The objective of this study was to utilize three-dimensional (3D) semi-landmarks & geometric morphometrics (GM) to quantify shape variation in the maxillo-mandibular complex of mice on prolonged diets of equivalent nutrition but different consistency. Forty three wild type mice (22 males; 21 females) were divided into two groups. For 15 generations, the control group (6 males; 6 females) was fed a standard hard pellet diet, whereas the experimental group (6 males; 6 females) was fed a soft powder diet of the same nutritional value. After the 15th generation, 19 more mice were added to the sample group but were placed in opposing sample categories (soft vs. hard). Mouse heads were collected at 6-weeks of age and fixed in 4% paraformaldehyde for 48h. Specimens were scanned using Skyscan 1076 MicroCT scanner at 18-micron resolution (55 kV, 150 mA, 0.5 mm Al filter) & reconstructed as series of 8-bit grayscale images. Segmentation & surface generation from microCT data was performed. Seventy landmarks were placed to measure 3D changes and subsequently analyzed by GM to determine shape variation.
Subtle morphological changes were noted in the skull, mandible, and temporomandibular joint (TMJ) using principle components analysis (PCA) and canonical variates analysis (CVA). For example, soft diet mice possessed shorter mandibular body lengths and wider condylar necks. In addition, sexual dimorphic differences were observed in the TMJ.
Thus, we demonstrated the impact of changing diet consistency over multiple generations on the morphology of the mouse maxillo-mandibular complex using 3D GM analysis.