Dyke Alice Elizabeth Catherine, Cunningham Susan, Hunt Nigel, Ruff Clifford
Eastman Dental Hospital,256 Grays Inn Road, London, WC1X8LD, England.
Eastman Dental Institute,256 Grays Inn Road, London, WC1X8LD, England.
Forensic Sci Int. 2018 Aug;289:368-373. doi: 10.1016/j.forsciint.2018.06.008. Epub 2018 Jun 26.
The human dentition contains many features which can be used to identify an individual from the dentition or from bite marks created and bite mark evidence may be used to link a suspect to a crime. The aim of this research was to investigate the effect of orthodontic treatment on the uniqueness of the human anterior dentition by comparison of the number of dental shape matches between pre- and post-treatment dental casts for a group of patients who have undergone orthodontic treatment (dental braces) to improve the alignment of their teeth.
This comparative study utilised pre- and post-orthodontic treatment dental casts from 36 patients. The dental casts were scanned and the anterior 6 teeth landmarked with 24 landmarks in total. The dental casts were divided into 4 groups: pre-orthodontic upper jaw (maxillary) and lower jaw (mandibular) and post-orthodontic maxillary and mandibular. Partial and full Procrustes analyses were undertaken to investigate the similarity between dental casts within each group and whether any of the comparisons were similar enough to be classified as a match. A landmarking repeatability study performed on a set of digitised dental casts determined the error of the landmarking procedure and allowed a proposed match threshold to be established.
Orthodontic treatment reduced the uniqueness, and increased the similarity, between dentitions, as evidenced by a reduction in the maximum partial Procrustes distances in the post-orthodontic dental cast groups. None of the dental cast comparisons in the pre- or post-orthodontic maxillary or mandibular groups were classified as a match with the partial Procrustes analysis. However, many false positive matches (between 35 and 61) were identified within the post-orthodontic maxillary and mandibular groups using the full Procrustes analysis.
Orthodontic treatment reduced the uniqueness of the human anterior dentition between different patients. There were no matches identified with the partial Procrustes analysis, but a large number of false positive matches were identified using the full Procrustes analysis. It is therefore proposed that full Procrustes analysis is unsuitable for this type of work and that only partial Procrustes analysis should be utilised.
人类牙列具有许多可用于从牙列或咬痕中识别个体的特征，咬痕证据可用于将嫌疑人与犯罪联系起来。本研究的目的是通过比较一组接受正畸治疗（戴牙套）以改善牙齿排列的患者治疗前和治疗后牙模之间牙齿形状匹配的数量，来研究正畸治疗对人类前牙列独特性的影响。
这项比较研究使用了36名患者正畸治疗前和治疗后的牙模。对牙模进行扫描，并在前6颗牙齿上总共标记24个地标点。牙模分为4组：正畸治疗前的上颌和下颌，以及正畸治疗后的上颌和下颌。进行了部分和完全普氏分析，以研究每组牙模之间的相似性，以及是否有任何比较相似到足以被归类为匹配。对一组数字化牙模进行的地标点重复性研究确定了地标点程序的误差，并允许建立一个提议的匹配阈值。
正畸治疗降低了牙列之间的独特性，并增加了相似性，正畸治疗后牙模组中最大部分普氏距离的减少证明了这一点。正畸治疗前或治疗后的上颌或下颌组中，没有牙模比较被部分普氏分析归类为匹配。然而，使用完全普氏分析在正畸治疗后的上颌和下颌组中发现了许多假阳性匹配（35至61个）。
正畸治疗降低了不同患者之间人类前牙列 的独特性。部分普氏分析未发现匹配，但使用完全普氏分析发现了大量假阳性匹配。因此，建议完全普氏分析不适用于此类工作，仅应使用部分普氏分析。
