8 - A facial maturation index based on cranium-to-face ratio as a predictor of skeletal maturity

Background

Diagnostic methods to determine individual skeletal maturity have been reported to indicate treatment timing in orthodontics.

Objective

To evaluate the changes in cranium/face size ratio (Facial Maturation Index - FMI) between the skeletal maturity stages defined by cervical vertebral maturation (CVM).

Methods

The sample consisted of a set of lateral cephalograms selected from the records of 180 subjects from the Burlington Growth Center and the Forsyth Institute. For each lateral cephalogram, the face area (FA) and neurocranium area (NCA) were delimited and measured. The FMI was calculated by FA/NCA. The FMI was compared and correlated with the CVM stages using ANOVA and Spearman's correlation tests. ROC analysis evaluated the FMI diagnostic performance.

Results

The NCA was similar between all maturation stages. FA and FMI increased significantly with each advance in CVM stages. The female sample tended to have a lower facial growth rate and earlier facial growth acceleration, while males tended to have a longer growth spurt period. There was significant and positive correlation between FMI and CVM stages for female (0.768) and male (0.803) samples. Areas under ROC curves for FMI were 0.851 to female and 0.854 to male sample, showing good diagnostic performance of FMI for discriminating pre-peak maturation stage from peak and post-peak stages.

Conclusion

Changes in cranium-to-face ratio were strongly correlated with CVM maturation stages. The diagnostic performance of FMI shows that it is a clinically useful diagnostic aid for predicting facial growth.