Geometeric morphometric assessment of mandibular shape in 6.0-8.0 Year Olds

Authors

Tiffany Tran, University of the Pacific
HeeSoo Oh, University of the Pacific
Gary D. Richards, University of the Pacific

Lead Author Affiliation

Dental Surgery Program

Introduction/Context/Diagnosis

We employ geometric morphometrics methods to explore three-dimensional data in an effort to delineate idiosyncratic and progressive growth variation in 6.0-8.0 year old mandibles.

Methods/Treatment Plan

We used a Microscribe digitizer to collect 39 three-dimensional landmarks from 45 mandibles (Institute for Craniofacial Study, UOP). To assess developmental age we; CT scanned the mandibles, visualized teeth as isosurfaces/volume renderings, and assigned ages based on the tooth calcification sequence of Schour and Massler. Age groups were constrained to ages 6.0-8.0 years. 3D coordinate data were analyzed with Morphologika. Shape was explored using Principle Components Analysis on Procrustes-aligned shape variables.

Results/Outcome

Principle components (PC) 1-2 explain 18.5 and 12.0% of the variance, respectively. PC2-PC3 explain a further 9.6 and 8.0% of the variance, respectively. PC1 drifts to more positive scores between ages 6.0-6.5 years, but stabilizes after 7.0 years. This PC indicates that the corpus-to-ramus angular relationship is becoming more obtuse in ages 6-7.0 years. The dimensions comprising PC1 are stable between groups but idiosyncratic variation increases in ages 7-8.0 years. PC2 scores indicate little growth between groups but significant change in the range of idiosyncratic variation related to corpus width. PC3 shows substantial laterally-directed growth of the coronoid process region and a concomitant anterior progression of the chin related to idiosyncratic variation but little in the way of progressive age differences.

Significance/Conclusions

Geometric morphometric methods allows visualization of the range of idiosyncratic variation in specific age groups but also the type and degree of shape change between minor increments of age.

Comments/Acknowledgements

This work was presented at the 95th General Session International Association for Dental Research, San Francisco, CA March 22-25, 2017.

Location

University of the Pacific, Dugoni Dental School, San Francisco, CA

Format

Poster

Poster Session

1st and 2nd Year Student Research Presentations