Peter J. Bush

Enamel Demineralization in Primary and Permanent Teeth

Although enamel demineralization is important for our understanding of caries formation, no consensus has been reached regarding the possible differences in susceptibility of primary and permanent enamel. We used the constant composition (CC) technique to investigate the acid-induced demineralization of these tissues at a relative undersaturation with respect to hydroxyapatite (HAP) of 0.902, pH = 4.5, and ionic strength = 0.15 mol L−1. The demineralization rates showed significant differences, primary enamel having the greater susceptibility to dissolution during an initial linear stage: 1.5 ± 0.5 x 10−10 mol mm−2 min−1 compared with 2.6 ± 0.5 x 10−11 mol mm−2 min−1 for permanent enamel. During the reactions, we observed nanosized crystallites which attached to the enamel surfaces or escaped into the bulk solution. These nanosized crystallites were kinetically protected against further dissolution, even though the solutions remained undersaturated. It is hypothesized that they may contribute to the remarkable mechanical and dynamic characteristics of enamel.

Biomechanical factors in human dermal bitemarks in a cadaver model.

Abstract:  In bitemark analysis, the forensic odontologist must consider how the biomechanical properties of the skin contribute to distortion of the bitemark. In addition, one must consider how the bitemark can be distorted by postural movement of the victim after the bite has occurred. A fundamental review of the architecture and biomechanical properties of the dermis is described and evaluated through bites made on cadavers. In order to assess distortion, 23 bites from a single characterized dentition were made on un‐embalmed cadaver skin. Bite indentations were photographed. Following various body manipulations they were re‐photographed in different positions. Hollow volume overlays of the biting dentition were constructed, and metric analysis of the dentition and all bitemarks was completed. The overall intercanine, mesial to distal, and angle of rotation distortion was calculated. Of the 23 bites made, none were measurably identical, and in some cases, dramatic distortion was noted.

Detection and classification of composite resins in incinerated teeth for forensic purposes.

ABSTRACT: The great demand for esthetic restorations has resulted in placement of large numbers of composite resin fillings. The popularity of these materials is reflected in the quantity and variety of resin brands currently on the market. The ability to distinguish resin brands can aid in positive identification of burn victims, assuming that appropriate dental records exist. Scanning electron microscopy/energy dispersive X‐ray spectroscopy (SEM/EDS) was used to characterize the structure and composition of 10 modern resins. The structure of each resin was unique to manufacturer, and elemental analysis allowed separation into distinct groups. These 10 resins were also placed in extracted teeth and incinerated at 900°C for 30 min, simulating near cremation conditions. The resins were identifiable by SEM/EDS after incineration, and the elemental composition remained almost unchanged. The data produced are immediately useful for resin identification in forensics, and comparative analysis can be readily performed using standard equipment. This work represents the initial stage of database generation.

Identification Through X‐Ray Fluorescence Analysis of Dental Restorative Resin Materials: A Comprehensive Study of Noncremated, Cremated, and Processed‐Cremated Individuals*

ABSTRACT: Tooth‐colored restorative materials are increasingly being placed in the practice of modern dentistry, replacing traditional materials such as amalgam. Many restorative resins have distinct elemental compositions that allow identification of brand. Not only are resins classifiable by elemental content, but they also survive extreme conditions such as cremation. This is of significance to the forensic odontologist because resin uniqueness adds another level of certainty in victim identification, especially when traditional means are exhausted. In this three‐part study, unique combinations of resins were placed in six human cadavers (total 70 restorations). Simulated ante‐mortem dental records were created. In a blind experiment, a portable X‐ray fluorescence (XRF) unit was used to locate and identify the resin brands placed in the dentition. The technique was successful in location and brand identification of 53 of the restorations, which was sufficient to enable positive victim identification among the study group. This part of the experiment demonstrated the utility of portable XRF in detection and analysis of restorative materials for victim identification in field or morgue settings. Identification of individuals after cremation is a more difficult task, as the dentition is altered by shrinkage and fragmentation, and may not be comparable with a dental chart. Identification of processed cremains is a much greater challenge, as comminution obliterates all structural relationships. Under both circumstances, it is the nonbiological artifacts that aid in identification. Restorative resin fillings can survive these conditions, and can still be named by brand utilizing elemental analysis. In a continuation of the study, the cadavers were cremated in a cremation retort under standard mortuary conditions. XRF was again used to analyze retrieved resins and to identify the individuals based on restorative materials known to exist from dental records. The cremains were then processed and the analysis was repeated to determine whether restorative resins could be found under this extreme condition. Under both circumstances, sufficient surviving resin material was found to distinguish positively each individual in the study group. This study showed the utility of XRF as an analytical tool for forensic odontology and also the significance of the role of restorative resins in victim identification, even after cremation.

Laser patterning and critical current measurements of submicrometer lines of Y-Ba-Cu-O

Superconducting strips of 0.6 μm width were fabricated by direct laser writing on mirror‐like Y‐Ba‐Cu‐O thin films on various substrates. These films were grown by laser deposition without post‐annealing. Laser ablation etching had no effect on the Tc and Jc until the lines were <1 μm wide. The 0.6‐μm‐wide strip showed some degradation of Tc. The critical current densities for all patterned lines were measured to be ∼4×106 A/cm2 at 20 ° K.

Analytical Survey of Restorative Resins by SEM/EDS and XRF: Databases for Forensic Purposes

Abstract:  Frequently in forensic cases, unknown substances must be identified. Automated databases can ease the burden of comparison as materials may be compared against many known standards in a relatively short period of time. It has been shown that dental resins can be named according to brand or brand group even in conditions as harsh as cremation. Databases are already in use for many materials, but no such database exists for dental resins. Thus, two databases were generated. One utilized a laboratory‐based method, scanning electron microscopy with energy dispersive X‐ray spectroscopy (SEM/EDS), in conjunction with the Spectral Library Identification and Classification Explorer (SLICE) software. The other was based on portable X‐ray fluorescence (XRF). The ability to perform database comparison with portable instrumentation can thus be brought directly to the field. Both the SLICE and XRF databases were evaluated by testing unknown resins. EDS is a well‐established technique and the SLICE program was demonstrated to be a good tool for unknown resin identification. Portable XRF is a relatively new instrument in this regard and its databases have been constructed mostly for metal alloy comparison and environmental soil testing. However, by creation of a custom spectral library, it was possible to distinguish resin brand and bone and tooth from other substances.

Uniqueness of the Dentition as Impressed in Human Skin: A Cadaver Model*

Abstract:  Bitemark interpretation assumes that the human dentition is unique and that its attributes can be accurately transferred to skin. A cadaver model was used to investigate whether the correct biter could be determined from similarly aligned dentitions once the dentitions were impressed in human skin. One‐hundred dental stone models, which were measured and determined to be unique, were divided into 10 groups based upon similarities of mal‐alignment patterns. One model was randomly selected from each group and bites were produced on unembalmed human cadavers. Metric/angular measurements and hollow volume overlays of the models were compared with the bites made. The percentage of dentitions from each group as well as the 100 dental model population that could not be excluded as the biter was determined. Results showed difficulty distinguishing the biter from individuals with similarly aligned dentitions and in some cases, an incorrect biter appeared better correlated to the bite.

The response of skin to applied stress: investigation of bitemark distortion in a cadaver model.

Abstract:  Knowledge of distortional properties of skin is important in bitemark analysis. Thus, the response of skin to stress from bites was investigated. Four sets of models were created from the dentition of one individual. Anterior teeth were systematically removed to vary contact surface area. A biting apparatus was constructed with an integrated load cell. Forty‐six bites were created perpendicular to Langer lines on six cadavers. Rate of force application and bite pressure were controlled. Metric/angular measurement and hollow volume overlays were employed. Distortion produced by each dentition was calculated and assessed. Results showed that as teeth impressed loose tissue, mesial/distal distance increased, angles of rotation flattened, and inter‐canine distance lengthened. An opposite effect was seen in tight tissue. When the surface area of the dentition was reduced, a mixture of these effects was observed. Conclusions indicated that stiffness of the tissue was the most important variable in bitemark distortion.

Ultraviolet Illumination as an Adjunctive Aid in Dental Inspection

Abstract:  Tooth‐colored resin fillings have become increasingly popular as restorative materials. Their presence in the dentition presents a challenge to the clinician and the forensic odontologist, as detection of the fillings can be difficult both visually and radiographically. As they necessarily form part of the unique dentition of an individual, recognition of the resins is important for forensic identification. Alternative light sources have been used with success in various fields of forensic science. In recent years small LED flashlights emitting at specific wavelengths in the ultraviolet light (UV) range have been developed. Their low cost, small size, and ready availability makes their use practical in both forensic dental inspection and clinical settings. UV inspection is of interest because enamel, dentin and dental materials all have differing fluorescent properties when illuminated by UV light. It was one goal of this research to quantitatively assess the fluorescence properties of modern restorative resins in order to predict their behavior during inspection using UV illumination. The second goal was to demonstrate practical use of UV in dental inspection with examples of how different materials fluoresce. Quantitative measurements were obtained for optical emission wavelength and intensity for 15 modern resins using a spectrophotometer. Results indicated that resin brands fluoresce at different wavelengths and with varying intensities. Practical use and comparison of the flashlights revealed that the most useful excitation wavelengths for resin detection were in the UVA range (365 and 380 nm). Porcelain restorations and composite resin fillings exhibited different responses to these two wavelengths and thus use of both is recommended for forensic dental inspection.

Identification of Incinerated Root Canal Filling Materials After Exposure to High Heat Incineration

Abstract:  With the increase in global terrorism there is a higher probability of having to identify victims of incineration events secondary to incendiary explosive devices. The victims of incineration events challenge forensic odontologists when coronal restorations are no longer present to compile postmortem data. With 40 million root canals being completed annually in the United States, a very large pool of antemortem data is available to the forensic odontologist to make positive identifications. When complete and thorough dental records exist, individuals that have undergone surgical and nonsurgical root canal therapy may have materials present in the canal that may aid in identification. This study provides elemental fingerprints of root canal obturation materials to be utilized as a forensic identification aid. This study used scanning electron microscopy/energy dispersive X‐ray spectroscopy (SEM/EDS) to assess the elemental composition of materials before and after high temperature incineration. Sixteen endodontic materials were analyzed pre‐incineration and placed in extracted teeth. The filled teeth were subjected to incineration at 900°C for 30 min to simulate incineration events or cremation. Incinerated materials were radiographed and re‐analyzed to determine if they retained their original elemental composition. Endodontic sealers, gutta percha, root‐end filling materials, silver points, and separated files were distinguishable in the canal and traceable after incineration. The authors present a fingerprint of the endodontic obturation materials that are capable of withstanding high heat incineration to be used as an aid for postmortem identification. This work represents the initial stage of database generation for root canal filling materials for use as an aid in forensic identification.