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 Table of Contents  
FORENSIC ODONTOLOGY: REVIEW ARTICLE
Year : 2020  |  Volume : 32  |  Issue : 2  |  Page : 172-177

Delve into the third dimension: Pertinence of 3D printing in forensic odontology


1 Department of Oral Medicine and Radiology, MNR Dental College and Hospital, Sangareddy, Telangana, India
2 Department of Oral Medicine and Radiology, SVS Institute of Dental Sciences, Mahabubnagar, Telangana, India

Date of Submission23-Mar-2020
Date of Decision22-Apr-2020
Date of Acceptance05-May-2020
Date of Web Publication27-Jun-2020

Correspondence Address:
Dr. Tejaswi Katne
Department of Oral Medicine and Radiology, SVS Institute of Dental Sciences, Mahabubnagar, Telangana - 509 002
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jiaomr.jiaomr_48_20

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   Abstract 


Three-dimensional (3D) printing is the forerunner in today's digital dentistry. It has revolutionized the field of healthcare and is making critical in roads today in forensics, driven primarily by its superior customization propensity. Application of this technique allows presentation of any evidence of human origin without any bias, with minimal degradation thereby reducing subjective errors. 3D printing has several applications, and this article is an attempt to enhance the knowledge of the forensic expert and to give an insight on its possible applications in forensic odontology.

Keywords: 3D printing and three dimensional, additive manufacturing, bite mark analysis, forensic odontology, rapid prototyping


How to cite this article:
Kanaparthi A, Katne T, Gantala R, Gotoor S. Delve into the third dimension: Pertinence of 3D printing in forensic odontology. J Indian Acad Oral Med Radiol 2020;32:172-7

How to cite this URL:
Kanaparthi A, Katne T, Gantala R, Gotoor S. Delve into the third dimension: Pertinence of 3D printing in forensic odontology. J Indian Acad Oral Med Radiol [serial online] 2020 [cited 2020 Jul 7];32:172-7. Available from: http://www.jiaomr.in/text.asp?2020/32/2/172/288138




   Introduction Top


Three-dimensional (3D) printing refers to the manufacturing technologies that create physical models from digital information. The term “3D printing” was coined by Prof. Ely Sachs, in 1995 while working on his project to modify an inkjet printer.[1] 3D printing is also known as additive manufacturing as this process forms the object by adding multiple layers. Synonymously, it is also known as rapid prototyping as the word “prototype” means the “First product.” 3D printing technology was introduced by the engineers with intent to create models of their designs that are quick and efficient.[2] Subsequently, its role in health care has revolutionized the field of medicine and this new technology of fabrication of the objects has embraced the field of maxillofacial dentistry in the past few years and has opened new doors of innovation and research. It is used to create study models for surgery and orthodontics, surgical stents, fabrication of copings, and metal prosthetic frameworks. This technology can create patient-specific craniofacial casts, in the physical form that may be retrieved and analyzed at any point of time.[1],[3]

Forensic odontology is a branch of forensics that deals with the identification of the suspect using the evidences that may be derived from the teeth and associated parts of the oral cavity. This seemingly attractive technology may allow forensic experts to create more robust forensic evidence for their use in courts and medico-legal cases.[3],[4]

3D printing enables creation of accurate physical models that may minimize the previously encountered errors during forensic analysis.[4] The major application of 3D printing in forensic odontology includes bite mark analysis, 3D facial reconstruction, dental age estimation, and gender determination [Figure 1]. This review is an attempt to highlight the importance of 3D printing in forensic odontology and to outline its possible applications.
Figure 1: Scope of 3D printing in forensic odontology

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Three-dimensional (3D) printing was first introduced by Charles Hull in 1983. In 1986 he created the first 3D printer, which used the technique called as “stereolithography.”[2] The main principle behind this process is producing three dimensional solid objects from a digital file format by a three dimensional printer by binding, sintering, or photo polymerizing materials. The three dimensional computer-assisted model (CAD) is sliced into many thin layers, and the manufacturing equipment uses this geometric data to build each layer sequentially until a complete three dimensional physical model is produced.[2],[3]

The basic working procedure of printing a three dimensional model is described in the flowchart [Figure 2].
Figure 2: Flowchart of basic 3D printing protocol

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The third step is the actual printing process wherein the material to be used for printing is chosen according to the requirement. Materials for common dental applications include plastics polymers, ceramics, resins, and metals.[3],[4] Most of these materials allow excellent finishing, to optimally achieve final model with a high degree of precision [Figure 3]. However, certain newer materials are still under development. According to the material chosen, the printing methods are finalized.
Figure 3: a) Three dimensional printer b) Printing in process c) Finished model post processing

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The basic difference in each of the technologies is the process of curing the material and the material used for 3D printing.[2],[5]

Selective laser sintering and electronic beam melting, sinter powder in a heated chamber to a point below its melting point, after which a scanning laser builds the object. Selective laser sintering can be used to print objects from polymers such as alumide, polyamide, glass-particle filled polyamide, rubber-like polyurethane, and metals (titanium, aluminum and stainless steel).[2],[5]

Stereolithography, photopolymer jetting, and digital light processing use photo polymerization, i.e., ceramic filled resins. The source of photo polymerization is the key difference in each of this technique. Stereolithography uses a vat of light-cured photopolymer resin and a light-sensitive laser to build successive layers. In photopolymer jetting, an ink type print-head jets light-sensitive polymer onto a platform incrementally building layers. Digital light processing builds the object upside down using liquid resin and light source on a platform.[2],[5]

In fused deposition modeling, several small beads of thermoplastic material are released from a nozzle for modeling. The materials used are thermoplastic polymers like polylactic acid (PLA), acrylonitrile butadiene styrene (ABS), polyether ether ketone (PEEK), and polycarbonate (PC), etc. Powder binder is a process that uses binding agent from an inkjet nozzle head projected onto a powder bed to construct the 3D object layer by layer. The materials used are calcium carbonate, acrylic, cyanoacrylate, ceramic powder, and liquid binder.[2],[5] Most of these techniques have revolutionized dentistry and are being used for manufacturing of craniomaxillofacial anatomical models, facial prosthesis, dental models, surgical guides, implants, crowns, and bridges [Figure 4].
Figure 4: Three dimensional printed models made using various techniques and materials

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In recent years, three-dimensional printing process has underwent tremendous improvements to make it more acceptable, reliable, and cost effective. Different 3D printing technologies, with brief note on advantages and disadvantages have been summarized [Table 1].
Table 1: Three dimensional (3D) printing technologies

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Irrespective of the process used the 3D printed models may serve as a valuable information that can be useful for the forensic expert to retrieve, analyze the evidence, and assist the court of law for conclusive jury.

a. Bite mark analysis:

Bite marks are the physical alterations within the medium caused by the forceful contact of teeth either alone or in combination with other parts of the mouth. This dental evidence, if processed properly, can help in solving a crime. Bite mark analysis facilitates identification of a suspect by comparing their dentition to the bite mark evidence.[6]

The act of biting is a dynamic procedure. In the bite mark evidences in food stuffs the consistencies of food, shrinkage, and putrefaction are the influencing factors to be taken into consideration. While in the case of a bite mark evidence on skin, healing can cause distortion and the loss of information.[7]

Traditionally, two-dimensional bite mark analysis used photographic documentation to preserve the bite marks and dental cast made from stone for recording the impression of the bite mark evidence. These have the limitation of angular distortions and dimensional inaccuracy, if proper technique is not followed.[6] Furthermore, the evidence in food stuffs needs to be collected extra cautiously due to the perishable nature of the evidence. Previous literature studies, have supported the use of 3D technologies that may overcome these limitations.[6],[7]

Once the patterned injury is established as human bite mark, with the help of 3D printing the suspect's dentition can be made and used as an evidence in court of law. Furthermore, the digitalized scans themselves can be used for 3D digital comparison of the suspect's teeth using softwares.[7] Using digital scanners to document the bite marks, eliminates any chance of distortion and also allows easy handling of the physical models that do not suffer for loss of details on handling and also allow exchange of data among judicial authorities for conclusive information of suspect's conviction. Thus, 3D scanning preserves maximum detail and seems to be a reliable, accurate, and reproducible technique.

Cheiloscopy is the study of lip patterns, various two-dimensional studies have been reported using the lipstick as a medium to collect these impressions. These traditional techniques, may cause distortion due to the variable force and can lead to loss of details.[8] 3D printed physical models may be useful in such cases. Similarly, 3D digitalization and 3D printing can be used for recording, and analyzing fingerprint, palatal rugae pattern, and footprints.[2]

b. 3D facial reconstruction:

Forensic facial reconstruction also known as facial approximation can be used to identify unknown human remains. With the advancement in 3D technology, quick, efficient, and cost effective computerized 3D forensic facial reconstruction method enables visual identification of the victim by the associated family members more definitely.[9] Computerized remodeling of missing individual can be made by using various software that also allow the data save in the standard triangulation language file (STL) formats.[2],[4],[10] These further, can be converted to the models that can be examined thoroughly. Schuh P et al. suggested the use of 3D printed skull remains from the CT scan data as a basis for forensic facial reconstruction. They also inferred that forensic radiological follow-up data improves the forensic conclusions and may support forensic expertise.[11]

c. Dental age estimation

Growth is a complex process; the skeletal system and dentition pass through a series of changes, eventually arriving at maturity. An important aspect of forensic odontology is the age determination of an individual based on dentition status.[12]

By the age of 20 years, growth and dental development are complete while the physiological changes predominate. The different methods applied for dental age assessment include the evaluation of tooth morphology, morphology of the primary and permanent dentition, the degree of skeletal ossification, and the analysis of biochemical modifications within the dental hard tissues.

Chaudhary R K et al. in their review suggested that, an accurate 3D dentition model may aid in assessing the individuals age by removing the need of direct examination in the oral cavity. They opined that 3D models would eliminate the problems faced due to improper visualization, saliva, and improper access. The same group also suggested that these 3D models of the mandible can be used for age estimation using the mandibular gonial angle.[2]

d. Gender determination:

Gender determination is a sub division of forensic odontology that is especially useful when the information relating to the deceased is unavailable. It becomes important in the case of massive disasters, chemical and nuclear explosions, natural disasters, criminal investigations, and ethnic studies.[12],[13]

Dental identification involves comparative analysis of postmortem dental profiling. The main advantage of dental evidences is that it can be preserved indefinitely after the death. This enables the analysis of antemortem and postmortem dental variables.[12]

The 3D printed model said in direct assessment and measurements of tooth sizes, shape, orientation, intercanine distances, intermolar distances, the overjet, the overbite, and arch lengths.[13] Hazeveld A et al. compared tooth sizes and observed no significant difference in the height and width of the crowns of all teeth. They concluded that the 3D-printed dental models can be clinically acceptable. It has been demonstrated that there is no dimensional change between the tooth and the 3D model.[14] An accurate printed model could improve the accuracy of sex determination procedures and for population identification from the nonmetric dental traits such as Carabelli formation.

The introduction of radiological imaging of postmortem CT scanning into the disaster victim identification (DVI) has brought additional detailed information that can be used in a variety of novel way to make physical 3D printed models. Biggs M et al. in 2019 presented a case where 3D printing was used to produce a model of a victim's dentition, enabling odontological identification without resorting to disfiguring incisions in a charred body.[15] Newcomb TL et al. in 2019 designed a 3D printed holding device known as combined holding and aiming device (CHAD) for taking postmortem radiographs. They suggested CHAD combines the benefit of being an “all-one” device because it is able to be 3D printed with its own holding and aiming mechanisms and needs no modifications or wax for use. Furthermore, CHAD can be customized to fit any single tooth in the absence of occlusion, and this device is also disposable.[16]

e. Injury pattern illustration and weapon reconstruction:

Printed 3D models may be useful to demonstrate the pattern of injury for crime scene reconstruction. It may be of special importance to present as an evidence for more detailed understanding of the crime and aid in forensic investigation.[17],[18],[19] Kettner M et al. in 2011 from Germany reported a fatal case of head injury due to hammer impact and used computer tomographic scans to create 3D printed head skull model and suggested 3D imaging allowed availability of the data sets, that can be used when the of relevant cases information is available by the forensic expert.[17] Another study by Wozniak K et al. in 2012 reported solving a case of victim with head injuries using 3 D printed model retrieved from CT scans, with 3D reconstruction of the fractured skull and suggested that this technique allowed the investigators to extract the data to develop the mechanism of injury and the probable weapon used.[18]

Forensic identification of the remains are evidences that are presented in front of judicial authorities; and traditionally it relies on photographs and data in the court involved with the storage, transportation, and presentation of human remains at the court of law.

Presenting human remains can be disturbing and also may lead to the degradation of the evidence, when handled by multiple people. 3D printed models can be a solution to solve this issue. Since, the data is in digitalized format, multiple models can be made, permanently documented, and retrieved, allowing quick and reliable digital transfer of the data across the judicial authorities for conclusive results. Furthermore, this method provides an excellent replication of three-dimensional injuries and anatomical structures consistent with legal and ethical issues also, respecting the dignity of the deceased and emotions of the family members.[19]

Examples of Current Application of Three-Dimensional Printing in Forensic Odontology[20]:

In order to better understand the crime scene and to present cases in court, the Hong Kong Police Briefing Support Unit uses its own 3D printers to recreate crime scenes and suggested the use of 3D printers for quick and accurate investigation.

In 2013, the Japanese police gathered thousands of case-related clues from local citizens, using a 3D printed model of a crime scene. A case of a 6-yearold girl was solved by forensic experts wherein 3D printed skull models from Computed tomography (CT) scans of her remains supported homicide prosecution of her parents by presenting detailed replicas of the victims injured skull.

In 2015, England police used a combination of 3D scanning and printing to obtain a conviction of Lorenzo Simon who was accused of murdering his tenant, Michael Spalding. The murderer separated the whole body with a saw, partially burnt, and disposed them within a suitcase. Using this 3D technology, the West Midlands Police with the help of Warwick's University identified the bone found in the suspect's backyard was a matching piece of fractured bone found in the suitcases.

In 2016, skeletal remains were found at Ohio, USA. The Greene County officer with the help of Ohio State University produced 3D models of the remains to aid in the identification process. After CT scanning and making a 3D printed model of the victim's skull, the model was fleshed out with clay, i.e., facial reconstruction. Finally, photographs of the 3D-printed model were circulated within the public of Ohio State, which quickly led to the identification of the victim.

Chase RJ et al. in 2018 in their review reported the value of forensic imaging and 3D printing as demonstrative aid in court of law while also highlighting the need for evidence- based data to support such tools. Furthermore, they also presented few of the National Institute of Justice projects wherein 3D printing is under research for its possible applications in forensics.[21]

Johnson A et al. in 2019 conducted any experimental study using an innovative digital approach of Forensic tooth reconstruction (FTR) using three-dimensional (3D) printed tooth retrieved from intra-alveolar morphology of empty dental sockets. They concluded that this technique proved to be accurate and showed minimal discrepancy.[22]

Limitations

These newer technologies have to be sufficiently explored to make them into a main stream evidence to be presented for cross-examination in court of law, an empirical evidence-base needs to be formed to underpin the reliability and reproducibility of 3D printing. Furthermore, there is limited information on 3D printer capabilities for printing forensic case specimens exhibiting trauma and fine details as most of the finished models show striations when the material was added in layers during manufacturing process.[21] This is even more crucial when using 3D techniques for demonstration of impact evidence. The issues surrounding the validity and reliability of printed replicas and their evidential value must be evaluated and addressed, to avoid risk of misleading evidence.

The need for technically trained personal with a keen knowledge on the available printing technologies and applied skill in practice of 3D printing is a major requisite. Another concern is the cost of the equipment, maintenance, and adherence to strict health and safety protocols.


   Conclusion Top


The technology of 3D printing may open new doors in forensic odontology. Though, the applications in this domain are in the stage of infancy, it definitely has a promising future. 3D-printed models assist the forensic expert, in the examination and identification of the suspect. The non invasive nature of this technique allows us to get maximum anatomic details in minimal time. It allows construction of the complex facial structures, that can be used to solve crime and also enables the experts to demonstrate the evidence in a presentable form to a non medical personal in the court of law for more clarity of the details. With the increasing popularity of these techniques in various fields, it is now easily available and relatively cost-effective. This form of digital forensics may revolutionize the field of forensic odontology in the near future.

Acknowledgement

The authors would like to thank Dr. Aditya Mohan Alwala, CEO, Am3D printing technologies private limited for the image acquisition and Mr. Kiran Soni, CEO, Evnzee technologies private limited for their expertise and assistance with the 3D printing.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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