A geometric morphometric approach to the study of variation of shovel‐shaped incisors
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Date
Authors
Carayon, Delphine
Adhikari, Kaustubh
Monsarrat, Paul
Dumoncel, Jean
Braga, Jose
Duployer, Benjamin
Delgado, Miguel
Fuentes-Guajardo, Macarena
De Beer, Frikkie
Hoffman, Jakobus W.
Journal Title
Journal ISSN
Volume Title
Publisher
Wiley
Abstract
OBJECTIVES : The scoring and analysis of dental nonmetric traits are predominantly accomplished by using the Arizona State University Dental Anthropology System (ASUDAS), a standard protocol based on strict definitions and three‐dimensional dental plaques. However, visual scoring, even when controlled by strict definitions of features, visual reference, and the experience of the observer, includes an unavoidable part of subjectivity. In this methodological contribution, we propose a new quantitative geometric morphometric approach to quickly and efficiently assess the variation of shoveling in modern human maxillary central incisors (UI1).
MATERIALS AND METHODS : We analyzed 87 modern human UI1s by means of virtual imaging and the ASU‐UI1 dental plaque grades using geometric morphometrics by placing semilandmarks on the labial crown aspect. The modern human sample was composed of individuals from Europe, Africa, and Asia and included representatives of all seven grades defined by the ASUDAS method.
RESULTS : Our results highlighted some limitations in the use of the current UI1 ASUDAS plaque, indicating that it did not necessarily represent an objective gradient of expression of a nonmetric tooth feature. Rating of shoveling tended to be more prone to intra‐ and interobserver bias for the highest grades. In addition, our analyses suggest that the observers were strongly influenced by the depth of the lingual crown aspect when assessing the shoveling.
DISCUSSION : In this context, our results provide a reliable and reproducible framework reinforced by statistical results supporting the fact that open scale numerical measurements can complement the ASUDAS method.
Description
Supplementary material: Table S1 Supporting Information Table 1. Visual scoring performed by two independent observers (intra‐ and interobserver tests). SSc: Statistical Scoring; VS1T1: Visual scoring Observer 1 Test 1; VS1T2: Visual scoring Observer 1 Test 2; VS2: Visual scoring Observer 2. In some cases, the observers gave an intermediate rating (0_1 meaning a category between ASUDAS references 0 & 1).
Table S2: Supporting Information Table 2. Definition of UI1 shoveling grades (Scott et al., 2018; Scott & Irish, 2017; Turner et al., 1991).
Table S3: Supporting Information Table 3. Correlations between various measurements obtained from the coordinates of the 7 ASUDAS reference casts. The ASUDAS category values were also compared against these metrics.
Table S4: Supporting Information Table 4. Correlations between various measurements obtained from the coordinates of all French samples (both contemporary and medieval). Maximum depth and hollow area are the directly measured metrics based on the non‐Procrustes alignment method. Principal components were obtained from both Procrustes and non‐Procrustes methods. Only PC1 is presented here for simplicity. Shades of color represent the degree of correlation, with darker green corresponding to the highest degrees and white to the lowest degree.
Table S5: Supporting Information Table 5. Correlations of rater‐assigned ASUDAS categories with various measurements obtained from the coordinates of all French samples.
Figure S1 Supporting Information Figure 1. Principal Component loadings represented as PC shape changes. Results are shown here for non‐Procrustes PCs; the plots for Procrustes PCs are very similar. The axes are same as in Figure 2. The black line, showing the shape for ASUDAS reference cast category 3, indicates the baseline in all figures. The thick colored curve in each figure represents a + 1 unit shift toward the direction of the PC from the baseline. Thin dotted lines join the coordinate of each of the 100 points before and after the shift, thus representing the amount and direction of shift for each point.
Keywords
ASUDAS, Virtual anthropology, Shovel‐shape incisors, Procrustes superimposition, Non‐Procrustes superimposition
Sustainable Development Goals
Citation
Carayon D, Adhikari K, Monsarrat P,
et al. A geometric morphometric approach to the study of variation of shovel-shaped incisors. American Journal of Physical Anthropology 2019;
168:229–241. doi: 10.1002/ajpa.23709.