Forensic identification may take place prior to death and is referred to as Antemortem (AM) identification. Identification may as well be transported after death and is called Postmortem (PM) identification. While behavioral characteristics (eg speech) are not suitable for PM identification, most of the physiological characteristics are not appropriate for PM identification as well, especially under severe circumstances encountered in mass disasters (eg aircraft crashes) or when identification is being attempted more than a few weeks after death.
Therefore, a postmortem biometric identifier has to survive such severe conditions and resist early decay that affects body tissues.Dental features are considered the best candidates for PM identification. This is due to their survivability and diversity. Forensic odontology is the branch of forensics concerned with identifying human individuals based on their dental features. Traditionally, forensic odontologists relied on the morphology of dental restorations (fillings, crowns, etc.) to identify victims. However, modern materials used in restorations and fills have poor radiographic characteristics. Here, it is becoming important to make identification decisions based on inherent dental features like root and crown morphologies, teeth size, rotations, spacing between teeth and sinus patterns.
ADIS will provide automated search and matching capabilities for digitized x-ray and photographic images. This paper deals about an overview of ADIS (Automated Dental Identification System) and also presents a new fully automated algorithm for identifying people from dental X-ray images. ADIS (Automated Dental Identification System) is a fully automated system, which is built for PM identification. Dental biometrics automatically analyzes dental radiographs to achieve the aim of forensic dentistry. It is to identify the disabled individuals for what other means of identification (eg, fingerprint, face, etc.) are not available. Dental radiographs provide valid, accurate and reliable information about the identity of an individual.
On the basis of the time of acquisition, there are two classes of dental radiographs. The radiographs acquired after the death are called the Post-mortem (PM) radiographs, and the radiographs acquired while the person is alive are called the Ante-mortem (AM) radiographs. The AM radiographs, grouped in the dentists 'office, are labeled with patients' names. The method used in dental biometrics is matching the unlabeled PM radiographs against the database of labeled AM radiographs. If the set of teeth in a PM radiograph adequately matches the teeth in an AM radiograph, the identity of the PM radiograph is obtained In order to achieve the ADIS, the automated archiving of AM (antemortem) dental images in a database, are for searched the database for the best matches to a given PM image. To achieve this goal, we need to automate the process of segmenting the dental radiographs. There are two stages for dental biometrics:
1. Radiograph Segmentation and Teeth Separation
2. Shape matching
3. Limitations of Existing Architecture:
There are many challenges that affect the performance of ADIS and should be taken into account while building the system. These challenges include dealing with i) The main challenge is that dental features may change over time, especially if the PM images were captured long time after the AM were captured, that will lead to difficulty in matching.
ii) Poor quality radiographs, which adversely affect the segmentation results, and consequentially affects the accuracy of ADIS.
iii) A third challenge is handling view variance in both AM and PM image.
If the PM images were captured long time after the AM were captured, that would lead to difficulty in matching. Morphology of root can be used for identification in this case. A reversible technique is presented which uses the root morphology.
Teeth are comprised of a crown and one or more roots. The crown may have a 'chisel-like' edge or one or more points called 'cusps'. Enamel formation is called amelogenesis and occurs in the crown stage of tooth development. Dentin formation, known as dentinogenesis, is the first identifiable feature in the crown stage of tooth development. The formation of dentin must always occur before the formation of enamel.
As root and cementum formation begin, bone is created in the adjacent area. Frequently, nerves and blood vessels run parallel to each other in the body, and the formation of both usually takes place simultaneously and in a similar fashion. However, this is not the case for nerves and blood vessels around the tooth, because of different rates of development
Cementum formation is called cementogenesis and occurs late in the development of teeth. Cementoblasts are the cells responsible for cementogenesis.
In this technique, missing teeth in skeletonized human remains can be reconstructed for the purpose of radiographic comparison and postmortem identification. In this technique, which is based upon pilot studies with skeletonized mandibles of archival remains, the alveolar socket walls are sealed with a coat of cyanoacrylate cement and injected with a mixture of vinyl polysiloxane and barium sulfate. Radiographs are produced with the radiopaque mixture in place, which highlights the antemortem morphology of the roots. Subsequently, the impression material is removed, resulting in no gross alteration of the evidence. The radiographs made with this technique, as well as the impressions, can be stored for later use at a trial or pending the discovery of ante mortem dental evidence.
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Source by Devi Padmini