [12,15,16], burning vehicles [17] and the 9/11 World Trade Center disaster (1093 8C) [23]. The process of oxidation at high temperatures was originally described by Pilling and Bedworth [24]. This oxidation onto the surface of the implants produced a slight increase in size of approximately 0.1 mm. The fragile nature of the crust made accurate measurements difficult to quantify however the small increase in size would need to be considered if a metric analysis was undertaken. As the colour varied between the commercially pure titanium implants and the alloy type this could assist the identification of the implant, although further studies would be required in vivo to study whether bone around the implant would influence the oxidation layer. The fact that the kiln door was repeatedly opened to facilitate photography may also have influenced the amount of surface deposition. As only one alloy type of dental implant was tested, caution should be taken in concluding that the same reaction would occur in all alloy type of dental implants. Ideally, it would be beneficial to have a sample of all dental implants and to observe the changes following severe heat exposure. As there are increasing numbers of dental implant companies this would be extremely difficult and expensive to achieve. The observation that there was some aluminum on the surface of the implant in the middle section only, might be explained by the fact that the same pair of forceps was utilized to remove each implant from the kiln and some residual aluminum transfer may have occurred. A separate pair of forceps should be utilized for each different implant.
[(Fig._2)TD$IG]
52
[(Fig._3)TD$IG]
J. Berketa et al. / Forensic Science International 207 (2011) 50–54
Fig. 3. The StraumannTM, BranemarkTM, All-in-oneTM and the 3iTM implants within the furnace before firing (a) and after firing (b). Note the gold colour change on the StraumannTM, BranemarkTM, All-in-oneTM implants.
Vanadium was not detected in the 3i alloy type implant. The vanadium content is only 4% and as only six sites on the implant were tested, it could be below detectable limits. The rate in which aluminum and titanium oxidize also could be much greater than vanadium, but further studies are required to verify this theory. Further studies utilizing cadaver or animal jaws are required to examine the effects of high temperatures on the physical properties of implants threaded in mandibular or maxillary bone. A broader range of implants may also further verify the findings.
[(Fig._4)TD$IG]
Fig. 2. 3iTM implant (a) pre-incineration, (b) post-incineration and (c) subtraction image. Similar results were observed for each brand of implant.
Fig. 4. StraumannTM implant head with partial crust removal.
[(Fig._5)TD$IG]
J. Berketa et al. / Forensic Science International 207 (2011) 50–54
53
Fig. 5. Elemental analysis of StraumannTM implant crust at the head of the implant (a) showing the presence of oxygen (O) and titanium (Ti) and at the middle thread of the implant (b) showing presence of oxygen (O), aluminum (Al) and titanium (Ti).
[(Fig._6)TD$IG]
Fig. 6. Elemental analysis of the 3iTM alloy implant, indicating oxygen (O), aluminum (Al) and titanium (Ti), but no vanadium (V) present.
54
J. Berketa et al. / Forensic Science International 207 (2011) 50–54
5. Conclusions In some cases undertaken by forensic odontologists extreme heat will destroy both teeth and conventional dental restorative materials, as well as other scientific identifiers. Due to their physical properties, implants will resist thermal insult and will also retain the features such as shape and thread pattern necessary to identify the type of implant. Although all the implants subjected to temperatures up to 1125 8C were confidently recognized only the pure titanium implants showed surface colour changes. Possible increase in physical dimensions due to the formation of the oxide layer must be considered prior to metric analysis. Acknowledgements The authors acknowledge the support of both the Minister for Police in South Australia and South Australian Police. The authors wish to thank the StraumannTM, Nobel-BiocareTM and 3i BiometTM companies for their generous donation of implants. The authors wish to thank Ian Linke from the school of Electrical and Electronic Engineering, University of Adelaide, for the use of the kiln and thermometer. References [1] H. James, Thai tsunami victim identification overview to date, J. Forensic Odontostomatol. 23 (2005) 1–18. [2] A. Valenzuela, S. Martin-de las Heras, T. Marques, N. Exposito, J.M. Bohoyo, The application of dental methods of identification to human burn victims in a mass disaster, Int. J. Legal Med. 113 (2000) 236–239. [3] J.M. Hutt, B. Ludes, B. Kaess, A. Tracqui, P. Mangin, Odontological identification of the victims of flight AI.IT 5148 air disaster Lyon-Strasbourg 20.01.1992, Int. J. Legal Med. 107 (1995) 275–279. [4] B.R. Rothwell, Principles of dental identification, in: Dental Clinics of North America, Saunders, Philadelphia, 2001.
[5] E.E. Herschaft, M.E. Alder, D.K. Ord, R.D. Rawson, E.S. Smith (Eds.), Manual of Forensic Odontology, American Society of Forensic Odontology, 4th ed., Impress, Albany, 2006, pp. 20–48. [6] Business Week No. 94: Straumann Holding, 2005, available at: http://www.businessweek.com/magazine/content/05_43/b3956812.htm (accessed February 21, 2010). [7] M.K. Iqbal, S. Kim, A review of factors influencing treatment planning decisions of single-tooth implants versus preserving natural teeth with nonsurgical endodontic therapy, J. Endod. 34 (2008) 519–529. [8] P. Laine, A. Salo, R. Kontio, S. Ylijoki, C. Lindqvist, R. Suuronen, Failed dental implants—clinical, radiological and bacteriological findings in 17 patients, J. Craniomaxillofac. Surg. 33 (2005) 212–217. [9] R. Van Noort, Titanium: the implant material of today, J. Mater. Sci. 22 (1987) 3801–3811. [10] M.J. Donachie Jr., Titanium: A Technical Guide, 2nd ed., ASM International, Materials Park, 2000, pp. 1–2. [11] India: Official Corruption and Negligence Tied to 34 Deaths in Firecracker Explosion, 2009, available at: http://www.wsws.org/articles/2009/oct2009/ indi-o22.shtml (accessed February 21, 2010) [12] S.I. Fairgrieve, Forensic Cremation: Recovery and Analysis, CRC Press, Boca Raton, 2008, pp. 148–156. [13] G. Merlati, C. Savio, P. Danesino, G. Fassina, P. Menghini, Further study of restored and un-restored teeth subjected to high temperature, J. Forensic Odontostomatol. 22 (2004) 34–39. [14] M.F. Ashby, D.R.H. Jones, Engineering Materials. An Introduction to Their Properties and Applications, 1st ed., Pergamon, Oxford, 1980. [15] The Cremation Process 71, available at: http://hubpages.com/hub/cremation (accessed February 21, 2010). [16] Crematorium Dangers, available at: http://www.ehow.com/list_5932595_crematorium-dangers.html (accessed February 21, 2010). [17] J. Dehaan, Kirk’s Fire Investigation, 5th ed., Brady, New Jersey, 2002. [18] A. Lo¨nnermark, H. Ingason, Gas temperatures in heavy goods vehicle fires in tunnels, Fire Safety J. 40 (2005) 506–527. [19] J.W. Berketa, R.S. Hirsch, D. Higgins, H. James, Radiographic recognition of dental implants as an aid to identifying the deceased, J. Forensic Sci. 55 (2010) 66–70. [20] Straumann’s Sales Outlook Remains Solid, available at: http://www.osseonews.com/straumanns-north-america-sales-remain-solid/ (accessed February 21, 2010). [21] Cast Nonferrous: Titanium and Titanium Alloys, available at: http://www.keytometals.com/Article20.htm (accessed February 21, 2010). [22] Aligning Images in Photoshop, available at: http://www.astropix.com/HTML/ J_DIGIT/PSALIGN.HTM (accessed April 11, 2010). [23] Context of ‘‘September 16–23, 2001: Images of Ground Zero Show Thermal Hot Spots’’, available at: http://www.historycommons.org/context.jsp?item=a091601hotspots (accessed June 30, 2010). [24] N.B. Pilling, R.E. Bedworth, The oxidation of metals at high temperatures, J. Inst. Met. 29 (1923) 529–591.
Contents lists available at ScienceDirect
Forensic Science International journal homepage: www.elsevier.com/locate/forsciint
Dental implant changes following incineration J. Berketa a,*, H. James a, V. Marino b a b
Forensic Odontology Unit, School of Dentistry, University of Adelaide, Adelaide, South Australia 5005, Australia Biomaterials Laboratory, School of Dentistry, University of Adelaide, Adelaide, South Australia 5005, Australia
A R T I C L E I N F O
A B S T R A C T
Article history: Received 7 May 2010 Received in revised form 11 August 2010 Accepted 29 August 2010 Available online 28 September 2010
Non-visual identification of victims utilizes DNA, fingerprint and dental comparison as primary scientific identifiers. In incidents where a victim has been incinerated, there may be loss of fingerprint detail and denaturing of DNA. Although extremely durable, tooth loss will also occur with extreme temperatures and the characteristics of recovered dental implants, if any, may be the only physical identifying data available. Currently, there are no experimental investigations to determine what changes occur to dental implants following high temperature exposure. A selection of dental implants was radiographed, utilizing purpose built apparatus to allow standard methodology. They were then heated in an INFITROLTM kiln to a maximum temperature of 1125 8C and the radiographic procedure repeated. Image subtraction evaluation of the radiographs was recorded using Adobe1 Photoshop1. Both commercially pure titanium and titanium alloy dental implants survived the incineration and there was oxidation of the surface leading to minor alteration of the image. There was, however, no detectable sagging of the implants. The results of this research suggest that dental implants are still recognizable following incineration. In scenarios commonly seen by forensic odontologists, heat will destroy both teeth and conventional dental restorative materials. Implants, however, will resist these conditions and will also retain the features necessary to identify the type of implant. ß 2010 Elsevier Ireland Ltd. All rights reserved.
Keywords: Forensic odontology Identification Incineration Dental implant oxidation Metal sag
1. Introduction Dental antemortem/postmortem comparison by odontologists continues to be the major scientific method for identification in disasters throughout the world [1–3], and radiographic images of dental structures are utilized in image comparison to support odontologists’ conclusions [4,5]. The placement of dental endosseous implants in patients to replace one or more missing teeth is occurring at a rapidly growing rate [6–8], increasing the likelihood that implants will be present in deceased victims and detected in postmortem radiographic examination. As implants are mass produced they lack the individuality of hand crafted restorations, but their physical properties of corrosion resistance and extremely high melting point [9,10] could assist in the identification of victims where there is lack of other scientific evidence such as DNA or fingerprints [11]. In situations of extreme heat, it has been seen that the crown of the tooth detaches from the root, probably due to the anatomy of teeth
* Corresponding author at: Forensic Odontology Unit, School of Dentistry, University of Adelaide, Level 3, 233 North Terrace, Adelaide, South Australia 5005, Australia. Tel.: +61 8 83035431; fax: +61 8 83034385. E-mail address: [email protected] (J. Berketa). 0379-0738/$ – see front matter ß 2010 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.forsciint.2010.08.025
allowing central vapourization of the pulp tissue [5]. Conventional dental filling materials such as amalgam, composite resin and gold may melt or distort [5,12,13]. As commercially pure titanium and titanium alloy dental implants have a melting point greater than 1650 8C [14] the likelihood of implants surviving thermal insult is high, providing some weight of evidence to the identification of victims. Maximum temperatures in human crematoria range around 950–1000 8C [12,15,16]. Currently it has been recorded that temperatures within burning motor vehicles reach 1000 8C [17]. A study in Sweden recorded temperatures in tunnel fires of up to 1365 8C [18]. Although the melting point of titanium metal is much greater than these reported temperatures, metals may sag (creep) at a much lower temperature than their melting point. Sagging in metals occurs when T > 0.3–0.4TM for metals where T is the temperature and TM is the melting temperature in degrees Celsius minus 272.15 [14]. The recognition features of implants include the grooves, holes and threads [19]. It is important to ascertain if the sagging might be of such magnitude that the individual features of the implants will no longer be recognizable radiographically. The exact number of dental implants sold by individual companies remains a trade secret; however Nobel-BiocareTM (Zurich, Switzerland) and StraumannTM (Waldenburg, Switzerland)
[(Fig._1)TD$IG]
J. Berketa et al. / Forensic Science International 207 (2011) 50–54
51
Fig. 1. Radiographic aid constructed from cold cure resin.
remain the most popular supply companies across the world [20]. These companies all utilize commercially pure titanium in their implant construction. 3i BiometTM (London, UK) is a well-known dental implant company that chooses to utilize titanium alloy (Ti– 6Al–4V) to manufacture their dental implants due to the alloy’s increased physical strength [21]. The authors decided to test these types of dental implants following incineration in a temperature controlled kiln. The hypothesis was that radiographs of pre- and post-incineration implants could be reliably compared. 2. Materials and methods Nobel-BiocareTM, StraumannTM and 3i BiometTM companies were approached to donate implants for the study. The implants selected from the donations were StraumannTM Standard Plus 3.3 8 mm, a Nobel-BiocareTM Branemark Mk III Groovy 15 5 mm, a Nobel-BiocareTM All-in-oneTM 13 3 mm and a 3i Biomet Certain 4 8.5 mm. Each implant was irradiated for 0.18 s at 65 kVp 8 mA using a Belmont Searcher model DX-068 (Takara Belmont, Osaka, Japan). The sensor was a MPSe Ethernet digital with Cygnus software (Cygnus Technologies, Scottsdale, USA). To allow standard methodology, a purpose built apparatus made from a cold cure resin (VertexTM Trayplast, Zeist, The Netherlands) was constructed as shown in Fig. 1. To reproduce the rotation of the implant within the positioning aid, each implant was superficially marked on its leading head edge with a high speed diamond bur and this mark was aligned forward to the beam on a marked area on the positioning apparatus. The implants were placed in an INFI-TROLTM (K.H. Huppert, Chicago, USA) kiln designed to heat porcelain restorations. The temperature within the INFI-TROLTM kiln was monitored with a digital thermometer Model N19 – Q1437 (Dick Smith, Chullora, Australia), with a temperature range of 200 to 1370 8C (0.5%) using KType thermocouples. A digital camera (Nikon Coolpix 5900, Tokyo, Japan) was mounted on a tripod in front of the kiln’s door and a photograph was taken of the implants within the kiln at room temperature and at each 100 8C increment and at 1125 8C Following the photograph at 1125 8C, the kiln was switched off and the door of the kiln was left open for the implants to cool slowly. At room temperature the implants were again photographed before removal. In order to standardize the method, the fired implants were then re-irradiated using the same apparatus. The procedure was repeated after one month using a second set of implants. The radiographic images of the implants taken before the firings were compared to the images taken after the firings using computer software, Adobe1 Photoshop1CS2 (Adobe Systems, San Jose, USA). An image subtraction function of the software was used to highlight differences between the images [22]. As there appeared to be colour changes between the pure titanium and alloy type implants further examination of the incinerated samples was conducted using field emission scanning electron microscopy (SEM) and X-ray elemental analysis.
3. Results The differences function in Adobe1 Photoshop1CS2 determines any changes between two images of the same size. If the images are identical the resultant subtraction image is completely black, reflecting the same pixel value. Any pixel discrepancies translate into differences in brightness and appear on the subtraction image as shades of grey. The results of the comparative analysis revealed image differences which we attribute to a slight enlargement of the implants, as seen in Fig. 2. Even though there was a slight discrepancy in size for each implant type, no detectable sagging
was noted and the recognition features of threads and grooves were still identifiable. Following the firing of the implants a distinctive gold coloured crust was visible on the surfaces of the pure titanium implants but not on the alloy type implant (Fig. 3). The SEM images of the implants indicated a distinct layer of crust formed on the surface after incineration, seen in Fig. 4. This crust was brittle and easily removed. The elemental analysis revealed that this crust consisted of titanium oxide on the commercially pure titanium implants at most sites except in the centre area of the implant where aluminum was curiously detected (Fig. 5). On the titanium alloy implant (3i) oxygen, aluminum and titanium were detected but not vanadium (Fig. 6).
4. Discussion The results indicate that there was no sagging visible on the radiographic images of the identification features such as grooves and threads following exposure to 1125 8C. The 1125 8C temperature was selected as it was extremely close to the maximum attainable temperature of the kiln and for occupational health and safety concerns. The temperature however was above the maximum temperatures reached in cremations [12,15,16], burning vehicles [17] and the 9/11 World Trade Center disaster (1093 8C) [23]. The process of oxidation at high temperatures was originally described by Pilling and Bedworth [24]. This oxidation onto the surface of the implants produced a slight increase in size of approximately 0.1 mm. The fragile nature of the crust made accurate measurements difficult to quantify however the small increase in size would need to be considered if a metric analysis was undertaken. As the colour varied between the commercially pure titanium implants and the alloy type this could assist the identification of the implant, although further studies would be required in vivo to study whether bone around the implant would influence the oxidation layer. The fact that the kiln door was repeatedly opened to facilitate photography may also have influenced the amount of surface deposition. As only one alloy type of dental implant was tested, caution should be taken in concluding that the same reaction would occur in all alloy type of dental implants. Ideally, it would be beneficial to have a sample of all dental implants and to observe the changes following severe heat exposure. As there are increasing numbers of dental implant companies this would be extremely difficult and expensive to achieve. The observation that there was some aluminum on the surface of the implant in the middle section only, might be explained by the fact that the same pair of forceps was utilized to remove each implant from the kiln and some residual aluminum transfer may have occurred. A separate pair of forceps should be utilized for each different implant.
[(Fig._2)TD$IG]
52
[(Fig._3)TD$IG]
J. Berketa et al. / Forensic Science International 207 (2011) 50–54
Fig. 3. The StraumannTM, BranemarkTM, All-in-oneTM and the 3iTM implants within the furnace before firing (a) and after firing (b). Note the gold colour change on the StraumannTM, BranemarkTM, All-in-oneTM implants.
Vanadium was not detected in the 3i alloy type implant. The vanadium content is only 4% and as only six sites on the implant were tested, it could be below detectable limits. The rate in which aluminum and titanium oxidize also could be much greater than vanadium, but further studies are required to verify this theory. Further studies utilizing cadaver or animal jaws are required to examine the effects of high temperatures on the physical properties of implants threaded in mandibular or maxillary bone. A broader range of implants may also further verify the findings.
[(Fig._4)TD$IG]
Fig. 2. 3iTM implant (a) pre-incineration, (b) post-incineration and (c) subtraction image. Similar results were observed for each brand of implant.
Fig. 4. StraumannTM implant head with partial crust removal.
[(Fig._5)TD$IG]
J. Berketa et al. / Forensic Science International 207 (2011) 50–54
53
Fig. 5. Elemental analysis of StraumannTM implant crust at the head of the implant (a) showing the presence of oxygen (O) and titanium (Ti) and at the middle thread of the implant (b) showing presence of oxygen (O), aluminum (Al) and titanium (Ti).
[(Fig._6)TD$IG]
Fig. 6. Elemental analysis of the 3iTM alloy implant, indicating oxygen (O), aluminum (Al) and titanium (Ti), but no vanadium (V) present.
54
J. Berketa et al. / Forensic Science International 207 (2011) 50–54
5. Conclusions In some cases undertaken by forensic odontologists extreme heat will destroy both teeth and conventional dental restorative materials, as well as other scientific identifiers. Due to their physical properties, implants will resist thermal insult and will also retain the features such as shape and thread pattern necessary to identify the type of implant. Although all the implants subjected to temperatures up to 1125 8C were confidently recognized only the pure titanium implants showed surface colour changes. Possible increase in physical dimensions due to the formation of the oxide layer must be considered prior to metric analysis. Acknowledgements The authors acknowledge the support of both the Minister for Police in South Australia and South Australian Police. The authors wish to thank the StraumannTM, Nobel-BiocareTM and 3i BiometTM companies for their generous donation of implants. The authors wish to thank Ian Linke from the school of Electrical and Electronic Engineering, University of Adelaide, for the use of the kiln and thermometer. References [1] H. James, Thai tsunami victim identification overview to date, J. Forensic Odontostomatol. 23 (2005) 1–18. [2] A. Valenzuela, S. Martin-de las Heras, T. Marques, N. Exposito, J.M. Bohoyo, The application of dental methods of identification to human burn victims in a mass disaster, Int. J. Legal Med. 113 (2000) 236–239. [3] J.M. Hutt, B. Ludes, B. Kaess, A. Tracqui, P. Mangin, Odontological identification of the victims of flight AI.IT 5148 air disaster Lyon-Strasbourg 20.01.1992, Int. J. Legal Med. 107 (1995) 275–279. [4] B.R. Rothwell, Principles of dental identification, in: Dental Clinics of North America, Saunders, Philadelphia, 2001.
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