Objectives: To assess the reliability of variable measurement for the objective phenotyping of Wild type CD-1 mice; a model for dental anomalies, using Image Analysis techniques (IA). This methodology will then be applied to provide genotype-phenotype relationships of X-linked Amelogenesis imperfecta (X-AI) using Amelx mutant mice.
Methods: A control population of 20 left and right hemi-mandibles and mandibular incisors were extracted from 20 CD-1 Wild-Type mice at ≤ 22 weeks old at age of death. Calibrated images were captured using established IA consisting of a 13.5 mega-pixel Kodak/ Canon DCS/n SLR digital camera mounted on a Kaiser photographic stand. Standardised conditions of illumination, orientation and magnification were used to obtain images from both buccal and lingual aspects of the hemi-mandibles and lower incisors. Repeat images and measurements were taken after a minimum interval of 1 week and 24 hours respectively, by 2 independent operators. Eight quantitative variables of size, shape curvature and bulk were defined for mandibles, (1) overall-length; (2) ascending-height; (3) basal-length; (4) mandible-angle; (5) coronoid-coronoid; (6) diagonal-length; (7) mandible-area; (8) mandible-perimeter, and incisors, (L) overall-length; (An) angle-of-curvature; (W) width-at-midpoint; (P) incisor-perimeter and (Ar) incisor-area, using Image Pro Plus 5.1 software.
Results: Intra-Class Correlation Coefficients (ICCC) for intra-operator repeatability's ≥0.79 and inter-operator reproducibility's ≥0.77 represented good reliability for all variables (Tables 1 & 2).
Conclusions: The study validated the IA for measurement of murine mandibles and incisors with good operator reliability. The variables chosen proved practical, providing additional information towards the understanding of the X-AI aetiology.
Table 1. Intra And Inter-Operator Repeatability For Mandible Measurement.
| INTRA-Operator 1 | |||||||||||||||
Aspect | Buccal | Lingual | ||||||||||||||
Variable | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 7 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 |
Left | 0.92 | 0.98 | 0.84 | 0.94 | 0.88 | 0.85 | 0.81 | 0.81 | 0.99 | 0.98 | 0.94 | 0.99 | 0.95 | 0.87 | 0.98 | 0.99 |
Right | 0.99 | 0.82 | 0.92 | 0.98 | 0.96 | 0.79 | 0.89 | 0.91 | 0.84 | 0.86 | 0.80 | 0.98 | 0.95 | 0.86 | 0.90 | 0.87 |
| INTER-Operator | |||||||||||||||
Left Right | 0.98 | 0.95 | 0.92 | 0.97 | 0.86 | 0.91 | 0.97 | 0.99 | 0.98 | 0.96 | 0.93 | 0.97 | 0.83 | 0.82 | 0.90 | 0.99 |
0.89 | 0.83 | 0.95 | 0.98 | 0.84 | 0.85 | 0.83 | 0.91 | 0.90 | 0.83 | 0.87 | 0.97 | 0.88 | 0.84 | 0.84 | 0.86 | |
Table 2. Intra And Inter-Operator Repeatability For Murine Incisor Measurement
| INTRA-Operator 1 | |||||||||
Aspect | Buccal | Lingual | ||||||||
Variable | L | An | W | P | Ar | L | An | W | P | Ar |
Left | 0.91 | 0.96 | 0.99 | 0.92 | 0.83 | 0.95 | 0.96 | 0.99 | 0.97 | 0.92 |
Right | 0.89 | 0.83 | 0.99 | 0.93 | 0.88 | 0.94 | 0.83 | 0.99 | 0.97 | 0.91 |
INTER-Operator | ||||||||||
Left | 0.85 | 0.91 | 0.99 | 0.91 | 0.82 | 0.81 | 0.93 | 0.99 | 0.95 | 0.89 |
Right | 0.90 | 0.77 | 0.99 | 0.93 | 0.86 | 0.82 | 0.82 | 0.99 | 0.96 | 0.91 |